Charge storage and transport in high density polyethylene and low density polyethylene

High density polyethylene (HDPE) and low density polyethylene (LDPE) are widely used as dielectrics and insulating materials. In this paper, the influence of heat treatment during and after corona charging on charge storage stability and the transportation of detrapping charges in the bulk of HDPE and LDPE were investigated by isothermal surface potential decay and open-circuit TSD analysis. The shifts of mean charge depth for the two kinds of PE at different charging temperature and environmental humidity were measured by heat pulse technique. Comparison of electret behaviors for the two kinds of PE was studied. The experimental results indicated that: (1) with increasing charging temperature and environment humidity, the mean charge depth for the two kinds of materials shifts toward the bulk from the free surface of the sample, especially in high temperature and humidity. (2) the charge storage stability can be improved significantly by heat treatment.