Emulsion colloid technique

Micro Structured metals have recently been coated by the sol-gel technique to obtain a Cu-Zn-Al catalyst system or by the emulsion colloid technique, which is similar to a standard washcoating procedure, to obtain a PdZn/ZnO catalyst system... 

Another application of microparticle technology is the production of polymeric microspheres, which are usually produced by emulsion polymerization techniques. But a variety of polymer colloids can be made by aerosol techniques (Partch et al, 1983 Nakamura et al, 1984 Partch et al, 1985). One advantage of the aerosol route is that larger sizes can be attained... 

Emulsion polymerization typically refers to the polymerization of a nonaqueous material in water. The polymerization of a water-soluble material in a nonaqueous continuum has been called inverse emulsion polymerization. The inverse emulsion polymerization technique is used to synthesize a wide range of polymers for a variety of applications such as wall paper adhesive, waste water fiocculant, additives for oil recovery fluids, and retention aids. The emulsion polymerization technique involves water-soluble polymer, usually in aqueous solution, emulsified in continuous oil phase using water in oil emulsifier. The inverse emulsion is polymerized using an oil- or water-soluble initiator. The product is a colloidal dispersion of sub-microscopic particles with particle size ranging from 0.05 to 0.3 pm. The typical water-soluble monomers used are sodium p-vinyl benzene sulfonate, sodium vinyl sulfonate, 2-sulfo ethyl acrylate, acrylic acid, and acrylamide. The preferred emulsifiers are Sorbitan monostearate and the oil phase is xylene. The proposed kinetics involve initiation in polymer swollen micelles, which results in the production of high molecular weight colloidal dispersion of water-swollen polymer particles in oil. 

Dispersion or plastisol resins are made exclusively by emulsion polymerization techniques. A vinyl latex is a colloidal suspension (emulsion) of the homo-copolymer particle in water. (The 0.2 )jm average particle size is small enough to be in Brownian movement.) Soaps are generally used to form a protective colloid around the particle, and they are surrounded by a negative electrical charge. In some cases air-dry film-forming systems are possible. 

The oil extracted from a well usually contains water dispersed as a fine emulsion. The de-emulsification of the oil is an important part of the overall processing, and improved and more economical methods of achieving this depend on the application of colloid techniques. 

Granular media filtration is only marginally effective in treating colloidal size particles in suspensions. Usually these particles can be made larger by flocculation although this will reduce run length. In cases where it is not possible to flocculate such particles (as in the case of many oil/water emulsions), other techniques such as ultrafiltration may be nessesary. 

Clearly, an objective of commercial production is to obtain a stable latex which has as high a solids content as remains consistent with producing the required balance of pol3naer properties after drying. The colloidal stability of latices is enhanced by the addition of surfactants. Latices prepared by emulsion pol3mierisation techniques usually have solids content of 40-45%. The kinetics and mechanism of emulsion polymerisation of VCM have been extensively reviewed by Ugelstad et al (9). 

One distinct advantage of the emulsion polymerization technique is that latex products are often used directly without prior separation of polymer from water. For example, coatings formulated primarily with emulsion polymers are essential to the beauty and protection of many objects such as houses, furniture, leathern products, and packaging materials. The performance properties of emulsion polymers of major interest to this section include rheology and film formation related to the colloidal phenomena. These performance properties play a crucial role in determining the ultimate mechanical properties of the polymeric films. 

Matsumoto S, Kohda M, Murata S. 1977. Preparation of lipid vesicles on the basis of a technique for providing W/O/W emulsions. / Colloid Interface Sci 62(1) 149-157. 

Among aU these various polymerization processes, one major advantage of emulsion polymerization techniques is that according to the selected recipe, it is really possible to carefully adjust both macromolecular and colloidal properties of the obtained latexes, which is quite versatile in view of the variety of applications. For specialty ones, the control of particle size, particle size distribution, surface morphology, surface chemistry and functionality etc. is indeed of paramount importance. In that purpose, emulsion polymerization has long been proved to be appropriate in the synthesis of functional latex particles (Arshady, 1999 Kawaguchi etaL, 2003). 

The compounding technique for latex differs from that of dry mbber and is fundamentally simpler. A critical factor of colloidal stabiUty makes necessary that each ingredient is of optimum particle size, pH, and concentration when added as an aqueous dispersion to the latex. Rubber latex is a colloidal aqueous emulsion of an elastomer and natural mbber latex is the milky exudation of certain trees and plants that of greatest commercial importance is the... 

This chapter describes the basic principles involved in the development of disperse systems. Emphasis is laid on systems that are of particular pharmaceutical interest, namely, suspensions, emulsions, and colloids. Theoretical concepts, preparation techniques, and methods used to characterize and stabilize disperse systems are presented. The term particle is used in its broadest sense, including gases, liquids, solids, molecules, and aggregates. The reader may find it useful to read this chapter in conjuction with Chapters 8, 12, and 14, since they include some of the most important applications of disperse systems as pharmaceutical dosage forms [1]. 

K Heinzelmann, K Franke. Using freezing and drying techniques of emulsions for the microencapsulation of fish oil to improve oxidation stability. Colloids Surfaces B Biointerfaces 12(3—6) 223—229, 1999. 

K. Kandori, K. Kishi, and T. Ishikawa Preparation of Monodispersed W/O Emulsions by Shirasu-Porous-Glass Filter Emulsification Technique. Colloid Surfaces 55, 73 (1991). 

Rowe RC, McMahon J. The characterisation of the microstructure of gels and emulsions containing cetostearyl alcohol and cetrimide using electron microscopy—a comparison of techniques. Colloid Surf 1987 27 367-373. 

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