Soy Protein Adhesives with Water and Heat Resistant, and Magnetic Properties via Micron/Nanometer Iron-based Particle Modification

The development of soybean meal (SM)-based adhesives with water resistance, heat tolerance, and magnetic-adsorbent functions is critical for expanding their applications as wood adhesives in hot and humid kitchen environments. A key goal is to enable magnetic storage systems such as knife holders and detachable shelves through localized adhesive application. However, the monofunctionality of existing bio-based adhesives limits their practical potential. In this study, micron-sized carbonyl iron powder (CIP) and nanoscale ferrosoferric oxide (Fe₃O₄) were introduced to confer multifunctionality to SM adhesives. Results indicated that the micron-scale dispersion of CIP markedly enhanced the heat resistance and wet-heat stability of SM adhesives through physical barrier effects, while optimizing magnetic attraction efficiency. In contrast, Fe₃O₄ nanoparticles achieved rapid magnetic response at low additive levels due to their high saturation magnetization, though nano-aggregation caused a sharp viscosity increase. Scenario-based validation confirmed that CIP-modified adhesives exhibit excellent structural stability in hot and humid kitchen environments, and they could withstand steam exposure, and retain magnetic adsorption properties.