Effect of poly(vinyl pyrrolidone) on the morphology and physical properties of poly(vinyl alcohol)/sodium montmorillonite nanocomposite films

Nanocomposites of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP) and sodium montmorillonite (Na+MMT) were prepared by solution mixing and then cast into films. X-ray diffraction analysis and images of transmission electron microscopy establish the formation of PVA/Na+MMT intercalated nanocomposite. Exfoliated and highly intercalated PVA/PVP/Na+MMT nanocomposite formed in the presence of PVP. Inclusion of PVP in PVA/Na+MMT matrix enhances the hydrogen bonding interactions between PVA and Na+MMT and thus increases the mechanical properties and thermal stability of PVA/PVP/Na+MMT nanocomposites compared to PVA/Na+MMT nanocomposite. The interactions between PVA, PVP and Na+MMT were established by the Fourier transform infrared spectroscopy. The moisture absorption tendency of both the PVA and PVA/PVP films reduced after the incorporation of Na+MMT at 75% constant relative humidity. Differential scanning calorimetry studies show that the presence of PVP and Na+MMT both are responsible for reducing the heat of fusion, and crystallinity of PVA. The flow behavior of the PVA, PVA/PVP and its nanocomposite solutions has been also studied. Water vapor permeability of PVA/PVP/Na+MMT composite films decreased in the presence of nanoclay due to increasing tortuous paths for diffusion.