Formulation and properties of a model two-component nanocomposite coating from organophilic nanoclays

Polyurethane bicomponent coatings have been modified by formulation with different amount (2-6% by weight) of organophilic nanoclays according to a solution blending procedure. The clays (indicated as 72T and 30B) differ each other in the nature and polarity of the organic quaternary ammonium salt. After application and curing the coatings were characterized by X-rays diffraction (XRD), contact angle measurements, atomic force microscopy (AFM), dynamic-mechanical analysis, tensile tests. The presence of clay additives enhances both modulus and strength of coating materials, and shows some effect also on surface hydrophobicity. The more polar 30B clay seems to form more homogeneous and smoother surfaces, and also a higher coating toughness is retained. Solvent swelling measurements were carried out in toluene allowing the estimate of the extent of clay exfoliation in the material. These measurements along with XRD result suggest that only a partial delamination was achieved.