Investigation of the elongational behavior of polymer solutions by means of an elongational rheometer

Stelter, M.; Brenn, Günter; Yarin, Alexander L.; Singh, R. P.; Durst, F.

doi:10.1122/1.1445185

Cited by 111 publications

(138 citation statements)

References 20 publications

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“…Several recent experimental studies of low viscosity elastic solutions in the capillary-thinning device, such as those of Stelter et al 28,29 and Bazilevskii et al 30 , have provided much needed insight into the dynamics of breakup of thin polymeric filaments. In contrast to the very viscous fluids studied by Anna and McKinley 26 , an initial high rate of filament thinning was observed in the lower viscosity solutions and was attributed to a balance between inertial and capillary effects, with elastic stress being unimportant in this region 30 .…”

Section: Introductionmentioning

confidence: 99%

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

2006

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The dynamics of drop formation and pinch-off have been investigated for a series of low viscosity elastic fluids possessing similar shear viscosities, but differing substantially in elastic properties. On initial approach to the pinch region, the viscoelastic fluids all exhibit the same global necking behavior that is observed for a Newtonian fluid of equivalent shear viscosity. For these low viscosity dilute polymer solutions, inertial and capillary forces form the dominant balance in this potential flow regime, with the viscous force being negligible. The approach to the pinch point, which corresponds to the point of rupture for a Newtonian fluid, is extremely rapid in such solutions, with the sudden increase in curvature producing very large extension rates at this location. In this region the polymer molecules are significantly extended, causing a localized increase in the elastic stresses, which grow to balance the capillary pressure. This prevents the necked fluid from breaking off, as would occur in the equivalent Newtonian fluid. Alternatively, a cylindrical filament forms in which elastic stresses and capillary pressure balance, and the radius decreases exponentially with time. A (0+1)-dimensional finitely extensible nonlinear elastic dumbbell theory incorporating inertial, capillary, and elastic stresses is able to capture the basic features of the experimental observations. Before the critical “pinch time” tp, an inertial-capillary balance leads to the expected 2∕3-power scaling of the minimum radius with time: Rmin∼(tp−t)2∕3. However, the diverging deformation rate results in large molecular deformations and rapid crossover to an elastocapillary balance for times t>tp. In this region, the filament radius decreases exponentially with time Rmin∼exp[(tp−t)∕λ1], where λ1 is the characteristic time constant of the polymer molecules. Measurements of the relaxation times of polyethylene oxide solutions of varying concentrations and molecular weights obtained from high speed imaging of the rate of change of filament radius are significantly higher than the relaxation times estimated from Rouse-Zimm theory, even though the solutions are within the dilute concentration region as determined using intrinsic viscosity measurements. The effective relaxation times exhibit the expected scaling with molecular weight but with an additional dependence on the concentration of the polymer in solution. This is consistent with the expectation that the polymer molecules are in fact highly extended during the approach to the pinch region (i.e., prior to the elastocapillary filament thinning regime) and subsequently as the filament is formed they are further extended by filament stretching at a constant rate until full extension of the polymer coil is achieved. In this highly extended state, intermolecular interactions become significant, producing relaxation times far above theoretical predictions for dilute polymer solutions under equilibrium conditions.

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Section: Introductionmentioning

confidence: 99%

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

2006

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“…10,16,17 It is very hard to quantitatively evaluate this property for dilute polymer solutions using other techniques; 18 however, monitoring the slow capillary drainage and ultimate rupture of a necking fluid thread can provide a suitable way of measuring this elusive material function. 3,12,19 Recent numerical simulations have also demonstrated the evolution and the interaction of multiple beads on a viscoelastic thread. The slow drainage of fluid into the beads results in small, but nonzero, axial variations in the radii of the slender filaments between the beads.…”

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confidence: 99%

Iterated stretching and multiple beads-on-a-string phenomena in dilute solutions of highly extensible flexible polymers

2005

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A new instrument for dynamic helical squeeze flow which superposes oscillatory shear and oscillatory squeeze flow Rev. Sci. Instrum. 83, 085105 (2012) The effects of hydrodynamic interaction and inertia in determining the high-frequency dynamic modulus of a viscoelastic fluid with two-point passive microrheology Phys. Fluids 24, 073103 (2012) MHD free convection flow of a visco-elastic (Kuvshiniski type) dusty gas through a semi infinite plate moving with velocity decreasing exponentially with time and radiative heat transfer AIP Advances 1, 022132 (2011) Transitional flow of a non-Newtonian fluid in a pipe: Experimental evidence of weak turbulence induced by shearthinning behavior Phys. Fluids 22, 101701 (2010) Effects of viscoelasticity on the probability density functions in turbulent channel flow

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“…Even though the exponential thinning continues indefinitely in the numerical simulations, in practice the finite extensibility of polymer chains limits the elastocapillary stress growth (Stelter et al 2002). The polymer coils, undergoing strong deformation, get stretched during the extensional flow and induce localized anisotropy in the microstructure at the midfilament.…”

Section: Capillary Break-up Extensional Rheometrymentioning

confidence: 99%

“…Nevertheless, rheologically important parameters such as stress, strain and strain rate can indeed be calculated by observing the temporal evolution of filament diameter with time and the value of surface tension by means of the following equations suggested by the past literature pioneering experimental development of the technique Anna and McKinley 2001;Stelter et al 2002;Kolte and Szabo 1999).…”

Section: Capillary Break-up Extensional Rheometrymentioning

confidence: 99%

“…Boger fluids (Plog et al 2005;Campo-Deano et al 2011;Anna and McKinley 2001), and yield stress fluids (McKinley 2005a, b;Niedzwiedz et al 2009) CaBER measurements for a number of systems containing biopolymers and their derivatives in aqueous media have been reported in the past literature, most notably for xanthan (Stelter et al 2002), hydroxypropyl ether guar (Duxenneuner et al 2008), methyl hydroxyethyl cellulose (HEC) (Plog et al 2005), alginate (Storz et al 2010;Rodriguez-Rivero et al 2014), scleroglucan (Japper-Jaafar et al 2009), cellulose acetate ? PEO solutions (Chen et al 2008), cellulose in an ionic liquid 1-ethyl-3-methylimidazolium acetate (Haward et al 2012) (Michud et al 2015), DNA (Chevallier 2009), cornstarch-water suspension (Bischoff White et al 2010), galactomannan (Bourbon et al 2010), casein/waxy maize starch (Chan et al 2009) and dilute ethyl HEC solutions (Sharma et al 2015).…”

Section: Introductionmentioning

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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Investigation of the elongational behavior of polymer solutions by means of an elongational rheometer

Cited by 111 publications

References 20 publications

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

Iterated stretching and multiple beads-on-a-string phenomena in dilute solutions of highly extensible flexible polymers

Extensional rheometry of cellulose ether solutions: flow instability

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