Abstract: Fiber-reinforced epoxy resin composite is widely employed in aerospace and other industries due to its low specific gravity, high specific strength, low curing shrinkage, and excellent corrosion resistance. However, the demand for thermal conductivity in this material has become increasingly stringent due to its special processing techniques and the heat dissipation requirements of the electronics and power industries. In this study, flame-retardant polyurethane open-cell foam (PUF) was used as a template; and nano boron nitride (BNNS) was introduced to modify this material. A low-loading boron nitride-polyurethane/fiberglass/epoxy thermal conductive composite was prepared using an impregnation-hot pressing method to investigate the effects of different BNNS contents on the thermal and electrical properties of the composite material. The results show that BNNS grows in situ on the three-dimensional skeleton surface of PUF, and as the BNNS content increases, the thermal performance of the composite material significantly improves. When the content of boron nitride nanosheets is 1vol%, the thermal conductivity of the composite material reaches 0.53 W/(m·K), which represents a 103% increase, while the coefficient of linear expansion decreases by 77.6%. With a BNNS content of 0.5vol%, the glass transition temperature of the composite material increases by 13.5 ℃, and it exhibits optimal thermal stability and mechanical properties. Moreover, thanks to the excellent insulation properties of boron nitride, the volume resistivity of the composite material is elevated to 7.2×10¹⁵ Ω·cm, and its arc resistance is significantly enhanced.

Key words: thermal conductive composite materials, polyurethane foam, boron nitride nanosheets, arc resistance performance, insulation performance