Emulsifier natural polymeric

Some natural polymeric emulsifiers such as the gums, in addition to forming steric and electrostatic... 

The surfactants used for the preparation of disperse systems are seldom effective in maintaining the long-term physical stabihty (absence of flocculation and/or coalescence) of the formulation. This is due to their weak and reversible adsorption and lack of the presence of a high-energy barrier that prevents flocculation as a result of van der Waals attractions. For this reason, dispersants and emulsifiers of polymeric nature that are strongly and irreversibly adsorbed at the interface are required. In addition, these polymeric dispersant provide effective repulsive forces (referred to as steric repulsion) that overcomes the van der Waals attractions. The criteria for an effective dispersant are [1, 2] ... 

This paper focuses on heterophase free radical polymerizations. It is limited to processes where multiple phases, distinguished by the insolubility of reagents, exists at the onset of the reaction. It therefore does not consider precipitation polymerization [1], which occurs when the polymer is insoluble in the monomer and precipitates out from an initially homogeneous solution. It also does not address emulsifier-free polymerization or dispersion polymerization. This rather general nomenclature is now accepted as applying to specific systems where the heterophase nature is produced at the onset of the reaction by homogeneous nucleation of oligomers or polymer chains which have exceeded their solubility limit [2]. 

Latex-based polymer materials can be either nature-made, as natural rubber [Stern, 1967 White, 1995], or synthetically made. The synthetically made latexes are commonly based on recipes of monomer, water, surfactant, and free radical initiator to induce chain polymerization [Lovell and El-Aasser, 1997 Wickson, 1993], However, recipes based on step polymerization are also well known, often resulting in crossUnked films [Walker and Shaffer, 1996], The resulting latex material consists of small particles, usually spherical, of 50-500 nm in diameter, dispersed in water. Alternately, polymers are sometimes emulsified after polymerization (direct emulsification, the product sometimes called artificial latexes) via agitation of a melt in the presence of water and surfactant (emulsifier), and sometimes organic solvent or plasticizer [Piirma, 1989]. 

It is the simplest approach, where suitable monomer (precursor of CP/ ICP) has been polymerized (Figure 1.45) in the presence of dispersed filled inclusion (another CP metallic, dielectric, or magnetic NPs QCNs any suitable combination of them). Depending upon the nature of reaction medium (i.e., presence of solvent, dispersant, or emulsifier), the polymerization may proceed via bulk, solution, suspension, or emulsion route [14,375,502]. During the process, monomer(s) tends to adsorb over filler and polymerize over the same, thereby enwrapping it and causing its dispersion within the formed polymer matrix. 

Chem. Descrip. Fatty acid sulfate, sodium salt Ionic Nature Anionic Uses Emulsifier for polymerization Properties Dk. amber liq. 70% act. 

Ionic Nature Anionic Uses Emulsifier for polymerization Ammonium nonoxynol-30 sulfate CAS 9051-57-4 (generic) 31691-97-1 (generic)... 

Uses Antistat for syn. Abets and polymer prods. surfactant, wetting agenL dispersant emulsifier for polymerization, personal care Nonoxynol-10 sulfate Synonyms Nonyl phenol ethoxy (10) sulfote Ionic Nature Anionic... 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Emulsion Polymerization. When the U.S. supply of natural mbber from the Far East was cut off in World War II, the emulsion polymerization process was developed to produce synthetic mbber. In this complex process, the organic monomer is emulsified with soap in an aqueous continuous phase. Because of the much smaller (<0.1 jira) dispersed particles than in suspension polymerization and the stabilizing action of the soap, a proper emulsion is stable, so agitation is not as critical. In classical emulsion polymerization, a water-soluble initiator is used. This, together with the small particle size, gives rise to very different kinetics (6,21—23). 

Mixing of latex compounds is accompHshed by stirring ingredients into the latex in the form of water solutions, dispersions, or emulsions. Although the mbber softeners needed to process dry mbber are not necessary for latex, use of emulsified softeners or polymeric plasticizers in natural or synthetic latex compounds provides lower modulus in the finished products. This reduces hand fatigue and increases touch sensitivity in dipped mbber gloves. Mineral oils are also used as an economy. 

Most synthetic latices contain 5—10 wt % of nonelastomeric components, of which more than half is an emulsifier or mixture of emulsifiers. One reason for this relatively high emulsifier concentration as compared with natural latex is that emulsifier micelles containing solubiHzed monomer play a principle role in the polymerization process. A high emulsifier concentration is usually necessary to achieve a sufficiently rapid rate of polymerization. Secondly, a considerable fraction of the surface of the polymer particles must be covered by adsorbed soap or equivalent stabilizer to prevent flocculation... 

There are some applications for a-sulfo fatty acid esters in the production and processing of synthetic materials or natural rubber. Emulsifiers are needed for the emulsion polymerization, antistatic agents improve the properties of polymers, and wetting agents are needed as parting components for elastomers. 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

For the characterization of Langmuir films, Fulda and coworkers [75-77] used anionic and cationic core-shell particles prepared by emulsifier-free emulsion polymerization. These particles have several advantages over those used in early publications First, the particles do not contain any stabihzer or emulsifier, which is eventually desorbed upon spreading and disturbs the formation of a particle monolayer at the air-water interface. Second, the preparation is a one-step process leading directly to monodisperse particles 0.2-0.5 jim in diameter. Third, the nature of the shell can be easily varied by using different hydrophilic comonomers. In Table 1, the particles and their characteristic properties are hsted. Most of the studies were carried out using anionic particles with polystyrene as core material and polyacrylic acid in the shell. 

Of the several types of the polymer-modified mortars and concretes used for various construction applications, latex-modified mortar and concrete are by far the most widely used materials. Latex-modified mortar and concrete are prepared by mixing a latex, either in a dispersed liquid or as a redispersible powder form with fresh cement mortar and concrete mixtures. The polymers are usually added to the mixing water just as other chemical admixtures, at a dosage of 5-20% by weight of cement. Polymer latexes are stable dispersions of very small (0.05-5 pm in diameter) polymer particles in water and are produced by emulsion polymerization. Natural rubber latex and epoxy latex are exceptions in that the former is tapped from rubber trees and the latter is produced by emulsifying an epoxy resin in water by the use of surfactants [87]. 

Surfactants play a major role in the preparation of suspensions of polymer particles by heterogeneous nucleation. In emulsion polymerization, the monomer is emulsified in a nonsolvent (usually water) using a surfactant, whereas the initiator is dissolved in the continuous phase. The role of surfactants in this process is obvious since nucleation may occur in the swollen surfactant micelle. Indeed, the number of particles formed and their size depend on the nature of surfactant and its concentration (which determines the number of micelles formed). 

Another class of surfactants that are used in cosmetics and personal care products is the phosphoric acid esters. These molecules are similar to the phospholipids that are the building blocks of the stratum corneum (the top layer of the skin, which is the main barrier for water loss). Glycerine esters, in particular, triglycerides, are also frequently used. Macromolecular surfactants of the A-B-A block type [where A is PEO and B is polypropylene oxide (PPO)] are also frequently used in cosmetics. Another important naturally occurring class of polymeric surfactants is the proteins, which can be used effectively as emulsifiers. 

These applications exploit the polymeric nature of starch in gelling, emulsifying and mouthfeel enhancement. 

Polyglycerol esters of fatty acids are produced by reacting polymerized glycerol with edible fats. The degree of polymerization of the glycerol and the nature of the fat provide a wide range of emulsifiers with different HLB values. 

Qnulsion polymerization of lower alkyl acrylates was studied in terms of Interfacial phenomena. Adsorption of emulsifier depending on its nature reduces during... 

The conditions which have been defined for the formation of effective microemulsions (nature of the oil, Ro and HLB values) are also required for obtaining clear and stable microlatices after polymerization. Various water-soluble monomers have been polymerized by a free radical process in anionic and nonionic microemulsions, either under U.V. irradiation or thermally with AIBN as the initiator (11,14,22,29). Total conversion to polymer was achieved in less than 20 minutes (a few minutes in some cases). Series of experiments have been performed in various oils. Table III summarizes some of the results and emphasizes the importance of the formulation. A good chemical matching between oils and emulsifiers (G 1086 -t Arlacel 83, Isopar H) leads to stable latices, a poor matching (G 1086 Arlacel 83, heptane) leads to unstable latices which settle within a few hours to a few days (22). 

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