296 Zbigniew Draczynski1, Sandra Flinčec Grgac2, Tihana Dekanic2, Anita Tarbuk2, Maciej Bogun1 'todž University of Technology, Faculty of Material Technologies and Textile Design, Department of Material and Commodity Sciences and Textile Metrology, Stefana Zeromskiego 116, 90-924 todž, Poland 2University of Zagreb, Faculty of Textile Technology, Department of Textile Chemistry and Ecology, Prilaz baruna Filipovica 28a, 10000 Zagreb, Croatia Implementation of Chitosan into Cotton Fabric Implementacija hitozana na bombažni tkanini Original Scientific Article/Izvirni znanstveni članek Received/Prispelo 08-2017 • Accepted/Sprejeto 10-2017 Abstract Chitosan, produced through chitin hydrolysis, has been highly appreciated for medical purposes. For the last decade, its application in textiles and biomaterials has grown significantly. It has been well-implemented in man-made fibre, but achieved properties in natural fibres have not proven durable. Thus, in this study, two chitosans with differing degrees of deacetylation were implemented into cellulose material using a mercer-isation process. The following methods of analysis were used for physical-chemical characterisation: Fourier-transform infrared spectrometry (FTIR), electrokinetic potential, scanning electron microscopy (SEM) and thermal gravimetric analysis. For the purpose of studying durability, characterisation was performed after one washing cycle. Performed analyses confirmed that both chitosans are well-implemented into cellulos-ic fabric. Fabric treated with chitosan with a higher degree of deacetylation has more positively charged amino groups and better thermal stability. Keywords: chitosan, cotton fabric, FTIR, electrokinetic potential, FE-SEM, thermal gravimetric analysis Izvleček Hitozan, ki nastane s hidrolizo hitina, je zelo cenjen v medicini. V zadnjem desetletju se je njegova uporaba v tek-stilstvu in biomaterialih znatno povečala. Uspešno je bil uporabljen v kemičnih vlaknih, na naravnih vlaknih pa dosežene lastnosti niso bile trajne. V tem članku je predstavljena uporaba dveh hitozanov različne stopnje deaci-tiliranja, ki sta bila na celulozni material nanešen z mercerizacijo. Za fizikalnokemijsko karakterizacijo so bile uporabljene analitične metode, kot so infrardeča spektrometrija s Fourierjevo transformacijo (FTIR), merjenje elektro-kinetičnega potenciala, vrstična elektronska mikroskopija (SEM) in termična gravimetrija. Raziskave obstojnosti so bile ocenjene po enem ciklusu pranja. Analize so potrdile dobro obstojnost obeh vrst hitozana na celulozni tkanini. Tkanina, obdelana s hitozanom z višjo stopnjo deacetiliranja, je imela več pozitivno nabitih amino skupin in boljšo termično stabilnost kot tkanina, obdelana s hitozanom z nižjo stopnjo deacetiliranja. Ključne besede: hitozan, bombažna tkanina, FTIR, elektrokinetični potencial, FE-SEM, termična gravimetrija 1 Introduction Chitosan is the (P-1,4) linked D-glucosamine derivative of the polysaccharide chitin (poly N-acetyl-d-glucosamine) found in the outer shell of crustaceans (e.g. shrimp and crab). Chitosan is usually produced through the alkaline hydrolysis of chitin, a process that results in N-deacetylation and depolymerisa- Corresponding author/Korespondencna avtorica: dr. sc. Anita Tarbuk, doc. E-mail: anita.tarbuk@ttf.hr tion. Chitosan has been highly appreciated for medical purposes, such as antibacterial wound dressings and drug delivery systems, and for enhancing immune activities [1-15]. For the last decade, its application in textiles and biomaterials has grown significantly [2-13]. It has been well-implemented in man-made fibre, but achieved properties in natural fibre have not proven durable Tekstilec, 2017,60(4), 296-301 DOI: 10.14502/Tekstilec2017.60.296-301 Implementation of Chitosan into Cotton Fabric 297 [3, 7, 9]. Because the antimicrobial property of chitosan is strongly affected by molecular weight, pH and degree of deacetylation (DDA) [12], two chi-tosans with differing degrees of deacetylation were implemented into cellulose material in this study, while characterisation was performed for the purpose of determining durability after one washing cycle. 2. Material and methods 2.1 Material Peroxide bleached 100% cotton woven fabric (article: "Fedora") from Tekstilna tvornica Trgovišce, Croatia, of mass per unit area 150 gm-2, yarn density and fineness: warp 55 cm-1, 16 tex; weft 32 cm-1, 20 tex was used. Chitosans of different molecular weight (Mn) and degrees of deacetylation (DDA) were purchased from Mathani Chitosan Pvt. Ltd. The chitosans were milled in a Planetary Micro Mill PULVERISETTE 7 premium line. Ceramic balls with a diameter of 5 mm were used at a milling time of 30 minutes at 900 rpm. After milling, a chitosan powder suspension in water was formed, and a fraction with a diameter greater than 1 |im after 5 minutes was sedimented. A chitosan fraction of less than 1 |im was obtained by evaporating the slurry. Nanoadditives were characterised in terms of their size distribution profiles by means of dynamic light scattering (DLS) using a Zetasizer apparatus from Malvern Instruments. The DLS results indicated that the average particle diameter obtained was within the range of 1 to 0.5 ,«m. The characteristics of chitosans are given in Table 1. Sodium hydroxide p.a. (NaOH) was purchased from Grammol d.o.o., 99.7% acetic acid from VWR International Ltd. and Subitol MLF from CHT-Bezema. Table 1: Characteristics of chitosan Chitosan DDA Mn [kDa] Average particle diameter [am] C-P2 80 60 1-0.5 C-TRI 90 80 1-0.5 2.2 Procedure Chitosan was implemented into cotton fabric by using a mercerisation process [16]. Mercerisation was performed following the technological process (with 0% tension) in a bath containing 24% NaOH, 5 gl-1 anionic surfactant Subitol MLF (Bezema) as a wetting agent in a liquor ratio of 1:20, for 2 minutes at 17 °C. Before hot rinsing, the alkali cotton fabrics were treated with 5 gl-1 of chitosan in a water bath (pH 13), with the same liquor ratio of 1:20, for 2 minutes at 17 °C. The fabrics were then rinsed with hot water (T = 98 °C) for 40 seconds, followed by cold water, neutralised with 0.1 M acetic acid and rinsed until pH 7, and finally air-dried. In order to determine treatment durability, fabrics were washed at 60 °C according to ISO Standard 6330:2012 with a phosphate-based standard ECE detergent without fluorescent whitening agents. The labels and treatments are listed in Table 2. Table 2: Labels and treatments Label Treatment B Peroxide bleached 100% cotton woven fabric P2 Chitosan C-P2 implemented in cotton fabric TRI Chitosan C-TRI implemented in cotton fabric -WC Washed for 1 washing cycle 2.3 Methods The samples were analysed using a FTIR-ATR spectrometer (PerkinElmer, software Spectrum 100). Four scans at a resolution of 4 cm-1 were recorded for each sample between 4000 and 380 cm-1. Electrokinetic potential versus pH was measured through the streaming potential method using a Brookhaven-Paar electrokinetic analyser (EKA) with a stamp cell, and calculated according to the Helmholtz-Smoluchowsky equation [17]. The zeta potential and isoelectric point (IEP) of the textile fabrics were determined and analysed. Scanning electron microscopy was done on cotton fabrics before and after one washing cycle using a MIRA\FE-SEM, Tescan, Czech Republic. The specimens were sputter-coated with a palladium-gold alloy and analysed using a SEM operating at an accelerating voltage of 5.00 kV and magnification of 2000 x. Thermogravimetric (TG) analysis were carried out in atmospheric conditions using a Pyris 1 TGA thermogravimetric analyser from Perkin Elmer. All samples of 5 to 6 mg were heated in a temperature range Tekstilec, 2017,60(4), 296-301 298 Implementation of Chitosan into Cotton Fabric from 50 to 800 °C at a heating rate of 10 °C min-1 with continuous air flow at a rate of 30 ml min-1. 3 Results and discussion The results of FTIR analysis for chitosan (C-P2 and C-TRI), cotton fabric (B) and fabrics with implemented chitosan (P2 and TRI) are shown in Figures 1 and 2. 1641 and 1646 cm-1, respectively. The chitosan characteristic band at 1563 cm-1, which is assigned to the stretching vibration of amino group of chitosan, N-H deformation (amide II), shifted for both chi-tosans applied C-TRI (1575 cm-1) and C-P2 (1585 cm-1) [14]. It is evident that the shape of bands between 1500-1750 cm-1 changed. The band at 2300 cm-1 can be attributed to NC=O group characteristic for the chitin, suggesting that the C-TRI chitosan sample is more acetylated than the C-P2 sample. For chitosan-treated fabrics, the intensity of peaks is lower than in cotton cellulose. The reason may lie in the possible overlapping of cellulose with chitosan. An increased intensity at bands 994 and 992 cm-1 for P2 and TRI chitosan implemented fabrics was observed. This can be attributed to the possible positive interference of peaks of both cellulose and chitosan. No other changes relative to the cellulose were noted. Electrokinetic analysis was thus performed. The results are shown in Figures 3 and 4, and in Table 3. Figure 1: FTIR analysis of chitosan (C-P2), bleached cotton fabric (B), and chitosan C-P2 implemented fabric (P2) Figure 3: Electrokinetic potential (Z) vs. pH of 0.001 M KCl of bleached cotton fabric (B) and chitosan P2 and TRI implemented fabrics Table 3: Zeta potential (Z) at pH 10, pH 7 and isoelectric point (IEP) of modified cotton fabrics before and after one washing cycle Figure 2: FTIR analysis of chitosan (C-TRI), bleached cotton fabric (B), and chitosan C-TRI implemented fabric (TRI) Basic transmission bands for chitosan and cellulose can be seen from the results shown in Figures 1 and 2. A peak at 1640 cm-1 corresponds to the C=O stretching of the secondary amide band (amide I). For both chitosans (C-P2 and C-TRI), that figure is Sample Z at pH 10 [mV] z at pH 7 [mV] IEP [pH] B -27.7 -26.4 2.2 B-WC -19.0 -19.0 2.3 P2 -26.4 -24.6 2.5 P2-WC -20.5 -20.1 2.5 TRI -26.9 -26.2 3.0 TRI-WC -20.4 -19.0 3.0 Tekstilec, 2017,60(4), 296-30 i 299 Implementation of Chitosan into Cotton Fabric Figure 4: Electrokinetic potential (Z) vs. pH of 0.001 M KCl of bleached cotton fabric (B) and chitosan P2 and TRI implemented fabrics after one washing cycle The results of the electrokinetic analysis indicate that both implementations went well. The results of zeta potential in alkali and neutral electrolyte solutions show slightly higher potential as a consequence of the chitosan amino group, from -27.7 mV for B to -26.4 mV for P2, and -26.9 mV for TRI in an alkali medium (pH 10), as well as in a neutral medium at pH 7, from -26.4 mV for B to -24.6 mV for P2, and -26.2 mV for TRI, respectively. The isoelectric point (IEP) confirms that finding. It changes significantly from 2.2 for B to 2.5 for P2 and 3.0 for TRI chitosan-treated fabrics. Even the P2 has a higher zeta potential in a neutral medium, while the IEP indicates the higher implementation of C-TRI chitosan. This can be explained by the DDA, which represents the number of amine or acetyl amine groups on the glycoside unit of chitosan. Since the DDA of TRI is 90, a higher zeta potential and IEP were expected. The results of electrokinetic potential after one washing cycle indicate that all fabrics have a higher zeta potential in alkali and neutral mediums, of about -20 mV. The reason for this lies in fabric shrinkage during the washing process. The zeta potential curves show similar behaviour as before washing, the difference being the plateau at higher values. It should be noted that the IEP is almost the same, suggesting the same presence of the chitosan in the fabrics after one washing cycle. For the characterisation of the fibre surface, scanning electron microscopy was performed on cotton 5-d 5-e 5-f Figure 5: SEM micrographs of cotton fibres with a magnification of2000x in (a) bleached cotton fabric (B), (d) bleached cotton fabric after one washing cycle (B-WC), (b) fabric with implemented chitosan C-P2 (P2), (e) fabric with implemented chitosan C-P2 after one washing cycle (P2-WC), (c) fabric with implemented chitosan C-TRI (TRI), (f) fabric with implemented chitosan TRI after one washing cycle (TRI-WC) Tekstilec, 2017,60(4), 296-30 i 300 Implementation of Chitosan into Cotton Fabric fabrics before and after one washing cycle. The SEM micrographs in Figure 5 show the surface of bleached cotton fabric (Figure 5a) and just cleaned after one washing cycle (Figure 5d). No fibrillation, which usually occurs when the washing process is repeated due to mechanics, was noticed. For the fabric with implemented chitosan, a higher amount of chitosan C-TRI (Figure 5c) can be found on the fibre surface than C-P2 (Figure 5b). After one washing cycle, some fibrillation as noted for both fabrics with implemented chitosan, as well as movement of chitosan particles to the surface. This observation suggests that some particles will be washed when the washing process is repeated. The structural properties of the chitosan-treated cotton fabrics were studied using TG analysis. The results of TG analysis in a range from 50 °C to 800 °C with changes of 10° min-1 are shown in Figures 6 and 7, and in Table 4. Figure 6: TG curves of bleached cotton fabric (B), and chitosan C-P2 implemented fabric (P2) and after one washing cycle (P2-WC) Figure: 7 TG curves of bleached cotton fabric (B), and chitosan C-TRI implemented fabric (TRI) and after one washing cycle (TRI-WC) Table 4: Weight at 500 °C; temperature of complete degradation (Td) and total residue of modified cotton fabrics before and after one washing cycle Sample Weight at 500 °C [%] Td [°C] Residue [%] B 14.954 582.14 0.144 P2 19.766 585.43 0.149 P2-WC 14.564 587.67 0.433 TRI 20.806 602.41 0.520 TRI-WC 15.215 594.83 0.650 It is evident from TG analysis that the chitosan is implemented into the fabric. The weight at 500 °C is significantly higher for fabric treated with chitosan. The amount for cotton fabric (B) is 14.9%, while the amount for chitosan implemented fabrics is 19.8% for P2 and 20.8% for TRI. The amount is slightly lower after one washing cycle, but still present. Taking into account the temperature of complete degradation, it is evident that chitosan-treated fabrics have better thermal stability, which is 20 °C for chi-tosan C-TRI, while Td increased from 582 to 602 °C. In terms of total residue, it is evident that a higher amount is achieved through the implementation of C-TRI chitosan. It should be noted that the washing process led to an increase in residue. One possible reason for this may be the phosphate from the standard ECE detergent, which is well known for its flame retardant properties. 4 Conclusion FTIR-ATR showed characteristic peaks for chitosan and cellulose, but not of implementation. Performed electrokinetic and thermogravimetric analyses, as well as FE-SEM microscopy confirmed that both chi-tosans were well-implemented into cellulosic fabric. Fabric treated with higher DDA chitosan (TRI) has more positively charged amino groups and better thermal stability. Fabric shrinkage occurred during the washing process, resulting in a higher zeta potential. However, the IEP remains the same, suggesting that achieved implementation is stable after one washing cycle. Because the obtained results have shown that chi-tosan with higher DDA gives slightly better properties, its implementation into cellulose will be the subject of the further research. Acknowledgement This research was supported by the University of Zagreb "Functionalisation and characterisation of textile materials for achieving protective properties" (TP3-16) and the Croatian Science Foundation under project no. 9967 "Advanced textile materials by targeted surface modification". The manuscript was partially financed from funds allocated for statuary activity no. 14-148-1-2137 by Lodz University of Technology, Department of Material and Commodity Sciences and Textile Metrology, Poland. Tekstilec, 2017,60(4), 296-30 i 301 Implementation of Chitosan into Cotton Fabric References 1. 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