Abstract
Epoxy–boron nitride composites are promising insulating materials, and it is highly important to understand their insulating performances at different temperatures with different nano-doping amounts. In this study, we investigated the effects of different mass fractions of epoxy–micron hexagonal boron nitride composites on their thermal conductivity, as well as the effects of temperature and mass fraction on their insulating performances. The results demonstrated that the thermal conductivity of epoxy–micron hexagonal boron nitride composites was superior to that of neat epoxy. The thermal conductivity of epoxy–micron hexagonal boron nitride composites increased with the mass fraction of hexagonal boron nitride, and their dielectric constant and dielectric loss increased with temperature. The dielectric constant of epoxy–micron hexagonal boron nitride composites decreased as the mass fraction of hexagonal boron nitride increased, while their dielectric losses decreased and then increased as the mass fraction of hexagonal boron nitride increased. Due to internal heat accumulation, the alternating current breakdown strength of epoxy–micron hexagonal boron nitride composites increased and then decreased as the mass fraction of hexagonal boron nitride increased. Additionally, as the temperature increased, the composites transitioned from the glassy state to the rubbery or viscous state, and the breakdown strength significantly degraded.
Highlights
Due to their excellent mechanical and insulating properties, epoxy-based materials have been widely applied in electrical equipment [1,2], but they suffer from poor heat dissipation, resulting in heat accumulation during operation and accelerated aging
The thermal conductivity of composites increased with the massfraction of h-Boron nitride (BN)
As the mass fraction of hexagonal boron nitride (h-BN) filler increased, the heat distribution ranges of composites at the same moment expanded, the hot spot temperature decreased, and the thermal conductivity increased more rapidly
Summary
Due to their excellent mechanical and insulating properties, epoxy-based materials have been widely applied in electrical equipment [1,2], but they suffer from poor heat dissipation, resulting in heat accumulation during operation and accelerated aging. Due to the rapid development of power systems, electrical equipment is becoming increasingly miniaturized, having large capacity and high dielectric strength, resulting in strict requirements for their thermal conductivity and insulating performance [5,6]. Boron nitride (BN) nanosheets have been widely applied as high-voltage insulating materials due to their superior thermal conductivity and insulating performance [9]. The addition of micron-sized hexagonal boron nitride (h-BN) particles into an epoxy resin matrix can significantly enhance the thermal conductivity and electrical properties (e.g., dielectric performance and breakdown strength) of composites at room temperature [10].
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