Multiple synergistic effects of graphene-based hybrid and hexagonal born nitride in enhancing thermal conductivity and flame retardancy of epoxy

Abstract

The heat shock, thermal aging and fire hazard of induced by delayed heat diffusion in microelectronic devices require a high-efficiency thermal management system with high-performance electronic packaging materials. In this work, the significant thermal conductivity and flame retardancy of polymer-based thermally conductive composites (PTCs) are addressed by multiple synergistic effects of hexagonal born nitride (hBN) and few flame-retardant functionalized graphene. Briefly, a multifunctional hydrophilic graphene-based hybrid containing Ni(OH)2 nanoribbons and reduced graphene oxide (RGO) was synthesized by two-step hydrothermal process. The resulted RGO@Ni(OH)2 hybrid and hBN sheets (lateral size of 4.37 ± 1.68 μm and thickness of 80 ± 21 nm) used as synergistic and main fillers, respectively, was simultaneously added into EP matrix. As expected, the binary fillers showed multiple synergistic effects for improving the thermal conductivity and flame retardancy of composites. Typically, the good dispersion and interfacial interaction of RGO@Ni(OH)2 hybrid in matrix can not only inhibit the stacking aggregation behavior of hBN sheets, but also bridge adjacent hBN sheets, both of which resulted in a high thermal conductivity (2.01 W/mK) of ternary composites with a synergistic increment of 39.4% comparing to EP/hBN. On the other hand, their synergistic flame retarding effect including catalytic carbonization, endothermic action and barrier effect induced by RGO@Ni(OH)2, as well as “tortuous path” effect of hBN sheets, jointly led to the formation of a compact and robust char layer in condensed phase during combustion. As a result, EP/hBN/RGO@Ni(OH)2 exhibited a desired flame ratardancy with considerable reductions being seen in peak heat release rate, total heat release and total smoke production, i.e., 33.5%, 33.8% and 43.0% comparing to neat EP.