Thermo-oxidative degradation and stabilization of rubber materials

Thermo-oxidative degradation of rubber materials often determines the life-time of rubber products. An understanding of fundamental aspects of oxidative ageing is therefore of great importance. This review discusses the ageing of thick-walled rubber materials according to results from tests of oxidative durability of NR and EPDM using novel analytical techniques, e.g. ATR-FTIR (reflection infrared spectroscopy), CL (chemiluminescence), CT (computed X-ray tomography scanning), MP (modulus profiling) and measurements of electrical conductivity. Ageing is shown to be concentrated in the surface region according to diffusion-limited oxidation expectations. The results suggest an attempt to stabilize rubber materials using surface modification techniques as an alternative to stabilization by using antioxidants. Suitable surface modification techniques, e.g. plasma polymerization and photografting, are presented with an appropriate choice of monomers. It is shown that acrylic acid is a monomer with great a potential for creating surface layers with a low permeation rate for oxygen.