Advanced Biomimetic Soybean Meal-Based Adhesive with High Strength and Toughness

Abstract

Phenol–amine synergy and mineral reinforcement collectively provide excellent mechanical properties to insect exoskeletons. An advanced soybean meal (SM)-based adhesive, inspired by the insect sclerotization, was developed by integrating tannic acid-functionalized graphene (TA@G), amino-terminated hyperbranched aromatic polyether (HBAP) and SM. TA@G was simultaneously produced and functionalized in a green manner (tannic acid-assisted ball milling), and the active surface of TA@G led to excellent dispersion in the adhesive matrix. HBAP provided numerous reaction sites for the construction of phenol–amine cross-linking network. The dry/wet shear strengths and adhesion work of SM/HBAP/TA@G reached up to 2.59 MPa, 1.29 MPa, and 0.262 J, which were 65.0%, 95.5%, and 66.9% higher than the pure SM (PSM) adhesive, respectively. Compared with PSM, the residual rate of SM/HBAP/TA@G increased to 72.8% from 61.4%, demonstrating enhanced water resistance. The results indicated that more covalent bonds were generated in the adhesive system, which was attributed to the Schiff base reaction and Michael addition between TA@G and HBAP. The formation of massive covalent bonds and the natural waterproof barrier of graphene resulted in a remarkable improvement in SM-based adhesives. Therefore, this simple bionic design strategy provided a novel approach to developing super bioadhesives for the wood industry and could advance the development of tough and strong composites.