Analysis of the structure and mass transport properties of nanocomposite polyurethane

In this work nanocomposite adhesives obtained using an organically modified montmorillonite (OMM) in a polyurethane matrix were studied. The basal distance of OMM before and after mixing with the polyol and after curing was characterized by X-Ray diffraction. The viscosity of polyols-OMM systems was studied as function of shear rate in a cone - plate rheometer in order to correlate the viscosity with the aggregation state of OMM. A simple model accounting for an apparent increase of rheological units size associated with the intercalation of macromolecules into OMM galleries, is proposed. Curing was performed at room temperature for 1 week. The basal distances of crosslinked PU nanocomposites was obtained by X-ray diffraction. The glass transition temperature, Tg, of PU nanocomposites, as measured using differential scanning calorimetry, increases with increasing volume fraction of OMM. Finally, the permeability to oxygen and water vapour of polyurethane clay-nanocomposites was measured. The gas permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OMM.