Functionalization and Enhanced Modification of Soy Protein Adhesives: A Review

Adhesive technologies have expanded rapidly and are now widely employed across diverse industrial sectors. However, conventional wood adhesives emit substantial amounts of formaldehyde and rely on fossil-derived feedstocks, posing risks to human health and the environment. Developing sustainable, multi-functional bio-based adhesives has therefore become increasingly important. As a renewable, environmentally friendly, bio-based material, soy protein shows strong potential to replace formaldehyde-based adhesives in plywood. This review summarizes the molecular structure, bonding mechanisms, and recent advances in functional soy protein adhesives. Topics include bonding strength, water resistance, anti-mold and antibacterial performance, flame retardancy, and electromagnetic shielding. The review discusses theoretical foundations and application prospects for green adhesives and outlines opportunities to design and fabricate high-value, multi-functional bio-based composites.