Emulsion macro

The emulsifying properties of lipopeptides were tested in many oil/water systems. The oil was aromatic such as toluene and styrene, paraffinic such as decane and dodecane, or a base product of the cosmetic industry. Lipopeptides give 3 types of emulsions macro-... 

Kunieda H, John AC, Pons R, Solans C. Highly concentrated emulsions (gel emulsions) macro self-organizing structures. In Esumi K, Ueno M, eds. Structure-Performance Relationships in Surfactants. Vol. 70. Surfactant Science Series. New York Marcel Dekker, 1997 359-393. 

H. Kunieda, A.C. Johns, R. Pons and C. Solans, Highly Concentrated Emulsions -Gel Emulsions Macro-Self-Organizing Structures, in [41], pp. 359. 

Oil-in-water emulsion polymerization systems are typically classified as possessing the characteristics of one of three types of emulsions macro-emulsions, mini-emulsions or microemulsions. These emulsions are the initial systems for emulsion polymerization. There are quite differences between these systems in some aspects such as the size of the droplets (i.e. the discontinuous or dispersed phase), the interfacial area of the droplets, the particle nucleation mechanism and the stability of the emulsion. 

Microemulsions are treated in a separate section in this chapter. Unlike macro- or ordinary emulsions, microemulsions are generally thermodynamically stable. They constitute a distinctive type of phase, of structure unlike ordinary homogeneous bulk phases, and their study has been a source of fascination. Finally, aerosols are discussed briefly in this chapter, although the topic has major differences from those of emulsions and foams. 

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. 

A novel approach to RAFT emulsion polymerization has recently been reported.461529 In a first step, a water-soluble monomer (AA) was polymerized in the aqueous phase to a low degree of polymerization to form a macro RAFT agent. A hydrophobic monomer (BA) was then added under controlled feed to give amphiphilic oligomers that form micelles. These constitute a RAFT-containing seed. Continued controlled feed of hydrophobic monomer may be used to continue the emulsion polymerization. The process appears directly analogous to the self-stabilizing lattices approach previously used in macromonomer RAFT polymerization (Section 9.5.2). Both processes allow emulsion polymerization without added surfactant. 

Fluid loss additives are used are used to reduce the rate of fluid loss from the fracture to the formation and to naturally occurring macro- and micro-fractures within the formation. Silica flour (73,74), oil-soluble resins (75), diesel oil emulsions (5% by volume) (74) have also been used. 

Karbstein, H. and Schubert, H., 1995, Developments in the continuous mechanical production of oil-in-water macro-emulsions, Chemical engineering and processing, 34, 3, 205 - 211. 

J.L. Salager Macro Emulsions Stabilized by an Ethoxylated Fatty Alcohol and an Alkyl Quat Emulsion Type and Stability in View of the Phase Behavior. In Proceedings of the 3rd World Congress on Emulsions 1 -F-107, Lyon, France (2001). 

To conclude, research, applications and expectations with regard to emulsions are permanently evolving. Changes in the macro-economic context along with various political decisions (e.g., sustainable development. Registration, Evaluation and Authorisation of Chemicals (REACH) directive for the European Union) are factors which influence the conditions in which emulsion-based products are fabricated and used. It is probable that these changes will motivate technological developments and new advances in emulsion science. 

At this point, the concept of the linear collapsed Plateau border is introduced. The Plateau border is the area of bulk continuous phase between three adjacent droplets or cells in an emulsion or foam respectively. The collapsed border is, therefore, an extremely thin version, which can be represented macro-scopically, as the line of intersection of three films of zero thickness, at angles of 120°. 

In principle, the long-term stability can be greatly improved by replacing the internal (macro)emulsion by a wawoemulsion or, better still, a thermodynamically stable micro-emulsion. (We note that, in this context, the prefix micro denotes an entity that is smaller than nano )... 

In accordance with the Smith-Ewart theory, the nucleation of particles takes place solely in the monomer-swollen micelles which are transformed into polymer particles [16]. This mechanism is applicable for hydrophobic (macro)mon-omers (see Scheme 2). The initiation of emulsion polymerization is a two-step process. It starts in water with the primary free radicals derived from the water-soluble initiator. The second step occurs in the monomer (macromonomer)-swollen micelles by entered oligomeric radicals. 

Macroemulsions tend to separate into two phases. This is called demulsification. Demul-sification can be very slow so that even a macroemulsion might appear stable. Often macroemulsions are just called emulsions because all classical dispersions of oil and water were macroemulsions. In this section we use the term emulsion if it concerns a property of macro- and microemulsions. If we discuss the properties primarily of macroemulsions we use the full term. From the practical point of view micro- and macroemulsions are very different. That we discuss some properties together should not hide this fact. 

Emulsions are dispersions of two immiscible liquids, usually water and oil. We distinguish macro- and microemulsions. Macroemulsions are not thermodynamically stable. Droplets are typically 0.5 - 10/im in diameter. Microemulsions are thermodynamically stable and droplets are of the order of 5-100 nm in diameter. 

Sections 10.2 and 9.1, respectively). Hence, the observed generation of a concentrated gas-in-liquid (macro)emulsion which interacts readily with simultaneously formed large (rodlike) micelles, using the above surfactant mixtures, is to be expected from and confirms such molecular packing considerations. 

Emulsification/demulsification (both macro- and micro-emulsions)... 

While microemulsions are thermodynamically stable, and the stability of emulsions has a kinetic origin, in both cases the adsorption of the dispersant upon the interface of the globules is responsible for stability. For this reason it appears natural to attempt to explain the above equality between the two inversion temperatures on the basis of surfactant adsorption. In addition, both the micro and macro-emulsions obey in many cases the Bancroft rule [8,9], which indicates that the phase in which a larger amount of dispersant is present becomes the continuous phase there are, however, some violations of this rule which will be discussed later in the paper. 

The copolymerization of monomers where one of the monomers acts as the hydrophobe was reported by Reimers and Schork [26]. MMA was copolymerized with p-methylstyrene, vinyl hexanoate, or vinyl 2-ethylhexanoate. The resulting copolymer composition tended to follow the predictions of the reactivity ratios, i.e., the reaction progresses as a bulk reaction. In contrast, copolymer compositions obtained from the (macro)emulsion copolymerizations tended to be more influenced by the relative water solubility of the comonomer and mass transfer. Wu and Schork used monomer combinations with large differences in reactivity ratios and water solubility vinyl acetate/butyl acrylate,... 

Different techniques are available to carry out a free radical polymerization in emulsion. In spite of the fact that their names (macro-, mini- and microemul-... 

Batch miniemulsion polymerization of MMA using PMMA as the costabilizer was carried out with SLS as the surfactant and KPS as the initiator. Solids content was kept at -30%. A low surfactant level was used with the miniemulsions to ensure droplet nucleation. The initiator concentration of the polymer-stabilized miniemulsion polymerizations was varied from 0.0005 to 0.02 Mjq, based on the total water content. An aqueous phase retarder, (sodium nitrite) or an oil-phase inhibitor (diphenylpicrylhydrazol [DPPH]), was added to both the miniemulsions and the macro emulsions prior to initiation. Particle numbers and rates of polymerization for both systems were determined. 

Therefore, we may conclude that there is indeed no significant difference in polydispersity between the miniemulsion and the equivalent macro emulsion. 

While the rate of monomer transport in macro emulsions may or may not limit the rate of polymerization, it is quite possible that unequal rates of diffusions for comonomers may make the comonomer composition at the locus different (richer in the more water-soluble monomer) from the overall composition. 

In summary, the semibatch feeding of neat monomer or a macroemulsion of monomer to a miniemulsion does not differ substantially from the equivalent semibatch feeding into a macro emulsion. The semibatch feeding of a... 

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