Curing process optimization and mechanical properties improvement of epoxy resin copolymer modified by epoxy-terminated hyperbranched polyether sulfone

A new epoxy-terminated hyperbranched polyether sulfone (EHPES) has been synthesized by a facile one-step method using 4,4′-dihydroxydiphenylsulfone (monomer A 2 ) and trimethylolpropane triglycidyl ether (monomer B 3 ). The diglycidyl ether of bisphenol-A (DGEBA) was modified by EHPES through the optimal curing process. Compared with the unmodified DGEBA, the copolymer containing 7% EHPES showed the best comprehensive performance. The maximum tensile, flexural, and impact strengths were increased by 9.24%, 10.70%, and 19.38%, respectively. The tensile and flexural moduli were enhanced by 40.74% and 16.20%, respectively. The excellent performances were attributed to the good compatibility of EHPES, increased rigidity, more free volumes, and more “flexible” crosslinking points. Meanwhile, the outstanding tensile property led to the narrow strain concentration region of DGEBA/7% EHPES copolymer through the observation of digital image correlation (DIC) system. The EHPES modified epoxy resin can also be potentially used for carbon fiber reinforced composites in some advanced applications.