Imine-Containing Epoxy Vitrimer Cured by Active Ester: Properties and Theoretical Analysis

Abstract

Vitrimers are polymers possessing a covalent adaptable network (CANs) that can undergo a topological structural transformation under specific conditions, enabling material reprocessing. In this study, an active ester hardener containing imine bonds (TAI) was synthesized, and subsequently, epoxy resin with CANs (epoxy vitrimer, DGEBA/TAI) was prepared, which exhibited excellent thermal stability (initial degradation temperature of 364 °C and char yield at 800 °C of 30%), low water absorption (0.25 wt %), and good dielectric properties (dielectric constant of 3.37 and dielectric loss of 0.013). A comparative scratch healing test between the epoxy vitrimer and conventional epoxy resin showed that the hard vitrimer could not demonstrate self-healing ability and that scratch healing was derived from deformation recovery. The performance of such hard vitrimers should focus on recycling and reprocessing rather than a self-healing capability. Thus, the resin could be effectively recycled and reused by a hot pressing or solvent method, resulting in recycled resins with good tensile strength (70 MPa for hot-press welding and 58 MPa for solvent recycling) compared to the originals (69 MPa). In addition, the vitrimer materials allow shape reconfiguration through a network structure transformation, and an alternative analytical method was proposed to obtain the relaxation time of the vitrimer by fitting the equation of the stress relaxation curve, which could mitigate some of the interferences and provide a method for data reliability verification of the viscoelastic properties of the vitrimer.