THERMOOXIDATIVE STABILIZATION OF PHOTOCHEMICALLY CROSS-LINKED POLYETHYLENE

Crosslinking efficiency and oxidative stability have been studied for a series of PE films containing different antioxidants as a function of exposure time and nature of photoinitiator. The striking difference between two groups of photoinitiators examined was demonstrated by comparing the oxidation induction periods of crosslinked samples. Crosslinking in the presence of sulfuryl chloride, phosphorus trichloride or phosphorus oxychloride results in dramatic decrease of the thermostability of the films, whilst using sulfur monochloride or thiophosphoryl chloride as the photoinitiator causes an initial drop of oxidation induction period which is followed by an increase after further UV irradiation. Thus photocrosslinking of PE can be accompanied by an increase of its thermostability in certain conditions.