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The Location of Acid and Disperse Dyes in Polyamides

Brody, H.
Textile research journal 1965 v.35 no.10 pp. 895-902
cellulose acetate, dyeing, dyes, fabrics, hydrolysis, nylon, polyamides, solubility, sorption isotherms, textile fibers
Assuming that nylon 66 fiber has structural elements similar to those of an imperfect crystal, it is proposed that dyeing by acid and disperse dyes occurs by filling vacancies caused primarily by chain folding. The hydrolysis during dyeing with acid dyes is assumed to take place at these folds. This leads to the concept of a maximum dye capacity determined by packing requirements for a fixed "free volume" within the fiber. In the case of acid dyes. it is proposed that additional dye can be accommodated by further hydrolysis of chains bordering the vacancies. Disperse dyes appear to have Langmuir-type adsorption isotherms on nylon 66, presumably due to the filling of the proposed sites. It is suggested that the dyeing of cellulose acetate by disperse dyes is also site-determined, with the usual linear isotherm being a Langmuir isotherm of limited extent. This partial filling of the sites would arise from a limiting dye solubility in the dyebath.