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Chapter 22

Emulsions

Emulsions consist of at least three components: water or any liquid miscible with water, oil or any liquid immiscible with water, and an emulsifying agent. The emulsifying agent is an amphipathic solute that is strongly adsorbed at the oil/water interface. The presence of the emulsifying agent prevents coalescence of the dispersed phase, as such coalescence would require desorption of molecules that had gone spontaneously to the interface. An empirical rule postulated by Bancroft also refers to the emulsifier, namely, that the phase in which it is the more soluble will end up as the external phase of the emulsion. Exceptions to both these generalizations can be found but only with
relatively poorly adsorbed emulsifiers.
Emulsifiers may be selected by means of the HLB Scale or by the phase-inversion temperature (PIT). The physical properties of the interface and of whole emulsions are described. Methods of making and breaking emulsions are described.

Key Words: asphalt emulsions, Bancroft’s rule, breaking emulsions, coalescence, coemulsifier, continuous phase, creaming, discontinuous phase, dispersed phase, dynamic foams, emulsifier, emulsion type, HLB scale, demulsification, emulsion inversion, emulsion polymerization, emulsion stability, external phase, hard-sphere model, hydrophobic particles, hydrophobic silica, interfacial area, intermittent milling, internal phase, making emulsions, microemulsion, miniemulsion, oil-in-water, O/W, osmotic stabilization, Ostwald ripening, phase-inversion temperature, PIT, phase inversion, Pickering emulsions, static foams, surface rheology, water-in-oil, W/O


 



 



 

 


 

 

 




 


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