Environmentally friendly high performance homopolymerized epoxy using hyperbranched epoxy as a modifier

A high performance, low cost, and environmentally friendly epoxy is demonstrated for the first time by copolymerizing a small amount of epoxide-terminated hyperbranched polyether (EHBPE) with DGEBA. Unlike typical epoxy systems, which involve large amounts of costly, toxic, and volatile curing agents, homopolymerized epoxy curing systems use only small amounts of catalysts instead of curing agents. However, high performance homopolymerized epoxy has not been reported so far, mainly due to brittleness and somewhat uncontrolled fast curing. Our results show that the addition of small amounts of epoxide-terminated hyperbranched polyether (EHBPE) into DGEBA can lead to simultaneous improvements in strength, toughness, and Tg. At 5 wt% EHBPE loading, the homopolymerized hybrid epoxy shows balanced mechanical performance and is suitable for structural materials. In the first part of the work, the effects of catalyst type and catalyst concentration were optimized using neat DGEBA. In the second part, DGEBA/EHBPE hybrid epoxy systems were cured and tested using those optimized conditions. Compared with neat DGEBA, the addition of 5 wt% EHBPE can increase toughness and tensile strength by 47.6% and 18.8%, respectively; in addition, Tg also increases from 171 to 173 °C.