Relation between molecular size of non-ionic dyes and their diffusivity in nylon 6 film.

Abstract

Diffusion coefficients (Df) of four p-nitroaniline derivatives and eight non-ionic azo dyes in nylon 6 film from aqueous solution were determined over the temperature range of 40-90°C. The values of Df were evaluated from the concentration-distance curves (profiles) of the dyes in the film, which were measured by the film roll method. For each dye, the activation energy (Ed) of diffusion in the film was assessed from the values of Df determined at various temperatures. The molecular weight (Mw), molar volume at boiling point (Vb) and van der Waals volume (Vw) were used as measures of molecular size of the penetrants. Fairly good correlations between Vw and D_??_ and Vw and Ed were observed. A computer simulation was made to estimate the rate of disperse dyeing of the nylon film at raising dye bath temperature. The decrease in the rate of dyeing with an increase in Vw was revealed.