Developments in Bio-Based Soy Protein Adhesives: A Review

Recently, soy protein has attracted extensive attention from wood industries and consumers in the production of wood adhesives as it is non-toxic, biodegradable, low cost, and easy to process. There are a variety of reactive groups namely -OH, -NH2, -COOH, and -SH, in protein molecules, which offer possibilities for protein denaturation, chemical modification, and increased ionic interactions. The research in protein denaturation, crosslinking modification, biomimetic modification, and organic-inorganic hybrid formulation not only focuses on enhancing the mechanical properties and tolerance to water of the adhesives but also considers its toughness, mildew resistance, and flame retardancy to further optimize the performances of the adhesives. In this paper, soy protein chemical composition, soy protein denaturation, and reinforced modification are discussed to understand these methods and further develop into a multifunctional soy protein-based adhesive. Given the potential of bio-based adhesives, these modification methods not only provide the theoretical basis for its development at full scale, but also the possibility for the multifunctional applications of bio-based adhesives.