Triggers and signatures of shear banding in steady and time-dependent flows

Abstract

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From Wall Slip to Bulk Shear Banding in Entangled Polymer Solutions

“…Moreover, our account of shear banding has little in common with the recent theoretical accounts in the literature. [98,99] As a general treatment of the phenomenon of shear banding in complex fluids, these numerical analyses do not explicitly explore how chain disentanglement may occur and what the rheological consequences of chain disentanglement are. The goal of this paper is modest: to demonstrate that the entangled polybutadiene solutions can undergo massive wall slip in controlled-rate mode and exhibit a transition from wall slip to shear banding as a function of b * /H in a conventional cone-plate setup without edge failure.…”

i-Rheo: determining the linear viscoelastic moduli of colloidal dispersions from step-stress measurements

“…Indeed, concentrated colloidal suspensions are often characterised by flow-induced inhomogeneities, such as shear banding, which can affect the response of colloidal dispersions during creep measurements, especially after a long time, 30,32 when approaching and/or crossing the glass transition. [30][31][32]51 This was not a problem for the lowest volume fractions explored in this work, i.e. f = 0.40, 0.48 and 0.50, which did not manifest flow inhomogeneities within the measurement time-window ( Fig.…”

“…[18][19][20] When a constant shear rate or a stress (creep) is suddenly applied to a dense suspension, the system yields and flows due to the rupture of the cages. [21][22][23][24][25][26][27][28] The transition to flow can be affected by shear banding, [29][30][31][32] ageing and history effects. 33 Here, we demonstrate that the evaluation of the materials' LVE moduli by means of i-Rheo applied to creep measurements is a reliable and faster alternative to conventional DFS measurements, also in the case of colloidal suspensions.…”

Periodic “stick-slip” transition within a continuum model for entangled supramolecular polymers

“…when the applied shear rate,γ av , is betweenγ low andγ high , the system spontaneously forms two macroscopic bands of fluid, one at a shear rateγ low and the other atγ high [29]. In the banded regime, i.e.γ low <γ av <γ high , the stress stays constant, or slightly increases due to curvature effects (not considered here) in geometries such as cylindrical Couette [57][58][59].…”

“…Polymeric systems with reversible junctions, such as entanglements or associative stickers, are also known to undergo flow instabilities, e.g. spurt [28], shear banding [18,24,[29][30][31][32] or melt fracture [33][34][35]. In concentrated solutions of telechelic polymers, i.e.…”