Enhancing Dielectric Strength and Thermal Conductivity of Synthetic Ester Oil Using Surface-Modified h-BN Nanoparticles

Synthetic ester insulating oil is an ideal environmentally friendly alternative to mineral oil in power equipment. However, its inherent low thermal conductivity and dielectric strength issues have limited its application in high-power equipment. To break through the above bottlenecks, this paper proposes to prepare high - performance nanocomposite insulating oil by modifying hexagonal boron nitride (h - BN) nanoparticles with γ-Aminopropyltriethoxysilane ( KH550 ) silane coupling agent. The effective grafting of KH550 onto h-BN surfaces was verified by Fourier transform infrared spectroscopy (FTIR) and X - ray photoelectron spectroscopy (XPS). The breakdown voltage, dielectric properties, kinematic viscosity, and thermal conductivity of the insulating oil at different nanoparticle concentrations were experimentally tested, and the mechanism of performance improvement was analyzed from the microscopic level combined with molecular dynamics simulation. The results show that when the addition concentration of KH550 - hBN is 0.05 g/L, the breakdown voltage increases to 81.62 kV, and the thermal conductivity reaches 0.1656 W/(m·K), which are about 23.2% and 17.5% higher than those of the base oil respectively, and the dielectric loss is significantly reduced at the same time. Appropriate addition of nanoparticles can effectively enhance the comprehensive performance of synthetic ester, while an excessively high concentration will lead to performance degradation due to the agglomeration effect. Molecular simulation shows that the modified h - BN introduces electronic traps and optimizes the interface charge distribution, which helps to suppress the migration of free electrons and the development of partial discharge. In addition, the nanoparticles form heat - conduction paths in the oil, improving the heat - dissipation capacity. The research results provide experimental basis and theoretical support for the design and application of high - performance nano - modified ester insulating oil.