Sustainable alternative for bisphenol A epoxy resin high-performance and recyclable lignin-based epoxy vitrimers

Epoxy vitrimers based on dynamic covalent bond chemistry have been developed in recent years as they can solve the problem of recycling and reuse for traditional thermosetting materials. Lignin as an aromatic raw material has recently used to partially replace commercial diglycidyl ether bisphenol A (DGEBA) in the epoxy vitrimers, however, it is difficult to achieve high lignin replacement rate, excellent mechanical property and reprocessability in a facile method at the same time. In this work, high mechanical strength and lignin replacement rate of lignin-based vitrimers were successfully synthesized by gradually replacing DGEBA with glycidyl ether of lignin. The mechanical properties of the lignin-based epoxy vitrimers can be tuned by different ratios of glycidyl ether of lignin and DGEBA, the Young’s modulus and tensile strength of those vitrimers can reach up to 2.00 GPa and 46.8 MPa, respectively. It's worth noting that the tensile strength and elongation at break were 39.5 MPa and 5.81 % when the lignin replacement rate was 100 %. All the lignin-based epoxy vitrimers exhibit excellent self-healing, reprocessing and shape memory property. The crack widths of the vitrimers were repaired over 80 % in just 5 min at 160 ℃, the tensile strength can reach up to 97 % healing efficiency after being hot reprocessed. The great properties of lignin-based epoxy vitrimers indicate that they can be used as renewable alternatives for bisphenol A epoxy vitrimers.