Light fading, rub and wash fastness of sulphur-dyed cotton fabrics aftertreated with cation–tannin protective system

Abstract

Purpose Sulphur dyes are the most highly consumed colourants for cellulosic substrates owing to their reasonable cost and acceptable fastness. However, the use of noxious conventional reducing agent, sodium sulphide and impaired wash fastness against oxidative bleaching is gradually decreasing the market of these dyes. As the need for “Green” goods and services is raising public awareness, this paper aims to use a glucose-based biodegradable reducing agent in place of sodium sulphide to dye cotton fabrics with a range of commercial sulphur dyes. The study also proposes an aftertreatment method to improve the fastness properties of the dyeing. Design/methodology/approach The paper investigated the impact of a newly developed aftertreatment method on the fastness properties of dyeing. This involved the sequential application of a cationic fixing agent (Tinofix ECO) and tannin (Bayprotect CL) on the coloured fabrics and subsequent evaluation of colour strength, washing, light and rubbing fastness. Findings The effect of aftertreating the dyed cotton was found to significantly improve the light and wet rub fastness. The surface morphology of the dyeing remained unaffected as depicted by the absence of any finish residues. Research limitations/implications The protective effect of the cation–tannin aftertreatments was examined with a view to providing the necessary commercial performance; however, it was established that the dry rub fastness was either reduced or remained unaffected and the wash fastness to International Organization for Standardization 105 C09 was also marginal. Originality/value This finishing technique is novel and can be found useful for manufacturing sulphur-dyed products with the improved light and wet rub fastness.