M. Guettari - Academia.edu (original) (raw)
Papers by M. Guettari
ABSTRACT Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinat... more ABSTRACT Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinate)/isooctane microemulsions as a function of temperature between 25 C and 55 C, molar ratio Wo = water/AOT ranging from 3 to 45 and three values of AOT/isooctane volume fractions (Φm = 0.1, 0.15, and 0.2). It was shown that microemulsions behaved as Newtonian fluids in the studied range of shear rate. For a critical molar ratio, Woc, the corresponding viscosity, ηoc, was shown to be constant with temperature but dependent on the micellar concentration. For Wo < Woc, the solutions behaved as simple fluids and the temperature dependence of viscosity was described by an Arrhenius law. The total activation energy was found to be dependent on W with a maximum for Wo = 5. A correlation between the microscopic structure of the reverse micelles and the total activation energy was proposed. However, a complex fluid behavior was observed for Wo > Woc, where the viscosity increased with temperature. For some values of Wo, the viscosity reached a maximum, which could be explained by attractive interdroplet interactions and formation of droplet clusters.
Journal of Macromolecular Science, Part B, 2010
The behavior of polyvinylpyrrolidone in mixed water/methanol solvents was studied by rheoviscosim... more The behavior of polyvinylpyrrolidone in mixed water/methanol solvents was studied by rheoviscosimetry over a temperature range of 20 • C-40 • C. For the lower temperatures of this range, the intrinsic viscosity variation of the polymer vs. methanol molar fraction shows structural transitions (coil-globule-coil). This transition, which is usually attributed to the cononsolvency phenomenon, agrees with our previously published results obtained by dynamic light scattering. For higher temperatures, near 40 • C, the intrinsic viscosity increase shows an expansion of the polymer over the alcohol molar fraction range 0.2 < X A < 0.5. This last result can be attributed to the water/alcohol complex destruction under temperature increase. The "excess viscosity" of the polymermixed solvents vanishes with increasing temperature and becomes positive at 40 • C. So, the polymer chain tends to transit from a globular to an ideal chain in the middle composition range of the mixed solvents.
Brazilian Journal of Chemical Engineering, 2013
The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on... more The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on the interaction between water and methanol. First, the dynamic viscosities were measured for polymer solutions by a rotational concentric cylinder at 25 °C and for the polymer concentration range from 0.1 to 0.6 g/dl. The results show a polynomial dependence of the viscosity on polymer concentration. On the hypothesis of a quasi-binary system, a pseudo Grumberg-Nissan constant, ' p d , was introduced to quantify the interaction between unlike molecules in the presence of polymer. The interaction between unlike molecules due to the presence of the polymer was quantified by the deviation of the Grumberg-Nissan constant, ' ' p p p d d d δ = − . Generally, this constant is negative which means that the interactions between water and methanol decrease in the presence of polyvinylpyrrolidone at 25 °C. The presence of the polymer induces a perturbation of the dynamic equilibrium between free and complexed molecules.
Fluid Phase Equilibria, 2014
ABSTRACT Estimation and knowledge of transport properties of fluids are essential for heat and ma... more ABSTRACT Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. Viscosity is one of the important properties which are affected by temperature and pressure. In the present work, based on the use of econometric and statistical techniques for parametric and non-parametric regression analysis and statistical correlation tests, we propose an equation modeling the relationship between the two parameters of viscosity Arrhenius-type equation, such as the Arrhenius energy (Ea) or the pre-exponential factor (As). In addition, we introduce a third interesting parameter called Arrhenius temperature (TA), to enrich the discussion. Empirical validation using 48 data set of pure solvents from the literature and studied at different temperature ranges gives excellent statistical results which allow us to redefine the Arrhenius equation using a single parameter instead of two ones. In addition, the proposed model is very useful for engineering data and permits to estimate one non-available parameter when the second one is available.
ABSTRACT Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinat... more ABSTRACT Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinate)/isooctane microemulsions as a function of temperature between 25 C and 55 C, molar ratio Wo = water/AOT ranging from 3 to 45 and three values of AOT/isooctane volume fractions (Φm = 0.1, 0.15, and 0.2). It was shown that microemulsions behaved as Newtonian fluids in the studied range of shear rate. For a critical molar ratio, Woc, the corresponding viscosity, ηoc, was shown to be constant with temperature but dependent on the micellar concentration. For Wo < Woc, the solutions behaved as simple fluids and the temperature dependence of viscosity was described by an Arrhenius law. The total activation energy was found to be dependent on W with a maximum for Wo = 5. A correlation between the microscopic structure of the reverse micelles and the total activation energy was proposed. However, a complex fluid behavior was observed for Wo > Woc, where the viscosity increased with temperature. For some values of Wo, the viscosity reached a maximum, which could be explained by attractive interdroplet interactions and formation of droplet clusters.
Journal of Macromolecular Science, Part B, 2010
The behavior of polyvinylpyrrolidone in mixed water/methanol solvents was studied by rheoviscosim... more The behavior of polyvinylpyrrolidone in mixed water/methanol solvents was studied by rheoviscosimetry over a temperature range of 20 • C-40 • C. For the lower temperatures of this range, the intrinsic viscosity variation of the polymer vs. methanol molar fraction shows structural transitions (coil-globule-coil). This transition, which is usually attributed to the cononsolvency phenomenon, agrees with our previously published results obtained by dynamic light scattering. For higher temperatures, near 40 • C, the intrinsic viscosity increase shows an expansion of the polymer over the alcohol molar fraction range 0.2 < X A < 0.5. This last result can be attributed to the water/alcohol complex destruction under temperature increase. The "excess viscosity" of the polymermixed solvents vanishes with increasing temperature and becomes positive at 40 • C. So, the polymer chain tends to transit from a globular to an ideal chain in the middle composition range of the mixed solvents.
Brazilian Journal of Chemical Engineering, 2013
The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on... more The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on the interaction between water and methanol. First, the dynamic viscosities were measured for polymer solutions by a rotational concentric cylinder at 25 °C and for the polymer concentration range from 0.1 to 0.6 g/dl. The results show a polynomial dependence of the viscosity on polymer concentration. On the hypothesis of a quasi-binary system, a pseudo Grumberg-Nissan constant, ' p d , was introduced to quantify the interaction between unlike molecules in the presence of polymer. The interaction between unlike molecules due to the presence of the polymer was quantified by the deviation of the Grumberg-Nissan constant, ' ' p p p d d d δ = − . Generally, this constant is negative which means that the interactions between water and methanol decrease in the presence of polyvinylpyrrolidone at 25 °C. The presence of the polymer induces a perturbation of the dynamic equilibrium between free and complexed molecules.
Fluid Phase Equilibria, 2014
ABSTRACT Estimation and knowledge of transport properties of fluids are essential for heat and ma... more ABSTRACT Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. Viscosity is one of the important properties which are affected by temperature and pressure. In the present work, based on the use of econometric and statistical techniques for parametric and non-parametric regression analysis and statistical correlation tests, we propose an equation modeling the relationship between the two parameters of viscosity Arrhenius-type equation, such as the Arrhenius energy (Ea) or the pre-exponential factor (As). In addition, we introduce a third interesting parameter called Arrhenius temperature (TA), to enrich the discussion. Empirical validation using 48 data set of pure solvents from the literature and studied at different temperature ranges gives excellent statistical results which allow us to redefine the Arrhenius equation using a single parameter instead of two ones. In addition, the proposed model is very useful for engineering data and permits to estimate one non-available parameter when the second one is available.