Surface modification of h-BN and preparation of h-BN/PEI thermally conductive flexible films

Hexagonal boron nitride (h-BN) micro-platelets were surface-functionalized by sulfuric acid (SA). Such modified h-BN powders were mixed with thermoplastic polyether imide (PEI) to prepare flexible composite films using a solution casting method. After surface modification, the h-BN powders were uniformly dispersed in the PEI matrix. The thermal conductivity of the flexible composite materials was significantly improved, with a 60% increase over that of pure PEI. The mechanical properties of the composites were also measured and discussed. The Young's modulus of the h-BN/PEI composites was increased from 1.15 GPa for pure PEI to 1.62 GPa for the h-BN/PEI composite with a filling ratio 10 vol%. As compared to pure PEI film, the electrical breakdown strength of the composites with 5 vol% h-BN increased from 45.3 to 55.3 kV/mm. Our results show that the surface-modified h-BN filler is effective in improving the thermal conductivity and insulation performance of PEI-based composites.