Influence of nanoparticle surface coating on electrical conductivity of LDPE/Al2O3 nanocomposites for HVDC cable insulations

Artikel i vetenskaplig tidskrift, 2017

LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. The surface coating of the nanoparticles is a key step to achieve well-balanced properties. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al2O3 nanocomposites. Al2O3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, octyl and octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m-3, indicating a porous nature on the nanoparticle surface. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbour particle distance. The electrical conductivity of the nanocomposites was determined at 40 and 60 °C. The results show that an appropriate surface coating on the nanoparticles maintained uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. Large particle agglomerates were found to increase the electrical conductivity of the nanocomposites. The composites based on the highly porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.