Boron nitride nanosheets endow the traditional dielectric polymer composites with advanced thermal management capability

Dielectric polymer composites with high thermal conductivity have increased applications in electrical and electronic systems. However, the increase of thermal conductivity is usually achieved by increasing filler loading, which results in deterioration of processing and dielectric property. In this work, a hybrid filler strategy for overcoming the shortcoming is reported. In the strategy, the traditional α-Al2O3 microspheres were encapsulated by boron nitride nanosheets (BNNSs). Both types of filler were treated by reactive silanes, resulting in chemical bonding between α-Al2O3 and BNNSs. Epoxy composites with the BNNS encapsulated α-Al2O3 (Al2O3@BNNS) and randomly dispersed hybrid filler (Al2O3&BNNS) were also prepared. It is interestingly found that at the same filler loading, the Al2O3@BNNS composites exhibit much higher thermal conductivity when compared with the Al2O3 composites and the Al2O3&BNNS composites. At a filler loading of 65 vol% and an optimal BNNS to α-Al2O3 ratio of 1 : 7, the Al2O3@BNNS composite exhibit a thermal conductivity of 2.43 W/(m·K), which is 73.9% higher than that of the Al2O3 composite and is also about 20% higher than that of the Al2O3&BNNS composites. This facile strategy opens a new avenue for upgrading and updating the traditional dielectric polymer composites in the field of dielectrics and electrical insulation.