BNNS Encapsulated TiO₂ Nanofillers Endow Polypropylene Cable Insulation with Enhanced Dielectric Performance

In this work, nano-titanium oxide (TiO2) is encapsulated into boron nitride nanosheets (BNNS) by the calcination process to fabricate core-shell structured TiO2@BNNS nanofillers. The effects of TiO2@BNNS fillers on the DC conductivity, space charge and breakdown strength of polypropylene (PP) composites are investigated. Experimental results show that PP/TiO2@BNNS composites have a lower temperature-dependent conductivity with an activation energy of 0.64 eV, which is much lower than that of PP, 0.95 eV. The DC breakdown strength of PP/TiO2@BNNS samples is 22.2% higher than that of PP at 90 °C. The average space charge density and electric field distortion rate of PP/TiO2@BNNS are reduced by 6.6 C/m3and 23.3%, respectively, compared with PP, under a polarization electric field of 40 kV/mm at 90 °C. It is proven that TiO2@BNNS nanofillers form numbers of electrical potential wells for charge carriers, thereby, inhibiting the hot electron transport and their damage to polymer molecules. This work provides an effective method to improve the dielectric performance of PP cable insulation.