Protective surfactants

There is no consensus on how polymer affects the IFT between alkaline solution and crade oil. It is commonly believed that the effect is not significant. Some believe that polymer can protect surfactant from being associated with... 

Relatively small amounts of the 2-nitrobenzyl-protected surfactant (1-7 percent of the total solids in the coating) are needed to effect the required change in adhesion of the polymeric coating for the metal surface on photolysis. A specific example best illustrates the phenomenon. 

In the final stage of emulsion-droplet coalescence the two droplets have made contact, the protecting surfactant films have fused, and the droplets are connected by a narrow neck. In this situation the neck can either grow spontaneously at all sizes or there is a critical neck size that has to be exceeded before growth occurs spontaneously. The driving force for the coalescence process is a decrease in surface area with a concomitant gain in surface free energy. One could then expect that the process is slower the smaller the surface tension. As the analysis presented below demonstrates, this intuitive expectation is erroneous (42). 

Uses Protectant, surfactant for building appiics. such as conaete, interlocking paving blocks, terra cotta pavement, and sandstone terra cotta pavement water repellent treatment for paper and paperboard, leather Properties Amber dear liq. sp.gr. 0.97 f.p. < -18 C flash pt. (CC) 26 C 25% act. 

Uses Protectant, surfactant for textile applies, (syn., cellulosic, microfibers, and blended fibers)... 

Uses Protectant, surfactant for water repellent treatment for paper and paperboard used for food pkg. (fast food, pkg. for butter/margarine/meat/poultry/coffee/lrozen prods.) and petfood pkg. 

Alveolar lining fluid (98,150-152) and airway mucus (153-155) also contain potent antioxidants, including catalase, superoxide dismutase, peroxidases, and glutathione. These enzymes are physically associated with airway and alveolar surfactant and may serve to protect surfactant from oxidative injury. 

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). 

Although most greases offer some inherent protection against msting, additives, eg, amine salts, sodium sulfonate, cycloparaffin (naphthenate) salts, esters, and nonionic surfactants (qv), are often used to provide added protection against water and salt-spray corrosion. A dispersion of sodium nitrite has been particularly effective in some multipurpose greases. 

Nonfood Uses. Vegetable oils are utilized in a variety of nonedible applications, but only a few percent of the U.S. soybean oil production is used for such products (see Table 13). Soybean oil is converted into alkyd resins (qv) for protective coatings, plasticizers, dimer acids, surfactants (qv), printing inks, SoyDiesel fuel (methyl esters used to replace petroleum-based diesel fuel) and other products (76). 

Bunte salts have bacterial, insecticidal, and fungicidal properties, and are also used as chelating agents (qv) or surfactants (qv) (97,98). Bunte salts have been tested for preirradiation protection for mammals exposed to lethal radiation doses (99,100) (see Radioprotectiveagents). 

Many different combinations of surfactant and protective coUoid are used in emulsion polymerizations of vinyl acetate as stabilizers. The properties of the emulsion and the polymeric film depend to a large extent on the identity and quantity of the stabilizers. The choice of stabilizer affects the mean and distribution of particle size which affects the rheology and film formation. The stabilizer system also impacts the stabiUty of the emulsion to mechanical shear, temperature change, and compounding. Characteristics of the coalesced resin affected by the stabilizer include tack, smoothness, opacity, water resistance, and film strength (41,42). 

Poly(vinyl acetate) emulsions can be made with a surfactant alone or with a protective coUoid alone, but the usual practice is to use a combination of the two. Normally, up to 3 wt % stabilizers may be included in the recipe, but when water sensitivity or tack of the wet film is desired, as in some adhesives, more may be included. The most commonly used surfactants are the anionic sulfates and sulfonates, but cationic emulsifiers and nonionics are also suitable. Indeed, some emulsion compounding formulas require the use of cationic or nonionic surfactants for stable formulations. The most commonly used protective coUoids are poly(vinyl alcohol) and hydroxyethyl cellulose, but there are many others, natural and synthetic, which are usable if not preferable for a given appHcation. 

Emulsion polymerizations of vinyl acetate in the presence of ethylene oxide- or propylene oxide-based surfactants and protective coUoids also are characterized by the formation of graft copolymers of vinyl acetate on these materials. This was also observed in mixed systems of hydroxyethyl cellulose and nonylphenol ethoxylates. The oxyethylene chain groups supply the specific site of transfer (111). The concentration of insoluble (grafted) polymer decreases with increase in surfactant ratio, and (max) is observed at an ethoxylation degree of 8 (112). 

Although spray-dryiag accommodates relatively high content of surfactants, certain types, such as the alkanolamides and some nonionic surfactants are best added to the product after spray-dryiag. Post additioa aot only protects the surfactant from the heat of the tower but also prevents the formation of aerosols ia the exit gas. Aerosols are more difficult to trap ia the scmbbiag system than soHd fines. They are formed by unsulfonated matter from the manufacture of LAS and nonionic surfactants with short ethylene oxide chains (120). 

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