Applied Rheology: Publications

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Francisco J. Galindo-Rosales
1st Summer School on Complex Fluid-Flows in Microfluidics (2017)

Appl. Rheol. 27:5 (2017) 46-47

Cite this publication as follows:
Galindo-Rosales FJ: 1st Summer School on Complex Fluid-Flows in Microfluidics (2017) , Appl. Rheol. 27 (2017) 46.

Martin Zatloukal
Novel Trends in Rheology VII

Appl. Rheol. 27:5 (2017) 51-54

Cite this publication as follows:
Zatloukal M: Novel Trends in Rheology VII, Appl. Rheol. 27 (2017) 51.

Daniel Svensek
10th Liquid Matter Conference (Liquids 2017)

Appl. Rheol. 27:5 (2017) 48-50

Cite this publication as follows:
Svensek D: 10th Liquid Matter Conference (Liquids 2017), Appl. Rheol. 27 (2017) 48.

Theau Conte, Rachid Bennacer, Mohend Chaouche
Thixotropic behavior of cement paste under large amplitude oscillatory shear

Appl. Rheol. 27:5 (2017) 53914 (9 pages)

Cement-based materials exhibit highly complex rheological properties, in particular yielding and thixotropy. These two properties can be characterized by considering rebuilding under a constant stress (creep) after shear at high rate. The rebuilding kinetics can be considered through the time evolution of the viscoelastic properties. However at the beginning of the rebuilding process the oscillatory behavior may be non-linear since the microstructure is destroyed by the shear flow. In the present investigation the rebuilding kinetics of cement pastes under oscillatory stress is considered through the transition from large amplitude oscillatory shear (LAOS) regime to small amplitude oscillatory shear (SAOS) regime. Three different cement paste mixes are considered: plain cement, nano-clay blended cement paste and cellulose ether blended cement paste. These three mixes are selected in order to deal with qualitatively different rheological properties.

Cite this publication as follows:
Conte T, Bennacer R, Chaouche M: Thixotropic behavior of cement paste under large amplitude oscillatory shear, Appl. Rheol. 27 (2017) 53914.

Johannes Nowak, Caroline Barhold, Christian Kessler, Stefan Odenbach
Gelation of a Nanocomposite-Hydrogel system and its dependency on mechanical loads

Appl. Rheol. 27:5 (2017) 52850 (6 pages)

Hydrogels are cross-linked polymer networks which are water-insoluble. They are suitable for several technical and biomedical applications due to the ability of some gels to swell and deswell as reaction to external stimuli. Such gels are synthesized and shift from a fluid-like liquid with solved components towards the final polymeric network with gel-like properties. Monitoring and characterizing this process is fundamental on the one hand to understand the chemical and physical behavior and on the other hand to adopt the application and production of such gels. Therefore, this investigation focuses on the characterization of the gelation of a nanocomposite hydrogel system based on PNIPAm with and without mechanical loads applied, using rheology. Measurements are conducted featuring rotational and oscillating rheometry and the results found are compared and evaluated. Furthermore the impact of a strong pre-shear, preventing the gelation, prior to the actual gelation, is investigated. The results found show a strong influence of the applied load as well as of an applied pre-shear on the gelation and furthermore on the mechanical properties of the final hydrogels. Therefore those parameters be taken into account for future investigations as well as for the large scale productions of hydrogels.

Cite this publication as follows:
Nowak J, Barhold C, Kessler C, Odenbach S: Gelation of a Nanocomposite-Hydrogel system and its dependency on mechanical loads, Appl. Rheol. 27 (2017) 52850.

Maryam Mudasir, Riaz Ahmed
An Explanation of Structure-Property Relationships for Polymer/Clay-Nanocomposites through Melt Flow Birefringence and Damping Function

Appl. Rheol. 27:5 (2017) 53700 (11 pages)

Rheological investigations are reported for pure polyolefin and its clay-nanocomposites to establish structure-properties relationship with respect to filler concentration. Flow birefringence is performed through an engineering geometry slit-die to obtain centerline principal stress difference during elongational flow. The centerline stress profile of clay-nanocomposite revealed additional viscoelastic nature even at low silicate concentrations whereas at the slit entrance no exceptional strain hardening was reported. Effects of higher filler concentrations are further examined during the simple shearing flow where non-terminal low frequency strain hardening only at maximum concentration of clay exhibited pseudo solid like response with improved dynamic moduli. The increase in damping coefficient with increasing clay concentration shows polymernanocomposites are more strain sensitive. The Wagner exponential damping function could adequately describe the timestrain separability at all clay concentrations studied. The results of this investigation reveal that the polymers are time-strain separable at all clay concentrations during elongational and simple shearing flows. But different molecular orientations are possible according to layers alignment along the flow direction.

Cite this publication as follows:
Mudasir M, Ahmed R: An Explanation of Structure-Property Relationships for Polymer/Clay-Nanocomposites through Melt Flow Birefringence and Damping Function, Appl. Rheol. 27 (2017) 53700.

Esteban F. Medina-Banuelos, Benjamin M. Marin-Santibanez, Jose Perez-Gonzales, Francisco Rodriguez-Gonzalez
Couette flow of a yield-stress fluid with slip as studied by Rheo-PIV

Appl. Rheol. 27:5 (2017) 53893 (11 pages)

The Couette flow of a model yield-stress fluid with slip at the walls, a 0.12% Carbopol® 940 microgel, was analyzed in this work by simultaneous rheometrical and particle image velocimetry measurements (Rheo-PIV). The Rheo-PIV technique was first tested in the analysis of the Couette flow of a Newtonian fluid and then used to determine the velocity and shear rate distributions of the microgel across gap. A reliable and full description of the different flow regimes occurring in the steady Couette flow of yield-stress fluids with slip at the rheometer walls was obtained, which includes rigid body-like motion at stresses below the yield one, rigid body-like motion and shear flow at stresses above the yield one, as well as pure shear flow once the shear stress at the outer cylinder overcomes the yield value. Slip occurred at both cylinders, which were made up of hydrophobic (inner) and hydrophilic (outer) materials, respectively. The slip velocity values measured at both walls increased along with the shear stress and the trends of these dependencies deviated from the predictions of the hydrodynamic and elastohydrodynamic lubrication mechanisms of slip in the flow of soft deformable particle dispersions [1]. Besides, the yield stress was determined with good accuracy from the velocity profiles, as well as the location of the yielded and non-yielded regions for each flow condition. Finally, the consistency of the obtained velocity profiles was tested by comparison with a theoretical prediction for the Couette flow problem of a Herschel-Bulkley fluid without slip.

Cite this publication as follows:
Medina-Banuelos EF, Marin-Santibanez BM, Perez-Gonzalez J, Rodriguez-Gonzales F: Couette flow of a yield-stress fluid with slip as studied by Rheo-PIV, Appl. Rheol. 27 (2017) 53893.


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