Synergistic Enhancement and Functionalization of Soybean Meal Adhesives through In Situ Regenerated Cellulose Nanofiber-Anchored Kenaf Fibers and Supramolecular Self-Assembled Melamine-Phytate Nanosheets

Although soybean meal (SM) adhesive holds promising prospects as an eco-friendly alternative to formaldehyde-based resins, its practical application remains constrained by issues such as poor bonding strength and inadequate water resistance. In this work, a multifunctional SM-based adhesive (SMG/CKF/MP), featuring high bonding strength, water resistance, flame retardancy, and antimildew, was successfully fabricated via the integration of in situ regenerated cellulose nanofiber-anchored kenaf fibers (CKF) and supramolecular self-assembled melamine-phytate nanoplates (MP). When subjected to external forces, CKF with its surface-loaded nanofiber structure effectively promoted interfacial bonding with the SM matrix by generating efficient mechanical interlocking and extensive hydrogen bonding interactions. Meanwhile, the two-dimensional rigid architecture of MP bridged soybean protein chains and CKF through electrostatic and hydrogen bonding interactions, enhancing load transfer and energy dissipation. As expected, the wet shear strength and fracture toughness of the plywood prepared by the modified SMG/CKF/0.5MP adhesive increased to 1.15 MPa and 618 mJ, which are about 379% and 2587% higher than those of the unmodified SM adhesive. Meanwhile, the SMG/CKF/MP adhesive exhibited superior flame retardancy and antimildew properties. This study provides a green and low-cost preparation strategy for high-performance biomass adhesives, further expanding the development and application of biomass adhesives.