Diffusion of Curatives. I

Abstract

Abstract Curatives will readily migrate across a rubber-to-rubber interface following the classical laws of diffusion. The rate of diffusion increases with increasing temperature. The absolute change in curative concentration diminishes with increasing distance from the interface and increases with time. A test procedure using conventional analytical methods can be used to accurately determine the diffusion coefficients of curatives at various storage temperatures in standard rubber formulations. Diffusion profiles and coefficients are dependent on the curative type. There appears to be a general correlation with molecular weight, with the rate of diffusion decreasing with increasing molecular weight. There is a small, rationalizable effect of concentration on the diffusion coefficient. The diffusion of curatives can cause a significant change in the cure system at or near the interface of a plied rubber article. Diffusion profiles for a particular rubber formulation can be predicted from experimental data using relatively simple analytical and mathematical techniques.