FINISHING PEER REVIEWED Antibacterial Finishing of Knitted Cotton Fabric Using Chitosan-citrate Arijit Chakraborty1*, Rosalind Chakraborty2, Subrata Minj1, Biplab Paul1 & Krishna Gopal Mondal1 1Department of Textile Technology, Govt. College of Engineering and Textile Technology 2 Department of Biotechnology, Techno India University Abstract The study focused on the development of bio-functional knitted cotton fabric using chitosan citrate. Chitosan citrate was synthesized, characterized and used for imparting antibacterial prop- erty onto the knitted cotton fabric by pad-dry-cure technique at different concentrations (0.2- 1.6%) with 70% wet pick up during padding. The antibacterial activity and the performance properties of the treated fabrics including bursting strength, wrinkle recovery, whiteness index, bending length and air permeability were evaluated. The finished fabric showed adequate wrinkle resistance, sufficient whiteness, tolerable decrease in tensile strength and more reduction rate of bacteria as compared to untreated fabric without hampering the comfort properties with respect to air permeability and bending length. Keywords Antibacterial finishing, Chitosan-citrate, Knitted cotton fabric 1. Introduction A number of chemicals have been employed to impart The recent developments in knitting technology and antibacterial activity to textile goods. These chemicals processing of knitted fabrics have extended their scope include inorganic salts, organometallics, iodophors for a large spectrum of end use, from usual apparel (substances that slowly release iodine), phenols and fabrics and hosiery to functional products. The con- thiophenols, onium salts, antibiotics, heterocyclics with sumers demand for knitted cotton fabric has increased related compounds, formaldehyde derivatives and and diversified concerning certain functional proper- amines [5]. Majority of such products are synthetic ties and high performance in addition to usual proper- based and may not be environment friendly. The com- ties such as comfort, handle, easy care, aesthetic ap- pliance to the regulations imposed by international peal etc. [1]. But, natural fibres like cotton provide an bodies, such as EPU is essential. The textile industry excellent room for the growth of micro-organisms continues to look for eco-friendly processes that sub- which causes unwanted effect not only to the cotton stitute for toxic textile chemicals [6]. Recently, natural textiles itself but also to the wearer [2]. These effects materials like chitosan, natural dyes, herbal products include the generation of unpleasant odour, stains and such as aloe vera, tea tree oil, eucalyptus oil, tulsi and discolouration of coloured fabric, a reduction in fabric neem leaf extracts are attracting the attention of re- mechanical strength and an increased likelihood of searchers because of their availability of resources, contamination. For these reasons, it is highly desirable low cost, easy handling and minimum damage to the that the growth of microbes on the cotton textiles should environment. In addition, they have unique properties be prohibited or minimized during their use or storage such as non-toxicity and biological degradability [7]. [3-4]. So, it is important to develop antibacterial cot- Nowadays, chitosan, a natural linear bio- ton fabric where aesthetic and hygiene is important polyaminosaccharide has opened up a new avenue in and safety is necessary. this area of research and has also been studied as a new antibacterial agent for textiles [8]. Protonated *All the correspondence should be addressed to, Association TEXTILE Dr. Arijit Chakraborty amino groups of glucosamine units in chitosan may Department of Textile Technology, inhibit growth of micro-organisms by holding nega- Govt. College of Engineering and Textile Technology, tively charged cell walls [9]. However, the major prob- Serampore-712201, India lems of chitosan as an antibacterial agent are its loss E-mail: [email protected] of antibacterial activity under alkaline conditions due Journal of the September - October 2015 149 FINISHING to its loss of the cationic nature and its poor durability on textile fabrics due to its lack of bonding force with fabric [10]. Though plenty of research work has already been done using chitosan and herbal products but the work on knitted cotton fabric is found to be very scanty and sporadic. Therefore, to overcome the problem, it has been thought worthwhile to synthesize and character- ize chitosan citrate as the chitosan derivative has the possibility of forming covalent bonds with cellulose and also to evaluate its potentiality towards antibacte- rial and crease resistant finishing of knitted cotton Figure 2.1: Synthesis of chitosan citrate fabric. 2.2.3 Characterization 2. Materials and Methods Characterization of pure chitosan powder, trisodium 2.1 Materials citrate dihydrate, chitosan citrate, knitted cotton fabric Chitosan having 75% degree of acetylation was ob- and knitted cotton fabric treated with chitosan and tained from HiMedia Laboratories Pvt. Ltd., Mumbai, chitosan citrate were carried out by Perkin Elmer FT- India. Mill scoured and bleached single jersey knitted IR 6X keeping air as reference. In this analysis, reso- cotton fabric (15.74 wales/cm, 20.47 courses/cm, lution of 4 cm-1 was chosen and data collection was in 322.36 stitches/cm2 and 166.88 g/m2), supplied by the range of 4000-400 cm-1. 1H NMR spectrum of Four Star international, Sodepur, Kolkata (North), In- chitosan and chitosan citrate was recorded on Bruker dia was used after purification by scouring for 2 h boil AV 400 (Switzerland). 13C NMR experiments were using aqueous solution of 1% sodium hydroxide. The carried out at 25.1 MHz on a spectrophotometer using fabric was then thoroughly washed and air dried at cross polarization (CP) and magnetic angle spinning room temperature. All the other chemicals used were (MAS) with high power 1H decoupling and 1s recycle of reagent grade. time. 2.2 Methods 2.2.4 Fabric treatment 2.2.1 Preparation of chitosan solution Fabric samples (10in×3in) were padded in an aqueous About 1g of the procured chitosan was mixed with 1% solution of dissolved chitosan citrate (0.2-1.6%) in two acetic acid (1ml of acetic acid in 99 ml of distilled dipped two nipped to give a wet pick up of 70%. The water) and the mixture was stirred for 24 h. After 24 padded samples were dried at 1000C for 2 min and h, chitosan was found to be dissolved in acetic acid cured at 1700C for 2 min. The cured fabrics were and a clear viscous solution was obtained. washed with hot water followed by cold water and then dried. The same procedure was followed for the 2.2.2 Synthesis of chitosan citrate treatment of the fabrics with chitosan dissolved in 1% 1% chitosan solution was added into a bath containing acetic acid solution. an aqueous solution of 100 ml of tri-sodium citrate (10% w/v), at 4°C for 3-4 h. At the same time pH of 2.3 Testing the solution was maintained in the range of 4.5-6.5 2.3.1 Dry and wet crease recovery angle using hydrochloric acid. The resultant slurry was Test on knitted cotton fabrics for the crease recovery washed with distilled water, put on a glass plate and angle was carried out by the Shirley Crease Recovery kept at room temperature for 48 h in order to dry the Tester as detailed in IS: 4681-1981 (Reaffirmed 2004). material. The chemical reaction involved in this re- A sample of the knitted cotton fabric 15 mm × 40 mm spect is shown in Figure 2.1. was cut from both wales and course directions. Then TEXTILE Association the sample was carefully folded into half, kept be- tween two glass plates and a 1kg weight was placed on the top. After 3 min, the load was removed and the sample was placed on the fabric clamp in the tester Journal of the and allowed to recover from creasing. Finally, the fabric 150 September - October 2015 FINISHING crease recovery angle was read and recorded. The same 2001 test method. An incubated bacterial culture in a procedure was carried out for measuring wet crease nutrient broth was diluted using a sterilized 0.5mM recovery angle for which each sample was immersed phosphate buffer (KH2PO4, pH 6.8) in order to obtain in water for 1 min and then placed between two pieces a final concentration 1.5-3.0 x 105 colony forming units of blotting paper for 2 min to remove excess water (CFU)/ml. This solution was used as a working bacte- [11]. rial dilution. The treated fabric sample (1g) was cut into small squares with 5mm length and transferred to 2.3.2 Bursting strength a 250 ml Erlenmeyer flask containing 50ml of the The bursting strength of the sample was tested using working bacterial dilution. All the flasks were loosely Bursting Strength Tester (UBIQUE Enterprises, Pune, capped, placed in the incubator and shaken for 1 h India) according to ASTM D3786. with 120 rpm speed at 370C using a Wrist Action in- cubator shaker. After a series of dilutions using the 2.3.3 Bending length buffer solutions, 1ml of the diluted solution was plated When a certain length of a fabric bends at a given in nutrient agar. The inoculated plates were incubated angle due to its own weight, it is defined as the fabric at 370C for 24 h. Then the optical density (OD) at bending length. Bending lengths of treated and un- lmax (660 nm) of the solution was measured with the treated samples were determined according to the help of Spectrophotometer. From OD reading, the CFU/ ASTM D1388-96 (Reapproved 2002) protocol using a ml was calculated referring 1OD = 2.04x108 CFU/ml. fixed angle flexometer (Paramount Stiffness Tester, The same treatment was carried out for untreated fab- Coimbatore, India). A fabric sample, 200 mm × 25 ric samples. The percentage reduction of bacteria was mm was first mounted on the horizontal stage under calculated as follows: the weight of the graduated ruler specially designed for this experiment and pushed forward.