A xylem fiber cell walls-inspired high-performance and multifunctional soy protein isolate adhesive with a double cross-linked strengthening network

Abstract

Soy protein isolate (SPI) adhesive, derived from a green and low-cost sustainable biomass resource, is as an excellent alternative for fossil-based adhesives. However, the weak water-resistant bonding strength and vulnerability to mildew have hindered its practical industrial applications. Herein, inspired by the relationship between the structures and mechanical properties in cell wall of wood xylem fibers, a double cross-linked strengthening network is designed to prepare SPI adhesive with high bonding performance and mildew resistance. Functionalized lignocellulose (TOLC) acting as a skeleton, covalent interaction with SPI enhances the structural stability of the adhesive, enabling it to withstand higher loads, and the water-resistant bonding performance reaches 1.45 ± 0.09 MPa. Sodium lignosulfonate (LS) as a binder can establish a sacrificial bonding network, which provides an effective energy dissipation mechanism for the adhesive and increases the toughness by 379.23 %; meanwhile, as a natural antibacterial agent, it can effectively improve the mildew-resistant performance of SPI adhesive (5 days without mildew). This novel strategy of producing tough, multifunctional and green biomass adhesives by constructing simple double cross-linked strengthening networks provides a practical way to achieve efficient utilization of waste resources and promote sustainable development.