Flow-induced concentration gradients in shear-banding of branched wormlike micellar solutions.
J Colloid Interface Sci
; 534: 695-703, 2019 Jan 15.
Article
em En
| MEDLINE
| ID: mdl-30268086
ABSTRACT
HYPOTHESIS:
Shear-banding of branched wormlike solutions is a topic of active investigation which has not been fully elucidated. Here, we surmise that flow-induced microstructuring in the shear banding regime is associated with spatial concentration gradients. EXPERIMENTS The experiments focus on the flow-induced behavior of a CTAB/NaSal wormlike micellar system. A unique approach based on a microfluidic-spitter geometry, combined with particle-image velocimetry and high-speed video microscopy, is used to separate the streams flowing out from the core and the near wall zones of the microchannel.FINDINGS:
Here, we present the first direct experimental evidence of the correlation between phase separation and shear banding. By increasing the pressure-drop across a microcapillary, the onset of a grainy texture close to the wall, showing a flow-induced demixing effect, is observed. We use a splitter to measure effluent streams from the center and the near-wall zones in terms of viscosity, conductance and dry mass. We observe that phase-separation induced by the flow correlates with chemical concentration gradients. This confirms our hypothesis that shear-induced local de-mixing of the system is strongly related to chemical concentration gradients.
Texto completo:
1
Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article