Shear-thickening and structure formation in polymer solutions |
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| Institution: | 1. Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany;2. Bruker JPK BioAFM, Am Studio 2d, 12489 Berlin, Germany;3. G.E.R.N. Center for Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Engesserstr. 4B, 79108 Freiburg, Germany;4. Cluster of Excellence livMatS@FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies, Georges-Köhler-Allee 105, 79110 Freiburg, Germany |
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| Abstract: | The phenomenon of shear-thickening has been investigated for solutions of several high molecular weight crystallizable polymers using capillary rheometry. The systems studied: polyethylene/xylene, polypropylene/tetralin, and poly(ethylene oxide)/ethanol have previously been investigated for their flow induced crystallization behavior. A shear-thickening pattern occurs in the relative viscosity vs. shear rate flow curves for the first two systems which, for the former of the two, also shows a strong molecular weight dependence. For the range of conditions studied, the poly(ethylene oxide)/ethanol system did not show shear-thickening, exhibiting instead a shear thinning pattern for the lower molecular weight sample studied and a constant viscosity high shear plateau for the higher MW system. The conclusion is reached that shear-thickening is due to molecular entanglements formed during flow and the implications of these results to the phenomenon of precursor phase separation in flow-induced fibrous crystallization are discussed. |
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