Renewable Coumarin-Derived Network as a Toughening Structure for Petroleum-Based Epoxy Resins

A double-network strategy to toughen epoxy resin system is presented herein. Dihydrocoumarin (DHC), a hexatomic compound extracted from tonka bean, is used as the building block for the construction of the first network, and the diglycidyl ether of bisphenol A epoxy matrix is used as the second network. The resultant double network demonstrates a single glass transition and good compatibility between these two networks. Owing to the firm interfacial adhesion between networks and the effective stress transfer as well as external energy absorption derived from the DHC-based network, the double-network-based epoxy resin shows a significant toughness improvement without trade-offs in the tensile strength and elongation at break. The finding in this study provides a promising way to overcome the intrinsic brittleness of commercial epoxy resin via the utilization of renewable DHC for the construction of a novel double network.