Monomers emulsification

When no NaCl is added to the SDS solution, the turbidity increase with slight dispersion of oleic acid is probably due to the monomer emulsification of the oleic acid. The process does not seem to require as much time and energy as solubilization. 

Since oleic acid is relatively polar, it may become emulsified by the surfactant monomer. The removal of oleic acid comes mainly from two contributions monomer emulsification and micellar solubilization. Although the Vgjj has been decreased with increasing EO number in dodecanol ethoxylates, in higher EO numbers than 5, this factor has been compensated by the Increase of monomer with increasing EO number (CMC decreases with EO number). The levelling of detergency of dodecanol ethoxylates from EO number 5 to EO number 8 has been interpreted by these reasons. The monomer emulsification of oleic acid has been clearly shown in this paper in SDS solution. The nonionic surfactants we used here have low EO numbers and show mainly the effect of solubilization. 

The negatively charged hydrophilic headgroup of the anionic surfactants may comprise sulfate, sulfonate, sulfosuccinate or phosphate groups attached to an extended hydrophobic backbone [82]. The nature of the hydrophilic group will influence the extent of electrostatic stabilization, the behaviour of the surfactant as a fiinction of pH, the degree of hydrolysis, and the variation of latex stability with time, electrolyte and temperature conditions. The nature of the backbone hydrophobe will influence the adsorption behaviour of the surfactant onto the latex particle surface, its cmc value, the interfacial tension (which affects monomer emulsification), and the extent of steric stabilization, among other factors. 

Monomer emulsions ate prepared in separate stainless steel emulsification tanks that are usually equipped with a turbine agitator, manometer level gage, cooling cods, a sprayer inert gas, temperature recorder, mpture disk, flame arrester, and various nossles for charging the ingredients. Monomer emulsions are commonly fed continuously to the reactor throughout the polymerisation. 

Early efforts to produce synthetic mbber coupled bulk polymerization with subsequent emulsification (9). Problems controlling the heat generated during bulk polymerization led to the first attempts at emulsion polymerization. In emulsion polymerization hydrophobic monomers are added to water, emulsified by a surfactant into small particles, and polymerized using a water-soluble initiator. The result is a coUoidal suspension of fine particles,... 

Emulsification is the process by which a hydrophobic monomer, such as styrene, is dispersed into micelles and monomer droplets. A measure of a surfactant s abiUty to solubilize a monomer is its critical micelle concentration (CMC). Below the CMC the surfactant is dissolved ia the aqueous phase and does not serve to solubilize monomer. At and above the CMC the surfactant forms spherical micelles, usually 50 to 200 soap molecules per micelle. Many... 

Emulsifiers are used in many technical applications. Emulsions of the oil-in-water and the water-in-oil type are produced on a large scale in the cosmetic industry. Other fields of employment are polymerization of monomers in emulsions and emulsification of oily and aqueous solutions in lubricants and cutting oils. In enhanced oil recovery dispersing of crude oil to emulsions or even microemulsions is the decisive step. 

An aqueous colloidal polymeric dispersion by definition is a two-phase system comprised of a disperse phase and a dispersion medium. The disperse phase consists of spherical polymer particles, usually with an average diameter of 200-300 nm. According to their method of preparation, aqueous colloidal polymer dispersions can be divided into two categories (true) latices and pseudolatices. True latices are prepared by controlled polymerization of emulsified monomer droplets in aqueous solutions, whereas pseudolatices are prepared starting from already polymerized macromolecules using different emulsification techniques. 

In interfacial polymerization, monomers react at the interface of two immiscible liquid phases to produce a film that encapsulates the dispersed phase. The process involves an initial emulsification step in which an aqueous phase, containing a reactive monomer and a core material, is dispersed in a nonaqueous continuous phase. This is then followed by the addition of a second monomer to the continuous phase. Monomers in the two phases then diffuse and polymerize at the interface to form a thin film. The degree of polymerization depends on the concentration of monomers, the temperature of the system, and the composition of the liquid phases. 

Sadurm, N., Solans, C., Azemar, N. and Garci a-Celma, M.J. (2005) Studies on the formation of O/W nano-emulsions, by low-energy emulsification methods, suitable for pharmaceutical aplications. Emulsion polymerization initiation of polymerization in monomer droplets., 26, 438-445. 

Latex or emulsion polymers are prepared by emulsification of monomers in water by adding a surfactant. A water-soluble initiator is added, e.g., persulfate or hydrogen peroxide (with a metallic ion as catalyst), that polymerises the monomer yielding polymer particles, which have diameters of about 0.1 pm. The higher the concentration of surfactant added, the smaller the polymer particles. 

Emulsifiable oil metal-working fluids, 1 22 Emulsification, 10 126 16 211 cosmetics, 7 837-841 hydrophobic-monomer, 14 717 Emulsified wax, in paper manufacture,... 

The surface active agents (surfactants) may be cationic, anionic or non-ionic. Surfactants commonly used are cetyltrimethyl ammonium bromide (CTABr), sodium lauryl sulphate (NaLS) and triton-X, etc. The surfactants help to lower the surface tension at the monomer-water interface and also facilitate emulsification of the monomer in water. Because of their low solubility surfactants get fully dissolved or molecularly dispersed only at low concentrations and at higher concentrations micelles are formed. The highest concentration where in all the molecules are in dispersed state is known as critical micelle concentration (CMC). The CMC values of some surfactants are listed in table below. 

Soap. The reaction product of a fatty acid ester and a metal hydroxide, usually sodium hydroxide. Soap lowers the surface tension of water, permitting emulsification of soil-bearing fats if the soap is used for washing, of monomers in solution if the soap is used for emulsification in a polymerization process. 6 e saponification. 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

The emulsification of the monomer takes place in the presence of water-soluble emulsifiers that can form micelles. At the beginning of the polymerization, the monomer is present in form of monomer droplets as well as in the micelles. 

The membrane emulsification technique is also employed for the preparation of microspheres starting from monomers such as methacrylates (methylmethacrylate, cyclohexyl acrylate, etc.), polyimide prepolymer, styrene monomer [81], and so on. 

The dispersions were obtained by emulsification via ultrasonication of a toluene solution of the unsaturated homopolymer in an aqueous surfactant solution. This was followed by exhaustive hydrogenation with Wilkinson s catalyst at 60°C and 80 bar H2 to produce a dispersion with an average particle size of 35 nm (dynamic light scattering and transmission electron microscopy analyses). The same a,co-diene was used as comonomer in the ADMET polymerization of a phosphorus-based monomer, also containing two 10-undecenoic acid moieties... 

If an oil-soluble monomer is dispersed in a continuous aqueous phase without the use of surfactants, suspension polymerization results. The viscosity of the resulting suspension will remain essentially constant over the course of the polymerization. Oil-soluble free radical initiators are used to effect polymerization. The monomer is dispersed into beads by the action of an agitator. Since little or no surfactant is used, no emulsification takes place, and, if the agitation is stopped, the monomer will form a separate bulk phase, usually above the aqueous phase. The monomer is polymerized by the initiator within the droplets, forming polymer beads of approximately the same size as the monomer droplets (0.1-10 mm diameter). The product can be readily separated from the aqueous phase (via filtration or decantation) in the form of macroscopic particles or beads, which can be easily packaged and/or transported. Heat transfer is facihtated by the presence of the continuous aqueous phase. Blocking agents such as clays or talcs are used to prevent particle ag-... 

With cetyl alcohol, there is the complication that the polarity of the molecule may cause it to reside at the surface of the droplet, imparting additional colloidal stability. Here, the surfactant and costabilizer form an ordered structure at the monomer-water interface, which acts as a barrier to coalescence and mass transfer. Support for this theory lies in the method of preparation of the emulsion as well as experimental interfacial tension measurements [79]. It is well known that preparation of a stable emulsion with fatty alcohol costabilizers requires pre-emulsification of the surfactants within the aqueous phase prior to monomer addition. By mixing the fatty alcohol costabilizer in the water prior to monomer addition, it is believed that an ordered structure forms from the two surfactants. Upon addition of the monomer (oil) phase, the monomer diffuses through the aqueous phase to swell these ordered structures. For long chain alkanes that are strictly oil-soluble, homogenization of the oil phase is required to produce a stable emulsion. Although both costabilizers produce re-... 

In the same work, it is also supposed that colloidal stability, rather than monomer ripening, plays an effective role in determining the final droplet size. Such a conclusion was supported by two different experimental results. First, it was noticed that droplet size increases right after the emulsification process stops, and a stable situation is typically achieved after just a few hours. However, if surfactant is added immediately after, this growth in size does not occur. Second, it is shown that there is a clear correlation between final droplet size and amount of oil phase used in the recipe. In particular, when the oil fraction in the system increases, droplet size also increases. 

Table I. OPB adsorbed on the monomer droplets after 15 minutes of stirring. HD dissolved in the water phase prior to emulsification.

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