Emulsions particle sizes

Emulsion. a larger quantity of emulsifier is employed, resulting in a fine particle size emulsion. The polymer after spray drying, is a finely divided powder suitable for use in organosols and plastisols. 

The oil-rich layer eventually coagulated to form an oil layer this type of separation was described as mixed-particle-size emulsion by Tadros and Vincent (1 ). The addition of sodium chloride to the water used in making the emulsion gave faster emulsion separation especially for high NaOH (5 x 10 or greater) concentration emulsions. When the NaCl content exceeded 2.0%, no homogeneous emulsion could be obtained as separation occurred immediately. 

Uses Epoxy for water dilution in combination with amine curing agents, forming fine particle size emulsions useful as modifiers for Portland cement, concrete, mortars, stuccos, grouts, as binders for trowel-applied floor toppings, as bond coats, base coats, membrane coatings, and sealers... 

Chem. Descrip. Microcrystalline wax emulsion EINECS/ELINCS 264-038-1 Uses Rub resist, aid in matte coatings Features Largest particle size emulsion Jonwax 120 [S.C. Johnson Polymer]... 

Highly hydrophilic version of AEROSOL NPES 2030. Primary surfactant for emulsion polymerization of acrylic, vinyl acetate and styrene-acrylic systems. Very fine particle size emulsions. Forms films with superior water-resistance. 

Polymer Areas For preparation of vinyl acetate and acrylic latexes, especially cross-linkable types. Used with N-methyl-olacrylamlde without detracting from cross-linking properties. Effective as post stabilizer. Generates small particle size emulsions. 

Polymer Areas Emulsion polymerization of vinyl acetate, acrylic, and styrene-acrylic systems. Very small particle size emulsions with excellent wet adhesion properties. 

Greth and Wilson [100] successfully applied, in the emulsion polymerization of unsaturated monomers, a method of classifying emulsifiers based on the HLB (hydrophilic/lipophilic balance) value. They plotted the most important properties of the emulsion polymerization system, i.e., the latex stability, particle size, emulsion viscosity, and rate of polymerization against the HLB value of emulsifiers used. The dependence is described by a curve with maximum or minimum at a certain value of HLB, as it is expected from the micellar model [6, 7]. 

Ionic surfactants generally have a lower CMC than non-ionic surfactants. Ionic surfactants can be sub-divided into two types i) anionic and ii) cationic. Anionics are frequently used on their own or in conjunction with non-ionic types where their low CMC s provide low particle size emulsions. However, their use has a tendency to induce foaming and enhance water sensitivity in the final coating. They can also give long term storage problems. 

Acrysol WS-68 is a small particle size emulsion of an acrylic copolymer containing acid groups which solubilise the polymer when the amine is added. Cymel 303 is monomeric melamine-formaldehyde resin which crosslinks the acid groups in the acrylic copolymer. The p-toluene sulphonic acid catalyses the crosslinking reaction after the DMAE evaporates during the stoving operation. 

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

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). 

There are two principal PVC resins for producing vinyl foams suspension resin and dispersion resin. The suspension resin is prepared by suspension polymerization with a relatively large particle size in the 30—250 p.m range and the dispersion resin is prepared by emulsion polymerization with a fine particle size in the 0.2—2 p.m range (245). The latter is used in the manufacture of vinyl plastisols which can be fused without the appHcation of pressure. In addition, plastisol blending resins, which are fine particle size suspension resins, can be used as a partial replacement for the dispersion resin in a plastisol system to reduce the resin costs. 

Eor the preparation of suspensions and emulsions, coUoid mills and homogenizers, respectively, are used. Ultrasonic mills that utilize vibrating reeds in restricted chambers to reduce the particle size of the dispersed ingredients can also be employed (see Colloids Ultrasonics). 

These pigments are sensitive to heat and bleed ia most paint solvents. They are, however, resistant to acids and bases. Their tinctorial strength is considerably greater than that of inorganic yellows but they are weaker than the diaryUde yellows. They are used extensively ia emulsion paints, paper coating compositions, inks (qv), and, depending on particle size, can ia some cases be used outdoors because of excellent lightfastness ia full shades. 

Emulsion polymeriza tion of ABS (241) gives a mbber-phase particle morphology which is mostly deterrnined by the mbbet-seed latex. Since the mbber particle size, polydispersity, and cross-linking ate estabhshed before the preparation, the main variables relate to grafting, molecular weight... 

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