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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.
Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics
Appl. Rheol. 20:2 (2010) 24380 (8 pages) ►
Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines in the areas of physics, chemistry, engineering, biology, and medicine. Currently used descriptions of surface rheology have a number of limitations, and in particular are hard to generalize to the large deformation regime. Data are often analyzed with constitutive equations based on straightforward generalizations of models developed for describing bulk phase rheology. Since the latter are in general designed to describe incompressible materials, they are not guaranteed to describe highly compressible interfaces correctly. Here we discuss a unified approach to surface rheology based on nonequilibrium thermodynamics (NET) that provides a consistent set of balance and constitutive equations for the unambiguous determination of surface rheological parameters, both near and far beyond equilibrium. A closer integration of experimental surface rheology and multiphase nonequilibrium thermodynamics would clearly be beneficial for both disciplines.► Cite this publication as follows:
Sagis L: Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics, Appl. Rheol. 20 (2010) 24380.
Carlos I. Mendoza, Ivan Santamaria-Holek
Rheology of concentrated emulsions of spherical droplets
Appl. Rheol. 20:2 (2010) 23493 (8 pages) ►
We propose a viscosity model accounting for experiments of emulsions of two immiscible liquids at arbitrary volume fractions. The model is based on a recursive-differential method formulated in terms of the appropriate scaling variable which emerges from an analysis of excluded volume effects in the system. This variable, called the effective filling fraction, incorporates the geometrical information of the system which determines the maximum packing and reduces to the bare filling fraction for infinitely diluted emulsions. The agreement of our model for the viscosity with experiments and previous theories is good for all the range of volume fractions and viscosity ratios.► Cite this publication as follows:
Mendoza CI, Santamaria-Holek I: Rheology of concentrated emulsions of spherical droplets, Appl. Rheol. 20 (2010) 23493.
Mathias Krebs, Olaf Wunsch
Development and testing of a new pressure cell for rheological characterisation of polymer melts
Appl. Rheol. 20:2 (2010) 23229 (6 pages) ►
A new pressure cell is described to measure the flow behaviour of polymer melts in dependence of temperature and pressure. Special attention is laid on the construction and functionality of the pressure cell. The pressure cell can be pressurized up to 120 bar and is heatable up to 260 C. As a measuring geometry a plate-plate-system is used which is capable of characterising high viscous fluids. First results with high viscous silicone oil show good agreement with known references in literature.► Cite this publication as follows:
Krebs M, Wunsch O: Development and testing of a new pressure cell for rheological characterisation of polymer melts, Appl. Rheol. 20 (2010) 23229.
Noemi Baldino, Lucia Seta, Massimo Migliori, Domenico Gabriele, Bruno de Cindio, Giuseppe Chdichimo
Rheological modelling of plaster deposition for painting restoration
Appl. Rheol. 20:2 (2010) 23110 (9 pages) ►
This paper reports on the result of rheological modelling of plaster deposition for paintings restoration. A typical plaster recipe was changed in order to check the effect of water level on rheological properties, both performing oscillatory tests and measuring plaster viscosity at two different temperatures. A model based on momentum balance on a vessel-nozzle geometry for a shear thinning fluid was set-up to simulate the deposition process and numerical results were compared to experimental data. A good agreement was found for moderate deposition times. At high process time, due to phase-separation in plaster, a loss in matching between the simulation and experimental point was found, because the modelling assumption of 'pseudo-homogeneous' behaviour does not apply anymore. Simulations allowed operating charts to be prepared reporting the deposited plaster volume as a function of the main process variables (temperature and pressure) and rheological properties of the plaster. This model could effectively support the development of an automatic deposition system able to recognise the filling volume over the painting surface and to control autonomously feeding of the plaster from a vessel through the deposition nozzle► Cite this publication as follows:
Baldino N, Seta L, Migliori M, Gabriele D, deCindio B, Chdichimo G: Rheological modelling of plaster deposition for painting restoration, Appl. Rheol. 20 (2010) 23110.
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