Dielectric properties of POSS/LDPE and MgO/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. Furthermore, materials for applications for electrical engineering must also be able to evacuate heat. Therefore, the thermal properties of these nanocomposite materials need to be studied and evaluated in order to identify good candidates. In this paper, LDPE based nanocomposites reinforced by Magnesium Oxide (MgO) or Polyhedral Oligomeric Silsesquioxanes (POSS) were prepared either by mechanical alloying or by melt mixing and their dielectric properties were investigated for low loadings from 0 to 3 wt% in order to assess the efficiency of the compounding procedure in producing enhanced dielectric and thermal properties. The thermal step method was used to investigate the space charge behavior of the various nanocomposites. The space charge measurements have shown differences between the different nanocomposites reinforced by different kind of nanofillers and made by different preparation protocol. The thermal diffusivity behavior has also been investigated. None of the prepared nanocomposites showed significant increases in their dielectric losses in a broad range of frequencies and temperatures and no measurable increase in their dc conductivity.