Steady-state shear banding in entangled polymers?

Velocity profiles of highly entangled polymer solutions under shear have been measured using particle tracking velocimetry to ascertain whether steady-state shear banding occurs in these samples. Under controlled torque flow, the velocity profile becomes nonlinear and the shear rate starts to rise w...

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Bibliographic Details
Published in:Journal of rheology (New York : 1978) 2010-11, Vol.54 (6), p.1307-1323
Main Author: Hu, Y. Thomas
Format: Article
Language:English
Subjects:
Applied sciences
Disentanglement
Edge fracture
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Properties and characterization
Rheology and viscoelasticity
Shear banding
Velocimetry
Velocity profile
Wall slip
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Summary:Velocity profiles of highly entangled polymer solutions under shear have been measured using particle tracking velocimetry to ascertain whether steady-state shear banding occurs in these samples. Under controlled torque flow, the velocity profile becomes nonlinear and the shear rate starts to rise when the true shear strain reaches about 2.5, suggesting that the shear rate rise is initiated by chain alignment and/or disentanglement. At long times, the velocity profile can become either smoothly curved or sharply banded for the same sample in the same geometry, implying that shear banding is not a deterministic behavior as expected from a non-monotonic constitutive relation. It is suggested that the stable shear banding observed in the measured entangled polymer solution is not true steady-state shear banding but may be “trapped” transient banding.
ISSN:0148-6055
1520-8516
DOI:10.1122/1.3494134