Studies on radiation-induced current in polymeric insulating materials and their fine structure

Abstract

Radiation-induced current (conductivity) (RIC) has been investigated in polymeric materials degraded under combined conditions of heat and radiation. Crystalline materials such as polyethylene, and non-crystalline materials such as ethylene—propylene rubber used for the insulation of wire and cable have been studied. Fine structure changes have been investigated by studying X-ray crystallinity, melting behaviour, the glass transition temperature, and tensile properties. RIC and its decay are affected more by the degree of crystallinity than its perfection. In crystalline samples irradiation after heating causes less degradation than heating after irradiation. Numbers of short-lived carriers increase with a decrease in the degree of crystallinity, indicating the trapping of short-lived carriers in the non-crystalline region and long-lived carriers in the crystalline region.