Changes in the mechanical properties and chemical structure of polystyrene by γ-irradiation

Abstract

The relationships between changes in the mechanical properties and chemical structure of polystyrene induced by γ-irradiation have been studied. The elongation at break decreased on irradiation in vacuo with doses above 50 Mrad, whilst no appreciable change was observed in the tensile strength. Both gel formation due to crosslinking and decrease in molecular weight by main chain scission took place competitively on irradiation in vacuo. The decrease in elongation at break in vacuo was related to both gel formation and decrease in molecular weight. Both elongation at break and tensile strength were decreased appreciably by γ-irradiation in air. The molecular weight decreased without gel formation on irradiation in air. The decrease in molecular weight was attributed to oxidative degradation leading to the formation of phenyl alkyl ketone end groups. The decreases in elongation at break and tensile strength in air were closely associated with the decrease in molecular weight. The radiation resistance of polystyrene, as measured by the changes in mechanical properties and molecular weight, etc., was greater in inflation molded film than in injected sheet.