Shear banding instability in wormlike micellar solutions |
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Authors: | MM Britton PT Callaghan |
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Institution: | (1) Institute of Fundamental Sciences-Physics, Massey University, Palmerston North, New Zealand, NZ |
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Abstract: | Using NMR velocimetry and mechanical measurements we study the flow dynamics, within a cone-and-plate rheometer, of the wormlike
micelle system, cetylpyridinium chloride/sodium salicylate (CPyCl/NaSal) at 100 mM/60 mM concentration in distilled water.
Depending on precise conditions within the system, two classes of behaviour are observed, one in which the boundary between
different shear rate phases fluctuates rapidly (on the order of tens of milliseconds) and one in which it migrates slowly
with a time constant of many seconds. These modes of behaviour may depend on minor solution impurities, which presumably affect
the detailed constitutive properties, but also on the externally applied shear rate within a given system. We argue that the
slow migrations are governed by stress relaxation effects while the rapid migrations are flow driven and arise from interfacial
instability.
Received: 2 June 1998 / Received in final form and Accepted: 27 July 1998 |
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Keywords: | PACS 61 25 Hq Macromolecular and polymer solutions polymer melts swelling - 47 20 Ft Instability of shear flows - 47 50 +d Non-Newtonian fluid flows |
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