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During the breaking process of high voltage circuit breaker (HVCB), the arcs generated between the contacts may cause severe ablation of the nozzle, shortening the life of HVCB. Therefore, it is necessary to study the nozzle material with better ablation resistance. Polytetrafluoroethylene (PTFE)/boron nitride (BN) composite materials are commonly used in the industry to prepare nozzles. The particle size of BN can affect the ablation resistance of PTFE/BN composites, but the law is still unclear. In this paper, several kinds of PTFE composite samples doped with different nanoscale and micron-scale BN were prepared to study the effect of BN size on ablation resistance. The experimental results show that micron-scale BN fillers are more effective for improving the ablation resistance. With the increase of micron-scale BN particle size, the arc ablation resistance becomes better first and then worsens. The results are discussed and explained from the perspective of thermal transport and spectral reflectance characteristics.

With the development of high voltage transmission, higher voltage is necessary. Power equipment with traditional materials can not satisfy the insulation requirement of higher voltage transmission, so excellent material is urgently needed. PTFE nozzle is important in circuit breaker which faces the problem of arc ablation, and the nozzle with better performance is helpful to improve the transmission voltage. In this paper, in order to study the influence of different pressing pressures and modes on the ablation performance of PTFE/BN composites, four pressures and two modes were adopted (cold isostatic pressing and mould pressing) to obtain 7-wt% BN doped PTFE composites. As the pressing pressure increases, the ablation amount of the specimen decreases gradually. Compared with mould pressing, the specimen prepared by cold isostatic pressing has a higher thermal conductivity and lower ablation amount, while the light reflection properties are almost the same for both preparing methods. This paper is of great significance to improve the ablation resistance of nozzle materials.