Study on space charge behaviour in polyethylene doped with nano-montmorillonite

Space charge existed in polymer subjected DC high electrical stress has attracted more and more attention over the world. Various methods of inhibiting space charge generation and accumulation had been attempted in order to reduce insulation deterioration. In the present paper, the polyethylene/montmorillonite nanocomposites are prepared by melting intercalation process. The distribution of space charges in the nano-composite is investigated by means of pulse electric acoustic (PEA) method under different conditions. The effects of maleic anhydride grafted polyethylene (PEMA) on space charge characteristics of the composites are discussed. The test results indicate that the heterogeneous space charges in the nanocomposite near the cathode gradually decrease with PEMA content increasing. When PEMA content is 20%, the heterogeneous space charges near the cathode almost disappear at all in the nanocomposite. In short-circuiting process, the residual space charges in the nanocomposite with compatilizer obviously decrease comparing with origin LDPE. It is suggested that PEMA as a compatilizer can improve the interaction combination between LDPE and O-MMT, consequently interfacial traps reduce.

I. Introduction

Polymer insulating materials are widely applied to power apparatuses. Traditionally, additive agents and fillers are used to improve the electrical insulating properties or mechanical properties. Recently, nanocomposite materials have attracted more attention in the field of dielectric and electrical insulation [1]–[2]. A nanocomposite polymer is composed of nano-filler, of which diameter is as small as a few tens to a few hundreds of nanometers, and a polymer as a matrix. As the sectional area of the interface between the filler and the matrix is enormously large compared to that of conventional microcomposite materials, some improvement of insulating performance is expected to be realized by using such technology [3]. In order to suppress charge injection and accumulation, a significant amount of work has been carried out and various bulk modifications of polyethylene as one of the most important insulating materials have been made, such as incorporating different inorganic fillers, organic additives, or another polymer in the base material [4]–[10]. In this paper, low density polyethylene/organo montmorillonite (LDPE/O-MMT) composites are successfully prepared by melting intercalation. Distribution of space charge density in LDPE/O-MMT with different compatibilizer contents was measured