Structure and properties of poly(vinyl alcohol)/Na+ montmorillonite nanocomposites

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compos itions were created by casting from a polymer/silicate water suspension. Th e composite structure study revealed a coexistence of exfoliated and interc alated MMT layers, especially for low and moderate silicate loadings. The i norganic layers promote a new crystalline phase different than the one of t he respective neat PVA, characterized by higher melting temperature and a d ifferent crystal structure. This new crystal phase reflects on the composit e materials properties. Namely, the hybrid polymer/silicate systems have me chanical, thermal, and water vapor transmission properties, which are super ior to that of the neat polymer and its conventionally filled composites. F or example, for a 5 wt % MMT exfoliated composite, the softening temperatur e increases by 25 degreesC and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the wate r permeability. Furthermore, due to the nanoscale dispersion of filler, the nanocomposites retain their optical clarity.