Capillary Break-up Rheometry of Low-Viscosity Elastic Fluids

By L. Rodd, Timothy P. Scott, Justin J. Cooper-White, G. H. McKinley. 2005

366 citations recorded by the source corpus.

Abstract We investigate the dynamics of the capillary thinning and break-up process for low viscosity elastic fluids such as dilute polymer solutions. Standard measurements of the evolution of the midpoint diameter of the necking fluid filament are augmented by high speed digital video images of the break up dynamics. We show that the successful operation of a capillary thinning device is governed by three important time scales (which characterize the relative importance of inertial, viscous and elastic processes), and also by two important length scales (which specify the initial sample size and the total stretch imposed on the sample). By optimizing the ranges of these geometric parameters, we are able to measure characteristic time scales for tensile stress growth as small as 1 millisecond for a number of model dilute and semi-dilute solutions of polyethylene oxide (PEO) in water and glycerol. If the final aspect ratio of the sample is too small, or the total axial stretch is too great, measurements are limited, respectively, by inertial oscillations of the liquid bridge or by the development of the well-known beads-on-a-string morphology which disrupt the formation of a uniform necking filament. By considering the magnitudes of the natural time scales associated with viscous flow, elastic stress growth and inertial oscillations it is possible to construct an “operability diagram” characterizing successful operation of a capillary breakup extensional rheometer. For Newtonian fluids, viscosities greater than approximately 70 mPas are required; however for dilute solutions of high molecular weight polymer, the minimum viscosity is substantially lower due to the additional elastic stresses arising from molecular extension. For PEO of molecular weight 2 · 106 g/mol, it is possible to measure relaxation times of order 1 ms in dilute polymer solutions with zero-shear-rate viscosities on the order of 2 – 10 mPas.

Subfields: Fluid Flow and Transfer Processes, Polymers and Plastics

View Paper: https://www.semanticscholar.org/paper/def4454e100beff83d1bac9b98c7dc6b5dbfdd03

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Citations in the corpus

Extensional rheology of a shear-thickening cornstarch and water suspension (2010, methodology): “…the extensional rheology of the less-concentrated and less-viscous fluids (Anna and McKinley 2001; Bazilevsky et al. 1990; Clasen et al. 2006; Entov and Hinch 1997; Kojic et al. 2006; McKinley and Tripathi 2000; Plog et al. 2005; Rodd et al. 2005; Stelter et al. 2000; Yesilata et al. 2006).”
“Vegetable Dynamicks”: The Role of Water in Plant Movements (2012, background): “Measurements of the thinning dynamics of the liquid filaments [capillary break-up rheometry (Rodd et al. 2005)] show that this unique trapping property comes from the high viscoelasticity and apparent elongational viscosity of the digestive liquid, which may be more than 105 that of water.”
How dilute are dilute solutions in extensional flows (2006, background): “For further details on the geometry and spect ratios see Rodd et al. 2005 .”