Irradiation of polyethylene: Some aspects of crosslinking and oxidative degradation

Crosslinking is the dominant process when polyethylene is irradiated under inert atmosphere; however, when it is irradiated in air, oxidative degradation becomes the dominant process, particularly at low-dose-rate gamma irradiation. There have been suggestions in the literature that (i) crosslinking may still be an important process during low-dose-rate gamma irradiation, and (ii) that peroxides can act as sensitizers for radiation-induced crosslinking of polyethylene. A consideration of possible radiation effects in polyethylene, in the presence of oxygen, suggests that there could be (i) an important role of cationic reactions leading to crosslinking; (ii) possible crosslinking within the crystalline regions; and (iii) excitation energy transfer to the peroxides produced during oxidative degradation to produce alkoxy radicals. (C) 1999 Published by Elsevier Science Ltd. AII rights reserved.