Emulsification methods

Different methods are used in microemulsion formation a low-energy emulsification method by dilution of an oil surfactant mixture with water and dilution of a water-surfactant mixture with oil and mixing all the components together in the final composition. These methods involve the spontaneous formation of microemulsions and the order of ingredient addition may determine the formation of the microemulsion. Such applications have been performed with lutein and lutein esters. ... 

Techniques of emulsification of pharmaceutical products have been reviewed by Block [27]. The location of the emulsifier, the method of incorporation of the phases, the rates of addition, the temperature of each phase, and the rate of cooling after mixing of the phases considerably affect the droplet size distribution, viscosity, and stability of the final emulsion. Roughly four emulsification methods can be distinguished ... 

The drawbacks of the W/O emulsification method include the use of large amounts of oils as the external phase, which must be removed by washing with organic solvents, heat stability problems of drugs, possible interactions of the cross-linking agent with the drug, and, as with all nanoparticles prepared by emulsification techniques, a fairly broad particle size distribution. 

The nanoemulsion mean droplet sizes were much smaller than those obtained in other systems using polar oil mixtures (above 500 nm) [18]. The findings verify that the low-energy emulsification methods are valid not only for aliphatic [9,10,13, 75, 76, 79-81] and semipolar oils [82-84], as reported in most studies devoted to low-energy emulsification, but also for polar solvent-preformed polymer mixtures. These nanoemulsions show good kinetic stability at 25 °C over a period of at least 24 h,... 

Forgiarini, A., Esquena, J., Gonzalez, C. and Solans, C. (2001) Formation of nano-emulsions by low-energy emulsification methods at constant temperature. Langmuir, 17 (7),... 

Sadurm, N., Solans, C., Azemar, N. and Garci a-Celma, M.J. (2005) Studies on the formation of O/W nano-emulsions, by low-energy emulsification methods, suitable for pharmaceutical aplications. Emulsion polymerization initiation of polymerization in monomer droplets., 26, 438-445. 

Galindo-Alvarez, J., Boyda, D., Marchal, Ph., Tribet, Ch., Perrin, P., Begue, E.M., Durand, A. and Sadder, V. (2011) Miniemulsion polymerization templates a systematic comparison between low energy emulsification (Near-PIT) and ultrasound emulsification methods. Colloids and Surfaces A Physicochemical and Engineering Aspects, 374 (1—3), 134—141. 

More complex geometries have been developed [40] and the influence of the geometrical structure has been examined. Although straight-through microchannel emulsification has been developed [39,41], the production rates are still low compared to those obtained with standard emulsification methods. However, the very high monodispersity makes this emulsification process very suitable for some specific fechnological applicafions such as polymeric microsphere synfhesis [42,43], microencapsulation [44], sol-gel chemistry, and electro-optical materials. 

Phase inversion may be used as an emulsification method for systems with a very high internal phase content [130-133]. The process is illustrated in Fig. 1.7 for... 

The size characteristics of emulsions obtained through different techniques reviewed in this chapter are summarized in Table 1.2. The emulsification method should be selected depending on the required size for industrial use. For high-jet homogenization, the stabilizer concentration and the applied pressure should be properly controlled. The dispersed volume fraction is restricted to 30% to avoid... 

N. Uson, MJ. Garcia, and C. Solans Formation of Water-in-Oil (W/O) Nano-Emulsions in a Water/Mixed Non-Ionic Surfactant/Oil Systems Prepared by a Low-Energy Emulsification Method. Colloid and Surfaces A Physicochem. Eng. Aspects 250, 415 (2004). 

The fourth approach to the stabilization of heterogeneous fuels—by gelation of the liquid carrier—has been developed more thoroughly than the emulsification method. Hence, the gelled fuels are discussed in greater detail than emulsified fuels. However, some aspects of heterogeneous fuels are not related to mechanical stabilization when these are discussed in connection with gelled fuels, it will be apparent that the comments apply also to emulsified fuels. 

Figure 1. The effect of emulsification method on particle size distribution.

In the early 1990s, Nakashima et al. [2] introduced membrane technology in emulsions preparation by a direct emulsification method, whereas, in the late 1990s, Suzuki et al. used premix membrane emulsification to obtain production rates higher than other membrane emulsification methods [11]. 

The emulsification method is primarily used for waterborne epoxy adhesive systems and is the focus of this section. The epoxy resin is made water-dispersible by partitioning the epoxy resin within a micelle, effectively separating the resin from the water. This emulsification can be achieved by a suitable surfactant. 

Emulsification Method. Emulsified sulfur-asphalt binder was prepared by combining molten sulfur and liquid asphalt in a 2Vi -in.-diameter, vertical, Gifford Wood colloid mill (1) at a rotor-stator gap setting of... 

Direct Substitution Method. Sulfur and asphalt were poured together at 300°F and were added to the heated aggregate at 300°-320°F. The three materials were mixed in the Hobart mixer for 2 min. Standard Marshall test samples for Marshall and dynamic stiffness tests were prepared as in the emulsification method. Bar samples for fatigue testing were prepared by kneading the mix into 3 X 3 X 12-in. bars to obtain compaction equal to the Marshall compacts. 

The grafted silicone polymers have been emulsified by the spontaneous emulsification method. The emulsification took advantage of the very low solubility of the polymers in water. Stable emulsions with sizes ranging between 200 and 500 nm have been produced. 

Fig. 5 Microscopy pictures of giiseofulvin crystals precipitated in water and out from a silicone emulsion. Top Giiseofulvin crystals precipitated by the spontaneous emulsification method 10 mg giiseofulvin in 2.5 mL acetone poured into 5 mL of 0.1 % Polysorbate 20 aqueous solution (left x 20, bar=200pm right xlOO, bar=20pm). Bottom lOmg silicone oil and 64mg giiseofulvin in 2.5 mL acetone poured into 5 mL of 0.1 % Polysorbate 20 aqueous solution (x 20, bar=200 pm)...

Such polymers are not soluble in water and were successfully emulsified by means of the spontaneous emulsification method, yielding aqueous emulsions with nanometric sizes (mean diameters from 100 to 500nm). 

Xu, Q.Y., Nakajima, M., and Binks, B.P. (2005). Preparation of particle-stabilized oil-in-water emulsions with the microchannel emulsification method. Colloids Surf. A, Physicochem., Eng. Aspects, 262(1-3), 94-100. 

An emerging class of emulsification methods is not based on imposing an overall flow field, but rather by making individual droplets on the mouths of membrane pores or micro-engineered channels. Characteristic is that the flow fields applied are much milder energy consumption is much lower, while the droplet sizes are strongly dependent on the shape and dimensions of the pores or micro-channels. A number of processes belong to this class ... 

Suzuki, K., Shuto, I., and Hagura, Y. (1996). Characteristics of the membrane emulsification method combined with preliminary emulsification for preparing com oil-in-water emulsions. FoodSci. Technol. Int. 2, 43-47. 

Although water-immiscible solvents display low solubility in water, there is some amount of solubility. The solvent diffusion/emulsification method exploits this for the production of nanoparticles. In this technique, drug and polymer are dissolved in an organic, water-immiscible solvent that is emulsified into an aqueous solution containing emulsifiers and stabilizers. The emulsion is then diluted with water to increase the level of organic solvent, which can be dissolved in the... 

Chan LW, Lee HY, Heng PW. Production of alginate microspheres by internal gelation using an emulsification method. Int J Pharm 2002 242(1-2) 259-262. 

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