Interfaces rheology



The formation of an emulsion occurs when mechanical energy is supplied to the system composed of two or more immiscible liquids.

This energy is used to agitate the system, thus producing droplets, which greatly increase the total area of the interfaces between the liquids. For a fixed amount of energy, the smaller the interfacial tension between the phases, the greater the total area formed, that is, the smaller the droplets formed. After the application of energy, the natural tendency, dictated by the second law of thermodynamics, is the spontaneous coalescence of the drops and the consequent separation of the phases. However, emulsions can remain stable for long periods, depending on the mechanical behavior (or rheology) of the interfaces that delimit the droplets (dispersed phase) from the continuous phase. Rigid interfaces populated by amphiphilic molecules or particles tend to stabilize the emulsions, while clean interfaces tend to allow rapid coalescence. If the objective is to stabilize an emulsion, the agitation energy must already be applied in the presence of an appropriate amphiphilic agent. If, on the other hand, the objective is to separate the phases, it is necessary to use other agents that act on the interfaces, dislodging the stabilizing agents. To evaluate the efficiency of stabilizing or destabilizing agents, the simplest and most practical method is to study the rheology of the interface. We have an excellent infrastructure and trained personnel in this area, which allows us to measure interface properties such as shear viscosity, elastic dilation and shear moduli, Langmuir isotherms, among others.

At the end of the study, a report will be made available containing the main results of interest in the form of figures, graphs and tables, with analysis and interpretation.

Infraestrutura: Reômetro rotacional com acessório Double-Wall Ring (DWR), com controle de temperatura e de pressão interfacial; cuba de Langmuir; cuba de deformação isotrópica; tensiômetro de gota Teclis com sistema de pressurização; tensiômetros Krüss e Lauda.


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