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

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.