γ-Initiated Oxidation of Isotactic Polypropylene: Effect of γ-Dose Rate on Durability

Abstract

The effect of γ-irradiation dose rate on the chemical, molecular, and mechanical properties of isotactic polypropylene (iPP) films was investigated using three different 60Co sources with dose rates of 600, 660, and 780 Gy h−1. Fourier transform infrared spectroscopy coupled with chemical derivatization with NO and SF4, and measurements of the elongation at break, toughness, and molecular weight were used to describe the effects of γ-dose rate on iPP. It was found that the formation of oxidation products depended significantly on the dose rate. However, the kinetic accumulation of ketones were more sensitive to the dose rate of gamma source. Degradation induced by γ-radiation depends on the dose rate—the degradation of mechanical properties was more significant at a low dose rate than at a high dose rate. It was found that the lower the dose rate, the higher the degree of oxidation in terms of the formation of γ-products. The mechanism of γ-degradation is discussed based on the correlation between the changes in chemical and physical properties upon exposure to γ-radiation.