Studies on dyeing properties of chitosan modified cellulosic fiber

Abstract

This paper presents the possibility of salt free dyeing of cotton fabric with reactive dye by treating the cotton with chitosan from fish scale and used as a salt for dyeing of cotton with reactive dye. Cellulosic fiber acquires negative charge in aqueous medium and thus repels negatively charged dye anion during dyeing. Such repulsion between fibre and dye is offset by using large quantity of salt in dye bath, particularly for reactive dyes. A low dye bath exhaustion also leads to low dye fixation of reactive dyes on cotton. Therefore the discharged wastewater from dye house creates avoidable environmental threats due to very high dye concentration. Hence, surface modification of cotton to increase dye-fibre interaction is thus the best route to overcome the lack of affinity of cotton to reactive dyes making salt-free reactive dyeing. In this investigation an attempt was made to modify cotton with chitosan extracted from fish scales. The chitosan modified cotton was dyed with reactive dye and compared with the conventional dyed cotton. The color strength of the modified cotton fabric was better than that of conventional sample which is 18.88 and 18.02 respectively. Better fastness properties were experienced in treated cotton sample than the ordinary sample. The fastness properties obtained were better than the conventional sample. From this investigation it was revealed that surface modification of cotton by treatment with chitosan provided better dyeing properties and it can be the best possibility for salt free dyeing of cotton.