High Strength and Toughness Epoxy Nanocomposites Reinforced With Epoxy‐Terminated Hyperbranched Polymer

ABSTRACT Epoxy composites reinforced and toughened with an epoxy‐terminated hyperbranched polymer (ETHP) were successfully synthesized. The ETHP was derived from a bio‐based epoxy resin, and its structure was confirmed using nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The influence of ETHP content on the mechanical and thermophysical properties of epoxy composites was systematically investigated. The mechanical properties exhibited an initial increase followed by a decline with increasing ETHP loading. The 7.5 wt% ETHP/epoxy composite demonstrated optimal mechanical performance, with a tensile strength of 91.7 MPa, elongation at break of 6.7%, and flexural strength of 145 MPa. Compared to the cured epoxy polymer, they represented increases of 30.6%, 34.3%, and 38.1%, respectively. The glass transition temperature (Tg) of the ETHP/epoxy composites also increases first and then decreases. A maximum Tg is obtained when ETHP content is 5 wt%. It shifted to 174.9°C from 158.6°C of pure epoxy polymer. The excellent overall performance of ETHP/epoxy composites not only broadens the potential applications of epoxy resins but also provides a novel approach for toughening other resin systems.