Slip mechanisms in complex fluid flows

Hatzikiriakos, Savvas G.

doi:10.1039/c5sm01711d

Cited by 114 publications

(73 citation statements)

References 157 publications

(265 reference statements)

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“…This stronger bonding to the steel surface usually results in wall adherence. The measured rheological data revealed wall slip even at low wall shear stress values. Other authors , who observed different slip mechanisms reported the first appearance of wall slip after exceeding a critical wall shear stress value. Generally, the experimentally determined slip velocity data correlate well with the dependencies predicted with the presented slip model in this paper, which considers a lubricating film between the die wall and the polymer melt. The experimentally obtained slip velocity increases with rising wall shear stress. The presented slip model predicts a power law dependency on wall shear stress.…”

Section: Resultssupporting

confidence: 85%

Experimental study and modeling of wall slip of polymethylmethacrylate considering different die surfaces

Zitzenbacher

Huang

Holzer³

2017

Polymer Engineering & Sci

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Wall slip of polymethylmethacrylate (PMMA) was studied on different flow channel surfaces using a rheological slit die and a high pressure capillary rheometer. As die surfaces polished steel, ground steel, and Si doped Diamond like carbon (DLC) were used. A new wall slip model is presented in this paper which assumes a lubricating film between the polymer melt and the die surface. The slip velocity has a power law dependency on wall shear stress. In the double logarithmic plot the wall slip curves are linear and can be parallel shifted to higher values with increasing temperature. The predicted dependencies of the wall slip velocity could be confirmed with experiments conducted with PMMA on polished steel. Furthermore, the die surface influences the flow behavior of PMMA. No wall slip was found on ground steel and on DLC. No complete film could be established by the lubricant on the ground steel die wall. The DLC‐coating exhibits a similar surface roughness and surface energy to polished steel, but the chemical composition is different. It is a metastable form of amorphous carbon containing sp2 and sp³ bonds. As a consequence slip additives have a low ability to bond to this material. POLYM. ENG. SCI., 58:1391–1398, 2018. © 2017 Society of Plastics Engineers

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Section: Resultssupporting

confidence: 85%

Experimental study and modeling of wall slip of polymethylmethacrylate considering different die surfaces

Zitzenbacher

Huang

Holzer³

2017

Polymer Engineering & Sci

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“…This is also consistent with the theoretical picture of a coil-stretch transition of the adsorbed chains occurring at the first monolayer of adsorbed polymer chains on the surface, and nearest neighbours in the next layer remain in the coiled conformation and entangled with other bulk chains. 23,43,74 In addition, we find that the average conformation of immobile chains reaches a higher level of molecular extension at Wi ¼ 22.6, compared to Wi ¼ 5.6 on ATPES surfaces. At the same Wi ¼ 22.6 on a regular glass, the DNA molecules still contain a signature of the preponderance of the coil-sized chain configurations during flow.…”

Section: -7mentioning

confidence: 72%

“…Despite the relevance and importance of wall slip in polymer flow, the molecular mechanisms of wall slip remain poorly understood. 23 Both the microstructure and the origin of wall slip can vary significantly depending upon the nature of the interaction between the polymer chain and the solid surface. The main objective of this work is to fundamentally address the molecular mechanisms of slip of the entangled polymer at different surface conditions (with strong and weak interactions) in the strong flow regime.…”

Section: Introductionmentioning

confidence: 99%

“…Despite this large body of work based on velocimetry techniques, it is challenging to gain molecular insights into the nature of slip and understand its dependence on the wall properties. 23,61 Given the recent progress in biomicrofluidics, it is now possible to directly visualize the DNA conformation in different flow conditions by manipulating DNA molecules at micro-scale devices. 2,62,63,76 For instance, we have recently integrated a commercial rheometer with a confocal fluorescence microscope capable of capturing the conformation of individual DNAs during 044118-2 O. Hemminger and P. E. Boukany Biomicrofluidics 11, 044118 (2017) slip on an APTES-treated surface (with a strong interaction with DNA) in shear flow.…”

Section: Introductionmentioning

confidence: 99%

“…A full understanding of the molecular nature of slip is required to control processes in which complex flows play a role. 23 The entangled polymeric fluids provide perhaps the richest examples of the wall slip phenomenon among complex fluids 9,12 due to its wide practical applications in many fields such as coating, 24,25 polymer enhanced oil recovery, [26][27][28][29][30] mixing and extrusion, 31 lubrication in industrial or biological systems, 32,33 and lab-on-chip technologies. 2,[34][35][36][37] Many of these processes encountered in nature and industry involve the interaction of macromolecules with different surface environments (wall).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microscopic origin of wall slip during flow of an entangled DNA solution in microfluidics: Flow induced chain stretching versus chain desorption

Hemminger

Boukany

2017

Biomicrofluidics

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Despite the relevance and importance of slip, a fundamental understanding of the underlying molecular mechanisms of wall slip in polymer flow is still missing. In this work, we investigate the slip behavior of an entangled DNA solution at a molecular scale using a confocal microscope coupled to a microfluidic device. From microscopic measurement, we obtain both the velocity profile and conformation of polymeric chains by visualizing DNA molecules during flow on various surfaces (ranging from weak to strong interactions with DNA molecules). In channel flow at a low Weissenberg number (Wi = 0.14), we observe a parabolic flow for an APTES-treated glass (with strong interaction with DNA) in the absence of slip, while a significant amount of slip has been observed for a regular glass (with a weak interaction with DNA). At higher flow rates (Wi > 1.0), strong slip appears during flow on APTES-treated surfaces. In this case, only immobile DNA molecules are stretched on the surface and other bulk chains remain coiled. This observation suggests that the flow induced chain stretching at the interface is the main mechanism of slip during flow on strong surfaces. Conversely, for slip flow on surfaces with weak interactions (such as unmodified or acrylate-modified glasses), polymeric chains are desorbed from the surface and a thin layer of water is present near the surface, which induces an effective slip during flow. By imaging DNA conformations during both channel and shear flows on different surfaces, we elucidate that either chain desorption or flow-induced stretching of adsorbed chains occurs depending on the surface condition. In general, we expect that these new insights into the slip phenomenon will be useful for studying the biological flow involving single DNA molecule experiments in micro/nanofluidic devices.

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Macromolecular Rheology

Ruymbeke

Vlassopoulos

2022

Macromolecular Engineering

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One of the most important features of polymeric systems is their response to weak external stimuli. Of utmost importance is their reaction to an imposed mechanical load, which reflects their viscoelasticity. The viscoelastic properties of polymers are central to their handling and are responsible for their wide‐ranging applications. In this article, we provide the basic elements of molecular rheology, the science of deformation and flow of matter, which is necessary for understanding polymer viscoelasticity and linking it to molecular characteristics of the studied macromolecules. The presentation is basic and does not require prior knowledge on the topic. It refers to amorphous flexible polymers with emphasis on melts. First, the fundamental aspects of rheological measurements are discussed, followed by a discussion on linear viscoelasticity. Then, the models for the linear viscoelastic response of both unentangled and entangled polymers are presented in detail for different architectures, linear, star, and well‐characterized branched polymers. Subsequently, we focus on the nonlinear viscoelastic regime with particular emphasis on the current state‐of‐the‐art and remaining challenges. Where appropriate, some applications of interest to the industrial practice are briefly discussed. Nonlinear phenomena such as flow instabilities, flow‐induced crystallization, and wall slip are not covered.

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Slip mechanisms in complex fluid flows

Cited by 114 publications

References 157 publications

Experimental study and modeling of wall slip of polymethylmethacrylate considering different die surfaces

Experimental study and modeling of wall slip of polymethylmethacrylate considering different die surfaces

Microscopic origin of wall slip during flow of an entangled DNA solution in microfluidics: Flow induced chain stretching versus chain desorption

Macromolecular Rheology

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