Chitin and Chitosan- Eco Friendly Textile Finishes
Chitin is a polysaccharide found in the outer skeleton of arthropods including insects, crabs, shrimps, and lobsters. It is the second most plentiful, naturally occurring polymer, after cellulose. Chitosan, derived from Chitin, is prepared by partial deacetylation of chitin. For commercial uses Chitin and Chitosan are primarily sourced from shrimp and crabs industry. Although, they are waste products for these industries, yet they are widely used in other industries ranging from health and beauty aids to water purification, biomedical applications, agriculture, biotechnology, nutrition, and treatments in the finishing process of textile fibers.
Application of Chitin and Chitosan in Textile Industry
Textile chemicals are an inseparable part of textile industry. They are widely used in pretreatment and finishing processes of textiles. Of late, Textile industry has been repeatedly accused for polluting environment. Many textile chemical companies
are on a lookout for environmental friendly alternatives either willfully or due to legal restrictions in some countries. Chitosan is biodegradable and is distributed into the environment in
a dispersed manner. Thus when it is used in textile dyeing
process, it represents an environmentally sound practice.
Chitin in Pretreatment of Fabrics
Desizing agents, detergents, peroxide agents, scouring agents etc. all are used in preparation process of fabrics for dyeing but they are all textile pretreatment chemicals
. Apart from chemicals, other environmental friendly substances like cellulose enzymes and chitosan are also used, although rarely, for pretreatment of fabrics. The chitosan pretreatment is used on yarns before the yarn is woven into fabric. It is done in a keir, which is a large metal cylinder used to dye yarns.
Chitosan is also used in pretreatment of fabrics having neps on them. Neps are the small knots or fiber entanglements on the surface of fabrics. Neps appear as white specs on the surface of dyed fabric, especially cotton and wool, and are caused by immature fibers which become entangled. The fiber having neps is pretreated with a mixture of chitosan, a non-ionic
wetting agent, and sodium sulfate. This combination is also referred to as chitosan pretreatment. This process doesn't require any additional machinery and has many benefits. It increases the dyeing ability of direct and reactive dyes. Chitosan treatments, used in combination with direct dyes, increase the color strength more than reactive dyes. It also eliminates differences in color between dyed immature and mature fibers. Thus, it helps in enhancing the quality of fabric and the entire process is environmental friendly too.
However, there are certain problems too while using chitosan for pretreating fibers. It reduces the wash-fastness and color-fastness properties of the fabric but this problem can be eliminated by after treatment of the fabric with fiber- reactive quaternary ammonium compounds.
Chitin in After treatment of Fabrics
Chitosan can also be used as aftertreatments for coverage of neps in fabrics. However, The chitosan aftertreatment is used on fabrics which have already been dyed and rejected due to the presence of neps, with the aim of reducing treatment cost. The fabric having neps is treated with a mixture of chitosan, a non-ionic wetting agent, and sodium sulfate also referred to as chitosan aftertreatment. Chitosan in after treatment is used in greater amount than it is used in pretreatment so that it may overcome the dye already present in the fabric. This process also gives all the benefits which results from pretreatment with chitosan. One of the major benefits is, decreased fabric rejection. The fabric that had previously been rejected due to the presence of neps can now be sold to the original fabric wholesale buyer, who had purchased the remaining fabric of the lot, at the premium price.
As the finishing process of fabrics done with chitin and chitosan are not very popular, the textile manufacturers and processors are hesitant to apply this practice. These manufacturers must be made aware of the potential economic benefits and costs of these treatments done with the help of chitin and chitosan. This environmental friendly substance for treating fabrics is waiting for its market and may prove far more beneficial in the long run.