Colouration of cotton by combining natural colourants and bio-polysaccharide

A sustainable alternative to some synthetic dyes and dyeing auxiliaries could be substitution by their corresponding natural counterparts. This is in response to a growing premium market for goods with the natural tag brought about by the increasing consumer awareness about conserving and preserving the environment. Currently, natural dyes are used only by hobbyists and craftsmen in a small scale of operation. The present market trend prompts investigations into all aspects of large-scale application of natural dyes. This may encompass the social, economic and technical aspects. A critical technical consideration is the means of increasing colour yield during dyeing. In achieving this, the use of by-products or consequent acquisition of functionality will be an added benefit. In this study, chitosan, a bio-polysaccharide derived from the exoskeleton of crustaceans, has been investigated for enhancing dye uptake while imparting antimicrobial attribute to cotton fabric. Pad-dyeing of natural dyes, from the Acacia family, in the presence of a controlled amount of chitosan resulted in darker shades by approximately 20% as compared to without chitosan. Key performance parameters such as fastness of dyed fabric to washing, rubbing and light were evaluated and found to be satisfactory. In addition, chitosan imparted excellent antibacterial properties to the cotton fabric.