Research on the Stability and Response of Food Packaging Polystyrene Resin Materials to γ-ray Irradiation

Radiation stability of food packaging materials is the key to ensuring food quality. In this study, ⁶⁰Co γ-ray was selected to investigate the radiation resistance of food packaging polystyrene (PS) resin material, although the FTIR analysis showed that the intensity of several peaks decreased slightly. The gel permeation chromatography (GPC) results displayed that the value of peak molecular weight (Mp) of PS went from 2.68 × 10⁵ g/mol down to 2.22 × 10⁵ g/mol. Moreover, the residual mass (Res) of PS increased from 7.208 to 30.23%, indicating that the tendency of coking of PS was stronger after irradiation. In addition, the peak intensities of the three main pyrolysis products -CH₂-, CH₄, and CH₂=CH₂ increased by more than 30% compared to unirradiated PS, and a large number of them were detected in the whole pyrolysis process. Moreover, mechanical property analysis finds that both breaking strength and elongation data increased before irradiation dose of 50 kGy, then, decreased sharply with further increase of irradiation dose. The theoretical bond order analysis confirmed that the tertiary carbon bond attaching the benzene ring had the lowest bond energy. This study can give helpful guidance when using PS for food packing materials.