1/2023 • vol. 66 • 1-72 ISSN 0351-3386 (tiskano/printed) ISSN 2350 - 3696 (elektronsko/online) UDK 677 + 687 (05) http://www.tekstilec.si Casopisni svet/Publishing Council Barbara Simoncic, predsednica/President Katja Burger, Univerza v Ljubljani Manja Kurecic, Univerza v Mariboru Tatjana Kreže, Univerza v Mariboru Gašper Lesjak, Predilnica Litija, d. o. o. Nataša Peršuh, Univerza v LjubljaniPetra Prebil Bašin, Gospodarska zbornica Slovenije Melita Rebic, Odeja, d. o. o.Tatjana Rijavec, Univerza v LjubljaniHelena Zidaric Kožar, Inplet pletiva d. o. o. Vera Žlabravec, Predilnica Litija, d. o. o. Glavna in odgovorna urednica/ Editor-in-Chief Tatjana Rijavec Namestnica glavne in odgovorne urednice/Assistant Editor Tatjana Kreže Podrocni uredniki/Associate Editors Matejka Bizjak, Katja Burger, Andrej Demšar, Mateja Kos Koklic, Alenka Pavko Cuden, Andreja Rudolf, Barbara Simoncic, Dunja Šajn Gorjanc, Sonja Šterman,Brigita Tomšic, Zoran Stjepanovic Izvršna urednica za podatkovne baze/ Executive Editor for Databases Irena Sajovic Mednarodni uredniški odbor/ International Editorial Board Arun Aneja, Greenville, US Andrea Ehrmann, Bielefeld, DE Aleš Hladnik, Ljubljana, SI Petra Forte Tavcer, Ljubljana, SI Darinka Fakin, Maribor, SI Jelka Geršak, Maribor, SI Karl Gotlih, Maribor, SI Memon Hafeezullah, Shanghai, CN Abu Naser Md. 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. In the appendices written in Slovene language, are published technical and short articles about the textile-technology novelties from Slovenia and the world, articles on textile and clothing design, information about research projects etc. Dosegljivo na svetovnem spletu/Available Online at https://journals.uni-lj.si/tekstilec Tekstilec je indeksiran v naslednjih bazah/Tekstilec is indexed in Emerging Sources Citation Index – ESCI (by Clarivate Analytics): Journal Citation Indicator, JCI (Material Science, Textiles): 2021: 0.34 Leiden University's Center for Science & Technology Studies: 2021: SNIP 0.726 SCOPUS/Elsevier (2021: Q3, SJR 0.312, Cite Score 1.9, H Index 13) Ei Compendex DOAJ WTI Frankfurt/TEMA® Technology and Management/ TOGA® Textile Database World Textiles/EBSCO Information Services Textile Technology Complete/EBSCO Information Services Textile Technology Index/EBSCO Information Services Chemical Abstracts/ACS ULRICHWEB – global serials directory LIBRARY OF THE TECHNICAL UNIVERSITY OF LODZ dLIB SICRIS: 1A3 (Z, A', A1/2); Scopus (d) Revija Tekstilec izhaja štirikrat letno (štirje znanstveni zvezki in dve strokovni prilogi)/ Journal Tekstilec appears six times a year (four scietific issues and two proffessional supplements) Revija je pri Ministrstvu za kulturo vpisana v razvid medijev pod številko 583. 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VOLUME 66 • TEKSTILEC 1 2023 ISSN 0351-3386 (tiskano/printed) UDK 677 + 687 (05) SCIENTIFIC ARTICLES/ Znanstveni clanki 4 Prasanta Das, Manas Datta Roy, Subrata Ghosh Study on the Hydrophobicity and Antibacterial Activity of Silica Sol- Chitosan-HDTMS Treated Cotton Fabric Dipped in an Aquas Media Hidrofobnost in protibakterijska aktivnost bombažne tkanine, obdelane s silicijevim solom, hitozanom in HDTMS iz vodnega medija 18 Kashaf Kazmi, Zafar Javed, Muhammad Salman, Fatima Iftikhar, Naseer Ahmed, Jawad Naeem, Abdul Jabbar, Mehmet Karahan, M. Salman Naeem Optimization of Knitted Fabrics for better Thermo-Physiological Comfort by using Taguchi-based Principal Component Analysis Optimizacija toplotnega udobja pletiv z analizo glavnih komponent temeljeco na Taguchijevi metodi 31 Chandrasekaran P., Saminathan Ratnapandian Evaluation of Sawdust as a Sustainable Dye Source in Ethiopia Ocena žagovine kot vira trajnostnega barvila v Etiopiji 38 Scolastica Manyim, Ambrose K. Kiprop, Josphat Igadwa Mwasiagi, Achisa Cleophas Mecha Cleaner Production of Bioactive and Coloured Cotton Fabric Using Euclea Divinorum Dye Extract with Bio-Mordants Cistejša izdelava bioaktivnih in obarvanih bombažnih tkanin z uporabo izvlecka barvila Euclea Divinorum s pomocjo organske cimže 47 Ievgeniia Romaniuk, Olga Garanina, Yana Red’ko, Natalia Borshchevska, Serhiy Kamenets Serhiy, Kernesh Viktoriia Mathematical Modelling of the Parameters of Braided Textile Tapes Matematicno modeliranje parametrov za izdelavo prepletenih tekstilnih trakov 57 Göksal Erdem, Timo Grothe, Andrea Ehrmann Adhesion of New Thermoplastic Materials Printed on Textile Fabrics Adhezija novih termoplasticnih materialov, natisnjenih na tkaninah 64 Manar Y. Abd El-Aziz, Z. M. Abdel-Megied, K. M. Seddik Enhancement Reinforcing Concrete Beams Using Polypropylene Cord-Knitted Bars Izboljšanje ojacitve betonskih nosilcev s pletenimi kompozitnimi palicami iz polipropilenskih vrvic Tekstilec, 2023, Vol. 66(1), 4–17 | DOI: 10.14502/tekstilec.66.2022094 Prasanta Das, Manas Datta Roy, Subrata Ghosh Dr. B. R. Ambedkar National Institute of Technology, Department of Textile Technology, Jalandhar, Punjab-144027 Study on the Hydrophobicity and Antibacterial Activity of Silica Sol-Chitosan-HDTMS Treated Cotton Fabric Dipped in an Aquas Media Hidrofobnost in protibakterijska aktivnost bombažne tkanine, obdelane s silicijevim solom, hitozanom in HDTMS iz vodnega medija Original scientific article/Izvirni znanstveni clanek Received/Prispelo 11-2022 • Accepted/Sprejeto 1-2023 Corresponding author/Korespondencni avtor: Assoc. Prof. Dr. Manas Datta Roy Phone: +91 9417361680 Email: roymd@nitj.ac.in ORCID ID: 0000-0003-2751-9518 Abstract A hydrophobic surface with an antibacterial property has numerous uses, including self-cleaning, anti-sticking, anti-contamination, sports apparel, and wound healing/implant materials. The durability of the coating in an aquas media (pH 7.4) is a vital requirement for use in technical textile sectors, particularly in medical applica­tions. In this study, we used silica sol, chitosan and hexadecyltrimethoxysilane (HDTMS) to create exceptionally hydrophobic surfaces with antibacterial properties on cotton fabrics. First, cotton fabric was treated with silica sol, which was produced by the hydrolysis and condensation of tetraethoxysilane (TEOS) in an alkaline environ­ment. After that, chitosan was applied on the silica sol-treated fabric to add an antibacterial characteristic. The silica sol-chitosan-treated fabric was then given a hydrolysed HDTMS treatment to give a highly hydrophobic property. The hydrophobicity was assessed by measuring the water contact angle, while the AATCC-147 test protocol was used to assess the antibacterial property. The developed fabric exhibited a strong hydrophobic property. The fabric samples were immersed in an aquas media for 30 days to assess the coating durability by observing changes in hydrophobicity and anti-bacterial activity in terms of the zone of inhibition (ZOI). After 30 days of immersion in the aquas media, it was observed that the contact angle decreased from 151.7° to 129.5°, and the ZOI increased from 1 mm to 5 mm, which indicates an increase in anti-bacterial activity in relation to time of immersion. The wicking characteristics of coated and uncoated fabrics were also measured to determine how coating affects the wicking behaviour of fabric. EDS was performed to observe the coating stability for coated-dipped fabric samples after 30 days. SEM analysis was performed to examine the surface morphology, while FTIR was used to determine the surface functional groups after coating and changes after dipping in the aquas media. The developed hydrophobic cotton fabrics with anti-bacterial properties may help in the fabrication of natural biomaterials and other technical textile products. Keywords: cotton, hydrophobic, antibacterial, silica sol, chitosan Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. Izvlecek Hidrofobna površina s protibakterijskimi lastnostmi ima številne uporabne lastnosti, vkljucno s samocistilnimi, proti sprijemanju in zamazanju, ki so pomembne za športna oblacila in materiale za celjenje ran ter vsadke. Obstojnost obdelave v vodi (pH 7,4) je bistvena zahteva za tehnicne tekstilije, med njimi zlasti za medicinske tekstilije. Za izdelavo izjemno hidrofobne površine s protibakterijskimi lastnostmi na bombažni tkanini je bil v tej raziskavi uporabljen silicijev sôl, hitozan in heksadeciltrimetoksisilan (HDTMS). Najprej je bila bombažna tkanina obdelana s silicijevim sôlom, ki nastane s hidrolizo in kondenzacijo tetraetoksisilana (TEOS) v alkalnem okolju. Na tako obdelano tkanino je bil v nas­lednjem koraku za dosego protibakterijskih lastnosti nanesen hitozan. Sledila je naknadna obdelava s hidroliziranim HDTMS za dosego visoke hidrofobnosti. Hidrofobnost je bila ocenjena z merjenjem sticnega kota vode, protibakterijske lastnosti pa so bile dolocene z merjenjem cone inhibicije (ZOI). Obdelana tkanina je izkazala visoko hidrofobnost. Za oceno obstojnosti obdelave sta bili hidrofobnost in cona inhibicije (ZOI) doloceni tudi na vzorcih, ki so bili za 30 dni potopljeni v vodni medij. Po 30 dneh potopa vzorcev v vodni medij se je sticni kot vode zmanjšal s 151,7° na 129,5°, ZOI pa se je povecal z 1 mm, na 5 mm, kar kaže na povecanje protibakterijske aktivnosti s casom potopitve. Izmerjena je bila tudi vpojnost obdelanih in neobdelanih tkanin. S pomocjo analize EDS je bila proucena stabilnost obdelave na vzorcih tkanin. Analiza SEM je bila izvedena za proucevanje morfologije površine, FTIR pa je bil uporabljen za dolo-citev funkcionalnih skupin na površini obdelanih vzorcev in kemijskih sprememb površine po namakanju v vodnem mediju. Razvoj hidrofobne bombažne tkanine s protibakterijskimi lastnostmi je lahko v pomoc pri izdelavi naravnih biomaterialov in drugih izdelkov iz tehnicnih tekstilij. Kljucne besede: bombaž, vodoodbojnost, protimikrobnost, silika, hitozan 1 Introduction Today, fabric made of natural fibres, such as cotton with hydrophobic and anti-bacterial properties, has many applications in different technical textile fields, in particular medical, industrial, military use, etc. The number of uses of hydrophobic sur­faces in the technical field is increasing due to their self-cleaning, anti-sticking and anti-contamination properties [1, 3]. Natural textile materials, such as cotton, represent an excellent media for bacteria. Natural cotton fibres provide nutrients, oxygen and moisture to bacteria for their growth and multi­plication [4-8]. Moreover, fabrics made of natural fibre yarn contain micropores inside the three-di­mensional structure of the yarn. These micropores increase the chance of bacteria colony formation because bacteria can easily hide and proliferate in­side the micropores [9-12]. The unfavourable tissue reaction of cotton biomaterial is higher than that in synthetic fibres, which declines after about a week [13]. This unfavourable tissue reaction is caused by the high hydrophilicity of cotton fibres because, after being implanted inside the body, their hydro­philic surfaces bind plasma proteins, such as coagu­lation factor XII, HMWK and prekallikrein [14, 15]. However, this issue can be avoided by generating surfaces that are extremely hydrophobic and have a contact angle of more than 120° [15-17]. Therefore, cotton fabrics require a hydrophobic coating with antibacterial properties for its use in medical, in­dustrial, military and other similar purposes. The hydrophobicity or hydrophilicity of a surface determines how liquids will interact with it. A hy­drophobic surface can be achieved by changing the surface topology (roughness), by reducing re­action surface energy or through both [1, 18, 19]. The degree of wettability of a material can be de­termined by evaluating the water contact angle (WCA) between the solid and liquid phases. Based on the angle of contact between water droplets and the surface, a substance is categorized as either superhydrophobic (WCA > 150°), hydrophobic (90° < WCA < 150°) or hydrophilic (WCA < 90°) [1, 20]. Various methods are available for the fabri­cation of superhydrophobic surfaces on cotton, such as sol-gel, layer-by-layer deposition, plasma etching, chemical vapour deposition and nanoparticle depo­sition [18, 21-23]. Apart from other techniques, the sol-gel method, through the use of silica nanopar­ticles, has drawn the attention of researchers due to its biocompatibility, eco-friendliness and non-tox­icity properties, and non-fluorinated nature with good experimental reproducibility [24, 25]. Zare et al. reported that silicone is extremely biocompatible when it interacts with host tissues because silicone is hydrophobic and has a low surface tension. It has good hemocompatibility and lowers the risk of en­crustation when it comes into contact with body fluids [26]. Antibacterial properties on natural fibres can be developed by using natural, organic and inorgan­ic antibiotics. Well-known natural antibiotics are chitosan and chitosan derivatives, while popular organic antibiotics are quaternary ammonium salts, guanidine, zwitterionic betaine compounds, pep­tide, etc. Similarly, inorganic antibiotics include Zn nanoparticles, Ti nanoparticles, Ag nanoparticles, etc. [27]. The most abundant polysaccharide found in nature is chitosan. Chitosan is a deacetylated derivative of the polysaccharide chitin, which is mostly found in crustacean exoskeletons and has received a lot of interest because of its versatility, non-toxicity, biodegradability and antibacterial characteristics [28-30]. Therefore, in this research, a hydrophobic surface with an antibacterial property was developed on scoured cotton woven fabric by using silica sol, HDTMS and chitosan. The silica sol was formed with the help of the sol-gel technique through hy­drolysis and the condensation of tetraethoxysilane (TEOS) in alkaline conditions. First, the scoured fabric was treated with silica sol. The silica-sol treat­ed cotton fabric was then coated with a chitosan solution to achieve an antibacterial property. After that, the chitosan-treated fabrics were coated with hydrolysed hexadecyltrimethoxysilane (HDTMS) to develop a highly hydrophobic surface through a reduction in surface energy. Coating durability in an aquas media (pH 7.4) is im­portant for application in medical use because post operative wounds generally take four to six weeks to heal [31]. For this reason, textile materials that are used for wound healing/implant materials will be in contact with physiological body fluid for a longer period (at least 30 days), during which time the av­erage pH of physiological body fluid remains at 7.4 [32]. There is limited work on the exposure of silica sol, chitosan and HDTMS coated fabric in an aquas media (pH 7.4) for 30 days and its impacts on hy­drophobicity and antibacterial activity. The aim of this study was thus to develop a non-tox­ic, biodegradable hydrophobic fabric with anti-bac­terial properties by using silica sol, chitosan and HDTMS, and to then study changes in the anti­bacterial activity and hydrophobicity of the surface when it is dipped in an aquas media (pH 7.4). 2 Experimental 2.1 Materials The study was conducted using cotton woven fabric that was obtained from a local industry. The details of the fabric are presented in Table 1. Table 1: Fabric details Property Value Linear density of cotton warp (tex) 20.2 Linear density of cotton weft (tex) 30.1 Weave structure plain Fabric areal density (g/m2) 110 Fabric density (EPCM × PPCM) (EPI × PPI) 26×17 (66 × 43) The chemicals used for this study were TEOS (tetra­ethoxysilane), ethanol, NH4OH, HDTMS (hexadec­yltrimethoxysilane), chitosan (deacetylation degree of chitosan was = 75.00%) and acetic acid. All the chemicals were purchased from Sigma-Aldrich. The cotton fabric was first de-sized using an acid de-sizing method to remove sized material and then scoured using sodium hydroxide (NaOH) to remove oily substances. 2.2 Methods 2.2.1 Synthesis of silica sol using sol-gel method The alkaline hydrolysis and condensation of tetra-ethoxysilane (TEOS) in ammonium hydroxide (NH4OH) and ethanol solution was used to make silica sol. A total of 5 ml of ammonium hydrox­ide (NH4OH) solution was slowly added, with continuous stirring, into 100 ml of ethanol at 60 °C. The stirring was continued for 30 minutes. Subsequently, 6ml of tetraethoxysilane (TEOS) was slowly added into the solution, drop by drop, and stirring was carried out for 90 minutes to produce the silica solution. 2.2.2 Chitosan solution preparation Chitosan solution was prepared by dissolving 2g of chitosan into 1000 ml of 2% acetic acid solution. The solution was then stirred for 2 hours. 2.2.3 Hexadecyltrimethoxysilane (HDTMS) hydration Hexadecyltrimethoxysilane (HDTMS) (0.75 % V/V) was slowly added (drop by drop) into ethanol to make the solution. The pH of the solution was main­tained at 5.0 by applying acetic acid. Thereafter, the solution was stirred for 60 minutes to make an alkylsilanol solution. 2.2.4 Treatment of fabric The scoured cotton woven fabric samples were dipped for 20 minutes in a silica sol solution. The samples were then padded using a laboratory pad-der with a wet pickup of 70% to 80% and dried for three minutes at 80 °C [33]. After that, the cotton fabrics were padded with a 2% chitosan solution. The padded fabrics were then dried at 80 °C for five minutes and cured at 140 °C for three minutes [34]. Subsequently, the cured samples were again dipped into HDTMS alkylsilanol solution for one hour and followed by drying at room temperature. Finally, the samples were cured at 120 °C for one hour [33]. The result was coated hydrophobic fabrics. The durability of fabric coating was studied by immersing the fabrics in an aquas media (pH 7.4) for three days, 10 days and 30 days respectively. Changes in the contact angle and anti-bacterial property of the different dipped fabrics were then measured. The different fabric samples, before and after coating, are presented in Table 2. Moreover, the aquas media (pH 7.4) was prepared using dis­tilled water and sodium carbonate. Sodium car­bonate was added to distilled water to maintain the pH of media at 7.4. Table 2: The different fabric samples before and after coating Seq. no. Sample code Fabric 1 C1 Untreated cotton fabric 2 C2 Coated fabric (silica sol + chitosan (0.2%) + 0.75% (V/V) HDTMS) 3 C3 Dipped in aquas media for 3 days 4 C4 Dipped in aquas media for 10 days 5 C5 Dipped in aquas media for 30 days 2.3 Characterization technique used Developed fabrics were characterized using the fol­lowing techniques: – contact angle measurement The contact angles of different types of fabrics were measured to determine the surface wettabili­ty of the untreated, treated and dipped fabric. The contact angle as measured by using a Drop Shape Analyzer, Kruss, Germany. – determination of wicking properties A published method [35] was used to assess the wicking effect of coated and uncoated fabric. Fabric measuring 200 mm × 25 mm was cut for the pur­pose of evaluating wicking ability. A clamp was then equipped with a stainless-steel scale. After that, a glass reservoir was added to the frame’s base. The fabric was also carefully controlled to avoid bending around its axis. The rise of liquid through the yarn of fabric was observed. The test was termi­nated when there was no indication that any liquid had been absorbed. – characterization of anti-bacterial property The antibacterial efficiency of coated fabric was eval­uated using the AATCC-147 test protocol with E. coli bacteria [6]. A culture media was prepared using agar-agar (2%) and Luria broth (2%) in distilled water. The petri dish, tip, forceps, L rod and media were then sterilized in an autoclave for 15 minutes at 120 °C and a pressure of 1.05 kg/cm2. The cultured media poured into petri dishes, and the petri dish, L rod, forceps, 1 ml tip box, pipette and fabric were again sterilized us­ing UV sterilization for 15 minutes. A total of 100 µl of bacteria were dispersed in an agar media using an L rod after UV sterilization. The fabric was then placed in the centre of the petri dishes. The petri dishes were covered with paraffin paper. After this, the petri dishes were incubated for 24 hours at 37 °C. The zone of in­hibition was determined to test antibacterial activity. – scanning electron microscopy (SEM) analysis The surface of the untreated and treated fabric was examined using a ZEISS Sigma 500 VP scanning electron microscope (Germany). Since cotton fibre is nonconductive, the fabric was coated with a thin film of gold before SEM measurements. – fourier infrared spectroscopy (FTIR) analysis Changes in the functional groups of untreated, treated and dipped fabric were observed using a BUKER ALPHA II FTIR spectrometer (Germany). The results were taken in a wavelength of 600 nm to 4000 nm. – energy dispersive X-ray spectroscopy (EDS) analysis EDS analyses of the uncoated, coated and dipped samples were performed to observe coating stability using an EDS, AMETEK ELECT PLUS device. – measurement of tensile strength The tensile behaviour of the yarns unravelled from coated fabric and from coated fabric dipped for 30 days were assessed using a Tinius Olsen Universal Testing Machine (UTM).The standard test norm ASTM D2256/D2256M 21 was applied to determine the tensile strength of the unravelled yarn. – measurement of tear strength The tearing strength of the uncoated and coated fabric was evaluated using the tongue (single rip) procedure (Constant Rate of Extension Tensile Testing Machine) according to standard test norm ASTM D2261. – measurement of stiffness The stiffness of the uncoated and coated fabric was measured according to the ASTM D1388-18 stand­ard protocol. 3 Result and discussion The procedure for forming a hydrophobic sur­face with antibacterial abilities on scoured cotton woven fabric is presented in section 2.2, while the potential chemical reactions are shown in Figure 1. Figure 1a illustrates how silica sol binds to cot­ton fabric through a condensation reaction be­tween the hydroxyl groups of cotton and silica sol. Similar observations have also been document- Figure 1: Potential reaction between: a) cotton fibre and silica sol; b) silica sol and chitosan; and c) chitosan and HDTMS ed in available literature [33, 36]. The structure of chitosan contains hydroxyl and amine groups. Silica sol’s hydroxyl group and chitosan’s hydroxyl group established a covalent link, resulting in the silica nucleation. Although the amine group can­not create covalent bonds, it serves as an excellent hydrogen bonding partner. As a result, a hydrogen bond formed with the silica sol’s hydroxyl group, as seen in Figure 1b, while a similar reaction was also observed by Budnyak [37]. Similar to the chitosan bonds with silica sol, HDTMS attached to chitosan through covalent and hydrogen bonds, as seen in Figure 1c [37]. FTIR spectra can be used to explain the binding mechanism. Figure 2 shows the FTIR spectra of ma­terials that were uncoated, coated and dipped for 30 days. For hydrophilic groups (-OH groups and NH2 groups), spectra in the range of 3200–3400 cm-1 was observed [38, 39]. After coating, there was a drop in the absorbance of spectra in the range of 3200–3400 cm-1. This decrease may be the result of a condensation reaction among the hydroxyl groups of cotton and silica-sol, silica sol and chitosan, and chitosan and HDTMS, although the peak of -OH is still present even after coating, which indicates the presence of some hydroxyl group on the fabric sur­face even after HDTMS coating. The peak intensity in the range of 3200–3400 cm-1 was again raised af­ter dipping the fabric in an aquas media for 30 days. This may be due to the breaking of hydrogen bond between hydroxyl group of HDTMS and NH2 of chitosan, which results in an increase in hydrophilic groups (-OH and -NH2). The breaking of bonds may be due to the prolonged direct contact of the sam­ples with water. In water, hydrogen bonds break eas­ily [40]. In addition, the unreacted OH group pres­ent on surface of coated fabric may absorb water molecules physically or by hydrogen bond [41, 43]. Additionally, the spectra between 1600 cm-1 and 1700 cm-1 appeared for the sample dipped for 30 days, while the peak between 1600 cm-1 and 1700 cm-1 normally appeared for amine groups [34]. Moreover, the peaks in the range of 1600 cm-1 to 1700 cm-1 are further evidence that the hydrogen bond between HDTMS and chitosan were broken, exposing amine groups. The absorption Si-O-Si spectra of silica sol and HDTMS, and the C-O spec­tra of chitosan in the range of 1100-1000 cm-1 ap­pear overlap with the untreated cotton C-O spectra (cellulosic bond), which is similar to the results of previously reported research [33, 43]. EDS analyses of uncoated sample C1, coated sample C2 and sample C5 dipped for 30 days were also per­formed to observe the stability of coating, and are presented in Figure 3. Only C and O atoms were de­tected on the surface of uncoated sample, while C, O, N and Si were detected for the coated sample and sample dipped for 30 days. Moreover, the presence a)b) c) Figure 3: EDX spectra of: a) uncoated sample C1; b) coated sample C2; and c) sample C5 dipped for 30 days of N atoms and Si atoms on the surface after 30 days of dipping confirmed coating stability. The hydrophobicity of the fabric surface was deter­mined by measuring the contact angle of the sam­ple surface using a drop shape analyser. Table 3 and Figure 4 present the contact angle values for fabrics C1, C2, C3, C4 and C5. Table 3 shows that the con­tact angle of untreated cotton fabric was not meas­urable because the water droplet vanished imme­diately from the fabric’s surface as soon as contact with the fabric surface was made. This may be due to the large number of hydrophilic groups present on cotton fibres, fine pores in the yarn and water wicking through the yarn’s capillaries, which are ul­timately responsible for the extreme hydrophilicity of untreated fabric [44]. It is evident that after be­ing treated with silica sol, chitosan and HDTMS the water contact angle of the coated cotton surface C2 reached a value of 151.7°, which indicates superhy­drophobic nature of the surface [21, 45]. Contact angle 180 160 140 120 100 80 60 40 20 0 Fabric C1 Fabric C2 Fabric C3 Fabric C4 Fabric C5 (Untreated) (Coated) (3 Days (10 Days (30 Days dipped) dipped) dipped) Figure 4: Water contact angle of untreated, treated and dipped cotton fabric Table 3: Water contact angle of untreated, treated and dipped cotton fabric Sample type Contact angle (°) C1 Not measurable C2 151.7 C3 138.0 C4 137.4 C5 129.5 The sharp rises in contact angle may be due to the alteration of surface roughness of the fabric follow­ing the application of silicon sol, and a reduction in the surface energy of the cotton fabric surface due to subsequent treatment with HDTMS. Therefore, the combined effects of roughness and reduced sur­face energy lead to a highly hydrophobic surface [6, 33, 46]. The original tracing obtained from the drop shape analyser are presented in Figure 5 for the fabric surfaces of samples C2, C3, C4 and C5. It is evident from Figures 4 and 5 that the contact angle decreased significantly after three days of dipping in an aquas media i.e. 151.7° to 138°. Thereafter, the rate of reduction in the contact angle is relatively lower for the next 30 days. The contact angle was decreased after dipping in an aquas media. There are two probable reasons for the entire surface phe­nomena in this respect. First, the decrease in the contact angle after dipping was probably due to the cracks in the silica coating on the cotton fibre sur­face caused by the swelling of cotton. This is sup­ported by earlier studies, which reported that the contact angle decreased after 25 to 30 washings, and the reduction may be due to cracks in silica film on the fibre surface caused by the swelling of cotton [33, 47]. The second reason is the absorption of wa­ter molecules by OH groups present on the coated fabric C2 fabric C3 fabric C4 fabric C5 151.7° 138° 137.4° 129.5° a) b) c) d) Figure 5: Contact angle of: a) treated sample; b) sample dipped for three days; c) sample dipped for 10 days; and d) sample dipped for 30 days surface during long-term direct contact with water [41, 42]. Furthermore, any material intended for use as a biomaterial must be biocompatible and must also have a contact angle greater than 120° for at least a week after implantation in order to stop this tissue reaction [13, 17]. This is because tissue reac­tivity normally subsides after about a week [13]. The developed cotton fabric exhibited a contact angle of above 120° even after 30 days of dipping in an aquas media. It is thus possible to use this developed fab­ric as a wound healing/implant material. The wicking effect of uncoated and coated cotton fabrics (C1 and C2, respectively) were observed by measuring the wicking height. Figure 6 and Table 1 0 Fabric C2 Fabric C3 Fabric C4 Fabric C5 (Coated) (3 Days (10 Days (30 Days dipped) dipped) dipped) Figure 7: Zone of inhibition (ZOI) of treated and dipped fabric ZOI (mm) 3 2 [50]. As a result, the obstructions limited the cap­illaries’ ability to work in coated fabrics. Moreover, the blocked pore/capillaries can be useful for med­ical applications because the bacteria can not hide and grow inside the yarn structure of coated fabrics where the pores are blocked. 6 5 4 4 show the wicking height of cotton fabrics that are uncoated (C1) and coated (C2), respectively. It is ev­ident from Figure 6 and Table 4 that cotton fabrics that are not coated exhibit wicking behaviour and have a wicking height of 8 cm ± 1 cm. This might be caused by the capillaries that exist within the struc­ture of the yarn (intra-yarn spaces) and between the yarns (inter-yarn spaces) [48, 49]. Conversely, the cotton fabric treated with silica sol, chitosan and HDTMS displayed zero evidence of wicking. Table 4: Wicking performance of uncoated and coated cotton fabric Fabric type Maximum wicking height (cm) Uncoated cotton fabric sample (C1) 8 ± 1 Coated cotton fabric sample (C2) 0 The anti-bacterial activity of fabric C2, C3, C4 and C5 were measured with help of the agar-agar dif­fusion test method using E. coli. The zone of inhi­bition (ZOI) was calculated for all the samples and plotted in Figure 7. It was observed that the ZOI of fabric C2 (treated) was relatively low, at around 1 mm, while the ZOI increased in the case of dipped The coating on the fabric surface developed an im-fabric C3, fabric C4 and fabric C5 relative to treated permeable barrier by blocking the pores and cap-fabric C2. The ZOI of coated fabric sample C2 and illaries inside the yarns and the fabric’s structure dipped sample C3 are also shown in Figure 8. The a) b) Figure 6: Wicking of: a) uncoated cotton fabric (sample C1); and b) coated cotton fabric (sample C2) a) b) Figure 8: ZOI of: a) treated fabric C2; and b) dipped fabric C3 increase in the ZOI of the dipped fabric samples (C3, C4 and C5) may be due to the breakage of the hydrogen bond between the -NH2 of chitosan and the -OH of HDTMS. The hydrogen bond breaks due to long-term direct contact with water. Hydrogen bonds break easily in water [40]. The breakage of the hydrogen bond thus leads to the exposure of the NH2 of chitosan. The exposure of NH2 after dipping was also confirmed by FTIR, which showed the in­creased intensity of the NH2 spectra at 1648 cm-1 (Figure 2). Moreover, when NH2 was exposed to an aquas media, it became cationic in nature and thus killed bacteria [34]. However, both the coated fabric sample (C2) and dipped fabric samples (C3, C4 and C5) demonstrat­ed antibacterial activity due to the presence of chi-tosan. There are two types of proposed mechanisms by which chitosan exhibits antibacterial property. In one method, the polycationic nature of the ami­no group (NH2) in chitosan interferes with the me­tabolism system of bacteria by attaching to the cells of bacteria. In the other method, the chitosan binds with DNA to inhibit the synthesis of mRNA [34, 51]. Hence, the improved antibacterial activity of coated samples after dipping in an aquas media may be useful in addressing the antibacterial require­ments of biomaterial [9-12]. The surface morphology of textile fabrics before and after coating are observed by using a Leica image analyser and SEM. The Leica image of fab­ric before and after coating are shown in Figure 9. The SEM images of uncoated sample C1, coated sample C2 and dipped sample C5 are shown in Figure 10. Higher roughness was observed on the SEM image of coated cotton fabrics C2 than on the untreated cotton fabric C1, which confirmed the attachment of chitosan and silicon nanopar­ticles. Moreover, the roughness of dipped sample C5 increased relative to coated sample. This may be due to the cracks in silica coating caused by the swelling of fibre during long-term direct contact with water [33]. a) b) Figure 9: Leica images of: a) untreated fabric C1; and b) treated fabric C2 a) b) c) d) e) f) Figure 10: SEM images of: a) untreated fabric C1; b) untreated fabric C1 with higher magnification; c) treated fabric C2; d) treated fabric C2 with higher magnification; e) dipped fabric C5; and f) dipped fabric C5 with higher magnification The tensile strength of yarn unravelled from treated Table 5: Tensile strength of coated sample (C2); and fabric sample C2 and sample C5 dipped for 30 days sample (C5) dipped for 30 days (yarn) was measured and is presented in Table 5. After 30 days of dipping, the yarn’s tensile strength de­creased by 6.4%. The degradation of cotton fibre in the aquas media may be responsible for this drop in Sample type Breaking force (N) C2 3.1 ± 0.3 C5 2.9 ± 0.4 tensile strength. The tearing strength of uncoated fabric sample C1 and coated fabric sample C2 were evaluated and are presented in Table 6. It is evident from Table 6 that tearing strength decreased by about 2% after coat­ing. Therefore, coating does not have a significant effect on tearing strength (p > 0.05). Table 6: Tearing strength of uncoated and coated sample Type of sample Average tearing strength (N) Uncoated fabric sample C1 15.34 Coated fabric C2 15.08 The stiffness of uncoated fabric sample C1 and coated fabric sample C2 was observed by measur­ing the bending length and is presented in Table 7. The bending length increased by 10% after coating. Therefore, the stiffness of the fabric is only margin­ally affected by coating (p > 0.05). Table 7: Bending length of uncoated and coated sample Type of sample Average bending length (cm) Uncoated fabric sample C1 1.8 ± 0.1 Coated fabric sample C2 2.0 ± 0.1 4 Conclusion The developed cotton fabric exhibited a highly hydrophobic nature when coated with silica sol, chitosan and HDTMS, while the value of the con­tact angle of the treated fabric was around 151.7°. However, after three, 10 and 30 days of dipping in an aquas media, the contact angle decreased to 138°, 137.4° and 129.5° respectively, meaning a highly hydrophobic nature was maintained even after 30 days. Moreover, the treated fabric indicates zero wicking due to the blocking of pores. In terms of antibacterial activity, coated fabric demonstrated a low antibacterial activity with a ZOI of approxi­mately 1 mm. However, the antibacterial activity was enhanced when the fabric was dipped in an aq­uas media for three, 10 and 30 days, with a ZOI of 5 mm. 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Research Journal of Textile and Apparel, 2012, 16(1), 77–85, doi: 10.1108/RJTA-16-01-2012-B008. Tekstilec, 2023, Vol. 66(1), 18–30 | DOI: 10.14502/tekstilec.66.2022024 Kashaf Kazmi,1 Zafar Javed,1 Muhammad Salman,2 Fatima Iftikhar,2 Naseer Ahmed,3 Jawad Naeem,2 Abdul Jabbar,2 Mehmet Karahan,4 M. Salman Naeem1 1 National Textile University, School of Arts and Design, Department of Design, Sheikhupura Road, Faisalabad - 37610, Pakistan 2 National Textile University, School of Engineering and Technology, Department of Textile Engineering, Sheikhupura Road, Faisalabad - 37610, Pakistan. 3 National Textile University, School of Science, Department of Applied Science, Sheikhupura Road, Faisalabad - 37610, Pakistan 4 Bursa Uludag University Vocational School of Technical Sciences, Görükle 16059 Nilüfer, Bursa, Turkey. Optimization of Knitted Fabrics for better Thermo-Physiological Comfort by using Taguchi-based Principal Component Analysis Optimizacija toplotnega udobja pletiv z analizo glavnih komponent temeljeco na Taguchijevi metodi Original scientific article/Izvirni znanstveni clanek Received/Prispelo 4-2022 • Accepted/Sprejeto 1-2023 Corresponding author/Korespondencni avtor: Mehmet Karahan E-mail: mkarahan@uludag.edu.tr ORCID ID: 0000-0003-3915-5598 Abstract The water, air permeability and thermal resistance of fabrics are important attributes that have a significant impact on the thermal comfort properties of sportswear fabrics in different environmental conditions. In this work, terry and fleece fabrics were developed by varying the fibre content and mass per unit area of fabrics. Moreover, the thermo-physical properties of the developed fabrics, including air permeability, water vapor permeability and thermal resistance, were analysed before and after washing. The multi-response optimization of the thermal comfort properties of knitted fabrics was performed using principal component analysis (PCA) and the Taguchi signal-to-noise ratio (PCA-S/N ratio) to achieve optimal properties. It was determined that the selected parameters (fabric type, finishing, fibre content and fabric mass per unit area) had a significant effect on the thermal comfort properties of knitted fabrics. The PCA analysis showed that 100% cotton terry fabric before washing with an aerial weight of 220 g/m2 had higher air and water vapor permeability value, but a lower thermal resistance value. Keywords: fibre blends, fabric construction, heat and transmission properties of fabric, statistical analysis Izvlecek Prepustnost za vodo, zracna prepustnost in toplotni upor pletiv pomembno vplivajo na toplotno udobje športnih oblacil v razlicnih okoljskih razmerah. V tej raziskavi so bila izdelana frotirna in flisna pletiva s spreminjanjem razmerja bombaža in poliestrskih vlaken ter spreminjanjem plošcinske mase. Pred pranjem in po njem so bile pletivom ana­lizirane zracna prepustnost, prepustnost vodne pare in toplotni upor. Vecodzivna optimizacija lastnosti toplotnega udobja pletiv je bila izvedena s pomocjo analize glavnih komponent (AGK) in Taguchijevega razmerja signal/šum Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. (razmerje AGK-S/N) za optimalne lastnosti. Ugotovljeno je bilo, da so izbrani parametri (vrsta pletiva, plemenitenje, vsebnost vlaken in plošcinska masa pletiva) pomembno vplivali na lastnosti toplotnega udobja pletiv. Analiza glavnih komponent je pokazala, da je neoprano 100-odstotno bombažno frotirno pletivo s plošcinsko maso 220 g/m2 doseglo najvišje vrednosti zracne prepustnosti in prepustnosti vodne pare in najnižji toplotni upor. Kljucne besede: mešanice vlaken, konstrukcija pletiva, toplota, prepustnost, statisticna analiza 1 Introduction Knitted fabrics are widely acceptable textiles be­cause of their good thermal comfort properties, availability in a wide range of products, and simple and low-cost manufacturing techniques [1]. These fabrics provide better freedom in body movements because their structure offers greater flexibility than woven fabrics. Knitted fabrics not only give the wearer a comfortable feeling during use, but also enable the designer to give a more fit look, which makes them ideal for use in sportswear, underwear and casual wear. Other characteristics that make knitted fabrics attractive are their moisture absorp­tion and transmission ability and good handling properties. Apart from development and advancement in the field of textiles, the rise of consumer aware­ness through different sources (social media, fash­ion shows and marketing campaigns by different brands), the dynamics of the clothing/fashion in­dustry are changing at a rapid pace. Currently, clothing brands focus not only on new styles, but also target different aspects of clothing comfort [1]. Although comfort and aesthetics play an important role in the selection of a garment, comfort is be­coming increasingly important because of different external factors (moisture, wind, temperature, and social and cultural influences) and internal factors (level of activity). In other words, clothing comfort can be defined as the absence of discomfort or dis­pleasure. Clothing comfort can be categorized in different ways, such as thermo-physiological, sen-sorial, psychological and garment fit comfort [2]. Thermo-physiological comfort deals with heat and moisture transport properties through clothing, and depends on different factors such as fibre type, fibre content, shape of fibre, yarn characteristic, type of fabrication techniques and finishing treat­ments, as well as garment fit and size [3]. The air permeability (AP) of a fabric can be defined as the amount of air that passes through a fabric of 100 mm2 in one second while maintaining a water head pressure difference of 10 mm [4]. The air per­meability of fabric indicates how fabric will allow the movement of air through it [5, 6]. The air perme­ability of fabric relates to thermo-physiological com­fort in different ways: air permeable material is like­ly to transmit water either in liquid or vapor form, while the thermal resistance of fabric is also closely related to the air trapped in the fabric structure. An earlier study [5] showed that increasing the porosi­ty and stitch length of cotton fabrics resulted in an improvement in the thermal insulation properties of knitted fabrics. Thermal conductivity decreases with an increase in the loop length/stitch length of knitted fabric. It is understood that the thermal con­ductivity value of fibres is higher than the thermal conductivity of the entrapped air layer. The lower thermal conductivity of knitted fabrics from longer loop length or stitch length is the result of the high porosity of fabric [7, 8]. Fayala et al. further conclud­ed that in cellulosic fabrics the surface characteris­tics and capillary structures of yarns have a signif­icant effect on the thermal and air permeability of fabrics. Not only fibre content but also the fibre fine­ness, linear density of yarn, size and shape of pores also contribute significantly to the air permeability and thermal resistance of fabrics [9, 10]. In another study, Saha et al. [11] showed that fabric from 100% cotton demonstrated higher air permeability than other fabrics when the proportion of cotton was de­creased and polyester content was increased because cotton has more amorphous regions than synthetic fibres, resulting in increased porosity. The determination of evaporative heat loss under iso-thermal conditions is known as water vapor re­sistance (Ret). Water vapor resistance is determined as the differentiation of water vapor pressure be­tween the two faces of a textile substrate divided by the resultant evaporative heat flux per unit area in the direction of the gradient. This capability of fab­ric or clothing to transmit water vapor plays a very important role in the thermo-physiological comfort of clothing. When the body stops sweating, the tex­tile substrate next to the skin releases water vapors in the external environment to create a dry micro-climate between the skin and textile fabric [11, 12]. Thermal resistance (Rct) can be defined as the temperature difference between the two fac­es of a material divided by the resultant heat flux per unit area in the direction of the gradient. The thermal resistance of fabric is directly relat­ed to fabric density and thickness. When fabric density increases, the thickness of fabric also in­creases due to increased air gaps in the fabric struc­ture, which ultimately increases thermal resistance [13]. Bivainyte et al. [14] investigated the impact of a double-layer knitted structure on the thermal trans­mission characteristics of fabric by using different types of materials, such as cotton, polyester, polyam­ide and polypropylene, and found that thermal re­sistance in double-layered knitted fabrics increases with an increase in the thickness of fabric. Due to the thicker fabric structure, more air is trapped, so the pores present within the fabric structure decrease, which ultimately increases thermal insulation. In another study, Saha et al. [11] used 100% cotton, 80% cotton/20% polyester and 60% cotton/40% polyes­ter fibres content in fleece fabric, and found that the maximum thermal insulation was achieved by us­ing 80% cotton/20% polyester because the polyester content made the fabric structure compact due to the presence of more crystalline regions than in 100% cotton fabric. Havenith [15] explained that heat in­sulation and water vapor resistance were increased with an increase in material thickness because of more air trapped in the thick fabric structure. A sim­ilar increase in the thermal resistance of fabric was found after washing, which resulted in more air trap­ping because the structure of fabrics became more compact after washing [16]. Jamshaid et al. investigated thermal comfort prop­erties such as air permeability, thermal resistance and moisture management for both knitted and woven denim fabric. It was determined that knitted denim fabric demonstrated better thermal resist­ance, moisture management and air permeability values than woven knitted fabric [17]. Akbar et al. [18] studied the comfort properties of knitted den­im. The samples of flax and polyester blends exhib­ited superior results in terms of air permeability and moisture management compared to samples made from polypropylene and cotton blends. Das et al. [19, 20] conducted a study on the development of advanced knitted structures for the base layer clothing of glacier regions. It was determined that the knitted structure developed from a blend of polyester/elastane (Lycra) and polypropylene/elas­tane (Lycra) has better thermal properties than pure polypropylene multifilament knitted fabric. However, there is still a gap in current literature re­garding the thermo-physiological comfort properties of different fibre content in the knitted structure of terry and fleece. Moreover, there is no such research available in which the effect of thermo-physiological properties for washed terry and fleece fabric has been explained. The objective of this study was to analyse the effect of knitted fabric type (terry and fleece) on thermo-physiological comfort properties such as air permeability, water vapor resistance and thermal re­sistance. Also analysed was the effect of different fi­bre content (cotton and polyester) and areal densities on thermo-physiological comfort properties of fabric before and after washing. 2 Materials and methodology 2.1 Materials Used in this work were yarns differing in terms of the proportion of cotton (CO) and polyester (PES), which were provided by Masood Textile Mills Limited, Faisalabad, Pakistan. The details of these yarns are presented in Table 1. The chemicals and reagents used in the study were produced by Archroma, Pakistan. All the chemicals and reagents used were of analytical grade. Table 1: Fibre content and yarn count used for developing knitted fabrics Seq. no. Yarn count (tex) Fibre content 1 29.5 100% CO 2 29.5 80% CO/20% PES 3 29.5 60% CO/40% PES 2.2 Methodology 2.2.1 Fabric preparation In this work, a total of 36 samples of terry and fleece fabrics were developed according to the combina­tion of selected factor levels [fabric type: (terry and fleece), finishing: (before and after), fibre content: (100% CO, 80% CO/20% PES and 60% CO/40% PES) and fabric mass per unit area: (220, 240, 260)], and are presented in Tables 4 and 5 respec­tively. All samples were developed using a Mayer & Cie Relanit 4.0 circular knitting machine from Germany. Different machine settings, such as num­ber of needles, diameter and needle gauge, were op­timized to achieve the required areal densities (220, 240 & 260) of fabric samples (Table 2). Table 2: Machine settings for developing different mass per unit area of fabrics Seq. no. No. of needles Diameter of the cylinder (cm) Needle gauge 1 1680 76.2 18 2 1872 76.2 20 3 2074 76.2 22 It is evident from Table 2 that as the fabric mass per unit area was increased from 220 g/m2 to 260 g/m2, the number of needles was increased to obtain more yarns to cover the required area in order to achieve the required values. The developed terry fabrics were converted into fleece fabric by abrading the surface of the fabric on a Gessner Napper Unipro 2006 raising machine. The thickness, stitch length and stitch density of terry and fleece fabrics, as well as mass per unit area are presented in Table 3. 2.2.2 Fabric processing After fabric preparation, the samples were moved to the textile processing department of Masood Textile Mills Limited, Faisalabad, Pakistan for fur­ther processing: – semi-bleaching process This process was carried out to increase absorben­cy in the developed fabric samples. Knitted fabrics were semi-bleached at 110 °C for 55 minutes using Imacol C3G plus (1.5 g/L), Felosan RG-N detergent (0.6 g/L), RUCO-STAB OKP (0.33 g/L), Polipan conc. (0.50 g/L), NaOH flakes (2.50 g/L), and H2O2 50% (2.0 g/L). – neutralizing After the semi-bleaching process, neutralization was carried out to eliminate the presence of hydro­gen, which can cause shade variations in the sam­ples. All of the semi-bleached fabrics were neutral­ized at 55 °C for 42 minutes using CH3COOH (2.0 g/L) and BT-88 catalase (0.2 g/L). Table 3: Planned parameters and physical properties of knitted fabrics Fibre content Fabric type Mass per unit area (g/m2) Thickness (mm) Stitch length (cm) Stitch density (cm-2) 100% CO Terry 220 0.76 0.31 1364 100% CO Terry 240 0.85 0.325 900 100 % CO Terry 260 0.86 0.34 1080 80% CO 20% PES Terry 220 0.71 0.305 1364 80% CO 20% PES Terry 240 0.75 0.325 900 80% CO 20% PES Terry 260 0.80 0.35 1080 60% CO 40% PES Terry 220 0.72 0.305 1364 60% CO 40% PES Terry 240 0.77 0.325 900 60% CO 40% PES Terry 260 0.78 0.34 1080 100% CO Fleece 220 0.74 0.31 1452 100% CO Fleece 240 0.90 0.325 972 100% CO Fleece 260 1.01 0.34 1160 80% CO 20% PES Fleece 220 0.83 0.305 1452 80% CO 20% PES Fleece 240 0.93 0.325 972 80% CO 20% PES Fleece 260 0.97 0.35 1160 60% CO 40% PES Fleece 220 0.84 0.305 1452 60% CO 40% PES Fleece 240 0.87 0.325 972 60% CO 40% PES Fleece 260 0.95 0.34 1160 – dyeing Cotton/polyester (PES/CO) blended knitted fabrics were dyed using reactive dyes. First, the cotton fi­bres were dyed in a jet machine using reactive dyes. After the completion of the dyeing process, the un­fixed dye was removed in a soaping process. – finishing process After dyeing, the samples were dried and stabi­lized through the finishing process in Monforts Stenter 6 chambers (80 m/minute, 50–250 °C, steam 2 bar) for the purpose of achieving shape-retention, crease-resistance and resilience properties. – washing Later, 18 knitted terry and 18 fleece fabric samples were washed to give them special effects. The wash­ing was performed in a Tonello washing machine using pre-cleaning, nano-bubble technology and neutralization. The liquor ratio of water and Felosan RGN was maintained at 1:20 (g/L) for pre-cleaning. The fab­ric samples were soaked in the solution at 70 °C for 5 minutes. The neutralization of knitted samples was then performed in an acidic medium. Using nano-bubble technology, a mixture of sodi­um hypochlorite (NaOCl) (400ML/L) and water was used to discharge colours from the garment surface. Nano-bubble technology uses less water and chem­icals. Flow rate was maintained at 16 min/L with a pressure of 2.3 bar for five minutes, not only to re­move the colour but also to give a tone-down effect to fabrics This process was performed in a Tonello washing machine [21]. 2.3 Characterizations of knitted fabrics 2.3.1 Mass per unit area The mass per unit area of samples was determined according to the standard testing procedure set out in ISO 3801:1977. Fabric samples were cut using a circular cutter with an area of 100 cm2. After cut­ting the required fabric samples, they were weighed on a scale, and the mean values of the mass per unit area of the fabrics were calculated. 2.3.2 Fabric thickness The thickness of developed knitted fabrics was measured using a Kawabata Evaluation System. A 20 cm × 20 cm fabric sample was cut and positioned on a compression tester in accordance with ASTM D1777. A compression force of 50 g was applied to the samples at a compression rate of 0.0067 mm/s on a fabric area of 2 cm2. Three readings of each sample at different places were recorded. 2.3.3 Air permeability (AP) The air permeability of fabrics was determined us­ing an SDL-Atlas M021A fabric air permeability tester according to the ASTM-D737 test method. Fabric samples with an area of 20 cm2 were tested for air permeability at an air pressure of 100 Pa. Ten values ¸for each fabric (five from the face and five from the back) were recorded at different places to obtain average values. 2.3.4 Thermal resistance (Rct) The thermal resistance of fabric samples was measured using a PERMETEST measuring de­vice according to the ISO 11092:2014 test meth­od. Polytetrafluoroethylene (PTFE) membrane was used to cover the measuring head of the PERMETEST device and was kept dry to de­termine thermal resistance under steady-state conditions. 2.3.5 Water vapor permeability (WVP) The water vapor permeability index was measured according to the ISO BS 7209-1990 test method. It was calculated by expressing the water vapor per­meability of the fabric as a proportion of the water vapor permeability of a reference woven fabric. 2.4 Experiment design 2.4.1 Taguchi technique The Taguchi technique was used for the optimiza­tion of the air permeability, thermal resistance and water vapor permeability of fabrics. The different factors and their levels used in this study are pre­sented in Table 4. Table 4: Factors and levels used in this study Factors Level 1 Level 2 Level 3 A: Fabric type A1-terry A2-fleece B: Finishing B1-before B2-after C: Fibre content C1-100% CO C2-80% CO 20% PES C3-60% CO: 40% PES D: Fabric mass per unit area D1-220 D2-240 D3-260 In this study, three responses (AP, Rct, WVP) were two levels each and the other two with three levels taken for simultaneous optimization using Taguchi-each, were taken into consideration in our study. An based principal component analysis (PCA). The de-L36 (22 x 32) orthogonal array was constructed for tailed experiment design with the corresponding these factors using Minitab 19 software. To meet the mean values of responses can be seen in Table 5. property of orthogonality, every pair of columns, A Taguchi orthogonal design is a highly fraction-each of possible pairs of elements, appears the same al orthogonal design that was used to reduce the number of times. Each combination was repeated number of experiment runs. Four factors, two with three times as shown in Table 5. Table 5: Taguchi-based experiment design with mean experimental results Seq. no. Coded Actual Responses A B C D Fabric type Finishing Blend % CO/% PES Mass per unit area (g/m2) Y1: AP (mm/s) Y2: WVP (g/m2 day) Y3: Rct (m2K/W) 1 1 1 1 1 Terry Before 100/0 220 1660 86 0.0089 2 1 1 2 2 Terry Before 80/20 240 403 90 0.021 3 1 1 3 3 Terry Before 60/40 260 324 95 0.028 4 1 1 1 1 Terry Before 100/0 220 1660 86 0.0089 5 1 1 2 2 Terry Before 80/20 240 403 90 0.021 6 1 1 3 3 Terry Before 60/40 260 324 95 0.028 7 1 1 1 1 Terry Before 100/0 220 1660 86 0.0089 8 1 1 2 2 Terry Before 80/20 240 403 90 0.021 9 1 1 3 3 Terry Before 60/40 260 324 95 0.028 10 1 2 1 1 Terry After 100/0 220 673 86 0.01 11 1 2 2 2 Terry After 80/20 240 303 85 0.024 12 1 2 3 3 Terry After 60/40 260 303 94 0.0335 13 1 2 1 2 Terry After 100/0 240 661 85 0.012 14 1 2 2 3 Terry After 80/20 260 300 85 0.027 15 1 2 3 1 Terry After 60/40 220 323 94 0.028 16 1 2 1 2 Terry After 100/0 240 661 85 0.012 17 1 2 2 3 Terry After 80/20 260 300 85 0.027 18 1 2 3 1 Terry After 60/40 220 323 94 0.028 19 2 1 1 2 Fleece Before 100/0 240 533 84 0.022 20 2 1 2 3 Fleece Before 80/20 260 293 85 0.0317 21 2 1 3 1 Fleece Before 60/40 220 304 92 0.031 22 2 1 1 2 Fleece Before 100/0 240 533 84 0.022 23 2 1 2 3 Fleece Before 80/20 260 293 85 0.0317 24 2 1 3 1 Fleece Before 60/40 220 304 92 0.031 25 2 1 1 3 Fleece Before 100/0 260 344 83 0.026 26 2 1 2 1 Fleece Before 80/20 220 303 88 0.027 27 2 1 3 2 Fleece Before 60/40 240 290 91 0.0317 28 2 2 1 3 Fleece After 100/0 260 242 82 0.0303 29 2 2 2 1 Fleece After 80/20 220 240 84 0.0266 30 2 2 3 2 Fleece After 60/40 240 267 87 0.034 31 2 2 1 3 Fleece After 100/0 260 242 82 0.0303 32 2 2 2 1 Fleece After 80/20 220 240 84 0.0266 33 2 2 3 2 Fleece After 60/40 240 267 87 0.034 34 2 2 1 3 Fleece After 100/0 260 242 82 0.0303 35 2 2 2 1 Fleece After 80/20 220 240 84 0.0266 36 2 2 3 2 Fleece After 60/40 240 267 87 0.034 2.4.2 Principal component analysis and signal-to-noise ratio (PCA-S/N ratio) An approach combining principal component anal­ysis (weighed by their eigenvalues) and Taguchi sig­nal-to-noise ratio was used to systematize the goals of the novel responses and eliminate the correlation between the many responses. A six-step process for applying the combined PCA-S/N ratio is specified in reference material [22]. Step 1: Convert the original data from the Taguchi experiment into signal-to-noise ratio for respons­es using the appropriate equation, depending on characteristics that differ according to the nature of the problem under study and that may be catego­rized as larger-the-better, lower-the-better or nom-inal-the-best. The mathematical equations (1-3) for S/N ratios are presented below: Larger-the-better .... .... 1 (....................)=-10............ (#1) (1) ........ ............2 ....=1 where y represents the i duplicate of j response and n ijthth represents S, i.e. the number of repetitions. Lower-the-better .... .... 1 (....................)=-10............ () (2) ........#............2 ....=1 Nominal-the-best .... ....#2 (....................)=10............() (3) ........2 where y!+y"+y#+,………………,y$ y"= n #- y()! s! ."$%(y" = n-1 Taguchi’s signal-to-noise ratio was applied for air and water vapor permeability responses according to equation (1) and for thermal resistance according to equation (2). Step 2: Normalize the signal-to-noise ratios: yij -min(yij) Yij = (4) max (yij)-min(yij) Step 3: Perform factor analysis using MINITAB 18 statistical software according to the principal com­ponent method (PCA) to determine the number of factors to extract in a factor analytic study. Step 4: Compute MRPI (Multi-Response Per­formance Index) using the principal component achieved via factor analysis (equations 5–7). X!= P1Y!+P1Y" (5) X!= P2Y"+P2Y! (6) MRPI=W!X! + W#X# + W$X$ +. (7) where W1 and W2 represent the weights of particular prin­cipal components. P1 and P2 represent the principal components of factors 1 and 2 respectively. Step 5: Describe the optimum factor and the com­bination of its level. Improved product features are obtained via a higher performance index. The factor’s effect and optimum level of each controlled factor can be assessed on the basis of the performance index. The factor’s effect (FE) can be determined as (equation 8): FE=max(MRPI)-min(MRPI) (8) Step 6: Perform an analysis of variance (ANOVA) to determine significant factors. 3 Results and discussion 3.1 Air permeability The air permeability of terry and fleece fabrics with different fibre proportions and areal densities was investigated before and after the washing process. It is evident from Figure 1 that all the values of air permeability showed that all fabric samples allow the flow/passage of air through them. However, a significant difference in air permeability was identified between terry and fleece fabrics. It was determined that the fabric structure has a signifi­cant effect on the air flow rate through the fabric. The results also indicated that fleece fabrics offered higher resistance to air movement through the fab­ric than terry fabrics because the fleece fabrics have pile or plush on their surface, which offered more resistance to air while passing through the fabrics. Hady and Baky found that fleece fabrics showed higher air resistance due to the more random ar­rangement of raised fibres from the surface of fabric [23]. Similar results were also reported by Badr and tighter. In another study, S. Vasile et al. [26] showed that air permeability decreased with an increase in the number of washes. Increasing the mass per unit area of the fabrics also resulted in a decrease in the air permeability of fabrics, as shown in Figure 1. Published literature [27-28] shows that increasing the mass per unit area of a fabric resulted in a re­duction in the air permeability of fabrics because fabric thickness increases with an increase in mass per unit area. This also offers higher resistance to air flow because of a reduction in porosity between the yarns in the fabric. Machine needle gauge, stitch length and material content play an important role in achieving the required mass per unit area of a fabric [29-30]. It is evident from Table 3 that as the mass per unit area of terry fabric was increased from 220 g/m2 to 260 g/m2, the stitch length de­creased because of the higher number of needles per unit area, which resulted in an increase in the amount of yarn in a particular area. A decreased stitch length ultimately results in a more compact structure, which causes a reduction in air permea­bility [31]. As stitch length decreased, more yarns became closer to each other, thereby decreasing pore spacing, which facilitated a higher resistance to air flow (9). As the polyester content in the yarn was increased, a gradual reduction in air permea­bility of knitted fabrics was observed because of the increased packing density of fibres. Nazir et al. [32]developed a mathematical relationship between yarn packing density and yarn count, spindle speed, twist per inch, yarn diameter and yarn hairiness (yarn packing density = 0.21 - 0.000293; yarn count = 0.00000013; spindle speed = + 0.00633; twist per inch = +0.645; yarn diameter = 0.0316). Increasing the polyester content in the yarn resulted in higher yarn packing density, which resulted in a reduction in the number of pores, which in turn might cause reduced air permeability values. 900 779 800 Air permeability (mm/s) 660 700 611 Nahrawv who determined that the raising of fibres on the surface of fabric helped provide an effective barrier against the flow of air [24]. It is evident from Figure 1 that air permeability was decreased both in terry and fleece fabrics af­ ter washing. Similar results were also reported by Mavruz and Ogulata [25] who found that air per­ 575 600 500 400 303 339 300 302 301 200 100 0 A1A2 B1B2 C1C2C3 D1D2D3 meability was decreased in knitted fabrics after Levels of factors washing because the structure of fabric becomes Figure 1: Air permeability of terry and fleece with different proportions of fibre content and mass per unit area before and after the washing process 3.2 Thermal resistance The thermal resistance of terry and fleece fabrics with different proportion of fibre content and ar­eal densities was determined before and after the washing process. It was established that different parameters, such as fibre content, yarn character­istics, fabric construction and finishing treatments, have a significant impact on the thermal charac­teristics of fabrics. It is evident from Figure 2 that fleece fabrics showed higher thermal resistance than terry fabrics. After washing, however, ther­mal resistance increased from 0.0238 m2K/W to 0.0264 m2K/W. A higher value of thermal resistance was found in fleece fabrics than in terry fabric be­cause the fleece has a raised surface that resulted in the greater thickness of the fabric and trapped more air in its structure. As air is a good thermal insula­tor, the greater thickness of the fleece fabric resulted in higher thermal insulation than terry fabric [35]. Havenith [15] also reported similar results, as he showed that thermal resistivity increased as a fabric trapped more air in its structure. As the mass per unit area of fabric was increased from 220 g/m2 to 260 g/m2, the stitch length also decreased, which resulted in a higher number of stitches in a particular area. The fabric thickness thus increased with an increase in the mass per unit area of fabric [33-35]. Afzal et al. [16] and Mitra et al. [36] also reported similar results of thermal resistance in knitted fabrics. In this study, the thermal resistance of fabrics increased slightly after the washing process. This may be due to the fact that after washing, the fabric structure became more compact, which contributed to an increase in thermal resistance. However, Holcombe showed that washing did not have any impact on the ther­mal resistance of polyester/cellulosic fabrics [37]. Increasing the polyester content of the yarn, howev-of fabric; increasing the value of needle gauge de­creases the stitch length of fabric. As a result, the GSM of fabric increases and the water vapor perme­ability of the fabric decreases [39, 40]. A decreasing trend in moisture vapor permeability was observed with an increase in the mass per unit area of fabrics as shown in Figure 3. Reducing the gaps in the fab­ric structure caused an increase in material thick­ness, which offered more resistance in moisture transportation from one side of fabric to the other. er, increased the thermal resistance of fabrics. Water vapor permeability (g/m3) 0.033 Thermal resistance (m2K/W) 90 0.031 0.029 0.027 0.025 0.023 0.021 86 84 82 0.019 Levels of factors 0.170 Figure 3: Water vapor permeability of terry and fleece Levels of factors with different proportions of fibre content and mass Figure 2: Thermal resistance of terry and fleece with different proportions of fibre content and mass per unit area before and after the washing process 3.3 Water vapor permeability Water vapor permeability is a measure of how much vapor is transmitted through a material. It is evi­dent from Figure 3 that terry fabric showed higher water vapor permeability than fleece fabrics, while both fabrics structures showed a decreasing trend of vapor permeability after the washing process. Kandhavadivu et al. [38] reported that piled/fleece fabrics demonstrated a slower transfer of mois­ture than other knitted structures because of lower contact of fibre with moisture and increased thick­ness of material. It is evident from Figure 3 that after washing water vapor permeability decreased slightly, from 89 to 86 g/mm2. This slight decrease in water vapor permeability may be attributed to an increase in fabric hairiness after washing, which offered more resistance to the flow of water vapors through the fabric thickness. As mentioned earlier, the packing density of yarn increases with an increase in polyester content in the cotton/polyester blend, which resulted in a re­duction in the inter-fibre spacing. Water vapor per­meability is inversely proportional to the thickness per unit area before and after the washing process 3.4 Optimization using principal component analysis combined with the signal-to-noise ratio (PCA-S/N ratio) method The multi-response optimization of AP, WVP and Rct was performed using principal component anal­ysis (PCA). Initially, the S/N ratio values for the responses were determined as shown in Table 6. The S/N ratios were computed as larger-the-better for AP and WVP according to equation 1 and low­er-the-better for Rct according to equation 2. In the second step, normalized S/N ratios were calculated according to equation 4 for all the output variables to eliminate the probabilities of error and normal­ize several quality characteristics as presented in Table 5. In the third step, principal component anal­ysis was performed using the results of normalized S/N ratios. The first principal component has an ei­genvalue greater than one, and was considered for further analysis. The principal component analysis matrix is presented in Table 7. The data from Table 7 were used to calculate X1, X2 and MRPI according to equations 5-9, and the results are presented in Table 8. MRPI=0.656(X!)+ 0.323(X#)+ 0.020(X$) (9) Table 6: S/N ratios of experimental results Seq. No. S/N ratios Normalized S/N ratio MRPI Y1: AP (mm/s) Y2: WVP (g/m2 day) 0.7630 AP WVP Rct 1 64.402 38.700 0.3931 1.000 0.331 0.000 0.7630 2 52.094 39.076 0.4414 0.268 0.633 0.639 0.3931 3 50.186 39.532 0.7630 0.154 1.000 0.854 0.4414 4 64.402 38.700 0.3931 1.000 0.331 0.000 0.7630 5 52.094 39.076 0.4414 0.268 0.633 0.639 0.3931 6 50.186 39.532 0.7637 0.154 1.000 0.854 0.4414 7 64.402 38.700 0.3931 1.000 0.331 0.033 0.7637 8 52.094 39.076 0.4414 0.268 0.633 0.639 0.3931 9 50.186 39.532 0.4480 0.154 1.000 0.854 0.4414 10 56.554 38.660 0.1792 0.533 0.299 0.084 0.4480 11 49.603 38.619 0.4016 0.120 0.266 0.739 0.1792 12 49.603 39.456 0.4193 0.120 0.939 0.988 0.4016 13 56.402 38.561 38.396 0.524 0.220 0.222 0.4193 14 49.542 38.599 31.361 0.116 0.250 0.827 0.1735 15 50.180 39.504 31.046 0.154 0.977 0.854 0.4337 16 56.402 38.561 38.396 0.524 0.220 0.222 0.4193 17 49.542 38.599 31.361 0.116 0.250 0.827 0.1735 18 50.180 39.504 31.046 0.154 0.977 0.854 0.4337 19 54.533 38.508 33.134 0.413 0.177 0.675 0.3415 20 49.303 38.577 29.981 0.102 0.233 0.946 0.1609 21 49.589 39.233 30.170 0.119 0.760 0.930 0.3420 22 54.533 38.508 33.134 0.413 0.177 0.675 0.3415 23 49.303 38.577 29.981 0.102 0.233 0.946 0.1609 24 49.589 39.233 30.170 0.119 0.760 0.930 0.3420 25 50.696 38.392 31.688 0.185 0.084 0.799 0.1644 26 49.603 38.856 31.361 0.120 0.457 0.827 0.2426 27 49.247 39.192 29.981 0.099 0.727 0.946 0.3184 28 47.658 38.288 30.367 0.004 0.000 0.913 0.0209 29 47.589 38.517 31.487 0.000 0.185 0.817 0.0760 30 48.490 38.752 29.355 0.054 0.373 1.000 0.1757 31 47.658 38.288 30.367 0.004 0.000 0.913 0.0209 32 47.589 38.517 31.487 0.000 0.185 0.817 0.0760 33 48.490 38.752 29.355 0.054 0.373 1.000 0.1757 34 47.658 38.288 30.367 0.004 0.000 0.913 0.0209 35 47.589 38.517 31.487 0.000 0.185 0.817 0.0760 36 48.490 38.752 29.355 0.054 0.373 1.000 0.1757 Table 7: Principal component analysis matrix Seq. no. Principal component Eigenvalue Proportion Eigenvector 1 First 1.9689 0.656 -0.687 (y), 0.196 (y), 0.700 (y) 111213 2 Second 0.9702 0.323 0.196 (y), 0.976 (y), -0.096 (y) 212223 3 Third 0.0609 0.020 0.700 (y), -0.071 (y), 0.711 (y) 313233 Table 8: Main effects on MRPI Seq. no. Factors Level 1 Level 2 Level 3 Max – Min 1 Fabric type (A) 7.8749 3.2319 - 0.5988 2 Finishing (B) 7.2074 3.8994 - 0.3039 3 Blend (C) 4.4865 2.4977 4.1226 0.1868 4 GSM (D) 4.7596 3.7256 2.6216 0.1905 Table 9: Results of ANOVA The main effects on MRPI are presented in Table 8. The table shows that the controllable factors on MRPI value were, in the order of importance, A, B, D, C. The maximum MRPI value indicates better quality. The optimum parameters might therefore be set as A1, B1, C1 and D1. The results of ANOVA are presented in Table 9. It was determined that fabric type was the most im­perative factor, with a contribution of 38%, while finishing type was the second most important fac­tor, with a contribution of 18%. The blend ratio and mass per unit area showed almost the same contri­bution, while error was determined to be 20%. All the factors have a significant effect on the comfort properties of fabrics. However, factors A and B have a greater effect than C and D. The optimum response values might be set as A1, B1, C1 and D1, which cor­responds to terry fabric, before washing, 100% cotton and 220 g/m2 respectively. The results showed that this fabric had higher air and water vapor permeabil­ity values, but a lower thermal resistance value. 4 Conclusion This study proposed a method for the multi-response optimization of knitted fabric thermal comfort prop­erties for sportswear using Taguchi-based principal component analysis. Herein, terry and fleece knitted fabrics, with mass per unit area of 220 g/m2, 240 g/m2 and 260 g/m2, were developed using a 29.5 tex (20’s Ne) staple spun yarn with three blend ratios (100% cotton, 60% cotton/40 polyester and 80% cotton/20% polyester), while thermal comfort properties, includ­ing air permeability, water vapor permeability and thermal resistance, were analysed before and after fabric washing. It was observed that air permeability and water vapor permeability decreased and thermal resistance increased after washing. The multi-re­sponse optimization proposed optimum comfort properties for 100% cotton terry fabric with a mass per unit area of 220 g/m2 before washing. ANOVA results showed that fabric type was the most critical factor affecting fabric comfort properties (38%), while finishing type (18%) had a comparatively smaller contribution to those properties. The blend ratio and mass per unit area (12%) were found to have a mini­mum effect on fabric comfort properties. Seq. no. Factors SS df MS F-Test Contribution (%) 1 A 0.5988 1 0.5988 64.43 38 2 B 0.3040 1 0.3040 32.71 18 3 C 0.1869 2 0.0934 10.05 12 4 D 0.1905 2 0.0953 10.25 12 5 Error 0.2788 30 0.0093 1.00 20 6 Total 1.3685 36 References 1. OGLAKCIOGLU, Nida, MARMARALI, Arzu. Thermal comfort properties of some knitted structures. Fibres & Textiles in Eastern Europe, 2007, 15(5–6), 64–65. 2. DAS, Apurba, ALAGIRUSAMY, R. Science in Clothing Comfort. New Delhi : Woodhead Publishing, 2010, doi: 10.1016/B978-1-84569-789-1.50009-2. 3. CHOUDHURY, A.K. Roy, MAJUMDAR, P.K., DATTA, C. Factors affecting comfort: human physiology and the role of clothing. In Improving Comfort in Clothing. Edited by Guowen Song. Elsevier, 2011, 3–60, doi: 10.1533/9780857090645.1.3. 4. BHATTACHARYA, Someshwar S., AJMERI, Jitendra R. Air permeability of knitted fab­rics made from regenerated cellulosic fibres. 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Tekstilec, 2023, Vol. 66(1), 31–37 | DOI: 10.14502/tekstilec.66.2022085 Chandrasekaran P., Saminathan Ratnapandian Kumaraguru College of Technology, Department of Textile Technology, Coimbatore, 641049, India Evaluation of Sawdust as a Sustainable Dye Source in Ethiopia Ocena žagovine kot vira trajnostnega barvila v Etiopiji Short scientific article/Kratki znanstveni prispevek Received/Prispelo 10-2022 • Accepted/Sprejeto 1-2023 Corresponding author/Korespondencni avtor: Saminathan Ratnapandian, Associate Professor Phone: +91735824846 Email: saminathan.r.txt@kct.ac.in ORCID ID: 0000-0003-2905-2333 Abstract Increasing eco-consciousness among consumers is creating an expanding niche market for textiles coloured using natural dyes. Natural dyes are derived from different parts of plants, animals (insects and invertebrates) and minerals. Although plant sources are common, a growing global population makes them compete with food crops. Hence, there is a need to investigate alternate avenues for procuring natural dyes. This research examined the feasibility of utilizing extractions of sawdust, a waste product of the wood furniture industry, as a natural colorant. Sawdust is an inevitable waste generated during the conversion of wood into consumer products such as furniture (tables, chairs, etc.), doors and windows. Sawdust, generated in significant amounts by timber mills, may be used in chipboard manufacture. However, the furniture industry disposes of sawdust as fuel or sometimes as communal waste. In this study, segregated sawdust of the most common woods was collected from Ethiopian furniture houses in Addis Ababa and Bahir Dar. Dyeing was attempted on cotton and wool fabrics using individual aqueous extractions. Different shades were obtained only on wool by simultaneous mordanting with mordants, such as copper sulphate, ferrous sulphate and potassium dichromate, using the exhaust dyeing method. Acceptable fastness to light, perspiration, rubbing and washing, as evaluated according to the relevant ISO standards, was obtained. It may be concluded that sawdust is a viable secondary source of natural dyes for textile coloration in Ethiopia and elsewhere. Keywords: natural dyes, sawdust, mordanting, wool, cotton Izvlecek Vse globlja ekološka ozavešcenost med potrošniki ustvarja cedalje vecjo tržno nišo za tekstilije, obarvane z naravnimi barvili. Naravna barvila se pridobivajo iz razlicnih delov rastlin, živali (žuželk in nevretencarjev) in mineralov. Rastlinski viri, ki se najpogosteje uporabljajo za te namene, so zaradi narašcajoce svetovne populacije namenjeni predvsem pridobivanju hrane. Zato je treba raziskati alternativne vire pridobivanja naravnih barvil. V tej raziskavi je bila kot vir naravnega barvila proucena možnost uporabe ekstrakta iz žagovine, ki je odpadek pohištvene industrije. Žagovina je neizogiben odpadek, ki nastane pri predelavi lesa v izdelke za široko porabo, kot so pohištvo (mize, stoli itd.), vrata in okna. Žagovina, ki v znatnih kolicinah nastaja v obratih za žaganje hlodov, se lahko uporablja pri proizvodnji ivernih plošc. Vendar pa pohištvena industrija odlaga žagovino tudi kot gorivo ali vcasih kot komunalne odpadke. Za potrebe te študije je bila loceno zbrana žagovina najbolj razširjenih gozdov iz etiopskih pohištvenih obratov v Adis Abebi in Bahir Darju. S posameznimi vodnimi ekstrakti so bile barvane bombažne in volnene tkanine. Razlicni barvni odtenki so bili po metodi izcrpavanja doseženi le na volneni tkanini s socasnim cimžanjem s sredstvi, kot so bakrov sulfat, železov sulfat Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. in kalijev dikromat. Dosežene so bile sprejemljive obstojnosti na svetlobo, znoj, drgnjenje in pranje, ki so bile ocenjene v skladu s standardi ISO. Na podlagi izvedene raziskave je mogoce sklepati, da je žagovina uspešen sekundarni vir naravnih barvil za barvanje tekstila v Etiopiji in drugod. Kljucne besede: naravna barvila, žagovina, cimžanje, volna, bombaž 1 Introduction Before the invention of synthetic dyes, humans used natural colorants from plants, animals, soil, in­sects and mineral resources. Those colorants were employed for the coloration of human and animal skins, hair, teeth, bones, all types of vegetable fibres (clothing) and woods in a wide range of colours [1, 2]. Since 1856, synthetic dyes have dominated tex­tile coloration because of their low cost, ease of syn­thesis and application, and excellent fastness prop­erties [3, 4]. Presently the use of synthetic dyes is estimated at around 10,000,000 tons per annum [5]. However, these synthetic dyes, derived from pe­troleum, not only destroy the environment during their synthesis, but also discharge effluents into wa­ter bodies and affect aquatic life [6-9]. Hence, there is growing interest in bringing natural dyes back to the textile sector [1, 10]. In this context, a varie­ty of application methods and dye sources, such as beetroot, henna leaves, eucalyptus bark, tea leaves, turmeric rhizomes, Rubia tinctorum roots, Bixa orellana seeds, kola nut and walnut bark, have been investigated [2, 11-18]. Table 1 lists some common plants used as dye sources and colours obtained. The consequence of an exploding global popula­tion is increased demand for food and living space. This results in intense competition between land re­quired for food (agriculture), for shelter (housing) and for textiles (growing cotton and dye plants) [19]. Hence, any alternative natural dye source is highly attractive [20]. Several authors have proposed the use of by-products and waste products as potential dye sources. The various industries that have been considered include timber, food processing, bev­erage manufacturing, oil extraction and wine pro­duction. Such sources have the additional benefits of providing value addition and employment, and alleviating environmental pollution [10, 21-34]. Ethiopia has a rich history of textile production and coloration. The country is home to a plethora of plants that can potentially provide a rainbow of colours [35]. However, the problem of competition for land mentioned earlier is present here, as well. Getaneh [36] and Shuka [37] have reported on the variety and volume of the furniture industry in Ethiopia. Although the sector is quite disorganized, it produces a wide variety and sizable volume, ca­tering primarily to the domestic market and occa­sionally to international customers. This research investigated sawdust from the Ethiopian furniture industry as an alternate source of natural dyes. The objectives were to assess the availability of sawdust (in terms of variety and volume), extract colorant from the most common varieties, apply them to textiles and determine the desirable properties of the dyed materials. The purpose of the study was to explore the possibilities of providing a value added product and employment, and creating a niche market. Table 1: Example of plant dye source and colours obtained Plant Scientific name Part used CI Name/chemical group Colour obtained Burberry Berberis vulgaris branches and roots C.I. Natural Yellow 18 yellow–brown Canadian golden rod Solidago canadiensis buds, leaves flavonoid dye yellow–olive Madder Rubia tinctorum roots C.I. Natural Red 8 red–brown Hollyhock Alcea rosea buds anthocyan dye brown–green Privet Ligustrum vulgare berries C.I. Natural Black 5 blue–green Walnut tree Juglans regia green walnut, brown nut shell C.I. Natural Brown 7 brown Ash tree Fraxinus excelsior bark flavonoid dye beige–black Sticky alder tree Betula alnus bark gallotannin dye beige–black 2 Materials and methods Ready-for-dyeing plain weave cotton fabric from Bahir Dar Textile Share Company, Ethiopia and twill weave wool fabric from Bhuttico Industries, Himachal Pradesh, India was used as received. Ferric sulphate, copper sulphate, potassium dichro-mate, sodium carbonate, sodium chloride, sodium hydroxide, hydrochloric acid and acetic acid were of laboratory reagent (LR) grade. Non-ionic standard soap from SDC was used in all trials. Segregated sawdust, from the most common woods used, was sourced from different furniture manu­facturers in Addis Ababa and Bahir Dar. Colorant extraction Aqueous extraction was carried out individually for sawdust from each variety of wood. An initial mate­rial to liquor ratio (MLR) (sawdust to water) of 1:20 was employed throughout. The mixture of sawdust and water was stirred thoroughly and the tempera­ture increased to the boiling point. Extraction was continued for about 30 minutes, during which time the MLR was reduced to 1:15. After allowing the mixture to cool, the supernatant-coloured liquid was decanted, filtered, diluted to three times its vol­ume and used for dyeing. The procedure was based on the work done by Trinidad [24] and Ismal [26]. Mordanting Natural dyes generally have low affinity for textile materials and therefore require the use of mordants (metallic salts) for effective dyeing. Three methods, i.e.pre-mordanting (first treating with mordant and then dyeing), simultaneous mordanting (mordant and dye in the same bath) and post-mordanting (dyeing followed by mordanting), are widely prac­ticed [1, 20]. In this work, simultaneous mordant­ing was the only method investigated. Individual mordanting processes, using ferric sulphate (5 g/L), copper sulphate (10 g/L) and potassium dichromate (2 g/L), were compared. Cotton dyeing Dyeing was carried out at a MLR of 1:30 using the diluted extract solution obtained in the previous step. Sodium hydroxide at 5 g/L and sodium car­bonate at 2 g/L were used to obtain a pH of 9.5 in the dye bath. Dyeing was conducted for 30 minutes at 100 °C. Sodium chloride at 5 g/L and the appro­priate mordant were added after 15 minutes to assist in exhaustion and fixation. This was followed by a warm rinse and two cold rinses in water to remove unfixed dye. Samples were air dried and condi­tioned prior to fastness assessment. Wool dyeing A MLR of 1:30, similar to cotton dyeing, was also used here. Solutions of 10% hydrochloric acid and 10% acetic acid were used in the dye bath. Half the acid was added at the beginning and the remain­ing added after 15 minutes, together with the mor­dant. Dyeing was carried out at 80 °C for a period of 30 minutes. After dyeing, the samples were subject­ed to a warm rinse and two cold rinses in water, and then air dried and conditioned. Fastness assessment Colour retention during use is an important re­quirement for textile materials. This involves as­sessing changes in colour due to exposure to light and when subjected to rubbing, both in dry and wet conditions. Moreover, there should be minimal alteration in colour during washing and no stain­ing of other clothing being washed together. These properties were assessed according to the standard test methods listed in Table 2 and using the appro­priate equipment. Table 2: Test standards for fastness properties Fastness to Test method Washing ISO 105-C06:2010 Perspiration ISO 105-E04:2013 Rubbing ISO 105-X12:2016 Light ISO 105-B02:2014 3 Results and discussion Sawdust A survey of furniture manufacturers in Addis Ababa and Bahir Dar determined that Eucalyptus camaldulensis (Eucalyptus Amharic Bahirzaf), Cordial Africana (Sudan teak Amharic Wonza) and MDF (medium density fibre wood) were the three most commonly used woods. Wonza was relative­ly expensive and thus lower quantities were used. The source was both indigenous and imported. Saw mills in Jimma, in the Oromia region, report­edly produce the highest furniture grade timber in Ethiopia. The quantity of sawdust produced varied with the type of wood used and the design pro- a) duced. No records were maintained in this regard, as sawdust is a waste product. Generated sawdust is not segregated and usually burnt as fuel by the workers. Separated samples of each wood type in b) the form of powder or shavings or small chips were collected. All samples were powdered in the lab pri­or to extraction. Extraction c) Each wood type yielded a different coloured solu­tion after extraction. As can be seen in Figure 1, eu­calyptus (a) produced pale yellow, MDF (b) medium brown and wonza (c) dark brown colours. Figure 2: Wool dyed using eucalyptus sawdust with different mordants: a) ferric sulphate, b) potassium dichromate and c) copper sulphate a) b) a)b) c) Figure 1: Coloured solution from sawdust after c) extraction: a) eucalyptus, b) MDF and c) wonza Dyeing Cotton fabric was not coloured or was minimal­ly stained, irrespective of the source and mordant combination used. The stain, if any, was lost during a) the rinsing process after dyeing. Hence, cotton was not dyed using sawdust extracts in this trial. This agrees with the theory that vegetable fibres (cellu­losic) possess a low affinity for most natural dyes [1, b) 20]. These samples were therefore not subjected to further evaluation. In comparison, wool fabric, being a keratinous an­imal fibre, was easily dyed using sawdust extracts. The hue obtained differed based on the mordant, c) with ferric sulphate (a) producing a reddish beige shade, potassium dichromate (b) a khaki shade and copper sulphate (c) a greenish shade. This is shown in Figures 2 to 4. Changes in the sawdust source affected the depth of shade in most cases. This re­iterated the fact that mordant plays a critical role in deciding on the final shade of textile materials [38, 39]. Figure 3: Wool dyed using MDF sawdust with different mordants: a) ferric sulphate, b) potassium dichromate and c) copper sulphate Figure 4: Wool dyed using wonza sawdust with different mordants: a) ferric sulphate, b) potassium dichromate and c) copper sulphate Fastness Table 3 contains the ratings of the dyed and or ad­jacent materials after being subjected to exposure to Table 3: Fastness testing results Sawdust source Mordant Fastness test ratings Rubbing Wash Light Perspiration dry wet Wonza Copper sulphate 5 4/5 GRADE 1 staining on wool 4-5 No staining or colour change Ferric sulphate 5 4/5 GRADE 1-2 staining on wool 5 No staining or colour change Potassium dichromate 5 5 GRADE 2 staining on wool 5 No staining or colour change Eucalyptus Copper sulphate 5 5 GRADE 2 Staining on wool 4-5 No staining or colour change Ferric sulphate 5 5 GRADE 1 staining on wool 5 No staining or colour change Potassium dichromate 5 5 GRADE1 staining on wool 5 No staining or colour change MDF Copper sulphate 5 5 GRADE 1 Staining on wool 4-5 No staining or colour change Ferric sulphate 4/5 5 GRADE 1 Staining on wool 5 No staining or colour change Potassium dichromate 5 4/4 GRADE 1-2 staining on wool 5 No staining or colour change light, washing and rubbing. The results confirm that wool fabric dyed using sawdust extracts from euca­lyptus, MDF and wonza possess acceptable fastness traits. 4 Conclusion This research has identified a potential source of natural dye in the form of the sawdust produced in the Ethiopian furniture industry. A limited variety of shades can be produced by changing the mordant used. Although only wool was dyed, further work can be carried out to ensure cotton dyeing. A de­tailed cost analysis and the possibilities of commer­cialization, at least at the cottage-level, also need to be investigated. When commercializing, the envi­ronmental impact of metal salts (from unutilized mordants) in the effluent should also be considered. Acknowledgements The authors would like to thank the HOD, Principal and management of Kumaraguru College of Technology, Coimbatore for providing the facilities and administrative support to carry out this study. References 1. CARDON, D. 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Present status of natural dyes. Indian Journal of Fibre & Textile Research, 2001, 26, 191-201. 39. GULRAJANI, M.L., SRIVASTAVA, R.C., GOEL, M. Colour gamut of natural dyes on cotton yarns. Coloration Technology, 2001, 117(4), 225-228, doi: 10.1111/j.1478-4408.2001.tb00066.x. Tekstilec, 2023, Vol. 66(1), 38–46 | DOI: 10.14502/tekstilec.66.2022072 Scolastica Manyim,1, 2 Ambrose K. Kiprop,1, 2 Josphat Igadwa Mwasiagi,2, 3 Achisa Cleophas Mecha2, 4 1 Moi University, Department of Chemistry and Biochemistry, P.O. Box 3900-30100 Eldoret, Kenya 2 Moi University, Africa Center of Excellence in Phytochemicals, Textile and Renewable Energy, P.O. Box 3900-30100 Eldoret, Kenya 3 Moi University, Department of Manufacturing, Industrial and Textile Engineering, P.O. Box 3900-30100 Eldoret, Kenya 4 Moi University Department of Chemical and Process Engineering, P.O. Box 3900-30100 Eldoret, Kenya Cleaner Production of Bioactive and Coloured Cotton Fabric Using Euclea Divinorum Dye Extract with Bio-Mordants Cistejša izdelava bioaktivnih in obarvanih bombažnih tkanin z uporabo izvlecka barvila Euclea Divinorum s pomocjo organske cimže Original scientific article/Izvirni znanstveni clanek Received/Prispelo 9-2022 • Accepted/Sprejeto 2-2023 Corresponding author/Korespondencni avtor: Dr. Scolastica Manyim E-mail: smanyim@gmail.com ORCID ID: 0000-0001-9639-9877 Abstract Coloured textile products are more marketable, and are therefore always in higher demand. This has increased the use of synthetic dyes in the textile industry, thus raising environmental pollution associated with synthetic dyes. Natural dyes have been shown to be suitable alternatives. However, the use of metallic mordants during dyeing means the process is not eco-friendly, hence the need to develop bio-mordants that can be used as alternatives to some toxic metallic mordants. In this study, the effects of bio-mordants on the dyeing properties of Euclea divinorum Hiern (Ebenaceae) dye extract were assessed using different mordanting methods on cotton fabric. Dyeing characteristics were evaluated in terms of colour fastness and colour strength. Antioxidant textile finishing properties of the natural dye on cotton fabric was determined using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method. The bio-mordants improved the colour strength for dyed cotton fabric from 0.612 to 0.863 and 0.911 for the cotton fabric mordanted with mango and rosemary, respectively. This study identified an important basis of suitable bio-mordants that can be applicable when dyeing cotton fabric with E. divinorum natural dye. In addition, the good antioxidant activity of 72.5% indicates that E. divinorum dye extract is a prom­ising agent for the future development of bioactive, protective and health textile fabric. Keywords: natural dye, bio-mordants, antioxidant activity Izvlecek Obarvani tekstilni izdelki se dobro tržijo in po njih je vedno veliko povpraševanja. Zato so se sinteticna barvila v preteklosti veliko uporabljala, to pa je vodilo tudi v povecano onesnaževanje okolja. Naravna barvila so primerna alternativa, vendar je raba kovinskih cimž pri barvanju z naravnimi barvili okolju neprijazna. Iz tega izhaja potreba po razvoju organskih cimž, ki bi lahko zamenjale strupene kovinske. V tej raziskavi so bili ocenjeni ucinki organskih cimž na lastnosti obarvane bombažne tkanine z barvilnim ekstraktom iz Euclea divinorum Hiern (Ebenaceae) pri uporabi razlicnih metod cimžanja. Lastnosti obarvanja so bile ocenjene glede na barvno obstojnost in globino obarvanja. Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. Antioksidativne lastnosti bombažne tkanine, obarvane z naravnim barvilom, so bile dolocene z metodo 2,2-difenil-1-pikrilhidrazil radikala (DPPH). Organske cimže so izboljšale globino obarvanja obarvane bombažne tkanine z 0,612 na 0,863 oziroma 0,911 za tkanini, cimžani z mangom oziroma rožmarinom. Ta raziskava je pomembna osnova pri izbiri primernih organskih cimž za barvanje bombažnih tkanin z naravnim barvilom E. divinorum. Poleg tega dobra antioksidativna aktivnost 72,5 % kaže tudi na to, da je ekstrakt barvila E. divinorum obetavno sredstvo za nadaljnji razvoj tekstilij z bioaktivnimi, zašcitnimi in zdravilnimi lastnostmi. Kljucne besede: naravno barvilo, organska cimža, antioksidativno delovanje 1 Introduction The textile dyeing process is among the leading pol­luting industrial processes due to use of the toxic synthetic dyes [1]. An environmentally friendly tex­tile dyeing process can be achieved by substituting certain toxic synthetic dyes with natural dyes that have been shown to provide value added to tex­tiles [2-4]. The process of manufacturing synthetic dyes, together with the associated textile applica­tion procedures, discharge toxic wastewaters that require costly resources for complete treatment, and thus find their way into the environment [5–7]. Environmental awareness has led to a recent shift to natural dyes, which in turn has stimulated in­creased research on natural dyes [8, 9]. Most natural dyes exhibit poor to moderate colour fastness on fabric, which has been a major limitation in their use in the textile industries. As a result, nat­ural dyes are used together with mordants that help fix them on textile material. Commonly used mor­dants include metallic salts that fix dye molecules to the fabric through a combination that involves the dye molecules, the fabric molecules and the metallic ions that form insoluble precipitates [10]. Examples of metallic mordants are potassium aluminium sul­phate, stannous chloride, potassium dichromate, copper sulphate, ferrous sulphate, and others [11]. The main purpose of metallic mordants during natural dyeing is to enhance the affinity of the fab­ric to the dye molecules since the metal ions form coordination complexes that allow the attachment of the dye to the textile fabric [12]. In addition, the use of metallic mordants during natural textile dye­ing offers a wider spectrum of shades from a single natural dye extract [13]. The mordanting step in the natural dyeing process is very crucial, especially when dyeing cotton fabric because it lacks function­al groups, such as carboxylic and amino acid groups present in other textile fabrics that act as positions where the dye molecules attach [10, 14]. On the other hand, most of these metallic mordants have been found to be harmful and a small amount of the metallic ion takes part in the fixation of the dye to the fibre, hence a huge percentage of it finds its way into the environment [15]. Global restrictions on production industries regarding the use of toxic substance with the aim of curbing increasing envi­ronmental pollution have stimulated research on the development of environment-friendly mordants that can be used as alternatives to poisonous metal­lic mordants [16]. Bio-based mordants are gaining popularity since they are obtained from nature and thus facilitate a suitable approach for making the natural dyeing process a part of green chemistry. Bio-mordants are basically natural substance that are rich in tan­nins or metal ions, and are mainly obtained from plants. Examples include tartaric acid, tannic acid [17], tamarind seed coat tannins [18], mango bark [19] extracts from myrabolan, pomegranate rinds, banana leave ash, rosemary plant, rhizomes of tur­meric, bark of acacia, guava, etc. [7, 20, 21]. In order to lessen the environmental hazards caused by some metallic mordants, there is need to shift to bio-mor­dants, which will help in realizing the aim of produc­ing ecologically coloured textile materials [22–24]. In addition to colours obtained from different natural dye extracts, functional textile finishing properties have also been achieved. These include antimicrobial [25–29], antioxidant [30, 31], deodor­izing [32] and UV-protective properties [33–35]. The discovery of these additional functional properties of textiles brought about by natural dyes is impor­tant in the development of healthy and clean textile materials. Antioxidant activity is one of the most significant properties of bioactive textile since it protects textile material from damage and safeguards the human skin from inflammation and aging due to oxidative stress caused by free radicals [36]. The human skin is continuously exposed to ionizing radicals, which are the primary cause of skin damage and the as­sociated diseases [37]. Ultra-violet radiation is the main source of free radicals in the environment, and accumulate to such a level that the antioxidants in the skin cannot neutralize them, leading to oxi­dative stress, which may cause skin cancer and oth­er diseases [38]. Antioxidants, also referred to as free radical scav­engers, are substances that react with free radi­cals and neutralize them, thus counteracting their harmful effects. Studies have shown that antioxi­dant molecules such as phenols and flavonoids have good anti-cancer activity against skin cancer [39]. The antioxidant activity of textile fabric is achieved through the deactivation of very reactive and de­structive radicals in the environment, such as ox­ygen and nitrogen radicals [40]. It has been shown that natural dyes are suitable agents for achieving antioxidants properties in textile material be­cause they are not toxic and do not irritate the skin [41–43]. Clothes are in direct contact with the skin. For this reason, the antioxidant activity of textile materials is important in the development of bioac­tive, healthy textile fabrics. The antioxidant activity of Euclea divinorum aque­ous root extract has been studied and was found to be between 74.5–82.5% DPPH (2,2-diphenyl-1-pic rylhydrazyl) [44]. The objective of this study was to determine the effects of bio-mordants on the dyeing properties of E. divinorum natural dye extract, and to explore its potential as an antioxidant finishing agent for cotton fabric. The durability of the anti­oxidant properties of textile materials after washing was also determined. 2 Material and methods 2.1 Materials E. divinorum root bark was collected in Nandi County in Kenya (latitude 0° 01’ 59.5” S and longi­tude 35° 3’ 17.3” E). Commercially bleached, plain woven cotton fabric with 20 ends/cm, 13 picks/ cm, 29.4 tex (Nm 34) warp count, 29.4 tex (Nm 34) weft count and a mass per unit area of 97.1 g/m2 was purchased from a textile factory in Eldoret, Kenya, while 2,2 -diphenyl-1-picrylhydrazyl radical (DPPH) was used for antioxidant evaluation. 2.2 Extraction E.divinorum root bark was washed and dried using sunlight, and then ground into powder form using an electric grinder. The natural dye as then extract­ed using distilled water. The extraction conditions used were: temperature of 84 °C, time of 146 min­utes and M:L 7.5:100, as previously determined [45]. Conical flasks were used as extraction containers and a water bath was used to regulate the temper­ature. After extraction, the extracts were allowed to cool and filtered using filter paper. 2.3 Bio-mordanting The mango (Mangifera indica) bark bio-mordant was extracted using the procedure described by [24], where extraction was performed at 90 °C for one hour using 75g/L of the sample in distilled water. Rosemary (Rosmarinus officinalis) was pur­chased from a local market, cut into small pieces, dried under the sun and then ground into powder. A mixture of 20g/L of rosemary powder in distilled water was used to extract the mordant at 100 °C for one hour [46]. Bio-mordanting was carried out us­ing the pre-, meta- and post-mordanting methods. For the pre-mordanting method, the wet cotton fabric was immersed in the solution of the mordant using a material to-liquor ratio of 1:50 at 60 °C. Continuous stirring was maintained for one hour, followed by dyeing. In meta-mordanting, the wet cotton fabric was immersed in a flask containing the solution of the mordant and the dye extract us­ing a material to-liquor ratio of 1:50 at 60 °C for one hour. For the post-mordanting method, the previ­ously dyed cotton fabric was placed in flask con­taining the solution of the mordant using a material to-liquor ratio of 1:50 at 60 °C for one hour [24]. 2.4 Dyeing The cotton fabric was cut into equal sizes of 1g. Wetting of the fabric was performed using 5g/L of non-ionic detergent for 30 minutes prior to dyeing. E. divinorum aqueous dye extract was used to pre­pare the dyebath using a material-to-liquor ratio of 1:40[1]. After dyeing, the dye bath was allowed to cool. The dyed samples were then washed with cold water to remove the unfixed dyestuff and subjected to soaping with a 2 g/L soap solution, followed by rinsing with water and air drying. 2.5 Colorimetric measurements The colour characteristics of the dyed samples were measured with a Spectro -Flash X-rite SP62 spec­trophotometer, using a D65 source of light and 10° standard observer. The CIELAB coordinates were measured. The un-dyed cotton fabric was used as the blank. The relative colour strength (K/S) values were determined using the Kubelka–Munk equa­tion (equation 1). (1 -0.01....)! ....#....= (1) 2 ×0.01.... where K represents the absorption coefficient, S rep­resents the scattering coefficient and R represents the minimum reflectance of dyed substrate samples. 2.6 Colour fastness The ability of cotton fabric to retain dye during washing and rubbing, and when exposed to light and perspiration was determined using the rel­evant standard colour fastness tests. These were conducted according to ISO 105-C02:1989, ISO 105 A02:1993, ISO 105-X12:2000 and ISO AATCC-2009 for washing, exposure to light, rubbing and perspi­ration fastness, respectively, with some changes, where the grey scale used to rate the colour fastness was between one and five, with five representing the best fastness [25]. 2.7 Antioxidant activity The antioxidant activity of the pure and dyed cot­ton fabric was evaluated using a DPPH radical scavenging assay [41]. A total of 2.54 cm2 of the pure and dyed cotton fabric were separately im­mersed in a test tube containing 50mL solution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) in methanol (0.15 mM) and mixed thoroughly. The samples were incubated in the dark at room temper­ature for 30 minutes. The absorbance of the solution was measured at 517 nm using a UV-Vis spectro­photometer. The percentage antioxidant activity was calculated according to equation 2. ....!"#$%"& -....'()*&+ ....= ×100(%) (2) ....!"#$%"& where A represents antioxidant activity, Acontrol rep­resents the initial absorbance of the DPPH solution and Asample represents the absorbance of the re­maining DPPH solution after incubation with the sample. The durability of the antioxidant activity of the dyed samples was assessed by subjecting the dyed fabric to washing cycles, with the antioxidant ac­tivity determined after every washing. The washing tests were performed by putting the samples into a washing solution comprised of commercial deter­gent (2 g/L) with a material-to-liquor ratio of 1 : 50. The antioxidant activity was determined after the 1st, 5th and 10th washing cycles [41]. 3 Results and discussion 3.1 Colorimetric analysis The colour characteristics of the dyed samples were measured and are presented in Table 1. In terms of lightness (L*), the mango and rosemary bio-mor­dants increased lightness from 63 to 66.33 and 67.27, respectively, providing lighter shades of brown. Similarly, the intensity of the colour increased as in­dicated by an increase in the value of C*. The ability of mango and rosemary bio-mordants to form light­er shades indicates that they can be used as substi­tutes for metallic mordants that are used to brighten the colour of the dye on the fabric, such as alum and tin, an observation that has been reported previ­ously in literature [46]. The polyphenols in the rose­mary bio-mordants are responsible for the increased dye absorption by the cotton fabric, which leads to increased colour strength [20]. Pre-mordanting method for both mordants showed the best colour strength, as has been observed in other studies [19]. 3.2 Colour fastness Colour change in terms of washing and perspira­tion fastness was in the range of 4–5, except for the pre-mordanted fabric using mango and rosemary bio-mordants, which was 5 (Table 2). The pre-mor­danting method allows the poly-phenols to attach to the cellulosic fibre then act as bridge between the fibre and the dye molecules, thus improving the ability of the dye to fix to the fabric, which in turn enhances the fastness properties of the dye [20]. The excellent light fastness throughout the dyeing pro­cess indicates that the dye-fabric complex formed is resistant to fading during the exposure to ultravi­olet radiation [1]. Generally, the colour fastness of the cotton fabric dyed with E. divinorum dye extract was very good and is suitable for application in the textile dyeing industry. 3.3 Antioxidant activity Antioxidant activity as a percentage is measured by the reduction of the absorbance of DPPH. When the phenolic hydroxyl donates a proton to the DPPH rad­ical, the solution is decolorized and its absorbance is reduced [49]. The antioxidant activity of the assayed Table 1: Colorimetric values and colour strength of the dyed and mordanted cotton fabric Method Mordant L* a* b* C* H° K/S Shade - - 63.47 +4.63 +16.86 17.53 74.53 0.612 Pre Mango bark 67.27 +9.66 +21.01 23.13 65.32 0.863 Rosemary 66.33 +8.65 +18.80 20.72 65.19 0.911 Meta Mango bark 64.59 +11.82 +19.55 22.85 58.84 0.708 Rosemary 64.74 +10.65 +17.27 20.31 58.30 0.720 Post Mango bark 66.14 +9.97 +19.18 21.64 62.51 0.691 Rosemary 65.76 +7.26 +16.72 18.22 66.58 0.724 Table 2: Colour fastness of the dyed fabric using different methods of mordanting Method Mordant Washing fastness Rubbing fastness Perspiration fastness Light fastness C.C a) C.S b) Dry Wet C.C C.S Without 4–5 5 5 5 4–5 4–5 5 Pre Mango bark 5 5 5 5 5 5 5 Rosemary 5 5 5 5 5 5 5 Meta Mango bark 4–5 5 5 5 4–5 5 5 Rosemary 4–5 5 5 5 4–5 5 5 Post Mango bark 4–5 5 5 5 5 5 5 Rosemary 4–5 5 5 5 5 5 5 a) colour change, b) colour staining cotton fabric samples is shown in Table 3. Dyeing with the E. divinorum dye extract increased the an­tioxidant activity from 26.9% (undyed cotton) to 72.5% (dyed cotton), which can be attributed to the molecules adsorbed by the cotton fabric from the dye extract, which consequently imparts the radical scavenging activity into the fabric. The antioxidant activity of aqueous root extracts of E. divinorum activity [50]. The mango bark extract comprises polyphenols that are responsible for the radical scav­enging ability of the extract [48], [51]. The durability of the antioxidant activity after wash­ing cycles was as indicated in Figure 1. A subsequent 90 80 was found to be between 74.5–82.5% DPPH [46]. It was also noted that the antioxidant activity of the fabric samples bio-mordanted with mango (82.4%) and rosemary (85.3%) was higher than that of the un-mordanted (72.5%) fabric, which could be due to the additional activity from the bio-mordant ex­ tracts that have been shown to have good antioxidant Table 3: Antioxidant activity of the sample fabric Antioxidant activity (%) 70 60 50 40 30 20 10 Sample Antioxidant activity (%) Undyed cotton 26.9 Dyed 72.5 Mango mordanted 82.4 Rosemary mordanted 85.3 0 Washing cycles Dye Dye + Mango Dye + Rosemary Figure 1: Antioxidant activity of dyed and mordanted cotton fabric after washing cycles reduction in the antioxidant activity of the dyed samples was observed, and was found to be sim­ilar to what has been reported in other studies. However, the reduction in antioxidant activity be­came minimal after the 5th washing cycle, which is a significant attribute for this extract and can be as­cribed to its good fastness properties [36]. The rate of reduction was lower in the mango and rosemary mordanted fabric than in the unmordanted fabric due to the enhanced fastness of the dye to the fabric [41]. The rosemary mordanted fabric showed good antioxidant durability (above 80%) after the 10th washing cycle), indicating that the elements respon­sible for bioactivity were not affected by the washing process and thus remained very active [36]. 4 Conclusion The bio-mordants improved the colour strength from 0.612 to 0.863 for the dyed cotton and to 0.911 for the cotton fabric mordanted with mango and rosemary, respectively. In addition, the bio-mor­dants modified the colorimetric values, resulting in different shades of brown colour on the cotton fab­ric. All the fastness properties in this case showed good results of 4–5 and higher. This study thus shows that bio-mordants provide the opportuni­ty to make natural dyeing an eco-friendly process as suitable alternatives to toxic metallic mordants, and thus need to be exploited in the textile industry. The dye extract imparted the anti-oxidant activity onto the cotton fabric, which showed a good radi­cal scavenging activity of between 72.5% and 85.3%. The antioxidant activities were found to be durable, even after several washing cycles. As a result, the dye extract is proposed as an agent for the future development of bioactive, protective and healthy textile fabrics. Acknowledgement This research was supported by the Africa Center of Excellence in Phytochemicals, Textile and Renewable Energy (ACEII-PTRE), to which we are extremely grateful. Thanks also go to the School of Sciences and Aerospace Studies and Department of Chemistry and Biochemistry of Moi University. 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Tekstilec, 2023, Vol. 66(1), 47–56 | DOI: 10.14502/tekstilec.66.2022059 Ievgeniia Romaniuk, Olga Garanina, Yana Red’ko, Natalia Borshchevska, Serhiy Kamenets Serhiy, Kernesh Viktoriia Kyiv National University of Technologies and Design, Nemyrovych-Danchenko str. 2, Kyiv, Ukraine Mathematical Modelling of the Parameters of Braided Textile Tapes Matematicno modeliranje parametrov za izdelavo prepletenih tekstilnih trakov Original scientific article/Izvirni znanstveni clanek Received/Prispelo 8-2022 • Accepted/Sprejeto 2-2023 Corresponding author/Korespondencna avtorica: Ievgeniia Romaniuk Phone: +38 0677962498 E-mail: romanyuk.yo@knutd.com.ua ORCID ID: 0000-0003-4805-959X Abstract Braided textile materials are widely used in many industries and agriculture. Braided tapes are used for domestic purposes, in the food industry, in construction, in medicine, in aircraft manufacturing, in electrical engineering, etc. Every braided product must correspond to a unique group of parameters and properties, depending on the initial manufacturing parameters. The production of braided tapes is still insufficiently explored. In the process of designing and manufacturing products with specified parameters, it is necessary to substantiate the formation of braided products. The manufacture of products with specific parameters and properties, and the creation of rational technological modes for that production represent urgent scientific issues to be addressed. One way to solve this problem is to conduct factorial experiments. This article thus presents the results of a factorial experiment, during which the following input parameters were determined based on preliminary studies: type of raw material, the linear density of raw materials and speed of removal of the product from the formation zone. The following were chosen as output parameters: breaking load, breaking elongation, the linear density of tapes, product width and the number of strands per 10 mm. The limits of factor variation were determined for four types of raw materials. Based on the results of the processing of the obtained experimental data, linear mathematical models were developed. The results of the verification of mathematical models indicated that they adequately describe the process of braiding tapes within the intervals determined by the conditions of the experiment. We thus established a connection between the factors of the braiding process and the properties of braided tapes. Keywords: braided tapes, braiding process, mathematical modelling Izvlecek Prepleteni tekstilni materiali se pogosto uporabljajo v razlicnih industrijah in kmetijstvu. V gospodinjstvu, živilski industriji, gradbeništvu, medicini, letalski industriji, elektrotehniki itd. uporabljajo prepletene trakove. Vsak prepleteni izdelek ima edinstvene lastnosti, ki so odvisne od zacetnih proizvodnih parametrov. Sama izdelava prepletenih trakov je še vedno premalo raziskana. Pri nacrtovanju in izdelavi prepletenih trakov s specificnimi parametri je treba definirati nacin oblikovanja njihove strukture. Izdelava trakov in ustvarjanje gospodarnih tehnoloških postopkov povzrocata znanstvene probleme, ki jih je treba premagati. Eden od nacinov reševanja teh problemov je faktorski poskus. V clanku so predstavljeni rezultati faktorskega poskusa, pri katerem so bili na podlagi predhodnih študij doloceni vhodni (su- Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. rovinska sestava, dolžinska masa niti in hitrost odvajanja oblikovanega traku) in izhodni parametri (izbrane lastnosti koncnega izdelka (traku): pretržna obremenitev, pretržni raztezek in dolžinska masa trakov, širina izdelka in število niti na 10 mm). Za štiri vrste izbranih surovin so bile dolocene meje variiranja faktorjev. Na podlagi rezultatov obdelave eksperimentalnih podatkov so bili razviti linearni matematicni modeli. Rezultati preverjanja matematicnih modelov so pokazali, da ti ustrezno opisujejo proces izdelave prepletenih trakov v intervalih, dolocenih z eksperimentalnimi pogoji. Ugotovljena je bila povezava med dejavniki postopka prepletanja in lastnostmi prepletenih trakov. Kljucne besede: prepleteni trakovi, postopek prepletanja, matematicno modeliranje 1 Introduction The world is witness to the constant development and improvement of the design of braiding ma­chines and their components. Modern technolo­gies, including information technology, are being introduced in production practices. At the same time, there is a wide range of problems and certain issues which hinder further development that re­main insufficiently explored. In addition, the num­ber of scientific works relating to the processing of textile materials is small compared with other technologies. In recent works, it has been determined that braid­ed structures can be tailored for a particular appli­cation by choosing the right set of parameters in or­der to obtain the desired level of properties based on predictive modelling [1]. Problems relating to the mechanical aspects of the braiding process have been investigated for many years and are discussed below. There is a description and analysis of the forces acting in and around the braiding zone, yarn direction, yarn tension, take­off and braiding velocities, all of which affect the quality of braids. Also discussed are connections between the prediction of braiding angles and picks per length, depending on the take-off [2]. Works dedicated to development of 3D braiding technol­ogy can be singled out, as well as research regard­ing the development of 3D braiding technology in terms of fabric, braiding technology and equip­ment. [3, 4]. Interesting is the development and use of software. Computer programs have been developed that are capable of designing geometric models, includ­ing braiding products. These programs include WiseTex, TexMind Software and SolidWorks [5-7]. At the same time, the manufacturers of woven tex­tile materials require modelling between the input parameters of the technological process and the physical and mechanical properties of the finished products. Let us briefly consider the formation of a braid­ed product. The thread forming the braided prod­uct moves simultaneously in two planes. The first movement is provided by the towing device, while the second is caused by the continuous movement of the spindle along its trajectory [2]. On preparatory equipment, raw materials (threads) are spun onto bobbins that are tucked into spindles. On the upper web of the machine, there is a system of horn gears with several notches into which the spindles are installed. The thread is unspun from the bobbin by a towing device and passes into the product formation zone – the place of braiding – where the threads of all systems form the product. The trajectory of the spindle in the horizontal plane is called the move and is a set of connected alter­nating semicircles. Single-stroke and two-stroke are the most widely used machines. In addition to the threads of the braiding system, braided tapes can include threads of the base sys­tem [8]. The warp threads occupy positions in the product along its axis inside the braid. The posi­tion of the braiding threads (Figure 1(a)) is char­acterized by the angle of inclination of the thread relative to the axis of the product (a), the number of strands per 10 mm and the characteristics of the weave repeat (L) [9]. The number of strands can be determined by the horizontal or vertical axis of a product. The number of strands along the horizon­tal axis is used very rarely; it is deemed sufficient to determine the number of strands along the vertical axis, on the track that is parallel to the axis of the product. Conventionally, a weave repeat is the smallest num­ber of threads forming a complete weave pattern [10]. By analogy with a braided structure, the weave repeat of a braided product is the smallest number of threads, in which the order of intersection of the threads of the braiding system is repeated [9]. Typically, the starting point, when determining the repeat (L) of the braided tape, is the point .n-1 (Figure 1(b)), which corresponds to the extreme (a) An˜1 ° An L An+1 (b) An˜1 An An An+1 Figure 1: Schematic illustration of the structure of a braided product (.) and along its forming thread (b): angle to the axis of the product (a), distance of the pattern repeat (L), extreme points of the beginning (.n-1) and end of repeat (.n-1), and change of direction (.n) position that the thread axis can occupy. At the ex­treme points (A, A and A), the thread bends n-1nn+1 along the entire braid, changing the direction of movement to the opposite. Figure 1(b) presents a diagram of a section of a braided tape along the axis of the thread that forms it. In most cases, the threads in a braided product do cross not at a right angle, so cross-sectional images of the threads have the shape of an ellipse. For the convenience of de­picting the section of the thread in the braid, we divide the repeat into two parts. All of the threads that form a braided tape cross twice in one repeat with other threads [11]. 2 Methods To study the mechanism of complex processes in the braiding of textile materials, it is necessary to establish the link between the factors of the process and the properties of the product, and present that link in a compact and convenient form with a quan­titative estimation (in the form of a mathematical model). Traditionally, research methods in the tex­tile industry are associated with experimentation. The methods of optimal experiment planning fa­cilitate the use of mathematical apparatus, not only in the phase of processing the measurement results, but also for preparing and conducting research [12]. Four factorial experiments were carried out on a class 17 flat braiding machine (TP-17-3, produced by Tex-Inter Co. LTD). We chose four types of raw materials for the experiments: cotton thread (25 tex), polyester thread (34 tex), polyamide thread (29 tex) and fiberglass thread (68 tex). These types of raw materials are the most common used today in the production of braided tapes. Nevertheless, it should be noted that raw materials modified using modern methods can also be used to produce wo­ven products [13, 14]. To study the process of braiding tapes using an ex­perimental planning method based on preliminary studies, the following input parameters were deter­mined: breaking load (N); breaking elongation (%); linear density (g/m); width (mm); and the number of strands per 10 mm (s/cm). We chose the following factors to study braided tapes: type of raw material; equipment class; linear density of raw materials (tex); and product with­drawal speed from the formation zone (m/h). All experimental tests were carried out according to current methods and standards [15-17]. 3 Results The limits of variation of the factors given in Table 1 were determined for four types of raw materials and two classes of equipment. Other parameters of the weaving process (such as the height of the braiding point, yarn tension and bobbin winding tension) during the experiment were within technological parameters. The experimental plan and the obtained input pa­rameters are shown in Table 2, where X1 represents the linear density of the raw material (tex), X2 rep­resents product withdrawal speed from the forma­tion zone (m/h), Y1 represents breaking load (N), Y2 represents breaking elongation (%), Y3 represents linear density (g/m), Y4 represents the number of strands per 10 mm (s/cm) and Y5 represents prod­uct width (mm). Table 1: Factors and their levels of variation in the braiding process Type of raw material Factors Variation levels -1 +1 Cotton thread . – linear density of raw material (tex) 1 25 100 . –product withdrawal speed from the formation zone (m/h) 2 57 142 Polyamide thread . – linear density of raw material (tex) 1 29 116 . –product withdrawal speed from the formation zone (m/h) 2 57 142 Fiberglass thread . – linear density of raw material (tex) 1 68 272 . –product withdrawal speed from the formation zone (m/h) 2 57 142 Polyester thread . – linear density of raw material (tex) 1 34 136 . – product withdrawal speed from the formation zone (m/h) 2 57 142 Table 2: Experimental plan and obtained input parameters in the braiding process Type of raw material Experiment number Factor scores Input parameters Coded Natural X1 X2 X1 X2 Y1 Y2 Y3 Y4 Y5 Cotton thread 1 1 1 100 142 238.3 19.2 1.84 2.80 7.6 2 -1 1 25 142 43.15 9.8 0.40 3.70 4 3 1 -1 100 57 218.3 23.6 2.02 6.58 8.9 4 -1 -1 25 57 49.23 10.6 0.42 6.3 3.8 Polyamide thread 1 1 1 116 142 974.78 26.8 2.01 2.4 7.3 2 -1 1 29 142 235.75 23.6 0.49 2.1 3.6 3 1 -1 116 57 923.79 42.2 2.17 5.1 8.2 4 -1 -1 29 57 242.64 18.8 0.50 6.2 4 Fiberglass thread 1 1 1 272 142 967.92 14.8 4.72 3 8.5 2 -1 1 68 142 411.49 8.2 1.14 4.3 3.4 3 1 -1 272 57 929.67 14 5.02 6.2 9.2 4 -1 -1 68 57 421.3 10.2 1.25 5.8 4.8 Polyester thread 1 1 1 136 142 759.6 46.2 2.82 2.7 15.5 2 -1 1 34 142 195.74 41.0 0.74 4 8.2 3 1 -1 136 57 725.3 57.3 2.95 7.18 16.9 4 -1 -1 34 57 193.39 37.4 0.72 7.36 8.7 The calculation of the coefficients of regression equations made it possible to obtain linear equa­tions in encoded values. The resulting equations are given in Table 3, where X1 represents the linear den­sity of the raw material and X2 represents the prod­uct withdrawal speed from the formation zone. The model adequacy hypothesis was tested us­ing Fisher’s F-test. The results of the calculation of F-test values for the obtained linear models are shown in Table 4. The calculated F-test values for the models range from 1.07 to 4.41, and do not exceed the table val­ue of the F-test for a confidence interval of 0.95 and the number of degrees of freedom 1 and 16 equal to 4.49. Taking this into account, the hypothesis that the obtained models adequately describe the pro­cess of tape braiding was confirmed. The significance of the coefficients of regression equations was verified by constructing a confidence interval. Table 5 shows the results of the calculation of the confidence interval for each of the obtained models. Table 3: Mathematical models of braided tape parameters obtained from the results of the experiment Type of raw material Mathematic models Breaking load (N) Cotton thread Y = 137.25 + 91.06X + 3.48X112 Polyamide thread Y = 594.24 + 355.05X + 11.03X112 Fiberglass thread Y = 682.60 + 266.20X + 7.11X112 Polyester thread Y = 468.51 + 273.94X + 9.16X112 Breaking elongation (%) Cotton thread Y = 15.80 + 5.6X - 1.3X212 Polyamide thread Y = 27.85 + 6.65X - 2.65X212 Fiberglass thread Y = 11.65 + 2.45X - 0.45X212 Polyester thread Y = 45.48 + 6.28X - 1.88X212 Linear density (g/m) Cotton thread Y = 1.17 + 0.76X - 0.05X312 Polyamide thread Y = 1.29 + 0.80X - 0.04X312 Fiberglass thread Y = 3.03 + 1.84X - 0.103X312 Polyester thread Y = 1.808 + 1.078X - 0.028X312 Number of strands per 10 mm (s/cm) Cotton thread Y = 4.844 - 0.156X - 1.594X412 Polyamide thread Y = 3.95 - 0.2X - 1.7X412 Fiberglass thread Y = 4.83 - 0.225X - 1.175X412 Polyester thread Y = 5.31 - 0.37X - 1.96X412 Product width (mm) Cotton thread Y = 6.075 + 2.175X - 0.275X512 Polyamide thread Y = 5.775 + 1.975X - 0.325X512 Fiberglass thread Y = 6.475 + 2.375X - 0.525X512 Polyester thread Y = 12.325 + 3.875X - 0.475X512 Table 4: Testing of the model adequacy hypothesis for braided tapes using the F- test Table 5: Confidence interval values for testing the significance of regression coefficients Parameter Type of raw material Variance of the adequacy of the mathematical model Variance of the measurement of the parameter Calculated F-test value Breaking load Cotton thread 170.04 38.95 4.37 Polyamide thread 837.52 425.97 1.97 Fiberglass thread 577.44 164.48 3.51 Polyester thread 255.20 230.91 1.11 Breaking elongation Cotton thread 3.24 1.80 1.80 Polyamide thread 102.01 23.93 4.26 Fiberglass thread 1.21 0.52 2.32 Polyester thread 54.02 12.36 4.37 Linear density Cotton thread 0.01 0.00 2.94 Polyamide thread 0.01 0.00 1.17 Fiberglass thread 0.01 0.00 3.52 Polyester thread 0.01 0.00 2.74 Number of strands per 10 mm Cotton thread 0.35 0.08 4.22 Polyamide thread 0.49 0.11 4.31 Fiberglass thread 0.72 0.17 4.35 Polyester thread 0.31 0.09 3.35 Product width Cotton thread 0.56 0.18 3.17 Polyamide thread 0.06 0.06 1.11 Fiberglass thread 0.12 0.09 1.42 Polyester thread 0.20 0.12 1.64 Parameter Type of raw material Confidence interval value Breaking load Cotton thread 3.323 5.857 Polyamide thread 10.990 24.350 Fiberglass thread 6.83 68.581 Polyester thread 8.092 19.526 Breaking elongation Cotton thread 0.714 1.107 Polyamide thread 2.605 0.871 Fiberglass thread 0.385 0.863 Polyester thread 1.872 1.414 Linear density Cotton thread 0.025 0.064 Polyamide thread 0.037 0.031 Fiberglass thread 0.027 0.221 Polyester thread 0.024 0.046 Number of strands per 10 mm Cotton thread 0.152 0.148 Polyamide thread 0.180 0.108 Fiberglass thread 0.217 0.166 Polyester thread 0.163 0.180 Product width Cotton thread 0.224 0.292 Polyamide thread 0.126 0.170 Fiberglass thread 0.156 0.174 Polyester thread 0.187 0.194 A comparison of the absolute values of the coeffi­cients of regression equations with the correspond­ing values of confidence intervals allows us to con­clude that all the coefficients of regression equations are significant. The value and sign of the coefficient in the linear model, presented in encoded values, determine the influence of a particular factor on the parameter value. 4 Discussion The value of the breaking load is most influenced by the linear density of the raw material. An an in­crease in linear density, within the interval deter­mined by the conditions of the experiment and at a product withdrawal speed from the formation zone of 100 m/h, results in increase in the value of the indicator by 127-394%. Figure 2 illustrates the breaking load response func­tion of braided tapes made on a class 17 machine and the dependence of the breaking load on the lin­ear density of the raw material at a fixed value of the product withdrawal speed from the formation zone (the factor varies within the intervals determined by the experiment). An increase in the product withdrawal speed from the formation zone, within the intervals estab­lished by the conditions of the experiment, result­ed in an increase in the breaking load by 5-20% (at a fixed value of the linear density of the raw mate­rial). It should be noted that tapes made of polyam­ide threads have the highest breaking load value, while tapes made of cotton threads have the lowest value. The greatest influence on the value of the breaking elongation is exerted by the linear density factor of the raw material. An increase in that factor, with­in the values established by the conditions of the experiment, results in an increase in elongation by 32-178%. Figure 3 shows the planes of the response functions of the breaking elongation, as well as the dependency of the breaking elongation of braided tapes made from fiberglass thread and polyester thread at a product withdrawal speed of 100 m/h on the linear density of the raw material. Figure 2: Planes of the response functions of the breaking load of tapes Figure 3: Planes of the response functions of the breaking elongation of tapes Figure 4: Planes of the response functions of the linear density of the tapes An increase in breaking elongation by 7-19% is observed with a fixed value of the linear density of the raw material within the variation interval and a decrease in the product withdrawal speed from the formation zone. The linear density of the product increases with an increase in the value of the linear density of the raw material factor by 295-390%. Figure 4 shows the planes of the response functions of the prod­uct linear density and the dependence of the linear density on the linear density of the raw material at a product withdrawal speed of 100 m/h. The graph is constructed according to linear equations charac­terizing the properties of tapes made from different types of raw materials. The value of the linear density of the product de­creases by 3-12% with an increase in the product withdrawal speed from the formation zone. The greatest influence on the parameter of the num­ber of strands per 10 mm of the product was exerted by the product withdrawal speed from the forma­tion zone, an increase in which led to a decrease in the aforementioned parameter by 39-60%.A de­crease in the number of strands per unit of length of the tape by up to 15% is observed up with an in­crease in the linear density of the raw material at a product withdrawal speed from the formation zone of 100 m/h. The width of the tapes (Figure 5), ceteris paribus, increases by 87-123% with an increase in the lin­ear density of the raw material and by 15% with a decrease in the product withdrawal speed from the formation zone. This indicator depends to a large extent on the linear density of the raw material. 5 Conclusion Based on the data of full factorial experiments, lin­ear models were developed that adequately describe the braiding process within the intervals deter­mined by the conditions of the experiment. A con­nection was established between braiding factors and the properties of a braided product. Analysing the resulting linear models, we can determine the following. The value of the breaking load of the tapes is most influenced by the linear density of the raw material. An increase in linear density, with­in the interval determined by the conditions of the experiment and at a fixed product withdrawal Figure 5: Planes of the response functions of the width of the tapes speed from the formation zone within the interval, results in an increase in the value of the indicator by 127-394%. An increase in the product withdraw­al speed from the formation zone results in an in­crease in the breaking load by 5–20%. The greatest influence on the value of the breaking elongation of the tapes is exerted by the linear density factor of the raw material, an increase in the value of which increases the elongation by 32-178%. An increase in breaking elongation of up to 19% is observed at a fixed value of the linear density of the raw material and a decrease in the product withdrawal speed. The linear density of the tapes increases with an in­crease in the value of the linear density of the raw material by 295-390%. An increase in the product withdrawal speed from the formation zone results in a decrease in the value of the linear density of the product by up to 12%. The greatest influence on the number of strands per 10 mm of tape was exerted by the factor of the prod­uct withdrawal speed from the formation zone, an increase of which led to a decrease in the parame­ter by 39-60%. A decrease in the number of strands per unit of length by 5–15% is observed with an in­crease in the linear density of raw materials. The width of the tapes, ceteris paribus, increases with an increase in the linear density of the raw material by 87-123% and a decrease in the prod­uct withdrawal speed from the formation zone by 4-15%. The data obtained as a result of the studies carried out make it possible to optimally select the parameters of braiding and raw materials for the manufacture of products with the necessary prop­erties at the design stage, which contributes signif­icantly to improving the efficiency of the process of braiding textile materials. References 1. RAWAL, Amit, HARSHVARDHAN, Saraswat, APURV, Sibal. Tensile response of braided struc­tures: a review. Textile Research Journal, 2015, 85(19), 2083-2096, doi: 10.1177/0040517515576331. 2. Braiding Technology for Textiles. Edited by Yordan Kyosev. Elsevier, 2015, 177-209, doi: 10.1533/9780857099211.2.177. 3. 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Tekstilec, 2023, Vol. 66(1), 57–63 | DOI: 10.14502/tekstilec.66.2023012 Göksal Erdem, Timo Grothe, Andrea Ehrmann Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences and Arts, 33619 Bielefeld, Germany Adhesion of New Thermoplastic Materials Printed on Textile Fabrics Adhezija novih termoplasticnih materialov, natisnjenih na tkaninah Original scientific article/Izvirni znanstveni clanek Received/Prispelo 3-2023 • Accepted/Sprejeto 4-2023 Corresponding author/Korespondencna avtorica: Prof. Dr. Dr. Andrea Ehrmann E-mail: andrea.ehrmann@hsbi.de ORCID: 0000-0003-0695-3905 Abstract Combining 3D printing, especially fused deposition modelling (FDM) as a material extrusion technique, with textile fabrics can lead to full-layer composites as well as partly reinforced textiles with different mechanical properties at different positions. While the combination of both techniques enables the production of new kinds of objects different from common fibre-reinforced matrices, the adhesion between both materials is still challenging and the subject of intense research activities. Besides well-known setup and printing param­eters, such as the distance between nozzle and fabric or the extrusion temperature, material combinations, in particular, strongly influence the adhesion between 3D printed polymer and textile fabric. In this study, we investigate composites of woven fabrics from cotton (CO), polyester (PES) and a material blend (CO/PES) with newly developed thermoplastic materials for FDM printing, and show that depending on the FDM polymer, the adhesion can differ by a factor of more than four for different blends, comparing highest and lowest adhesion. Keywords: 3D printing, fused deposition modelling (FDM), high-performance polymers, high-performance polyolefin, fibre-reinforced polymers Izvlecek Kombinacija 3-D tiskanja, še zlasti modeliranja taljenega nanosa (FDM), in tkanine lahko vodi do izdelave laminiranih kompozitov, kot tudi do delne ojacitve tekstilij z razlicnimi mehanskimi lastnostmi na razlicnih predelih. Medtem ko kombinacija 3-D tiskanja na tkanino omogoca izdelavo novih vrst vecslojnih materialov, ki se razlikujejo od navadnih z vlakni ojacenih matric, je adhezija obeh materialov še vedno izziv in predmet intenzivnih raziskav. Poleg dobro znanih parametrov nastavitev tiskalnika in parametrov tiskanja, kot je razdalja med šobo in tkanino ali temperatura ekstrudiranja, na oprijem med 3-D natisnjenim polimerom in tkanino mocno vpliva predvsem kombinacija materialov. V tem clanku so predstavljene raziskave kompozitnih materialov, izdelanih iz bombažnih tkanin, poliestrskih tkanin oziroma tkanin iz mešanice bombaž/poliester in na novo razvitimi termoplasticnimi materiali za tisk s tehnologijo FDM. Ugotovljena je bila vec kot štirikratna razlika med najslabšo in najboljšo adhezijo glede na uporabljene polimere pri 3-D tisku in tkanine. Kljucne besede: 3-D tiskanje, modeliranje taljenega nanosa, FDM, visokozmogljivi polimeri, visokozmogljiv poliolefin, polimeri, z vlakni ojaceni polimeri Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. 1 Introduction In recent years, 3D printing has emerged from a technique that necessitated expensive equipment and was mostly used for rapid prototyping towards a technology that is easily available at low costs, and that is also used for the rapid printing of single ob­jects, from spare parts to gimmicks. Amongst the various additive manufacturing techniques, ma­terial extrusion, in particular FDM printing, has found its way into companies and laboratories, schools and private households due to its ease of use, non-toxic or low-toxic materials and inexpen­sive printers. Nevertheless, the mechanical proper­ties of such FDM printed parts are usually weaker than those of injection moulded objects, since the layer-wise production process leads to a strong ani­sotropy and often induces air voids, further reduc­ing stability [1-3]. Commonly, two different approaches are reported in literature to improve the mechanical properties of FDM printed parts: on the one hand, new fila­ments with improved mechanical properties can be used, e.g. fibre-reinforced polymers [4-6]; on the other hand, macroscopic combinations with mechanically stronger materials are possible, such as textile fabrics. In the latter case, the adhesion between both materials is important to avoid the detaching of the polymer from the fabric under mechanical forces. When combining stereolitho­graphy (SLA) printed areas on textile fabrics, low-viscous resin can easily penetrate into even fine fabrics [7], while FDM printed objects often adhere better to thicker fabrics with relatively large pores [8, 9]. Besides the fabric structure, primarily the nozzle-fabric distance influences the adhesion due to form-locking connections [10, 11], while the printing bed temperature [12, 13], chemical pre­treatments [14, 15] or thermal post-treatments [16, 17] can also influence adhesion. It has also been shown that soft thermoplastic materials printed with FDM often have a higher adhesion on textile fabrics than rigid ones and, amongst the latter, that Table 1: Textiles used in this study poly(lactic acid) (PLA) demonstrates higher adhe­sion on examined textile fabrics than acrylonitrile butadiene styrene (ABS), while nylon has higher or lower adhesion than PLA, depending on the sub­strate [18, 19]. That is why this study investigates six newly de­veloped FDM filaments, partly glass or carbon fibre-reinforced, invented by Grauts GmbH [20]. We describe the filaments, having different elastic prop­erties, and show their strongly varying adhesion on three different textile fabrics. 2 Materials and methods The textile fabrics used in this study are depicted in Table 1. The pure CO and PES fabrics have a similar structure, while the CO/PES woven fabric is thick­er and has a higher mass per unit area. The latter value was measured using an SE-202 analytical balance (VWR International GmbH, Darmstadt, Germany), while the fabric thickness values were measured using a J-40-T digital thickness gauge (Wolf-Messtechnik GmbH, Freiberg, Germany). Printing was performed using an Orcabot XXL Pro 2 FDM printer (Prodim, The Netherlands), ena­bling printing with an extrusion temperature of up to 285 °C. The printing parameters for all filaments were as follows: nozzle diameter: 0.4 mm; layer height: 0.2 mm; unheated printing bed; 100% linear infill in ± 45° orientation; two perimeters; printing speed: 30 mm/s; and z-distance between nozzle and printing bed: 0.5 mm. A relatively high z-distance was chosen because it is well-known that near the optimum z-distance, even the smallest deviations have a large impact, while around the setting where the nozzle just slightly touches the fabric, this impact is almost negligible [10]. Thus, the chosen z-distance facilitated the comparison of the slightly thicker CO/ PES fabric with thinner fabrics. The extrusion tem­peratures were optimized in pre-tests and were set in the range 230 °C to 250 °C, as depicted in Table 2. Sample Material Structure Mass per unit area (g/m²) Thickness (mm) CO 100% cotton Plain weave 150 0.50 PES 100% PES Plain weave 160 0.50 CO/PES 70% CO, 30% PES Plain weave 205 0.65 Table 2: Thermoplastic materials for FDM processing and corresponding printing temperatures. HPP = high-performance polyolefin Filament name Material Shore hardness Extrusion temp. (°C) PA+Carbon Polyamide / 15% carbon fibres 75 D a) 250 Mid GF 1461 Polyamide / 15% glass fibres 80 D a) 235 Mid GF 1613 Polyamide / 15% glass fibres 93 D a) 230 HPP+GF 1443 HPP / 15% glass fibre 84 D a) 230 HPP 1444 HPP 52 D 235 HPP 1476 HPP 57 D 235 a) Values measured using a PCE-DD-D durometer (PCE Instruments, Meschede, Germany) on 3D printed parts with 100% infill; other Shore hardness values were provided by the manufacturer. This table also describes the FDM printing polymers. These filaments were chosen, since they have strong mechanical properties and can withstand much higher temperatures than PLA and other common thermoplastic materials used in FDM. Samples were designed according to DIN 53530, using Autodesk Fusion, as rectangles with an area of 150 mm × 25 mm and a height of 0.4 mm (i.e. two printed layers). Adhesion tests were performed using Sauter FH2K and Zwick-Roel Z010 universal test machines according to DIN 53530 and evaluat­ed according to ISO 6133, procedure B, taking into account the median of the measured adhesion force peaks for each sample. Three specimens were inves­tigated for each combination of filament and tex­tile fabric. Microscopic images were taken using a Camcolms2 digital microscope. 3 Results and discussion The results of the adhesion force measurements are depicted in Figure 1. Since the z-distance is not op­timized, the values are generally smaller than pos­sible with these material combinations. The largely small error bars, however, indicate the reliability of the measured values. Of all fabrics included in this study, the HPP 1444 filament shows the lowest adhesion. Much larger values are visible for HPP 1476, in particular, but also for the Mid GF 1461 and Mid GF 1470 glass-fi­bre reinforced filaments. It should be mentioned that Mid GF 1461 could not be printed properly on the PES fabric, so these values are omitted. Unexpectedly, the CO/PES woven fabric, although thicker than the pure CO and PES fabrics, most­ly shows smaller adhesion values than the others, Figure 1: Adhesion forces between different textile fabrics (coloured) and novel FDM printing filaments while no large differences between CO and PES are visible. However, most of these differences are insignificant. To evaluate these results, they can be compared with other 3D printing filaments reported in literature, using results that were measured for the nozzle just touching the textile surface. Some results found in literature (approximated for a z-distance identical with the fabric thickness) are given in Table 3. As this comparison shows, the adhesion reached with the recently tested filaments is higher than some of the other results, but there are also adhesion forces more than twice the values measured in this study. One possible reason is that the new filaments tested in this study are high-temperature filaments, which should possibly be printed at even higher tem­peratures than in this study to reduce their viscos­ity during printing and enable deeper penetration into the textile fabrics under examination. Previous Table 3: Values found in literature for adhesion forces, measured at or approximated for a z-distance identical to the fabric thickness. TPU = thermoplastic polyurethane (here with Shore hardness 86A), TPS = thermoplastic styrene (here with Shore hardness 67A and 79A) Textile fabric Fabric thickness (mm) Filament material Adhesion force (N/cm) Ref. Cotton woven 0.21 PLA 2 [10] Polyester woven 0.19 PLA 0.5 [10] Polyester woven 0.51 PLA 18 [10] Polyester woven 0.51 ABS 3 [10] Polyester woven 0.51 PA 6.6 11 [10] CO/PES woven 0.45 TPU 2-86A 26 [17] CO/PES woven 0.45 TPS1-67A 8 [17] CO/PES woven 0.45 TPS2-79A 3 [17] Cotton woven 0.49 PLA 8 [21] Cotton woven 0.37 PLA 8 [21] Cotton woven 0.39 PLA 16 [21] Cotton woven 0.74 PLA 24 [21] CO, PES, CO/PES 0.5-0.65 HPP 1476 8-11 This work results from literature show that the shift in opti­mum z-distance is strongly correlated with the ex­trusion temperature [21], meaning future tests with increased printing temperatures are necessary. On the other hand, previous studies showed that the textile fabrics used also played an important role, not only due to their pore dimensions, but also with respect to the fibre lengths in the fabrics, where hairy fabrics with long – and thus well-fixed – fibres in the yarn resulted in higher adhesion than fabrics from short-staple yarns, where the fibres are more easily pulled out of the yarn and thus cannot fix the imprinted polymer layers properly. To investigate this possibility, Figure 2 shows mi­croscopic images of the detached back of different polymers printed on the cotton fabric under inves­tigation here. On the back of the black filaments, white cotton fibres are clearly visible, especially on the sample from the Mid GF 1470 filament. This matches the results of the adhesion tests where both Mid GF filaments gave high values on the cotton fabric. For HPP 1444, only very few fibres are visi­ble, while a more in-depth look at HPP 1476 shows several fibres, but with optically reduced contrast on the blue filament. None of the images on HPP 1444 reveals more than a few fibres, which is in line with the finding that this filament has the lowest adhesion of all three textile fabrics. It should be mentioned, however, that here only small parts of the printed samples are depicted and that variations of the amount of fibres stuck on the polymer are vis­ible for all samples. While the filaments investigated here do not reach the maximum adhesion forces reported in previous studies, most of them (especially HPP 1476) show re­liable adhesion on all three tested textile fabrics. Due to their good mechanical properties and high heat distortion temperature, compared with PLA, further experiments in combination with other fabrics, at higher extrusion temperatures and with optimized z-distance will be performed to enable the use of these filaments in composites for high-temperature applications or improved mechanical properties. 4 Conclusion and outlook Six new filaments were FDM printed on different woven fabrics. Most of them showed reliable adhe­sion forces on PES, CO and CO/PES fabrics and fi­bre bundles attached to their back after separation during adhesion tests. The largest differences were found between two high-performance polyolefin materials, unexpectedly with the softest material (HPP 1444) having the lowest adhesion amongst the tested samples. The chosen substrates did not have a significant influence on adhesion to the thermo­plastic materials printed on them. Figure 2: Back of the printed polymer, detached from cotton fabrics by adhesion tests according to EN 53530 Future tests will concentrate on optimizing the z-distance between fabric and printing nozzle, as well as the extrusion temperature, and on the inves­tigation of more fabrics with different woven struc­tures to further improve adhesion, so that applica­tions, especially in high-temperature surroundings where PLA cannot be used, are enabled. Acknowledgments The authors would like to thank Grauts GmbH, Löhne, Germany, for providing the special thermo­plastic materials for FDM printing. The study was partly funded by the German Federal Ministry for Economic Affairs and Climate Action via the AiF, based on a resolution of the German Bundestag, grant no. KK5129708TA1. References 1. POPESCU, Diana, ZAPCIU, Aurelian, AMZA, Catalin, BACIU, Florin, MARINESCU, Rodica. FDM process parameters influence over the mechanical properties of polymer specimens: a review. 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Testing thermoplastic elastomers selected as flexible three-dimensional printing materials for functional garment and technical textile applications. Journal of Engineered Fibers and Fabrics, 2020, 15, 1-10, doi: 10.1177/1558925020924599. 18. PEI, Eujin, SHEN, Jinsong, WATLING, Jennifer. Direct 3D printing of polymers onto textiles: experimental studies and applications. Rapid Prototyping Journal, 2015, 21(5), 556-571, doi: 10.1108/RPJ-09-2014-0126. 19. SANATGAR, R.H., CAMPAGNE, C., NIERSTRASZ, V. Investigation of the adhesion properties of direct 3D printing of polymers and nanocomposites on textiles: effect of FDM printing process parameters. Applied Surface Science, 2017, 403, 551-563, doi: 10.1016/j.apsusc.2017.01.112. 20. Print your ideas with our filament [online]. Grauts [accessed 4. 3. 2011]. Available on World Wide Web: . 21. SPAHIU, T., AL-ARABIYAT, M., MARTENS, Y., EHRMANN, A., PIPERI, E., SHEHI, E. Adhesion of 3D printing polymers on textile fabrics for garment production. IOP Conference Series: Materials Science and Engineering, 2019, 459, 1-6, doi: 10.1088/1757-899X/459/1/012065. Tekstilec, 2023, Vol. 66(1), 64–72 | DOI: 10.14502/tekstilec.66.2022108 Manar Y. Abd El-Aziz, Z. M. Abdel-Megied, K. M. Seddik Clothing and Knitting Industrial Research Department, Textile Research and Technology Institute, National Research Centre, 33 El Buhouth St, Ad Doqi, Dokki, Cairo 12622, Egypt Enhancement Reinforcing Concrete Beams Using Polypropylene Cord-Knitted Bars Izboljšanje ojacitve betonskih nosilcev s pletenimi kompozitnimi palicami iz polipropilenskih vrvic Original scientific article/Izvirni znanstveni clanek Received/Prispelo 12-2022 • Accepted/Sprejeto 4-2023 Corresponding author/Korespondencni avtor: Dr. Manar Yahia Email: manar_yahia@hotmail.com ORCID ID: 0000-0002-8254-8277 Abstract Currently, technical fabrics play a major role in many industries due to their multiple characteristics. The aim of this research was to utilize composite knitted bars to reinforce concrete beams. Six cord-knitted samples with two different polypropylene yarn counts (outer layer) and three different core materials were manufactured and immersed in a local epoxy material (Kemapoxy 150). Composite knitted bars were prepared in this way. Several tests were conducted for fabrics and knitted bar samples. All data were collected and analysed using two different tools: ANOVA test and radar chart area. Finally, three concrete beams with a varying number of cord-knitted bars (one bar, two bars and three bars) were produced. The results indicated that the differences in outer and core yarns for cord-knitted samples have a significant effect on several fabric and bar character­istics. The knitted bars with PP core yarn can be more beneficial for concrete that do does not require high stress, while the knitted bars using glass fibres and polypropylene (50% and 50% PE) as core materials are not appropriate for applications that require more flexibility and extensibility. Reinforced concrete beams were im­proved significantly with cord-knitted bars, taking into account the number of bars per area, which may cause the minimizing of flexure force through an increase in that number of bars per area. Keywords: cord-knitted, cement, construction, mortar, strength Izvlecek Tehnicne tkanine so zaradi mnogoterih lastnosti pomembne v številnih panogah. Namen te raziskave je bil uporabiti pletene kompozitne palice za ojacitev betonskih nosilcev. Pletene vrvice, izdelane iz polipropilenskih prej v zunanji plasti in jedra iz združenih prej, so bile potopljene v lokalno dostopno epoksismolo Kemapoxy 150. Izdelanih je bilo šest vzorcev pletenih kompozitnih palic iz dveh polipropilenskih prej razlicne dolžinske mase in s tremi razlicnimi jedri. Opravljenih je bilo vec testiranj pletenih vrvic in pletenih kompozitnih palic. Vse meritve so bile statisticno analizirane (ANOVA) in prikazane s pomocjo polarnih grafikonov. Izdelani so bili trije betonski nosilci z eno, dvema oziroma tremi pletenimi kompozitnimi palicami. Rezultati so pokazali, da razlicne preje v zunanji plasti in jedru pomembno vplivajo na lastnosti pletenih vrvic in pletenih kompozitnih palic. Pletene kompozitne palice z jedrom iz polipropilenske preje so primerne za betonske nosilce, ki ne zahtevajo velikih obremenitev. Pletene kompozitne palice iz steklenih vlaken oziro-ma iz 50 odstotkov polipropilenskih in 50 odstotkov polietilenskih vlaken niso primerne za aplikacije, kjer sta zahtevani Content from this work may be used under the terms of the Creative Commons Attribution CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Authors retain ownership of the copyright for their content, but allow anyone to download, reuse, reprint, modify, distribute and/or copy the content as long as the original authors and source are cited. No permission is required from the authors or the publisher. This journal does not charge APCs or submission charges. vecja upogibljivost in raztegljivost betonskih nosilcev. Pletene kompozitne palice so izboljšale ucinkovitost armiranih betonskih nosilcev, pri cemer je bila ugotovljena najvecja upogibna sila pri uporabi dveh palic na betonski nosilec. Kljucne besede: pletenina, cement, gradbeništvo, malta, trdnost 1 Introduction Recent advances in textile production technolo­gy have led to its use in many applications, such as medical, agricultural, aerospace, filtering, etc., due to its unique properties. These textiles are known as technical textiles [1]. Technical textiles are defined as “Textile materials and products manufactured primarily for their technical and performance prop­erties rather than their aesthetic or decorative cha­racteristics” [1]. The corrosion of steel bars (rebar) used for reinforc­ing concrete is a major factor in reducing the service lifetime of reinforced concrete constructions. Thus, the solution is to cover or replace rebars with non­corrosive materials [2]. Textile reinforced concrete is a new advanced composite material. It generally comprises alkali-resistant fibreglass (AR) or carbon fibres with cementitious matrix reinforcement, in contrast to steel reinforcement. The single fibres of glass or carbon AR can be positioned in textile in any direction, which results in the adopted perfect orientation of an applied load [3]. The use of polypropylene fibres (PP) in concrete increases the concrete’s tension and compressive strength [4, 5]. PP fibres are hydrophobic and have a melting point of about 160 °C [6]. When used in concrete, the yarns of PP create pathways in the concrete to evaporate moisture. PP fibres have been used in concrete to reduce cracking, increase tough­ness and impact resistance, and thus improve the energy absorption capacity of the concrete [7-9]. Many studies have shown that adding a small amount of PP fibres to fresh concrete can signifi­cantly reduce plastic cracking in the early stages, while these fibres can also significantly limit surface cracking and aggregate settlement in fresh concrete, reducing the possibility of setting cracks [7, 10]. Textile composites are stiff materials (enhanced by fibres, yarns and different fabric materials) that have properties, such as light weight, flexibility, solid construction and toughness. They have been em­ployed for structural or load-bearing applications due to their outstanding quality [11, 12]. Rebars made of glass fibre-reinforced polymers pro­vide various advantages over standard reinforced steel, including a higher ratio, greater corrosion re­sistance, and greater fatigue load resistance. A lack of ductility, however, is one of the key drawbacks of GFRP rebars [13, 14]. Fibre-reinforced polymers (FRP) provide special benefits to address a variety of civil engineering issues in situations when traditional materials fall short of expectations. Unlike steel, FRP can with­stand the corrosive effects of acids, alkalis, salts, and other similar hostile compounds, without be­ing damaged by electrochemical degradation. FRP is widely recognised as a steel substitute in appli­cations where steel is susceptible to the significant risk of corrosion due to its superior properties, in­cluding high tensile strength and corrosion resist­ance [13, 14]. Tarek Elsayed et al. suggested the use of aramid, carbon and glass fibres via pultrusion to produce local rebars [14]. Knitting techniques usually give fabrics unique performance characteristics due to their yarn-loop­ing shape [15, 16]. Those types of knitted fabrics have been employed as textile reinforced concrete (TRC) for concrete reinforcement in some stud­ies [17]. In the same context, the cord-knitted fab­ric is considered one type of knitted fabric that is produced in a tube shape with different structures using a very small diameter of a circular knitting machine. Inlay warp, weft, and core yarns can be added for cord construction, where the final appli­cations of the cord-knitted fabrics are affected by tightness factors [18]. The available commercial materials for the TRC sys­tem were basalt, carbon, glass and polyphenylene fabrics with different construction. Mortar must have fine grains, good workability, plastic consist­ency, low viscosity (to facilitate application on steep or vertical surfaces) and sufficient shear strength (to keep the composite material from peeling away from the substrate) [19, 20]. Taking into account earlier studies, this research aimed to utilize PP fibres to design and produce bars as a composite technique with a cord-knitted fabric for reinforcing concrete beams (which is an economical material for this application) and evalu­ate its performance. 2 Materials and methods Six cord-knitted samples were fabricated with a plain structure and constructed with two layers (outer and core). Two different yarn counts from PP yarn (133 tex and 267 tex) were used for the outer layer, while three different materials with the closest yarn counts were used for the core layer as present­ed in Table 1. Figure 1 illustrates the experimental­ly manufactured cord-knitted samples and cross section. 2.1 Manufacture of cord-knitted samples A cord-knitting machine with a cylinder diameter of 6 mm, and eight needles was used to manufac­ture the six polypropylene cord-knitted samples. Figure 2 shows a cord-knitting machine and its specifications. 2.2 Preparation of composite cord-knitted fabrics Kemapoxy 150 (solvent-free, transparent epoxy) commercial resin from the company CMB was used for the preparation of composite bars as shown in Figure 2: Cord knitting machine – internal cylinder diameter (cord diameter) = 6 mm Quantity of needles: 8needles per diameter; machine speed: 800-1200 rpm; no creel needed and cones can be installed directly on the machine; automatic stop-motion system with tensioner configuration (a) (b) Figure 1: Cord-knitted fabrics: a) produced PP cord-knitted fabrics, b) cord-knitted cross section Table 1: Experimental design of manufactured cord-knitted fabrics Sample code Outer layer Core layer Material Yarn count (tex) Material Yarn count (tex) 1 PP a) 267 PP a) approx. 156 2 PP a) 267 GF b) 3 PP a) 267 50% PP/50% PE c) 4 PP a) 133 PP a) 5 PP a) 133 GF b) 6 PP a) 133 50% PP/50% PE a) polypropylene, b) glass fibre, c) polyethylene Figure 3. In order to prepare Kemapoxy 150, com­ponent B (hardener) was added to component A (resin) and manually mixed for three minutes. The cord-knitted fabrics were then immersed in a mixture for one minute, removed and put on a flat surface. The air was then vacuumed from the fab­rics to obtain a stiffer shape and rough surface after drying. (a) (b) Figure 3: Coated samples (a) by Kemapoxy (b) 2.3 Reinforcement of concrete beams with composite cord-knitted bars The concrete mix was prepared with the mix­er shown in Figure 4 using the proportions pre­sented in Table 2. One blank concrete beam and three groups of concrete beams measuring 50 cm × 10 cm × 10 cm were then produced. The first group of concrete beams was reinforced with one prepared PP cord-knitted bar, the second group of concrete beams was reinforced with two prepared PP cord-knitted bars and the third group of con­crete beams was reinforced with three prepared PP cord-knitted. Figure 5 shows the pouring of reinforced prepared beams and Figure 6 shows rein­forced concrete beams with PP prepared bars. Cement (kg) Water (kg) Super plasticizer (L) Sand (kg) Coarse aggregate (kg) 325 146 4.8 765 1145 Figure 5: Pouring reinforced beams with PP prepared bars Figure 6: Reinforced concrete beams with PP prepared bars 2.4 Testing and analysis Standard tests were used to test cord-knitted fab­rics, composite bars and reinforced concrete beams, as described below. 2.4.1 Fabric testing According to standard methods, tests were conduct­ed on cord-knitted fabrics to determine their stitch length [21], tightness factor [22-26], longitudinal weight [27], thickness [28], bending length [29] and tensile force [30]. All tests were carried out according to standard conditioning, as described in test meth­od BS 1051 for textile testing, where all samples were placed for 24 hours at a temperature of 20 °C ± 2 °C and a relative humidity (RH) of 65 % ± 2 %. 2.4.2 Testing of composite cord-knitted bars At the national research centre, all prepared com­posite samples were examined for the bars’ longi­tudinal weight [27], diameter and tensile force [31], in accordance with standard methods to investigate any potential effects on the application of reinforced concrete beams. 2.4.3 Testing of reinforced concrete beams One of the key metrics for describing concrete strength is flexure strength. It is a measurement of a beam’s or slab’s resistance to bending failure. According to the ASTM C293 standard test method (centre point loading) [32], flexure strength is test­ed in the lab of the Housing and Building National Research Centre by applying a point load to con­crete beams in the middle of a span length. Figure 7 shows the flexure of a beam that has been reinforced with bars made from PP cord-knitted textiles. Table 3: Tests results of PP cord-knitted samples 2.5 Data analysis All results were collected and analysed using two different tools: an ANOVA test with a P-value of = 0.05 was performed in order to identify the sig­nificant/insignificant effect of different variables on the production of bars, while a radar chart area was calculated and plotted in order to rank the samples and assign the preferable performance characteristics. 3 Results and discussion 3.1 Physical and mechanical characterizations Cord-knitted samples were tested and tabulated to compare their characteristics, as shown in Table 3. The findings show that the cord-knitted bars with a core PP yarn (samples No. 1 and 4) achieved the lowest fabric thickness and fabric tensile force, as well as the highest tightness factor and elongation percentage relative to other cord-knitted samples. Furthermore, the cord-knitted bars with core glass fibres (GF) (samples No. 2 and 5) attained the high­est fabric weight/length at one meter and the lowest elongation, while the cord-knitted bars with a core of 50% PP/50% PE (samples No. 3 and 6) achieved the highest fabric thickness, bending length and tensile force. The reason can be traced to variation in the density and elasticity of the core yarns, which are seen in several knitted-bar characteristics. As a result of the above, prepared composite bars of cord-knitted samples were tested, and the findings are presented in Table 4. The findings show that the bar samples prepared with PP as a core material achieved the lowest weight, diameter and tensile force (N). On the other hand, the bar samples prepared with GF achieved the highest weight, medium diam­eter and tensile force, while the bar samples prepared with 50% PP/50% PE achieved a medium weight, and the highest bar diameter and tensile force, emphasiz­ing the unique and significant effect of core yarns on the characteristics of bar samples. No. Stitch length (cm) Tightness factor Weight (kg) Thickness (mm) Bending length (cm) Tensile force (N) Elongation (%) 1 0.2 5.74 0.147 5.1 33.5 1120 32.77 2 0.228 5.03 0.163 5.8 40 1670 4.32 3 0.247 4.65 0.126 6.3 40 2190 18.73 4 0.251 6.47 0.189 6.4 32.5 1180 73.32 5 0.255 6.37 0.218 6.5 37 1290 5.25 6 0.286 5.68 0.167 7.3 42.5 2990 59.92 Table 4: Tests results of PP cord-knitted prepared bars Sample no. Bar weight (kg) Bar diameter (mm) Bar tensile force (N) 1 0.028 5.9 1800 2 0.033 5.9 2620 3 0.032 6.3 3370 4 0.031 6.5 1770 5 0.037 6.7 2240 6 0.034 7.3 3360 3.2 Significant/insignificant effect In order to explain the effect of different variables in the production of samples, an ANOVA test with a P-value of = 0.05 was performed, with the results shown in Tables 5 and 6. The results indicate that the difference in outer PP yarn count (133 tex and 267 tex) has a significant effect on the stitch length, weight and thickness characteristics of cord-knitted samples, and on the diameter characteristic of the prepared composite bars. Moreover, the results in­dicate that the variation of core yarns only had sig­nificant effect on the fabric weight of the cord-knit­ted fabric, and on the tensile force of the prepared composite bars. Table 5: ANOVA results of PP cord-knitted samples Characteristics P-value Outer count yarns Core materials Stitch length (mm) 0.030139 a) 0.077754 Sample weight (g) 0.008714 a) 0.028537 a) Sample thickness (mm) 0.028714 a) 0.074176 Sample bending length 0.785166 0.098936 Sample tensile force (kN) 0.687811 0.135106 Sample elongation (%) 0.174346 0.176963 a) Significant effect 3.3 Ranking of samples In order to determine preferable performance char­acteristics, radar chart areas were calculated and plotted for all samples, as shown in Figure 8 and Table 7. The results indicate that the cord-knit- Table 6: ANOVA results of PP cord-knitted prepared bars Characteristics P-value Outer count yarns Core materials Bars’ weight (g) 0.31687 0.269231 Bars’ diameter (mm) 0.020204 a) 0.088235 Bars’ tensile force (kN) 0.364074 0.016863 a) a) Significant effect ted sample No. 6 (PP 266 tex, 50% PP/50% PE core yarn) achieved the highest behavioural character­istics, while the cord-knitted sample No. 5 (PP 133 tex, GF core yarn) recorded the lowest. Moreover, the results indicate that the cord-knitted sample No. 1 with a core yarn PP and outer PP yarn count of 133 tex ranked highest among other samples with the same outer PP yarn count, while the cord-knit­ted sample with a core yarn PP and outer PP yarn count of 266 tex ranked second. We can thus con­clude that the PP yarns had a significant effect on produced cord-knitted performance characteristics. Fabrics’ longitudinal weight (gm) 100 Fabrics’ Fabrics’ elongation (%) Thickness (mm) Fabrics' tensile force Fabrics’ bending length (KN) (cm) sample No 1 sample No 2 sample No 3 sample No 4 sample No 5 sample No 6 Figure 8: Radar chart for PP cord-knitted fabric samples At the same time, radar chart areas for prepared composite bars were calculated and plotted, as seen in Figure 9 and Table 8. The result indicate that samples with 50% PP/50% PE core yarn ranked highest at different yarn counts of outer PP yarn, while samples with PP core yarn ranked lowest at different outer PP yarn counts, despite achieving a preferable rank among cord-knitted samples. This could be attributed to the decreasing tensile force of PP yarns compared with other materials (glass fibres and 50% PP/50% PE), an indication that its Table 7: Radar chart for PP cord-knitted fabrics Sample no. Weight (%) Thickness (%) Bending length (%) Tensile force (%) Elongation (%) Radar chart area Rank 1 85.7 100 97.01 37.4 44.6 26070.41 3 2 77.2 87.9 81.2 55.8 5.89 18312.8 5 3 100 80.9 81.2 73.2 25.5 23823.32 4 4 66.6 79.6 100 39.4 100 26478.26 2 5 57.7 78.4 87.8 43.1 7.16 15159.14 6 6 75.1 69.8 76.4 100 81.7 30964.57 1 Table 8: Radar chart area calculation for prepared bars Sample no. Weight (g) Thickness (mm) Bar tensile force (kN) Radar chart area Rank 1 100 100 53.4 17911.6 5 2 84.8 100 77.7 19793.8 2 3 87.5 93.7 100 22784.7 1 4 90.3 90.8 52.5 15337.2 6 5 87.5 88 66.5 16778.8 4 6 75.7 80.8 99.7 18809.7 3 potential use in various applications does not re­quire high stress. At the same time, the other ma­terials may be inappropriate for applications requir­ing more flexibility and extensibility. force (KN) diameter (mm) sample No 1 sample No 2 sample No 3 sample No 4 sample No 5 sample No 6 Figure 9: Radar chart for PP prepared bars 3.4 Results for reinforced concrete beams Concrete beams reinforced with composite PP cord-knitted bars (PP 133 tex, PP core yarn) were produced. Three different composite cord-knit­ted bars (one, two and three bars) were applied to concrete beams, while a basic concrete bar with­out cord-knitted fabric was also tested. The flex­ure forces of basic and reinforced concrete beams were tested, as shown in Table 9. The results con­firm that, although PP bars (PP core yarn, PP out­er yarn) achieved the lowest tensile force (kN) as seen in Table 3, they enhanced reinforced concrete beams using varying numbers of cord bars, indi­cating that other prepared cord-knitted bars with altered cores yarn could further improve rein­forced concrete beams. Additionally, the results in­dicate that the number of bars per area impacts the flexure force of reinforced concrete beams, as ex­ceeding a certain limit might reduce flexure force, where beam No. 3 with three bars achieved the lowest force and beam No. 2 with two bars achieved the highest force. Table 9: Flexure force results for concrete beams rein­forced with polypropylene cord-knitted prepared bars Sample no. Number of bars Reinforcing bar material Flexure force (kN) Basic 0 No reinforcing 10.5 Beam 1 1 PP 14.7 Beam 2 2 PP 15.7 Beam 3 3 PP 13.5 4 Conclusion Based on the results reported in this study regard­ing the use of cord-knitted PP fabrics to reinforce concrete beams, the following main conclusions can be drawn: • The variance of outer PP yarn count (133 tex and 266 tex) and core yarns has a significant effect on several cord-knitted fabric and bar characteristics. • Although the cord-knitted fabric with PP out­er and core yarns did not achieve the highest results (depending on radar area), it did have a significant effect on the samples’ performance characteristics. • According to the testing of knitted bars, the po­tential use of bars with PP core can be excluded for applications that require high stress. On the other hand, the knitted bars with core materials glass fibres and 50% PP/50% PE are not suitable for applications requiring more flexibility and extensibility. • Cord-knitted bars enhanced reinforced concrete beams effectively, while the number of bars per area should be considered during the production of reinforced concrete beams, as exceeding a cer­tain limit might reduce flexure force. Acknowledgement The authors would like thank the National Research Centre and the Housing and Building National Research Centre for testing the samples from this study in their labs. References 1. Handbook of technical textiles. Edited by A. R. Horrocks and S. C. Anand. Cambridge : Woodhead Publishing, 2000, 1-4. 2. PARK, K.T., KIM, H.Y., YOU, Y.J., LEE, S.Y., SEO, D.W. Hybrid FRP reinforcing bars for concrete structures. In 4th Asia-Pacific Conference on FRP in Structures, Melbourne, 2013. Ontario : International Institute for FRP in Construction, 2013. 3. 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