Cellulosic paper‐based composites enhanced with long‐chain fatty acids: Superb mechanical properties and water resistance

Abstract Cellulosic paper‐based materials are considered to be one of the most potential candidates to replace non‐degradable plastics, but the strong affinity between cellulose and water causes cellulosic paper‐based materials to face the dilemma of poor water resistance and weak wet strength. Herein, a fatty acid‐based hydrophobic modifier (SAT) is constructed by amidation reaction between (3‐aminopropyl)triethoxysilane and stearic acid. The ethoxy groups in the structure of SAT can be covalently crosslinked with the hydroxyl groups of cellulose through hydrolytic condensation, thereby making cellulose paper‐based materials exhibit excellent properties including (1) high mechanical properties (the dry‐state tensile strength has doubled from 22.3 to 46.8 MPa, while the wet‐state tensile strength has surged from 0.47 to 20.0 MPa), (2) long‐term stability (mechanical properties remain almost unchanged after 40 days storage at 80% RH), (3) superb water resistance (soaked in water at 25°C for 1 h, water absorption drops from 247.0% to 56.5%; at 90°C, it falls from 290.5% to 82.9%), (4) eco‐friendly (it can be completely degraded after being buried in soil for 90 days, or it can be recycled and reused). The aforementioned impressive performance positions SAT‐modified cellulose paper as a formidable contender for plastic replacement in packaging applications. Highlights Fatty acid‐based modifier (SAT) can modify cellulose by chemical bond. The low polarity of long‐chain alkanes enables cellulose's hydrophobicity. Covalent crosslinking of SAT with cellulose ensures superb strength SAT paper is an unrivaled combination of degradability and recycling.