Steady-state shear banding in entangled polymers?

Hu, Yike

doi:10.1122/1.3494134

Cited by 54 publications

(65 citation statements)

References 30 publications

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“…This criterion was also predicted on the basis of fluid-universal analytical calculations in [47], and has been confirmed in numerical simulations of polymeric fluids [48] and SGMs [3]. It is consistent with experimental observations in polymers [14,33,34,41,[44][45][46]57], carbopol microgels [43], and carbon black suspensions [42].…”

Section: A)supporting

confidence: 72%

“…In view of this, a natural question to ask is whether shear banding might also arise in these time-dependent flows and, if so, under what conditions. Over the past decade, a body of experimental data has accumulated to indicate that it does indeed occur: In shear startup [6,7,16,[32][33][34], following a step strain (in practice a rapid strain ramp) [35][36][37][38][39][40][41], and following a step stress [14,33,34,[41][42][43][44][45][46].…”

Section: A)mentioning

confidence: 99%

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Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

Carter¹,

Girkin²,

Fielding³

2016

Journal of Rheology

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe investigate theoretically shear banding in large amplitude oscillatory shear (LAOS) of polymeric and wormlike micellar surfactant fluids. In large amplitude oscillatory shear strain, we observe banding at low frequencies and sufficiently high strain rate amplitudes in fluids for which the underlying stationary constitutive curve of shear stress as a function of shear rate is nonmonotonic. This is the direct (and relatively trivial) analog of quasisteady state banding seen in slow strain rate sweeps along the flow curve. At higher frequencies and sufficiently high strain amplitudes, we report a different but related phenomenon, which we call "elastic" shear banding. This is associated with an overshoot in the elastic (Lissajous-Bowditch) curve of stress as a function of strain and we suggest that it might arise rather widely even in fluids that have a monotonic underlying constitutive curve, and so do not show steady state banding if under a steadily applied shear flow. It is analogous to the elastic banding triggered by stress overshoot in a fast shear startup predicted previously by R. L. Moorcroft and S. M. Fielding [Phys. Rev. Lett. 110(8), 086001 (2013)], but could be more readily observable experimentally in this oscillatory protocol due to its recurrence in each half cycle. In large amplitude oscillatory shear stress, we report shear banding in fluids that shear thin strongly enough to have either a negatively or a weakly positively sloping region in the underlying constitutive curve, noting again that fluids in the latter category do not display steady state banding in a steadily applied flow. This banding is triggered in each half cycle as the stress magnitude transits the region of weak slope in an upward direction such that the fluid effectively yields. It is strongly reminiscent of the transient banding predicted previously in step stress [R. L. Moorcroft and S. M. Fielding, Phys. Rev. Lett. 110(8), 086001 (2013)]. Our numerical calculations are performed in the Rolie-poly model of polymers and wormlike micelles, but we also provide arguments suggesting that our results should apply more widely. Besides banding in the shear strain rate profile, which can be measured by velocimetry, we also predict banding in the shear and normal stress components, measurable by birefringence. As a backdrop to understanding the new results on shear banding in LAOS, we also briefly review earlier work on banding in other time-dependent protocols, focusing in particular on...

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Section: A)supporting

confidence: 72%

Section: A)mentioning

confidence: 99%

Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

Carter¹,

Girkin²,

Fielding³

2016

Journal of Rheology

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“…A well-known failure of the DE theory lies in its inability to predict the experimentally observed monotonic steady state constitutive relationship between shear stress and shear rate [Doi and Edwards (1979)]. Specifically, if the constitutive curve indeed is non-monotonic as predicted by the DE model, shear banding should occur, meaning that bands with different shear rates could form in the sample above a critical shear stress or shear rate; however, this non-monotonicity or shear banding has not been normally observed [Hu (2010); Hayes et al (2008)]. On the other hand, in step strain tests, it was found that the DE model underestimates the strain softening behavior in some cases [Osaki and Kurata (1980); Vrentas and Graessley (1982)].…”

Section: Introductionmentioning

confidence: 99%

Flow field visualization of entangled polybutadiene solutions under nonlinear viscoelastic flow conditions

Li¹,

Hao²,

McKenna³

et al. 2013

Journal of Rheology

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SynopsisUsing self-designed particle visualization instrumentation, startup shear and step strain tests were conducted under a series of systematically varied rheological and geometrical conditions, and the velocity profiles of three different well-entangled polybutadiene/oligomer solutions were obtained. For startup shear tests, in the regime of entanglement densities up to 89 and Weissenberg numbers up to 18.6, we generally observe either wall slip and a linear velocity/strain profile or simply the linear profile with no wall slip unless a massive edge fracture or instability has occurred in the sample. Meanwhile, step strain tests were conducted under similar and higher step Weissenberg numbers, and little motion was observed upon cessation. These results lead us to a conclusion that there is no compelling evidence of shear banding or non-quiescent relaxation in the range of entanglement density and Wi investigated; we interpret the results to imply that any observed banding probably correlates with edge effects, and these probably are also present in the work of the S. Q. Wang group, and they lead to shear banding.

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“…Numerous classes of non-Newtonian fluids are known to exhibit shear banding behavior (Olmsted, 2008), from various kinds of yield stress fluids (Møller et al, 2008;Divoux et al, 2010) to entangled polymer melts (Tapadia et al, 2006;Hu, 2010) and wormlike micellar solutions (Britton and Callaghan, 1997;Salmon et al, 2003;Manneville et al, 2004b,a;Lopez-Gonzalez et al, 2006;Boukany and Wang, 2008;Lettinga and Manneville, 2009). Wormlike micelles are a particularly interesting class of shear banding systems because they are widely used in consumer products, and they have become a canonical model system for probing shear banding.…”

Section: Introductionmentioning

confidence: 99%

Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

et al. 2012

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We explore the behavior of a wormlike micellar solution under both steady and large amplitude oscillatory shear (LAOS) in a cone-plate geometry through simultaneous bulk rheometry and localized velocimetric measurements. First, particle image velocimetry is used to show that the shear banded profiles observed in steady shear are in qualitative agreement with previous results for flow in the cone-plate geometry. Then under LAOS, we observe the onset of shear-banded flow in the fluid as it is progressively deformed into the non-linear regime -this onset closely coincides with the appearance of higher harmonics in the periodic stress signal measured by the rheometer. These harmonics are quantified using the higher order elastic and viscous Chebyshev coefficients e n and v n , which are shown to grow as the banding behavior becomes more pronounced. The high resolution of the velocimetric imaging system enables spatiotemporal variations in the structure of the banded flow to be observed in great detail. Specifically, we observe that at large strain amplitudes (γ 0 ≥ 1) the fluid exhibits a 3-banded velocity profile with a high shear rate band located in-between two lower shear rate bands adjacent to each wall. This band persists over the full cycle of the oscillation, resulting in no phase lag being observed between the appearance of the band and the driving strain amplitude. In addition to the kinematic measurements of shear banding, the methods used to prevent wall slip and edge irregularities are discussed in detail, and these methods are shown to have a measurable effect on the stability boundaries of the shear banded flow.

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Steady-state shear banding in entangled polymers?

Cited by 54 publications

References 30 publications

Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

Flow field visualization of entangled polybutadiene solutions under nonlinear viscoelastic flow conditions

Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

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