| Abstract: | Polymer melt‐direct intercalation or exfoliation is a promising approach for the preparation of nanocomposites. The structure of nanoclay platelets in the nanocomposites depends not only on the properties of polymer matrix and nanoclay, but also on the operating conditions during processing. The objective of the present work is to investigate the effects of clay chemical modifiers, mixing protocols, and operating conditions upon the clay structure in nanocomposites prepared with a corotating twin‐screw extruder. Two mixing methods were used for the nanocomposite preparation: two‐step mixing and one‐step mixing. Experimental results obtained from melt flow index and complex viscosity measurements suggest that nanoclay C15A is more exfoliated than C30B in a polypropylene homopolymer containing a maleic anhydride grafted PP (PB) as compatibilizer. The two‐step mixing method results in better exfoliation for the nanofillers than the one‐step mixing method. A numerical simulation has been carried out to evaluate the mean residence time and shear rate in different screw configurations under various process conditions. X‐ray diffraction experiments indicate that the residence time is a dominant factor in producing satisfactory nanocomposites in extruders. However, high shear rate coupled with long residence time might result in poor exfoliation of clay. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1891–1899, 2004 |
