Synergistic effect of recycled PET and hyperbranched ionic liquids for toughening epoxy resin

Improving the toughness of epoxy resins is critical for high-performance applications. In this study from molecular structure design, hyperbranched ionic liquids (HBIL) containing imidazole groups were synthesized through a one-step esterification method. These HBIL were subsequently combined with recycled polyethylene terephthalate (PET) to synergistically enhance the toughness of epoxy resins (EP). The mechanical, thermomechanical, and rheological properties, as well as the curing behavior of the epoxy composites, were systematically evaluated. The addition of HBIL reduced the viscosity and curing temperature of the epoxy composite. The impact strength of the epoxy composites with only 6 phr PET was increased from 6.48 kJ/m 2 to 18.19 kJ/m 2 . Furthermore, the addition of HBIL exhibited a synergistic effect with PET. The epoxy composites added with 6 phr PET and 4 phr HBIL showed an increase in impact strength, elastic modulus, and flexural modulus by 237 %, 28.5 %, and 12.4 %, respectively, and an increase in the glass transition temperature (T g ) by 5.8 °C compared with pure EP. Molecular dynamics (MD) simulations corroborated these experimental results, providing insight into the improved properties. This study introduces an innovative approach to developing epoxy composites with superior performance characteristics.