Excellent strength and toughness and multifunctional protein-based adhesive produced by polyether block sulfuretted polyamidoamine-epichlorohydrin via a dual-crosslinking strategy

Developing high-temperature soy-protein meal (HSM)-based adhesives equipped with excellent bonding strength, superb toughness, and versatility is challengeable due to their inherent high hydrophilicity and agglomeration. Though conventional chemical modifications can enhance the bonding strengths of HSM-based adhesives, few strategies can achieve simultaneous enhancement and toughening. To achieve this target, the polyether block sulfuretted polyamidoamine-epichlorohydrin (SPE-PEDE) was innovatively self-prepared. The SPE-PEDE can not only form a stiff chemical bond crosslinking network through the active azetidinium groups and disulfide bonds in sulfuretted polyamidoamine-epichlorohydrin (SPE) segment, but also can provide a plasticizer phase (PEDE) which can trigger dynamic hydrogen bonding and promote stress transfer among the adhesive system. Thus, forming an efficient dual-network strengthening and toughening system inside adhesives. The improved toughness of the HSM/SPE-PEDE15% sample prepared herein achieved a 306.31% compared to the neat sample, and it bonded plywood obtained a dry bonding strength of 2.90 MPa, a wet bonding strength of 1.11 MPa, and a pre-pressing bonding strength of 760 kPa, which were 82.39%, 258.06%, and 208.94%, respectively higher than the HSM sample. Besides, the modified adhesives also exhibit high solid contents, low moisture absorption, excellent mildew resistance, and antibacterial activity, thus showing the potential to promote the industrial production of HSM-based adhesives.