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Epoxy (EP) vitrimers are considered the ideal substitutions for conventional thermosetting EPs due to their sustainability. However, for industrial applications, the high strength of vitrimers usually contradicts a high recovery ratio. Herein, we synthesized a series of hardeners containing imine bonds via the reaction of a Schiff base between p -phenylenediamine and vanillin, which were then used to prepare EP vitrimers with various imine bond contents according to stoichiometric ratios. EP vitrimers exhibited a tensile strength of at least 54.9 MPa, and all of the vitrimers can be self-healed and reprocessed at high temperatures. Moreover, with the increase of imine bond content, the activation energy ( E a ) and topology freezing transition temperature ( T v ) of the vitrimers decreased, leading to the improved recovery ratio. The optimal comprehensive properties of the EP vitrimer were achieved for EPV-VP-1.5, with a T g of 132.7 °C, a tensile strength of 82.4 MPa, an elongation at break of 5.5%, and a recovery ratio of 91.5% in the first recycling process. Even after recycling three times, a tensile strength of 62.8 MPa was retained. Moreover, all EP vitrimers can be dissolved completely in 0.5 mol L –1 HCl with DMF solutions at 50 °C after 2 days. Therefore, this work demonstrated a strategy to prepare EP vitrimers with both high strength and a high recovery ratio.
Luo et al. (Thu,) studied this question.