Abstract
Mixtures of inorganic clay platelets dispersed in a polymer matrix have dimensional, mechanical and thermal barrier properties that have motivated interest in potential applications in the automotive, aerospace and packaging industries. Such polymer/clay nanocomposites are formed by the intercalation and exfoliation of swelling clays such as montmorillonite in a polymer matrix. Nylon and epoxy nanocomposites are among the most successful polymer /clay hybrids formed to date. The high degree of exfoliation of these materials contributes to the enhancement of solid-state material properties such as strength, modulus and heat distortion temperature. While the dispersion of nanocomposites is often probed by X-ray scattering and electron microscopy, melt-state rheology has also recently been used. Melt-state rheology is furthermore an indicator of flow behavior in processing operations such as injection molding. We have used melt- state rheology in conjunction with wide-angle X-ray scattering to assess the relative dispersion of polypropylene nanocomposites prepared by melt compounding. The linear viscoelasticity and wide-angle X-ray scattering of a polypropylene/clay hybrid material for by melt compounding is reported. Non-linear rheological measurements have also been undertaken. The results of flow reversal experiments reveal the characteristic time for the evolution of nanocomposite morphology.