Dielectric properties of various metallic Oxide/LDPE nanocomposites compounded by different techniques

Metallic oxide reinforced thermoplastics are good candidates as insulating material for HVDC cables because of their ability to limit or suppress space charges injection and accumulation. In this paper, LDPE based nanocomposites reinforced by Magnesium Oxide (MgO), Polyhedral Oligomeric Silsesquioxanes (POSS) or Zinc Oxide (ZnO) were prepared either by mechanical alloying or by melt mixing and their dielectric properties were investigated for low loadings from 0 to 5 wt% in order to assess the efficiency of the compounding procedure in producing enhanced dielectric properties. The thermal step method was used to investigate the space charge behavior of the various samples. The space charge measurements have shown differences between the different nanocomposites reinforced by different kind of nanofillers and made by different preparation protocols, just after manufacturing and also after different conditions of DC poling. None of the prepared nanocomposites showed significant increases in their dielectric losses in a broad range of frequencies and temperatures and no significant increase in their DC conductivity.