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 & PRIME;-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.