EFFECT OF PREMATURE CROSSLINKING AND THERMAL OXIDATION ON THE BREAKDOWN PERFORMANCE OF CROSSLINKABLE POLYETHYLENE INSULATING MATERIALS

Crosslinkable polyethylene insulation materials is widely used in high-voltage cables. However, premature crosslinking and thermal oxidation in the extrusion process of the insulating materials have a negative impact on the breakdown performance of the cable. In this work, the samples of insulating materials with different degrees of premature crosslinking and thermal oxidation are prepared, and the breakdown performance of insulating materials with and without antioxidants are compared. Gel content, crystallinity and carbonyl index have been obtained through experiments. The results show that the breakdown performance of the insulating materials depends on various factors such as the uniformity of crosslinked network, thermal oxidation, and crystallinity. The increase in defects under the combined effects of uneven premature crosslinking and thermal oxidation is the main cause of the decrease in breakdown strength and the increase in the dispersion of breakdown experimental data. What's more, hindered antioxidants can inhibit premature crosslinking and thermal oxidation, which can improve the breakdown performance of crosslinkable polyethylene insulating materials.