Emulsions Lecture Notes by Dr. Hamid Montazeri

A collection of flashcards based on the lecture notes covering emulsions, their types, properties, and role of emulsifiers.

What are emulsions?

Thermodynamically unstable dispersed systems where small droplets of liquid (dispersed phase) are distributed in another immiscible liquid (dispersion phase).

What is the dispersed phase?

composed of small droplets of liquid

What is the dispersion phase?

Distributed in another liquid

What are the two types of liquid?

Immiscible liquids and miscible liquids.

What is the dispersed phase known as?

Internal phase

What is the dispersion phase known as?

external phase

Can emulsions have more than two phases?

Yes

What are topical liquid emulsions called?

Lotions

Miscible

When two liquids are completely soluble in each other in all proportions

Immiscible liquid pairs

Not soluble in each other in any proportion

Emulsification

the process of creating an emulsion from two immiscible liquid phases

Are emulsions physically stable?

No

How are emulsions made?

Combine two immiscible liquids in a relatively homogenous manner

What are the two main types of emulsions?

Oil-in-water (O/W) and water-in-oil (W/O) are the two main types of emulsions.

Oil-in-water

This type of emulsion consists of oleaginous (lipophilic) droplets dispersed in an aqueous continuous phase

Water-in-oil

Here, the dispersed droplets are of aqueous nature, and the continuous phase is lipophilic (oily)

Water-in-Oil-in-water

This is a three phase emulsion, where the continuous phase is aqueous, and the dispersed droplets are a dispersion of aqueous phase dispersed in oil

Oil-in-Water-in-Oil

the dispersed aqueous droplets contain smaller droplets of oil dispersed in them. The continuous phase is lipophilic (oily)

What can determine the emulsion type?

Dilution test, Dye test, Drop test

Dilution test

A portion of the formulation is diluted with water

Dye test

A water soluble dye is added to the emulsion and mixed

Drop test

A drop of the formulation is put on the surface of water

Surface Tension Theory

Surfactants (AKA surface active agents) lower the interfacial tension of the two immiscible liquids, reducing the repellent force between the liquids, and diminishing each liquid’s attraction for its own molecules

Oriented-wedge Theory

This theory assumes monomolecular layers of emulsifying agent curved around the droplet of internal phase of emulsion. It is based on the assumption that certain surfactants orient themselves about and within a liquid according to their solubility

Plastic or Interfacial Film Theory

This theory places emulsifying agent at the interface between oil and water, surrounding the droplets of the internal phase as a thin layer of file absorbed on the surface of the droplet. This film prevents contact between the dispersed droplets

What does the Plastic or Interfacial Film Theory prevent?

Contact between the dispersed droplets

Emulsifying Agents

Natural emulsifying agents, Finely divided solids, Synthetic Surfactants

Natural emulsifying agents

Usually form multi-molecular films

Finely divided solids

Form a film of particles

Synthetic Surfactants

Form mono-molecular Film

Natural Emulsifying Agents

They usually do not lower the interfacial tension, but form multi-molecular layers, only form oil-in-water emulsions, and have been used for many years