Mantis shrimp-inspired functionalized plant fibers to fabricate a soy protein adhesive with high strength and mildew resistance

Soy protein-based adhesives present a promising alternative to petroleum-based adhesives in the wood industry. Nevertheless, their limitations, including insufficient water resistance, low bonding strength, and inadequate mold resistance, constrain their industrial applications. Plant fiber-reinforced composites find extensive applications across various sectors, including furniture, automotive, and aerospace. However, the smooth surfaces of the fibers adversely impact the reinforcement effect. Inspired by the multilayered microscale structure of peacock mantis shrimp chelipeds, this work presents an eco-friendly method to develop hierarchical functionalized kenaf fibers (KF) for reinforcing soybean meal (SM) adhesive. Specifically, ZnO was deposited onto the KF surface to impart micro-nano roughness, thereby enhancing their mechanical interlocking effect with the SM matrix. Bio-based lipoic acid (LA) and limonene (LIM) were employed to create a highly reactive layer on the fiber surface, facilitating the formation of multiple chemical crosslinking structures with the SM matrix. The synergistic mechanical and chemical effects between KF and SM endowed adhesive with improved performance. The wet shear strength of the three-layer plywood prepared with the synthetic adhesive was remarkably increased by 450 % to 1.21 MPa. Additionally, the combined anti-mold effects of ZnO, LA, LIM, and triglyceride amine (TGA) extend the adhesive's storage time to 7 days. This sustainable and eco-friendly design of multilayered bionically functionalized KF offers an efficient approach for the high-value utilization of agroforestry residues, presenting broad application prospects in SM-based adhesives.