Development of Bio-Based Epoxy Thermosetting Materials Based on Imine Bonds

The development of bio-based epoxy thermosetting materials represents a promising step towards sustainable and high-performance polymer chemistry. Conventional epoxy resins, primarily derived from bisphenol A (BPA), raise significant environmental and health concerns due to their toxicity and lack of recyclability. In response to these issues, this study focuses on the synthesis of epoxy thermosetting materials using Schiff base chemistry, incorporating lignin-derived vanillin and syringaldehyde, along with the naturally occurring, non-toxic flavonoid naringenin. These bio-based monomers were polymerized through three distinct strategies: self-polymerization, initiator-assisted polymerization, and TGEN-copolymerization. The synthesized thermosets exhibited outstanding thermal properties, with glass transition temperatures ranging from 138 to 249°C, demonstrating excellent stability under high-temperature conditions. Furthermore, these materials showed remarkable recyclability through transimination reactions, allowing the recovery and reprocessing of the polymer network without significant loss of performance. Their high flame resistance, with a limiting oxygen index (LOI) of 33–37%, further enhances their potential for applications in industries where fire safety is critical. The combination of thermal stability, mechanical strength, and chemical recyclability highlights the potential of these bio-based epoxy resins as a viable alternative to petroleum-derived thermosets in advanced technological applications such as aerospace, automotive, and construction.