Renewable and flexible thermosetting epoxies based on functionalized biorefinery lignin fractions

Epoxy resin materials are spread all over the daily life with their excellent physical, mechanical, and insulating properties. However, the biologically toxic bisphenol A used in epoxy resins formulations has brought a long lasing environmental problem. It is therefore urgent to design and develop more biodegradable alternatives to mitigate the plastic menace. Lignin is an abundant biopolymer with great potential to replace petroleum-based chemicals; however, its valorization is commonly limited because of the heterogeneity. In this regard, a green and simple strategy to fabricate renewable and flexible lignin-based thermosetting epoxies with enhanced mechanical strength has been developed. Specifically, industrial biorefinery lignins are firstly fractioned through a green and simple gradient precipitation and then modified with introduced epoxy groups into the lignin macromolecule under a mild reaction condition. The cross-linking treatment facilities improved interfacial bonding forces between modified lignin fractionations and bisphenol A diglycidyl ether (BADGE) with varied contents (5–15 wt%). The fabricated cured epoxy thermosetting plastic exhibits an enhanced tensile strength (29.7%) and elongation (26.8%) as compared to those of the pure commercial BADGE polymer. We envision that the present strategy provides a new possibility for lignin valorization and design of high-performance flexible thermosetting epoxies for remarkable multifunctionality.