Shear and extensional investigations in solutions of grafted/ungrafted amylopectin and polyacrylamide

Stelter, M.; Wunderlich, Thomas; Rath, Sangram K.; Brenn, Günter; Yarin, Alexander L.; Singh, R. P.; Durst, F.

doi:10.1002/(sici)1097-4628(19991209)74:11<2773::aid-app25>3.0.co;2-9

Cited by 23 publications

(19 citation statements)

References 18 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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“…STELTER et al [5] and WUNDERLICH et al [6] described the simple principle of the CaBER. A small quantity of sample (less than 0.2 mL) was placed between two parallel plates (6 mm in diameter).…”

Section: Measurement Of Extensional Breakup Timementioning

confidence: 99%

Viscoelasticity of mixed polyacrylamide solution

2008

J. Cent. South Univ. Technol.

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The viscoelastic behavior of polyacrylamide solution is crucial for its application in various industries. The mixed polyacrylamide solution was prepared by mixing polyacrylamide with different relative molecular masses according to the defined mass fraction. The viscosity and elasticity of mixed polyacrylamide solution were separately tested with RS150 rheometer and capillary breakup extensional rheometer and compared with those of the single polyacrylamide solution which is directly provided by manufacturer without any mixing. The results indicate that the mixed and single polyacrylamide solutions have the same shear viscosity and intrinsic viscosity. However, some mixed polyacrylamide solutions have higher elasticity than single polyacrylamide solution. The flow resistance of mixed polyacrylamide with higher elasticity is also greater than that of single polyacrylamide solution in porous medium. This paper presents an effective method of mixing polyacrylamides with different relative molecular masses, which can enhance the elasticity of polyacrylamide solution and flowing resistance through porous medium.

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“…[3,5,6] While droplet size is predominantly affected by nozzle selection, [4] polymer adjuvants used in dilute concentration can also strongly affect droplet size and jet breakup. [7] Additionally, these rheology-modifying additives have application in other areas including enhanced oil recovery (EOR), [8] drag reduction in pipelines, [9] cosmetics and inkjet printing. [10,11] The enhanced extensional viscosity (or elasticity) of polymer solutions is believed to cause the larger drop size.…”

Section: Introductionmentioning

confidence: 99%

Polymeric Drift Control Adjuvants for Agricultural Spraying

Lewis

Evans

Malic

et al. 2016

Macro Chemistry & Physics

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---------The movement of a pesticide or herbicide to an off-target site during agricultural spraying can cause injury to wildlife, plants and contamination of surface water. This phenomenon is known as spray drift and can be controlled by spraying during favorable environmental conditions, and by using low drift nozzles and drift control adjuvants (DCAs). Polymeric DCAs are the most common type of DCA and function by increasing the droplet size produced during spraying. There are, however, two main drawbacks of polymeric DCAs; they are prone to mechanical degradation during spraying which reduces their performance and they can produce oversized drops which reduces the efficacy of the spray. In this review, existing DCA technology is reviewed including the mechanism through which they function.This then provides a platform for the discussion of novel polymeric architectures which have currently not been applied in DCA formulations.-2 -

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Shear and extensional investigations in solutions of grafted/ungrafted amylopectin and polyacrylamide

Cited by 23 publications

References 18 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

Viscoelasticity of mixed polyacrylamide solution

Polymeric Drift Control Adjuvants for Agricultural Spraying

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