DOSE-EFFECT IN GAMMA-IRRADIATED POLYETHYLENE STUDIED BY POSITRON-ANNIHILATION LIFETIME TECHNIQUE

Commercial high-density polyethylene (HDPE) samples were irradiated by gamma-rays with doses ranging from 10 to 200 kGy. Positron annihilation lifetime measurements were performed to study the effect of gamma-radiation on the structure of polyethylene. The lifetime tau3, associated with the pick-off process, in which the positron in o-Ps annihilates an electron from the surrounding material, and its intensity I3 are measured as a function of gamma-dose. It can be concluded that the effect of gamma-irradiation on polyethylene results in intensive formation of new bonds or crosslinking at doses ranging from 10 to 100 kGy. Saturation of I3 for the irradiated HDPE at doses ranging from 100 to 200 kGy may indicate the achievement of a structural stability.