Space charge in LLDPE loaded with nanoparticles

Fillers are widely used in insulation systems to achieve specific electrical, mechanical and thermal properties. Recently, polymer nanocomposites have attracted significant attention as a means of improving their performance and widening their utility. To better use the nanocomposites, a thorough understanding of interaction between nanoparticles and their matrix is important. The interaction can be studied by various methods. In the present study we focus our attention on space charge dynamics of linear low density polyethylene (LLDPE) loaded with nanometric size aluminium oxide (alumina) under dc electric fields. To obtain a good dispersion of nano fillers in LLDPE, a Brabender mixer has been utilised. Four types of LLDPE nanocomposite films were prepared with concentrations of alumina of 0, 1, 5 and 10 wt% for space charge measurements. They were electrically stressed at three electric field levels of 10, 50 and 100 kV/mm and space charge dynamics during stressing period and decay after the removal of the applied electric field were observed. The results show that space charge dynamics in nanocomposites are dependent on both content of filler and the applied electric field. Generally, the amount of space charge in the sample with 1% of alumina is less while there is a significant change in characteristics in the sample loaded with 5% alumina or more. In particular, the electrical performance in the sample with 10% alumina deteriorates, indicating there is an optimal load of alumina.