Continuous lubricated squeezing flow: A novel technique for equibiaxial elongational viscosity measurements on polymer melts

We briefly review the recent advances in the rheology of entangled polymers and identify emerging research trends and outstanding challenges, especially with respect to branched polymers. Emphasis is placed on the role of well-characterized model systems, as well as the synergy of synthesis-characterization, rheometry and modeling/simulations. The theoretical framework for understanding the observed linear and nonlinear rheological phenomena is the tube model, which is critically assessed in view of its successes and shortcomings, whereas alternative approaches are briefly discussed. Finally, intriguing experimental findings and controversial issues that merit consistent explanation, such as shear banding instabilities, multiple stress overshoots in transient simple shear and enhanced steady-state elongational viscosity in polymer solutions, are discussed, whereas future directions such as branch point dynamics and anisotropic monomeric friction are outlined.

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“…We do not discuss here the important but least developed area of controlled biaxial extension [106,107].…”

Section: Challengesmentioning

confidence: 99%

Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers

Snijkers

Pasquino

Olmsted

et al. 2015

J. Phys.: Condens. Matter

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“…Such lubricated squeezing devices have been demonstrated as effective biaxial extensional rheometers for relatively high-viscosity fluid samples such as polymer melts. 22,23 For the flow of shear-thinning fluids in squeeze flows, shear localization at the plate surfaces has a similar effect to partial slip at the surfaces. 24 Effectively the fluid self-lubricates, resulting in a more plug-like flow in the bulk and an increased dominance of extensional effects over shearing contributions to the flow in the region of the mid-plane between the plates.…”

mentioning

confidence: 99%

Extensional flow of hyaluronic acid solutions in an optimized microfluidic cross-slot device

et al. 2013

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We utilize a recently developed microfluidic device, the Optimized Shape Crossslot Extensional Rheometer (OSCER), to study the elongational flow behavior and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found in the knee joint. The OSCER geometry is a stagnation point device that imposes a planar extensional flow with a homogenous extension rate over a significant length of the inlet and outlet channel axes. Due to the compressive nature of the flow generated along the inlet channels, and the planar elongational flow along the outlet channels, the flow field in the OSCER device can also be considered as representative of the flow field that arises between compressing articular cartilage layers of the knee joints during running or jumping movements. Full-field birefringence microscopy measurements demonstrate a high degree of localized macromolecular orientation along streamlines passing close to the stagnation point of the OSCER device, while micro-particle image velocimetry is used to quantify the flow kinematics. The stress-optical rule is used to assess the local extensional viscosity in the elongating fluid elements as a function of the measured deformation rate. The large limiting values of the dimensionless Trouton ratio, Tr $ O(50), demonstrate that these fluids are highly extensional-thickening, providing a clear mechanism for the load-dampening properties of SF. The results also indicate the potential for utilizing the OSCER in screening of physiological SF samples, which will lead to improved understanding of, and therapies for, disease progression in arthritis sufferers. V C 2013 AIP Publishing LLC. [http://dx

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“…The CLSF technique involves compressing a sample between lubricated parallel plates . To avoid lubricant thinning, lubricant is continuously added to the films through porous plates connected to a syringe pump.…”

Section: Methodsmentioning

confidence: 99%

“…This ensures that the sample does not experience any shearing deformation and deforms in a purely extensional manner. A complete description of the technique can be found in the work by Venerus et al .…”

Section: Methodsmentioning

confidence: 99%

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Equibiaxial elongational viscosity measurements of commercial polymer melts

Mick

Shiu

Venerus

2014

Polymer Engineering & Sci

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The equibiaxial elongational viscosity of six commercially available polymer melts is measured using a novel technique known as continuous lubricated squeezing flow. This technique is a modification of simple lubricated squeezing flow. The systems were chosen in order to investigate the dependence of equibiaxial elongational viscosity on molecular structure. Three of the melts are polyethylene with long chain branching, two are polyethylene with short chain branching, and one is polyisobutylene with linear chains. Each polymer was subjected to strain rates ranging from 0.003 to 0.1 s−1 and compared to the linear viscoelastic prediction so that the degree of strain hardening could be determined. For a modestly branched polymer, comparison of rheological behavior in both uniaxial and equibiaxial deformations was possible. POLYM. ENG. SCI., 55:1012–1017, 2015. © 2014 Society of Plastics Engineers

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Continuous lubricated squeezing flow: A novel technique for equibiaxial elongational viscosity measurements on polymer melts

Cited by 27 publications

References 22 publications

Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers

Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers

Extensional flow of hyaluronic acid solutions in an optimized microfluidic cross-slot device

Equibiaxial elongational viscosity measurements of commercial polymer melts

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