Self-healing dual cured polyurethane elastomeric coatings prepared by orthogonal reactions

Highlighting enhanced properties of polymers provided by dual-curing, self-healing coatings have been prepared via Diels-Alder and urethane formation reactions. These two orthogonal reactions were performed by functionalization of hydroxyl-terminated polybutadiene with furan dangling groups through thiol-ene reaction. In other words, the presence of the furan groups along with the terminal hydroxyl groups of HTPB made it possible to undergo in both urethane formation and Diels-Alder cycloaddition reactions, simultaneously. Remarking the effect of the Diels-Alder reaction on the self-healing ability of the samples, the proper bismaleimide compound has been selected by the DSC test. Moreover, a novel tetrafuran compound has been synthesized as crosslinking agent to improve the mechanical strength of the prepared coating and their self-healing properties. Evaluating the microscopic and macroscopic scales showed that the prepared coatings exhibited good healing properties as well as their mechanical properties. The microscopic imaging confirmed that the created scratches vanished after the healing process in all samples. Furthermore, the healed samples were displayed at least 50 % of their initial strength in the tensile test. Additionally, the results revealed that the coatings mechanical strength was reinforced from 1.34 to 2.30 MPa by introducing tetrafuran crosslinking agent in their matrix.