| 1. |
- Allouche, Joachim, et al.
(författare)
-
Simultaneous Conductivity and Viscosity Measurements as a Technique To Track Emulsion Inversion by the Phase-Inversion-Temperature Method
- 2004
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:6, s. 2134-2140
-
Tidskriftsartikel (refereegranskat)abstract
- Two kinds of transitions can occur when an emulsified water-oil-ethoxylated nonionic surfactant system is cooled under const. stirring. At a water-oil ratio close to unity, a transitional inversion takes place from a water-in-oil (W/O) to an oil-in-water (O/W) morphol. according to the so-called phase-inversion-temp. method. At a high water content, a multiple W/O/W emulsion changes to a simple O/W emulsion. The continuous monitoring of both the emulsion cond. and viscosity allows the identification of several phenomena that take place during the temp. decrease. In all cases, a viscosity max. is found on each side of the three-phase behavior temp. interval and correlates with the attainment of extremely fine emulsions, where the best compromise between a low-tension and a not-too-unstable emulsion is reached. The studied system contains Polysorbate 85, a light alkane cut oil, and a sodium chloride brine. All transitions are interpreted in the framework of the formulation-compn. bidimensional map.
|
|
| 2. |
- Allouche, Joachim, et al.
(författare)
-
Single- and Two-Step Emulsification To Prepare a Persistent Multiple Emulsion with a Surfactant-Polymer Mixture
- 2003
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 42:17, s. 3982-3988
-
Tidskriftsartikel (refereegranskat)abstract
- The regions corresponding to different emulsion morphol. occurrences have been clearly identified on a bidimensional formulation-compn. map. Multiple emulsions spontaneously form when there is a conflict between the formulation and compn. effects. In such systems the most external emulsion is found to be unstable when the formulation effect is produced by a single surfactant. The use of a proper surfactant-polymer mixt. allows one to strongly inhibit the mass transfer and to considerably lengthen the equilibration between interfaces. As a consequence, the multiple emulsion can be stable enough to be used in encapsulation and controlled-release applications. The area where multiple emulsions occur and their characteristics (cond. and amt. of encapsulated external phase) are reported for a system contg. a sorbitan ester lipophilic surfactant and a diblock poly(ethylene oxide)-poly(propylene oxide) hydrophilic polymer, as a function of the formulation and compn., for a single-step process in which a specific amt. of mech. energy (stirring) is supplied. An increase in the oil viscosity is found to alter the map and to modify the multiple emulsion characteristics. The application of the results to emulsion-making technol. is discussed.
|
|
