Unique rheological behavior of rubber based nanocomposites

Montmorillonite clay (N) based nanocomposites were prepared using three different grades of acrylonitrile butadiene rubber (NBR) (19%, 34%, and 50% acrylonitrile contents), styrene butadiene rubber (SBR), and polybutadiene rubber (BR). Rheological study was carried out on these nanocomposites at three different temperatures (110 degrees C, 120 degrees C, and 130 degrees C) over a range of shear rates for comparison. The results showed that the shear viscosity decreased with increasing shear rate and incorporation of the unmodified (N) and the modified (OC) fillers up to a certain loading, when the results were compared with the gum rubber. This effect became more prominent with increasing polarity of the rubber. The die swell, on the other hand, decreased with loading of N and OC. With increasing filler volume fraction, the die swell further decreased. Decrease of viscosity with concomitant decrease of die swell is unique in such systems. Consecutive runs of the same sample over different shear rates increased the viscosity. The results were explained with the help of X-Ray Diffraction (XRD) data and Transmission Electron Microscopy (TEM). (c) 2005 Wiley Periodicals, Inc.