Synthesis and properties of vermiculite-reinforced polyurethane nanocomposites.

Natural vermiculite was modified by cation exchange with long-chain quaternary alkylammonium salts and then dispersed in polyether-based polyols with different structures and ethylene oxide/propylene oxide ratios. The dispersions were evaluated by X-ray scattering and rheology. In all polyol dispersions tested, polyols were intercalated into the vermiculite interlayers. Also, significant shear thinning behavior was observed. A large interlayer spacing of ∼90 Å was achieved in one polyol suitable for polyurethane elastomer synthesis. In polyurethane made with this polyol, clay platelets were extensively intercalated or exfoliated. The composites showed a >270% increase in tensile modulus, >60% increase in tensile strength, and a 30% reduction in N(2) permeability with a loading of 5.3 wt % clay in polyurethane. Differential scanning calorimetry and dynamic mechanical analysis revealed that the nanoclay interacts with the polyurethane hard segments.