A reusable soy protein adhesive with enhanced weather resistance through construction of a cutin-like structure

Enhancing the weather resistance and reprocessability of soy protein-based (SP) adhesives poses a considerable challenge. Here, we report an SP adhesive inspired by animal cutin, featuring dynamic covalent bonds and an organic-inorganic hybrid structure. The soy protein isolate undergoes enzymatic hydrolysis and is then combined with L-cysteine, which is subsequently grafted with glycidol and sodium tetraborate to create disulfide bonds and borate ester bonds, along with mineralized calcium phosphate. This adhesive effectively bonds various substrates, enabling stainless-steel sheets to pull a 1,135 kg car. Additionally, the adhesive exhibits remarkable weather resistance comparable to a phenolic resin (PF) adhesive in an accelerated aging test. It showcases outstanding reusability, surpassing commercial urea-formaldehyde resins and PF adhesives in particleboard reprocessability. Furthermore, the adhesive proves to be mildew resistant, flame retardant, degradable, and eco-friendly. This study signifies a significant advancement in reusable and weather-resistant adhesives derived from plant proteins.