Positron irradiation effects on polypropylene

Positron irradiation effects on polypropylene (PP) and polyethylene during the positron lifetime measurements have been studied in detail. The effect, which was to decrease I 3 , has been found to be larger in air than in vacuum. For PP, when the lifetime measurements were performed at temperatures above 348K, the radiation effect was scarcely observable. However at low temperature the radiation effect was accumulated and I 3 was decreased during the measurements. Irradiation of Co-60 γ-ray up to the dose of 300 MRad also lead to similar decrease in I 3 , but the decrease due to γ-irradiation was not as large as that due to the positron irradiation. Irradiation effect of positrons appears to be different from that of γ-rays