Polyethylene crosslinked in different media: structural changes versus dielectric behaviour

Changes in the structure and dielectric properties of low-density polyethylene were created by gamma irradiation in air, deionised water and nitrogen. Role of irradiation media on dielectric and charge trapping behaviour was studied through dielectric loss and thermally stimulated discharge current measurements. Changes in magnitude, position and activation energy of all dielectric relaxations (gamma, beta and alpha) were found to be dependent on crosslinking and oxidative degradation, two competitive processes which can be tuned by radiation dose and media. Largest changes in the position and activation energy were found for the beta relaxation due to its cooperative nature.