Waste-Paper-Derived Cellulose Nanocrystal-Reinforced Polyvinyl Alcohol/Sodium Alginate Films: Toward Sustainable and Biodegradable Packaging Materials

A significant quantity of office waste paper (OWP) is produced annually, polluting the environment to a considerable extent. Using such waste to produce valuable materials is a sustainable and effective process. This study aimed to extract high-quality cellulose nanocrystals (CNC) from OWP and evaluate the reinforcing ability in polymer composites. OWP was utilised as a sustainable source of cellulose to address the research gap in incorporating CNC into a PVA/Na-Alg system to develop sustainable barrier films. To obtain CNC, the OWP underwent a series of chemical pretreatments followed by acid hydrolysis. The extracted CNCs exhibited quasi-spherical morphology with diameters of 5 to 20 nm and a crystallinity index of 74.6%. Incorporation of CNCs into the PVA/Na-Alg matrix significantly enhanced thermal stability, tensile strength, and water vapor barrier properties, although the improvements depended on CNC loading. The highest tensile strength (41.27 MPa) was achieved at 1 wt% CNC, whereas the most effective water vapor barrier performance (WVTR of 5.34 gm -2 h -1 ) was observed at 3 wt% loading. All films retained visible-light transmittance above 85%, ensuring optical clarity for transparent packaging applications. At 5 wt% loading, hydrophobicity reached a maximum contact angle of 82.21±1.80°, but mechanical and barrier properties declined due to nanoparticle aggregation. The PVA/Na-Alg film showed biodegradability with 38.5% weight loss in 28 days, while CNC incorporation reduced degradation due to a denser hydrogen-bonded network. These findings demonstrate that OWP-derived CNC added PVA/NaAlg film are a sustainable alternative to petroleum-based packaging films with strong potential for food packaging applications. • Cellulose nanocrystals were successfully extracted from office waste paper. • Nanofiller inclusion increased the tensile strength of the films by 94%. • Composite films exhibited enhanced thermal stability and water resistance. • The biodegradable films successfully extended the shelf life of red chilies. • Developed films proved effective for biodegradable food packaging applications.