RADIATION EFFECT ON POLYPROPYLENE STUDIED BY THE RELAXATIONAL BEHAVIOR AT LOW-TEMPERATURE USING POSITRON-ANNIHILATION

The irradiation effect of gamma-rays on polypropylene (PP) has been st udied through relaxational behaviour, using the positron annihilation lifetime (PAL) method. At low temperature, the intensity of a long-liv ed component of positronium, I-3, for unirradiated PP samples increase d due to a termination of the local thermal motion of polymer structur es. At 100 K, the increase in I-3 of 1 MGy gamma-ray irradiated sample s became very small. However, the increase was observed again in the P P samples after 48 h of irradiation by positrons during the PAL experi ment. This suggests a restructuring of the short polymer chains cut by gamma-ray irradiation may occur. Copyright (C) 1996 Elsevier Science Ltd.