A Furan-Derived Self-Initiating Hardener for Renewable High-Performance Epoxy Thermosets: Synthesis, Curing Mechanism, and Structure−Property Relationships

Abstract The development of high-performance thermosets from renewable resources is essential to reducing the environmental impact of polymeric materials. Herein, we report a new family of epoxy thermosets designed to be entirely obtainable from renewable feedstocks cured with a furan-derived hardener (F-MA) synthesized through a catalyst-free modified Diels−Alder reaction. A unique feature of these systems is their ability to undergo initiator-free curing enabled by the intrinsic reactivity of the F-MA hardener, which eliminates the need for external initiators or catalysts. The curing mechanism and network formation were investigated by FTIR, 1H-NMR, and DSC, revealing a multistep polymerization process. The resulting thermosets exhibited outstanding thermomechanical performance, with storage moduli up to 3.2 GPa and α-transition temperatures approaching 197 °C. Excellent thermal stability was achieved, with temperatures at 5% weight loss reaching 377 °C. In addition, the materials displayed inherent flame-retardant behavior, achieving limiting oxygen index (LOI) values up to 34% without the use of flame-retardant additives. Combining a theoretical 100% renewable-feedstock content, initiator-free curing, high thermal resistance, and intrinsic fire safety, these thermosets represent a sustainable alternative to conventional epoxy resins for demanding structural and high-temperature applications.