AN ESR STUDY OF THE INFLUENCE OF FATIGUE ON THE DECAY OF FREE-RADICALS IN GAMMA-IRRADIATED POLYCARBONATE

Polycarbonate was subjected to long-term stress by transverse bending. Stressed, as well as non-fatigued, samples were irradiated by gamma r adiation in evacuated ampoules. The concentration of free radicals was measured by ESR in the course of gradual heating of the samples. It a ppeared that the free radicals in the samples subjected to long-term s tress were more stable than the free radicals in the non-fatigued samp les. This suggests that the arrangement of polymer chains changes duri ng fatigue and the free volume in the proximity of radical centres dec reases so that the transfer of these centres to adjoining chains is re tarded. (C) 1997 Elsevier Science Limited.