Improving coating and prepressing performance of soy protein-based adhesive by constructing a dual-bionic topological structure

Abstract

Developing efficient and sustainable green adhesives to replace aldehyde-based adhesives has become an important strategy to address fossil resources depletion, environmental pollution, and clean production. Soy protein is a raw material-rich, renewable biomass material that can be used to prepare environmental-friendly adhesives. However, the weak interfacial adhesion of soy protein-based (SP) adhesives leads to poor coating and prepressing properties, thus limiting the large-scale application of the SP adhesives. In this study, a bionic "bond-stitch" molecular topology was designed and constructed in SP matrix to prepare a strong multifunctional adhesive. Inspiring by the strong adhesion of mussel, urushiol (U) with natural catechol structure and acrylamide were polymerized in situ into poly(urushiol-co-acrylamide) (PUAM) as stitching polymer, which was entangled with the SP network to form a bond-stitch molecular topology. The hydroxyapatite was used to construct an organic-inorganic hybridization in the SP matrix mimicking the tough cohesion of oysters. The resultant dual-bionic SP adhesive exhibited excellent coating performance, prepressing intensity (0.45 MPa), flame retardancy (the limiting oxygen index was 39.4%), mildew resistance (10 d), low volatile organic compounds release, and good antibacterial activity (the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans were 89.55%, 78.59%, and 99.91%, respectively.). The wet shear strength of the prepared SP adhesive was increased from 0.35 MPa to 1.17 MPa. This study provides a new strategy for the design and preparation of high-performance, sustainable, low-carbon footprint bio-adhesives and composites.