Investigation of electrical properties of LDPE/ZnO nanocomposite dielectrics

In order to investigate the effect of inorganic nanoparticle fillers on the electrical properties of low density polyethylene (LDPE), LDPE/ZnO nanocomposites were prepared with a variety of filler loadings by melt blending method and the corresponding electrical properties are investigated. Experiments show that, the trap density is increased by 3-5 times in the nanocomposite as compared with LDPE. The conduction current of the nanocomposite is decreased to 0.5 - 0.25 of the value of LDPE both at low and high electric fields. The electrical breakdown strength is increased at low filler contents and decreased at high contents (>1 wt%). The electrical treeing life time is elongated 50 times at most in the nanocomposites. Both homo- and hetero-space charges are remarkably suppressed in the nanocomposite with 0.5 and 7 wt% contents. The study indicates that the improvements on the electrical properties, especially the charge transport and space charge suppression in the nanocomposites are closely related to the significant increase of deep trap density. The effect of UV light absorption and electric field homogenization by ZnO can also contribute to the enhancement of electrical breakdown strength and elongation of electrical treeing life.