Ageing and degradation mechanism of linear low density polyethylene-natural rubber composites due to partial discharge

Ageing and degradation mechanism of linear low density polyethylene (LLDPE)-natural rubber (NR) composites after subjected to partial discharge (PD) activities is presented in this paper. The LLDPE-NR blends and LLDPE-NR composites containing nano-sized fillers, montmorillonite (MMT) and Titanium (IV) Oxide (TiO₂) were produced by a twin-screw extruder. The Maleic anhydride grafted linear low-density polyethylene (LLDPE-g-MAH) of 10 wt% was added as a compatibilizer. The entire of LLDPE-NR blends and composites were conducted with partial discharge test according to CIGRE Method II. Surface of LLDPE-NR blends and composites specimen showed severe chalking and discoloration on the side of high voltage electrode. The surface morphological changes were studied in detail using Scanning Electron Microscope (SEM) and Energy Disperse X-ray spectroscopy (EDX). The SEM micrographs of aged LLDPE-NR specimens showed that the surface structure become porous and degradation appeared. The longer of ageing time result the more severe degradation on the surface of specimens. In addition, the morphological analysis result based on the EDX spectrum of the degraded LLDPE-NR composite specimen revealed the existence of O_1s peak anticipates that the oxidation of the insulation specimen proceeded.