Emulsion stability polymer

PVP was one of the first successful hair fixative resins (Section III) (44). However, in this application today, it is more frequently present as a copolymer. PVP homopolymer is often employed in solution-based personal care products as a viscosifying and emulsion-stabilizing polymer. Simple emulsions that employ PVP benefit from its stabilizing effects. It has been suggested that, although solutions of PVP display yield stress, the magnitude of this effect is not always sufficient to stabilize emulsions, especially complex multiple ones (45). 

Until recently, the manufacture of high molecular weight acrylamide polymers or copolymers was accomplished by one of two methods. The polymers could be produced as water-in-oil emulsions (or "latex" polymers), consisting of a hydrocarbon-based solvent for the continuous phase and various surfactants to provide emulsion stability. Polymers prepared in this fashion are generally 20% to... 

An important industrial example of W/O emulsions arises in water-in-crude-oil emulsions that form during production. These emulsions must be broken to aid transportation and refining [43]. These suspensions have been extensively studied by Sjoblom and co-workers [10, 13, 14] and Wasan and co-workers [44]. Stabilization arises from combinations of surface-active components, asphaltenes, polymers, and particles the composition depends on the source of the crude oil. Certain copolymers can mimic the emulsion stabilizing fractions of crude oil and have been studied in terms of their pressure-area behavior [45]. 

The inverse emulsion form is made by emulsifying an aqueous monomer solution in a light hydrocarbon oil to form an oil-continuous emulsion stabilized by a surfactant system (21). This is polymerized to form an emulsion of aqueous polymer particle ranging in size from 1.0 to about 10 pm dispersed in oil. By addition of appropriate surfactants, the emulsion is made self-inverting, which means that when it is added to water with agitation, the oil is emulsified and the polymer goes into solution in a few minutes. Alternatively, a surfactant can be added to the water before addition of the inverse polymer emulsion (see Emulsions). 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

An emulsion that is, for instance, stable over many years at low droplet volume fraction may become unstable and coalesce when compressed above a critical osmotic pressure 11. As an example, when an oil-in-water emulsion stabilized with sodium dodecyl sulfate (SDS) is introduced in a dialysis bag and is stressed by the osmotic pressure imposed by an external polymer solution, coarsening occurs through the growth of a few randomly distributed large droplets [8]. A microscopic image of such a growth is shown in Fig. 5.1. 

Another important emulsion stabilization is achieved by using polymers. The large polymer molecules adsorbed on solid particles (Figure 9.6) will exhibit repulsion at the surface of the particles. The charged polymers also will give additional charge-charge repulsion. Polymers are used in many pharmaceutical, cosmetics, and other systems (milk). Obviously, the choice of a suitable polymer is specific to each system. 

The mechanical properties are also affected by the surfactant concentration in the emulsion precursor. Maxima in both crush strength and Young s modulus were shown at the surfactant concentration for optimum emulsion stability. Foams prepared from 100% styrene were found to have much lower compressive moduli than those containing DVB [130], This was attributed to plasticisa-tion of the polymer by the surfactant. 

Benichou, A., Aserin, A., Garti, N. (2002). Double emulsions stabilized by new molecular recognition hybrids of natural polymers. Polymers for Advanced Technologies, 13,1019-1031. 

This deficiency has been overcome by the development of "lipophilic" starches (18,19) starch hydrolyzates incorporating a covalently bound lipophilic species, 1-octenyl succinate. In this manner, a lipophilic polymer is produced which allows for excellent aqueous flavor emulsion stability, good water solubility (40% w/w), excellent retentions of the volatile flavoring material following drying and minimal "extractable" oil in the finished product (9), functional properties only exhibited by gum arabic prior to their development. 

Given the excellent lemon oil-incorporated emulsion stabilities of both polymers, the excellent dryer retention performance of the Control material and good lemon oil retentions using the Oxidized starch, scaled-up systems were prepared and dried. One... 

C.D. Smith, Vinyl acetate ethylene emulsions stabilized with poly(eth-ylene/poly (vinyl alcohol) blend, US Patent 6 673 862, assigned to Air Products Polymers, L.P. (Allentown, PA), January 6, 2004. 

Polymer Stabilization. Polymers have so far been used comparatively less than the common surfactants to stabilize emulsions in spile of the fact that excellent stabilization by them can be achieved. Application probably has been limited because the adsorption of polymers to emulsion droplets has displayed some intricate phenomena small changes in polymer structure or in solvent properties may lead to drastic changes in adsorption... 

Itaconic acid is a specialty monomer that affords performance advantages to certain polymeric coatings (qv) (see Polyesters, unsaturated). Emulsion stability, flow properties of the formulated coating, and adhesion to substrates are improved by the acid. Acrylonitrile fibers with low levels of the acid comonomer exhibit improved dye receptivity which allows more efficient dyeing to deeper shades (see Acrylonitrile polymers Fibers, acrylic) (10,11). Itaconic acid has also been incorporated in PAN precursors of carbon and graphite fibers (qv) and into ethylene ionomers (qv) (12). 

M. H. Kabir, M. Ishitobi, and H. Kunieda, Emulsion stability in sucrose monoalkanoate system with addition of cosurfactants, Colloid Polym. Sci., 280 (2002) 841-847. 

Instead of conventional surfactant molecules, amphiphilic water soluble macromonomers, especially PEO macromonomers, have been used extensively as a reactive emulsifier and as steric stabilizer polymer, as summarized in Table 5. Generally speaking, however, the mechanism for the particle nucleation in the emulsion polymerization systems using macromonomers has been poorly established when compared to the dispersion copolymerizations with macromonomers as mentioned earlier. 

Residual materials (e.g., surfactants, emulsifiers) from polymerization which remain on the surface of the resin particle can exhibit unique secondary manifestations of degradation, such as poor heat and light stability and susceptibility to fungal attack not associated with the polymer itself. This is particularly true of emulsion-prepared polymers (dispersion or paste resins) where the surfactant level may be as high as 3% to provide appropriate rheological properties to the resin. 

The kinetics of vinyl acetate emulsion polymerization in the presence of alkyl phenyl ethoxylate surfactants of various chain lengths indicate that part of the emulsion polymerization occurs in the aqueous phase and part in the particles (115). A study of the emulsion polymerization of vinyl acetate in the presence of sodium lauryl sulfate reveals that a water-soluble poly (vinyl acetate)—sodium dodecyl sulfate polyelectrolyte complex forms, and that latex stability, polymer hydrolysis, and molecular weight are controlled by this phenomenon (116). 

TABLE 2. Emulsion stability of selected amphiphilic copolymers prepared by adding 1.5 g of a selected experimental polymer to an oil/water mixture and blending at 90° C to 100° C. 

A keto acid ester such as allyl levulinate may be crosaUxlced by adipic acid hydrazide, and some unsaturated diketones or keto-acids would probably react similarly. Polymers have been descriled in bead form, but conditions could probably be found to enstire emulsion stability. (55)... 

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