Thermally remendable, weldable, and recyclable epoxy network crosslinked with reversible Diels-alder bonds

Abstract

The development of epoxy resins through Diels-Alder crosslinking is challenging: the synthesis is complex, and the mechanical properties are hindered by the brittleness of these bonds. In this work, an epoxy/amine resin with different Diels-Alder crosslinking ratios is manufactured, achieving a simplified route that enhances both sustainability and industrial transferability. The curing temperatures are carefully studied, defining a two-step method (100 °C, 6 h + 60 °C, 12 h) that generates the thermo-reversible resins dispending the use of solvents or intermediate oligomers synthesis. Besides NMR, FTIR, and DSC characterization, the influence of Diels-Alder bonds on mechanical properties is analyzed. The addition of Diels-Alder crosslinking up to a 0.6 ratio of the stoichiometry provides an epoxy with an optimal compromise between recyclability and mechanical properties. Using this ratio, the effect of Diels-Alder crosslinking and disengagement is analyzed through DMTA and microhardness, demonstrating the network reversibility and the feasibility of this techniques to monitor its evolution. • Diels-Alder resins are manufactured without solvents or intermediate prepolymers. • Diels-Alder crosslinked networks show repeatable thermal reversibility. • Diels-Alder reversibility is measured through DMTA and microhardness for first time. • Medium Diels-Alder contents exhibit both reversibility and mechanical properties. • The synthetized resins show self-healing, thermal forming, and recycling capabilities.