Luhao Wang, Weidong Gu, Zhiming Wang
Soy protein (SP) adhesive have garnered significant attention due to their renewability and environmental friendliness. However, their inherent limitations—particularly poor water-resistant bonding strength and pronounced brittleness of cured adhesive layers—severely restrict large-scale applications. This study proposes a synergistic modification strategy utilizing hyperbranched polyester (HBPE). Through esterification reactions, HBPE with varying branching degrees was synthesized, and an innovative approach combining physical blending with epoxy-based chemical crosslinking was developed to achieve multi-level interfacial interactions between HBPE and SP molecules. When incorporating 10 wt% HBPE-3 coupled with 1.5 wt% 1,2,3-tris(glycidyloxy)propane, the modified plywood demonstrated a remarkable wet shear strength of 1.37 MPa (representing a 216 % enhancement over unmodified systems), while the toughness of cured adhesive films reached 0.53 MJ/m³ , demonstrating exceptional toughening effects. The topological structure of HBPE effectively disperses stress concentration, and the dynamic hydrogen-bonding network formed between its terminal hydroxyl groups and protein molecules significantly retards crack propagation. This research not only elucidates the structure-property relationship of hyperbranched molecules in strengthening and toughening SP adhesive but also provides theoretical foundations for developing bio-based adhesive that integrate high mechanical performance with sustainability. The findings exhibit promising application prospects in green packaging and engineered wood product industries. • Synergistic topology-crosslinking resolves SP adhesive's strength-toughness conflict. • Modified SP adhesive achieve 216 % stronger wet adhesion and 0.53 MJ/m³ toughness. • Hyperbranched topology dissipates stress via self-repairing H-bond networks.