Diffusion of ester plasticizers in polybutadiene

Abstract The diffusion of plasticizers in polybutadiene is studied over a wide temperature and concentration range. Certain systems manifest a “negative” relation between the concentration and the relative coefficient of diffusion. On the basis of the correlation between the ratio of the limiting diffusion coefficients in the limiting composition regions it is suggested that this effect is characteristic of penetrants of MM exceeding the mass of the kinetic segment. With all the systems studied an inflexion point is observed at 130–140°C on the plot of temperature against the coefficients of diffusion. The contributions to the energy expended in the formation of microcavities and friction of the diffusant on translation are calculated within the framework of the proposed model. The size of the hole necessary for diffusion, which is only a little larger than the most bulky penetrant group, is determined.