A vanillin-based vitrimer matrix for recyclable and sustainable carbon fibre-reinforced composites

Recently, economic and environmental concerns over the accumulation of end-of-life carbon fibre composite wastes have led to the extensive search for sustainable materials offering a lower environmental impact. Lately, vitrimers – a modern class of covalent adaptable networks – appeared as an innovative polymer, bridging the gap between thermoplastics and thermosets. However, the synthesis of vitrimers often involves the consumption of petrochemicals, increasing the carbon footprint and conflicts with the sustainability regulations in the “green” polymer industry. Herein, a biobased vitrimer from vanillin was successfully prepared via a catalyst-free imine condensation reaction. The Fourier Transform Infrared absorption peak at 1644 cm −1 represents the imine bond in the vanillin-based vitrimer (v-vitrimer). The thermal gravimetric analysis of the v-vitrimer shows good thermal stability (T d5% ∼ 240 °C) compared to the control polyimine vitrimer (285 °C) and the industry-grade vitrimer (Vitrimax) (299 °C). Differential scanning calorimetry (DSC) shows that v-vitrimer exhibits a higher glass transition temperature (85 °C) than that obtained from the control vitrimer (75 °C) and Vitrimax vitrimer (55 °C). Dynamic mechanical analysis shows that v-vitrimer exhibits rapid stress relaxation, reaching a relaxation time (37% relaxation) within 30 s. Owing to the fast stress relaxation at elevated temperatures, v-vitrimer can be thermally reprocessed by hot-press at their glass transition temperature (85 °C). Moreover, v-vitrimer can be chemically recycled via both acid hydrolysis and transamination thanks to reversible imine bonds in the v-vitrimer system. This work proposed a promising procedure to synthesise vitrimer from biobased materials with reprocessability and recyclability. • Vanillin-based vitrimer was successfully synthesised by a catalyst-free imine condensation at room temperature. • The vitrimer shows a moderate glass transition temperature T g at 85 °C. • Low crosslink density (2671 mol m −3 ) enables the vitrimer to exhibit fast stress relaxation. • Reprocessed vitrimers maintain their chemical structure and thermal properties. • Vitrimer composites can be fully recycled under a neat amine at room temperature.