Structure and Properties of Poly(vinyl alcohol)/Na⁺ Montmorillonite Nanocomposites

TLDR

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites were fabricated by casting from a polymer/silicate aqueous suspension. The composites exhibit both exfoliated and intercalated montmorillonite layers, forming a new crystalline phase with higher melting temperature, which enhances mechanical strength, thermal stability, and reduces water vapor permeability by up to 60 % while preserving optical clarity.

Abstract

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compositions were created by casting from a polymer/silicate water suspension. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties. Namely, the hybrid polymer/silicate systems have mechanical, thermal, and water vapor transmission properties, which are superior to that of the neat polymer and its conventionally filled composites. For example, for a 5 wt % MMT exfoliated composite, the softening temperature increases by 25 °C and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale dispersion of filler, the nanocomposites retain their optical clarity.