Thixotropic Behavior of Oils

Weltmann, Ruth N.

doi:10.1021/i560119a003

Cited by 38 publications

(14 citation statements)

References 8 publications

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“…Equation 7 expressed in terms of stress decay becomes where vy is the rate of thixotropic breakdown. Hahn et al (1959) reworked the data of Weltmann (1943b) and found plots of 7 versus In t for the mineral oil to be sigmoidal and not linear. They argued on theoretical grounds that stress decay of thixotropic substances should instead follow the first-order type relationship…”

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confidence: 99%

Characterization of Structure Breakdown of Foods From Their Flow Properties

Figoni

Shoemaker

1981

Journal of Texture Studies

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Advances in the characterization of the complex time‐dependent flow properties of liquids and semisolids are reviewed, with special emphasis placed on recent developments in elucidating the behavior of food systems when sheared. Time dependency is discussed in terms of viscoelasticity and structural changes. Systems as diverse as mineral oils, lotions and creams, egg custards, and mayonnaise are shown to exhibit a similar stress decay over time when sheared at a constant rate. Various mathematical descriptions, both theoretical and empirical, are used to characterize the stress decay, which is due to structural changes (e.g. thixotropy) that occur within the system as it is sheared. Evidence is provided that the stress decay varies with product formulation and experimental conditions, such as temperature, shear rate, and viscometer gap width. A discussion of the uses and disadvantages of steady shear measurements is included.

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confidence: 99%

Characterization of Structure Breakdown of Foods From Their Flow Properties

Figoni

Shoemaker

1981

Journal of Texture Studies

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“…This does not seem to be a particularly useful approach. Equation (3) shows that at a given concentration and temperature, the viscosity depends on <I> and A. Both <I> and A depend in turn on the aggregate size distribution nj(t).…”

Section: Discussionmentioning

confidence: 99%

Structure of Thixotropic Suspensions in Shear Flow. III. Time-Dependent Behavior

Mercer

Weymann

1974

Transactions of the Society of Rheology

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SynopsisThe time-dependent viscosity of bentonite-water suspensions was studied experimentally in COllette flow for various transitions between constant shear rates. It was found that, after a sudden change in the shear rate the time dependence of the viscosity can be described by .,,(1) = A exp [-(t/TJ) 4°1 + B exp (-t/T,) + C, with T, > r i-In general, the characteristic times: 1) become longer as the differences in shear rates become smaller; 2) decrease with increasing concentration; 3) show little temperature effect for a 20°C temperature change. A theory for the time-dependent behavior is given which can reproduce the essential features of the experimental results.

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“…This threshold shear stress is called the yield stress of the fluid. The behavior of Bingham plastic fluid can be mathematically expressed by Equation 3: [3] where τ o = the Bingham yield stress (Pa) and η p = the Bingham plastic consistency coefficient (Pa·s).…”

Section: Methodsmentioning

confidence: 99%

“…Crude oil may be considered a structured disperse system because the complex mixture of liquid hydrocarbon derivatives acts as a dispersion medium and the aggregated impurities make up the dispersed phase. The impurities of crude oils influence flow characteristics and determine their non-Newtonian properties (3). The power law model has been used to describe flow properties of liquid-based food products.…”

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confidence: 99%

Effects of purification process on rheological properties of catfish oil

Sathivel

Prinyawiwatkul

King

et al. 2003

J Americ Oil Chem Soc

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Effects of oil refining steps (degumming, neutralizing, bleaching, and deodorizing) on rheological properties of catfish oil were investigated. Four rheological models (Newtonian, Bingham, Herschel-Bulkley, and Casson) were used to fit the experimental data. Refined catfish oil behaves like a Newtonian fluid. Based on the Casson model, the yield stress values of oils gradually decreased after each refining step. The highest shear rate index (0.904) was observed in the deodorized oil. The Casson model was used to predict rheological properties because it works well at both lower and higher shear rates.

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Thixotropic Behavior of Oils

Cited by 38 publications

References 8 publications

Characterization of Structure Breakdown of Foods From Their Flow Properties

Characterization of Structure Breakdown of Foods From Their Flow Properties

Structure of Thixotropic Suspensions in Shear Flow. III. Time-Dependent Behavior

Effects of purification process on rheological properties of catfish oil

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