The light stability of azo dyes and azo dyeings II. Perspiration–Light stability of dyeings with reactive and non-Reactive derivatives, respectively, of two selected azochromophores

Abstract

The perspiration–light stability of RC-dyed (conventional reactive dyeing) and N-dyed (substantive dyed without subsequent rinsing) cotton fabric dyeings produced with the members of ‘A’-dye and ‘B’-dye groups, respectively, have been studied. Three main factors influence the perspiration-light stability of the studied dyeings: the nature of the dye–fibre bond, the light stability of the released hydrolysed dye molecules and the action of the salts in perspiration on the latter. The preferred MCT-covalent bonds in the ‘A’-group dyeings lead to higher proportion of released dye molecules in acidic perspiration under exposure, than the preferred, and to a lesser extent to acid sensitive VS-type bonds in the ‘B’-group dyeings. Covalently fixed dyes in dyeings result in much better perspiration-light stability than dyeings with released hydrolysed dye molecules, and the difference in light stability between hydrolysed dye molecules of the two dye groups, as well as their different salt sensitivity, result in improved perspiration–light stability compared to light stability in the ‘B’-group dyeings, and lower perspiration–light stability compared to the light stability in the ‘A’- group dyeings.