A novel universal strategy for fabricating soybean protein adhesive with excellent adhesion and anti-mildew performances

Soybean meal (SM) adhesive is a promising alternative to petroleum-based ones. However, the poor water resistance, low bonding strength, and susceptibility to mildew limit its industrial application. Inspired by the micro-nano micelle structure's strengthening mechanism, a facile and green method of synthesizing a high-performance soy protein adhesive by a dual cross-linking strategy was reported. The in-situ self-assembled micelles of benzyldodecyldimethylammonium bromide (BDAB) interacted with protein chains via dynamical bonds, while 1,6-hexanediol diglycidyl ether (HDE) acted as the flexible cross-linker. The BDAB micelles interact with protein chains via non-covalent electrostatic interactions, improving the cross-linking density of the network system and the micelles with numerous amino cations exhibit efficient anti-bacterial properties. The as-obtained adhesive exhibits excellent mechanical properties and stable network structure, showing strong bonding strength and water resistance (2.22 and 1.25 MPa). Especially, the incorporation of HDE and BDAB imparts the modified SM adhesive with excellent antifungal and antibacterial (E. coli and S. aureus) performances, significantly extending the adhesive storage life. Additionally, this work provides a new facile and universal strategy for fabricating formaldehyde-free, environment-friendly, and renewable protein-based adhesives, which is a promising alternative to traditional adhesives in the wood industry.