Shear flow properties of concentrated solutions of linear and star branched polystyrenes

Yasuda, Katsutaro; Armstrong, Robert C.; Cohen, Robert E.

doi:10.1007/bf01513059

Cited by 624 publications

(366 citation statements)

References 18 publications

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“…In 1981 Yasuda carried out an extensive study of the shear thinning of solutions of polystyrene polymer solutions and suggested a modification to the Carreau equation to improve its fit in the transition region between Newtonian and strong shear thinning [82]. This has the form; According to Bair, from thermodynamic arguments  o can be equated to N v kT where N v is the number of molecules per unit volume [83].…”

Section: Carreau and Yasudamentioning

confidence: 99%

History, Origins and Prediction of Elastohydrodynamic Friction

2014

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There is currently considerable debate concerning the most appropriate rheological model to describe the behaviour of lubricant films in rolling-sliding, elastohydrodynamic contacts. This is an important issue since an accurate model is required in to predict friction in such contacts. This paper reviews the origins of this debate, which primarily concerns a divergence of views between researchers using high pressure, high shear rate viscometry and those concerned with the measurement and analysis of elastohydrodynamic friction; the former advocate a Carreau-based shear stress/strain rate model while the latter generally favour an Eyring-based one. The crucial importance of accounting for shear heating effects in analysing both viscometric and friction data is discussed. The main criticisms levied by advocates of a Carreau-based model against Eyring's model are discussed in some detail. Finally the ability of both types of rheological model to fit elastohydrodynamic friction measurements for a quite simple, well-defined base fluid is tested, using previously-measured pressure-viscosity behaviour for the fluid. Both models appear to fit the experimental data over a wide temperature range quite well, though fit of the Eyring model appears slightly closer than that of the Carreau-Yasuda model. Friction data from a wider range of welldefined fluid types is needed to identify categorically the most appropriate model to describe elastohydrodynamic friction.

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Section: Carreau and Yasudamentioning

confidence: 99%

History, Origins and Prediction of Elastohydrodynamic Friction

2014

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“…Bellow a critical shear rate the viscosity tends to approach an asymptotic value, which is the maximum viscosity or zero-shear-rate viscosity,  o . Therefore, the equilibrium viscosity as a function of shear rate can be calculated from the generalized Cross-Carreau model [13][14]:…”

Section: Theorymentioning

confidence: 99%

A simple model to describe the thixotropic behavior of paints

Armelín¹,

Martí²,

Rudé³

et al. 2006

Progress in Organic Coatings

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We propose a simple rheological model to describe the thixotropic behavior of paints, since the classical hysteresis area, which is usually used, is not enough to evaluate thixotropy. The model is based on the assumption that viscosity is a direct measure of the structural level of the paint. The model depends on two equations: the Cross-Carreau equation to describe the equilibrium viscosity and a second order kinetic equation to express the time dependence of viscosity. Two characteristic thixotropic times are differentiated: one for the net structure breakdown, which is defined as a power law function of shear rate, and an other for the net structure buildup, which is not dependent on the shear rate. The knowledge of both kinetic processes can be used to improve the quality and applicability of paints. Five representative commercial protective marine paints are tested. They are based on chlorinated rubber, acrylic, alkyd, vinyl, and epoxy resins. The temperature dependence of the rheological behavior is also studied with the temperature ranging from 5 ºC to 35 ºC. It is found that the paints exhibit both shear thinning and thixotropic behavior. The model fits satisfactorily the thixotropy of the studied paints. It is also able to predict the thixotropy dependence on temperature. Both viscosity and the degree of thixotropy increase as the temperature decreases.

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“…is obeyed by many polymeric melts (Booij et al 1983, Cox and Merz 1958, Dealy and Larson 2006, Kulicke and Porter 1980, Laun 1986, Winter 2009) and concentrated polymer solutions (Al-Hadithi et al 1992, Kulicke and Porter 1980, Laun 1986, Yasuda et al 1981) with a wide range of chemical structures and molecular weight. The Cox-Merz rule establishes a connection between the complex viscosity η * ω ( )measured in an oscillatory frequency sweep (at a fixed strain amplitude within the linear viscoelastic regime) and the steady shear viscosity η  γ ( ) = σ  γ measured as a function of shear rate  γ .…”

Section: Introduction: the Cox-merz Rule And Laun's Rulementioning

confidence: 99%

An intriguing empirical rule for computing the first normal stress difference from steady shear viscosity data for concentrated polymer solutions and melts

Sharma

McKinley

2012

Rheol Acta

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The Cox-Merz rule and Laun's rule are two empirical relations that allow the estimation of steady shear viscosity and first normal stress difference respectively using small amplitude oscillatory shear measurements. The validity of the Cox-Merz rule and Laun's rule imply an agreement between the linear viscoelastic response measured in small amplitude oscillatory shear and the nonlinear response measured in steady shear flow measurements. We show that by using a lesser known relationship also proposed by Cox and Merz, in conjunction with Laun's rule, a relationship between the rate-dependent steady shear viscosity and the first normal stress difference can be deduced. The new empirical relation enables a priori estimation of the first normal stress difference using only the steady flow curve (i. e. viscosity vs shear rate data). Comparison of the estimated first normal stress difference with the measured values for six different polymer solutions and melts show that the empirical rule provides values that are in reasonable agreement with measurements over a wide range of shear rates; thus deepening the intriguing connection between linear and nonlinear viscoelastic response of polymeric materials.2

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Shear flow properties of concentrated solutions of linear and star branched polystyrenes

Cited by 624 publications

References 18 publications

History, Origins and Prediction of Elastohydrodynamic Friction

History, Origins and Prediction of Elastohydrodynamic Friction

A simple model to describe the thixotropic behavior of paints

An intriguing empirical rule for computing the first normal stress difference from steady shear viscosity data for concentrated polymer solutions and melts

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