Dielectric properties of LDPE/clay nanocomposites

Polymers can be reinforced by layered silicate fillers leading to polymeric nanocomposites with altered dielectric properties, often superior breakdown and endurance strength than those of neat polymers can be observed. In addition, mitigation of space charge accumulation can potentially be reached with such nanocomposites, for several reasons such as the barrier effect of the platelets, ionic trapping of the inorganic filler and also a slight increase of the DC conductivity allowing space charges to slowly flow across the insulation wall instead of accumulating inside the insulation bulk. In this paper, the dielectric response of LDPE/clay nanocomposites, with and without a polyolefin-based compounding compatibilizer, was investigated as well as the space charge formation. The dielectric responses were investigated as a function of the temperature in a broad range of frequencies. The space charge behaviour has been investigated by using a non-destructive measurement technique called the Thermal Step Method, after an electrical and thermal poling. A comparison between the different materials with different nanofiller contents was carried out showing different space charge behaviours and highlighting an optimal nanofiller content for a minimal space charge accumulation. A correlation with the frequency-domain dielectric responses performed under low applied electric field was also done.