Thermally activated multiple self-healing diels-alder epoxy system

The introduction of thermo-reversible covalent bonds in the molecular network is a recent approach to prepare self-healing polymers upon a suitable thermal trigger. Among reversible reactions, Diels-Alder (D-A) cycloaddition is an ideal candidate for the synthesis of mendable polymers, such as epoxy resins, with improved operative life. The D-A adduct, referred to as 2Ph2Epo, was synthetized and crosslinked with a mixture of aliphatic and aromatic amines. The resin formulation aimed at reaching a compromise between the mending capability of cured material and its dimensional stability at high temperatures, required during healing cycles. The latter result was achieved by mixing the adduct with commercial DGEBA monomer. The ability of the adduct to give direct D-A and reverse D-A (r D-A) has been verified by FT-IR and rheological analysis on 2Ph2Epo. Mechanical tests were performed for assessing the self-healing efficiency of the crosslinked 2Ph2Epo/DGEBA system. The multiple healing feature of the system was proved. The hybrid epoxy resin is able to recover damages, still exhibiting the pristine stiffness, while the strength of the system decreases after progressing healing cycles.