Flame retarding epoxy composites with poly(phosphazene-co-bisphenol A)-coated boron nitride to improve thermal conductivity and thermal stability

Based on the template-induced self-assembly characteristic of cyclomatrix polyphosphazene micro–nanometer materials, novel poly(cyclotriphosphazene-co-bisphenol A)-coated boron nitride (PCB-BN) was designed and synthesized by in situ condensation polymerization on the surfaces of boron nitride (BN) particles using the reaction of hexachlorocyclotriphosphazene (HCCP) with bisphenol A (BPA). It was found that the incorporation of PCB-BN particles in the epoxy matrix significantly enhanced thermal conductivity of the epoxy composites. With 20 wt% PCB-BN loading, the thermal conductivity of the EP/PCB-BN composites was 0.708 W m−1 K−1, which was 3.7 times higher than that of the neat epoxy. Meanwhile, the EP/PCB-BN composites possessed good electrical insulation and thermal stability simultaneously. The composites fabricated also exhibited improved flame retardation and superior dimensional stability during combustion.