Self-curing triphenol A-based phthalonitrile resin precursor acts as a flexibilizer and curing agent for phthalonitrile resin

Abstract

Major problems currently limiting the widespread application of phthalonitrile resins are the high precursor melting point and volatility of the curing agent. Herein, a novel self-curing triphenol A-based phthalonitrile resin precursor (TPPA-Ph) was successfully synthesized by reacting α,α,α′-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene (TPPA) with 4-nitrophthalonitrile (NPh) via nucleophilic substitution. The presence of residual phenolic hydroxyl groups in the TPPA-Ph precursor promoted the curing reaction of phthalonitrile resin in the absence of an additional curing reagent. Self-cured TPPA-Ph resins exhibited relatively low melting points (less than 100 °C), high thermal stability, and a wide processing window (116 °C). Furthermore, the TPPA-Ph precursors contained phenolic hydroxyl and cyano groups that can be used as flexibilizers and curing agents to optimize other phthalonitrile resins. Resorcinol-based phthalonitrile resin (DPPH) cured with various amounts of TPPA-Ph possessed excellent thermal and thermo-oxidative stability with a 5% weight loss temperature exceeding 530 °C, T_gs above 380 °C, and a wide processing window and time. Therefore, as a novel precursor and curing agent for phthalonitrile resins, the triphenol A-based phthalonitrile resin is an ideal resin matrix for high-performance composites with broad application prospects in aerospace, shipping, machinery, and other high-tech fields.