Comparison of effects of gamma and electron radiations on polymer insulators

This work is aimed at comparing the effects of Co-60 gamma ray and electron ray irradiation on polyethylene, polypropylene, silicone rubber, natural rubber, fluororubber, ethylene-vinyl acetate copolymer and isobutylene-isoprene rubber. Gas generation, gel fraction and swell are observed. A tensile test is also carried out. It is found that gamma and electron radiations have nearly the same effects on all polymers except for EVA. In particular, there is no difference between them in the range of 0 - 50 Mrad for PE, 0 - 30 Mrad for PP, IIR, SiR and FR, and 0 - 120 Mrad for NR. However, some differences as follows are actually observed in this study : 1) The amount of hydrogen gas generated by gamma ray irradiation is greater by 10 - 20 percent than that by electron irradiation in all cases investigated, and 2) These two types of irradiation have different effects on the tensile properties, gel fraction and swell of EVA. (Nogami, K.)