Synergistic effect between amino-functionalized cellulose and bentonite: Enhancement performance and molecular interaction mechanisms of formaldehyde-free peony seed meal-based adhesives.

Peony seed meal (PSM), abundant in protein and carbohydrates, is a promising feedstock for biomass adhesives. Herein, a ternary synergistic modification strategy was adopted, involving inorganic modification with bentonite (BT), organic reinforcement with amino cellulose (AC), and cross-linking and curing with polyamide-amine-epichlorohydrin (PAE), to effectively enhance the water resistance and flame retardancy of the adhesives. The focus was on analyzing the performance enhancement mechanisms and molecular interaction mechanisms of the two functional fillers on PSM-based adhesives. Experimental results indicated that BT, as a layered silicate inorganic filler, can be embedded into or exfoliated by the PSM-PAE-AC matrix. Subsequently, through adsorption, hydrogen bonding, and electrostatic interactions, it reacts with the organic matrix to form a stable organic-inorganic hybrid structure, achieving the synergistic effects of physical reinforcement and flame-retardant modification from inorganic materials. AC, as a natural polymer reinforcing component, relies on its amino active sites and can undergo covalent cross-linking reactions with the carboxyl groups of PSM protein and the epoxy groups of PAE, thereby anchoring the flexible cellulose chains into the adhesive network. This compensates for the insufficient cross-linking density of PSM macromolecules and further strengthens the mechanical properties. The optimal composite adhesive (denoted PP-BT3@AC2) exhibited a viscosity of 34,047 mPa·s, a soaked wet shear strength of 1.82 MPa, and an aged wet bond strength of 1.13 MPa, while cutting raw material costs by approximately 19.5%. This novel composite modification approach will minimize costs and provide a promising direction for the effective use of these adhesives in green materials.