Water-Proof, Oil-Proof, and Flame Retardant Composite Based on Grafting Modification of Bagasse Cellulose

Cellulose is a promising biodegradable alternative to nondegradable plastics for packaging. However, its inherent flammability, hydrophilicity, and lipophilicity restrict high-value applications. To overcome these limitations, a multifunctional modifier (PR) was designed by coupling rosin with phytic acid using silane coupling agent. The PR anchors within the cellulose network via dehydration condensation with hydroxyl groups, forming Si–O–C bonds. This process effectively fills structural voids and shields polar groups. Consequently, the PR-modified cellulose composites (PR paper) exhibit exceptional integrated properties: significant flame retardancy (limiting oxygen index of 32.0%), enhanced water resistance (water absorption reduced from 417.7% to 25.4% after 4 h immersion), and superior oil resistance (oil absorption in castor oil decreased from 79.8% to 13.2% after 4 h; kit rating exceeding level 12). Moreover, the PR paper demonstrates outstanding tensile strength (74.0 MPa), significantly surpassing that of commercial plastics like polyethylene, polypropylene, and polystyrene. Remarkably, even after 30 days of storage at 80% relative humidity, the tensile strength remained high at 71.5 MPa. This work presents a novel strategy for designing high-performance, multifunctional cellulose-based packaging materials to replace conventional nondegradable plastics.