Xylan-tannic acid adhesive combined activated wood interface to construct ultrastrong cross-linking network bonding interface

Biomass adhesives have long been a subject of widespread concern and study due to their cost-effectiveness and minimal environmental impact. In this study, an activated wood surface with epoxy groups (AWI) was created by uniformly applying 3-glycidoxypropyltrimethoxysilane (KH560) onto poplar veneer. Then the aminated xylan-oxidized tannic acid adhesive (2AX-OTA) was prepared based on the Schiff base reaction between the quinone of oxidized tannic acid (OTA) and the amine group of aminated xylan (AX). Eventually, the high-performance bonding interface was co-built by 2AX-OTA and AWI. The dry bonding strength of 2AX-OTA-AWI plywood achieved 3.86 MPa, while the wet bonding strength was measured at 2.41 MPa and 2.15 MPa after immersion in hot (63 °C)/boiling water for 3 h. FT-IR, 13C NMR, and XPS chemical analyses demonstrated that a triple cross-linked network structure of the bonding interface was co-constructed by imine covalent chain bridges and epoxy-amine network. This triple cross-linked network structure plays a crucial role in enhancing water resistance. This study presents a novel approach to designing multi-cross-linked networks for the synthesizing of eco-friendly and high-performance bio-based adhesives.