Crosslinked aqueous dispersion of silylated poly (urethane-urea)/clay nanocomposites

Stable water-borne crosslinked silylated poly (urethane-urea) (CSPU)/clay nanocomposites, reinforced with various amounts of the organically modified clay, were prepared by a polyaddition reaction of toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI), polytetramethylene glycol and dimethylol propionic acid. This was followed by end-capping the free NCO groups of the PU prepolymer with phenylamino propyl trimethoxysilane and self-crosslinking. The particle size, viscosity and storage stability of these nanocomposites were measured. The particle size and viscosity of the IPDI-based nanocomposites were higher than the TDI-based ones. Intercalation of the silicate layer in the CSPU matrix were conformed by X-ray diffraction pattern and transmission electron microscopy studies. The mechanical properties of the SPU/clay nanocomposites were tested by tensile, dynamic mechanical, and nano-indentation measuring techniques and the respective properties were found to be enhanced by the reinforcing effect of organophilic clay. Modulus and hardness increased with an increase in the clay content in the CSPU matrix. Thermal stability, water and xylene resistance of the nanocomposites increased, as compared to pure CSPU and these properties increased with an increase in clay content. The mechanical properties, water and xylene resistance of the TDI-based nanocomposites were higher compared to the IPDI-based nanocomposites. A marginal reduction in transparency was observed with the addition of clay. Storage stability results confirmed that the prepared nanocomposite dispersions were stable. (c) 2006 Elsevier Ltd. All rights reserved.