A hair fiber inspired bio-based adhesive with high bonding strength and mildew tolerance

Soybean protein (SP)-based adhesives present low adhesive strength, poor water resistance and low mildew resistance, which generally limit their practical industrial applications. Inspired by the interesting phenomenon that the strength of hair fiber was affected by the breaking and reuniting of disulfide bonds during perming, in this study, a new biomimetic strategy was proposed to construct a soybean meal (SM)-disulfide bonds-chitosan (CS) structure to achieve enhanced adhesive strength, improved water resistance and higher mold resistance. The introduction of sulfhydryl chitosan (CSSH) with high sulfhydryl content provided sufficient reaction sites, endowing the resultant high-strength and mold resistant bio-based adhesive with increased crosslinking density and numerous hydrogen bonds. The dry shear strength and the wet shear strength for 3 h soaking at 63 °C of SM-CSSH was improved by 61.31% and 365.6% to 2.71 MPa and 1.49 MPa, respectively. The increase in residual rate and decrease in moisture absorption of adhesive illustrated the excellent water resistance of the material. More importantly, the antibacterial property of chitosan prolonged the storage time of the adhesive, which benefits to its industrial applicability. This study provided a new biomimetic strategy to prepare high-strength adhesives from agricultural and fishery wastes, exploring for green and sustainable development concept.