Cationization of Cotton Fiber by Chitosan and Its Dyeing with Reactive Dye without Salt

Abstract

Conventional dyeing process of cotton fabric with reactive dyes requires the use of large amount of electrolyte as exhausting agent. Thus the discharged wastewater from dye house creates unavoidable environmental threats due to very high salt concentration. This paper presents the possibility of salt free dyeing of cotton fabric with reactive dye by treating the fabric with chitosan. Exhaustion of dye by the fabrics was increased by treating them with chitosan prior to dyeing. It has been noticed that absorption of dye has significantly increased with the increment of chitosan concentration. The K/S value, i.e. dye absorption of chitosan treated fabrics was found as 1.6, 1.7, 2.2 and 2.9 respectively for 1%, 2%, 3% and 4% chitosan concentration whereas the K/S value of untreated fabric was 1.9. Fastness of the dyed samples had also been investigated through color fastness to washing, perspiration and rubbing. No fastness deterioration had been experienced for the dyed fabric treated with chitosan. However in case of chitosan treatment at high concentration, the wet rubbing fastness was found slightly inferior to untreated dyed samples which can be explained as the consequence of higher depth of shade due to high absorption of dyestuff by the fabric.