Study on toughening and strengthening of bisphenol a epoxy resin with aromatic polyether type hyperbranched epoxy

Abstract Epoxy resins (EPs) have gained widespread industrial adoption due to their exceptional mechanical properties, chemical resistance, and electrical insulation characteristics. However, their inherent brittleness caused by highly cross-linked networks significantly limits their application under impact loading conditions. This study demonstrates a solvent-free strategy for significantly enhancing the toughness of epoxy resins while maintaining their mechanical strength and thermal stability through incorporation of hyperbranched epoxy resins (HPEs). At an optimal 15 wt% loading, the HPE-modified epoxy system exhibits a remarkable 120% improvement in impact strength with simultaneous enhancement of tensile and flexural properties, accompanied by only a minimal 3°C reduction in glass transition temperature. Comprehensive characterization reveals that this exceptional performance stems from three synergistic mechanisms: free volume expansion (from 0.15 nm³ to 0.21 nm³), stress-induced microvoid formation, and optimized crosslinking via terminal group interactions, offering new insights for developing high-performance epoxy composites through sustainable processing.