Shear-Induced Shish-Kebab Morphology in Polymer Melts - Flow Between Two Parallel Plates versus Coaxial Cylinders

ORAL

Abstract

\textit{In-situ} synchrotron SAXS (small-angle X-ray scattering) studies of shear-induced shish-kebab morphology in isotactic polyprolylene melt under two different flow geometries have been carried out. These geometries included (1) shear between two parallel-plates, where the X-ray beam was perpendicular to the flow and neutral directions, and (2) shear between coaxial cylinders or couette flow, where the X-ray beam was perpendicular to the flow and gradient directions. Time-resolved SAXS patterns revealed the formation of typical shish-kebab morphology under both flow geometries; whereby equatorial streaks due to shish were seen to evolve immediately after shear, followed by meridional maxima due to kebabs. SAXS images obtained under the parallel-plate and couette flow geometries exhibited a striking resemblance indicating the cylindrical symmetry of the shish-kebabs and similar spatial distribution along the orthogonal directions in sheared melts. The high temperature stability of iPP shish-kebabs and its molecular origin will be discussed. The financial support of this work was provided by NSF (DMR-0405432).

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Authors

  • Rajesh Somani

    Stony Brook University

  • Igors Sics

  • Benjamin Hsiao

    Chemistry Department, State University of New York at Stony Brook, Stony Brook, NY 11794, Department of Chemistry, Stony Brook University, Department of Chemistry, State University of New York, Stony Brook, NY 11794 - 3400, Stony Brook University, Chemistry Department, State University of New York at Stony Brook