Major Development in Cotton Coloration: A Review

Abstract

Most cotton fabrics are dyed with reactive dyes because they produce a full range of bright fashion colours with a high degree of wash fastness.Reactive dyes are frequently considered as king of dyes for cotton owing to their simple application techniques. However, reactive dyes are anionic and cotton fibers gain anionic surface charge in water, the charge repulsion adversely affects the dye bath exhaustion. Large quantity of electrolyte is added to overcome this problem. Some problems such as low dye utilization, high degree of salt utilization and colored effluent due to unexhausted, unfixed, and hydrolyzed dyestuffs, and high volume of waste water discharged, always exist in the application of reactive dyes.These electrolytes are neither exhausted nor destroyed and hence remain in the discharge dye liquor which leads to enormous environmental problem. Due to these problems this class of dyes is the most unfavorable one from the ecological point of view, these effluents produced gives high values of BOD/COD and increases salinity of the rivers affects the delicate biochemistry of aquatic life.A number of more environmentally sustainable approaches for reactive dyeing of cotton have been proposed to overcome the polluted effluent problem. This paper reviews options to improve the sustainability of the colouration process through development in dye structure, modification of dyeing machinery and processes, chemical modification of cotton fibre prior to dyeing, and use of organic compounds in place of inorganic chemicals.