Implementation of Chitosan into Cotton Fabric

Chitosan, produced through chitin hydrolysis, has been highly appreciated for medical purposes. For the last decade, its application in textiles and biomaterials has grown signifi cantly. It has been well-implemented in man-made fi bre, but achieved properties in natural fi bres have not proven durable. Thus, in this study, two chitosans with diff ering degrees of deacetylation were implemented into cellulose material using a mercerisation 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 confi rmed that both chitosans are well-implemented into cellulosic fabric. Fabric treated with chitosan with a higher degree of deacetylation has more positively charged amino groups and better thermal stability.


Material
Peroxide bleached 100% cotton woven fabric (article: "Fedora") from Tekstilna tvornica Trgovišće, Croatia, of mass per unit area 150 gm -2 , yarn density and neness: warp 55 cm -1 , 16 tex; we 32 cm -1 , 20 tex was used.Chitosans of di erent molecular weight (M n ) and degrees of deacetylation (DDA) were purchased from Mathani Chitosan Pvt. Ltd. e 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.A er milling, a chitosan powder suspension in water was formed, and a fraction with a diameter greater than 1 µm a er 5 minutes was sedimented.A chitosan fraction of less than 1 µm was obtained by evaporating the slurry.Nanoadditives were characterised in terms of their size distribution pro les by means of dynamic light scattering (DLS) using a Zetasizer apparatus from Malvern Instruments.e DLS results indicated that the average particle diameter obtained was within the range of 1 to 0.5 µm.e 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.

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.e 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 nally 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 uorescent whitening agents.e labels and treatments are listed in Table 2.

Methods
e samples were analysed using a FTIR-ATR spectrometer (PerkinElmer, so ware 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].e zeta potential and isoelectric point (IEP) of the textile fabrics were determined and analysed.Scanning electron microscopy was done on cotton fabrics before and a er one washing cycle using a MIRA\FE-SEM, Tescan, Czech Republic.e specimens were sputter-coated with a palladium-gold alloy and analysed using a SEM operating at an accelerating voltage of 5.00 kV and magni cation of 2000 x. ermogravimetric (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 Implementation of Chitosan into Cotton Fabric from 50 to 800 °C at a heating rate of 10 °C min -1 with continuous air ow at a rate of 30 ml min -1 .

Results and discussion
e 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. 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 gure is 1641 and 1646 cm -1 , respectively.e chitosan characteristic band at 1563 cm -1 , which is assigned to the stretching vibration of amino group of chitosan, N-H deformation (amide II), shi ed for both chitosans 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.e 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.e 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.is 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.e results are shown in Figures 3 and 4, and in Table 3. e results of the electrokinetic analysis indicate that both implementations went well.e 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.e isoelectric point (IEP) con rms that nding.It changes signi cantly 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.is 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.
e results of electrokinetic potential a er one washing cycle indicate that all fabrics have a higher zeta potential in alkali and neutral mediums, of about -20 mV.
e reason for this lies in fabric shrinkage during the washing process.e zeta potential curves show similar behaviour as before washing, the di erence 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 a er one washing cycle.For the characterisation of the bre surface, scanning electron microscopy was performed on cotton fabrics before and a er one washing cycle.e SEM micrographs in Figure 5 show the surface of bleached cotton fabric (Figure 5a) and just cleaned a er one washing cycle (Figure 5d).No brillation, 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 bre surface than C-P2 (Figure 5b).A er one washing cycle, some brillation as noted for both fabrics with implemented chitosan, as well as movement of chitosan particles to the surface.is observation suggests that some particles will be washed when the washing process is repeated.e structural properties of the chitosan-treated cotton fabrics were studied using TG analysis.e 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.It is evident from TG analysis that the chitosan is implemented into the fabric.e weight at 500 °C is signi cantly higher for fabric treated with chitosan.e 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. e amount is slightly lower a er 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 chitosan C-TRI, while T d 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 ame retardant properties.

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 con rmed that both chitosans 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 a er one washing cycle.Because the obtained results have shown that chitosan with higher DDA gives slightly better properties, its implementation into cellulose will be the subject of the further research.

Acknowledgement
is 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 modi cation".e manuscript was partially nanced 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.

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

Figure 5 :
Figure 5: SEM micrographs of cotton bres with a magni cation of 2000x in (a) bleached cotton fabric (B), (d) bleached cotton fabric a er one washing cycle (B-WC), (b) fabric with implemented chitosan C-P2 (P2), (e) fabric with implemented chitosan C-P2 a er one washing cycle (P2-WC), (c) fabric with implemented chitosan C-TRI (TRI), (f) fabric with implemented chitosan TRI a er one washing cycle (TRI-WC)

Table 4 :
Weight at 500 °C; temperature of complete degradation (T d ) and total residue of modi ed cotton fabrics before and a er one washing cycle