Surfactant-stabilized latex

Fig. 1.24 The three intervals of a typical emulsion polymerization reaction, showing surfactant molecules ( "), large monomer droplets, micelle (indicated by clusters of surfactant molecules within Interval 1), radicals (R ), initiator (1) and surfactant-stabilized latex particles (Reprinted from Thickett and Gilbert [274]. Copyright 2009, with permission from Elsevier)...

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). 

MYKON NRW-4 surfactant is an excellent wetting agent. At low concentration it can be used in water repellent finishes without causing rewetting of the fabric after drying. MYKON NRW-4 surfactant can also be used to stabilize latex finishes and can be used in standard resin finishes. 

Also, the solid particles may contain water-soluble substances, which undergo leaching and specific adsorption. Reference [1865] reports the IEP of phosphate-containing goethite. One sample studied in [32] contained sulfate and phosphate, and its IEP and PZC differed significantly. The silica studied in [2929] was prepared in the presence of a nonionic surfactant. No attempt was made to remove that surfactant from the final product. Phosphate-doped titania was studied in [2930] and polymer-stabilized latex was studied in [2931], A few results presented above have been cited by others as pristine PZCs/IEPs. 

When a water-soluble initiator is added to a microemul-sion, polymer particles are nucleated mainly by the micellar mechanism. The role of the monomer-swollen micelles in microemulsion polymerization is not only to act as nucle-ation loci and surfactant reservoir but also as monomer reservoir. The fast nucleation rate leads to the initial increment of Rp. As the monomer is polymerized, its concentration in micelles diminishes and eventually monomer concentration within polymer particles decreases as well [205]. As a consequence, the nucleation and polymerization rates tend to decrease, explaining in this way the maximum in the Rp evolution curve experimentally observed. The final latex consists of surfactant-stabilized polymer particles that typically contain only polymer and empty micelles formed by excess surfactant. 

Generally, the mechanical and chemical stabilities of latexes are improved with an increase in the content of the surfactants selected as stabil izers, and the stabilized latexes can disperse effectively without coagulation in latex-modified mortar and concrete. On the other hand, an excess amount of surfactant may have an adverse effect on the strength of the latex-modified mortar and concrete because of the reduced latex film strength, the... 

Chem. Deserp. Sodium allyloxy hydroxypropyl sulfonate aq. sol n. Uses Surfactant stabilizer for emulsion polymerization latex stabilizer reduces latex foaming provides improved film props, for paints, adhesives, paper and textile coatings... 

Uses Emulsifier, thickener, wetting agent, dispersant, solubilizer, stabilizer for cosmetics and pharmaceuticals demulsifier in petrol, industry detergent ingred. antistat for polyethylene and resin molding powds. metal treatment emulsion polymerization surfactant in latex-based paints, aq.-based syn. cutting fluids and vulcanization of rubber Properties Colorless liq. m.w. 5500 ref. index 1.4613 water-sol. sp.gr. 1.04 vise. 850 cps HLB 15 cloud pt. 65 C (1%) pour pt. 18 C surf, tens. 40.3 dynes/cm (0.1%) nonionic 100% act. 

U n itex http //www. unitexchemical. com] Dicyclohexyl sodium sulfosuccinate CAS 23386-52-9 EINECS/ELINCS 245-629-3 Synonyms Sodium 1,4-dicyclohexyl sulfobutanedioic acid Sodium 1,4-dicyclohexyl sulfonatosuccinate Sodium dicyclohexyl sulfosuccinate Sodium 1,4-dicyclohexyl sulfosuccinate Succinic acid, sulfo-, 1,4-dicyclohexyl ester, sodium salt Definition Sodium salt of the diester of cyclohexyl alcohol and sulfosuccinic acid Empiricai C16H26O7S Na Properties Anionic Toxicoiogy TSCA listed Uses Dispersant, surfactant, emulsifier for modified S/B post additive to stabilize latex and promote adhesion pigment dispersant surfactant, foaming agent, hydrotrope in cosmetics emulsifier in food pkg. 

Figure 6.4. A mixed monolayer of nonionic and anionic surfactants usually stabilizes latex droplets...

Figures 6.7(a) and (b) show the topographies of films cast from maleate-stabilized latex, before and after rinsing, respectively. The film before rinsing showed hills , indicative of surfactant aggregates at the surface. After the film was rinsed with water, holes appeared in a regular pattern. This is indicative of removal of surfactant from the surface. The situation is much improved compared to the appearance of the films from the SDS-based latex but, evidently, even with the reactive maleate surfactant, a substantial portion is not anchored to the latex particle. Chemical analysis showed that about 1/3 of the surfactant was not chemically incorporated into the film.

The most common method of stabilizing latex particles is by addition of mixed anionic and nonionic surfactants. The key property of a siufactant is that it possesses chemically dissimilar groups one hydrophobic and one hydrophilic. The hydrophobic group is physically adsorbed onto the polymer latex particle while the hydrophilic portion extends into the aqueous phase. It is the hydrophilic groups that provide the stabilization. 

Latex coating. The first objective was to cover the latex with the polycations without coagulation. Cationic surfactants as well as polycations are normally used as titrants for the determination of the charge density of anionically stabilized latexes (4). In an impropriate range of concentration, the point of charge compensation is indicated by clearly pronounced flocculation. 

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