Constructing integrated thermal conductive and flame-retardant filler network in ceramifiable epoxy composites

Simultaneously improving the thermal conductivity and flame resistance of epoxy composite is still a challenge. Herein, a novel epoxy composite with high thermal conductivity and greatly enhanced flame retardancy was developed through constructing integrated three-dimensional (3D) network based on boron nitride (BN), talc, ammonium polyphosphate (APP). The thermal conductivity of the composite with filler network reached 3.04 Wm⁻¹K⁻¹, which was 15.2 and 3.1 times of those of pure epoxy and sample with random filler distribution. The LOI value of the composite with filler network reached 37.8%, which was 1.9 and 1.4 times of those of pure epoxy and sample with random filler distribution, respectively. In addition, the effects of various combinations of filler on the flame resistance of the epoxy composite were also evaluated. The prepared composite with filler network exhibited excellent shape stability and mechanical strength even after ablation at 1000°C. The network structure constructed by BN had a positive effect on heat transfer, while APP led to the formation of phosphoric acid at high temperature, adhering to talc and other residues together. A ceramic-like residue was formed on the firing surface, which enhanced the barrier effect of char layer and flame resistance of the composite.