Preparation, characterization, and performance of reactive phenolphthalein poly(aryl ether sulfone) tougheners highly compatible with epoxy resin

Aiming at the problem of phase separation between thermoplastic toughener and epoxy after curing, which leads to the reduction of mechanical properties, in this paper we improve the compatibility of the two phases by introducing reactive groups into the molecular chain of thermoplastic resins, thus improving the impact strength of the epoxy system. Phenolphthalein polyether sulfone (C-PESC) with designable and controllable carboxyl group content was prepared via SN 2 nucleophilic substitution copolymerization. Further C-PESC was evaluated for epoxy toughening, and the effects of carboxyl group content of C-PESC on mechanical properties and thermal stability of the resin system were investigated. The results show that C-PESC resin has good compatibility with E51 epoxy resin. Carboxyl group accelerates the dissolution rate of thermoplastic resins in epoxy and also participates in the curing reaction with epoxy to enhance the interfacial bonding ability between the toughening component and the matrix resin. The reactive toughener C-PESC can not only improve the impact properties of E51 epoxy, but also maintain the high T g and thermal properties of the resin system. Among them, the addition of 5 PHR of C-PESC3 increased the impact strength of the modified resin by 45%, with uniform fracture surface and tough fracture shape.