Preparation of Hexagonal Boron Nitride-Containing Foam with Improved Thermal Conductivity of Epoxy Resins

With the continuous development of electrical and electronic devices, the thermal conductivity of dielectric polymer composites within devices is becoming increasingly important. However, improving the thermal conductivity usually requires the incorporation of a large amount of filler in polymer material, which undoubtedly increases the production cost while destroying the processability and the dielectric properties of the material. In this work, an efficient heat transfer network was constructed inside the resin matrix to overcome this drawback. Using the opposite surface potentials of hexagonal boron nitride (h-BN) and polyethyleneimine (PEI) in solvent, h-BN was anchored on the surface of melamine foam (MF) by an electrostatic self-assembly technique to construct a thermal conductive skeleton with a three-dimensional open pore structure, and the corresponding epoxy (EP) composite was prepared by vacuum-assisted impregnation. This EP–MF@BN composite showed a significant increase in the heat arrival rate at an extremely low filler loading. At a h-BN loading of 2.1 wt %, the thermal conductivity of the composite reached 0.433 W/(m·K), which was 147% higher than that of the pure resin matrix. This is mainly attributed to the unique three-dimensional open-hole structure of the MF foam, which formed a three-dimensional frame structure with extremely low thermal resistance after anchoring by h-BN, thus providing a great degree of weakening of the scattering behavior during phonon transport. In addition, the transport behavior of carriers inside the composite under strong electric field conditions was analyzed in the current study. This strategy of constructing an efficient heat transfer network inside the polymer matrix provides an idea and method for the preparation of composites in the field of electrical insulation.