It is of great importance to develop epoxy vitrimers with the combination of high performance and versatile recyclability. Herein, two imine-containing hardeners were synthesized from bio-based vanillin and petroleum-based p-hydroxy benzaldehyde. The epoxy resins cured by these two hardeners show high T g (>120 °C), tensile strength (>60 MPa), Young's modulus (>2500 MPa), and good solvent resistance. Owing to the incorporation of imine dynamic covalent bond, the cured epoxy resins are reprocessable and degradable. Notably, the chemical degradation products can be reused to prepare new epoxy resins, thus achieving a closed-loop recycling process. Both the reprocessed and chemically recycled epoxy resins exhibit high-percentage retention of thermal and mechanical properties. Finally, this study demonstrates that the epoxy resin cured by the vanillin-based hardener shows comparable thermal, mechanical, and recycling properties compared with the epoxy resin cured by the petroleumbased counterpart.

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Thermoset resins generally lack the ability to be welded or reprocessed like thermoplastics because of their cross‐links. Increasing use of fiber‐reinforced composites in large structures, such as rail and aircraft parts, as well as wind blades, calls for better ways to repair damages and be compliant with recycling and environmental regulations. In this article, an epoxy resin containing disulfide bonds was prepared and characterized by Fourier transform infrared, 1H‐NMR, and 13C‐NMR. The dynamic nature of the disulfide bonds allowed the cured epoxy resin to be welded like thermoplastics, and the welded joints had strength that matched the resin's cohesive strength. It could also be reprocessed with 90% tensile strength retention after three reprocessing cycles, allowing the parts to be repaired instead of being replaced. In addition, the cured resin was chemically degradable in a thiol‐based solvent, allowing it to be recycled in closed‐loop processes. Moreover, the cured epoxy resin showed a glass transition temperature of 116°C, demonstrating its potential for advanced composite applications.

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