Thermally remendable, weldable, and recyclable epoxy network crosslinked with reversible Diels-alder bonds
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.
The authors acknowledge the assistance of Gilberto Del Rosario from the Technological Center Support of University Rey Juan Carlos.
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