Physical properties of biaxially oriented poly(ethylene terephtalate) irradiated at different temperatures and doses with electron beam

• E-beam produced chain scission and a decrease in molecular weight in PET.
• Melting point decreased and crystallinity increased with the increase in dose.
• Crystallization temperature increased with the increase in absorbed dose.
• Mechanical properties were strongly affected by absorbed dose.
• Irradiation above Tg degraded PET more than irradiation at ambient temperature.

The electron beam irradiation of a biaxially oriented PET film was carried out in air over a range of 50–3000 kGy at different temperatures and a dose rate of 4.48 kGy min−1. The effects of the irradiation at temperatures above and below the glass transition temperature (Tg) on the thermal and mechanical properties were studied. Melting temperature decreased slightly and crystallization temperature and crystallinity increased significantly with the increase in dose, more at higher irradiation temperature, whereas Tg did not show any significant change with dose or temperature. Mechanical properties were adversely affected by irradiation. Stress and strain at break were strongly reduced, more at higher irradiation temperature, and Young's Modulus slightly increased with the increase in dose. The changes in properties were related to the chain scission produced by the electron beam irradiation leading to a decrease in molecular weight.