Effect of SiO₂, PVA and glycerol concentrations on chemical and mechanical properties of alginate-based films

Sodium alginate (SA)/polyvinyl alcohol (PVA)/SiO₂ nanocomposite films were prepared by in situ polymerization through solution casting and solvent evaporation. The effect of different SA/PVA ratios, SiO₂, and glycerol content on the mechanical properties, water content, water solubility, and water vapor permeability were studied. The nanocomposite films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal stability (thermogravimetric analysis/differential thermogravimetry) analyses. The nanocomposites showed the highest values of mechanical properties, such as SA/PVA ratio, SiO₂, and glycerol content was 7:3, 6 wt.%, and 0.25 g/g SA, respectively. The tensile strength and elongation at break (E%) of the nanocomposites increased by 525.7% and 90.7%, respectively, compared with those of the pure alginate film. The Fourier transform infrared spectra showed a new Si–O–C band formed in the SA/PVA/SiO₂ nanocomposite film. The scanning electron microscopy image revealed good adhesion between SiO₂ and SA/PVA matrix. After the incorporation of PVA and SiO₂, the water resistance of the SA/PVA/SiO₂ nanocomposite film was markedly improved. Transparency decreased with increasing PVA content but was enhanced by adding SiO₂.