An eco-friendly adhesive reinforced by cinnamaldehyde to build Schiff Base structure with high strength and superior mold resistance

Conventional soy protein adhesives are limited by weak bonding strength and mold susceptibility. While petrochemical crosslinkers improve performance, their unsustainable nature hinders practical application. Herein, cinnamaldehyde (CA), a plant-derived aldehyde, was integrated into soy protein adhesives via Schiff base formation. With merely 3 wt% CA (relative to soy-protein isolate), the wet and dry shear strengths reached 1.23 MPa (+50%) and 2.47 MPa (+66%), alongside 40-day mold resistance. Structural analyses revealed that CA-induced crosslinking densified the protein network, concurrently enhancing mechanical properties and hydrophobicity. This work presents a simple fabrication method for high-performance bio-based adhesives, surpassing prior bio-adhesives reliant on hybrid synthetic systems.