Barnacle and mussel-inspired of functional silk fibroin to prepare biomass adhesive with ultra-high cold-pressing adhesion

Soy protein adhesives have shown attractive potential across wood-based composite application as replacements for formaldehyde synthetic resins. However, the problems of poor cold-pressing bonding performance, mildew resistance, and flame retardancy are major bottlenecks preventing their widespread industrial use. Herein, a novel dual-bionic soybean meal (SM) adhesive was developed with excellent bonding performance inspired by the strong wet adhesion system of barnacles and mussels. Polydopamine (PDA) adopts for coating the silk fibroin (SF) via a facile in situ polymerization to form a functional SF/PDA (SPA), which acts as a hydrogen bond donor in adhesive system. Benefiting from abundant phenolic hydroxyl groups, multiple hydrogen bond cross-linked networks, and the removal of interfacial water, the adhesive generated a strong cold-pressing adhesion (771.0 kPa) and toughness (1.54 MJ/m 3 ), which respectively increased by 267.1% and 208.0% compared with SM adhesive. The introduction of borate further induces the formation of the dynamic cross-linked network along with supramolecular interactions in adhesive system, which demonstrated strong adhesion to different hydrophilic and hydrophobic substrates in the adhesive. Additionally, borate and phenol hydroxyl groups synergistically improved mildew resistance and flame retardancy in adhesives, which were stored for 20 days without mildew formation and showed combustion suppression behavior during combustion tests. The design of this bionic system offers a novel approach for developing high performance wood adhesives.