Chemical additives migration in rubber

Migration of compounding ingredients is an important factor in the overall properties and performance of rubber articles containing a number of layers for example, a tire, a hose or a conveyor belt. In certain cases, migration of compounding ingredients before, during and after vulcanization in rubber compounds can be of benefit. For example, waxes and p-phenylenediamines antiozonants rely heavily on the migration mechanism to provide optimum protection of rubber products during service against degradation by ozone. In addition, the dispersion of compounding ingredients such as oil, curatives, and antidegradants can be enhanced by diffusion within rubber. In other cases, however, diffusion across a rubber-to-rubber interface can be detrimental to performance. Diffusion will change the distribution of materials which in turn may result in changes in mechanical properties, loss in adhesion or antidegradant protection, and staining of light-colored products. Thus, a better understanding of the migration of chemical additives in rubber could provide the desired distribution of ingredients for obtaining the optimum compound performance.