Effects induced by gamma irradiation of different polyesters studied by viscometry, thermal analysis and positron annihilation spectroscopy

An experimental study on different polyesters (PET, PBT, PEN, PEA, PCT-co-ET) subjected to γ-irradiation up to 1 MGy was carried out through viscometry, thermal analysis and positron annihilation lifetime spectroscopy. Chain scission induced by irradiation prevails for doses up to 100 kGy; it is influenced by the length of the aliphatic chain as well as by the presence of the aromatic ring. Crosslinking dominates for doses between 100 and 300 kGy, while the oxidative degradation mechanism, present at the highest doses, increases its importance with the amorphous fraction of the polymer. Free volume structure is not modified by irradiation.