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Wall slip,shear banding and instability in the flow of a triblock copolymer micellar solution

S. Manneville, A. Colin, G. Waton, and F. Schoessler — Phys. Rev. E 75, 061502 (2007)

publié le

The shear flow of a triblock copolymer micellar solution — PEO-PPO-PEO Pluronic P84 in brine — is investigated
using simultaneous rheological and velocity profile measurements in the concentric cylinder geometry.
We focus on two different temperatures below and above the transition temperature Tc which was previously
associated with the apparition of a stress plateau in the flow curve. i. At T=37.0 °C < Tc, the bulk flow
remains homogeneous and Newtonian-like, although significant wall slip is measured at the rotor that can be
linked to an inflexion point in the flow curve. ii. At T=39.4 °C > Tc, the stress plateau is shown to correspond
to stationary shear-banded states characterized by two high shear rate bands close to the walls and a very
weakly sheared central band, together with large slip velocities at the rotor. In both cases, the high shear branch
of the flow curve is characterized by flow instability. Interpretations of wall slip, three-band structure, and
instability are proposed in light of recent theoretical models and experiments.