Self-emulsification mechanism

Figure 5. Schematic Representation of the Proposed Self-Emulsification Mechanism. A. Water Penetration. B. Formation of Liquid Crystal. C. Disruption and Emulsification.

The emulsion blocking mechanism involves formation of emulsion in the pores either by self-emulsification of water-based filtrate with the crude oil, or oil filtrate from an oil-based fluid emulsifying formation water. The emulsions are viscous and can block the pores. The remedial design is to prevent emulsification either by eliminating oil from completion fluid or by the use of demulsifiers. 

M.G. Wakerly, C.W. Pouton, B.J. Meakin, and E.S. Morton Self emulsification of vegetable oil non-ionic mixtures a proposed mechanism of action. In Phenomena in Mixed Surf actant Systems. American Chemical Society, Washington, DC (1986). 

Wakerly, M.G., Pouton, C.W., Meakin, . J., and Morton, F.S. (1986). Self-emulsification of vegetable oil-nonionic surfactant mixtures A proposed mechanism of action. A.C.S. Symposium, 311, 242-255. 

D. Q. Craig, S. A. Barker, D. Banning, and S. W. Booth, Investigation into the mechanisms of self-emulsification using particle size analysis and low frequency dielectric spectroscopy, Int. J. Pharmaceut. 114 103-110 (1995). 

As mentioned in introduction, nano-emulsions being nonequilibrium systems require an energy input for their formation, which can be supplied mechanically (high-energy emulsification), or from the chemical energy of the components (condensation or low-energy emulsification methods). In this section, the different condensation methods, which are classified as self-emulsification and phase inversion methods, will be discussed. 

The so-called self-emulsification is referred to those methods in which the nano-emulsion is just obtained by a dilution process without any inversion of phases. It is also called direct emulsification because the initial emulsion type is that of the intended final emulsion [19]. It should be taken into account that the term self-emulsification is frequently used in the Ulerature to describe emulsification mechanisms, in which not only dilution processes but also processes implying changes in the spontaneous curvature of the surfactant film are involved. Therefore, this terminology is often misleading. 

A (macro)emulsion is formed when two immiscible Hquids, usually water and a hydrophobic organic solvent, an oil, are mechanically agitated (5) so that one Hquid forms droplets in the other one. A microemulsion, on the other hand, forms spontaneously because of the self-association of added amphiphilic molecules. During the emulsification agitation both Hquids form droplets, and with no stabilization, two emulsion layers are formed, one with oil droplets in water (o /w) and one of water in oil (w/o). However, if not stabilized the droplets separate into two phases when the agitation ceases. If an emulsifier (a stabilizing compound) is added to the two immiscible Hquids, one of them becomes continuous and the other one remains in droplet form. 

Emulsions are formed by mixing two liquids, a process which creates discrete droplets in a continuous phase. During emulsification,by mechanical agitation for example, both liquids tend to form droplets resulting in a complex mixture of 0/W and W/0 emulsions. Which of the components forms the continuous phase depends on the emulsifier used since one of the types of droplet is unstable and coalesces. Therefore, there is a need to identify the continuous phase in emulsion systems not only in the final emulsion system, but also at short times after emulsion formation or even dining the emulsification process. The NMR self-diffusion method may easily distinguish the continuous and... 

Previous chapters have discussed the formation of colloidal particles by various mechanisms, including commutation, nucleation and growth, and emulsification. There exists another very important class of colloids that differ significantly from those discussed previously. Their formation, for example, does not result from the input of energy such as in commutation or emulsification it is a spontaneous association process resulting from the energetics of interaction between the individual units and the solvent medium, as is crystallization. However, the size, shape, and basic nature of the associated structure are controlled by a complex series of factors distinctly different from those involved in crystalhzation. The size, in particular, will be much more limited than that of a normal crystal. This class of colloids is generally referred to as association or self-assembled colloids. 

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