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  • Key words Viscoelastic surfactant solution  (1)
  • elongational flow  (1)
  • Springer  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Branched viscoelastic surfactant solutions and their response to elongational flow (1997)
    Springer
    Rheologica acta 36 (1997), S. 632-638 
    Details
    ISSN: 1435-1528
    Keywords: Viscoelasticity ; branched micelles ; elongational flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Several years ago, Münstedt and Laun reported on the influence of branching on the elongational flow properties of polymer chains (Münstedt and Laun, 1981). They concluded that, in addition to the molecular weight distribution, the degree of branching strongly affects the degree of strain thickening of the elongational viscosity in such a way that the maximum in this material function increases with branching. In a recent paper by Lin, a ternary system of dodecyldimethylamine oxide-sodium laureth sulphate-sodium chloride surfactant solutions was investigated by CryoTEM and rheology (Lin, 1996). He reported a linear relation between the added sodium chloride and the branching of the wormlike micelles. In this paper we present an investigation of these surfactant solutions in elongational flow. Our results indicate that for branched micellar systems the presence of branching enhances the maximum of the elongational viscosity in the same manner as in the case of polymer melts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367359
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  • 2
    Electronic Resource
    Electronic Resource
    Time dependent flow in equimolar micellar solutions: transient behaviour of the shear stress and first normal stress difference in shear induced structures coupled with flow instabilities (2000)
    Springer
    Rheologica acta 39 (2000), S. 234-240 
    Details
    ISSN: 1435-1528
    Keywords: Key words Viscoelastic surfactant solution ; Shear induced structure ; Flow instabilities ; First normal stress difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Recently we studied time dependent structural changes that are coupled with flow instabilities (Fischer 1998; Wheeler 1998; Fischer 2000). Within a stability analysis, a classification scheme for the feedback circuit of coupled shear-induced structure and flow instabilities was derived by Schmitt et al. (1995) and applied to our samples. Here, inhomogeneous flow layers of different concentration and viscosity are generated by shear-induced diffusion (spinodal demixing) and, as consequence, one no longer observes a homogeneous solution but a type of shear banding that is seen here for the first time. In this paper we present the behaviour of the first normal stress difference observed in the critical shear-rate regime where transient shear-induced structure is coupled with flow instability. Similar to the oscillations of the shear stresses (strain-controlled rheometer) one observes oscillations in the first normal stress difference. This behaviour indicates that elastic structures are built up and destroyed while the shear-induced structures occur and that the induced phase is more elastic than the initial one. Oscillations of shear stress and first normal stress difference are in phase and indicate that both phenomena are caused by the same mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003970000087
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