On the Coalescence Characteristics of Low Tension Oil-Water-Surfactant Systems
The coalescence behavior of isolated oil drops in microemulsion systems and of microemulsion drops in brine systems is studied. A new 3xperimental method is presented for conducting such controlled coalescence tests in an inclined spinning drop apparatus. Observations on five oil-water-surfactant systems are presented, three involving iso-octane as the oil phase and two involving crude oils. Coalescence times were measured in terms of the applied coalescence force and the droplet-droplet contact radius. The results show a wide range of behavior with coalescence rate per unit coalescence force varying over three orders of magnitude, with the specific magnitude for any given system being quite sensitive to the nature of the system and the associated phase changes with varying NaC1 concentration. In nearly all cases, the most rapid coalescence occurred with the lowest tension systems. This apparently reflects the increased tendency of low tension systems to exhibit film rupture at relatively large values of the critical film thickness. The specific role of such effects and interfacial viscous effects are discussed.
KeywordsInterfacial Tension Contact Radius Mobile Interface Tension System Coalescence Time
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