Multifunctional films of cellulose nanocrystal reinforced polyvinyl alcohol through citric acid crosslinking for efficient freshness.

Polyvinyl alcohol (PVA) is a promising biodegradable packaging material, but its widespread application is severely limited by several drawbacks, including insufficient strength, poor water resistance, weak UV shielding properties, and poor preservation ability. In this study, PVA/cellulose nanocrystals/citric acid (PVA/CNC/CA) composites were fabricated using a solution blending combined with thermal crosslinking process. The effects of CNC content and CA amount on the structure and properties of the composites were systematically investigated. The crosslinked PVA composites exhibited an enhancement in tensile properties compared to the neat PVA, with tensile strength reaching 27.2-31.2 MPa and elastic modulus ranging from 153.6 to 328.8 MPa, with almost no compromise in elongation at break. Moreover, after 24 h of immersion in water, the PVA/CNC/CA composite experienced swelling, and the UV transmittance at 300 nm decreased to below 27%. More importantly, after 28 days of storage in the PVA/CNC/CA film, the surface of the cherry tomatoes remained smooth, firm, and showed no signs of deterioration. This study successfully developed high-performance PVA composites through a sustainable and simple method, overcoming the inherent defects of PVA, and providing strong support for its widespread application in the field of packaging materials.