Leipzig 1999 – wissenschaftliches Programm
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DRG: Deutsche Rheologische Gesellschaft
DRG 10: Suspensionen und Emulsionen
DRG 10.6: Vortrag
Mittwoch, 3. März 1999, 11:20–11:40, HS 21
New aspects in the flow behaviour of viscoelastic surfactant solutions — •Peter Fischer1, Elizabeth K. Wheeler2, and Gerald G. Fuller2 — 1Eidgen"ossische Technische Hochschule, ILW, Universit"atsstr. 2, CH-8092 Z"urich — 2Stanford University, Department of Chemical Engineering, Stanford, CA 94305-5025, USA
In recent years it was found that the non-linear rheological response of wormlike micellar surfactant solutions (cetylpridinium chlorid-sodium salicylat) is not obeying the model character that is found in the linear regime. In general, the non-linear properties cannot be described by extensions of the Maxwell model as done in the Cates or Giesekus Model. For example, some solutions shear thicken, while others experience phenomena such as spurt effect, shear-induced phases, shear induced structures. The analysis of such phenomenon is a complex problem that must take into acccount coupling between flow instabilities and structural changes (Wheeler et al.). In this paper both an overview of these different flow properties and a detail discussion of a unique transient shear induced structure (SIS) that results in a flow instability (FI) is given. Within a stability analysis a classification scheme for the feedback circuit of coupled SIS/FI is derived (Schmitt et al.). Inhomogeneous flow layers of different concentration and viscosity is generated by shear induced diffusion (Spinodal demixing) and, as a consequence, one observes not longer a homogeneous solution but a new type of shear banding that is experimentally observed here in the first time.
V.Schmitt, C.M. Marques and F. Lequeux, PRE 52, 4009 (1995)
E. K. Wheeler, P. Fischer and G. G. Fuller, JNNFM 75, 193 (1998)