Preparation and characterization of poly (lactic acid)/rice straw cellulose bio-composite films for packaging applications

The development of sustainable and biodegradable poly(lactic acid) (PLA) bio-composite films using cellulose fibers extracted from rice straw (RSC), a major agricultural waste product in Southeast Asia. This study tackles pressing environmental issues arising from the excessive use and improper disposal of petroleum-based plastics, focusing on single-use applications such as food packaging. Rice straw cellulose was extracted through a chemical process involving alkaline, bleaching, and acidic treatments, resulting in cellulose fibers with enhanced purity. These cellulose fibers were subsequently modified with alkyl ketene dimer (AKD), a cost-effective and hydrophobic reagent with food-safe properties. Eco-friendly, solvent-free ball-milling and thermal treatment processes were employed to improve their compatibility with the hydrophobic PLA matrix. The success modification was verified by Fourier-transform infrared (FTIR) spectroscopy, demonstrating the reaction between the lactone ring of AKD and hydroxyl groups (-OH) of cellulose successfully generated β-ketoester bonds, reflected by a new band at 1735 cm-1, which imparted hydrophobic characteristics to the cellulose surface and improved dispersion within the PLA matrix.The PLA/RSC bio-composite films were prepared using a solvent-casting method with cellulose fiber contents varying between 1-7 %wt. The films' mechanical properties, water vapor permeability (WVP), and hydrophobicity (water contact angle) were investigated. The results indicated significant improvements in mechanical properties, including tensile strength and elongation at break, particularly at a 3 %wt loading of the AKD-modified cellulose. The films also exhibited enhanced hydrophobicity, with water contact angles increasing to 91.5°, demonstrating improved water resistance compared to neat PLA films. Furthermore, the inclusion of modified cellulose maintained the water vapor permeability of the films, ensuring their suitability for packaging applications that require effective moisture control. By transforming rice straw into high-performance bio-composite films, this research promotes a bio-circular economy, reduces environmental pollution, and creates value-added products. Moreover, the developed PLA/RSC bio-composite films present a promising eco-friendly for smart packaging applications.