How polymeric solvents control shear inhomogeneity in large deformations of entangled polymer mixtures

Ravindranath, Sham S.; Wang, Shi‐Qing; Olechnowicz, Michael; Chavan, Vijay; Quirk, Roderic P.

doi:10.1007/s00397-010-0507-0

Cited by 29 publications

(28 citation statements)

References 51 publications

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“…The Rolie-poly model thus predicts transient banding as the sample relaxes back to equilibrium after a rapid strain ramp. This is consistent with early theoretical intuition [88], and with experimental observations in polymers [89][90][91][92][93][94][95][96] and wormlike micelles [25].…”

Section: Rapid Finite Strain Rampsupporting

confidence: 92%

Triggers and signatures of shear banding in steady and time-dependent flows

Fielding¹

2016

Journal of Rheology

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThis pr ecis is aimed as a practical field guide to situations in which shear banding might be expected in complex fluids subject to an applied shear flow. Separately for several of the most common flow protocols, it summarizes the characteristic signatures in the measured bulk rheological signals that suggest the presence of banding in the underlying flow field. It does so both for a steady applied shear flow and for the time-dependent protocols of shear startup, step stress, finite strain ramp, and large amplitude oscillatory shear. An important message is that banding might arise rather widely in flows with a strong enough time dependence, even in fluids that do not support banding in a steadily applied shear flow. This suggests caution in comparing experimental data with theoretical calculations that assume a homogeneous shear flow. In a brief postlude, we also summarize criteria in similar spirit for the onset of necking in extensional filament stretching. V C 2016 The Society of Rheology.[http://dx

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Section: Rapid Finite Strain Rampsupporting

confidence: 92%

Triggers and signatures of shear banding in steady and time-dependent flows

Fielding¹

2016

Journal of Rheology

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“…In contrast to the methods that detect the structures of materials, some other methods have been utilized to determine the velocity profile inside the various geometries in a rotational rheometer. These methods include particle tracking velocimetry (PTV) (35,(37)(38)(39)(40)(41)(42), (44,45), particle image velocimetry (20), (22,23), ultrasonic velocimetry (21,31), dynamic light scattering (17,36), a confocal laser scanning microscope (32,33), nuclear magnetic resonance (19), and magnetic resonance imaging (24)(25)(26)(27)(28)(29). Schematics of rheo-PTV are shown in Figure 37, where the movements of tracing particles in the fluid are recorded by a camera from which the local velocity can be determined.…”

Section: Transient Shearmentioning

confidence: 99%

Rheological Measurements

2013

Encyclopedia of Polymer Science and Technology

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Rheology is the science to study the flow and deformation of matter. It becomes an important field in material science and engineering, food, biotechnology, and so on. The objects in rheological study are not the ideal solid and ideal fluid, which can be described by the Hookean elastic model and the Newtonian viscous model, respectively. Instead, the rheological study often focuses on materials that can exhibit viscous, elastic, and plastic behavior under different flow conditions. They are often termed as complex fluids or soft matter, which include polymers, gels, suspensions, emulsions, biofluids, foods, inks (1). In contrast to hydrodynamics, which often accounts for the complex flow behavior of simple fluids, simple geometry is utilized in rheological measurements to understand the rather complicated relationship between the mechanical input and output of complex fluids. The real flow fields encountered in many applications (such as polymer extrusion, injection molding, blow molding, fiber spinning, inkjet printing, coating) are rather complicated (2). It becomes a problem whether the rheological measurements that performed under simple flow fields are useful in understanding the complicated flow behaviors of complex fluids. Fortunately, it has been proved in many examples that the properties determined from simple rheological measurements are sufficient to quantify the material parameters in various constitutive equations, which have been used widely and successfully to simulate the flow behaviors in polymer processing (3-11). The most frequently used simple flow fields are simple shear flow and simple extensional flow.The simplest geometry that defines the simple shear is two infinite parallel plates separated by a distance h. The liquid is set between two plates with one plate moving parallel to the other (Fig. 1). In reality, when the length L and the width B are much larger than the gap h, the flow in the center regime resembles the flow between two infinite plates. It means that the edge effects are ignored in most experimental shear geometries. In rheological measurements, the flow between two plates should be laminar. Moreover, it is usually assumed that the velocity across the gap satisfies a linear profile. As shown in Fig. 1, if the bottom plate is fixed and the upper plate moves horizontally with the velocity V, the fluid velocity varies linearly from 0 at the bottom plate to V at the upper plate if the no-slip boundary condition is satisfied. The linear velocity profile generates a constant velocity gradient, which is known as the shear rate. Then, the flow field between two parallel plates is homogeneous in the shear rate. The homogeneous assumption is nontrivial in the rheological tests since the actual velocity

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“…Specifically, Hu seemed to be puzzled by the fact the 1M(10%)-9K solution developed shear banding in the conventional cone-plate (CP) geometry ], whereas the 1M(10%)-15K solution always appeared to be homogeneous in the CPP ]. Our recent studies ; Ravindranath et al (2011);Wang et al (2011)] have demonstrated that solvents play a crucial role in the formation of shear bands by regulating the value of the extrapolation (slip) length b. As already explained by , 1M(10%)-15K has significantly lower b, and a monolayer of chain disentanglement in the bulk or at the sample/wall interface would therefore produce little correction to the initial homogeneous shear field.…”

Section: Role Of Solvent In Shear Bandingmentioning

confidence: 74%

Letter to the editor: Cone partitioned plate (CPP) vs circular couette

Ravindranath¹,

Wang²,

Boukany³

et al. 2012

Journal of Rheology

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SynopsisIn geometries capable of producing uniform shear stress across the gap such as cone-plate, it is a challenge to study the nonlinear rheology of well-entangled polymers without wall slip and edge fracture. The task to obtain meaningful steady-state information is particularly daunting. Significant insights are required in the design of experiments and choice of reliable apparatuses that could fulfill the objective to determine the constitutive behavior. In a recent published article, Hu J. Rheol. 54, 1307-1323 (2010) reported particle-imaging velocimetric measurements of two highly entangled polybutadiene solutions with a cocylinder geometry. One of the solutions was prepared and provided to Hu by Ravindranath from the University of Akron. Rheological and particletracking velocimetric studies have been carried out on the same sample in our laboratory. In this letter, we will compare Hu's results with our own measurements, clarify a few misrepresentations, and discuss several important issues concerning shear banding in entangled polymers. V C 2012 The Society of Rheology. [http://dx.

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How polymeric solvents control shear inhomogeneity in large deformations of entangled polymer mixtures

Cited by 29 publications

References 51 publications

Triggers and signatures of shear banding in steady and time-dependent flows

Triggers and signatures of shear banding in steady and time-dependent flows

Rheological Measurements

Letter to the editor: Cone partitioned plate (CPP) vs circular couette

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