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Ulrich A. Handge
Rheologentagung 2007
Appl. Rheol. 17:4 (2007) 230-231 ►
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Handge UA: Rheologentagung 2007, Appl. Rheol. 17 (2007) 230.
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Coussot P, Barrat J: Flow in Glassy Systems. European School of Rheology, Appl. Rheol. 17 (2007) 228.John Embery
A Feast of Polymer Physics
Appl. Rheol. 17:4 (2007) 226-227 ►
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Embery J: A Feast of Polymer Physics , Appl. Rheol. 17 (2007) 226.
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Rheological Societies: Society's Site Sep 2007 - Feb 2008, Appl. Rheol. 17 (2007) 238.
Rheo-optics is a method that allows the analysis of optical properties, like birefringence and dichroism under steady and oscillatory shear. It is possible to correlate macroscopic mechanical responses with induced microscopic changes in the material. We describe how this method was improved several fold and implemented on a commercially available setup. However, the here presented ideas are applicable to any rheo-optical setup, based on modulation of the laser light. Additionally it does not need a lock-in amplifier and therefore reduces the costs of the setup.► Cite this publication as follows:
Klein C, Venema P, Sagis L, vanDusschoten D, Wilhelm M, Spiess HW, vanderLinden E, Rogers SS, Donald AM: Rheo-optical Measurements using Fast Fourier Transform and Oversampling, Appl. Rheol. 17 (2007) 45210.
Rheological and mechanical properties of acrylonitrile-butadiene-styrene polymers (ABS) prepared via bulk polymerization depending on the molecular weight (Mw) of styrene-acrylonitrile copolymer (SAN) have been investigated.The tendencies of attaining the yield stress at steady-state shear flow and approaching to the .plateau. region of storage modulus at low frequencies in oscillatory tests were observed. Both these phenomena are induced by formation of the structural skeleton consisting of polybutadiene (PB) particles arranged in the SAN-matrix. Growth of Mw of SAN leads both to increase of the .plateau. value of storage modulus at low frequencies and the yield stress.This fact can be explained by the influence of Mw of SAN chains grafted onto PB particles on structure formation in ABS melts because of a redistribution of the ratio particleparticle / particle-matrix interactions. The elongational viscosity of ABS melts is a power function of Mw of SAN matrix. The power index of this function increases with the polymer straining that reflects orientation of SAN chains with their length increase. The strain-hardening index of ABS melts increases considerably with increase of SAN matrix Mw. However, it does not depend on presence of PB particles in the material. It means that the value of this index is governed by orientation effect in the SAN matrix.The impact strength of the investigated ABS samples is interrelated with rheological characteristics of ABS melts as well as Mw of SAN. The dependence of impact strength on Mw can be explained by increasing role of orientation effects of SAN chains with Mw increase in the copolymer fibrils connecting the walls of crazes formed at impact action.► Cite this publication as follows:
Dreval VE, Vasilev G, Borisenkova E, Semakov A, Kulichikhin VG: Influence of Molecular Weight of SAN on Rheological and Mechanical Properties of ABS-plastics, Appl. Rheol. 17 (2007) 44745.
Nowadays it is necessary to perform experimental measurements to compare with numerical calculations. In this study we focus on different aqueous solutions which are tested to obtain in the same time a rheological blood like fluid and particular optical properties for laser measurements (particle image velocimetry (PIV) or laser Doppler velocimetry (LDV)). Using viscometric tests we show that the non Newtonian behavior of blood is reached by adding xanthan gum in aqueous glycerol and aqueous potassium thiocyanate solutions. Optical properties are directly achieved by modifying glycerol or thiocyanate potassium concentrations. Indeed we proove using refractometric measurements that the addition of xanthan gum does not affect the value of the refractive indexes. Finally,we can prepare an optical blood like fluid adapted to cardiovascular studies by adjusting the proportion of the different components.► Cite this publication as follows:
Benard N, Jarny S, Coisne D: Definition of an experimental blood like fluid for laser measurements in cardiovascular studies., Appl. Rheol. 17 (2007) 44251.
Consideration is given to the reaction to Barnes and Walters' 4-page The yield stress myth? paper published 21 years ago. It has been cited approximately 180 times since then, as either a standard reference for 'yield stress' papers, or to disagree with its sentiment that yield stresses do not actually exist, but are a useful approximation. The references that cite the paper are categorized and commented on.► Cite this publication as follows:
Barnes HA: The 'Yield stress myth?' paper - 21 years on, Appl. Rheol. 17 (2007) 43110.
The concentration and size dependencies of elastic properties of highly concentrated w/o emulsions were studied. The range of weight concentration of the disperse phase was 90 - 96%, the range of the average droplet size was 16 - 20 μm, and the droplet size distribution remained unchanged. The disperse phase consists of droplets of over-cooled concentrated aqueous solutions of inorganic salts. The concentration range being studied lies above the limit of maximal close packing, φ > φm. The droplet size distribution is fairly wide and the shape of droplets is polygonal.These factors alone determine possible new rheological effects, such as the elasticity and visco-plastic behaviour of emulsions, as well as the observed form of concentration and size dependencies of rheological properties of emulsions. The complete flow curves were measured for these fairly new emulsion systems. It emerged that they were similar to the entire concentration and droplet size ranges being studied. The concentration dependencies of the yield stress and storage modules corresponded to the Princen-Kiss theory with critical volume concentration approximately 0.71 - 0.74. However, this theory describes the size dependence of elastic modules incorrectly. A new model is proposed, which correctly describes the dependencies of elastic modules on both determining parameters - those of concentration and droplet size.► Cite this publication as follows:
Masalova I, Malkin AY: Rheology of highly concentrated emulsions - concentration and droplet size dependencies, Appl. Rheol. 17 (2007) 42250.
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