Irradiation effects on aromatic polymers: 1. Gas evolution by gamma irradiation

The effects of gamma irradiation on aromatic polymers, such as polyimides (Kapton, Upilex-R and Upilex-S), poly(aryl ether ether ketone) (PEEK), poly(aryl ether sulphone) (PES), bisphenol A type Udel poly(aryl sulphone) (U-PS) and poly(aryl ester) (U-Polymer), were investigated based on gas evolution. The radiation resistance in terms of gas evolution was in the following order: Upilex-R ⩾ Kapton > PEEK > PES > Upilex-S ⪢ U-PS > U-Polymer. The G values of total gases from these aromatic polymers were 1100th to 11000th of the G values from aliphatic polymers. The major component gases were: H2 and N2 for polyimides; CO2 and CO for PEEK; CO2, CO and SO2 for polysulphones; and CO and CO2 for U-Polymer. The influence of crystallinity on the behaviour and yield of gas evolution was investigated in PEEK. Crystalline PEEK gave lower yield compared to amorphous PEEK. The radiolysis mechanism of gaseous products was discussed based on the structures of the aromatic polymers.