Interfacial rheology has been used to quantify the film
The purpose of this study is to investigate interfacial properties strength of adsorbed emulsifier layers at fluid interfaces (4of lipophilic nonionic surfactants of the sorbitan fatty acid ester 6). Both mechanical (solid-like) and flow (liquid-like) type (Spans 20, 80, 83, and 85) with the aim of selecting approproperties can be measured using this technique. Several priate emulsifiers for water-in-oil (W/O) emulsions under differstudies have been reported on the characterization of emulsient conditions. Interfacial tension and rheology were investigated fier film strength for water-soluble emulsifiers, used to stabiat a planar mineral oil/double distilled water interface using a lize oil-in-water (O/W) emulsions (6-8). For example, Wilhelmy plate method and an oscillatory ring surface rheometer, macromolecules (such as proteins) have been reported to be respectively. The effects of bulk concentration, temperature and effective stabilizers of O/W emulsions as a consequence of the presence of salt in the aqueous phase on the interfacial properties of surfactant films were determined. The relationship between their ability to form strong interfacial films (6-8). However, interfacial film properties and W/O emulsion stability in the presfew studies have been conducted on oil-soluble surfactants, ence of salt was assessed by visual observation of phase separation such as sorbitan fatty acid esters (Spans), which are typion storage. All the surfactants exhibited viscoelastic properties cally used in the preparation of water-in-oil (W/O) emulwith the exception of Span 85. Interfacial association of inverse sions. Span surfactants are effective at reducing interfacial micelles and/or surfactant multilayer formation are probably tension (9) and investigations performed on Spans 80 and responsible for the observed viscoelasticity. Addition of sodium 83, in separate studies, indicated that they possess appreciachloride to the aqueous phase and increase in temperature influble interfacial viscoelasticity (10, 11). There has not been enced the viscoelastic properties. Emulsion stability to phase sepaa detailed interfacial rheological investigation of Span surration decreased in the presence of salt. The interfacial rheology factants or of any other lipophilic surfactants. Such studies data were predictive of emulsion stability for the systems studied.
are important since it has been reported that interfacial rheo-