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Ahsanul Haque, Daka, BD Geelong, AU Ilda Kazani, Tirana, AL Svjetlana Janjic, Banja Luka, BA Igor Jordanov, Skopje, MK Petra Komarkova, Liberec, CZ Mirjana Kostic, Beograd, RS Manja Kurecic, Maribor, SI Rimvydas Milasius, Kaunas, LT Olga Paraska, Khmelnytskyi, UA Irena Petrinic, Maribor, SIŽeljko Penava, Zagreb, HR Tanja Pušic, Zagreb, HR Zenun Skenderi, Zagreb, HR Snežana Stankovic, Beograd, RS Jovan Stepanovic, Leskovac, RS Zoran Stjepanovic, Maribor, SI Simona Strnad, Maribor, SI Jani Toroš, Ljubljana, SI Mariana Ursache, Iai, RO Antoneta Tomljenovic, Zagreb, HR Dušan Trajkovic, Leskovac, RS Hidekazu Yasunaga, Kyoto, JP (ISSN: 0351-3386 tiskano, 2350-3696 elektronsko) je znanstvena revija, ki podaja temeljne in aplikativne znanstvene informacije v fizikalni, kemijski in tehnološki znanosti, vezani na tekstilno in oblacilno tehnologijo, oblikovanje in trženje tekstilij in oblacil. V prilogah so v slovenskem jeziku objavljeni strokovni clanki in prispevki o novostih v tekstilni tehnologiji iz Slovenije in sveta, prispevki s podrocja oblikovanja tekstilij in oblacil, informacije o raziskovalnih projektih ipd. (ISSN: 0351-3386 printed, 2350-3696 online) the scientific journal gives fundamental and applied scientific information in the physical, chemical and engineering sciences related to the textile and clothing industry, design and marketing. 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VOLUME 64 • TEKSTILEC 4 2021 ISSN 0351-3386 (tiskano/printed) UDK 677 + 687 (05) SCIENTIFIC ARTICLES/ Znanstveni clanki 276 Elise Diestelhorst, Jan Lukas Storck, Bennet Brockhagen, Timo Grothe, Inken Blanca Post, Thorsten Bache, Rumen Korchev, Anke Rattenholl, Frank Gudermann, Andrea Ehrmann Necessary Parameters of Vertically Mounted Textile Substrates for Successful Cultivation of Cress for Low-Budget Vertical Farming Lastnosti vertikalno namešcenih tekstilij, potrebne za uspešno gojenje kreše pri nizkocenovnem vertikalnem kmetovanju 286 Aleksandra Micic, Ivanka Ristic, Suzana Djordjevic, Nebojsa Ristic, Dragan Djordjevic Adsorbent from Textile Waste for Removal of Textile Reactive Dye from Water – Equilibrium Adsorption and Kinetics Adsorbent iz tekstilnih odpadkov za odstranjevanje tekstilnega reaktivnega barvila iz vode –adsorpcijsko ravnotežje in kinetika 298 Ilda Kazani, Majlinda Hylli, Pellumb Berberi Electrical Resistivity of Conductive Leather and Influence of Air Temperature and Humidity Elektricna upornost prevodnega usnja ter vpliv temperature in vlažnosti zraka 305 Malek Alshukur Effect of Spinning Triangle and Production Speed of Hollow-Spindle System on the Bouclé Yarn Structure Vpliv predilnega trikotnika in proizvodne hitrosti sistema z votlim vretenom na strukturo preje buklé 317 Tetiana Ielina, Liudmyla Halavska, Nataliia Ausheva Macro-Modelling of Rib-Knitted Tubular Parts Makromodeliranje rebrasto pletenih cevastih sestavnih delov 325 Sibel Kaplan, Betül Akgünoglu Transfer and Friction Characteristics of Sports Socks Fabrics Made of Synthetic Fibres in Different Structures Prenos tekocin in torne lastnosti sinteticnih pletiv za športne nogavice v razlicnih vezavah 338 Md. Mazharul Islam, Md. Reazuddin Repon, Md. Shohan Parvez, Md. Mahbubul Haque, Mohammad Abdul Jalil Factors Affecting Apparel Pattern Grading Accuracy: Existing Software Solutions Comparison and Development of New Solution Dejavniki, ki vplivajo na natancnost gradiranja krojev oblacil: primerjava obstojecih programskih rešitev in razvoj nove rešitve Tekstilec, 2021, Vol. 64(4), 276–285 | DOI: 10.14502/Tekstilec2021.64.276-285 Elise Diestelhorst 1, Jan Lukas Storck 1, Bennet Brockhagen 1, Timo Grothe 1, Inken Blanca Post 2, Thorsten Bache 2, Rumen Korchev 2, Anke Rattenholl 1, Frank Gudermann 1, Andrea Ehrmann 1 1 Bielefeld University of Applied Sciences, Faculty of Engineering and Mathematics, Bielefeld, Germany 2 Bache GmbH, Rheinberg, Germany Necessary Parameters of Vertically Mounted Textile Substrates for Successful Cultivation of Cress for Low-Budget Vertical Farming Lastnosti vertikalno namešcenih tekstilij, potrebne za uspešno gojenje kreše pri nizkocenovnem vertikalnem kmetovanju Original scientific article/Izvirni znanstveni clanek Received/Prispelo 1-2021 • Accepted/Sprejeto 4-2021 Corresponding author/Korespondencna avtorica: Prof. Dr. Dr. Andrea Ehrmann E-mail: andrea.ehrmann@fh-bielefeld ORCID ID: 0000-0003-0695-3905 Abstract A growing population needs an expansion of agriculture to ensure a reliable supply of nutritious food. As a variable concept, vertical farming, becoming increasingly popular, can allow plant growth for local food produc­tion in the vertical sense on, e.g. facades in addition to the classical layered structure in buildings. As substrates, textile fabrics can be used as a sustainable approach in terms of reusability. In our experiment, we investigated which properties a textile should possess in order to be suitable for an application in vertical farming by the example of cress seeds. To determine the best-fitted fabric, four different textiles were mounted vertically, and were provided with controlled irrigation and illumination. Our results showed that a hairy textile surface as provided by weft-knitted plush is advantageous. There, the rooting of cress plants used in this experiment is easier and less complicated than along tightly meshed, flat surfaces, as for woven linen fabrics. Keywords: vertical farming, textile substrates, cress, cost-effectiveness, germination Izvlecek Narašcajoce prebivalstvo potrebuje širitev kmetijstva, da bi si zagotovilo zanesljivo oskrbo s hranljivimi živili. Vertikalno kmetovanje, ki postaja cedalje bolj priljubljeno, lahko kot spremenljiv koncept omogoci rast rastlin za lokalno pridelavo hrane v navpicni legi, na primer ob klasicnih vecplastnih strukturah na fasadah stavb. Za podlago lahko uporabimo tekstilije, ki pomenijo trajnostni pristop v smislu njihove ponovne uporabe. Na primeru semen kreše v našem poskusu raziskujemo, katere lastnosti bi morala imeti tekstilija, da bi bila primerna za uporabo v vertikalnem kmetovanju. Za dolocitev najboljše tekstilije so bile štiri razlicne tekstilije namešcene vertikalno, z nadzorovanim namakanjem in osve­tlitvijo. Naši rezultati kažejo, da ima prednost kosmatena tekstilna površina, ki jo zagotavlja votkovni pliš, pri katerem je ukoreninjenje rastlin kreše, uporabljenih v tem poskusu, lažje in manj zapleteno kot na tesno povezanih, ravnih površinah, kot so na primer lanene tkanine. Kljucne besede: vertikalno kmetovanje, tekstilni substrat, kreša, nizkocenovno, kalitev 1 Introduction The system of vertical farming (VF) has generated increasing attention in recent years. This develop­ment is due to the many advantages of the system, when compared to conventional agriculture, as well as due to the flexibility of the structure, the compo­nents and materials used. In view of a growing pop­ulation [1], the rising demand for nutritious food [2, 3]is expected to increase by about 70% until 2050 [4, 5], while the available arable land is decreasing in the face of growing cities and climate change [6]. One of the challenges to meet this demand lies in the phenomenon of urbanisation, which results in pushing green spaces further out of the city cen­tre, thereby lengthening the transport routes of food products and significantly reducing their quality in terms of nutrients and freshness [7–9]. Furthermore, the carbon footprint caused by the transportation contributes to heavy air pollution and thus global warming [10, 11]. Apart from the insufficient quantity of land, con­ventional agriculture entails a variety of problems including the ongoing destruction of forests [7], which can lead to the loss of native plant and ani­mal species [12], to a loss of biodiversity and degra­dation of ecosystems due to the use of fertilisers and pesticides [3], and to the intense utilisation of water [10, 13], to name just a few. Another challenge of conventional agriculture lies in the invariable external factors such as weather conditions. In view of the changing climate due to global warming, the food supply can often not be ensured, as phenomena like droughts, heatwaves or floods can lead to crop failures [7, 10, 13] with ag­riculture itself contributing to those risks by using methods like intensive groundwater pumping [13]. These issues can partly be solved by transferring plant cultivation from the fields into buildings and utilising systems like VF as an alternative concept to conventional agriculture. This makes the sup­ply of food more reliable for several reasons. The independence from weather and climate change prevents weather-related crop failures and produc­tion can be carried out regardless of the season [7], leading to a higher food security. In addition, no new areas need to be developed and production can be conducted centrally in existing buildings [7, 8, 14]. At the same time, by cultivating into the ver­tical plane, the productivity per unit area increases compared to conventional agriculture [4, 7, 15–17]. Local production can further reduce transport emissions, while the nutrient content can increase by shortening the storage time of plants. The overall environmental pollution is reduced since a local VF system offers a more sustainable solution in terms of used materials and the cultivation of plants re­garding the usage of water and energy resources [7, 8, 18]. Initially, VF is often associated with constructions in the form of ceiling-high shelves in high-rise buildings with the use of hydroponics as an ap­proach for a sustainable production of herbs and plants in general, and the ability of manipulating factors that mimic the natural growing environ­ment, e.g. artificial light sources and heating [8, 16]. Although control over temperature and light­ing brings many benefits in terms of plant growth, these are also the factors that can become problem­atic when it comes to sustainable crop production, depending on building characteristics and location. If outdoor temperature differs greatly from the re­quired indoor temperature, or if the amount of daylight is extremely low or cannot be distributed sufficiently evenly, VF can have high-energy re­quirements. For example, in large cities with many surrounding high-rise buildings, this cannot be op­timally met by renewable energy sources, e.g. solar panels, due to the shading from surrounding build­ings [19]. Alternative concepts, e.g. living walls, utilise substrates like textile fabrics or nonwovens and attach them to walls vertically for city green­ing or for air improvement indoors [18, 21]. Apart from plants, another possibility is the cultivation of algae on textile substrates [22]. The term “agro textile” refers to a variety of textiles applied in areas like agriculture, landscaping and forestry [23] that are used, e.g. as mulch mats [24], hail protection or windshields, in agricultural contexts, all main­ly with the purpose of crop protection [25]. Due to their numerous application possibilities, the textiles themselves differ considerably in their properties and can be woven, nonwoven or knitted [18, 23, 26]. Textiles, however, are usually not applied in VF [22], although they can be more sustainable than the often-used mineral wool. Thus, we are presenting here the findings on inherent textile fabric charac­teristics which enable successful plant growth. This form of farming can easily be adapted for home growth, e.g. herbs on a small scale in the kitchen, and thus generally enable a more widespread ac­ceptance in the population for this relatively new form of soilless plant cultivation. In this context and with a low-budget system, the study aimed to investigate basic parameters of textile substrates for successful germination and cultivation of plants on the example of cress. 2 Experimental The used textiles included woven linen, woven cotton (both plain weave), weft-knitted plush (from 5 threads 100% poly(ethylene terephthalate) (PET) 400 dtex, from Technofibres s.a., Wasserbillig, Luxembourg) and another weft-knitted fabric (1 thread merino Table 1: Parameters of fabrics used in investigation wool 100%, Nm 30/2 (2 threads Nm 30), from Zegna Baruffa, Biella, Italy). The textiles were categorised according to their mass per unit area, thickness and capillary water height. An overview of fabric parame­ters can be found in Table 1. These textiles were selected to allow a comparison of materials that differ significantly in their prop­erties to find an indication which textiles are most suitable for a VF application. Another aspect was the reusability of textiles, which should be cleana­ble after the plants have been removed and reused to cultivate plants again, since their mechanical properties have not substantially changed after the cleaning. Sample number Composition Mass per unit area (g/m2) Thickness (mm) Capillary rise (cm) Photograph 1 Weft-knitted merino wool 970 3.84 12.3 2 PET weft-knitted plush 1020 6.91 2.6 3 Cotton woven 85 0.22 5.8 4 Linen woven 142 0.30 8.4 The mass per unit area was determined according to DIN EN 12127 with an analytical balance SE-202 (VWR International GmbH, Darmstadt, Germany). Thickness was measured according to DIN EN ISO 5084 with a digital gauge J-40-T (Wolf-Messtechnik GmbH, Freiberg, Germany) and capillary rise ac­cording to DIN 53924 after 30 min, using 5 speci­mens per fabric. A digital microscope VHX-600D for samples was the water storage capacity accord­ing to DIN 53923:1978-01. 1.5 Flow (ml/s) 1.0 0.5 (Keyence, Neu-Isenburg, Germany) was utilised for the microscopic images of textiles with the roots of plants to see which fabric offers plants optimal growth conditions, e.g. secure attachment of roots in the meshes, pile and through the stitches. Textiles (60 cm × 20 cm) were attached to a coat­ed metal grid (45 cm in height, 180 cm in width) as shown in Figure 1, which is the same basic struc­ture as in the previous experiment [27]; however, with larger pieces of fabric and a different irrigation rhythm. The irrigation of textiles with supply water (water hardness level 16 °d, i.e. 16 degrees of hardness) took place every 15 minutes using a pump INDOOR P300-I (3.6 W) (Heissner, Lauterbach, Germany), which reuses dripping water and pumps it from a water reservoir under the textiles to the distribution tube above them. Zip ties allowed the water to exit the tube and to irrigate the grid in a well-directed flow, reducing splashes and thus the waste of wa­ter. The flow rate was measured per irrigation hole (cf. Figure 2). In the previous experiment, it was found that although water was distributed slight­ly unevenly throughout the openings, this had no measurable impact on the plant growth [27]. With this type of irrigation, one of the evaluation criteria 0.0 Position number Figure 2: Flow rate through openings; samples were placed in positions 1–3, 4–6 etc. (cf. Figure 1) Illumination was provided by an Osram lamp with the colour temperature of 3011 K, radiant flux of 6.25 W and luminous flux of 2.02 lm for 16 h per day (6 a.m.–10 p.m.). This lamp was chosen due to its wavelength peaks in the areas of chlorophyll A and B absorption, and its broad spectrum, which has been found to be suitable for plant cultivation in the context of VF [28]. Two of these lamps were placed one above the other in front of the test stand at the distance of 50 cm to illuminate it frontally. The resulting irradiance (in W/m2) was measured with a KIMO SL-200. The preparation of samples was the same as in the previous test, using a biodegradable Konjac Gum Powder (Special Ingredients, Chesterfield, UK) Figure 1: Schematic construction, showing fabrics numbered according to Table 1 hydrogel (2 g Konjac Gum Powder dissolved in 240 ml deionised water) to provide the seeds with a better hold and to prevent them from immediately falling [27]. One side of each textile was completely coated with the hydrogel and then the seeds were attached to the textiles. Subsequently, they were im­mediately attached vertically to the test stand. Cress (Lepidium sativum L., Kiepenkerl, Everswin­kel, Germany) was again used as a model organism. The reason was the easy handling due to the fast growth and the usability as food and potential for urban greening. On each piece of fabric, the seeds were arranged in 13 homogeneously spaced rows, each containing 5 seeds, i.e. overall 65 seeds per fabric. In order to be able to make a statement about the quality of plant growth, the fresh mass was deter­mined by cutting the plants above the textile at the end of the test and weighing them directly after­wards. Furthermore, the dry mass was determined to give a better indication of the biomass growth. The dry mass is the pure biomass without water, which is obtained by letting the plants dry in an oven for 48 h at 60 °C. During the course of the experiment, which lasted over the period of 30 days, the main focus was on the water storage capacity of fabrics and the rooting of plants in the materials, which was investigated subjectively with microscopic images. 3 Results and discussion The measured irradiance (W/m2) is presented in Figure 3. The lamp was aligned in such a way that the illumi­nation of fabrics was symmetrically distributed. As already stated in the previous paper [27], the slight varying intensity in the central area does not affect the comparability of plant development on different pieces of fabric as this low level of (varying) irradi­ance only triggers phototropism and the focus can be placed on the suitability of different textiles for the usage in VF [27, 29]. The suitability of textiles for the application in VF was first evaluated on the basis of lost seeds (cf. Figure 4). The reason for some seeds falling off from the textiles was the rinsing away of the Konjac Gum hydrogel, which inevitably happens after a certain period of time due to its water solubility in combi­nation with late germination of the seeds. A large number of lost seeds on Sample 3 is the indication that, despite the Konjac Gum Powder and formed roots, it was not possible for the roots to adhere to the surface of this fabric. This can clearly be at­tributed to Sample 3 being the thinnest fabric with the smallest pores between the neighbouring warp and weft threads, which does not enable the plant roots to penetrate through these pores to get fixed. Sample 2 is considered the most suitable regarding the rooting or the adherence of roots to the sub­strate as the low number of lost seeds (cf. Figure 4) suggests. It should be mentioned that this is in contrast to Khandaker and Kotzen [20] where a “living wall” with vertically mounted pots was applied, using soil and different substrates, hence showing anoth­er way to implement the vertical approach with­out the danger of losing seeds since the substrates inside these vertically mounted pots were only slightly tilted with respect to the ground and not fully vertical. Focusing on the amount of germinated and grow­ing plants (cf. Figure 5), Samples 1 and 2 are advan­tageous, i.e. relatively thick weft-knitted fabrics. Sample 4 had the lowest percentage of grown plants, followed by Sample 3, which can be explained by the poor possibility of rooting in these thin fabrics. Figure 3: Measured irradiance in W/m2; samples were placed in positions 1–3, 4–6, 7–9 and 10–12. 100 80 80 Lost seeds per row (%) 60 40 20 60 40 20 0 0 Sample number Figure 4: Lost seeds on different samples; error bars show standard deviations, calculated from percentage of lost seeds in each of 13 rows. It should be mentioned that some of the seeds were stuck on the fabric without germination; therefore, adding the percentages in Figures 3 and 4 does not result in 100%. When observing the rooting of plants under a mi­croscope, it is noticeable that the roots in Samples 3 and 4 could not find a hold through the interaction Sample number Figure 5: Germinated seeds; error bars show standard deviations, calculated from percentage of lost seeds in each of 13 rows. with meshes (cf. Figure 6c), but instead developed along the surface with the aid of small root hairs (cf. Figure 6d). Looking at the microscopic pic­tures of knitted Samples 1 and 2 (cf. Figures 6a, b), a good rooting through the hairy surface and plush threads, respectively, can be seen. In addition, a less intensive formation of root hairs is visible, which Figure 6: Roots on (a) Sample 1, (b) Sample 2, (c) Sample 3 and (d) Sample 4; arrows indicate root hairs also supports the thesis that the fixation in the tex­tile is a prerequisite for better plant growth due to the reduced requirement of an intensive root devel­opment. Due to a small amount of textile fabrics, it can be assumed that textile substrates should have for successful plant growth high porosity with a hairy surface for the seeds not to fall down before the formation of their germ roots, and to take root in the meshes and the pile without difficulty in fur­ther growth. These parameters are interestingly identical to those found for the growth of micro-and macro-algae [30, 31]. The fact that the surfaces of Samples 3 and 4 require a more intensive formation of root hairs to prevent the plant from falling down may result from the plants on Samples 3 and 4 being shorter than those of Samples 1 and 2 (cf. Figure 7). The latter is also supported by the previous experi­ment [27] which indicated that the water solubility of the Konjac Gum Powder hydrogel can be prob­lematic if it dissolves before the root could anchor in the textile. This makes a high porosity fabric with large pores or a raised surface the roots can grow easily in more advantageous for the application in VF. Nevertheless, it must be mentioned that the dif­ferences among all four samples are not significant, as it is directly visible from the large error bars. Thus, there is only a tendency of plants growing on Samples 1 and 2 to have larger stem lengths. Another factor that is beneficial in promoting growth is the material’s ability to distribute and store water. Samples 1 and 2 have the best water storage properties (cf. Figure 8) and can therefore 40 provide plants with a constant supply of water over a longer period of time. The capillary height, as a measure for water distribution inside the fabric, is less important here due to the irrigation with rela­tively small spaces between the irrigation holes, so that all fabrics were fully wetted. The harvested aboveground fresh mass per plant of each textile is shown in Figure 9a. Sample 2 pro­duced the highest yield, which is also reflected in the amount of dry mass (cf. Figure 9b). Again, a strong difference can be seen between Samples 2 and 4, obtaining by more than 50% less dry mass at Sample 4 compared to Sample 2. However, it must be mentioned again that most dif­ferences are not significant, i.e. standard deviations overlap. Furthermore, while a large number of seeds (65 seeds per sample) was used, especially for Sample 4 where less than 20% germinated (cf. Figure 5), the statistical significance based on standard deviations is lower than it could be expected at first glance. Finally, it must be mentioned that the results pre­sented here are valid for a certain period during the year (in this case end of July until the end of August in Western Europe) and may be different in other seasons. This effect is well known from indoor plant growth experiments, even inside climate rooms, which is why such experiments are usually repeat­ed subsequently [32–34]. In consequence, the results obtained in this study can only serve to choose tex­tile fabrics for future experiments where objective, time-independent findings can be reported, i.e. for the differentiation between the two thin-woven 40 30 30 20 10 Stem lengths (mm) 20 10 0 0 Sample number Sample number Figure 7: Plant lengths; error bars show standard Figure 8: Water storage capacity deviations, calculated from all germinated seeds with grown stems (depending on germination rate, 10–42 plants per sample) 15 Fresh mass per stem (mg) 60 50 40 30 20 10 0 10 5 0 Sample number S pl ber Figure 9: (a) Total aboveground fresh mass per plant, (b) total dry mass per stem; error bars show standard deviations, calculated from all germinated seeds with grown stems. fabrics (Samples 3 and 4), which are clearly not suit­able for root fixation, and different thicker knitted fabrics (Samples 1 and 2) which allowed the pene­tration by plant roots and will thus be investigated in further studies. 4 Conclusion and outlook In this experiment, four different fabrics were com­pared regarding their applicability in vertical farm­ing, i.e. vertically positioned substrates, with cress as a test plant over the course of 30 days. In general, it was found that textile substrates should have for successful plant growth high po­rosity with a hairy surface to enable the penetra­tion of roots into the fabric. Furthermore, a corre­lation between the water absorption capacity and biomass growth can be assumed. Overall, Sample 2 (weft-knitted plush) showed the best combination of good rooting properties, high germination rate, good water storage capacity, and high fresh and dry matter. For future trials, considering water usage and sus­tainability, we will investigate these and other rela­tively thick, open-pore materials with different wa-ter-storage properties, and change the duration and frequency of irrigation to see if the amount of used water can be reduced by less frequent irrigation. Additionally, other more agronomically important plants should be in the scope of future research. Funding The project was partly funded by the Federal Ministry for Economic Affairs and Energy in the scope of the ZIM project ZF4036107 and by the HiF fund of the Bielefeld University of Applied Sciences. Acknowledgments We thank Martina Holt and Karl-Josef Dietz for their constructive criticism of the manuscript, lend­ing laboratory equipment and for advice on the im­plementation of the experiments. References 1. Selected Results of the 2019 UN World Population Projections. Population and Development Review, 2019, 45(3), 689–694, doi: 10.1111/padr.12288. 2. ICKOWITZ, A., POWELL, B., ROWLAND, D., JONES, A., SUNDERLAND, T. Agricultural intensification, dietary diversity, and markets in the global food security narrative. Global Food Security, 2019, 20, 9–16, doi: 10.1016/j. gfs.2018.11.002. 3. HUNTER, Mitchell C., SMITH, Richard G., SCHIPANSKI, Meagan E., ATWOOD, Lesley W., MORTENSEN, David A. Agriculture in 2050: re­calibrating targets for sustainable intensification. 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Tekstilec, 2021, Vol. 64(4), 286–297 | DOI: 10.14502/Tekstilec2021.64.286-297 Aleksandra Micic 1, Ivanka Ristic 2, Suzana Djordjevic 2, Nebojsa Ristic 2, Dragan Djordjevic 1 1 University of Nis, Faculty of Technology, Bulevar oslobodjenja 124, 16 000 Leskovac, Serbia 2 Academy of Vocational Studies Southern Serbia, Department of Technological Art Studies, Vilema Pušmana 17, Leskovac, Serbia Adsorbent from Textile Waste for Removal of Textile Reactive Dye from Water – Equilibrium Adsorption and Kinetics Adsorbent iz tekstilnih odpadkov za odstranjevanje tekstilnega reaktivnega barvila iz vode –adsorpcijsko ravnotežje in kinetika Original scientific article/Izvirni znanstveni clanek Received/Prispelo 4-2021 • Accepted/Sprejeto 10-2021 Corresponding author/Korespondencni avtor: Prof dr. Dragan Djordjevic Phone: ++381 1 62 47 203 E-mail: drag_64@yahoo.com ORCID ID: 0000-0002-8223-9474 Abstract The removal of textile reactive dye from an aqueous solution on a new adsorbent prepared from waste cotton knitted fabric was investigated in this study. Waste cotton textile, used for the production of adsorbents, is a by-product of the cutting of stacked parts of cotton knitwear planned for the production of women’s T-shirts. The degree of efficiency of a paper pattern determines the amount of collected waste. The qualitative and quantitative characterization of the new adsorbent showed carbon and oxygen to be dominant in the chemical composition. A longer contact time means a greater amount of dye on the adsorbent, i.e. the dye concentration in the solution decreases with the duration of the adsorption process. The percentage of removed dye decreases with an increase in the initial dye concentration in the solution. However, the actual amount of adsorbed dye increases as the initial dye concentration increases. The results for equilibrium adsorption show that the Langmuir isotherm can be used for the interpretation of reactive dye adsorption on a new adsorbent. The pseudo-first order model can be fully used to describe the kinetics of dye adsorption on an adsorbent, with respect to valid results for statistical indicators. Based on the results, it can be concluded that the new adsorbent obtained from waste textiles has the potential to remove textile reactive dye from aqueous solutions. Keywords: cotton knitted fabric, cutting, adsorbent, reactive dye, the Langmuir model, kinetics Izvlecek V clanku je bila raziskana odstranitev tekstilnega reaktivnega barvila iz vodne raztopine s pomocjo novega adsorbenta, pripravljenega iz odpadnega bombažnega pletiva. Uporabljena odpadna tekstilija je bila stranski proizvod krojenja bombažnega pletiva, položenega v plasti za izdelavo ženskih kratkih majic, pri cemer izkoristek papirnatega kroja doloca kolicino zbranega odpadka. Kvalitativna in kvantitativna karakterizacija novega adsorbenta kažeta, da sta v kemicni sestavi prevladujoca elementa ogljik in kisik. Daljši kontaktni cas pomeni vecjo kolicino barvila na adsorbentu, torej se s casom trajanja procesa adsorpcije koncentracija barvila v raztopini zmanjšuje. Odstotek odstranjenega barvila se zmanjšuje s povecevanjem zacetne koncentracije barvila v raztopini, vendar se dejanska kolicina adsorbiranega barvila z narašcanjem zacetne koncentracije barvila poveca. Rezultati adsorpcijskega ravnotežja kažejo, da se Langmuirjeva izoterma lahko uporabi za interpretacijo adsorpcije reaktivnega barvila na novem adsorbentu. Model psevdoprvega reda se lahko v celoti uporabi za opis kinetike adsorpcije barvila na adsorbentu glede na veljavne rezultate statisticnih kazalnikov. Na podlagi rezultatov lahko sklepamo, da ima novi adsorbent, pridobljen iz odpadnega tekstila, potencial odstranjevanja tekstilnih reaktivnih barvil iz vodnih raztopin. Kljucne besede: bombažno pletivo, krojenje, adsorbent, reaktivno barvilo, Langmuirjev model, kinetika 1 Introduction The textile industry consumes an extensive amount of synthetic dyes. The aim is to use dyes that are more exhausted from the bath during dyeing, as well as those that are more degradable and envi­ronmentally friendly, or that can be more easily re­moved from water after textile dyeing [1, 2]. Reactive dyes belong to the class of very successful modern synthetic dyes thanks to their wide range of shades, flexibility in application and excellent fastness properties, particularly when wool, silk and cotton, as well as regenerated cellulose fibres, are dyed. These dyes contain certain groups ca­pable of forming covalent bonds with nucleop­hilic sites on the fibre, which is an assumption of the extraordinary properties of colour fastness in terms of washing. Reactive dyes for wool are considered alternatives to chrome dyes. Certain classes of reactive dyes have a positive effect on the amount of damage to wool during dyeing at the boiling point [3]. After textile dyeing of natural or artificial origin, waste water from the textile industry is inevitably dyed, as it contains a higher or lower amount of or­ganic dye residues. One of the methods for remov­al of organic matters from dyed water is the use of porous solid sorbents. The properties of these sub­stances that make them useful are high porosity and their surface, as well as the physical and chemi­cal nature of the inner surface. Such and similar ad­sorbents, e.g. activated carbon, are most frequent­ly used in separation and purification processes. Research aimed at finding alternative adsorbents that could replace expensive activated carbon have intensified recently. Industrial waste materials are potentially inex­pensive adsorbents for removing organic matter from water. To date, researchers have used various waste materials of cellulose origin, e.g. agricultur­al or agro-industrial waste of cellulose origin, such as barley straw, rice husks, cotton stalks, the pits of various fruits and vegetables, etc. There was no example of the use of waste from a garment plant for the production of active adsorbent that would be used for the adsorption of waste reactive dye from aqueous solutions [2, 4-6]. If other types of dye and a similar adsorbent are taken into account, there are studies that describe, for example, the adsorption processes of methylene blue (basic thiazine dye) on an adsorbent of cotton stalk, cotton waste fibres and cotton dust [7, 8]. It has been observed that these types of adsorbents can be successfully used to re­move methylene blue from aqueous solutions using the sorption technique. Sorption increases by in­creasing the initial dye concentration, temperature, sorbent dose and solution pH. The time required for maximum dye removal was 90 minutes. Maximum dye removal of up to 97.50% was achieved in all test­ed experimental conditions [7, 8]. The research presented in this paper uses precise­ly that waste material which thus far has typically been incinerated or disposed of in a landfill. This research proposes a new way of disposing of this waste, turning it into a useful product for the pu­rification of coloured water. The aim is to use the resulting waste textile material, transform it into an adsorbent and use it for the removal of colour from water. Applying the equilibrium isotherm and the adsorption kinetics of textile dye has led to signif­icant knowledge about the adsorption mechanism and feasibility of the decolorization process of aque­ous solution. 2 Experimental 2.1 Materials An adsorbent is made of the waste textiles from cot­ton knitted fabric after the cutting process in the manufacture of women’s T-shirts. It is a by-product obtained from the cutting of the stacked parts of cotton knitted fabric during the clothing manufac­ture process. The raw material for the production of adsorbent was collected from a professional work­shop. The amount of raw material waste was about 6 kg per one cutting of a multilayer stacked textile knitted fabric. Since the waste cotton material was collected from the cutting of the cut parts of the future garment, the construction preparation of the women’s T-shirt was monitored using a Gerber Technology comput­er software system. The optimal width of the basic material (140, 145 and 152 cm) was selected on the basis of the use of the paper pattern made using a CAD system during the production of the selected model of the women’s T-shirt. Knitted fabric made of 100% cotton fibres was used to make the selected model of a women’s T-shirt with raglan sleeves. Table 1 shows the basic char­acteristics of the material (knitted fabric) that was used to make women’s T-shirt as the by-product of cutting. Table 1: Basic characteristics of knitted fabric for women’s T-shirt production Properties Description/values Raw material composition Cotton, 100% Colour White Weaving Double knit plated Horizontal density (1/cm) 14.6 Vertical density (1/cm) 20.5 Fineness of yarn (tex) 18 Surface mass (g/m2) 165 The new adsorbent was obtained through the chem­ical and physical modification of cotton waste. After its collection, the waste was washed (distilled wa­ter, bath ratio 1 : 100, 60 minutes at 90 °C), dried and cut into pieces as small as possible. Such a pre­pared waste was treated with a solution of H3PO4 (Oleohemija, Serbia, 85%, ratio 1:4) for 48 hours at room temperature. After decantation, the sam­ples were heated at 600 °C for 2 hours. Cooling and shredding followed, then rinsing with distilled wa­ter and neutralization with an aqueous solution of sodium carbonate (Tehnohemija, Serbia). Finally, the drying (100 °C) and grinding of the materi­al was performed, and samples were prepared for adsorption. 2.2 Adsorption process An adsorption model test was performed in reac­tion vessels in which the adsorbent was suspended in a reactive dye solution (adsorbate). The reaction vessels were placed on a shaker (130 rpm) at a tem­perature of 20 °C and maintained for some time. The amount of adsorbent was fixed at 2 g, whereas the solution in a constant amount of 0.1 dm3 con­tained a reactive dye concentration of 30, 50, 75, 100, 125 and 150 mg/dm3. Processing time was 5, 10, 20, 30, 40, 50 and 60 minutes. The pH for all dye solution was 3. The reactive dye used, CI Reactive Red 84 (RR84), belongs to the group of monoazo dyes with two sul­fo groups and one amino. The structure comprises sulfonyldibenzen, naphthalene and bromoacryla­mide part. The dye is water-soluble, and is used for the dyeing and printing of wool and silk fabrics. 2.3 Analyses and measurements Solution absorption was measured on a UV-VIS spectrophotometer (Cary 100 Conc UV-VIS, Varian) at . = 490 nm (the maximum wavelength of the spectrum of the used dye solution). The mois­ture content in the sorbent was determined accord­ing to the SRPS EN ISO 18134 standard. The ash content in the sorbent was determined according Figure 1: Structure of the used reactive RR84 dye to the SRPS ISO 5984 standard. The density of the sorbent by pycnometer was determined accord­ing to the SRPS EN ISO 2811-1 standard. SEM and EDS measurements were performed on a TESCAN MIRA3 microscope. The samples were applied to an adhesive graphite strip and fixed to the supports, and then ion-coated with a thin layer of gold using a PO-LARON SC502 Sputter Coater. The degree of dye removal [5] or degree of exhaus­tion was calculated on the basis of the dye concen­tration before and after this treatment: ....!- ....",$ ....= ·100 (1) ....% where: C0 and Ct,e (mg/dm3) represent the initial and final (equilibrium) concentration of the dye solu­tion, respectively. The amount of adsorbed dye (adsorbate) per unit mass of adsorbent [9] at time t, qt (mg/g), or equi­librium time, qe, (mg/g), was determined using the equation: $....$- ....!,#'·.... ....!,#= (2) .... wherein: M (g) represents the mass of adsorbent and V (dm3) represents the volume of solution from which the adsorption was performed. The Langmuir isotherm [4] is presented using fol­lowing equation: 1$1 11 =(·+ (3) ....! ....·...."....! ...." where: Q0 (mg/g) represents the maximum amount of adsorbate that can bind to the adsorbent and b (dm3/mg) represents the ratio of the adsorption rate constant and the adsorbate desorption rate constant. Adsorption kinetics data are described using the Lagergren model [9] of pseudo-first order: log(....!-....")=log(....!)- ....# ·.... (4) 2,303 where k1 (1/min) represents the rate constant of ad­sorption pseudo-first order. The adsorption kinetics can also be described using the pseudo-second order model [9]: .... 11 = + ·.... (5) " ....! ...."·....# ....# where k2 (g/mgmin) represents the adsorption rate constant of the pseudo-second order. 3 Results and discussion 3.1 Origin of textile waste Figure 2 is a graph showing the efficiency of paper patterns in the manufacture of women’s T-shirts, resulting in waste used to create a new adsorbent for the adsorption of reactive dyes. All paper patterns show the expected efficiency obtained when fitting the cutting parts. On the basis of these results, the paper pattern with a width of 152 cm had the high­est material efficiency (85.82%) in relation to the other widths, due to more suitable combinations of cutting parts. Figure 2: Graphic representation of the degree of effi­ciency of paper patterns with respect to their widths 3.2 Adsorbent characterization The characterization of the absorbent was per­formed for the purposes of the representation of physical properties, as well as the introduction of morphological characteristics, or the actual chemi­cal structure, as a very important factor for success­ful adsorption. The determination of yield, density, ash content, moisture, etc. are techniques that provide informa­tion regarding the structure of the tested samples, but also regarding their reactivity and the possibili­ty of application in appropriate conditions. The loss after washing of raw cotton waste, before transformation into an adsorbent, was approxi­mately 8% in relation to the sample of waste before washing. The yield of adsorbent from waste cotton textiles was approximately 42%. The moisture content of the new adsorbent was 7.8%. The presence of moisture affected the activi­ty in adsorption processes. Namely, the moisture that was largely adsorbed in the structure of the adsorbent obtained from waste textiles blocks the pores of the material, making them inaccessible to dye ions from the solution. The consequence of this effect was a decrease in the adsorption capacity towards the dye ions that were adsorbed from the solution into the porous structure of the adsorbent. The ash content in the adsorbent may indicate a conversion pathway from the used precursor-waste cellulose textile. Typically, a powder adsorbent with high values of ash content show weaker adsorption power with respect to different adsorbates. The pro­portion of ash in the structure of the new adsorbent was 6%. The amount of ash was moderate, in this case, so there would be no obstacles to good sorp­tion characteristics of the adsorbent in the process­ing of dyed water. The determination of adsorbent particle density, including pore volume within the particles, was performed using a pycnometer. The new adsorbent had a density of 1.2 g/cm3. Density values of the ad­sorbent were in a range typical for materials from cellulosic raw materials. Density is an important property of powder materials and illustrates poros­ity and the way the particles are packed in space. Porous materials with lower density have more air trapped in the structure. The used adsorbent is a granular material with het­erogeneous porous particles of divergent shape and form. Cracks, cavities and channels are present in the depth of the particles that are the basis of the porosity of the material. The micrograph in Figure 3 shows the appearance of adsorbent particles at a magnification of 2000x. The EDS system enables a quick assessment of the elementary composition of the sample. The follow­ing chemical elements were detected: C (41.87%), O (54.34%) and Na (3.79%). According to the EDS analy­sis, there was carbon, as expected, while the increased presence of oxygen related to the oxides of metals (Na), while an adsorbent might have reacted with ox­ygen from the air during the annealing process. Figure 3: SEM micrograph of the applied adsorbent form textile waste mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 Figure 4: Change of the initial dye concentration of RR84 during adsorption to a new adsorbent for different initial concentrations A similar morphology and chemical composition were seen in research [10] that deals with the prepa­ration of cheaper and environmentally friendly ad­sorbents from biomass, with the use of phosphoric acid as the activator. Via SEM and EDXA spectra, the existence of the porous structure was asserted, as well as the presence of carbon and oxygen, which were dominant amongst chemical elements. The presence of potassium, sodium and phosphorus was negligible. The selected RR84 dye has good solubility with respect to the existence of two sulfo groups, and shows a good affinity to the adsorbent in contact, given that there is no greater affinity towards the aqueous phase. The present sulfo groups represent a negative characteristic of this dye, whereas an ami­no group increases reactivity in the aromatic ring due to the electron donor [11]. It is known that adsorption from a solution to­wards a solid surface begins to occur when dipoles or charged types of adsorbent and adsorbate inter­act with each other. Also, the exchange of anions or cations occurs when the neutral molecules get close enough to each other. Similarly, an interaction occurs between the dissolved organic components (dyes), the molecule of the solvent (water) and the surface of the adsorbent [12]. 3.3 Influence of certain factors on adsorption The influence of the time of adsorption on the ex­haustion of the RR84 dye was tested in a concen­tration range of 30–150 mg/dm3 (Figure 4). As time increases, the initial dye concentration decreases in all cases. The initial dye concentration in the solu­tion provides an important driving force for over­coming the mass transfer resistance between the aqueous and solid phases. According to the curves in the graph presented in Figure 4, the higher initial dye concentrations of RR84 declined slightly more over time, while low­er initial concentrations showed a more moder­ate change over time. All curves in the graph have a similar appearance of change over time, which shows similar or identical mechanisms of adsorp­tion of dye molecules on the outer surfaces and in­side the adsorbent particles. Figure 5 presents a graph that explains the change in the level of exhaustion of RR84 dye relative to the duration of adsorption. The highest percentage of dye exhaustion occurs at the lowest initial dye mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 Figure 5: Degree of exhaustion of RR84 dye during adsorption to a new adsorbent for different initial concentrations concentrations, while the lowest percentage is pres­ent at the highest initial concentrations. All curves demonstrate an upward trend. On the other hand, the largest amount of the adsorbed dye from the aqueous solution in absolute terms, is found with the highest initial concentrations. Thus, for example, in equilibrium (after 60 minutes): • at the highest initial concentration (150 mg/dm3), the degree of exhaustion was 61% or 91.5 mg in absolute terms; and • at the lowest initial concentration (30 mg/dm3), the degree of exhaustion was 79.33% or 23.8 mg in absolute terms. • There was thus almost four times more of the adsorbed dye to the new sorbent (91.5 mg >> 23.8 mg) at the highest initial concentration, although a lower percentage of the degree of ex­haustion occurred here (61% < 79.33%). Similar results are shown by a study of the adsorp­tion potential of rice husk and alkali-treated rice husk to remove yellow reactive dye from an aqueous solution. The highest adsorption was achieved after 40 minutes and did not change after that time. The first adsorbent was found to remove 65% of the dye within 40 minutes compared to the second which removed 92% [5]. The graph in Figure 6 shows the change in the ad­sorbed amount of dye per unit mass of adsorbent during adsorption (adsorption capacity) for differ­ent initial dye concentrations of RR84. The graph confirms that the amount of adsorbed dye increases relative to the duration of adsorption, and that the highest adsorption was observed at the highest in­itial concentrations. Since the curves have a simi­lar appearance in the graph, it is assumed that the mechanism of adsorption at all initial concentra­tions is identical. Similar behaviour in terms of the degree of exhaus­tion of the reactive dye (Bezaktiv Red S-Maks) was seen in a study [6] that estimated the different ac­tivated carbon prepared from by-products from agricultural waste. It was observed that adsorption was more rapid during the initial phase of the ad­sorption process, followed by a slower stage until equilibrium was reached. This phenomenon was due a large number of free positions exposed to mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 Figure 6: Change of adsorption capacity of RR84 dye during adsorption on a new adsorbent for different initial concentrations adsorption in the initial phase, which made the tak­ing of the remaining places on the surface harder because of the refusal between the adsorbate and adsorbent. 3.4 Adsorption izotherms The graph in Figure 7 represents the linear inter­pretation of the Langmuir adsorption isotherm, showing the dependency of the parameter (1/qs ) in relation to the equilibrium dye concentration (1/Cs ). The values of the Langmuir constants were deter­mined from this graph, i.e. the slope and cut of the functional line. The significant functionality of this parameter was observed from this graph, i.e. the fitting curve per­fectly covers the experimental points. It can thus be concluded that the Langmuir adsorption isotherm can be used for the analysis of this specific case of RR84 dye adsorption onto the adsorbent. The Langmuir constants Q0 and b represent to the maximum amount of adsorbate that can bind to the adsorbent and the free adsorption energy, respec­tively. The values of these constants were 8.35 mg/g and 0.027 dm3/mg, respectively. In this particular case, the Langmuir model had a very high value of R2, which was 0.997. The features of the Langmuir isotherm can be ex­pressed in dimensionless constant, equilibrium parameter RL. In the specific case of RL= 0.2, it was confirmed that the applied Langmuir isotherm was suitable since the equilibrium parameter was be­tween 0 and 1. Similarly, in other research, [10] the application of cheaper and more environmentally friendly adsor­bents from biomass for the needs of purification of reactive dye (Reactive red 23) from aqueous solution confirmed the dominance of the Langmuir mod­el after comparison with the four most frequently used equilibrium adsorption models. 3.5 Adsorption kinetics According to the linear forms of kinetic model in Figure 8, it can be concluded that the rate of adsorp­tion, in the presented experimental conditions, can be functionally described in full by the pseudo-first order. Figure 7: Modelling of RR84 dye adsorption on new adsorbent using the Langmuir model Figure 8: Kinetic curves of RR84 dye adsorption on a new adsorbent according to the pseudo-first order model Thus, according to the appearance of curves on fabric, is perfectly described by the pseudo-first or-this graph, as well as the positions of the experi-der model. mental points around the ideal fitting curves, it Table 2 presents the value of the kinetic parameter was determined that the kinetic adsorption of of the RR84 dye adsorption process on the adsor­RR84 dye on the adsorbent from cotton textiles, bent from the waste cotton (equilibrium constant obtained from waste after cutting of cotton knitted rate of the pseudo-first order) for all of the initial Table 2: Kinetic parameters of the RR84 dye adsorption process on new adsorbent (pseudo-first order, 20°C) Dye concentration (mg/dm3) q (mg/g) t,exp q (mg/g) t,izr k (g/mg×min) 1 R2 RSS 30 1.19 1.41 0.063 0.957 0.05 50 1.93 2.42 0.066 0.945 0.07 75 2.85 3.49 0.064 0.952 0.06 100 3.64 4.67 0.068 0.942 0.08 125 4.37 5.50 0.069 0.956 0.06 150 4.57 5.39 0.064 0.971 0.04 mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 mg/dm3 Figure 9: Kinetic curves of RR84 dye adsorption on a new adsorbent according to the pseudo-second order model dye concentrations, values for the parameter qe (calculated, q and experimental, q) and sta- e, izre, exp tistical indicators of validity. The pseudo-first order model has, in all cases, a coefficient of determi­nation greater than 0.940 (0.945-0.971), resulting in a high functionality, where the model can be accurately used to describe the process of dye ad­sorption on the adsorbent. Also, according to the statistical parameter residual sum of squares (RSS), whose values are approximately zero, the validity of the results of the modelling of kinetics using the pseudo-first order model can be confirmed. The differences between parameters q and q e, izre, exp are approximate for this model, but again not com­pletely identical. According to the data presented in Table 2, the rate constant of pseudo-first order is not dependent on the initial dye concentration in the solution, which in turn confirms the validity of the results of that model. The adsorption kinetics according to the pseu­do-second order model (Figure 9) are presented us­ing the graph of the dependence of t/qt on time. By fitting the data to a graph, functional straight lines for all the initial dye concentrations were obtained. This model includes all phases of adsorption, such as external diffusion, adsorption and internal diffu­sion in particles, since it is pseudo model. It was es­tablished by comparing the curves from the graph, as well as the appearance and the dispersion of the points around the ideal curve fitting, that the ki­netics of RR84 dye adsorption to the adsorbent are sufficiently described by the pseudo-second order model. Table 3 shows the value of the kinetic parameters of the adsorption process of the reactive dye on the adsorbent (the equilibrium rate constant for the pseudo-second order) for all the initial dye concen­trations, values for parameter qe (calculated, q e,calc and experimental, q) and statistical indicators e,exp of validity. In all cases, the kinetic pseudo-second order model had a coefficient of determination of R2>0.97, thereby achieving a high degree of func­tionality (better than that of the pseudo-first order model), when the model can be used to describe the dye adsorption process on the adsorbent with suffi­cient certainty. On the other hand, the differences between pa­rameters q and q are more significant for this e,izre,exp model than in the pseudo-first order model. Also, a greater variation of the rate of constant k2 with a change in the initial dye concentration, as well as a very high number of values for the residual sum of square far greater than zero, push the pseudo-second order model into the background and give prefer­ence to the pseudo-first order model. It can be concluded that the adsorption of RR84 dye on an adsorbent is of a physical nature, although it can be supported at any time by chemisorption, giv­en the results of kinetic analysis, as well as the fact that the rate of equilibrium is rapid, which character­izes physisorption and activated chemisorption [13]. A similar observation was made in the study of the adsorption kinetics of reactive yellow and blue dyes on an adsorbent made by modifying agricultural residues from sugar cane processing. Dye adsorp­tion is well described by the kinetic pseudo-first order model for reactive yellow and pseudo-second order for reactive blue dye [14]. 4 Conclusion With phosphoric acid as an activating agent, the thermochemical conversion of waste cotton tex­tile into a powder adsorbent was performed. The obtained adsorbent was tested for physical and chemical properties. The element composition of the produced adsorbent was dominated by carbon and oxygen, while the surface morphology shows porosity. The removal of reactive azo-dye with the help of the adsorbent was tested under different conditions. It was found that the adsorption depended on contact time and initial dye concentration. The Langmuir equilibrium model perfectly de­scribes the process of adsorption of reactive dye on the adsorbent from waste cotton textiles from the cutting of knitted fabric during the production of women’s T-shirts. The kinetic pseudo-first and pseudo-second order models excellently described the change in the ad­sorption rate of the reactive dye on the adsorbent, but preference was still given to the pseudo-first or­der model. Based on these results, it can be concluded that the adsorbent obtained from the waste cotton textile may be an effective adsorbent for the removal of the reactive azo-dyes from an aqueous solution, with a reasonable tendency of application in industrial conditions, as well. References 1. PUASA, S.W., ISMAIL, Khairul N., KHAIRI, N.A.I.A.Cleavable surfactant-impregnated acti­vated carbon for enhanced adsorptive removal of reactive dye from an aqueous solution. Materials Table 3: Kinetic parameters of RR84 dye adsorption process on new adsorbent (pseudo-second order, 20°C) Dye concentration (mg/dm3) q (mg/g) t,exp q (mg/g) t,izr k (g/mg×min) 2 R2 RSS 30 1.19 1.65 0.026 0.980 18.47 50 1.93 2.70 0.015 0.980 7.18 75 2.85 4.04 0.010 0.977 3.65 100 3.64 5.16 0.008 0.978 2.16 125 4.37 6.14 0.007 0.982 1.24 150 4.57 6.41 0.006 0.981 1.16 Today: Proceedings, 2018, 5(10), 22020–22028, doi: 10.1016/j.matpr.2018.07.063. 2. DASH, Subhajit, CHAUDHURI, Haribandhu, GUPTA, Radha, NAIR Udayabhanu G. 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Tekstilec, 2021, Vol. 64(4), 298–304 | DOI: 10.14502/Tekstilec2021.64.298-304 Ilda Kazani 1, 2, Majlinda Hylli 1, Pellumb Berberi 3 1 Polytechnic University of Tirana, Department of Textile and Fashion, Mother Teresa Square No.1, Albania 2 Albanian Young Academy, Shëtitorja Murat Toptani 1000 Tirana, Albania 3 Polytechnic University of Tirana, Department of Engineering Physics, Bulevardi Dëshmorët e Kombit Nr. 4, Tirana, Albania Electrical Resistivity of Conductive Leather and Influence of Air Temperature and Humidity Elektricna upornost prevodnega usnja ter vpliv temperature in vlažnosti zraka Original Scientific Article/Izvirni znanstveni clanek Received/Prispelo 1-2021 • Accepted /Sprejeto 3-2021 Corresponding author/Korespondencna avtorica: Assoc Prof dr. Ilda Kazani E-mail: ikazani@fim.edu.al ORCID ID: 0000-0002-5727-5553 Abstract Leather is a material that has been used in different applications for centuries. Today, living in the era of high-tech­nology, we are surrounded by smart products. For this reason, traditional products must be changed or im­proved in order to support and make us more comfortable while using them. For instance, the touch screen display in electronics products is a smart phone’s or a tablet computer’s primary input device. Still, traditional leather will not function properly in a cold climate or other specific conditions. To make it conductive in such conditions, the double in-situ polymerization of the pyrrole coating method was used. The aim of this study was to observe the electrical properties of conductive leather. At the same time, it stands up to a wide range of different air temperatures, and relative and absolute humidity. These properties are essential because de­signers and textile engineers should be familiar with them when they decide to use materials in different smart products. Electricity conductivity tests were carried out in year-round temperatures from 7.5 °C to 28.1 °C, with a relative humidity from 18% to 77% and a vapor air concentration from 2.77 g/kg to 12.46 g/kg. The so-called “multiple-step method” was used to test leather’s electrical resistivity for the first time. The method considers a material’s compressional properties and provides an indicator inherent for a material’s electrical properties, regardless of the mass and shape of samples. The results showed a strong dependence between water vapor air concentration and electrical resistivity, described using the formula . = 1.3103 H-1.04 Om, with a correlation coefficient of 0.87. There was no relation between relative humidity and electrical resistivity, and resistivity and air temperature. Also, the results confirmed again that changes in the shape of the sample used during tests did not influence the measurement’s results, but supported the appropriateness of the measuring method. Keywords: air humidity, conductive leather, electrical resistivity, multiple-step method. Izvlecek Usnje se kot material že stoletja uporablja v razlicnih aplikacijah. Danes, ko živimo v dobi visoke tehnologije, smo obkroženi s pametnimi izdelki. V ta namen je treba tradicionalne izdelke spremeniti ali izboljšati, da bi jih nadgradili in naredili primernejše za rabo. Na primer, v elektronskih izdelkih je zaslon na dotik primarna vhodna naprava pametnega telefona ali tablicnega racunalnika. Ker tradicionalno usnje v hladnem okolju ali drugih posebnih razmerah ne deluje, je bilo površinsko obdelano z metodo dvojne in situ polimerizacije pirola. Cilj te študije je opazovati elektricne lastnosti prevodnega usnja v širokem razponu razlicnih temperatur, relativne in absolutne vlažnosti zraka. Te lastnosti so bistvene, ker oblikovalci in tekstilni inženirji morajo poznati te lastnosti, ko se odlocijo za uporabo materiala v razlicnih pametnih izdelkih. Testi elektroprevodnosti so potekali eno leto pri temperaturah od 28,1 °C do 7,5 °C, pri relativni zracni vlažnosti od 77 % do 18 % in koncentraciji vodne pare v zraku od 12,46 g/kg do 2,77 g/kg. Prvic je bila za testiranje elektricne upornosti usnja uporabljena t. i. „metoda z vec koraki“. Ta upošteva tlacne lastnosti materiala in zagotavlja indikator, ki je vezan na elektricne lastnosti materiala, ne glede na maso in obliko vzorcev. Rezultati so pokazali mocno odvisnost med koncentracijo vodne pare v zraku in elektricno upornostjo, opisano z zvezo . = 1.3103 H-1.04 Om, s korelacijskim koeficientom 0,87. Med relativno zracno vlago in elektricno upornostjo ter upornostjo in temperaturo zraka ni bilo povezave. Prav tako so rezultati ponovno potrdili, da spremembe oblike vzorca, uporabljenega med preizkusi, niso vplivale na rezultate meritev, kar potrjuje vrednost merilne metode. Kljucne besede: zracna vlaga, prevodno usnje, elektricna upornost, vecstopenjska metoda 1 Introduction Leather is a natural product made by converting animal hides and skins using tannage [1]. This ma­terial has been used in different applications for centuries after numerous mechanical and chemical operations. Moreover, this material has excellent insulating properties [2, 3], making it essential for various applications such as clothing, upholstery, footwear, automotive products and accessories. Today, however, we live in a high-tech world sur­rounded by smart products. For this reason, tra­ditional products must be changed or improved to support and make us more comfortable while using them. For instance, the touch screen display in electron­ics products is the primary input device of a smart phone or a tablet computer. Still, traditional leather will not function properly in a cold climate or other specific conditions. A great deal of research has been done on the trans­formation of textiles into conductive materials, in­cluding leather in the last decade. In this way, elec­trically conductive materials can be applied to the leather’s surface to be used as a touching operator for a capacitive touch screen panel. Consequently, the treated leather samples show electrical conductivity and are expected to have a reasonable working performance on a capacitive touch screen [2-10]. Various methods are used to evaluate the electro-conductive properties of textile and leather materi­als. Those methods provide indicators that are diffi­cult to compare with each other. For this reason, we decided to use the so-called “multiple-step method” for measuring the electrical resistivity of our manu­factured leather’s electrical resistivity [5, 11, 12]. The method takes into consideration the compressional properties of a material. It provides an indicator in­herent for a material’s electrical properties, regard­less of the mass and shape of samples. When investigating the electrical resistivity of con­ductive leather, certain parameters such as environ­mental conditions must be considered. We typically take into account standard air temperature and hu­midity conditions for textile materials’ physical and mechanical properties. Nevertheless, it is important for applications of con­ductive leather to know what happens to the elec­trical properties in a wide range of air temperatures and relative and absolute humidity. In this paper, we attempt to give more information about this smart leather to designers and textile engineers, who should be familiar with these properties when they decide to use this smart material in different appli­cations such as clothing, bags, footwear, automobile seats or furniture. 2 Experimental 2.1 Materials and methods White sheep crust leather of Albanian origin was used in this research. The leather was initially cut into 8 cm x 8 cm pieces with a thickness of 0.97 mm ± 0.2 mm. The leather was only chrome tanned and dried. A double in-situ polymerization of pyrrole coating was used to make the material conductive. The chemicals used here were pyrrole, ferric chloride, anthraquinone-2-sulfonic acid sodium salt mono-hydrate of laboratory-grade and high purity [2]. The multiple-step method was used to measure the electroconductive properties of this conductive leather [11-12]. This method consists of measuring the electrical re­sistance of the sample compressed to different vol­ume fractions within a measuring cell, as shown in Figure 1. A reciprocal power function then approxi­mated the dependence of the textile material’s elec­trical resistance on its volume fraction (Vf ) within the measuring cell. *% .... .... $" ....=........!**........"....=....#-(1) ....·........!.....# where . represents electrical resistivity in .m, m represents the mass of the sample, Rf represents the electrical resistance of the sample in volume frac­tion Vf calculated from the approximation function Rf = f (Vf ), Vf represents the ratio between the in­trinsic volume of the sample V0 = m/d and volume occupied in the measuring cell, d represents the density of leather’s material, a represents the dis­tance between the measuring electrodes of the measuring cell, and b represents a power index cal­culated using the approximation of the set of resist­ances of the sample compressed in different volume fractions. The double in-situ polymerization of the pyrrole coating method was used to make the leather con­ductive. The leather samples were first cut into in 8 cm x 8 cm squares and treated with a mixed pyrrole/AQSA solution for one hour at room tem­perature, rotating manually at 10 rpm. A ferric chloride solution, which plays an oxidant role, was then added to the mixture to initiate the polymeri­zation, which was carried out for two hours at 5 °C, rotating manually at 10 rpm. The polypyrrole coat­ed leather samples were washed with distilled water and dried at 35 °C. The concentration of monomer (pyrrole), AQSA as a dopant and FeCl3 as an oxidant were varied and optimized to ensure the leather’s maximum conductivity. The sample was then treat­ed following the same procedure to obtain double in situ polypyrrole coated leather. In the end, the coated leather was washed four times with distilled water and dried at 35 °C. The colour of the sheep leather samples treated us­ing this method changed from white to black at the end of the experiments. 3 Results and discussion The samples’s electrical resistance compressed in different volume fractions (Vf ) was measured us­ing a Tektronix DMM4050 Multimeter. The voltage used was 10 V DC. For each sample, a set of electri­cal resistance results compressed by at least fifteen different volume fractions was used to calculate power index b of approximation power function of the form Rf = f (Vf-b) needed to calculate the resis­tivity .. Correlation coefficients R2 in each case were more than 0.95. Figure 2 illustrates a typical case of approximation. 1/Vf Figure 2: Typical curve of dependence between electrical resistance of the tested sample in . and inverse of volume fraction 1/Vf The mass of the sample used for these measurements was 4.54 g. The density of leather was 0.86 g/cm3, while intrinsic volume was V0 = 5.28 cm3. Each sam­ple was first tested in its initial square sheet shape (8 cm × 8 cm). It was then cut into thin strips and again tested for electrical resistance (Figure 1). We did this because our initial objective was to verify whether this method of measurement of resistivity, originally applied to textile fibres, could be success­fully applied to leather, as well. The samples were randomly placed in the measuring cell. In our previous research, [5] it was observed that the electrical resistivity of conductive leather, un­like the methods and standards used today for measuring surface resistance, was shown to be an inherent indicator of bulk conductivity of a leather assembly and was not influenced by sample shape or the way it is placed in the measuring cell. After proving the objectivity of the method, we decided to continue the measurements for near­ly one year to observe how the conductive leather will behave in natural environmental conditions. In this way, the tests were carried in natural weather conditions that included a wide range of humidity and air temperatures, using products made from this material. The objective of this research was to understand how the conductive leather applied in a smart product will react due to environmental con­ditions. Measurements of the sample’s resistivity in two different shapes and different environmental conditions are shown in Table 1. The results of resistivity were plotted versus relative the humidity and water vapor concentration of the air, as shown in Figures 3 and 4, respectively. Also, each figure contains two sets of data: curve 1 corre­sponds to the dependence of the sample’s resistivity in the shape of strips on the relative humidity and vapor concentration in the air. Curve 2 shows the above dependencies, but all results are considered, both for samples in the form of strips and sheets. As mentioned above, the preliminary objective of the actual study was to test the appropriateness of multiple-step method for measuring the resistivi­ty of leather and its sensitivity to the shape of the sample. This explains why we tested two shapes of the same sample, initially in the form of a sheet and later in the form of strips. A problem arose when comparing the results of the resistivity taken from tests performed on different days when air humidi­ty changed. The discrepancy of resistivity results in different temperatures and humidity raised doubts about the appropriateness of the method. The sam­ple in the shape of a sheet was tested during the summer when temperatures were higher, while tests of the sample in the shape of strips were performed mainly during winter when temperatures were low. The obvious difference between curve 1 and 2 in Figure 3 create the impression of the ambiguous in­fluence of the sample’s shape, air temperature and relative humidity. The correlation coefficient R2 was 0.21 for curve 1 and 0.14 for curve 2. The values are too low to consider them reliable. In Figure 4, curves 1 and 2 match each other. The correlation coefficient is as high as 0.87, which makes them reliable. We can conclude that the multiple-step method used to measure resistivity offers satisfactory results for testing leather electrical conductivity. Moreover, the leather’s resistivity depends on the water vapor concentration in the air but not on relative humid­ity. Consequently, there is no visible dependence of the resistivity of conductive leather on temperature. A change in the resistivity of conductive leather with water vapor concentration in the air follows the equation: ....=1.310!...."#.%& ..... (2) Table 1: Resistivity of the sample in two different shapes and in different environmental conditions Nr Shape Air temperature (°C) Relative humidity (%) Water vapor concentration (g/kg) Resistivity × 102 (.m) 1 strips 21.1 60 9.39 1.0846 2 strips 22.6 67 11.52 1.2421 3 strips 22.7 62 10.72 1.3104 4 strips 20.8 31 4.76 1.7104 5 strips 22.6 35 6.02 1.4418 6 strips 24.0 55 10.32 1.0846 7 strips 23.3 45 8.08 1.5174 8 strips 22.4 42 7.13 1.6218 9 strips 23.4 49 8.85 1.4693 10 strips 21.6 24 3.88 2.8489 11 strips 22.8 18 3.13 4.3787 12 strips 22.3 70 11.81 1.0599 13 strips 18.9 73 9.96 0.9529 14 strips 18.0 77 9.94 1.0194 15 strips 13.0 45 4.25 3.3581 16 strips 11.7 42 3.66 3.7270 16 strips 13.0 45 4.25 3.9341 18 strips 8.5 46 3.28 3.2578 19 strips 9.5 50 3.80 3.2091 20 strips 11.7 52 3.48 4.0133 21 strips 7.5 45 3.02 3.8110 22 strips 8.0 40 2.77 3.8150 23 strips 8.7 65 4.70 3.6590 24 strips 9.1 74 5.48 2.0040 25 strip 9.7 72 5.54 2.8300 26 sheet 24.2 55 10.45 1.5298 27 sheet 24.4 52 10.00 1.0922 28 sheet 25.0 45 8.98 1.1007 29 sheet 24.2 58 11.02 1.1714 30 sheet 25.1 62 12.46 0.9109 31 sheet 25.5 42 8.65 1.1321 32 sheet 24.9 58 11.51 0.6584 33 sheet 28.1 37 8.96 1.3086 34 sheet 27.4 43 9.97 1.0711 35 sheet 24.9 23 4.56 1.8825 corresponds to sets of data taken from samples in shape of both strips and sheets. Figure 4: Change in the resistivity of conductive leather with vapor concentration in the air H. Curve 1 corresponds to sets of data taken from the sample in the shape of strips alone, while curve 2 corresponds to sets of all data taken from samples in the shape of both strips and sheets. 4 Conclusion We can conclude that the multiple-step method for measuring resistivity offers satisfactory results for testing the electrical conductivity of leather. The conductive leather’s electroconductive properties were observed at different temperatures from 7.5 °C to 28.1 °C, relative humidity from 18% to 77% and water vapor concentration in the air from 2.77 g/kg to 12.46 g/kg, using the multiple-step method. The analyses of obtained data revealed that conductive leather’s electrical resistivity was a property with a strong dependence on environmental conditions, particularly on the air humidity. Resistivity de­creased with an increase in relative and absolute hu­midity. This study observed that the leather’s resis­tivity depends on the water vapor concentration in the air but not on relative humidity. Consequently, there was no visible dependence of the resistivity of conductive leather on temperature. This conclusion regarding the influence of environmental condi­tions on conductive leather can help researchers un­derstand where and how to apply conductive leather in different smart textile applications. References 1. HYLLI, M. Evaluation of extension set of dif­ferent Albanian leathers. Albanian Journal of Natural Technical Sciences, 2014, 21(1), 111-119, https://doczz.net/doc/3772801/ some-results-of-green-s-relations. 2. HYLLI, M., SHABANI, A., KAZANI, I., BEQIRAJ, E., DRUSHKU, S., GUXHO, G. Application of double in-situ polymeriza­tion for changing the leather properties. In Book of Proceedings of 8th International Textile Conference. Edited by I. Kazani. Tirana : Polytechnic University of Tirana, Faculty of Mechanical Engineering, 2018, 42-47. 3. WEGENE, J.D., THANIKAIVELAN, P. Conducting leathers for smart product appli­cations. Industrial & Engineering Chemistry Research, 2014, 53(47), 18209-18215, doi: 10.1021/ ie503956p. 4. HONG, K.H. Preparation of conductive leather gloves for operating capacitive touch screen dis­plays. Journal of the Korean Society for Clothing Industry, 2012, 14(6), 1018-1023, doi: 10.5805/ KSCI.2012.14.6.1018. 5. SHABANI, A., HYLLI, M., KAZANI, I., BERBERI, P.G. Measurement of resistivity of conductive leather using multiple step meth­od. In Book of Proceedings of 8th International Textile Conference. Edited by I. Kazani. Tirana : Polytechnic University of Tirana, Faculty of Mechanical Engineering, 2018, 120-125. 6. SHABANI, A., HYLLI, M., KAZANI, I., BERBERI, P., ZAVALANI, O., GUXHO, G. The anisotropic structure of electro conductive leath­er studied by Van der Pauw method. Textile & Leather Review, 2019, 2(3), 136-144, doi: 10.31881/ TLR.2019.16. 7. SHIN, J.E., HAN, S.S, CHOI, S.M. Fabrication of highly electrical synthetic leather with pol­yurethane/poly(3,4-ethylene dioxythiophene)/ poly(styrene sulfonate). The Journal of The Textile Institute, 2017, 109(2), 241-247, doi: 10.1080/00405000.2017.1337296. 8. YANG, C., WANG, J., LI, L. A novel approach for developing high thermal conductive artificial leather by utilizing smart electronic materials. Textile Research Journal, 2016, 87(7), 816-828, doi: 10.1177/0040517516641356. 9. BAO, Y., FENG, C., WANG, C., MA, J., TIAN, C. Hygienic, antibacterial, UV-shielding perfor­mance of polyacrylate/ZnO composite coatings on a leather matrix. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017, 51(C), 232-240, doi: 10.1016/j.colsurfa.2017.01.033. 10. SHABANI, A., HYLLI, M., KAZANI, I., BERBERI, P.G. Resistivity behavior of leather after electro-conductive treatment. Textile & Leather Review, 2019, 2(1), 15-22, doi: 10.31881/ TLR.2019.15. 11. BERBERI, P.G. Effect of processing on elec­trical resistivity of textile fibers. Journal of Electrostatics, 2001, 51-52, 538-544, doi: 10.1016/ S0304-3886(01)00112-7. 12. BERBERI, P.G. A new method for evaluat­ing electrical resistivity of textile assemblies. Textile Research Journal, 1998, 68(6), 407-412, doi:10.1177/004051759806800604. Tekstilec, 2021, Vol. 64(4), 305–316 | DOI: 10.14502/Tekstilec2021.64.305-316 Malek Alshukur1,2 1 Heriot-Watt University, School of Textiles and Design, Netherdale Road, Galashiels, TD1 3HF, UK 2 Faculty of Mechanical and Electrical Engineering, Department of Mechanical Engineering of Textiles Industries and their Technologies, Damascus University, Airport Road, Post Box 86, Damascus, Syria Effect of Spinning Triangle and Production Speed of Hollow-Spindle System on the Bouclé Yarn Structure Vpliv predilnega trikotnika in proizvodne hitrosti sistema z votlim vretenom na strukturo preje buklé Original scientific article/Izvirni znanstveni clanek Received/Prispelo 10-2020 • Accepted/Sprejeto 4-2021 Corresponding author/Korespondencni avtor: Malek Alshukur E-mail: malekshukur@yahoo.com ORCID ID: 0000-0002-4042-7311 Abstract This study aims to show the impact of both the width of the base of the spinning triangle and the production speeds of hollow-spindle spinning machines on the structure of ultimate multiple-thread-structure bouclé yarns and similar fancy yarns. A hollow-spindle spinning machine was used and bouclé yarns were made of a core thread, an effect thread and a (multifilament) binder. Initially, five bouclé yarns were made by setting the widths of the base of the spinning triangle at five levels, i.e. 4.5 mm, 7.5 mm, 10 mm, 13 mm and 16 mm. A further six bouclé yarns were made to show the changes that occur to the spinning triangle at various production speeds. The resulting fancy bouclé yarns were assessed by measuring the size, number and circularity ratio of bouclé profiles. It was found that at low production speeds, i.e. at start-up, that the spinning triangle was unstable, which adversely affected the structure of the final bouclé yarns. However, at production speeds higher than 17 m/min, the spinning triangle became stable, though such a stable spinning triangle had no impact on the structure of the resulting fancy bouclé yarns. The results of this study may help fancy yarn manufacturers to avoid making defective fancy yarns. Keywords: fancy yarn, bouclé yarn, spinning triangle, hollow-spindle machine Izvlecek Cilj te študije je bil ugotoviti, kako širina predilnega trikotnika in proizvodna hitrost predilnih strojev z votlim vretenom vplivata na strukturo vecnitne preje buklé in drugih efektnih prej. Za izdelavo preje buklé je bil uporabljen predilni stroj z votlim vretenom. Preja buklé je bila izdelana iz niti v jedru, efektne niti in multifilamentne povezovalne preje. Najprej je bilo izdelanih pet prej buklé z nastavitvijo širine osnove predilnega trikotnika na pet nivojev, tj. 4,5 mm, 7,5 mm, 10 mm, 13 mm in 16 mm. Nadaljnjih šest prej buklé je bilo izdelanih zato, da bi ugotovili, kakšne spremembe nastanejo na predilnem trikotniku pri razlicnih proizvodnih hitrostih. Kakovost izdelanih efektnih prej buklé je bila ocenjena glede na velikost, število in razmerja kroglastih profilov buklé. Pokazalo se je, da je pri nizkih proizvodnih hitrostih, tj. ob zagonu stroja, predilni trikotnik nestabilen, kar je negativno vplivalo na strukturo izdelane preje. Pri proizvodnih hitrostih nad 17 m/min je postal predilni trikotnik stabilen, vendar to ni vplivalo na strukturo nastale efektne preje buklé. Rezultati te študije lahko pomagajo predilcem, da se izognejo napakam pri izdelavi efektnih prej. Kljucne besede: efektna preja, preja bukle (bouclé), predilni trikotnik, stroj z votlim vretenom 1 Introduction 1.1 Spinning triangle of multiple-thread-structure fancy yarns on hollow spindle-spinning machines When using the hollow-spindle system to make fan­cy yarns by combining several (input) spun threads (or yarns), the final fancy yarn is said to have a multiple-thread structure. The spinning geometry of this final multiple-thread-structure fancy yarn forms part of the first spinning zone. This zone is located between the yarn supply rollers and the in­let mouth of the hollow-spindle [1, 2]. This zone is characterised by the formation of an approximate­ly right-angle spinning triangle and effect-thread helices. An example is provided in Figure 1 for the Gemmill & Dunsmore MK#3 hollow-spindle spin­ning machine. This machine can make the effect component of fancy yarns using either drafted fibres (i.e. slivers or rovings) or previously spun threads as the input materials. When using a spun thread for the effect component, a spinning triangle forms when the effect thread emerges from the supply roll­ers to the point where it starts making a helix around the core thread. The sides of such a spinning triangle were the segments of the core thread (one side of the triangle), the effect thread (hypotenuse of triangle) and the distance between the nipping points of the upper and lower supply rollers on these two threads (i.e. the base of the triangle). Observations indicated that changing the width of the base of such a trian­gle may alter the size of such a spinning triangle. It is easily possible to change such a width using the grooves of the control cylinder, which is located be­fore the upper supply roller (not shown in Figure 1). Several studies have been conducted on multi-ple-thread-structure fancy yarns made using the hollow-spindle system as shown below. 1.2 Literature survey The structure of multiple-thread fancy yarns made by either wrapping or twisting was studied using several approaches. These include the mathemati­cal modelling of the structure, the statistical or em­pirical modelling of the structural features of these yarns, technological studies of the parameters of the machines and their impact on the structure, engi­neering studies of the properties of the input yarns and their impact on the structure, engineering studies of the formation conditions of the structure and forces affecting the formation process, etc. In one analytical study based on mathematical equa­tions, the structure and formation of several types of multiple-thread-structure fancy yarns were mod-elled analytically [3]. In such a purely theoretical study, no practical results were presented to test the accuracy of the theoretical equations. Further, the fancy yarns described in such a study were made by twisting, not wrapping, and using routes and tech­nologies different from the hollow-spindle spinning system. When using the hollow-spindle spinning or hol­low-spindle twisting systems, the spinning geome­try was shown to have an impact on the structure of multiple-thread final fancy yarns. A recent ex­perimental investigation using the hollow-spindle system showed that the tension of the core thread can change the spinning geometry of fancy yarns [4], particularly within the first spinning zone. Consequently, it was used to regulate the style of the ultimate multiple-thread-structure fancy yarns by selecting suitable values for it. The practical bene­fit of such a study is that it showed it was possible to make good-quality multiple-thread-structure fancy bouclé yarns using a differential overfeed ratio of as low as +50% of only one effect thread in comparison with the core thread [4]. Following this, two other studies were also conducted to provide a deeper understanding of the formation of the ef-fect-thread helices within the first spinning zone of hollow-spindle spinning machines [1, 2]. In these two studies, it was shown that the shape and size of the effect-thread helices can change the structure of the ultimate multiple-thread-structure fancy yarns. These two studies also showed that the spinning ge­ometry was also controlled by several factors, such as the overfeed ratio of the effect thread, the weight and stiffness of input effect thread and the dynam­ic forces affecting the segment of the effect thread within the first spinning zone [1, 2]. Dynamically, the diameter of the helices is controlled by external forces, such gravitational force, air drag, centrifu­gal force and centripetal force. It is also controlled by internal forces, such as tension and the bending force of the effect thread [1]. Mathematically, it was shown that the overfeed ratio and the number of helices can define the radius of the helices in the steady-state rotation or configuration of the ef-fect-thread helices [2]. In another study, a universal, analytical model of the structure and geometry of several types of mul­tiple-thread-structure fancy yarns was presented [5]. In other studies, another form of mathematical modelling of the geometry of bouclé yarns was used to build a mathematical model of the strength of such types of fancy yarn. In the same study, how­ever, the structure was called loop yarn when the structural profiles were sinusoidal in shape, though these were similar to any typical bouclé yarn struc­tural profiles [6, 7]. In another study, the Structural ratio of multi-thread fancy yarn was presented using a simple mathematical equation to account for the interaction of the number of wraps and the overfeed ratio, and to show how such an interaction may help in deciding the structure and type of fancy yarn [8]. Depending on the value of this ratio, the final fancy yarn can be bouclé yarns, gimp yarns, overfed fancy yarns or wavy yarns. Other studies concerned the contribution of tech­nological factors of the hollow-spindle system to the structure of multiple-thread fancy yarns. Examples of these studies are those that dealt with the impact of the supply speed of the effect thread, the rotational speed of the hollow-spindle and the delivery speed of the ultimate fancy yarns [9-14]. These studies were based on the design of experi­ment method using either the Box-Behnken design or second-order composite models. The differ­ences between these studies lie in the type of ma­terial used and types of fancy profile that resulted [9-14]. The researchers studied these overfed fancy yarns in terms of linear density, breaking tenacity, height of the effect projections, width of the effect projections, distance between the effect projections and the number of effect projects per unit length. In these studies, the effect threads that were stud­ied were loop/knot and plain knot, plain knot-knot effect profiles, closed loop, opened loop, loop-knot, opened loop-plain knots, knot made from various loops and combinations thereof [9-14]. The impact of other factors was also reported, including the bending stiffness of effect threads [15, 16], the com­bined effect of the overfeed ratio and the number of wraps [8] and false twist [17]. Other forms of investigation were also based on the design of experiment method using factorial designs [18-21]. The multiple-thread-structure fan­cy yarns were gimp fancy yarns, derivatives there­of and generic overfed fancy yarns. The properties studied were the linear density of ultimate fancy yarns [18], their aesthetics and structural properties [19] and their tensile properties [20, 21]. This group of technological factors included the supply speed of effect thread, the delivery speed of ultimate fan­cy yarn, the rotational speed of the hollow spindle, the use of false-twist, the nature of the effect com­ponent (i.e. number of threads, linear density, type of spinning method and any special treatments), the nature of the core component and the nature of the (multifilament) binder. Significant results were ob­tained, as summarised in Table 1 [18-21]. Using the combined hollow-spindle system and ring-spindle system in one machine, two similar studies were conducted on multiple-thread-struc­ture bouclé yarns and fancy knitted fabrics made from them [22, 23]. The factors of these two stud­ies were the overfeed ratio of the effect thread, the number of wraps of the binder and the direction of wraps. The bouclé yarns were assessed by counting the number of bouclé profiles per unit length and by measuring their height. The fancy knitted fabrics made of these bouclé yarns were studied in terms of areal density, fabric thickness and abrasion re­sistance. The knitted fabrics were single jersey and (1×1) rib in the first study [22], and 2×1 and 2×2 rib fabrics in the second study [23]. The overfeed ratio had two levels, i.e. 100% and 200%, while the number of wraps had three levels, i.e. 400, 450 and Table 1: Summary of results reported on multiple-thread-structure fancy gimp yarns using a fractional factorial design Factor and levels Advantages gimp yarn structure Disadvantages to gimp yarn structure Core component: two single threads versus a single thread Thicker gimp yarns; higher value of the maximum load and load at the first peak; better extension at the first peak; higher number of the core ruptures; lower number of irregular non-gimp fancy projections with smaller sizes Not applicable Binder component: heavy textured multifilament versus lighter non-textured multifilament Higher values for load at the first peak and extension at the first peak, lower number of non-gimp profiles with smaller sizes Lower number of core ruptures Effect component: heavy and stiff bamboo yarn versus lighter, softer cotton yarn Thicker gimp yarns; higher value of load at the first peak; smaller number of non-gimp profiles with smaller sizes; and higher number of core ruptures Lower value of the maximum load; less extension at the first peak Supply speed: high versus low Thicker gimp yarns Not applicable Rotational speed: high versus low Reduced number of non-gimp profiles by increasing the number of wraps; slightly increase in the number of core ruptures Not applicable Delivery speed: high versus low Not applicable Thinner gimp yarns False-twist: using versus not using it Not applicable Slight increases in the number of non-gimp profiles Number of wraps: high versus low Increase in the number of core breaks; reduced number of non-gimp profiles by increasing the rotations of the spindle Decrease in the maximum load; slight increases in the size of abnormal distortions Overfeed ratio: high versus low Increase in the number of the core ruptures Reduced number of core breaks; increases in the number of non-gimp profiles and their average size 500 wraps per metre. All these factors were found to have an influence on the results, but clear inter­action plots for the effect of these factors were not provided and the experimental design was not a standard experimental design for either of the two studies [22, 23]. The spinning triangle was not studied in any of these published studies. However, since the spin­ning triangle on traditional ring spinning machines is important to the structure of typical spun yarns and controlling its dimensions has led to the in­vention of compact ring spinning, a similar inves­tigation is required for the spinning triangle on the hollow-spindle system. Such an investigation may be completed in two cases. In the first case, which is beyond the scope of this study, the effect element of fancy yarns should be made by spinning draft­ed fibres, i.e. sliver or roving. In the second case, the effect element of fancy yarns is made by com­bining previously made yarns. In this second case, since the spinning triangle forms part of the first spinning zone, studying it may help increase cur­rent knowledge of the spinning geometry of this category of fancy yarns. Based on all of that, this study was conducted to complete the experimen­tal investigations that were reported for the most part in three studies [1, 2, 4]. The topic of this study was the distance between the core thread and the effect thread at the beginning of the first spinning zone, also known as the width of the base of the spinning triangle. Further, since the motion of the effect thread changes at different levels of produc­tion speeds, in particular at the start-up of the hol­low-spindle machines or at low production speeds, the spinning triangle may change. Therefore, the impact of running the hollow-spindle system at dif­ferent levels of production speed on the structure of the ultimate fancy yarns was also studied. 2 Experimental For this investigation, two experiments were con­ducted, and the ultimate fancy yarns were made by combining only three input yarns. This num­ber of input threads was suitable for this kind of investigation, though fancy yarn can be made from more input threads. In the first experiment, five fancy bouclé yarns were made (i.e. group I of fancy bouclé yarns). The input effect component was a 67 tex wool thread and the input core com­ponent was a three-ply cotton thread (R72/3 tex), while the binder (or wrapper) was a nylon multi-filament (R14.5/77 tex). The multiple-thread bou­clé yarns were made on a Gemmill & Dunsmore (G&D) MK#3 hollow-spindle spinning machine. The supply speed of the machine was 54 m/min, the delivery speed was 30 m/min and the rota­tional speed of the hollow-spindle was 5700 rev­olutions per minute. Subsequently, the number of wraps was W = 5700 ÷ 30=190 wraps per metre, while the theoretical overfeed ratio was . = (54 ÷ 30) ×100 = 180%, i.e. the differential overfeed ratio is +80%. These values of machine speeds ensured that the spinning triangle was stable, while the ef­fect thread helices were also stable. The tension of the core thread while running the machine was ap­proximately zero in accordance with the results of a previous study [4]. The width of base of the spin­ning triangle was set to 4.5, 7.5, 10, 13 and 16 mm, one at a time, according to the machine design and limited by the width of the upper (rubber) supply roller. Due to the variability of the manufacturing process itself, the vibration of the machine parts and the variation in linear density of the core and effect threads, the aforementioned values for the base width changed continuously within a ± 0.5 mm range. The false-twist hook was used in this experiment, while its influence on the structure was revealed in a previous work [17]. False-twist may result in a transient impact on the structure at the start-up of the machine if drafted fibres are used, but this is not the case when using yarns as input materials due to differences in number, size and mass of the input threads in comparison with loose fibres. Since the formation of a stable spinning triangle is related to the levels of production speeds, a further experiment (Experiment II) was conducted to as­sess the impact of production speed on the fancy bouclé yarn structure. This experiment may com­plement a previous investigation on the effect of the production speed of hollow-spindle machines on the structure of bouclé yarns that have the effect component made from drafted fibres [24]. In one case of Experiment II, the spinning triangle was made unstable by running the machine at a low production speed. This is similar to the case of a machine starting-up or changing speeds when the machine is already running at a suitable production speed. Six new bouclé yarns were made (i.e. called group II of fancy bouclé yarns) for Experiment II. The core component was an R120/2 tex lambswool/ viscose blended spun yarn. The effect component was an R120/2 tex lambswool/cashmere blended spun yarn. The false-twist hook was used in the Experiment II. The full settings of the machine are given in Table 2. Table 2: Machine settings and structural parameters of bouclé yarns for Experiment II Fancy yarn Delivery speed (m/min) Supply speed (m/min) Rotational speed (min-1) Overfeed ratio, . (%) Number of wraps (m-1) Yarn II (1) 17 34 3400 200 200 Yarn II (2) 24 48 4800 Yarn II (3) 28 56 5600 Yarn II (4) 32 64 6400 Yarn II (5) 34 68 6800 Yarn II (6) 36 72 7200 The ultimate multiple-thread structure fancy yarns were first preconditioned and then conditioned ac­cording to BSI ISO Standard 139:2005. They were then assessed according to the parameters and pro­cedures given in previous studies for the objective assessment of such unique yarns [25, 26]. These parameters include the size of fancy profile, the number of fancy profiles and the circularity ratio of fancy profile. The size of fancy profile refers to the average area of an ultimate, fitted polygon drawn to match the circumference of the 2D projection of the fancy profile on a plane (if it is seen under a microscope). The number of fancy profiles refers to the number of the main fancy profiles of the effect component in a unit length (usually one meter) of the fancy yarn. The circularity ratio of fancy pro­file is a term that describes the circularity or the roundness of the representative projection of fancy profile on a plane. Fifteen specimens were sampled systematically to count the number of fancy bouclé (including semi-bouclé) profiles per dm. The sam­pling distance for this procedure was two metres. A manual winding reel (supplied by Doodbrand & Co. Ltd., England) was used to prepare the yarns for this purpose. A further fifteen specimens were also sampled systematically to measure the size (or area) and the circularity ratio of the fancy bouclé profiles. For these last two parameters, the sampling distance between each two bouclé profiles selected was 60 cm. The selected fifteen bouclé profiles were prepared before taking a digital image of each of them. The preparation was accomplished by plac­ing the selected profiles, one at a time, underneath a suitable transparent plate made from glass. Doing so ensured that the fancy profiles lay in a plane if they were not already so. The plate and profile un­derneath it were all placed under a microscope with Table 3: Numerical results of Experiment I a magnifying power of 4×. The microscope was con­nected to an Olympus digital camera. Following this, a digital photo was taken of each fancy profile. A digital image analysis software package called ‘analySIS FIVE®’ was used to draw an ultimate, fit­ted polygon around the projection of fancy profile when viewed from above. This digital image anal­ysis software was used to analyse the images and to measure both the size and the circularity ratio of the profile. 3 Results and discussion The yarns made for the first experiment are shown in Figure 2. The fancy profiles that are marked with green colour were profiles that were selected to measure their size (mm) and circularity ratio (%). Subjectively, one may say that these bouclé yarns were similar in structure because they all had sim­ilar bouclé profiles and regular sigmoidal segments. These observations were confirmed objective­ly by the results of numerical testing procedures, as shown in Table 3. According to the p-values of ANOVA testing, no statistical differences were found amongst the yarns in terms of the size, the number and the circularity ratio of profiles. This means that the width of a stable spinning triangle had no effect on the structure of multiple-thread bouclé yarns. The similarities in the number, size and the circularity ratio of the fancy bouclé pro­files mean that the effect-thread helices in the first spinning zone were similar in number and diameter [1, 2]. This also indicates that the influential factors controlling the diameter of effect-thread helices, as given previously [1, 2], exceeded any impact of the width of the spinning triangle base. Bouclé yarn Width of spinning triangle (mm) Size of bouclé profile (mm2) Number of bouclé profile (dm-1) Circularity ratio of bouclé profile (%) Average SD a) Average SD a) Average SD a) Yarn I (1) 4. 5 13.39 3.80 7.3 0.90 57 17 Yarn I (2) 7.5 14.65 4.19 7.2 1.20 53 17 Yarn I (3) 10 12.85 6.72 7.8 1.60 55 20 Yarn I (4) 13 13.59 4.15 7.3 0.90 56 18 Yarn I (5) 16 14.40 6.59 6.5 1.40 56 18 a) Standard deviation Yarn I (1) Yarn I (2) Yarn I (3) Yarn I (4) Yarn I (5) Figure 2: Images of the bouclé yarns made for Experiment I The yarns made for Experiment II are shown in configuration of these profiles, it is necessary to rely Figure 3, while the results of the numerical testing on numerical values for the size of the profiles. Table of these yarns are given in Table 4. Subjectively, 4, and Figures 4 and 5 all indicate that the use of low one may say that the first of these yarns had a low-speeds on the machine resulted in the final bouclé er number of bouclé profiles in comparison with yarn II (1) being different from those made at high-the rest of the yarns. Additionally, the other yarns er speeds. The main difference was that profound-do not appear to differ profoundly in terms of the ly larger and less bouclé profiles were obtained. number of bouclé profiles. However, due to the 3D Figure 4 and Figure 5 also have two regions, with an approximately stable region starting from a delivery speed of 24 m min-1. This region is characterised by approximately similar profiles within an acceptable level of variation that is typical for fancy yarns. This region is preceded by an initial region that has fancy bouclé yarns different in terms of size and number from the profiles of the second stable regions. Dynamically, the effect thread segment within the spinning triangle is subjected to internal and ex­ternal forces. The main internal forces are bending force and tension. The tension may initially have negative values, i.e. compression, at the start-up of the machine because the effect thread is forced forward by the supply rollers. However, once the Yarn II (3) Yarn II (4) Yarn II (5) Yarn II (6) Figure 3: Images of bouclé yarns made for Experiment II Table 4: Numerical results of Experiment II Fancy yarn Delivery speed (m/min) Size of bouclé profile (mm2) Number of bouclé profiles (1/dm) Average SD a) Average SD a) Yarn II (1) 17 23.11 9.56 9.46 1.59 Yarn II (2) 24 18.45 5.73 11.87 2.50 Yarn II (3) 28 19.00 6.61 12.53 3.182 Yarn II (4) 32 20.89 6.19 12.67 2.28 Yarn II (5) 34 19.34 9.69 11.67 1.72 Yarn II (6) 36 19.90 6.66 12.53 3.638 a) Standard deviation Figure 4: Relationship between the speeds of the hollow-spindle machine and the size of bouclé profiles Figure 5: Relationship between the speeds of the hollow-spindle machine and the number of bouclé profiles rotational speed and thus centrifugal and centrip­etal forces increase, a positive value of the tension will control the effect thread segment in all loca­tions of the first spinning zone, including the spin­ning triangle. The main external forces in the spin­ning triangle are air drag and gravitational force. At the start-up of the machine, gravitational force (G) will be the dominating external force, and the effect-thread segments may fall downwards. As all speeds of the machine increase, air drag appears and comes into effect. Once the rotational speed reaches a specific limit, the effect thread segment starts to rotate around the core thread segment. The result of this is that a new force, called centripetal force, starts to appear and is directed outward from the centre of rotation, while centrifugal force acts in the opposite direction. Starting from this limit, the impact of air drag remains constant, and as such, it may not create substantial changes to the shape of the spinning triangle. Gravitational force is greater than centripetal force (F) at the start-up of the machine. This is confirmed c by the following calculations based on an infinitesi­mally small segment dl of the effect thread that has a linear mass m. This yarn segment is subjected to a gravitational force of dG = mgdl, where g represents the gravitational acceleration, g = 9806.65 mm/s2. Due to rotation, this yarn segment is also subjected to centripetal force dF=mr.2dl, where . represents c angular velocity (measured in radians per second) and r represents the radius of the rotation of this yarn segment. Centripetal force must be greater than gravitational force for a fancy yarn to form, i.e.dF > dG or mr.2dl > mgdl; thus r.2 > g. Since c . = 2pRS, where RS represents rotational speed, therefore (2pRS)2 > g, or: ........>$60g (1) 2p.... where the number 60 is used to convert time from seconds into minutes for the revolutions. At the start-up of the machine, the radius of rota­tion r may be equal to the base of the spinning tri­angle. When r = 4.5 mm, which is the setting used for the first setting of Experiment I, then RS must be > 144 revolution per minute for centripetal force to be greater than gravitational force. Once cen­tripetal force increases, air drag comes into effect. Thus, higher values of centripetal force are required to exceed such a drag. As centripetal force and cen­trifugal force increase in magnitude, they reach a point where they become the dominating forces and they balance out all other forces. Subsequently, both the spinning triangle and the helical config­uration of the effect thread reach the steady-state case. Eventually, a stable spinning triangle followed by stable effect-thread helices are formed, and the spinning triangle smoothly merges with the top of the effect-thread helical configuration. Since stable, similar helices are formed, regardless of the length of the hypotenuse of the spinning tri­angle, no changes will occur to their diameter or number within the first spinning zone. This means that the use of the overfeed ratio as a main element in Equation 5 in a previous study [2] remains valid. This Equation is reproduced here as follow: ....! ....= '...."-1 (2) 2........ where r represents the radius of helices, n repre­sents their number within the first spinning zone, . represents the theoretical overfeed ratio of the ef­fect thread and Lc represents the length of the core thread within the first spinning zone (which ap­proximately equals the length of the first spinning zone). It is thought that changes in the length of such a hypotenuse, when changing the width of the base, happen mainly at the start-up of the machine and also when changing the speeds of the machine. The case of machine start-up is also similar to the case of running the machine at low speeds. During the start-up time, once the machine reaches the set values of rotational, supply and delivery speeds, the hypotenuse will also be stable for the specific overfeed ratio used. The set values of speeds must be above a certain level to ensure the stability and regularity of both the spinning triangle and the ef­fect thread helices. These results were explained dy­namically above. The result of Experiment II indicate that the spin­ning triangle was not stable at low production speed, but rather was irregular. This is because of gravity and air drag. These reasons concur with a previous investigation regarding effect-thread hel­ices at low machine speeds, in particular the rota­tional speed [1, 2]. In some cases where the speeds of the machine are extremely low, the machine fails to make a spinning triangle or effect-thread helices. Consequently, it fails to make multi­ple-thread-structure fancy bouclé yarns. Due to the similarities in structure with other fancy yarns as described mathematically in one universal geomet­rical model [5], similar results may be obtained for overfed fancy yarns such as gimp fancy yarns, wavy fancy yarns, generic overfed fancy yarns and all their derivatives. 4 Conclusion It was concluded that the width of the base of the spinning triangle of hollow-spindle spinning ma­chines had a profound influence on the structure of multi-thread fancy bouclé yarns when such ma­chines run at low production speeds, i.e. = 17 m/min. At these low production speeds, the spinning trian­gle was unstable. The resulting fancy bouclé yarns thus had an unacceptably low number of profound­ly large bouclé profiles, which adversely affected their quality and commercial value. This problem was solved by increasing the production speed to a higher value, i.e. = 24 m/min. At these higher pro­duction speeds, the stability of the spinning triangle was improved. This helped in regulating the struc­ture, morphology and style of the resultant mul-ti-thread fancy bouclé yarns. Similar results may be obtained for similar multiple-thread-structure fancy yarns, such as gimp fancy yarns, wavy fancy yarns, generic overfed fancy yarns and all their de­rivatives. The results of this research can help fancy yarn manufacturers to improve the quality of their yarns and also to avoid the aforementioned unfa­vourable situations, thus saving them money, effort and time. References 1. ALSHUKUR, Malek, YURCHENKO, Daniil. Experimental study on the spinning geometry of multi-thread fancy yarn on hollow-spindle spinning machines: Part II. International Journal of Clothing Science and Technology, 2019, 31(4), 454–461, doi: 10.1108/IJCST-05-2017-0065. 2. ALSHUKUR, Malek, YURCHENKO, Daniil. Experimental study on the spinning geometry of multi-thread fancy yarn on hollow-spindle spinning machines: Part I. International Journal of Clothing Science and Technology, 2018, 30(4), 496–506, doi: 10.1108/IJCST-05-2017-0064. 3. MARTON, Erich, Theoretical principles of fancy yarn twisting. Melliand Textilberichte [Eng. Ed.], 1987, 68(8), E 242–243. 4. ALSHUKUR, Malek, SUN, Danmei. Effect of core thread tension on structure and quality of multi-thread bouclé yarn. Indian Journal of Fibre & Textile Research, 2016, 41(4), 367–372, http://op. niscair.res.in/index.php/IJFTR/article/view/8176. 5. ALSHUKUR, Malek, GONG, Hugh, STYLIOS, George. Structural Modelling of multi-thread fancy yarn. International Journal of Clothing Science and Technology, 2018, 30(2), 268–283, doi: 10.1108/IJCST-05-2017-0063. 6. GRABOWSKA, Katarynza Ewa. Mathematical modeling of tensile properties of fancy loop yarns. Theoretical: Part I. Textile Research Journal, 2010, 80(18), 1905 –1916, doi: 10.1177/0040517510369405. 7. GRABOWSKA, Katarynza Ewa. Experimental analysis of the tensile properties of fan­cy loop yarns. Part II. Textile Research Journal, 2010, 80 (18), 1917–1929, doi: 10.1177/0040517510369406. 8. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Structural ratio of multi-thread fancy yarn: in­teraction effect of both the number of wraps and the overfeed ratio on fancy bouclé yarn structure. Journal of Natural Fibers, 2021, 18(11), 1570-1579, doi: 10.1080/15440478.2019.1692320. 9. PETRULYTE, Salvinija, PETRULIS, Donatas. Influence of twisting on linen fancy yarn struc­ture. Journal of Natural Fibers, 2014, 11(1), 74–86, doi: 10.1080/15440478.2013.842512. 10. RAGAIŠIENE, Audrone. Interrelation between the geometrical and structural indices of fan­cy yarns and their overfeed and twist. Fibres & Textiles in Eastern Europe, 2009, 17(4)/76(5), 26–30, http://fibtex.lodz.pl/article265.html. 11. RAGAIŠIENE, Audrone. Influence of overfeed and twist on fancy yarns structure. Materials Science, 2009, 15(2), 178–182, https://www.matsc. ktu.lt/index.php/MatSc/article/view/26142. 12. PETRULYTE, Salvinija. Influence of technolog­ical parameters on the periodical effects of fancy yarns. Fibres & Textiles in Eastern Europe, 2008, 16(3)/68(3), 25–29, http://fibtex.lodz.pl/article163. html. 13. PETRULYTE, Salvinija. Analysis of structural effects formation in fancy yarn. Indian Journal of Fibre & Textile Research, 2007, 32(1), 21–26, http://hdl.handle.net/123456789/399. 14. RAGAIŠIENE, Audrone, PETRULYTE, Salvinija. Design of fancy yarns with worsted and elasto­meric covered components. Materials Science, 2003, 9(4), 414–418, https://matsc.ktu.lt/index. php/MatSc/article/view/26751. 15. ALSHUKUR, Malek, FOTHERINGHAM, Alex, GONG, Hugh. Influence of component stiffness on the structure of multi-thread, fancy bouclé yarn. Journal of Industrial Textiles, 2020, 49(7), 889–905, doi: 10.1177/1528083718801365. 16. ALSHUKUR, Malek, FOTHERINGHAM, Alex, GONG, Hugh. Relationship between the interac­tion of bending stiffness of component yarns and the structure of fancy bouclé and semi-bouclé yarns. Fibers and Polymers, 2020, 21(2), 437–446, doi: 10.1007/s12221-020-8156-0. 17. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Role of false twist in the manufactur­ing process of multi-thread fancy yarn on hol­low spindle spinning machines. The Journal of The Textile Institute, 2014, 105(1), 42–51, doi: 10.1080/00405000.2013.810367. 18. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Studying the linear density of multi-thread fancy yarn made from natural fibers using the design of experiments. Journal of Natural Fibers, 2018, 15(5), 658–667, doi: 10.1080/15440478.2017.1354741. 19. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Quality and structural properties of gimp fan­cy yarns using the design of experiments. The Journal of The Textile Institute, 2015, 106(5), 490–502, doi: 10.1080/00405000.2014.927126. 20. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Studying the tensile properties at the first break of multi-thread fancy gimp yarns using the design of experiments. Journal of Natural Fibers, 2020, 17(5), 716–725, doi: 10.1080/15440478.2018.1527741. 21. ALSHUKUR, Malek, FOTHERINGHAM, Alex. Study of maximum tensile strength of fancy yarns using the design of experiments. Mechanics & Industry, 2019, 20(4), 403–412, doi: 10.1051/ meca/2019033. 22. NERGIS, Banu Uygun, CANDAN, Cevza. Performance of bouclé yarns in various knitted fabric structures. Textile Research Journal, 2006, 76(1), 49–56, doi: 10.1177/0040517506059210. 23. NERGIS, Banu Uygun, CANDAN, Cevza. Performance of rib structures from boucle yarns. Fibres & Textiles in Eastern Europe, 2007, 15(2)/61(2), 50–53, http://fibtex.lodz.pl/arti­cle1058.html. 24. BAOYU, Zhu, OXENHAM, William. Influence of production speed on the charac­teristics of hollow spindle fancy yarns. Textile Research Journal, 1994, 64(7), 380–387, doi: 10.1177/004051759406400703. 25. ALSHUKUR, Malek. The quality of fancy yarn: Part I: methods and concepts. International Journal of Textile and Fashion Technology, 2013, 3(1), 11–24, http://www.tjprc.org/publishpa­pers/2-29-1517224853-2.IJTFTMAR201302.pdf. 26. ALSHUKUR, Malek. The quality of fancy yarn: Part II: practical experiments and application. International Journal of Textile and Fashion Technology, 2013, 3(1), 25–38, doi: 10.24247/ ijtftmar201303. Tekstilec, 2021, Vol. 64(4), 317–324 | DOI: 10.14502/Tekstilec2021.64.317-324 Tetiana Ielina1, Liudmyla Halavska1, Nataliia Ausheva2 1 Kyiv National University of Technologies and Design, Nemyrovych-Danchenko str. 2, Kyiv, Ukraine 2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Ukraine Macro-Modelling of Rib-Knitted Tubular Parts Makromodeliranje rebrasto pletenih cevastih sestavnih delov Original scientific article/Izvirni znanstveni clanek Received/Prispelo 2-2021 • Accepted/Sprejeto 4-2021 Corresponding author/Korespondencna avtorica: Tetiana Ielina Phone: +38 0965403835 E-mail: yelina.tv@knutd.com.ua ORCID ID: 0000-0002-9310-0582 Abstract The aim of the research was to improve the process of knitted products design. The use of modern software helps us predict the physical and mechanical behaviour of materials, using their three-dimensional models. A macro-model of rib-knitted tubular parts was developed in the study. This model allows its implementation into algorithms, describing the peculiarities of the stretching process. Recent findings in the field of 3D modelling and simulation of knitwear behaviour aim at working with models of different scales of structural hierarchy. The use of macro-models provides the opportunity to simplify the geometry and significantly reduce the time required for simulation. Rib stitch structures are among the most popular weft-knitted ones. When using threads of usual stretchability (with breaking elongation that does not exceed 10–12%), the stretchability of some rib stitch structures in the course-wise direction can reach up to 350% and even more. When stretched in the course direction, rib-knitted stitches undergo a number of stages. The stretching process includes: decreasing the width-wise curling; mutual shifting of knit and purl stitches; reducing the curvature of the loop feet and loop heads; pulling the yarn from the loop legs to the loop feet; stretching of the yarn. The assumption was made that such parts of knitted garments as cuffs and borders on sweaters, cuffs on socks, where rib stitch patterns are used, can be described as thin-walled elastic shells. A part of a human body surface, covered with a rib-knitted garment part, can be approximated by a truncated cone. The mid-surface of the shell can be represented as a ruled surface created upon a set of Bezier curves, located along the circumference of the upper and lower bases of the truncated cone. The mathematical description, elaborated in the course of the research, was used for the computer program LastikTube, which was developed to create 3D macro-models of ribbed tubular garments. Keywords: Rib stitch structures, macro-models, sock cuff, 3D modelling Izvlecek Cilj raziskave je bil izboljšati proces oblikovanja pletenih izdelkov. Sodobna programska oprema nam z uporabo tridi­menzionalnih modelov materialov pomaga predvideti njihovo fizikalno in mehansko obnašanje. V študiji je bil razvit makromodel rebrasto pletenih cevastih sestavnih delov. Model omogoca izpeljavo v algoritme, ki opisujejo posebnosti raztezanja. Najnovejša spoznanja na podrocju 3-D modeliranja in simulacije obnašanja pletenin so namenjena delu z modeli na razlicnih ravneh strukturne hierarhije. Uporaba makromodelov omogoca poenostavitev geometrije in znatno skrajšanje casa, potrebnega za simulacijo. Rebraste strukture so med najbolj priljubljenimi votkovnimi pletivi. Pri uporabi niti obicajne raztegljivosti (s pretržnim raztezkom pod 10–12 %) lahko raztegljivost nekaterih rebrastih struktur v smeri zancnih vrst seže do 350 % in celo vec. Pri raztezanju v smeri zancnih vrst gredo rebrasta pletiva skozi vec faz. Raztezanje zajema: zmanjšanje vihanja po širini; vzajemno premikanje levih in desnih zank; zmanjšanje ukrivljenosti igelnih in platinskih glav zank; odvzemanje preje od krakov zanke k platinski glavi zanke in raztezanje preje. Domnevali smo, da lahko dele pletenih oblacil, kot so rokavne in pasne obrobe na puloverjih in robovi nogavic, kjer so uporabljene rebraste pletene strukture, opišemo kot tankostenske elasticne lupine. Del površine cloveškega telesa, ki je prekrit z reb­rasto pletenim delom oblacila, lahko poenostavljeno prikažemo kot prisekani stožec. Sredinsko površino lupine lahko predstavimo kot ravno površino, ustvarjeno s pomocjo niza Bezierovih krivulj, ki se nahajajo vzdolž oboda zgornje in spodnje osnovne linije prisekanega stožca. Matematicni opis, izdelan med raziskavo, je bil uporabljen za racunalniški program LastikTube, ki je bil razvit za izdelavo 3-D makromodelov rebrastih cevastih oblacil. Kljucne besede: rebrasta pletena struktura, makromodeli, rob nogavice, 3-D modeliranje 1 Introduction The challenge of designing knitwear with predicted properties is widely discussed in the scientific com­munity. Evidently, the demands for the quality and comfort of clothing are constantly rising. Some of the most important properties of apparel that affect the level of human comfort in the process of wear­ing clothes are air permeability, hygroscopicity and tactile comfort. This idea has been confirmed in various studies [1–4]. Other papers [5–7] focus on the pressure clothes exert on a human body and the conditions of maintaining their comfort when us­ing them. Research [8–10] addresses the issue of de­signing various knitted structures by means of yarn level modelling. It provides high accuracy of yarn geometry, but significantly increases the time re­quired for calculus [11, 12]. Depending on the algo­rithms and the purpose of physical process model-ling, knitwear can be represented as an orthotropic shell of certain thickness, with specified parame­ters of elasticity, hygroscopicity, heat conductivity, stiffness etc. In a ready-made product, the level of indicators that affect the comfort of clothes in the process of wearing is predominantly determined by the properties of raw materials they are made of and their knitted structure. Furthermore, the latter is predetermined by the design of the product and the compliance of its size with body measurements. Circumference measurements depend on the posi­tion of a human body and the dynamics of its move­ments [13]. When used, the knitted garment is in a deformed state (especially if the clothing is tight fitted). Thus, the indicators of the above-mentioned properties differ significantly from the ones that re­fer to not deformed ones. The issues of knitted fab­ric deformation mechanism and fabric deformation modelling by means of computer tools were studied [14–19]. One of the most popular weft-knitted structures is a rib structure which provides high elasticity without creating any excessive compression. The surface of rib stitch structures possesses certain peculiarities and requires using special algorithms for the crea­tion of macro-models of some parts of knitted prod­ucts comprising rib structures. 2 Methodology Within the apparel modelling system, the scale of modelling and corresponding fabric structure ide­alisation depends on the purpose of its design and input data availability as well as software and hard­ware tools. It is important to choose appropriate assumptions and idealisations, as well as numerical homogenisation methods. Within the systems of three-dimensional modelling and simulation, knit­wear can be represented as an orthotropic textile shell with given thickness. In this case, the product, e.g. a sock, can be presented in the shape of a 3D model as shown in Figure 1. The basic knitted structure element is a loop inter­meshed with the loops of the previous and subse­quent courses. Furthermore, in the case of 2 × 2, 3 × 3, 4 × 4 and other rib stitch patterns, adjacent knit and purl stitches of the same course can change their mutual position; plain columns width-wise curling can exist as well. As for mechanical char­acteristics, it is necessary to mention that, depend­ing on the rib stitch pattern and yarn properties, rib stitch structures can have variable levels of stretch­ability. To represent the physical and mechanical properties of rib stitch structures in macro-models more precisely and to design the mid-surface of tu­bular rib-knitted shells, the mathematical tool of Bezier curves and ruled surfaces can be used. 2.1 Rib stitch course-wise cross-section The study of geometric transformations that occur in the process of course-wise stretching of rib-knit­ted structures [20–22] proved that the change in the configuration and position of separate elements within such a structure is irregular. In the course of stretching, some different processes occur: de­creasing of width-wise curling, mutual shifting of adjacent knit and purl stitches, reduction of the cur­vature of the loop feet and loop heads, pulling the yarn from the loop legs to the loop feet, stretching of the yarn. To study the nature of a thread redis­tribution within the structure of knitwear, the au­thors of papers [20–22] used the following notions: the ribbing pattern unit width in mm (Wru), the width of the projection of a convex part of a rib stitch pattern on the fabric plane (C) and the width of the projection of a visible segment of its concave part on the fabric plane (S), as shown in Figure 2. If we divide the process of stretching of knitwear in the course-wise direction into n discrete states Tm, where m is the number of a given state, we can say that 0 = m = f, where 0 is the index of a free state particular to a knitted fabric before applying tensile forces and f is the index of the state of maximum tension that is reached by a sample before its de­struction. Therefore, the above-mentioned geomet­ric characteristics defined for T state can be noted m as Wru m, .m and Sm (cf. Figure 2). The cross-section of a 2 × 2 rib-knitted structure during the stretching process can be schematically represented as shown in Figure 3. The relative posi­tion of the loops before the process of stretching is shown in Figure 3a, while the change in the relative position of loops during the process of stretching (cf. Figures 3a and 3b) until they gain the state of Tf (m = f ) is shown in Figure 3d. Owing to their intrinsic elastic properties, rib stitch structures can often be used to design sock cuffs, necklines, waistlines, borders on sweaters etc. 2.2 Geometric approximation In recent researches, different approaches are used for textile clothes simulation [23]. The most com­monly used are mesoscale modelling [10–12] and macro-level garment simulation [24, 25]. However, Figure 2: Parts of ribbed patterns within rib stitch structures Figure 3: Transformation of knitted fabric elements of 2 × 2 rib structure in process of uniaxial course-wise stretching according to the authors’ knowledge, there is no published work dedicated to macro-modelling of rib-knitted garment parts. The body parts covered with a tubular rib-knitted garment or its segments can be approximated by a set of conical surfaces, e.g. to provide a mathematical analysis of a ribbed sock cuff, it is possible to approximate the leg sur­face with a frustum (cf. Figure 4b) with the radii of bases Rs1 and Rs2, the perimeters of which corre­spond to the leg girths in sections 1 and 2, respec­tively (cf. Figure 4a). Figure 4: Simplification of shin surface shape with frustum with equivalent base circumferences 3 Results and discussion In general, if a tubular shell made of an even rib stitch pattern knit is put onto a conical surface, the knitted structure may undergo various levels of stretching in the course-wise direction. In case the tubular rib-knitted garment was produced without changing the number of working needles and stitch density, the number of loops in one course and the loop length do not change. 3.1 Stretching geometry When the number of rib stitch patterns in one cir­cular course is denoted as Nru and the perimeter of a ribbed tube in a free state as Q0 (mm), then the pattern width in a free state Wru0 (mm) can be de­termined with equation 1: ....0 ....!" 0 = (1) ....!" If putting a tube with Q0 perimeter onto a conical surface as shown in Figure 5, three cross-sections with R1, Rand Rradii, and Q1, Qand Qperim­ 23 23 eters, respectively, can be schematically represent­ed by three discrete tensile states T1, T2 and T3 as shown in Figure 6. The number of stitches remains unchanged. In the case of transition from T1 to T3, the relative elongation increases and the fabric thickness Mm decreases. The pattern width in T1, T2 and T can be determined by using equations 2–4. 3 ....!" 1 = ....1 ....!" (2) ....!" 2 = ....2 ....!" (3) ....!" 3 = ....3 ....!" (4) Figure 5: Conical surface with radii of cross-sections R1, R2, R3 The correlation of Wru m, Cm and Sm values for each state of tension depends on many factors and is cur­rently determined experimentally [20–22]. Figure 7 presents macro-models of three stretching states of a sample of 2 × 2 rib structure made of PAN yarn of linear density 32 × 2 tex reproduced according to experimental data as described in [21]. Figure 7: Three states of tension of rib stitch structure sample represented in macro-models If a ribbed tube is put onto a cylindrical or conical surface, the following algorithm can be used to de­scribe the mid-surface. 3.2 Set of Bezier curves for one repeated unit mid-surface segment If we assume that 2 × 2 rib stitch structure is wrapped around a cylinder with the perimeter Qm, where Qm = Q0, then the relative elongation .lm (%), can be calculated according to equation 5: (....!-....0) ........!=100 ×(5) ....0 Figure 8 represents a course-wise cross-section of a repeated pattern unit of a rib-knitted fabric wrap­ping a cylinder of radius Rm. The control points P0, P1, P15 and P16 belong to the circle line with the ra­dius Rm_1 = Rm + Dc / 2, where Dc is a yarn diam­eter. Then, the control points P3, P4, P5, P11, P12, P13 are located on the circle line with the radius R = mc Rm + Mm / 2, where Mm is the thickness of the fab­ric, which corresponds to a given state of stretching. Points P7, P8 and P9 are located on the circle line with the radius Rm_2 = Rm_1 + Mm – Dc / 2. ............!·180 ....= (6) ....·....!" (....!-........)·180 ....1 =(7) ....·....!" (....!+........)·180 ....2 =(8) ....·....!" 3.3 Mid-surface geometry description The ruled surface with guide curves described as quadratic Bezier curves can be used to describe the mid-surface of rib-knitted shells (marked as Ms in Figure 8) pulled over the cone base. The radius vec­tor of the ruled surface r (u, v) (cf. Figure 9) can be described as equation 9: ....(....,....)=....1(....)(1 -....)+....2(....).... (9) where 0 = v = 1 is a point on the generating line, and r1(u), r2(u) are quadratic Bezier curves. Figure 9: Building of ruled surface fragment upon Bezier curves Curve lines r1(u) and r2(u) are represented as a com­bination of Bezier curves (equation 10): ....!(....)={....!0(....),....!1(....),.......!"(....)}, (10) where rij(u) is a quadratic Bezier curve. In order to provide the geometric description of a rib stitch pattern (cf. Figure 6), eight quadratic Bezier curves are used. In such a case, a parametric equation of the elementary curve can be presented as follows (equation 11). ....!"(....)=....!,$(1 -....)2 +2 ·....!,$%1(1 -....)·....+....!,$%2....2 (11) where k = 0 ... 14 corresponds to the aggregate num­ber of control vertices that determine the directions of tangents for all elementary curves. The combina­tion of elementary curves represents the central line of a rib stitch pattern Ms (cf. Figure 8). To increase smoothness between adjoining quadratic Bezier curves, it is necessary that the last point of the first segment and the first point of the second segment coincide as shown in Figure 10. Therefore, the equa­tion can be written as (equation 12): ....(1)(1)=....(2)(0) (12) In addition, the joint segment must have a continu­ous inclination at the connection point (equation 13): ....(")(1)=...."....;....(2)(0)=....2...., (13) where T is a unit vector of a common tangent, and a1, a2 are scalar constants that influence the com­pleteness of a segment. It can be proved by the ex­ample (cf. Figure 8): ....(1)(....)=....0(1 -....)2 +2....1(1 -....)·....+....2....2 (14) ....(2)(....)=....2(1 -....)2 +2....3(1 -....)·....+....4....2 (15) ....(")(1)=....$;....(2)(0)=....2; (16) The first condition is considered. For the continuity of a tangent tilt, ....!(#)(1)=2(....%-....#);....'(2)(0)=2(....3 -....2); (17) the unit vector of a common tangent can be calcu­lated as follows: 2(....2 -....1) 2(....3 -....2) ....= = (18) ....1 ....2 where a1 anda2 are tangent vector lengths. Therefore, the equation for the segment of a cone surface can be represented with the following for­mula (equation 19): ....(....,....)=(....1,"(1 -....)2 +2....1,"#1(1 -....)....+....1,"#2....2,· ....2,"(1 -....)2 +2....2,"#1(1 -....).... , (19) ·(1 -....)+. /·.... +....2,"#2....2 where 0 = u, v = 1. 3.4 Software development The above proposed mathematical calculations aimed at the geometric description of the mid-sur­face of rib-knitted shells were installed into the LastikTube program. The latter helps improving the process of designing rib-knitted structure tubular garment parts (cf. Figure 11). The program contains a database, created during experimental studies, which allows determining the relationship between the geometric characteris­tics of the surface, e.g. width of Wru pattern, and the widths of its structural parts, i.e. C convex and a visible part of a concave area S of the pattern unit, created on the base of the analysis of rib knits of various raw materials and pattern numbers. 4 Conclusion Modelling the physical and mechanical knitwear behaviour in the program environment is one of the most promising ways to increase the usability and functionality of knitwear. During the study, the as­sumption was made that certain parts of knitwear made by even rib stitch patterns, e.g. 2 × 2, 3 × 3 etc., can be described as thin-walled elastic shells, the middle surface of which is a linear surface cre­ated upon a set of Bezier curves located along the contours of truncated cone bases. The software, de­veloped in the course of the research, was used to broaden the capability of computer aided design of knitwear, including the macro-modelling of ribbed tubular garments. 3D models, generated by means of the program, can be used for the assessment of thermophysiological comfort. References 1. NIIMI, Yoshitaka, HAVELKA, Antonin, KANAI, Hiroyuki. A proposal for designing knitted fab­ric for the “wear promotes exercise effect” with the purpose of improving comfort. Fibres and Textiles, 2018, 25(4), 71–77, http://vat.ft.tul. cz/2018/4/VaT_2018_4_13.pdf. 2. HERCIKOVA, Eva, KOMARKOVA, Petra, GLOMBIKOVA, Viera, HAVELKA, Antonin, KUS, Zdenek. Evaluation of thermal properties of textile structures under fast flowing air con­ditions. Fibres and Textiles, 2018, 25(4), 31–34, http://vat.ft.tul.cz/2018/4/VaT_2018_4_7.pdf. 3. ANGELOVA, Radostina, REINERS, Priscilla, GEORGIEVA, Elena, KONOVA, Hristina Plamenova, PRUSS, Bianca, KYOSEV, Yordan. Heat and mass transfer through outer­wear clothing for protection from cold: in­fluence of geometrical, structural and mass characteristics of the textile layers. Textile Research Journal, 2017, 87(9), 1060–1070, doi: 10.1177/0040517516648507. 4. GÜNEY, SestaÇ, AKGÜNOGLU, Betül, KAPLAN, Sibel. Parameters affecting sport socks pressure and pressure prediction from tensile characteristics. Fibres and Textiles, 2017, 24(1), 68–72, http://vat.ft.tul.cz/Archive/VaT_2017_1. pdf. 5. MENGNA, Guo, KUZMICHEV, Viktor. Pressure and comfort perception in the system “female body–dress”. AUTEX Research Journal, 13(3), 71–78, doi: 10.2478/v10304-012-0032-6. 6. NAKHAICHUK, Oleg, ZAKHAROVA, Elina, MIZRAKH, Arkadij, HOROBCHYSHYNA, Valentina. Pressure forecasting of tex­tile materials in the “figure-dress” system. Bulletin of Khmelnytskyi National University. Technical Sciences, 2020, 283(2), 135–140, doi: 10.31891/2307-5732-2020-283-2-135-140, http:// journals.khnu.km.ua/vestnik/?p=1239. 7. BARDOS DE VASCONCELOS, Fernando, CASACA, Fabiano, GOMES DE VASCONCELOS, Fernanda, MARCICANO, Joao Paulo Pereira, SANCHES, Regina Aparecida. Design of elas­tic garments for sports in circular knitting. International Journal of Textile and Fashion Technology (IJTFT), 2013, 3(1), 39–48, http:// www.tjprc.org/publishpapers/--1357879773-4. Design%20full.pdf. 8. KYOSEV, Yordan, Geometrical and mechanical modelling of textile structures at fiber and yarn level – software and data structures. Vlakna a Textil, 2017, 24(1), 3–9, http://vat.ft.tul.cz/ Archive/VaT_2017_1.pdf. 9. KURBAK, Arif, EKMEN, Ozgur. Basic studies for modeling complex weft knitted fabric struc­tures. Part I: a geometrical model for width­wise curlings of plain knitted fabrics. Textile Research Journal, 2008, 78(3), 198–208, doi: 10.1177/0040517507082352. 10. KALDOR, Jonathan, JAMES, Doug, MARSCHNER, Steve. Simulating knitted cloth at the yarn level. 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Simulation of the spherical deformation of biaxial weft-knitted fab­rics using meso and macro models. Fibres and Polymers, 2016, 17(10), 1702–1708, doi: 10.1007/ s12221-016-6511-y. 15. ABGHARY, Mohammad Javad, HASANI, Hossein, NEDOUSHAN, Reza Jafari. Geometrical modeling for bi-axial weft-knitted fabrics based on rib structure. Indian Journal of Fibre & Textile Research, 2017, 42(4), 431–438, http://nopr.niscair. res.in/handle/123456789/43245. 16. LIU, Dani, CHRISTE, Daniel, SHAKIBAJAHRO­MI, Bahareh, KNITTEL, Chelsea, CASTANE­DA, Nestor, BREEN, David, DION, Genevieve, KONTSOS, Antonios. On the role of material architecture in the mechanical behavior of knit­ted textiles. International Journal of Solids and Structures, 2017, 109, 101–111, doi: 10.1016/j. ijsolstr.2017.01.011. 17. WEEGER, Oliver, SAKHAEI, Amir Hosein, TAN, Ying Yi et al. Nonlinear multi-scale mod-elling, simulation and validation of 3D knitted textiles. 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YELINA, Tetiana, HALAVSKA, Liudmyla, MANOILENKO, Oleksandr, Development of a parametric surface model of rib 2x2 knits. Bulletin of the Kyiv National University of Technologies and Design, 2020, 144(2), 80–89 [in Ukrainian], doi: 10.30857/1813-6796.2020.2.8. 22. YELINA, Tetiana, PUKHOVA, Angelina, ROMANIUK, Veronika, HALAVSKA, Liudmyla. Study of the process of stretching in the course-wise direction of different knitting rib struc­ture. Bulletin of the Kyiv National University of Technologies and Design, 2020, 148(4), 98–106 [in Ukrainian], doi: 10.30857/1813-6796.2020.4.9. 23. LONG, James, BURNS, Katherine, and YANG, Jingzhou (James). Cloth Modeling and simula­tion: a literature survey. In Proceedings. Third International Conference, ICDHM 2011, Orlando, Florida, USA, July 9-14, 2011. Edited by Vincent G. Duffy. Berlin, Heidelberg : Springer, 2011, 312– 320, doi: 10.1007/978-3-642-21799-9_35. 24. SPAHIU Tatjana, SHEHI E, PIPERI Erald. 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Tekstilec, 2021, Vol. 64(4), 325–337 | DOI: 10.14502/Tekstilec2021.64.325-337 Sibel Kaplan, Betül Akgünoglu Suleyman Demirel University, Textile Engineering Department, West Campus, Isparta, Turkey Transfer and Friction Characteristics of Sports Socks Fabrics Made of Synthetic Fibres in Different Structures Prenos tekocin in torne lastnosti sinteticnih pletiv za športne nogavice v razlicnih vezavah Original scientific article/Izvirni znanstveni clanek Received/Prispelo 3-2021 • Accepted/Sprejeto 10-2021 Corresponding author/Korespondencna avtorica: Prof. Dr. Sibel Kaplan E-mail: sibelkaplan@sdu.edu.tr Phone: 0090 246 2111183 ORCID ID: 0000-0002-7247-135X Abstract Sports socks fabrics produced from polyester, polypropylene, their modified forms Thermocool®, Polycolon®, in three different structures (single jersey, piquet, terry) were investigated for their skin-fabric friction, permeability (air and water vapour), liquid absorption and transfer (absorbency, immersion, absorption capacity, wetback and drying) properties. According to the results, the effect of structure is dominant for frictional characteristics but focusing on the material, polypropylene created a bulkier and lighter structure with lower friction coeffi­cients, an advantage for sports socks. The effect of structure is greater than the material also for some thermal comfort parameters, e.g. air permeability and absorbency. Focusing on materials, besides their better liquid transfer characteristics, modified forms of both fibres had worse performances for air permeability and absor­bency compared to their standard forms. Absorption capacity, wetback and drying performances were related to fabric density besides the polyester’s higher regain capacity. While Polycolon® had superiority for wetback performance against standard polypropylene, this was not the case for Thermocool®; however, both modified materials showed apparent superiority for drying periods. Piquet structures were advantageous for absorption capacity and wetback performances for polypropylene. For sports socks parts, specific needs can be met by changing the fabric structure. Considering the materials, polypropylene and Polycolon® can be recommended for both thermal and tactile aspects. Keywords: sports socks, Thermocool®, Polycolon®, friction, liquid transfer Izvlecek Na levo-desnih pletivih za športne nogavice, izdelanih iz poliestra, polipropilena in njunih modificiranih oblik Thermocool® in Polycolon® v treh vezavah, tj. enostavni levo-desni, pike in frotir, so bili preizkušani trenje pletiva ob kožo, prepustnostne lastnosti (zracna prepustnost, prepustnost vodne pare), absorpcija in prenos tekocine (vpojnost, omocljivost pri potapljanju, zmogljivost vpojnosti, povratno vlaženje in sušenje). Glede na rezultate ima vezava prevla­dujoc vpliv na torne lastnosti, pri osredotocenju na material pa je pletivo iz polipropilena lažje in bolj voluminozno ter ima nižji koeficient trenja, kar je za športne nogavice prednost. Vpliv vezave je vecji od vpliva materiala tudi za nekatere dejavnike toplotnega udobja, kot sta zracna prepustnost in vpojnost. Ce se osredinimo na materiale, modificirani tipi vlaken Thermocool® in Polycolon® bolje prenašajo tekocine ter imajo slabšo zracno prepustnost in vpojnost kot standardni tipi vlaken. Vpojnost, povratno vlaženje in sušenje so bili povezani z višjo reprizo poliestra in gostoto pleti­va. Medtem ko je bil za Polycolon® prenos vlage na hrbtno stran vecji kot pri standardnem polipropilenu, to ne velja za Thermocool®; oba modificirana materiala sta obcutno boljša glede casa sušenja. Vezava piké ugodno vpliva na zmogljivost vpojnosti in povratno vlaženje pletiva iz polipropilena. Za sestavne dele športnih nogavic je zadovoljeva­nje specificnih potreb mogoce doseci s spremembo vezave pletiva, glede izbire materiala pa sta z vidika toplotnih in taktilnih lastnosti priporocljiva polipropilen in Polycolon®. Kljucne besede: toplotna udobnost, tipna udobnost, prenos mase 1 Introduction Consumers require multifunctional apparel prod­ucts with superior comfort performance and sports socks is one of the clothing groups for which both thermal, pressure and tactile comfort performances are crucial. Socks comfort has a big influence on the performance of sports people and it is difficult to enable dryness, necessary insulation and mechan­ical comfort for different kinds of sports shoes as it is a closed system. Compression support, minimisa­tion of foot blisters as a result of cyclic friction un­der high temperature and relative humidity within the shoes [1], moisture management properties, an­atomically placed cushioning and shock absorbing properties [2] can be listed as characteristics of op­timal sports socks. Sweating, which may reach up to 0.5 litres per foot during a sports activity with­in shoes not allowing adequate liquid, and water vapour transfer is the main reason for dampness sensation, decreased insulation, foot injuries occur­ring as a result of softer skin or wet fabric having a higher friction coefficient, some health problems sourcing from microorganisms and increased fa­tigue feeling [3–10]. Therefore, besides liquid ab­sorption period and capacity, good athletic socks fabric must also transport sweat away from the foot surface not to create the above mentioned prob­lems. Mechanical interactions between the skin and fabric are the sources of skin irritations for some specific garments such as socks and fitted sports clothing, e.g. swimwear, leggings etc. [11]. The men­tioned friction characteristics of fabrics produced from different materials and fabric structures are generally evaluated by subjective tests [12–14] and fabric surface analyses with a reciprocating linear tribometer [15–17], horizontal platform method [18] and 3D biomechanical models with computational simulations [19]. The material and fabric structure of sports socks are the determinant factors of comfort and defor­mation related problems. Ideally, under pressure, an athlete should wear hydrophobic socks in regions prone to blister formation and shoes with a hydro­philic inner liner [20]. Sports socks are usually pro­duced from standard or modified synthetic fibres and their blends for insulating and moisture wick­ing abilities without absorption and lighter weight upon sweating, enabling less energy expenditure [21–24]. Polyester, polyamide, polypropylene, acryl­ic (generally as pile structure) and elastane are the most common fibres used in sports and active wear [22, 24]. Polypropylene and its modified forms are increasingly being used in the sportswear market for generally inner layers [21] with their very low moisture absorbency, insulation retaining perfor­mance, excellent moisture vapour permeability and transplanar/in plane wicking capabilities [11]. A worsted spun yarn, Polycolon®, was suggested for cold weather protective gloves [25] and for shoe in­soles with its good capillary wicking abilities [26]. Bioceramics (1%) were also used for socks and managed moisture on foot better than cotton/pol­yester [27]. Generally single jersey, false rib, terry and piquet structures are used on different parts of sports socks for thermal comfort enhancements, to decrease friction and pressure on specific parts [2]. In this study, permeability, liquid absorption/trans­fer and skin-fabric friction characteristics of sports socks fabrics produced from polyester, its modified form Thermocool®, polypropylene and its modified form Polycolon® were investigated. Single jersey (without elastane), piquet and terry fabrics were knitted to simulate structures on different parts of functional sports socks. 2 Materials and methods 2.1 Materials Socks fabrics were knitted from Ne 26 standard pol­yester, its modified form Thermocool®, Ne 34 stand­ard polypropylene and its modified form Polycolon® staple yarns, the characteristics of which are sum-marised in Table 1. Thermocool® is a unique blend of fibres with a hollow core that enables light weight, Table 1: Characteristics of yarns used for socks fabrics Fabric code Knit type Material Yarn count Twist coefficient (ae) [S.D.] a) PESA Single jersey 100% polyester 227 dtex 4.34 [0.12] PESB Piquet 78% polyester/15% polyamide/7% elastane 227 dtex PES + 20/40dtex /13f PA gimped – PESC Terry MPESA Single jersey 100% Thermocool® 227 dtex 5.34 [0.02] MPESB Piquet 78% Thermocool®/15% polyamide/7% elastane 227 dtex PES + 20/40 dtex /13f PA gimped – MPESC Terry PPA Single Jersey 100% polypropylene 174 dtex 3.43 [0.10] PPB Piquet 74% polypropylene/17% polyamide/9% elastane 174 dtex PP + 20/40 dtex/13f PA gimped – PPC Terry MPPA Single Jersey 100% Polycolon® 174 dtex 3.29 [0.09] MPPB Piquet 74% Polycolon®/17% polyamide/9% elastane 174 dtex PP + 20/40dtex/13f PA gimped – MPPC Terry a) standard deviation higher insulation and a channelled cross section for better wicking and drying abilities [28]. Polycolon® is a modified, polypropylene-based, worsted-spun long-staple yarn produced by Scholler. It has the lowest surface tension of all synthetic functional fi­bres and does not absorb moisture. With its good liquid transfer properties, it decreases the risk of blisters when used for socks. It is the lightest func­tional fibre in the world; around 40% lighter than cotton and 35% lighter than polyester [29]. Fabrics having single jersey, piquet and terry struc­tures were knitted on a Lonati 400 socks knitting machine with 3 3/4 inch diameter, 200 needles and E value of 18. Single jersey fabrics were knitted without any other component to see the material effects clearly, while the piquet and terry structures were knitted with 20/40 dtex/13 f (spandex/polyam­ide) elastomeric inlay yarn (full plating). The socks parts where investigated knit types are used can be seen in Table 2. Table 2: Knitting structures used on different parts of sports socks Knit code A B C Knit type Single Jersey Piquet Terry Needle diagram Regions of knit types on socks 2.2 Methods 2.2.1 Physical and frictional characteristics Weight and thickness were tested according to TS 251 and ASTM D 1777 with 5 g/cm2 pressure with a James Heal R&B Cloth Thickness Tester (James Heal Corp., UK) in turn. Physical porosity char­acteristics were calculated according to Equation 1 [22]. $1-.... ....= ....)....100 (1) where P is porosity (%), m is fabric density (g/cm3) and . is fibre density (g/cm3). Friction coefficients of socks fabrics were calcu­lated with friction force measurements conducted according to ASTM D 1894-14 with a Lloyd LR5K Plus (Lloyd Instruments, Inc., USA) tensile strength tester. Static and kinetic friction coefficients were calculated (cf. Equation 2) from force results ob­tained for wale direction as a result of movement of a sled (3.9 cm × 4 cm) covered with lambskin with a speed of 25 mm/min and normal force of 2.50 g/cm2 on a platform covered with the socks fabric (inner side up). µ=..../.... (2) where N is normal force (N) and F is static/kinetic frictional force. 2.2.2 Permeability and liquid absorption/transfer characteristics The air and water vapour permeability values were tested according to TS 391 EN ISO 9237 by FX Textest 3300 (James Heal Corp., UK) and ASTM E96-16 Cup Method in turn. The absorbency and liquid transfer characteristics of samples were test­ed with drop test according to AATCC 79:2018 and with sinking time (immersion) test according to AATCC 79-Method B. Absorption capacities were calculated according to the modified version of ISO 20158:2018 and drying periods were deter­mined according to a preceding study [30] until the fabrics come to their conditioned weight. From dry­ing graphics, slopes of the weight loss lines (amount of evaporated liquid/evaporation period) that give idea about the drying rates were calculated to have an exact comparison. Transverse wicking (wet­back) rates were determined according to a preced­ing study [31] from the liquid amounts transferred from the wet sample (including liquid equal to their absorption capacities) to the dry samples 74.5 mm in diameter under the pressure of 15.6 kg/m2 af­ter the periods of 5 min, 10 min, 15 min, 20 min, 25 min and 30 min. All fabrics were washed according to TS EN ISO 6330:2012 in a Wascator FOM71 CLS washing ma­chine (James Heal and Co. Ltd., Halifax, UK) and conditioned under standard atmospheric condi­tions (20 ± 2 °C, 65 ± 2% RH) according to ASTM D1776-08e1 (2009) before the tests. 2.2.3 Statistical analyses IBM SPSS 21.0 Statistics Software (SPSS Inc. USA) was used for the Multivariate Analysis of Variance (MANOVA) test to investigate the effects of mate­rial and structure on the investigated parameters. MANOVA is used when more than one factor af­fecting the dependent variable, including all their combinations at different levels, are studied and tested. Duncan and Student Newman Keuls (SNK) tests were used to examine significant differences. Statistical significances were investigated with p values (p < 0.05 meaning significant difference). A correlation analysis was conducted to determine the relationships among physical and mechanical parameters. 3 Results and discussion Material (polyester, polypropylene, Thermocool®, Polycolon®), structure/knit type (single jersey, pi-quet and terry) of the fabrics and their interactions obtained from MANOVA had significant effects on all physical, surface, permeability and liquid transfer characteristics, as it can be seen in Table 3 (p < 0.05). Table 4 shows material effects of socks fabrics grouped according to three different knit types. 3.1 Physical and surface properties Physical properties of socks fabrics produced from different synthetic yarns in different knit types are compiled in Table 5. As it can be seen in Table 4, for single jersey fab­rics, the lowest weight belonged to polypropylene (PP) followed by Polycolon® (MPP) related to their fibre densities, while the polyester (PES) fabric had significantly the maximum weight. The trend is valid for other structures except for the higher val­ue of MPP for the piquet fabric. Thickness values Table 3: MANOVA results of main factor-parameter interactions Dependent variable Significance values of main factors (p) Material Structure Material × structure Weight 0.00 0.00 0.00 Thickness 0.00 0.00 0.00 Static friction coefficient 0.00 0.00 0.00 Kinetic friction coefficient 0.000 0.001 0.000 Air permeability 0.00 0.00 0.00 Absorption period (drop) test 0.00 0.00 0.00 Immersion period 0.00 0.00 0.00 Absorption capacity 0.00 0.00 0.00 Table 4: Post-hoc test results of fabric properties Property Single jersey Piquet Terry Weight PP < MPP < MPES < PES PES < PP < MPES = MPP PP = MPP < PES = MPES Thickness PES = MPES < PP = MPP MPES = PP < PES < MPP PES < MPES = MPP < PP Static fric. coeff. MPP = PP = PES < MPES PP = MPES = MPP < PES PP = MPP < MPES = PES Kinetic fric. coeff. PP = MPP = PES < MPES PP = MPES = MPP < PES PP = MPP < MPES < PES Air permeability MPES < PES < MPP < PP MPP < PP < MPES < PES MPP < PP < MPES < PES Absorption period (drop) test PES < PP < MPES < MPP PP did not absorb MPP did not absorb PES=MPES PP did not absorb MPP did not absorb PES < MPES Immersion period PP did not sink MPP did not sink PES < MPES PP did not sink MPP did not sink MPES < PES PP did not sink MPP did not sink MPES < PES Absorption capacity PP = MPP < MPES < PES Statistically identical PP < MPP < PES < MPES (cf. Figure 1) are generally higher for PP and MPP, enabling bulkier structures. However, there are some exceptions that PES had higher thickness than PP for the piquet fabric, and the modified forms of both (MPES and MPP) had identical thickness val­ues for the terry fabric. According to the porosity values compiled in Table 5, higher values belonged to the piquet and single jersey structures for poly­ester and polypropylene fabrics in turn. The piquet and terry structures generally had identical porosity values due to the tuck and pile loops within the fab­ric structures in turn. The differences among pol­yester and polypropylene fabrics were not clear as the porosity equation includes a ratio of fibre and fabric densities, despite the lower fabric (as a result of lower yarn linear density) and fibre densities of polypropylene. According to friction coefficient results, the min­imum and identical static and kinetic friction Figure 1: Fabric thickness values Table 5: Physical properties of fabrics Fabric code Courses-wales (1/cm) Weight (g/m2) [S.D.] Density (g/cm3) [S.D.] Porosity (%) [S.D.] PESA 70-42 255.20 [2.34] 0.39 [0.013] 71.85 [0.92] PESB 84-50 266.4 [5.48] 0.16 [0.005] 94.81 [0.36] PESC 80-56 544.62 [26.80] 0.19 [0.013] 85.88 [0.95] MPESA 70-42 149.60 [9.22] 0.22 [0.013] 83.93 [0.93] MPESB 88-75 264.87 [3.00] 0.18 [0.003] 87.05 [0.25] MPESC 92-57 553.35 [25.52] 0.19 [0.007] 86.29 [0.56] PPA 84-51 93.70 [1.92] 0.13 [0.005] 86.01 [0.55] PPB 86-38 254.98 [5.01] 0.17 [0.005] 81.63 [0.61] PPC 84-40 520.98 [4.46] 0.16 [0.006] 82.08 [0.71] MPPA 72-54 94.98 [1.38] 0.13 [0.001] 85.59 [0.12] MPPB 80-54 263.40 [3.21] 0.15 [0.004] 83.17 [0.43] MPPC 74-55 475.33 [12.04] 0.16 [0.007] 81.91 [0.83] Legend: PES: polyester, MPES: Thermocool®, PP: polypropylene, MPP: Polycolon® A: Single Jersey, B: Tucked, C: Terry coefficients were obtained for PP, MPP (confirming Dyck’s study in 1993), maximum values belonged to MPES for single jersey, and PES for the piquet and terry fabrics (cf. Figure 2). For the knit types, while terry fabrics created rougher surfaces for polyester fabrics, single jersey fabrics were rougher for poly­propylene according to both static and kinetic fric­tion coefficients. Both material and fabric structure were affective [18]; however, the effect of the fabric structure seems greater on friction coefficients con­firming the results by Richie [32]. 3.2 Permeability and liquid absorption/ transfer properties The permeability and absorbency/transfer character­istics of the socks fabrics can be seen in Table 6. Air permeability results (cf. Figure 3), giving idea about the porous structure of the fabric, show the ranking of PP, MPP, PES and MPES from the maxi­mum values for single jersey fabrics, a result propor­tional to fabric density and porosity values (cf. Table 4). Worse performances of MPES and MPP, when compared to their standard forms, can be attributed to the rougher surfaces of modified fibres within sta­ple yarn having higher frictional area with air. While terry fabrics had significantly lower air permeabili­ty values than piquet fabrics (cf. Figure 3), material trends are the same for both structures. Both stand­ard and modified PES fabrics had higher values than PP and modified PP for piquet and terry fabrics as a result of their higher porosity, confirming a preced­ing study [33]. As a general look, effects of fabric structure seem greater than material on air permea­bility, confirming a preceding study [11]. The effect of linear density was not observed for piquet and terry structures including elastomeric inlay yarn. a) b) Figure 2: Static (a) and kinetic (b) friction coefficients Water vapour permeability results could not dis­criminate the fabrics (p > 0.05), probably due to the insufficient precision of the cup method and envi­ronmental condition variations (cf. Table 6), despite the test conducted under standard atmospheric conditions. To move in a fibrous medium, a liquid must wet the fi­bre surface before being transported through inter-fi­bre pores by means of capillary action. The fibre-liq­uid surface attraction force causes wetting action and is determined by fibre and fabric surface characteris­tics, pore distribution and liquid properties [34–35]. The PP and MPP fabrics did not absorb water within acceptable periods (around 5 seconds), except for the PP single jersey fabric (6.63 s), due to their lowest sur­face tensions (cf. Table 6). Only single jersey fabrics absorbed liquid within acceptable limits (2.24–8.08) as a result of their open pore structures where liq­uid can be bound better. MPES and MPP yarn fab­rics (mainly designed for better liquid transfer and insulation) absorbed moisture within significantly longer periods than PES and PP as a result of irreg­ular cross sections of these fibres that might decrease contact surface area with water, hence surface energy. Rougher surfaces of piquet and terry fabrics also de­creased their surface energy that they absorbed water within 16.45–26.17 seconds contrary to the preceding statement about better wettability of rougher surfaces by well wetting fluids [35]. The procedure and real life simulation ability of the test method should also be considered, namely, sports socks are normally used within shoes under pressure and the surface energy surely differs under these conditions. Table 6: Permeability and liquid absorption/transfer characteristics Fabric code Water vapour permeability (g/m2/24 h) [S.D.] Absorption period (drop) test (s) [S.D.] Sinking period (s) [S.D.] Drying rate/speed (g/h) PESA 659.57 [191.46] 2.24 [0.20] 102.01 [21.54] 0.477 PESB 561.91 [129.64] 20.14 [6.54] 427.39 [22.92] 0.762 PESC 489.04 [49.33] 16.45 [6.18] 207.71 [19.45] 0.786 MPESA 604.21 [62.04] 8.08 [0.04] – 0.435 MPESB 566.37 [40.90] 21.51 [0.13] 271.08 [90.14] 0.692 MPESC 616.85 [75.98] 26.17 [0.09] 173.78 [63.69] 0.866 PPA 493.80 [106.63] 6.62 [0.17] – 0.344 PPB 580.36 [148.15] – – 0.779 PPC 569.70 [100.13] – – 0.651 MPPA 534.02 [94.58] 11.44 [0.15] – 0.253 MPPB 609.98 [178.56] – – 0.764 MPPC 462.58 [42.32] – – 0.807 Legend: PES: Polyester, MPES: Thermocool®, PP: Polypropylene, MPP: Polycolon® A: Single Jersey, B: Tucked, C: Terry –: did not absorb water or did not sink The immersion or sinking period results (cf. Table 6) giving idea about both absorption and transfer of liq­uid within a fabric were also in harmony with the ab­sorption period results that the PP and MPP fabrics did not sink as they did not absorb liquid. Although designed for better transfer capability, the MPES fab­ric did not have superior performance than standard PES for single jersey fabric showing solely the mate­rial effect. MPES Thermocool® had lower sinking pe­riods for both piquet and terry fabrics showing the effects of fibre cross sections and the porous struc­ture of fabrics. The sinking time of about 5 seconds is generally considered satisfactory for well-prepared cellulosic materials [36] and none of the fabrics had a closer performance due to their hydrophobic natures. The absorption capacity values, which affect the dampness sensation, hence comfort, were discrim­inated more for terry fabrics. For the terry fabrics, MPES had better performances than PES, followed by MPP and PP (cf. Figure 4). Single jersey fabric results showing solely the material effect were the highest for PES; modified forms of both PET and PP could not show superior performances as the ab­sorption capacity is related to the macromolecular structure of the fibre, not its cross section. Better performances of PES against PP can be attributed to their higher moisture regain values (0.4% when compared to 0% of polypropylene) [37]. When the fabric structure is considered, piquet structures had significantly better performances when compared to terry fabrics. Summing up, apart from the fibre macromolecular structure, the fabric structure is also effective on the absorption capacity confirming a preceding study [33]. Besides moisture absorption capacity of the socks fabric, its liquid transfer to another clothing lay­er (wetback) under pressure is important as well. The geometric configuration of pore structures (inter and intrayarn capillaries) and mechanical stress on a fabric play roles on water transport [11]. According to the transplanar wicking under pres­sure (wetback) test results (cf. Figure 5), standard polyester (PES) transferred the maximum amount of liquid to the outer dry layer for all structures, hence a drier feeling, having the rating of single jersey (A), piquet (B) and terry (C) fabrics starting from the maximum. MPES fabrics come after PES fabrics for the determined period of 30 minutes and its ranking was obtained as piquet (B), terry (C) and single jersey (A) starting from the maximum. As it can be seen in Figure 5, all standard and modified PP fabrics (PP and MPP) transferred the minimum amount of liquid (ranging from 0.48% to 2.31%) to the outer dry layer proportional to their low ab­sorption capacities and short drying periods. The greater amount of liquid was transferred by MPP Polycolon® when compared to standard PP and by piquet fabrics among other knit types confirming their absorption capacity results. Moisture on the skin or clothing increases the heat loss of the body and also affects its overall perfor­mance and endurance. The drying ability of the knitted fabric is primarily affected by the mass per unit area and thickness [37]. The mentioned phenomenon is valid also for this study that ter­ry fabrics with the maximum weight values (PES and MPES) dried within longer periods in spite of their lower absorption capacities than piquet fabrics (cf. Figure 6). Minimum drying periods belonged to polypropylene single jersey fabrics as expected, fol­lowed by polyester fabrics. According to slope cal­culations (cf. Table 6), terry fabrics made of MPES had the maximum drying speed (0.87), followed Figure 5: Transferred liquid from wet to dry fabric (weight gain) under pressure (A: single jersey, B: piquet, C: terry) Figure 6: Drying periods (A: single jersey, B: piquet, C: terry) by MPP Polycolon® (0.81). The drying speed values increased starting from single jersey fabrics (A), followed by piquet (B) and terry fabrics for all ma­terials except for PP. The minimum drying speed belonged to single jersey MPP fabric (0.25) followed by single jersey PP fabric (0.34), MPES (0.44) and PES (0.48) fabrics. It was concluded that drying pe­riods are related more to weight and absorption ca­pacities of fabrics. According to the correlation analysis results, air permeability is negatively correlated with weight and thickness as expected. The denser the fabric, the less air passes through it. The absorption pe­riod (drop) test results are correlated with surface and porosity properties, which shows the effect of surface and structural features on surface energy, hence absorbency of the fabric. Other significant correlation coefficients are compiled in Table 7. Table 7: Correlation analysis results 4 Conclusion Sports socks have a decisive influence on com­fort and performance of sports people. The per­ceived comfort, mainly affected by temperature and dampness feelings, depends on the fibre con­tent and construction of socks. Moreover, friction­al deformation occurring on foot skin, perceived by mechanoreceptors, is also important for sports performance. During walking or running, besides cyclic pressure, friction and shear forces result­ing from forward or sideways momentum of the athlete, increased moisture level and temperature within sports shoes are the main reasons for foot blisters. Therefore, in this study, friction, perme­ability and liquid transfer characteristics of socks fabrics produced from standard and modified forms of polyester and polypropylene fabrics in different Property Weight Thickness Water vapour perm. Static friction coeff. Kinetic friction coeff. Porosity Weight 0.904 b) Air permeability –0.699 a) –0.837 b) Absorption period (Drop) 0.661 a) 0.630 a) 0.645 a) Absorption capacity 0.678 a) Static friction coeff. 0.975 b) a), b): significant for p = 0.05, p = 0.01 in turn structures (single jersey, piquet and terry) were in­vestigated. According to the results, both standard and modified polypropylene Polycolon® gave lighter and bulkier fabrics, which is an advantage for per­meability, hence drying performance of the socks. Polypropylene fabrics also created lower friction coefficients, meaning less deformation on wet skin when compared to polyester. Polyester, especial­ly the standard one, has a bigger potential for skin deformation, the effect of fabric structure here be­ing greater. The modified forms of polyester and polypropylene (Thermocool® and Polycolon®) had worse performances for air permeability, which may be related to their higher fibre surface areas. For liquid absorption, polyester was advantageous, but piquet and terry structures of polypropyl­ene did not absorb liquid. The modified polyester Thermocool® did not have a superiority for liquid absorption, but it transferred liquid better for piquet and terry structures. While the absorption capacity is related to the regain capacity of the fibre and fab­ric density, besides its lower capacity, polypropylene had better performances in piquet structure which is also the case for wetback performance. Polycolon® had better wetback performance when compared to standard polypropylene, which was not the case for polyester. Both Thermocool® and Polycolon® had better performances for drying periods. Yarn line­ar densities of polyester and polypropylene fabrics surely had influence on fabric density, porosity and hence permeability characteristics, which can be accepted as a weakness of this study. In conclusion, polypropylene, especially modified form Polycolon® and piquet structures, can be suggested for plan­tar and lateral foot parts where blisters occur dur­ing running under high moisture and temperature conditions. Acknowledgments This work was supported by Suleyman Demirel University (Project Number: 4840-YL1-16) for fabric tests and Celik Socks Company for fabric production. We would like to thank to both for their valuable contribution. References 1. DAN, R., FAN, X. R., XU, L. B., ZHANG, M. Numerical simulation of the relationship between pressure and material properties of the top part of socks. Journal of the Textile Institute, 2013, 104(8), 844–851, doi: 10.1080/00405000.2012.758516. 2. 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Mahbubul Haque6, Mohammad Abdul Jalil 5 1 Northern University Bangladesh, Department of Textile Engineering, Dhaka-1213, Bangladesh 2 ZR Research Institute for Advanced Materials, Sherpur-2100, Bangladesh 3 Khwaja Yunus Ali University, Department of Textile Engineering, Sirajgang-6751, Bangladesh 4 Kaunas University of Technology, Department of Production Engineering, Faculty of Mechanical Engineering and Design, Studentu 56, LT-51424, Kaunas, Lithuania 5 Khulna University of Engineering & Technology, Department of Textile Engineering, Khulna-9203, Bangladesh 6 Daffodil International University, Department of Textile Engineering, Dhaka-1207, Bangladesh Factors Affecting Apparel Pattern Grading Accuracy: Existing Software Solutions Comparison and Development of New Solution Dejavniki, ki vplivajo na natancnost gradiranja krojev oblacil: primerjava obstojecih programskih rešitev in razvoj nove rešitve Original scientific article/Izvirni znanstveni clanek Received/Prispelo 12-2020 • Accepted/Sprejeto 10-2021 Corresponding author/Korespondencni avtor: Mohammad Abdul Jalil E-mail: drjalil@te.kuet.ac.bd Phone: +8801711269630 ORCID ID: 0000-0002-0006-8086 Abstract Every so often, grading is not 100% accurate due to the conventional system for calculating the grading incre­ment. The aim of this study was to develop a new calculation system of grading increment provided by different software, e.g. Lectra, Gerber, Optitex, Boke CAD etc., and to develop a new mathematical solution that enhances grading precision. For this experiment, three different spec sheets of different buyers were collected, and then combined and drawn to a solitary sketch for both front and back including all points of measures (POM) for a more easy comparison. The solutions for the presence of diagonal and curve measurements were provided with examples using various tools and techniques of different professional garment CAD software. The benefit of the new approach is not only reduced errors of grading but also guaranteed garment fit without distorting style features. However, the drawbacks of the measurement method are complicated and time-consuming. They revolve around the fact that iterative fitting and adjustments are mandatory to improve the fit before bulk production. The study revealed that this new system slightly increases calculation time, whereas the sample approval time for order execution reduces considerably. Keywords: grading, CAD, pattern making, grading system, Pythagoras grading Izvlecek Gradiranje pogosto ni 100-odstotno natancno zaradi konvencionalnega sistema za izracun gradirnega prirastka. Namen te študije je razviti nov sistem izracunavanja gradirnega prirastka v primerjavi s tistimi, ki jih ponujajo razlicna programska orodja, kot so Lectra, Gerber, Optitex, Boke CAD ipd., in razviti novo matematicno rešitev, ki izboljša na­tancnost gradiranja. Za raziskavo so bile izbrane tri tehnicne skice razlicnih proizvajalcev, združene v eno samo skico oblacila, ki prikazuje sprednji in zadnji del oblacila ter vkljucuje vse mere oblacila za njihovo lažjo primerjavo pri gra­diranju. Nato so na primerih z uporabo razlicnih orodij in tehnik gradiranja z razlicnimi komercialnimi programi CAD PDS prikazani rezultati gradiranja diagonalnih in krivuljnih mer. Prikazana prednost novega pristopa gradiranja ni le v zmanjšanju napak pri gradiranju, temvec tudi v zagotavljanju prileganja oblacila, ne da bi se spremenila njegova oblika. Pomanjkljivost tega pristopa je v zapleteni in dolgotrajni merilni metodi, ki za izboljšanje rezultata gradiranja zahteva rocno prilagajanje gradirnega prirastka. Kljucne besede: gradiranje, CAD, konstruiranje krojev oblacil, gradirni sistem, Pitagorovo gradiranje 1 Introduction Grading is a process of increasing and decreasing pattern dimensions by creating multiple sizes to fit different people [1–3]. In the concepts of pattern grading, it has been described that the grading sys­tem is developed from sizing specifications, and siz­ing specifications are derived from anthropometric surveys [4]. In order to create garments in each size, the increases used to create each new pattern should be based on body measurements associated with that specific size and organised in a size chart. In the late 1960s, computerised grading was developed in the USA, followed by Germany, Italy, Denmark, UK and France to improve the accuracy as well as efficiency [3, 5]. The basic principle of computerised grading is the same as manual grading. The man­ual procedure of grading is exceptionally tedious and grading efficiency is affected by the grader’s ex­perience [6]. The computer was used as a drawing tool. Computerised grading was still tedious and time-consuming; however, the mistake-vulnerable grading process was done satisfactorily with the computerised method. Computer-aided pattern grading systems have become popular in clothing factories as they have become faster, more consistent and accurate, more reliable and manageable than conventional manual grading [7–10]. Generally, grading contains three steps, i.e. determining grade points, determining alteration rules and amounts of each grade point, and joining altered points using the curve smoothing technique [11, 12]. A grade rule can be determined by comparing and calculating mathematical or geometrical differenc­es between the body measurements of each size [1, 13–15]. A grade rule table defines how far each car­dinal point of pattern moves in the x and y direction in a Cartesian graph [16]. The way towards grading is extremely dreary and requires an incredible lev­el of acumen and discernment, and frequently the exactness of the graded pattern pieces of clothing is affected by the grader’s skills [17]. The proportion of the pattern will vary according to the experience, accuracy and personal judgment of the grader [18]. The problems of assessing the factors affecting ap­parel pattern grading accuracy were identified and some recommendations were proposed in the first part of this work [19]. This paper, however, focuses on the comparison of different solutions to achieve grading accuracy provided by different software, e.g. Lectra, Gerber, Optitex, Boke CAD etc., and develops a new mathematical explanation. Grading has long remained a neglected area of research in the clothing industry and the classical size charts used by the industry have evolved over the years with a trial-and-error method [20]. Pattern grading is a procedure of efficiently enhancing and reducing the measurements of a piece or sloper into a differ­ent number of sizes for large scale manufacturing [4, 17]. The amount and direction into which the pattern increases or decreases has been determined. At the same time, the correct proportions of gar­ments have been maintained without distorting the style features. In order to grade a pattern, increas­es (or decreases) are applied at specific points of a pattern to make each new pattern in another larg­er (or smaller) size. The conventional incremental computerised grading is based on a Cartesian graph that has the horizontal (x) and the vertical axes (x) that intersect at right angles and divide an area into four quadrants. In the Cartesian graph, the dimen­sional changes of patterns are moved to the left or right on the x-axis, and up or down on the y-axis to create new sizes [10, 21]. Consequently, horizon­tal increments are placed on the x-axis and verti­cal measurements on the y-axis. Diagonal meas­urement increments are based on the assumption that they will increase in the same amount as the amount on the x- or y-axis. Nevertheless, scientifi­cally this is not true and will lead to measurement problems. Again, during the grading of the curve line, the amount that should change in the x and y directions to get the desired length of the curve is unknown and complex. Hence, grading increments must be changed more than once until the required curve length is achieved. As it can be seen in the first part of this paper, different problems arise due to the presence of diagonal and curved lines in a spec sheet [22, 23]. The problem is in the calculation method; therefore, the calculation should be done properly to minimise grading errors. The presence of diagonal and the presence of curve measure­ments are only two major problems. Their presence in the spec sheet leads to other problems, as it af­fects the selection of base size, number of sizes pres­ent in the spec sheet etc. If they can be avoided, then other problems will be automatically minimised. For instance, if there is no diagonal measurement, then whatever the base is selected, it will not lead to grading errors. In some spec sheets, it is possible to avoid diagonal and curve measurements but not in all types of product spec sheets. Therefore, solutions to these problems are highly needed. 2 Experimental design 2.1 Materials For this experiment, three different spec sheets of different buyers were collected, combined and drawn to a solitary sketch for both front and back (cf. Figure 1 and Table 1), including all points of measures (POM) to compare them more easily. The measurement points and their descriptions of all three spec sheets are shown in Table 1. 2.2 Methods The solutions for the presence of diagonal and curve measurements are provided below with examples using different tools and techniques of profession­al garment CAD software, e.g. Lectra, Optitex, Gerber, Tuka CAD, Boke CAD. If these CADs are not available and are techniques unknown to the grader, then another mathematical solution was developed by the authors, which is not only appli­cable in software but also in the manual process. It is called “Pythagoras Grading” as authors use the “Pythagoras formula” to calculate new grading in­crement values. All techniques are described and compared with the existing or conventional grading system. Finally, some recommendations are given to choose which solution should be used in what situation. The conventional system is based on the increment of the given measurement of apparel for different sizes, e.g. “body length from high point shoulder” is increased by 2 cm for each size; hence, points H and G should increase by 2 cm in the negative y di­rection. For the T-shirt specs A, B and C, cardinal points (represented by A, B, C, E, G, H for front and back, and A, B, C, D, E, F, G for sleeve) and Cartesian coordinate values of grading increments are shown in Figure 2. 3 Experimental work To solve the grading error due to the presence of di­agonal and curve measurements, there are different solutions possible, which are described below. 3.1 Solutions to problem 1 – presence of diagonal measurements 3.1.1 Solution 1 to problem 1 – manual manipulation of grading increment When grading is required in a particular point, an increment only from the base size to the next higher size is calculated. However, there are two problems Figure 2: Cardinal points and Cartesian coordinate values of T-shirt specs A, B and C Table 1: Measurement points and their descriptions of all three specification sheets Figure 1: Combination of all measurement points of T-shirt Points Description POMs A Back neck drop or depth BND B Front neck drop or depth FND C Neck width or opening NW D Across shoulder width or shoulder to shoulder AS E Shoulder length S F Shoulder drop or slant SD G Armhole straight AHS H Armscye depth ASD I Half chest HC M Body length from high point shoulder BLfHPS Q Sleeve length SL R Sleeve opening SO S Under sleeve US T Sleeve width or upper arm SW X Sleeve cap height SCH Y Shoulder slant in degree SSD POM Reference spec A Reference spec B Reference spec C S M L XL XXL S M L XL XXL S M L XL XXL BND 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 FND 8.00 8.50 9.00 9.50 10.00 8.00 8.50 9.00 9.50 10.00 8.00 8.50 9.00 9.50 10.00 NW 16.00 17.00 18.00 19.00 20.00 16.00 17.00 18.00 19.00 20.00 16.00 17.00 18.00 19.00 20.00 AS – – – – – 45.00 48.00 51.00 54.00 57.00 45.00 48.00 51.00 54.00 57.00 S 15.00 16.00 17.00 18.00 19.00 15.00 16.00 17.00 18.00 19.00 – - - - - SD 5.00 5.00 5.00 5.00 5.00 – – – – – 5.00 5.00 5.00 5.00 5.00 AHS 24.00 25.00 26.00 27.00 28.00 24.00 25.00 26.00 27.00 28.00 – - - - - ASD – – – – – – – – – – 29.00 30.00 31.00 32.00 33.00 HC 48.00 51.00 54.00 57.00 60.00 48.00 51.00 54.00 57.00 60.00 48.00 51.00 54.00 57.00 60.00 BLf-HPS 70.00 72.00 74.00 76.00 78.00 70.00 72.00 74.00 76.00 78.00 70.00 72.00 74.00 76.00 78.00 SL 21.00 22.00 23.00 24.00 25.00 21.00 22.00 23.00 24.00 25.00 21.00 22.00 23.00 24.00 25.00 SO 18.00 19.00 20.00 21.00 22.00 18.00 19.00 20.00 21.00 22.00 18.00 19.00 20.00 21.00 22.00 US 14.00 14.50 15.00 15.50 16.00 – – – – – – - - - - SW – – – – – 23.00 23.75 24.50 25.25 26.00 23.00 23.75 24.50 25.25 26.00 SCH – – – – – – – – – – 9.55 10.40 11.25 12.10 12.95 Note: All units are measured in cm. POM: Points of measure with that. One is that it is assumed that any horizon­tal or vertical increment leads to an increase in the same amount in diagonal measurement, which is scientifically not true. For instance, when shoulder length increased e.g. by 1 cm and half neck width by 0.5 cm, then the horizontal increment would be (1 + 0.5 = 1.5 cm) in case of “spec A” and the ver­tical increment 0 cm as there is no increment in shoulder drop. According to the conventional sys­tem, the horizontal increment for shoulder length of spec A is 1.5 cm for all sizes. However, an incre­ment of 1.5 cm in the horizontal direction does not mean that the diagonal (shoulder length) increment would be the same. After the grading, it was found that the measurements are lower than required. Manually, the measurements are initially increased by 0.01 cm in the horizontal direction until the re­quired length is achieved. From the result, it was es­tablished that at least 0.04 cm should increase along with 1.5 cm measurement, meaning that instead of the 1.5 cm horizontal increment, it should increase by 1.54 cm. And for other sizes, it may be 1.53 or 1.55, since the shoulder angle is not constant. Even if shoulder length increased constantly, e.g. 1 cm (15, 16, 17, 18 and 19 cm for S, M, L, XL and XXL sizes, respectively), the increment should not be the same as the angle of the shoulder for all sizes is not constant, which represents the second problem. To prove this, size spec A of the T-shirt is graded with conventional calculation and then the measurement error is checked, which is shown in Figure 3. After that manual manipulation in grading, the incre­ment is done to rectify the measurements, which is shown in Figure 4. Before and after manipulation measurements for the shoulder are shown below in Figures 3 and 4 along with their grading increment values. Based on Figures 3 and 4, it can be said that if the diagonal measurement exists in a spec sheet, then the measurement checking and manual manipula­tion in grading increment should be done to rectify the measurements. Figure 3: Shoulder length measurements and their grading increment values before manipulation (spec A) Figure 4: Shoulder length measurements and their grading increment values after manipulation (spec A) 3.1.2 Solution 2 to problem 1 – segment editing with Optitex or TukaCAD Manual manipulation is time-consuming; there­fore, different software companies provide differ­ent solutions for grading rectification, e.g. “meas­ure and segment editor” in Optitex and TukaCAD software. The shoulder length before measurement and segment editing is designated in Figure 5, and after measurement and segment editing is given in Figure 6. In segment editing, the “last horizontal” option is chosen since shoulder length can only increase or decrease in the horizontal direction. If the vertical option is chosen, then the shoulder drop measure­ment will change. The selection of the segment ed­itor option depends on the measurement location, e.g. in spec A of the T-shirt, shoulder length and shoulder drop are given. The shoulder drop change has to plot in the vertical direction and the shoulder length change has to plot in the horizontal direc­tion. In the case of spec B of the T-shirt, shoulder length and across shoulder are given. Hence, the across shoulder change has to plot in the horizon­tal direction and the shoulder length change has to plot in the vertical direction. In this case, the “last vertical” option must be chosen in the segment ed- Figure 5: Shoulder length before segment editing (spec A) Figure 6: Shoulder length after segment editing (spec A) itor. Another reason for choosing “last vertical or last horizontal” instead of “first horizontal or first vertical” is due to the shoulder point being the last point and side neck point being the first point of the shoulder line, and in Optitex or Tuka CAD soft­ware, points are counted in the clockwise direction. After segment editing, it was established that there is no diagonal grading error. 3.1.3 Solution 3 to problem 1 – automatic grading with BokeCAD Automatic grading is available only in BokeCAD as far as the authors know. There is a difference between automatic grading and conventional Cartesian coordinate grading. In Cartesian coordi­nate grading, firstly, a base should be selected and a pattern should be drawn according to the base size measurements. Then, the grading increment calcu­lation is done according to the given measurements Figure 7: Shoulder length after conventional grading (spec A) with BokeCAD Figure 8: Shoulder length after automatic grading (spec A) with BokeCAD in the size chart and their input in the x and y direc­tions of the Cartesian coordinate grading. However, in automatic grading, the first whole measurements from the spec sheet should be plotted in the size chart of the software. Then, a base size should be selected and a pattern drawn by the measurement points not by the measurements. When the grad­ing button is clicked, it will automatically grade the whole pattern. The advantages of the system are: a) grading increment calculation is not needed, hence no possibility of miscalculation; b) diagonal meas­urements are automatically adjusted, hence manual manipulation is not needed for the diagonal grading rectification; c) curve grading is almost accurate, as sometimes up to 0.02 cm grading error is found in the case of curve line grading, which is negligible. For the experiment, “spec A” of T-shirts was select­ed and graded with both conventional Cartesian coordinate (x, y) grading and automatic grading method. The results are shown in Figures 7 and 8. From Table 2, it can be seen that graded measure­ments are more precise after automatic grading than conventional grading. 3.1.4 Solution 4 to problem 1 – Pythagoras grading system It was seen that the diagonal measurements grading increments create grading errors. To minimize the latter, a new grading increment calculation system was developed. For this experiment, specs A and B of T-shirts were selected. The details follow below: Table 2: Diagonal length comparison of body part (spec A) with conventional and automatic grading of BokeCAD Point of measures Measurement comparison Size Unit S M L XL XXL Shoulder Error after conventional grading +0.10 +0.05 0.00 –0.04 –0.08 cm Length acquired after conventional grading 15.10 16.05 17.00 17.96 18.92 Length required 15.00 16.00 17.00* 18.00 19.00 Length acquired after automatic grading 15.00 16.00 17.00 18.00 19.00 Error after automatic grading 0.00 0.00 0.00 0.00 0.00 Armhole straight Error after conventional grading +0.01 +0.01 0.00 0.00 0.00 cm Length acquired after conventional grading 24.01 25.01 26.00 27.00 28.00 Length required 24.00 25.00 26.00* 27.00 28.00 Length acquired after automatic grading 24.00 25.00 26.00 27.00 28.00 Error after automatic grading 0.00 0.00 0.00 0.00 0.00 Note: * indicates base size Figure 9: Points to calculate Pythagoras grading for pattern pieces of T-shirt body part (spec A) (a) Pythagoras grading for pattern pieces of T-shirt body part (spec A) Pattern construction of a T-shirt body part can be divided into some geometries that are shown in Figure 9. From . BQC (cf. Figure 9), according to Pythagoras law: BQ2+QC2=BC2 (1), for L size: # BQL=$........"#-........"=)17#-5#=16.25 (2), and for XL size: BQXL=$........#$%-........#$%=)18%-5%=17.29 (3). The x-axis value of shoulder point C = (17.29 – 16.25) + (x-axis change in B point) = 1.04 + 0.5 = 1.54, and y-axis value of shoulder point C = 0 (due to no change in shoulder drop). According to con­ventional calculation, C = (1, 0) which should be re­placed with (1.54, 0). From Figure 9, OR = SD = ¼ chest; QC = RP = shoulder drop; . CP = QR = OR – OB – BQ = (¼ chest) – LLLLL L (½ neck width) L – BQL . CPL = 27 – 9 – 16.25 = 1.75 and CP = QR = OR – OB – BQ = (¼ chest) XLXLXLXLXL XL – (½ neck width) XL – BQXL . CPL = 28.5 – 9.5 – 17.29 = 1.71 From . CPD (cf. Figure 9), according to Pythagoras law: PD!+CP! =CD! (4), for L size: PDL =%26"-1.75"=25.94 (5), and for XL size: PDXL =%27#-1.71#=26.95 (6). The x-axis value of armpit point D = 1.5 (due to change in ¼ chest) and the y-axis value of armpit point D = 25.94 – 26.95 = –1.01. According to conventional calculation, D = (1.5, –1) which should be replaced with (1.5, –1.01). After applying Pythagoras grading, the grading in­crement values of T-shirt body parts are changed, as shown in Figure 10. After the grading with new grading increments of points C and D, the measurements found are pre­sented in Table 3. From Table 3, it can be seen that after apply­ing Pythagoras grading, errors were minimised considerably. Table 3: Diagonal length comparison of pattern pieces of T-shirt body parts (spec A) before and after applying Pythagoras law Point of Measures Measurement comparison Size Unit S M L* XL XXL Shoulder Error before applying Pythagoras law +0.10 +0.05 0.00 –0.04 –0.08 cm Length acquired before applying Pythagoras law 15.10 16.05 17.00* 17.96 18.92 Length required 15.00 16.00 17.00* 18.00 19.00 Length acquired after applying Pythagoras law 15.02 16.01 17.00* 18.00 19.00 Error after applying Pythagoras law +0.02 +0.01 0.00 0.00 0.00 Armhole straight Error before applying Pythagoras law +0.01 +0.01 0.00 0.00 0.00 cm Length acquired before applying Pythagoras law 24.01 25.01 26.00* 27.00 28.00 Length required 24.00 25.00 26.00* 27.00 28.00 Length acquired after applying Pythagoras law 24.00 25.00 26.00* 27.01 28.01 Error after applying Pythagoras law 0.00 0.00 0.00 +0.01 +0.01 Note: * indicates base size (b) Pythagoras grading for the pattern pieces of T-shirt body part (spec B) From . BQC (cf. Figure 9), according to Pythagoras law: BQ!+QC! =BC! (7), where BQL = OQL – OBL = (half across shoulder – half neck width) of size L = 25.5 – 9 = 16.5. For L size: #= QCL=%........"#-........"*17#-16.5#=4.09 (8) and for XL size: BQXL=%18#-17.5# =4.21 (9). The y-axis value of shoulder point C = (4.09 – 4.21) = –0.12 and the x-axis value of shoulder point C = 1.5 (due to change in across shoulder), hence the grading increment value of C = (1.5, –0.12) instead of traditional (1.5, 0.). From . CPD (cf. Figure 9), according to Pythagoras law: CD!+PD! =CD! (10), where CD = armhole straight and CP = QR = OR – OQ = (¼ chest – ½ across shoulder). Therefore, PDL =%........"#-........"# =*26#-1.5# =25.96 (11) and PDXL = %........#$%-........#$% = *27%-1.5% = 26.96 (12). The y-axis value of armpit point D = (25.96 – 26.96) + y-axis point of C = (–1 – 0.12) = (–1.12) and the x-axis value of armpit point D = 1.5 (due to change in ¼ chest), hence the grading increment value of D = (1.5, –1.12) instead of traditional (1.5, –1). After applying Pythagoras grading, the graded 3.2 Solutions to problem 2 – presence of curve measurements were changed, as it can be seen in measurements Table 4. 3.2.1 Solution 1 to problem 2 – segment measuring Figures 10 and 11, and Tables 3 and 4 show that and manual manipulation of grading Pythagoras grading can be used for higher preci-increment value sion grading for diagonal lines. In the first part of the paper [19], it can be seen that the back and front sleeve curves do not match with Table 4: Diagonal length comparison of pattern pieces of T-shirt body parts (spec B) before and after applying Pythagoras law Point of measures Measurement comparison Size Unit S M L* XL XXL Shoulder length Error before applying Pythagoras law +0.07 +0.03 0.00 –0.03 –0.05 Length acquired before applying Pythagoras law 15.07 16.03 17.00* 17.97 18.95 cm Length required 15.00 16.00 17.00* 18.00 19.00 Length acquired after applying Pythagoras law 15.00 16.00 17.00* 18.00 19.00 Error after applying Pythagoras law 0.00 0.00 0.00 0.00 0.00 Armhole straight Error before applying Pythagoras law 0.00 0.00 0.00 0.00 0.00 cm Length acquired before applying Pythagoras law 24.00 25.00 26.00* 27.00 28.00 Length required 24.00 25.00 26.00* 27.00 28.00 Length acquired after applying Pythagoras law 24.00 25.00 26.00* 27.00 28.00 Error after applying Pythagoras law 0.00 0.00 0.00 0.00 0.00 Note: * indicates base size the front and back armhole curve length in the con­ventional grading system. As the armhole straight is given, after shape correction, armhole curve lengths cannot be modified. Sleeve curves must be manipu­lated until they match the curve lengths of front and back armhole curves. For spec B, sleeve width and armhole straight are given. The x-axis of the “F” point (cf. Figure 12) cannot be modified. Instead, a fixed increment must be plotted as sleeve width is given. The y-ax­is must be modified until the curve length of “AF” (cf. Figure 12) matches the front armhole curve lengths. Figures 13–16 show that if curve lengths need to match each other, the measurement checking and manual manipulation in grading increment should be conducted to rectify the measurements. However, in the case of spec A, this method cannot rectify the grading errors as the sleeve curve length measurement and under sleeve measurement are connected to only one point (F point in Figure 12). Any change in the x or y direction affects the other line. It can be said that if a combination such as “di­agonal and vertical” or “diagonal and horizontal” or “curve and vertical” or “curve and horizontal” is given, then it is possible to rectify the grading with the “segment measuring and manual manipulation of grading increment value” technique. However, if the “diagonal and curve” or “diagonal and diago­nal” combination is given, then it is not possible to solve the grading with the “segment measuring and manual manipulation of grading increment value”. 3.2.2 Solution 2 to problem 2 – segment editing with Optitex or TukaCAD Since manual manipulation is time consuming, dif­ferent software companies provide a different solu­tion for grading rectification, e.g. “measure and seg­ment editor” in the Optitex and TukaCAD software. Before and after the measurement of the front and back sleeve curve before and after segment editing are presented in Figures 17–20. In segment editing for the front sleeve curve (spec˜B), the “first vertical” option is chosen and for the back sleeve curve (spec B), the “last verti­cal” option is chosen, as in the Optitex or Tuka CAD software, points are counted in the clockwise direction. Moreover, it is possible to change front and back sleeve curve in the vertical direction since under sleeve is not given. It is not possible to select the horizontal direction as sleeve width is given in spec B. However, in the case of spec A, the segment editor cannot solve the error of sleeve curve length measurement and under sleeve due to them being connected to only one point (F point in Figure 12). Any change in the x or y direction affects the other line. It can be said that if a combination such as “di­agonal and vertical” or “diagonal and horizontal” or “curve and vertical” or “curve and horizontal” is given, then it is possible to rectify the grading with the segment editor. However, if the “diagonal and curve” or “diagonal and diagonal” combination is given, then it is not possible to solve grading with the segment editor (cf. examples above). 3.2.3 Solution 3 to problem 2 – automatic grading with BokeCAD Sometimes the spec sheet does not have any giv­en curve length. However, due to the matching of some curve lengths, the front and back sleeve curve lengths should be matched with the front and back armhole curve lengths. Sometimes, the curve length depends on diagonal length, e.g. in spec B, armhole straight is 26 cm and after making the curve, the front and back armhole curve lengths are 27.50 cm and 27.45 cm, respectively. To get that length sleeve armhole straight, 27 cm (SAHS = AHS + 1 cm) were drawn to get 27.5 and 27.45 cm front and back sleeve curve lengths. However, this is not fixed. Only for this spec, 1 cm is added to the armhole straight to match the curve length. For another spec sheet, it will vary according to the measurement. Due to diagonal grading error, curve lengths changed as well. But even if the diagonal grading values are rectified, the curves do not match 100% with each other and a slight error will occur, the latter being negligible. For 100% matching of the curve, a slight modification is quite enough after automatic grad­ing. Therefore, for the experiment, specs A and B of T-shirts were selected and graded with both the Cartesian coordinate (x, y) and automatic method. The results are presented in Tables 5–6. Tables 5 and 6 show that after automatic grading, there is no diagonal grading error. And up to 0.1 cm, the grading error is found in curve-line grad­ing, which is negligible. 3.2.4 Solution 4 to problem 2 – Pythagoras grading system As it was seen, diagonal measurement and curve measurements related to diagonal measurement create grading errors. To minimize that, a new grading increment calculation system was devel­oped. The author called it “Pythagoras grading”. For this experiment, specs A and B of T-shirts were se­lected. Details are given below. 3.2.4.1 Pythagoras grading for pattern pieces of T-shirt sleeve (spec B) Pattern construction of a T-shirt sleeve can be di­vided into some geometries that are shown in Figure 21. Table 5: Diagonal and curve length comparison of pattern pieces of T-shirt body part (spec B) with conventional and automatic grading of BokeCAD Point of measures Measurement comparison Size Unit S M L* XL XXL Sleeve armhole straight Error after conventional grading +0.43 +0.21 0.00 –0.21 –0.43 cm Length acquired after conventional grading 25.43 26.21 27.00* 27.79 28.57 Length required 25.00 26.00 27.00* 28.00 29.00 Length acquired after automatic grading 25.00 26.00 27.00* 28.00 29.00 Error after automatic grading 0.00 0.00 0.00 0.00 0.00 Front sleeve curve Error after conventional grading +0.51 +0.26 0.00 –0.26 –0.51 Length acquired after conventional grading 25.90 26.70 27.50* 28.30 29.10 cm Length required 25.39 26.44 27.50* 28.56 29.61 Length acquired after automatic grading 25.46 26.48 27.50* 28.52 29.55 Error after automatic grading +0.07 +0.04 0.00 –0.04 –0.06 Back sleeve curve Error after conventional grading +0.51 +0.25 0.00 –0.26 –0.52 cm Length acquired after conventional grading 25.85 26.65 27.45* 28.24 29.04 Length required 25.34 26.40 27.45* 28.50 29.56 Length acquired after automatic grading 25.40 26.42 27.45* 28.47 29.49 Error after automatic grading +0.06 +0.02 0.00 –0.03 –0.07 Note: * indicates base size Table 6: Diagonal and curve length comparison of body part (spec A) with conventional and automatic grading of BokeCAD Point of measures Measurement comparison Size Unit S M L* XL XXL Sleeve armhole straight Error after conventional grading +0.42 +0.21 0.00 –0.21 –0.42 cm Length acquired after conventional grading 25.42 26.21 27.00* 27.79 28.58 Length required 25.00 26.00 27.00* 28.00 29.00 Length acquired after automatic grading 25.00 26.00 27.00* 28.00 29.00 Error after automatic grading 0.00 0.00 0.00 0.00 0.00 Under sleeve Error after conventional grading –0.18 –0.10 0.00 +0.12 +0.25 cm Length acquired after conventional grading 13.82 14.40 15.00* 15.62 16.25 Length Required 14.00 14.50 15.00* 15.50 16.00 Length acquired after automatic grading 14.00 14.50 15.00* 15.50 16.00 Error after automatic grading 0.00 0.00 0.00 0.00 0.00 Point of measures Measurement comparison Size Unit S M L* XL XXL Front sleeve curve Error after conventional grading +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired after conventional grading 25.84 26.65 27.45* 28.25 29.06 Length required 25.34 26.40 27.45* 28.50 29.56 Length acquired after automatic grading 25.41 26.43 27.45* 28.47 29.48 Error after automatic grading +0.07 +0.03 0.00 –0.03 –0.08 Back sleeve curve Error after conventional grading +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired after conventional grading 25.75 26.55 27.35* 28.15 28.95 Length required 25.25 26.30 27.35* 28.40 29.45 Length acquired after automatic grading 25.33 26.34 27.35* 28.37 29.38 Error after automatic grading +0.08 +0.04 0.00 –0.03 –0.07 Note: * indicates base size According to Pythagoras law from . ABG (cf. Figure 21): AG!+GB! =AB! (13), where AB = sleeve armhole straight and GB = sleeve width. For L size: " "= AGL=%........!-........! *27"-24.5"=11.35 (14), for XL size: %= AGXL=%........#$%-........#$*28%-25.25%=12.10 (15). The x-axis value of point A = 0 and the y-axis value of point A = 12.10 – 11.35 = 0.75; the y-axis value of point D = (1 – 0.75) = –0.25; and the x-axis value of point D = 0. Therefore, the value of A = (0, 0.75), B = (0.75, 0), C = (1, –0.25), D = (0, –0.25) and G = (0, 0). After applying Pythagoras grading, the grading in­crement values change, which is shown in Figure 22. The diagonal and curve measurements found after the grading are shown in Table 7. Based on data in Table 7, it can be said that diago­nal and curve grading is up to 0.1 cm error, which is negligible. However, if the under sleeve is given instead of sleeve width, then the calculation is more difficult. 3.2.4.1.1Pythagoras grading for pattern pieces of T-shirt sleeve (spec A) (method 1) The pattern construction of a T-shirt sleeve can be divided into some geometries that are shown in Figure 23. After drawing the pattern and then manually meas­uring the length, the following measurements were found: AGL = 9.02 and GBL = 25.45 (cf. Figure 23). For the grading of sleeve length, the total amount of the grading increment (1 cm) was distributed Table 7: Diagonal and curve length comparison of sleeve pattern piece (spec B) with conventional and Pythagoras grading Point of measures Measurement comparison Size Unit S M L* XL XXL Sleeve armhole straight Error before applying Pythagoras law +0.43 +0.21 0.00 –0.21 –0.43 cm Length acquired before applying Pythagoras law 25.43 26.21 27.00* 27.79 28.57 Length required 25.00 26.00 27.00* 28.00 29.00 Length acquired after applying Pythagoras law 25.02 26.01 27.00* 28.00 29.00 Error after applying Pythagoras law +0.02 +0.01 0.00 0.00 0.00 Front sleeve curve Error before applying Pythagoras law +0.51 +0.26 0.00 –0.26 –0.51 cm Length acquired before applying Pythagoras law 25.90 26.70 27.50* 28.30 29.10 Length required 25.39 26.44 27.50* 28.56 29.61 Length acquired after applying Pythagoras law 25.48 26.49 27.50* 28.52 29.54 Error after applying Pythagoras law +0.09 +0.05 0.00 –0.04 –0.07 Back sleeve curve Error before applying Pythagoras law +0.51 +0.25 0.00 –0.26 –0.52 cm Length acquired before applying Pythagoras law 25.85 26.65 27.45* 28.24 29.04 Length required 25.34 26.40 27.45* 28.50 29.56 Length acquired after applying Pythagoras law 25.44 26.44 27.45* 28.47 29.48 Error after applying Pythagoras law +0.10 +0.04 0.00 –0.03 –0.08 Note: * indicates base size equally on both sides of the zero-point G; hence, AGXL = (9.02 + 0.5) = 9.52. From .AGB (cf. Figure 23), according to Pythagoras law: AG2+ GB2= AB2 (16), and for XL size: GBXL=%28!-9.52! =26.33 (17). The x-axis value of point B = (26.33 – 25.45) = 0.88 and the y-axis value of point B = 0; the value of point A = (0, 0.5), B = (0.88, 0), C = (1, –0.5), D = (0, –0.5) and G = (0, 0). After applying Pythagoras grading, the grading in­crement values change, as shown in Figure 24. After applying Pythagoras grading, the graded measurements changed and are shown in Table 8. 3.2.4.1.2Grading calculation for pattern pieces of T-shirt sleeve (spec A) (method 2 – two sleeves drawing from same starting point) The pattern construction of a T-shirt sleeve can be divided into some geometries when overlapping two consecutive sizes (base size and size next to it), which is shown in Figure 25. From point D (cf. Figure 25), if the pattern of the sleeve is drawn as AD and A2D = sleeve length for L and XL size, DC and DC2 = sleeve opening for L and XL size, AB and A2B2 = armhole straight for L and XL size, and CB and C2B2 = under sleeve for L and XL size, the calculation can be done as value A = (0, 1), D = (0, 0), C = (1, 0) as in the conventional method. However, for calculating the increment of B point, 2 lines from B and B2 points must be extended to intersect at point P. Now, the measurement can be performed manually to measure the values of BP Table 8: Diagonal and curve length comparison of pattern pieces of T-shirt body part (spec A – method 1) with conventional and Pythagoras grading Point of Measures Measurement comparison Size Unit S M L* XL XXL Sleeve armhole straight Error before correction +0.42 +0.21 0.00 –0.21 –0.42 cm Length acquired before correction 25.42 26.21 27.00* 27.79 28.58 Length required 25.00 26.00 27.00* 28.00 29.00 Length acquired after method 1 25.01 26.00 27.00* 28.00 29.00 Error after method 1 +0.01 0.00 0.00 0.00 0.00 Under sleeve Error before correction –0.18 –0.10 0.00 +0.12 +0.25 cm Length acquired before correction 13.82 14.40 15.00* 15.62 16.25 Length required 14.00 14.50 15.00* 15.50 16.00 Length acquired after method 1 14.17 14.58 15.00* 15.43 15.86 Error after method 1 +0.17 +0.08 0.00 –0.07 –0.14 Front sleeve curve Error before correction +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired before correction 25.84 26.65 27.45* 28.25 29.06 Length required 25.34 26.40 27.45* 28.50 29.56 Length acquired after method 1 25.42 26.44 27.45* 28.46 29.48 Error after method 1 +0.08 +0.04 0.00 –0.04 –0.08 Back sleeve curve Error before correction +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired before correction 25.75 26.55 27.35* 28.15 28.95 Length required 25.25 26.30 27.35* 28.40 29.45 Length acquired after method 1 25.33 26.34 27.35* 28.36 29.37 Error after method 1 +0.08 +0.04 0.00 –0.04 –0.08 Note: * indicates base size and B2P, which are actually the x- and y-axis values of B point. Hence, B = (0.91, 0.57). After applying method 2, the grading increment values change, which is shown in Figure 26. The measurements found after the grading can be seen in Table 9. Regarding data in Table 9, it can be said that there is a minimum deviation from the original meas­urements, i.e. only up to 0.01 cm error, which is negligible. The values can also be slightly adjust­ed (increase or decrease as required) to get 100% accurate length. If sleeve width is given instead of under-sleeve, then it is very easier to calculate the grading increments. 4 Recommendation for presence of diagonal and curve measurements 4.1 Recommendation for problem 1 – presence of diagonal measurements Diagonal measurements should be avoided as much as possible in the spec sheet since they cause grad­ing deficiency. If the diagonal measurement exists in a spec sheet, then the measurement checking and manual manipulation in grading increment should be conducted to rectify the measurements. It can be Table 9: Diagonal and curve length comparison of pattern pieces of T-shirt body part (spec A – method 2) Point of measures Measurement comparison Size Unit S M L* XL XXL Sleeve armhole straight Error before correction +0.42 +0.21 0.00 –0.21 –0.42 cm Length acquired before correction 25.42 26.21 27.00* 27.79 28.58 Length required 25.00 26.00 27.00* 28.00 29.00 Length acquired after method 2 25.00 26.00 27.00* 28.00 29.00 Error after method 2 0.00 0.00 0.00 0.00 0.00 Under sleeve Error before correction –0.18 –0.10 0.00 +0.12 +0.25 cm Length acquired before correction 13.82 14.40 15.00* 15.62 16.25 Length required 14.00 14.50 15.00* 15.50 16.00 Length acquired after method 2 14.02 14.5 15.00* 15.50 16.01 Error after method 2 +0.02 0.00 0.00 0.00 +0.01 Front sleeve curve Error before correction +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired before correction 25.84 26.65 27.45* 28.25 29.06 Length required 25.34 26.40 27.45* 28.50 29.56 Length acquired after method 2 25.41 26.43 27.45* 28.47 29.48 Error after method 2 +0.08 +0.03 0.00 –0.03 –0.08 Back sleeve curve Error before correction +0.50 +0.25 0.00 –0.25 –0.50 cm Length acquired before correction 25.75 26.55 27.35* 28.15 28.95 Length required 25.25 26.30 27.35* 28.40 29.45 Length acquired after method 1 25.32 26.34 27.35* 28.36 29.38 Error after method 1 +0.07 +0.04 0.00 –0.04 –0.07 Note: * indicates base size done in any garment CAD. However, if Optitex or TukaCAD is available, then the “measure and seg­ment editor” function can be used to minimise the diagonal line grading error. If BokeCAD is availa­ble, then “automatic grading” can be used instead of “conventional grading” as both methods are available in BokeCAD. Even if Optitex or TukaCAD or BokeCAD is not available, or we are not famil­iar with the particular function to rectify grading, then Pythagoras grading can be used to minimise inclined line grading errors. 4.2 Recommendation for problem 2 – presence of curve measurements Measurement checking and manual manipulation for the grading increment should be performed until the required curve lengths are achieved. If Optitex or TukaCAD is available, use the “measure and segment editor tool” to rectify the curve line grading. If Boke CAD is available, then there is no need to rectify the grading since it has an automatic grading system for higher precision grading. If that software is not available or we are not familiar with the described tools, then use the Pythagoras grad­ing system developed by the author. 5 Conclusion During the production, pattern pieces must be increased or decreased geometrically to create a complete range of sizes to produce clothing that fits various body types and sizes. Size specifica­tions vary slightly from manufacturer to manu­facturer and each company determines its own grade specifications for each size. Grading is still the most effective method to create multiple sizes from base size according to the size chart for the clothing production (even though the grading calculation can be slightly tricky and complex), since it is less time consuming and it supports downstream operations such as marker making and cutting. Computerised grading with different 2D and 3D CAD systems are not free from limita­tions even though they provide the most efficient method of pattern making, grading and marker making. 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