Modeling of Oxidation Process and Property Changes Induced in Ethylene-Propylene-Diene Copolymer by Gamma Irradiation

摘要

The oxidation process induced in ethylene-propylene-diene (EPDM) copolymer by gamma irradiation at high temperature was simulated by solving equations on chemical reactions and gas diffusion rates. As a result, distributions of oxidative products and gases and changes in material properties were clarified. All the oxidative products such as ketones, alcohols, and carboxylic acids as well as chain scissions in EPDM increase with irradiation and show concave spatial distributions. Crosslinks between molecular chains also increase with irradiation but show convex spatial distributions. Moreover, the simulation results demonstrate that the irradiated materials become harder and the resultant increase in hardness is more significant near the surface. These results on the changes in material properties are important factors in many aspects such as the design of a proper preventive condition monitoring method of EPDM being used under gamma irradiation.