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Emulsion stability and rheology

  • Supervisor: prof. Daniel Bonn
  • Research Team: Riande Dekker, Yuri Hendrix, Heleen Kibbelaar
  • Goal: Investigate the stability and rheology of various emulsions
  • Info: D. Bonn

Emulsions play an important role in everyday life and can be found in for example food, cosmetics and paints. They consist of two immiscible liquids where one liquid is dispersed in the other. Emulsions are thermodynamically unstable but can be kinetically stabilized by addition of surface-active agents. Indeed, stabilizing or destabilizing emulsions is of considerable industrial importance. For instance, stabilization is needed to improve the shelf life of cosmetics, drugs and food products, while destabilization is a key step in oil recovery, by extracting water from the recovered crude oil. We use the squeeze flow technique for emulsion destabilization to investigate the dynamics and hence the characteristic time scales of the processes responsible for the destabilization of the emulsion. Rheology is a useful tool to investigate emulsions. Understanding and predicting the flow behaviour of these complex materials is of industrial and fundamental importance. These materials show the emergence of a yield stress for volume fractions above a critical volume fraction, called the jamming transition. At small stresses yield stress materials behave like solids, deforming in an elastic manner. However, once a critical stress, called the yield stress, is exceeded, the material starts to flow. Describing the flow properties of yield stress materials as a function of the volume fraction has become an important research topic and can give useful insights for the preparation of emulsions for industrial applications.