Electrical tracking characterization of LLDPE-Natural Rubber blends filled with nanofillers

Electrical tracking is a process of formation of permanent conducting path across the insulating material due to the surface erosion under high voltage application. The existing of leakage current (LC) on the wet contaminated material surface causes the generation of surface discharges that resulted to the material degradation. Electrical tracking test can be indicated as failure when LC exceed 60 mA for more than two seconds or at least 25mm of formation of carbon track or erosion breaks through the thickness of the sample. In this paper, a new formulated thermoplastic elastomer material which composed of Linear Low-Density Polyethylene with Natural Rubber (LLDPE/NR) filled and unfilled with different percentage of silicone oxide (SiO₂) or titanium oxide (TiO₂) as nanofiller is presented. The compound was tested based on IEC 60587 inclined plane tracking test procedure. The analysis of LC and rate of carbon track development were also conducted. Surface morphology analysis was carried out for investigating the degraded surface structure of the materials. The formulation of pure LLDPE/NR has shown the highest average leakage current whereas the composition of LLDPE/NR-TiO₂ with 1 % wt of nanofiller was found to be the best electrical tracking resistance due to the lowest average leakage current and no carbon track appeared. The blends of LLDPE/NR-SiO₂ show that low average leakage current and no carbon track in less than 5 % wt nanofiller. The usage of 5% wt or more for both nanofiller had shown the worst in carbon track formation.