Allyl-Functionalized Poly(ether sulfone) for BMI Resins: Synergistic Toughening and Thermal Stability Enhancement

Bismaleimide (BMI) resin is characterized by a high degree of cross-linking. However, its application is limited due to inadequate toughness. In this research, a series of thermoplastic reactive poly(arylene ether sulfone) (rPES-PPIs) resins with different propenyl contents were designed and used to toughen the N,N′-(4,4’-diphenylmethane) bismaleimide (BDM)/diallyl bisphenol A (DABPA) system. The study systematically examined the thermal stability, impact resistance, flexural strength, and fracture surface characteristics of both the BDM/DABPA system and the rPES-PPIs/BDM/DABPA blends. The findings indicated that the blend containing 10 phr of rPES-PPIs achieved an unnotched impact strength of 21.23 kJ/m2, which is a 220.21% increase compared to the unmodified system, while the flexural strength reached a maximum increase of 38.80% over the unmodified system. Dynamic mechanical analysis (DMA) also revealed an increase in the glass transition temperature (Tg) of the blends. Additionally, the system exhibited a relatively low curing activation energy of 18.25 kJ/mol, which facilitates the curing process. These results suggest that rPES-PPIs can greatly enhance the toughness of cured BMI resin without compromising thermal properties, and a related toughening mechanism is proposed.