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.
© 2013 Applied Rheology.
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