Fabrication and characterization of CMC-based nanocomposites reinforced with sodium montmorillonite and TiO₂ nanomaterials

In this study, a novel carboxymethyl cellulose (CMC)-based ternary nanocomposite films containing sodium montmorillonite (Na-MMT) (1, 3 and 5% wt) and titanium dioxide (TiO₂) (1, 3 and 5% wt) nanoparticles (NPs) were made via casting method. The results showed that addition of NPs decremented water vapor permeability of the films up to 39% and 50% by adding Na-MMT, and Na-MMT + TiO₂, respectively, while moisture content, density and glass transition temperature incremented slightly. The nanoclays amplified resistance of the nanocomposites against tensile stress and Young's modulus (YM) of the films at the expense of elongation at break. A synergistic effect of NPs on moisture uptake reduction (≈ 40%) of films was observed. Nano-TiO₂ was strongly effective in UV-light blocking (The films containing 5% TiO₂ removed more than 99% of UV and more than 98% of visible lights). The interactions, crystallinity and morphology of the nanocomposites were investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). Development of hydrogen bonds between the hydroxyl groups of CMC and nanoparticles was indicated by FT-IR spectroscopy. Conforming to the XRD analysis, clay nanolayers organized an intercalated structure in the nanocomposites, whereas a limited agglomeration of TiO₂ nanoparticles led to increment of films crystallinity. SEM micrographs showed well-dispersed Na-MMT and TiO₂ NPs through the films surface especially at low concentrations. In conclusion, although the films loaded with nanoclays exhibited better properties than the control film, inclusion of TiO₂ more improved the functional characteristics of them and extended the potential as a biodegradable packaging.