A vanillin-derived hardener for recyclable, degradable and self-healable high-performance epoxy vitrimers based on transimination

Development of high-performance and reprocessable thermosets based on sustainable feedstocks is particularly desirable due to the issues of sustainability and resources. Herein, a simple single-step process between vanillin and xylene diamine was used to produce a sustainable vanillin-imine containing hardener (VIH). The VIH-cured epoxy vitrimer exhibits flexural strength (125 MPa) equivalent to commercially available counterparts and significantly higher storage modulus (3448 MPa) at ambient temperature. The hardened vitrimer can be repetitively recycled as like thermoplastics because of the substantial number of reversible imine linkages in the thermoset structures and the recovering of flexural properties near about 100 % even after three reprocessing cycles. Meanwhile, the glass transition temperature (Tg) and thermal properties of the recycled vitrimer maintain nearly identical to those of the pristine vitrimer. Furthermore, the VIH-cured epoxy vitrimer degrades quickly in acidic solution (HCl, 1 M) within 12 h at 50 ᵒC, but it totally resists degradation in other organic solvents over a period of 2 days. Taken together, this study offers a facile procedure for developing a renowned vanillin-imine based hardener for epoxy resins having excellent mechanical properties, recyclability, and degradability.