Emulsions factors affecting

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

In addition to graft copolymer attached to the mbber particle surface, the formation of styrene—acrylonitrile copolymer occluded within the mbber particle may occur. The mechanism and extent of occluded polymer formation depends on the manufacturing process. The factors affecting occlusion formation in bulk (77) and emulsion processes (78) have been described. The use of block copolymers of styrene and butadiene in bulk systems can control particle size and give rise to unusual particle morphologies (eg, coil, rod, capsule, cellular) (77). 

Bailey, A.L, Cardenas-Valera, A.E., Graft copolymers as stabilizers for oil-imwater emulsions. Part 2. Preparation of the emulsions and the factors affecting their stability. Colloids and Surfaces, v.97, pp.1-12, 1995. 

C. B. Lalor, G. L. Flynn, and N. Weiner. Formulation factors affecting release of drug from topical formulations. I. Effect of emulsion type upon in vitro delivery of ethyl p-aminobenzoate. J. Pharm. Sci. 83 1525-1528 (1994). 

The amount of water solubilized in a reverse micelle solution is commonly referred to as W, the molar ratio of water to surfactant, and this is also a good qualitative indicator of micelle size. This is an extremely important parameter since it will determine the number of surfactant molecules per micelle and is the main factor affecting micelle size. For an (AOT)/iso-octane/H20 system, the maximum Wq is around 60 [16], and above this value the transparent reverse micelle solution becomes a turbid emulsion, and phase separation may occur. The effect of salt type and concentration on water solubilization is important. Cations with a smaller hydration size, but the same ionic charge, result in less solubilization than cations with a large hydration size [17,18]. Micelle size depends on the salt type and concentration, solvent, surfactant type and concentration, and also temperature. 

In applying oil sprays to fruit trees, the objective is to apply an evenly distributed deposit of oil sufficient to effect control of the pest while remaining below the deposit that will produce plant injury. The margin of safety is relatively small in some cases. Recent attempts have been made to apply straight oils in the form of mists or as concentrated emulsions, but this method of application is still in the experimental stage. The quantity of oil deposited bears a direct relationship to both the effectiveness of insect control and safety of the tree. The most important factors affecting deposit are concentration of oil in the spray mixture, the nature and concentration of the emulsifier used, and the quantity of spray applied. 

Most, if not all, milks contain sufficient amounts of lipase to cause rancidity. However, in practice, lipolysis does not occur in milk because the substrate (triglycerides) and enzymes are well partitioned and a multiplicity of factors affect enzyme activity. Unlike most enzymatic reactions, lipolysis takes place at an oil-water interface. This rather unique situation gives rise to variables not ordinarily encountered in enzyme reactions. Factors such as the amount of surface area available, the permeability of the emulsion, the type of glyceride employed, the physical state of the substrate (complete solid, complete liquid, or liquid-solid), and the degree of agitation of the reaction medium must be taken into account for the results to be meaningful. Other variables common to all enzymatic reactions—such as pH, temperature, the presence of inhibitors and activators, the concentration of the enzyme and substrate, light, and the duration of the incubation period—will affect the activity and the subsequent interpretation of the results. 

The sizes of the droplets in the initial emulsion significantly affect the size and properties of the microspheres (Table 6)36). As the mixing rate used to produce the emulsions is increased, the average size of the droplets decreases whereas the microsphere size increases. Very dispersed emulsions seem to be more likely to coalesce, thus yielding larger droplets and hence larger microspheres after the heat treatment. This method can produce spherical unicellular particles with diameters of200-400 pm, densities of 260-700 kg/m3, and space factors of up to 59% 35 36). 

Juliano, R. L. (1988) Factors affecting the clearance kinetics and tissue distribution of liposomes, microspheres and emulsions dv. Drug Deliv. Rev., 2 31-54. 

Formulation factors affecting the oral bioavailability from conventional dosage forms such as solutions, suspensions, emulsions, capsules and tablets are described here. 

Boyd, J., Parkinson, C., Sherman, P. 1972. Factors affecting emulsion stability and the HLB concept. J. Coll. Inter/. Sci. 41, 359-370. 

TABLE 2 Formulation Factors Affecting Metabolism as Lipoproteins, Recognition by Mononuclear Phagocyte System (MPS), and Elimination from Blood Circulation of Second- and Third-Generation Nanosized Emulsions after Parenteral Administration... 

Very often, the microstructure and the macroscopic states of dispersions are determined by kinetic and thermodynamic considerations. While thermodynamics dictates what the equilibrium state will be, kinetics determine how fast that equilibrium state will be determined. While in thermodynamics the initial and final states must be determined, in kinetics the path and any energy barriers are important. The electrostatic and the electrical double-layer (the two charged portions of an inter cial region) play important roles in food emulsion stability. The Derjaguin-Landau-Verwey-Oveibeek (DLVO) theory of colloidal stability has been used to examine the factors affecting colloidal stability. 

Figure 13. Electrophoretic mobility (Fen Kem 3000) of the emulsion from Figure 12 after cationic polymer addition (A). The cationic polymer has neutralized the oil droplet surface charge and electrostatically destabilized the emulsion. The photomicrograph (B) shows this destabilized emulsion that has begun to flocculate or a lomerate but that is not coalescing. This electrostatic destabilization is not the only factor affecting emulsion stability. Factors such as interfacial tension and film strength can prevent coalescence of the emulsion droplets, even though they can now closely approach each other and ag omer-...

Effect of Emulsion Characteristics. As discussed in Chapter 4, the rheology of emulsions is affected by several factors, including the dis-persed-phase volume fraction, droplet size distribution, viscosity of the continuous and dispersed phases, and the nature and amount of emulsifying surfactant present. All of these parameters would be expected to have some effect on flow behavior of the emulsion in porous media. However, the relationship between bulk rheological properties of an emulsion and its flow behavior in porous media is feeble at best because, in most cases, the volume... 

Several factors affect demulsifier performance temperature, pH, and the nature of the aqueous-phase salt. In most cases, an increase in temperature results in a decrease in emulsion stability. Consequently, for a particular emulsion, less demulsifier is required at higher treating temperatures to effect the same degree of treatment. Studies (i) on the effect of pH on the instability of crude-oil-water emulsions have shown that a pH of 10.5 produced the least stable emulsions. Furthermore, basic pH produced oil-inwater emulsions and acidic pH generated water-in-oil emulsions. 

It is purpose of this paper to present the experimental results obtained from a series of the works on the W/O/W emulsions in the author s laboratory in order to search further insights into the factors affecting the formation and stability of W/O/W-type dispersion. 

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