Development and characterization of rice straw-derived all-cellulose nanocomposite films reinforced with cellulose nanofibers obtained via high-intensity ultrasonication and high-shear dispersion

Abstract

Agricultural residue, rice straw, represents an underutilized source of cellulose with potential for value-added applications. In the present study, all-cellulose nanocomposite films were developed by incorporating cellulose nanofibers (CNFs) as reinforcing nanofillers within a regenerated cellulose matrix. The films were fabricated using a lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solvent system, providing a homogeneous dispersion of CNFs and facilitating strong interfacial interactions between the matrix and the nanofillers. The influence of CNF concentrations (0%, 3%, 5%, 7%, and 9%) on the morphology, barrier properties, crystallinity, mechanical performance, optical transparency, and thermal properties of the all-cellulose nanocomposite (ACNC) films was systematically evaluated. The results indicated that tensile strength and modulus increased significantly with higher CNF concentrations, although the films exhibited brittleness at 9% CNF. FTIR analysis showed that the functional groups in the cellulose structure remained intact in the nanocomposites. The surface morphology of ACNCs studied through Field Emission-Scanning Electron Microscopy (FE-SEM) showed the uniform distribution of CNFs within the cellulose matrix. The XRD analysis indicated that the incorporation of CNFs increased the crystallinity index of ACNC films, with CNF7 exhibiting the highest CI of 61.50%. The films were also characterized for their density, porosity, and moisture content, which were found to be influenced by the CNF concentration. The water vapour transmission rate (WVTR) and oxygen transmission rate (OTR) of CNF7 were 44.7 ± 3.0 g m⁻² day⁻¹ and 5.6 ± 0.8 cm³ m⁻² day⁻¹, respectively, which were significantly lower than those of CNF0, likely due to increased tortuosity arising from CNF reinforcement. Although optical transmittance decreased with the incorporation of CNFs, the films retained sufficient transparency for food packaging applications. Thermal stability was also enhanced upon CNF addition, with the peak degradation temperature reaching 335.4 °C in CNF7. Biodegradability assessment using enzymatic degradation showed complete degradation of CNF7 within 75 days. Overall, the results highlight strong intermolecular interactions between CNFs and the cellulose matrix, leading to enhanced functional properties and demonstrating the potential of CNF-reinforced films for sustainable food packaging applications.