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

• Published in: Polymer (Guilford) 2022-10, Vol.259, p.125334, Article 125334
• Main Authors: Lorero, I., Rodríguez, A., Campo, M., Prolongo, S.G.
• Format: Article
• Language: English
• Subjects: Diels-Alder resin; Recyclable resin; Reprocessable thermosets; Self-healing epoxy; Thermo-reversible crosslinking
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2022.125334

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. [Display omitted] •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.