Investigation of Rheological Behavior to the State of Dispersion in Polyurethane-Montmorillonite Nanocomposites

Polyurethane-clay nanocomposites were prepared by applying high-intensity ultrasound during the synthesis of clay-urethane nanocomposites. In this article, rheological measurements along with turbidimetry, optical microscopy, X ray diffraction (XRD)and Transmission electron microscope (TEM) analyses were carried out. The results of XRD showed that the distances between silicate layers of clay reached to 41 A0 in the polymeric matrix. Results showed that nanocomposites had higher dynamic moduli, and solid like behavior in comparison to that of neat polyurethane. The strong increase in modulus of nanocomposites was due to the intercalated and dispersed silicate platelets. The increase rate in storage modulus of these composites decreased at higher organoclay loadings and was not linear. Also, the sample that contained 5% organic clay showed a shear thinning behavior at low frequencies. By using the results of XRD, optical microscopy and rheometery analysis, the state of dispersion and optimum percent of clay that has the best dispersion state were obtained. J. Color Sci. Tech. 3(2009), 89-96.© Institute for Color Science and Technology.