A theoretical model for the diffusion-limited thermal oxidation of elastomers at medium temperatures

A theoretical model is presented to describe the diffusion-limited thermal oxidation of stabilized elastomers, with no assumptions concerning the concentration of oxygen, the kinetic chain length, the ratio of termination rate constants, or the existence of a steady state for oxidation products. Model predictions are found to agree qualitatively with reported main features of elastomer thermal oxidation. The model is used to simulate the thermal ageing of thick natural rubber slabs under ambient air at 80-150 degreesC. Among others, the effect of stabilizer concentration and thickness of the aged parts on the evolution of the oxidation process is discussed. Conditions are also identified under which the oxidation process may be considered free of oxygen mass transfer limitations.