The Effect Of Particle Surface Modification On Dielectric Properties In Polymer Nanocomposite

Polyethylene, as a highly insulated material, has been successfully used for high voltage AC (HVAC) cables. However, in DC high field, attempts to widely use this material as cable insulation have failed, due to easy accumulation of space charge and the resulting distortion of local electric field. A small amount of inorganic nano-additives can make the dielectric properties of polymer material change a lot. Therefore, the use of inorganic nanoparticles on polyethylene modification becomes a hotspot in dielectric area.This article used three kinds of nano-SiO₂ particles with different size and surface modification as additive, studied the effect of nano-additive on microstructure, space charge distribution and conduction charactoristics of low density polyethylene (LDPE). The results show that, after doping different kind of nano-SiO₂ particles, the crystallinity of polyethylene changed and a strong interaction was formed between nanoparticle and LDPE molecules. Nano doping reduced the amount of space charge accumulated in polyethylene. With the increasing of doping content, the amount of space charge and charge decay rate during short-circuit both changed regularly. For virgin LDPE and nano-SiO₂/LDPE composite of lower content, the conductivity mechanism can be divided into three parts: Ohm conduction, Poole-Frenkle effect and hopping transport model; for nano-SiO₂/LDPE composite of higher content, the conductivity mechanism can be divided into two parts: Ohm conduction and hopping transport model. Particle size and surface treatment only made quantitative change for the amount of space charge and the value of conductance current, but made no effect on the overall trend of charge transport property.Based on a large number of experimental data, the mechanism of charge generation, transportation and accumulation of nano-SiO₂/LDPE composite was discussed. The results of this article will surely provide a theoretical basis and experimental evidence for the development and application of new DC cable insulation material.