Challenges in process rheometry

Dealy, John M.

doi:10.1007/bf01329297

Cited by 57 publications

(80 citation statements)

References 10 publications

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“…The crossover between the linear and nonlinear rheology regime can be roughly given by the Weissenberg number. The Weissenberg number is defined as W i ≡ λγ [46]. For W i ≪ 1 the rheology is linear and the solutions behave as Maxwellian fluids.…”

Section: Nonlinear Rheologymentioning

confidence: 99%

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

et al. 2012

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In the past twenty years, shear-banding flows have been probed by various techniques, such as rheometry, velocimetry and flow birefringence. In micellar solutions, many of the data collected exhibit unexplained spatiotemporal fluctuations. Recently, it has been suggested that those fluctuations originate from a purely elastic instability of the shear-banding flow. In cylindrical Couette geometry, the instability is reminiscent of the Taylor-like instability observed in viscoelastic polymer solutions. The criterion for purely elastic Taylor-Couette instability adapted to shear-banding flows suggested three categories of shear-banding depending on their stability. In the present study, we report on a large set of experimental data which demonstrates the existence of the three categories of shear-banding flows in various surfactant solutions. Consistent with theoretical predictions, increases in the surfactant concentration or in the curvature of the geometry destabilize the flow, whereas an increase in temperature stabilizes the flow. But experiments also exhibit some interesting behaviors going beyond the purely elastic instability criterion.

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Section: Nonlinear Rheologymentioning

confidence: 99%

Interplay between elastic instabilities and shear-banding: three categories of Taylor–Couette flows and beyond

et al. 2012

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“…To enable comparison, strain rates are given in terms of nondimensional Weissenberg numbers (Wi R ¼ _ ε 0 τ R indicated at each experiment) instead of the absolute value _ ε 0 . Wi R compares the Rouse relaxation time of the chain contour length τ R to the imposed rate of deformation _ ε 0 [28]. As long as Wi R < 1 the number of Kuhn lengths between entanglements N e is unimportant.…”

Section: -2mentioning

confidence: 99%

Linear and Nonlinear Universality in the Rheology of Polymer Melts and Solutions

et al. 2015

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“…Finally, sampling valves themselves can sometimes damage the structure (for instance, droplet size in an emulsion) thereby making the offline measurement of little utility. In view of all these issues, much attention has been given to the development of on-line or in-line measurements of viscosity for a range of rheologically complex substances over the past 20 years or so ( Cheng et al ., 1984 ;Dealy, 1990 ;Steffe, 1996 ;Roberts, 2001) . The terms on-line and in-line are used here to distinguish the location of the sensor being in a bye-pass line or in the actual process line itself, but both refer to continuous monitoring of quality parameters.…”

Section: On-line Viscometrymentioning

confidence: 99%