||Long-term Oxidative Degradation of Electron Beam Irradiated High Density Polyethylene Studied by Positron Annihilation Technique
Structural change and degradation of electron-beam irradiated high density polyethylene was investigated by a conventional positron annihilation lifetime spectroscopy (PALS) using 22Na positron source, gel fraction measurement, and micro-FT-IR spectroscopy immediately after the irradiation and after 3 years storage in air. The pick-off annihilation intensity of ortho-positronium (o-Ps) became small by the irradiation and after the storage maybe due to the trapping of positron by radicals/carbonyl groups. On the other hand, o-Ps lifetime did not change by the irradiation and the storage. It suggests that size of nanometer-sized free-volume is not affected by the structural change such as oxidation and cross-linking.
The 13th meeting of the “Ionizing Radiation and Polymers” symposium (IRaP2018)