Gamma and electron beam irradiation effects on SiR-EPDM blends

Abstract

Ethylene Propylene Diene Monomer (EPDM) is widely used as Cable Insulation Material (CIM) due to its good mechanical strength. Silicone Rubber (SiR) is used in high temperature environments due to its good di-electric properties/hydrophobicity. The blending of SiR-EPDM may result in the improvement in their specific properties. The SiR-EPDM blend of equal composition (50:50) was prepared. When such blends are used as Cable Insulation Materials (CIM), they should perform their safety functions throughout their installed life in Nuclear Power Plants (NPP). The CIM will be exposed to Gamma irradiation at the installed locations. The short time accelerated testing was carried out, in order to forecast long-term performance of CIM. Electron beam irradiation is widely used in cable manufacturing industries to improve the performance of the polymeric materials. In the current study, on the purpose to investigate the effect of gamma/electron beam irradiation on the 50–50 composition of SiR-EPDM blend, blend was exposed to 25 Mrad dose of gamma/electron beam irradiation. The electrical and mechanical parameters like Volume Resistivity (VRY), Surface Resistivity (SRY), Tensile Strength (TS), Elongation at Break (EB), Hardness (H) of the virgin, gamma/electron beam irradiated blends were determined as per ASTM/IEC standards. The nature of degradation was investigated using Fourier Transform Infrared Spectroscopy (FTIR). To determine the elemental composition of the materials at the surface, Energy Dispersive X-ray Analysis (EDAX) has been done. Scanning Electron Microscopy (SEM) analysis has been done to study the morphological changes. The occurrence of cross-linking is found to be the mechanism for ageing in gamma/electron beam irradiated SiR-EPDM blends.