A Sustainable Bio‐Based Epoxy Thermoset as a High‐Performance Alternative to BPA‐Based Resins

ABSTRACT Epoxy resins are indispensable to structural composites, coatings, and adhesives. However, conventional bisphenol A (BPA)‐based epoxy resins are limited by toxicity concerns, intrinsic brittleness, poor end‐of‐life recyclability, and a high carbon footprint. Here, a rigid–flexible bio‐based network design is developed by coupling epoxidized soybean oil (ESO), lignin, and malic acid through maleic anhydride bridging, which simultaneously improves component compatibility and introduces dynamic ester linkages for pH‐responsive degradation. The resulting thermoset achieved an unusual combination of strength, ductility, and environmental resilience, delivering 22.08 MPa shear strength as a structural adhesive and 31 4.57 MPa tensile strength in glass‐fabric composites, together with an ≈250% increase in flexural strain relative to the BPA epoxy. It further maintains robust performance after exposure to chemically aggressive media and extreme temperatures ranging from −196 to 200°C. Life cycle assessment (LCA) and techno‐economic analysis (TEA) confirmed its environmental friendliness and competitive cost‑effectiveness. This work demonstrates a sustainable design for high‑performance thermoset, offering a viable sustainable alternative for applications such as structural adhesives and wind‑turbine composites, thereby accelerating the transition toward a circular bio‑economy.