Highly thermally conductive flame-retardant epoxy nanocomposites with reduced ignitability and excellent electrical conductivities

A highly efficient phenylphosphonate-based flame-retardant epoxy resin (FREP) was firstly prepared from phenylphosphonic dichloride (PPDCl) and allylamine (AA). Functionalized graphite nanoplatelets (fGNPs) fillers were then performed to fabricate the fGNPs/FREP nanocomposites via mixing followed by casting method. The thermally conductive coefficient (λ), thermal diffusivity (α), flame retardancy, electrical conductivities and thermal stabilities of the fGNPs/FREP nanocomposites were all enhanced with the increasing addition of fGNPs fillers. The λ and α value of the fGNPs/FREP nanocomposite with 30 wt% fGNPs fillers was increased to 1.487 W/mK and 0.990 mm²/s, about 7 times and 6 times for that of pure FREP matrix (0.234 W/mK and 0.170 mm²/s), respectively. And the corresponding electrical conductivity was also increased to 5.0 × 10⁻⁴ S/cm, far better than that of pure FREP matrix (1.0 × 10⁻¹² S/cm). In comparison with that of pure FREP, the THR and TSP value of the fGNPs/FREP nanocomposite with 15 wt% fGNPs fillers was decreased by 37% and 32%, respectively, char yield was increased by 13%, and LOI value was increased from 31% to 37%. However, the peak of heat release rate of the fGNPs/FREP nanocomposite became worse due to its high thermal conductivity. Nanoindentation revealed that there was negligible influence of fGNPs fillers on the hardness values and Young's modulus of the fGNPs/FREP nanocomposites.