Comparison of properties of poly(vinyl alcohol) nanocomposites containing two different clays

Morphologies, thermo-optical properties, and gas barriers of poly(vinyl alcohol) (PVA) hybrid films containing two different clays are compared. Saponite (SPT) and hydrophilic bentonite (BTT) were used as the reinforcing filler in the fabrication of PVA hybrid films, which were synthesized from aqueous solutions and were solvent-cast at room temperature under vacuum, yielding 20-31-μm-thick PVA hybrid films with varying clay contents. The addition of small amounts of clay is sufficient to improve the thermal properties and gas barriers of PVA hybrid films. Even polymers with a low clay content (3-10 wt%) were found to exhibit much higher transition temperature values than pure PVA. The addition of BTT was more effective than the addition of SPT for improving the thermal properties and gas barrier in the PVA matrix. The PVA hybrid films containing 5 wt% SPT were equibiaxially stretched, with stretching ratios ranging from 150% to 250%. Clay dispersion, morphology, optical transparency, and gas permeability were then examined as a function of the equibiaxial stretching ratio. PVA hybrid films with a stretching ratio of ≥ 150% displayed homogeneously dispersed clay within the polymer matrix and exfoliated nanocomposites.