Thermal Conductivity of Epoxy Composites Filled with Silane-Modified Boron Nitride Nanosheets

This study investigates the exfoliation of hexagonal boron nitride (h-BN) into boron nitride nanosheets (BNNS) and their subsequent functionalization for high-performance epoxy composites. To enhance the dispersibility of BNNS in solvents, combined hydrothermal and sonication treatments were used. Additionally, the BNNS surface was modified with less than 3% of 3-aminopropyltriethoxysilane (APTES) to improve interfacial adhesion. The physical properties of the treated BNNS, including layer number, interlayer interactions, and functional group attachment, were systematically analyzed. Incorporation of APTES-functionalized BNNS (APTES-BNNS) into the epoxy matrix significantly enhanced the composite's thermal properties, primarily due to improved filler dispersion and stronger interfacial interactions. As a result, the composite achieved a thermal conductivity of 4.32 W/m·K, representing a 21.6-fold increase over the epoxy matrix. Notably, while thermal conductivity was greatly improved, the composite's electrical resistivity remained above 10¹⁶ Ω·cm. These findings indicate that APTES functionalized BNNS/epoxy composites are promising for thermal management applications that require both high thermal conductivity and excellent electrical insulation.