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Maria Jesus Hernandez Lucas, Teresa Sanz Taberner, Ana Salvador Alcaraz, Francisco J. Rubio Hernandez, Roberto Steinbruggen
IBEREO 2017

Appl. Rheol. 27:6 (2017) 42-44

Cite this publication as follows:
HernandezLucas MJ, SanzTaberner T, SalvadorAlcaraz A, RubioHernandez FJ, Steinbruggen R: IBEREO 2017, Appl. Rheol. 27 (2017) 42.

Jaime Caballero-Hernandez, Ana Gomez-Ramirez, Juan D. G. Duran, Fernando Gonzalez-Caballero, Andrey Zubarev, Modesto T. Lopez-Lopez
On the effect of wall slip on the determination of the yield stress of magnetorheological fluids

Appl. Rheol. 27:1 (2017) 15001 (8 pages)

We study the effect of wall slip on the measured values of the yield stress of magnetorheological (MR) fluids. For this aim we used a rheometer provided with parallel-plate geometries of two types, distinguished by having smooth or rough surfaces. We found that wall slip led to the underestimation of the yield stress when measuring geometries with smooth surfaces were used, and that this underestimation was more pronounced for the static than for the dynamic yield stress. Furthermore, we analysed the effect that both irreversible particle aggregation due to colloidal interactions and reversible magnetic fieldinduced particle aggregation had on the underestimation provoked by wall slip. We found that the higher the degree of aggregation the stronger the underestimation of the yield stress. At low intensity of the applied magnetic field irreversible particle aggregation was dominant and, thus, the underestimation of the yield stress was almost negligible for well-dispersed MR fluids, whereas it was rather pronounced for MR fluids suffering from irreversible aggregation. As the magnetic field was increased the underestimation of the yield stress became significant even for the best dispersed MR fluid.

Cite this publication as follows:
Caballero-Hernandez J, Gomez-Ramirez A, Duran JD, Gonzalez-Caballero F, Zubarev A, Lopez-Lopez MT: On the effect of wall slip on the determination of the yield stress of magnetorheological fluids, Appl. Rheol. 27 (2017) 15001.

Pilar Olivares-Carrillo, Antonia Perez de los Rias, Joaquin Quesada-Medina, Jose Gines Hernandez Cifre, Francisco Guillermo Diaz Banos
Viscosity as a measure of oil composition changes due to thermal degradation

Appl. Rheol. 24:5 (2014) 53667 (6 pages)

In this work, the viscosity of soybean oil subjected to thermal degradation has been determined and related to the chemical composition of the oil. In particular, it is found a linear relationship between the viscosity value and the triglycerides content during the degradation process (an increase of the former is associated to a decrease of the latter). Thus, it is shown that viscosity provides us a reliable way of measuring oil degradation and, insofar as proportional to flow time, it allows for the design of simple devices to control the oil quality. Besides, the study of the viscosity behavior along with the changes in composition during the cooking time, i.e. the period of time that the oil is being heated, give us valuable information about the type of chemical reactions occurring within the oil.

Cite this publication as follows:
Olivares-Carrillo P, PerezdelosRios A, Quesada-Medina J, HernandezCifre JG, DiazBanos FG: Viscosity as a measure of oil composition changes due to thermal degradation, Appl. Rheol. 24 (2014) 53667.

F.J. Rubio-Hernandez, A.I. Gomez-Merino, J.F. Velazquez-Navarro, L. Parras
4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013)

Appl. Rheol. 23:6 (2013) 374-375

Cite this publication as follows:
Rubio-Hernandez F, Gomez-Merino A, Velazquez-Navarro J, Parras L: 4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013), Appl. Rheol. 23 (2013) 374.

Francisco Jose Galindo-Rosales, Francisco Jose Rubio-Hernandez
Static and Dynamic Yield Stresses of Aerosil(R) 200 suspension in Polypropylene Glycol

Appl. Rheol. 20:2 (2010) 22787 (10 pages)


Fumed silica suspensions in low molecular weight liquids are used in many photonic and microelectronic applications, playing its rheology a major role in the effectiveness of their usage. Particle-particle and particle-liquid medium interactions of suspensions of hydrophilic fumed silica in low molecular weight polar media, polypropylene glycol of 400 and 750 g/mol, concretely, have been already investigated.There, the affinity between polar solvent molecules and fumed silica particles prevents the formation of a 3D gel network. In this work it has been found that fumed silica can develop a flocculated suspension when it is dispersed in polypropylene glycol with a molecular weight of 2000 g/mol. Besides, it has been found that this suspension exhibits time dependent behaviour within its reversible shear thinning region, which is related to thixoelasticity. The experimental method, proposed theoretically by Cheng in 1986 to obtain the dynamic yield stress in thixotropic systems has been here extended successfully to a thixoelastic system.

Cite this publication as follows:
Galindo-Rosales FJ, Rubio-Hernandez FJ: Static and Dynamic Yield Stresses of Aerosil(R) 200 suspension in Polypropylene Glycol, Appl. Rheol. 20 (2010) 22787.

Manuel Dolz, Francesco Corrias, Octavio Diez-Sales, Alejandro Casanovas, M.J. Hernandez
Influence of test times on creep and recovery behaviour of Xanthan gum hydrogels

Appl. Rheol. 19:3 (2009) 34201 (8 pages)

Rheological creep and recovery tests have been applied at different assay times to xanthan gum hydrogels at several concentrations. The Burger model has been successfully applied to fit the creep data and to analyze results. Increasing the xanthan gum concentration also increases the elastic and viscous components without changing the molecular distribution of these hydrogels. A semi-empirical equation considering the different elements of the Burger model has been proposed to analyze compliance behavior in recovery tests. The dependence of the relative contribution to deformation of the Maxwell and Kelvin-Voigt units upon xanthan gum concentration and recovery assay times has been evaluated. Since the recovery ratio is the same for all hydrogels, we suggest parallel structures with no mutual interactions are formed when increasing concentration.

Cite this publication as follows:
Dolz M, Corrias F, Diez-Sales O, Casanovas A, Hernandez M: Influence of test times on creep and recovery behaviour of Xanthan gum hydrogels, Appl. Rheol. 19 (2009) 34201.

Jose Gines Hernandez Cifre, Jose Garcia de la Torre
Radiation Scattering by Dilute Polymer Solutions in Shear Flow: An Example of Mesoscale Modeling and Brownian Dynamics Simulation

Appl. Rheol. 13:4 (2003) 200-208

The intention of the paper is to illustrate the ability of the Brownian dynamics simulation technique applied to mesoscale polymer models in order to reproduce light scattering experiments of dilute polymer solution under flow. After suitable parameterization of a real polymeric system, polystyrene solved in a oligostyrene/toluene mixture at 299 K (good solvent conditions), a bead-spring model of the polymer chain is built and used to generate molecular trajectories on a computer. Such trajectories will capture the deformational and orientational processes experienced by the real polymer chain under flow. Then, from the set of molecular conformations generated, several polymer properties as well as typical scattering patterns can be reproduced quite accurately. FENE springs were used and excluded volume and non-preaveraging hydrodynamic interaction were taken into account in order to build a chain model as realistic as needed.

Cite this publication as follows:
HernandezCifre JG, delaTorre J: Radiation Scattering by Dilute Polymer Solutions in Shear Flow: An Example of Mesoscale Modeling and Brownian Dynamics Simulation, Appl. Rheol. 13 (2003) 200.


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