The effect of domestic laundry detergents on the light fastness of certain reactive dyes on 100% cotton

Abstract

This study presents findings on the effect of several domestic laundry detergents on the fastness to light of selected fiber reactive dyes applied to cotton. Cotton fabric dyed with commonly used reactive dyes were laundered with water only, several domestic detergents, and a laboratory-formulated neutral detergent, and then exposed to light for 2 h in the wet state. Exposures were repeated 15 times, equivalent to 30 h of exposure. Color loss and color difference were measured after 5, 10, and 15 wash cycles, and 10 h, 20 h, and 30 h of exposure. When the fabric was exposed to light wet, the color faded more rapidly than when it was exposed dry. The presence of an oxidizing bleach (sodium perborate or sodium percarbonate) in the detergent increased color loss during washing and wet exposure to light. Ultraviolet radiation from the light source, heat, moisture, alkali, and oxidizing bleach during exposure resulted in hydrolysis of the dye–fiber bond, causing dye desorption during washing and rinsing. The combination of ultraviolet radiation and oxidizing bleaches altered the chemistry of the dye and hence its shade. This was particularly evident on the black dye and one of the navy blue dyes.