Model for heterogeneous aging of rubber products

Rubbers and elastomers will change their material properties due to environmental influences such as temperature, oxygen, radiation and similar conditions. The reason for this material change is the modification of the polymer network. In the case of sulphur cured natural rubber it can result in hardening of the material and pronounced surface hardening for thick walled products. This is known as the diffusion limited oxidation effect when oxidation is the key environmental influence. This paper describes a model which is designed to calculate the change in network density caused by thermo-oxidative aging and the required measurements for the parameterisation. The model is validated by simulating the intermediate stress relaxation experiments and showed good correlation with the experimental data.