Catalyst-free, environmental stable epoxy vitrimer based on a trifunctional amine with adjustable reactivity and its repairable composites

The development of reprocessable, repairable and high environmental stable epoxy vitrimers without the use of any external catalysts is attractive for practical applications. Herein, the reaction of a kind of trifunctional amine based on B–Ncoordinated boronic ester (DBPM) to conventional epoxy compounds was studied. Through precise adjusting the crosslinking degree of the epoxy, epoxy vitrimers with good thermal stability, high mechanical strength, and remarkable network reconstruction capacity were obtained. The obtained epoxy vitrimers (AE-DB) exhibit bending strength as high as 59 MPa and can be efficiently healed after being fractured four times. The inherit high reversibility of the boronic ester structure enables the flexural strength of the glass fiber/AE-DB composites retains 74 % of their original value after four breaking/healing cycles, and the glass fiber can be facilely recycled from the composites. Notably, owing to the B–N coordinated structure and finely tuned crosslinking structure, the dynamically crosslinked AE-DB resin possesses good water and humidity resistance, and it can be still efficiently repaired after immersion in water for 48 h. This study will provide useful reference for developing a new type of epoxy vitrimer as matrix for repairable composites.