Effect of a spectrum of relaxation times on the capillary thinning of a filament of elastic liquid

Entov, V. M.; Hinch, E. J.

doi:10.1016/s0377-0257(97)00022-0

Cited by 387 publications

(488 citation statements)

References 2 publications

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“…With Weissenberg numbers W i = λd ln L/dt ≫ 1 the constant force pull ultimately imposes an almost affine deformation on the microstructural elements in the polymeric sample towards their finite extensibility limit. In contrast to this in capillary breakup (CABER) type experiments the Weissenberg number remains in the elastocapillary balance regime constant at W i = 2/3 [12,9] and the polymeric chains are not deforming affinely with the flow [23,16]. Although the polymer chains will also in a Caber experiment eventually approach their finite extensibility limit, this requires higher strains than for the affine deformation with the CFP technique.…”

Section: Introductionmentioning

confidence: 92%

Constant force extensional rheometry of polymer solutions

Szabó

McKinley

Clasen

2012

Journal of Non-Newtonian Fluid Mechanics

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We revisit the rapid stretching of a liquid filament under the action of a constant imposed tensile force, a problem which was first considered by Matta & Tytus [JN-NFM vol. 35, pp 215-229, 1990]. A liquid bridge formed from a viscous Newtonian fluid or from a dilute polymer solution is first established between two cylindrical disks. The upper disk is held fixed and may be connected to a force transducer while the lower cylinder falls due to gravity. By varying the mass of the falling cylinder and measuring its resulting acceleration, the viscoelastic nature of the elongating fluid filament can be probed. In particular, we show that with this constant force pull (CFP) technique it is possible to readily impose very large material strains and strain rates so that the maximum extensibility of the polymer molecules may be quantified. This unique characteristic of the experiment is analyzed numerically using the FENE-P model and two alternative kinematic descriptions; employing either an axially-uniform filament approximation or a quasi two-dimensional Lagrangian description of the elongating thread. In addition, a second order pertubation theory for the trajectory of the falling mass is developed for simple viscous filaments. Based on these theoretical considerations we develop an expression that enables estimation of the finite extensibility parameter characterizing the polymer solution in terms of quantities that can be extracted directly from simple measurement of the time-dependent filament diameter.

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Section: Introductionmentioning

confidence: 92%

Constant force extensional rheometry of polymer solutions

Szabó

McKinley

Clasen

2012

Journal of Non-Newtonian Fluid Mechanics

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“…Newtonian and viscoelastic fluids have distinctively different filament thinning profiles. For Newtonian fluids, the elastic stresses are insignificant and hence the extensional flow is primarily caused by a viscocapillary balance Entov and Hinch 1997). The filament radius decreases linearly with a slope of -r/g S where g S is the shear viscosity of the Newtonian fluid.…”

Section: Capillary Break-up Extensional Rheometrymentioning

confidence: 99%

“…Analysis of the data collected enables the determination of k E , the characteristic time governing the elasto-capillary thinning (Entov and Hinch 1997;Liang and Mackley 1994) and G, the elastic modulus. Although the constant k E with the dimension of time has been often mentioned in the literature as a 'relaxation time' it is different than the time constants associated with stress relaxation following cessation of steady shear.…”

Section: Capillary Break-up Extensional Rheometrymentioning

confidence: 99%

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Extensional rheometry of cellulose ether solutions: flow instability

Vadodaria

English

2015

Cellulose

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Capillary breakup extensional rheometry of semi-dilute hydroxyethyl cellulose (HEC) solutions was performed under several step-stretch conditions. The resulting parameters, i.e. terminal steady state extensional viscosity (g E ) and the timescale for viscoelastic stress growth, commonly referred to as the extensional relaxation time (k E ) were found to be sensitive to the step-stretch conditions. The k E decreased with increasing step-strain as opposed to the g E . Prior to the filament break-up, a 'bead-onstring' instability was observed close to the mid-plane. It is believed that this instability originated from the accumulation of viscoelastic stresses near the filament neck leading to the 'elastic recoil' of the extended polymer chains. The reasons for this belief are discussed in detail with the perspective of the past literature. Such type of flow instability has been reported for the first time for a cellulosic system. Various dimensionless numbers were plotted for the HEC solutions and compared with those obtained from past studies for various biopolymers as well as synthetic polymers.

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“…In figure 10 we show representative transient profiles of the mid plane radius R t mid a f obtained numerically from equations (7), (8) It is also possible to obtain a closed form solution for combined evaporation and Newtonian capillary thinning by assuming the filament shapes shown in figure 8 can be approximated as axially uniform cylindrical threads held between large quasi-static or stagnant drops (or "blobs") and then following the analysis of Entov & Hinch (1997).…”

Section: Newtonian Modelmentioning

confidence: 99%

Using filament stretching rheometry to predict strand formation and "processability" in adhesives and other non-Newtonian fluids

Tripathi¹,

Whittingstall²,

McKinley³

2000

Rheologica Acta

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The spinning of polymeric fibers, the processing of numerous foodstuffs and the peel & tack characteristics of adhesives is associated with the formation, stability and, ultimately, the longevity of thin fluid 'strands'. This tendency to form strands is usually described in terms of the tackiness of the fluid or by heuristic concepts such as 'stringiness' [Lakrout et al., J. Adhesion 69, 307 (1999)]. The dynamics of such processes are complicated due to spatially and temporally non-homogeneous growth of extensional stresses, the action of capillary forces and the evaporation of volatile solvents. We describe the development and application of a simple instrument referred to as a microfilament rheometer (MFR) that can be used to readily differentiate between the dynamical response of different pressure-sensitive adhesive fluid formulations. The device relies on a quantitative observation of the rate of extensional thinning or 'necking' of a thin viscous or viscoelastic fluid filament in which the solvent is free to evaporate across the free surface. This high-resolution measurement of the radial profile provides a direct indication of the ultimate time to break-up of the fluid filament. This critical time is a sensitive function of the rheological properties of the fluid and the mass transfer characteristics of the solvent, and can be conveniently reported in terms of a new dimensionless quantity we refer to as a Processability parameter P. We demonstrate the usefulness of this technique by presenting our results in the form of a case study in which we measure the visco-elasto-capillary thinning of slender liquid filaments for a number of different commercial polymer/solvent formulations and relate this to the reported processing performance of the materials. We also compare the MFR observations with the prediction of a simple 1D theory derived from the governing equations that model the capillary thinning of an adhesive filament.

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Effect of a spectrum of relaxation times on the capillary thinning of a filament of elastic liquid

Cited by 387 publications

References 2 publications

Constant force extensional rheometry of polymer solutions

Constant force extensional rheometry of polymer solutions

Extensional rheometry of cellulose ether solutions: flow instability

Using filament stretching rheometry to predict strand formation and "processability" in adhesives and other non-Newtonian fluids

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