Destruction of Concentrated Emulsions Undergoing Coalescence

Lifetime and Destruction of Concentrated Emulsions Undergoing Coalescence 

BENEDICTE DEMINIERE, ANNIE COLIN, FERNANDO LEAL CALDERON AND JEROME BIBETTE 

Centre de Recherche Paul Pascal, Av. A. Schweitzer, F-33600 Pessac, France 

Emulsions are metastable colloids made out of two immiscible fluids, one being dispersed in the other, in the presence of surface active agents. The droplet volume fiaction may vary from zero to almost one dense emulsions are sometimes called biliquid foams since their structure is very similar to the cellular structure of air-liquid foams for which the continuous phase is very minor. From dilute to highly concentrated, emulsions exhibit very different internal dynamics and mechanical properties. When diluted, droplets are agitated by Brownian motion and behave as viscous Newtonian fluids, whereas when more concentrated, namely above the random close packing volume fraction which is 64% for monodisperse droplets, the internal dynamics are severely restricted and they behave as viscoelastic solids. Simple direct emulsions are composed of oil droplets dispersed in water while inverse emulsions are composed of water droplets dispersed in an oil continuous phase. In fact, emulsions are in principle made out of two immiscible phases for which the interfacial tension is therefore non-zero, and may involve other hydrophilic-like or lipophilic-like fluids in the presence of suitable surface active species, each phase being possibly comprised of numerous components. Sometimes, simple emulsions may also contain smaller droplets of the continuous phase dispersed within each droplet of the dispersed phase. Such systems are called double emulsions or multiple emulsions.  

Emulsions are artificial and, depending both on the metastability of the freshly formed interfaces and the fragmentation procedure which is employed, various structures may be generated. However, their lifetime may vary considerably some systems are impossible to prepare whatever the employed procedure, some others 

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Lifetime and Destruction of Concentrated Emulsions Undergoing Coalescence 0.3... 

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