Development of a Sustainable, Self-Healing, and Recyclable Epoxy Resin Adhesive Based on Soybean Oil

Adhesives are materials that connect two different materials through adhesion and cohesion at their interfaces (references 1-5). They have a wide range of applications in various industries, including aerospace, transportation, electronics, machinery manufacturing, and daily necessities (references 6-11). Thermosetting adhesives, in comparison to thermoplastic adhesives, exhibit excellent bonding properties, chemical resistance, and thermal stability. However, the cross-linked network of thermosetting adhesives prevents them from being reassembled and recycled on demand. To address this limitation, the introduction of dynamic covalent bonds into the cross-linked network has gained significant attention in recent years (references 12-20). This strategy enables thermosetting adhesives to have self-healing ability and recyclability, which is of great importance for on-demand reassembly and recycling. \ Furthermore, the main synthetic materials used in adhesives are derived from non-renewable fossil resources. Given the depletion of global fossil resources, there is a growing need to utilize renewable biomass resources for adhesive preparation (references 21-28). Among the various biomass-based chemical products, soybean oil (SBO) derivatives have received considerable attention due to their abundant availability (references 29, 30). \ In this study, SBO was chosen as the starting polymer substrate and functionalized with epoxy groups. The resulting epoxy resin adhesive exhibited self-healing ability and recyclability, and boronic esters were used in the synthesis process. The chemical structures of epoxidized SBO and the synthesized cross-linker were thoroughly characterized. Subsequently, cross-linked epoxy resins with different compositions were prepared through a reaction between the functional groups. The epoxy resin adhesive was shown to be capable of reassembly at a moderate temperature. \ Overall, the research presented in this paper focuses on the development of a sustainable adhesive based on SBO, which possesses self-healing ability and recyclability.