Novel reactive phenolphthalein‐based polyether ketone, its scale‐up preparation and high‐efficiency toughening in epoxy resin modification

Abstract Incorporating reactive groups that can participate in epoxy cross‐linking into traditional thermoplastic toughening agents enhances the interfacial compatibility between thermoplastic and thermosetting resins, thereby improving the impact toughness of the system. In this study, hydroxyl end groups were integrated into phenolphthalein polyether ketone (PEKC) molecular chains to engage in the cross‐linking reaction during epoxy curing, significantly enhancing the toughening effect on the epoxy system. The results indicate that hydroxyl‐terminated phenolphthalein polyether ketone (PEKC‐OH) of various molecular weights can enhance the impact strength of the epoxy system (E51/MTHPA). Among these, the PEKC‐OH‐2 resin exhibited the optimal toughening effect at an addition level of 10 phr, increasing the impact strength from 11.85 to 23.46 kJ/m 2 , representing a 98% improvement, without compromising the operating temperature and mechanical properties of the epoxy system. Additionally, kilogram‐scale toughening agent resins were produced through scale‐up experiments of PEKC‐OH‐2 in a 50‐L polymerization reactor, validating its applicability for industrial epoxy toughening. In summary, the PEKC‐OH synthesized in this study serves as an efficient reactive thermoplastic toughening agent, offering ease of preparation, industrial producibility, and considerable application potential. Highlights Novel hydroxyl‐terminated phenolphthalein polyether ketone (PEKC‐OH). Reactive hydroxyl end groups improved compatibility with epoxy resin. PEKC‐OH formed an interpenetrating network with epoxy, boosting impact toughness. Scaled‐up of PEKC‐OH‐2 in a 50‐L reactor for industrial production. PEKC‐OH is feasible to prepare and has great application prospect.