Sucrose-tannin-nanosilica hybrid bio-adhesive based on dual dynamic Schiff base and disulfide bonds with enhanced toughness and cohesion

Herein, a high-performance sucrose-tannin bio-based adhesive is developed based on consisting of oxidized sucrose (OS), tannin acid (TA), SiO2 nanoparticles and 2,2'-disulfanediylbis (ethan-1-amine) (DBA) by a facile chemical cross-linking strategy. The OS-TA and OS-TA@SiO2 bio-based adhesives are characterized by XPS, FTIR, and 13C NMR, while the bonding performance is also investigated using shear strength test. Results show that the optimal formulation of OS-TA bio-based adhesive is a 2:1:1 mass ratio for OS: TA: DBA. When the mass fraction of SiO2 is 15 % and the solid content of main components is 50 %, the OS-TA@SiO2 bio-based adhesive has excellent bonding strength. Relative to OS-TA, the wet bonding strength of the OS-TA@SiO2 enhanced from 1.16 MPa to 1.85 MPa, while the dry bonding strength improved from 1.90 MPa to 2.50 MPa. The wood failure rate of the plywood fabricated by using the OS-TA@SiO2 bio-based adhesive reaches 80 %. Therefore, relying on the high flexibility of dynamic disulfide bonds, adding SiO2 nanoparticles into the adhesive system can facilitate greatly the mechanical interlocking effect and make the chemical cross-linking network more compact through the synergistic chemical interactions. This work provides new insights into producing green and renewable bio-based wood adhesives using sucrose and tannin.