Catalyst-free epoxy vitrimers from rosin: Highly mechanical performance, fast self-healing, and facile recycling

Recyclable epoxy vitrimers from biomass are significant for sustainable industrial development. However, the reprocessing of epoxy vitrimers comes at the cost of their mechanical properties and thermal stability and it is a challenge to obtain epoxy vitrimers with facile recycling ability, high mechanical properties and thermal stability, simultaneously. Present work offers a way to prepare the high-performance epoxy vitrimers with dual dynamic beta-hydroxy ester bonds and boroxines from rosin derived glycidyl ester epoxy resin and 3-aminobenzeneboronic acid. The presence of tertiary amines and dynamic beta-hydroxy ester bonds, as well as dynamic boroxines in the network accounts for the effective malleable behavior without the assistance of a catalyst. The resultant rosin-based epoxy vitrimers possess the Tg around -83.2 degrees C with the Ts above 170 degrees C, the E ' of 36.1 MPa and the tensile strength around -60.9 MPa comparable to commercial BPA epoxies, which attribute to the rigid rosin structure and high crosslink degree. The integrated self-healing of scratches after heating at 120 degrees C for 30 min is achieved, and the self-healing efficiency in terms of Young's modulus is 97.8 %. The welding efficiency of tensile strength reaches 94.4 % after welding treatment at 120 degrees C for 30 min. The reprocessed samples with the first generation obtained from hot press (8 MPa) at 140 degrees C for 3.5 h exhibit the tensile strength of 54.9 MPa. A close-loop recycling of rosin-based epoxy vitrimers was demonstrated, the retention ratio the recycled sample in terms of tensile strength of 82.6 %. Therefore, the REB networks with unique properties are desired alternatives to commercial epoxy resin and show the potential applications in transportation, aerospace and construction materials.