Space Charge Characteristics of Epoxy/BN nanocomposites by using Surface Modification

Improving the space charge accumulation of epoxy resin insulation can improve the reliability of HVDC power devices. This work investigates the surface modification of hexagonal boron nitride (h-BN) by silane coupling agent, which could improve thermal conduction while restraining space charges of epoxy resin. Surface modified BN (KBN) was produced by the hydrolysis reaction method. The epoxy/BN nanocomposites with different nanoparticle contents were produced using suitable dispersing and curing techniques. FTIR and SEM were used to characterize the chemical grafting and dispersity of the nanocomposites. The measured space charge behavior was then analyzed and discussed. The results show that the silane-oxygen groups appear on the BN surfaces after modification, increasing the chemical compatibility between BN and epoxy resin matrix. Incorporation of 1% by weight of KBN makes it possible to effectively suppress space charge accumulation at 20 kV/mm. Whereas for high content samples (10 wt%), a small amount of positive charge accumulations can be observed near the anode. The introduction of shallower traps responds to the positive charge accumulations. Given the deep trapping at the interface, the height of the injection barrier is increased in the low grade samples. Future work should be focused on the interface states near the electrodes.