Inhibition Effect of Graphene on Space Charge Injection and Accumulation in Low-Density Polyethylene.

Zhonglei Li,Jingang Su,Chenlei Han,Zhaohao Hou,Boxue Du

doi:10.3390/nano8110956

Abstract

Space charge injection and accumulation is attracting much attention in the field of dielectric insulation especially for electronic devices, power equipment and so on. This paper proposes using the inhibition effect of graphene for the injection and accumulation of space charge in low-density polyethylene (LDPE). Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were employed to observe the dispersion of graphene with a two-dimensional structure in LDPE. The time-dependent space charge dynamic behaviors of graphene/LDPE nanocomposites with the filler content of 0, 0.003, 0.005, 0.007 and 0.01 wt % were characterized by the pulsed electro-acoustic (PEA) test at 40, 60 and 80 °C, and the charge mobility was evaluated by its depolarization processes. The experimental results show that for the undoped LDPE film, large amounts of space charges were injected from the electrodes into samples, especially at 60 and 80 °C. The graphene/LDPE nanocomposites with a filler content of 0.005 wt % could markedly suppress the space charge injection and accumulation even at 80 °C, which is attributed to the large quantities of graphene-polymer in interface regions. These interface regions introduced numbers of deep trap sites within the forbidden band of nanocomposites, which can reduce the de-trapping rate of charges and suppress the space charge accumulation in the polymer bulks. The graphene/LDPE nanocomposites are suggested for dielectric applications, intending the inhibition of space charge injection and accumulation.

Highlights

Polyethylene-based insulating materials, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), cross-linked polyethylene (XLPE) and so on, are widely used for electrical insulation, due to their excellent electrical and mechanical properties [1,2,3]
It is found that the melting peak temperature increased by 5.3 ◦C with the filler content increasing from 0 to 0.01 wt %
The profiles of space charge tended to be relatively stable up to 30 min. This phenomenon was exactly similar to the results reported by [8], in which the space charge polarity in the vicinity of anode reversed with the temperature rising from 30 to 50 ◦C for XLPE under 30 kV/mm

Summary

Introduction

Polyethylene-based insulating materials, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), cross-linked polyethylene (XLPE) and so on, are widely used for electrical insulation, due to their excellent electrical and mechanical properties [1,2,3]. Space charge characteristics are attracting much attention along with the rapid development of direct-current electronic devices and power equipment during the past decade. With an increase of the voltage level, the miniaturization of electrical devices and the rise of operation temperatures, the space charge injection and accumulation will be further exacerbated and become one of the critical issues for the development of PE-based insulation. The suppression of space charge injection and accumulation has been a research focus in the field of electrical insulation

Methods

Results

Discussion

Conclusion