Measuring the yield behaviour of structured fluids

Stokes, J. R. and Telford, J. H. (2004) Measuring the yield behaviour of structured fluids. Journal of Non-Newtonian Fluid Mechanics, 124 1-3: 137-146. doi:10.1016/j.jnnfm.2004.09.001


Author Stokes, J. R.
Telford, J. H.
Title Measuring the yield behaviour of structured fluids
Journal name Journal of Non-Newtonian Fluid Mechanics   Check publisher's open access policy
ISSN 0377-0257
Publication date 2004
Sub-type Article (original research)
DOI 10.1016/j.jnnfm.2004.09.001
Volume 124
Issue 1-3
Start page 137
End page 146
Total pages 10
Place of publication Amsterdam
Publisher Elsevier
Collection year 1970
Language eng
Subject 09 Engineering
Abstract Structured fluids or semi-solids, shear-thin dramatically at a critical shear stress and include household consumer products such as skin creams and lotions, sauces, pastes, spreads, mayonnaise, and ice cream. Such fluids also tend to be highly thixotropic so that theological measurements are often irreproducible due to the disruption of the microstructure during sample loading and dependence on measurement procedure. The use of a vane, consisting of four blades that form a cross shape at the end of a central shaft, inserted into the fluid is an easy and convenient method of performing accurate theology measurements on such samples. The vane enables the flow curves to be measured for structured fluids, which would otherwise be difficult or impossible to determine accurately using conventional techniques. Example studies have shown its particular usefulness in distinguishing crucial textural attributes of mayonnaise using a simple rapid test on the sample in the jar and enabled the yielding and flow behaviour of ice-slurries to be investigated at sub-zero temperatures. Accurate theological measurements would, in principle, allow the examination of structured fluids in terms of their underlying microstructure. However, due to the thixotropic nature of structured fluids, material properties such as the apparent yield stress are typically dependent on the test procedure. The effect of various test methodologies on the material properties of a lamellar gel network used to structure skin creams are compared, including test duration time for shear stress-sweep tests and the effect of shear rate in step-shear tests used for measuring a dynamic yield stress. The influence on the results using different test methodologies is discussed and how they can be related to one another. The results highlight the difficulty in choosing the most appropriate test procedure to give 'true' and accurate material properties for highly structured fluids. (C) 2004 Published by Elsevier B.V.
Keyword Yield stress
Rheometry
Vane
Structured fluid
Soft solid
Suspension
Emulsion
Microstructure
Cream
Lotion
Ice
Mayonnaise
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown
Additional Notes This paper was presented at a conference on Rheometry organised by the University of Wales Institute of Non-Newtonian Fluid Mechanics(UWINNFM) in April 2003. Author has requested that this record remain a journal article.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Chemical Engineering Publications
 
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Created: Wed, 01 Jul 2009, 16:05:17 EST