Electrical insulating characteristics of polymer nanocomposites for high voltage applications

Abstract

Polymer nanocomposites have attracted wide interests in electrical insulating society due to its potential properties enhancement. In the present work, high density polyethylene (HDPE) nanocomposites containing 2 wt%, 5 wt% and 8 wt% of nanosized organically modified montmorillonite clay (nanoclay) were investigated, with unfilled HDPE served as reference material. The nanocomposites were prepared by using Brabender Plasticorder twin screw extruder. Scanning Electron Microscope (SEM) characterization was performed to determine the dispersion state of nanoclay in HDPE. Electrical insulating properties, mainly the surface tracking and internal discharge characteristics were investigated based on BS EN 60587: 2007 and CIGRE Method II test standards respectively. It was found that nanoclay negatively affected the surface tracking property of HDPE, in which higher amount of nanoclay causes more severe tracking progression. A degradation mechanism leading to the adverse effect of nanoclay towards surface tracking was proposed. In addition, contact angle measurement was performed to determine the hydrophobicity of the test samples. Results indicate that HDPE nanocomposites were less hydrophobic than unfilled HDPE. For internal discharge test, unfilled HDPE shows the highest resistance towards internal discharge. Interestingly, among nanocomposites, higher loading of nanoclay improved the internal discharge performance of the insulating material. Meanwhile, thermal characterization through Differential Scanning Calorimeter (DSC) shows that there is no significant difference observed for melting and cooling endotherms of HDPE nanocomposites and unfilled HDPE.