Bioinspired mineral–organic hybridization strategy to produce a green high performance soybean meal based adhesive

Soybean meal-based adhesives have been applied in many fields due to the abundant source and eco-friendly property. However, the preparation of high-performance soybean meal-based adhesives was still challenging. Inspired by the mineral-organic hybridization structure of nacre, hydroxyapatite and tannic acid complex was used as rigid nanofiller and cross-linker to improve the properties of soybean meal adhesives. Tannic acid was bonded with hydroxyapatite through coordination bonds and could promote the hydrogen bond between soybean meal and hydroxyapatite. Owing to enhanced crosslinking density, the wet shear strength of the adhesive increased from 0.66 to 1.70 MPa and the toughness was also clearly improved. The residual ratio increased to 85.8% and the moisture absorption reduced to 16.5%, indicating better water resistance. The high chemical reactivity of catechol and pyrogallol groups on tannic acid endowed the adhesive with better mildew resistance and antibacterial ability. Besides, the addition of hydroxyapatite and tannic acid complex could restrict the heat transfer and quench the oxygen free radicals, which enhanced the flame resistance of the adhesives. This study provided a new strategy for the preparation of green soybean meal-based adhesives with high performance.