Volume 41, Number 6, March II 1998
|Page(s)||677 - 682|
|Section||Cross-disciplinary physics and related areas of science and technology|
|Published online||01 September 2002|
Flow-structure relationship of shear-thickening surfactant solutions
Unité Mixte de Recherche CNRS, Université de
Montpellier II n 5581,
Groupe de Dynamique des Phases Condensées, F-34095 Montpellier Cedex 05,
2 Department of Chemical Engineering, Doherty Hall 2208C, Carnegie Mellon , Pittsburgh PA 15213, USA
3 Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9, France
Accepted: 26 January 1998
The shear-thickening transition in dilute surfactant solutions is investigated using rheology and small-angle neutron scattering. Steady shear experiments on a new thickening system, the tosylate of cethyltrimethylammonium, revealed a continuous increase of the apparent viscosity above a critical strain rate . Concentration and temperature variations of are derived, and the former is found to be in contradiction with a theoretically predicted gelation. From the scattering under shear, we establish a clear correlation between flow and structure. In the thickening region, the patterns are due to the superposition of two coexisting states, one viscoelastic entangled sheared network and one still purely viscous made of short aggregates. At higher , the former state dominates and its increasing orientation results in shear-thinning.
PACS: 82.70.-y – Disperse systems / 83.50.Qm – Thixotropy; thickening flows / 61.12.Ex – Neutron scattering techniques (including small-angle scattering)
© EDP Sciences, 1998
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