CONCENTRATION DEPENDENCE OF DIFFUSION COEFFICIENT OF DISPERSE DYE IN POLYVINYLACETATE

Abstract

A sublimative desorption study of model disperse dyes, p-nitroaniline (PNA), p-amino-azobenzene (PAAB) in polyvinylacetate has been carried out with dye content from 0.01 to 0.25 in g-dye/g-polymer. The desorption temperature ranged from 80 to 130°C. The apparent diffusion coefficients of these dyes increased linearly with an increase in dye concentration; diffusion of PNA showed much stronger concentration dependence than that of PAAB. These features of dye diffusivity could be explained quantitatively in terms of Fujita's free volume theory of diffusion. On the other hand, increasing dye concentration had an effect on lowering the glass transition temperature (T_g) of the colored polymer. Both depression of T_g and increase in dye diffusivity with dye concentration were considered as resulting from the same functional increase in fractional free volume in polymer-dye mixture with increasing dye content.