Simulation of space charge behavior in LDPE/silica nanocomposite with a modified model

The charge transport behavior is changed when low-density polyethylene (LDPE) filled with a few percent nanometer fillers. In this paper, a modified of bipolar charge transport model considered the influence of impurity ion is present to investigate the space charge behavior in nanocomposite. The impurity ion transport consists of ion generation by field assisted dissociation of impurities, transport, trapping and recombination in polymer. Space charge distribution was acquired by pulse electro acoustic method, in order to provide simulation reference. Obviously, the heterocharge accumulates adjacent anode and cathode in LDPE, respectively. After filled with nano-filler, polarity of space charge near anode and cathode changed with the increase of the nano-filler content, respectively. Compared with the result of simulation and experiment, it is clear that there are some limitations on the bipolar charge transport model and impurity ion transport model, due to the limitation on charge source. However, the combination of both models could not only simulate the heterocharge accumulation in pure LDPE, but also describe the threshold field characteristic of apparent space charge accumulation. Furthermore, it could simulate the trend from heterocharge accumulation to homocharge accumulation in nanocomposite with the increase of filler concentration.