High-temperature resistant bio-based phthalonitrile/graphene nanocomposites for eco-friendly dielectric applications

This study introduces a novel graphene/bio-based phthalonitrile nanocomposite with ultrahigh dielectric constant and excellent thermal stability. Specifically, a bio-based phthalonitrile resin (CPN) was synthesized by nucleophilic substitution between cardanol and 4-nitrophthalonitrile. Graphene sheets (GNS) were prepared by direct high-speed wet ball-milling exfoliation method. Then, CPN/GNS nanocomposites were prepared by a facile hot-press method and their structures, dielectric and thermal degradation behaviors were systematically discussed. The incorporation of GNS significantly improved the dielectric constant of CPN/GNS nanocomposites by 1096.80% compared with that of phthalonitrile matrix. Thermal decomposition of CPN/GNS nanocomposite happened in the cleavages of weak C-N, C-O and C-C bond, with a stacking mechanism of main chain decomposition and the further carbonization of prior decomposition product by releasing NH3, CO2, CH4, C6H6, C6H5OH and H2O. CPN/GNS nanocomposites showed excellent thermal stabilities and flame reactance, with a Td5% of over 400 ℃, a char yield of 36wt% at 800 ℃ and a limit oxygen index of above 32, respectively. CPN/GNS nanocomposite holds great promise as an environmentally friendly replacement for petroleum-based materials in high-temperature resistant dielectric applications.