Polyurethane modified epoxy vitrimer and its stress relaxation behavior

Abstract Anhydride cured epoxy vitrimers usually exhibit desired mechanical strength but poor toughness and slow transesterification rate. Therefore, the repairing property of the material was restricted. In this paper, polyurethane modified epoxy vitrimer (PU-Epv) was prepared. PU was introduced into the vitrimer system of tetrahydrophthalic anhydride cured epoxy to improve the toughness of the material. Meanwhile, because of the presence of amino ester, the transesterification reaction was promoted and the activation energy of the transesterification was only 33.59 kJ/mol. In the thermal welding experiment, the material could be welded at least five times, and scratches on the surface of the samples could be efficiently repaired within 30 min. The toughness of the material was improved without damaging the strength. Meanwhile, the hard thermosetting epoxy was endowed with excellent repairing properties to increase the service life of the material.