Comparison of the effects of heat and gamma irradiation on the degradation of cross‐linked polyethylene

Abstract

For conducting comparative research, samples of cross‐linked polyethylene (XLPE), made exactly in the same manner as those used in nuclear power plants, were aged in two ways: purely thermally, and concurrently with heat and γ‐irradiation, for long periods up to 2000 h. They were then examined by an indenter, mid‐infrared absorption spectroscopy, broadband dielectric spectroscopy, and measuring the electrical conductivity. As a result, it became clear that the effect of radiation is more dominant than that of heat on the oxidation or carbonyl formation in XLPE. However, heat is a more determining factor on the surface hardness of XLPE. In addition, the complex permittivity of XLPE increases as a result of the appearance of abundant carbonyl groups. Both the carbonyl index and indenter modulus can be indicators of aging. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.