On the space charge and DC breakdown behavior of polyethylene/silica nanocomposites

Space charge occurs in a dielectric material when the rate of charge accumulation is different from the rate of removal, which arises due to moving or trapped charges. Inevitably, the local electric field is increased at some point within the material, which then leads to faster degradation and premature failure. The determination of space charge behavior has seen wide implementation in characterizing novel dielectric materials, especially in connection with the newly emerging field of nanocomposites. In this paper, we report on an investigation into space charge dynamics in silica-based polyethylene nanocomposites. The various systems differed with respect to the amount of filler and its surface chemistry; the pulsed electro-acoustic (PEA) technique was used to evaluate the space charge distribution in each. Experimental results indicate that the incorporation of nanosilica into polyethylene results in a significant amount of homocharge development near both electrodes. With appropriate surface treatment of the nanofiller, homocharge formation was successfully suppressed, indicating less severe space charge development in the nanocomposite materials. The mechanisms leading to the observed space charge development and direct current (DC) breakdown properties of the nanocomposites are discussed.