Polyvinyl alcohol as an aftertreatment: Part 3 direct dyes on cotton

An aftertreatment with polyvinyl alcohol was found to improve the fastness of three direct dyes on cotton to washing at 60 °C. The effectiveness of the aftertreatment was enhanced by the sequential application of an organic titanate, MgSO4 and three different protease enzymes. This was attributed to the formation of a large molecular size, low water-solubility complex situated at the surface of the dyed substrate which physically resists diffusion of dye from the dyed fabric during washing. Each of the six, polyvinyl alcohol-based aftertreatments reduced the colour strength and also brought about changes in the colour of the dyeings which were similar in magnitude and hue for each aftertreatment, with the exception of that involving PVOH alone, which imparted very little change to the colour of the black dyeing.