Emulsions: Principles and preparation - Making emulsions using physical destabilization - Phase inversion

8 important questions on Emulsions: Principles and preparation - Making emulsions using physical destabilization - Phase inversion

Which 2 methods of phase inversion to make emulsions exist? And what are their differences?

  1. Catastrophic phase inversion --> adding more and more dispersed phase
  2. Transitional phase inversion --> properties of emulsion are changed from favouring droplets of the low-viscous phase to droplets of the high-viscous phase

For what is phase inversion used?

When the viscosity of one of the phases is much larger.

How does catastrophic phase inversion work?

  • One starts with the phase that should become the dispersed phase. One then slowly adds the other phase (B) to phase (A), while the system is agitated. Droplets of phase B are formed, which are broken up into small droplets (agitation). However, you want A in B, so the surfactant system is dissolved in phase B and not in phase A.
  • Emulsion becomes so concentrated and viscosity so high, that the droplets of B start to coalesce. B makes the continuous phase and A starts to be the dispersed phase.

What are disadvantages of catastrophic phase inversion?

  • Final droplet size is usually not very small
  • Emulsion can be rather polydisperse

How does transitional phase inversion work?

The first step is to prepare an emulsion of the phase that should become the continuous phase (B) in a continuous phase (A). Surfactant system is chosen carefully, favours the formation of B-in-A emulsion. When emulsion is prepared, conditions are changed (temperature, pH) so that it favours A-in-B emulsion.

What is a difference between catastrophic and transitional phase inversion?

Catastrophic --> surfactant has affinity for A or B
Transitional --> surfactant affinity for both is equal

What is a micro emulsion?

An intimately mixture of 2 phases. There is not clear A-in-B or B-in-A emulsion.

Why is transitional phase inversion not used in the food industry?

Due to the properties of oils commonly used in foods, finding a surfactant system that exhibits this behaviour has not yet succeeded.

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