The effect of reactive dyes on damage in wool dyeing

This paper demonstrates that reactive dyes exert a significant fibre–protective effect when dyeing wool fabric; this effect may be measured, in a reproducible manner, using the wet–burst strength test. The effect of dyebath pH, dye concentration, dyebath temperature and dyeing time on wool can thus be evaluated. The magnitude of the above protective effect has been compared with that achieved using commercially available fibre–protective agents. It is concluded that reactive dyes are significantly more effective than the latter agents when employed in medium to full depths. It is proposed that the unusual protective effect afforded by reactive dyes is related to the following factors. Reactive dyes readily react with sulphur nucleophiles, thus inhibiting thiol–disulphide interchange reactions and thereby significantly interfering with the level of set produced in a boiling dyebath. Reactive dyes react preferentially with non–keratinous proteins in the intercellular cement and the endocuticle thus reducing their tendency to hydrolyse and to partially dissolve in the hot aqueous dyebath.