Synthesis of Thermoplastic Phenolphthalein Polyether Sulfone and Its Toughening Research in Epoxy Resin and CFRP

Abstract This work investigated the thermo‐mechanical properties of phenolphthalein polyether sulfone (PES‐C) in toughening epoxy resin and CFRP, along with an analysis of toughening mechanisms. PES‐C, a high‐performance resin with a high glass transition temperature and modulus due to its specific cardo ring structure and sulfone group, was synthesized and incorporated into epoxy resin through physical blending to enhance the mechanical properties of the epoxy matrix. With the addition of 15 phr PES‐C the impact strength increased by 72.71 %, and SEM analysis revealed a bi‐continuous and island coexistence structure, with the toughening mechanism attributed to reaction‐induced phase separation. The thermal performance was improved, with T d5% and T g increased using TGA and DMA analyses. Additionally, PES‐C non‐woven fabric was fabricated via electrospinning and integrated into EP/CF prepregs for interlayer toughening. G I, C, and G II, C of CFRP increased by 37.5 % and 134 %, respectively. The toughening mechanism could be attributed to the enhanced interlayer bonding strength provided by the PES‐C non‐woven fabric, which effectively mitigated fiber debonding. These two approaches demonstrated that PES‐C exhibited excellent toughening effects on both epoxy resin and CFRP, offering significant application potential in the aerospace field.