Pharma, Cosmetics | Rheology of Microemulsions (base for lotions and gels)

This application report explains various rheological standard tests for characterizing samples in the pharmaceutical industry. The measurements are performed on the Anton Paar Rotational Rheometer RheolabQC.

In the pharmaceutical industry microemulsions are often used as the base for gels and lotions.

This report presents different rheological methods which can be used for characterizing gels and lotions. The described methods include flow and viscosity curves, the “yield point“, structural regeneration (“thixotropy“) and determination of temperature-dependent behavior. The measuring methods presented here are useful for the manufacturing process (homogenizing, pumping, filling, etc.) and also for the subsequent end-use of the gels and lotions.

Microemulsions are clear or slightly opalescent homogenous liquids consisting of at least two fluids which do not mix (e.g. water and oil) plus a surfactant (tenside). Microemulsions are thermodynamically very stable in comparison to “normal emulsions” (homogenously distributed droplets). They therefore display a high degree of long-term stability. Besides the long-term stability there are other advantages resulting from the high proportion of tensides. These advantages are especially relevant for the pharmaceutical industry. The high tenside content can influence the skin barrier and allow medical agents dissolved in the microemulsion to move through the skin into the organism (“penetration“).

The rheological behavior of microemulsions is controlled by adding different additives during the manufacturing process.

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