Constructing epoxy and imidazole dual-functionalized polyurethane@Zinc oxide core-shell crosslinker based on coordination interactions for the preparation of strong, tough, and water-resistant soybean flour adhesives

Abstract

Nanofilling has been regarded as an effective strategy to enhance adhesion performances of soybean flour (SF) adhesives, while it still exists huge challenges to regulate the interfacial properties of nanocomposites toward strong, tough, and water-resistant system. Here, we report on engineering interfacial crosslinking of nanohybrid and SF matrix via core–shell structure design. The reactive core–shell nanohybrid is prepared by epoxy and imidazole dual-functionalized polyurethane shell and zinc oxide (ZnO) nanofiller core under deposition effect of interfacial coordination interactions. Combining reactive epoxy groups and dynamic imidazole/ZnO bonds, a high-performance crosslinking structure with energy dissipation mechanism has been constructed at the interface of ZnO and SF matrix. The structure not only improves the stability of SF adhesive network to resist the external destruction of stress and moisture but also provides dynamic imidazole/metal cation coordination bonds as sacrificial units to facilitate energy dissipation during loading. Results show that the adhesives modified by 5 wt% core–shell nanohybrid present the best performances, in which an 142.0%, 162.3%, and 283.6% increment are observed in dry adhesion strength, wet adhesion strength, and adhesion toughness compared to pristine SF adhesives. Overall, such a high-performance biomass-derived adhesive has great potential for the practical use in wood industry.