Effect of ageing on the dielectric relaxation of oriented and gamma irradiated LDPE

The influence of accelerated ageing on the dielectric relaxation of drawn a nd gamma irradiated low density polyethylene (LDPE) was studied through die lectric loss (tan delta) analysis in the temperature range from 25 to 325 K . The accelerated ageing was performed under 0.5 MPa pressure of oxygen at an elevated temperature (80 degreesC). The radiation induced and the post-i rradiation oxidation were observed using IR spectroscopy. The intensity and the position of the gamma and beta dielectric relaxation maxima (tan delta (max)) were found to be strongly dependent upon the changes in the microst ructure of the amorphous phase induced by crosslinking and oxidation. (C) 2 001 Elsevier Science Ltd. All rights reserved.