Design of high performance multifunctional protein adhesive by incorporating of polydopamine-functionalized boron nitride and carboxymethylated lignin

Soybean protein isolate (SPI), a promising biomass resource to substitute petroleum-based chemicals, has been widely employed to prepare biobased board adhesives due to abundant availability, environmental compatibility, and rich functionality. However, pure SPI-based adhesives exhibit poor mechanical properties and high water absorption, which limit their practical application. In this work, dopamine-functionalized hexagonal boron nitride (PDA-BN) and carboxymethylated lignin (CAL) were introduced to serve as fillers and reinforcers to cross-link with SPI. The wet and dry shear strength of resultant adhesive increased by 172% and 64.3% to 1.58 MPa and 2.07 MPa, respectively, compared to the pure SPI-based adhesive, surpassing the performance of a vast of different SPI-based adhesives. The SPI-based adhesive also demonstrated enhanced water resistance, flame retardancy, and mildew resistance. These improvements can be attributed to the dense covalent and noncovalent intermolecular interactions and improved compatibility between PDA-BN and the SPI matrix.