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Nonionic surfactants defined

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). [Pg.25]

Poloxamers are used primarily in aqueous solution and may be quantified in the aqueous phase by the use of compleximetric methods. However, a major limitation is that these techniques are essentially only capable of quantifying alkylene oxide groups and are by no means selective for poloxamers. The basis of these methods is the formation of a complex between a metal ion and the oxygen atoms that form the ether linkages. Reaction of this complex with an anion leads to the formation of a salt that, after precipitation or extraction, may be used for quantitation. A method reported to be rapid, simple, and consistently reproducible [18] involves a two-phase titration, which eliminates interferences from anionic surfactants. The poloxamer is complexed with potassium ions in an alkaline aqueous solution and extracted into dichloromethane as an ion pair with the titrant, tet-rakis (4-fluorophenyl) borate. The end point is defined by a color change resulting from the complexation of the indicator, Victoria Blue B, with excess titrant. The Wickbold [19] method, widely used to determine nonionic surfactants, has been applied to poloxamer type surfactants 120]. Essentially the method involves the formation in the presence of barium ions of a complex be-... [Pg.768]

Particularly useful is the physical classification of surfactants based on the hydrophile-lipophile balance (HLB) system [67,68] established by Griffin [69,70]. More than 50 years ago he introduced an empirical scale of HLB values for a variety of nonionic surfactants. Griffin s original concept defined HLB as the percentage (by weight) of the hydrophile divided by 5 to yield more manageable values ... [Pg.257]

In order to define a ionic/nonionic surfactant solution with high salinity/hardness tolerance, the following criterion should be followed. The mixed micelle should have as large of a negative deviation from ideality as possible. Surfactant mixture characteristics which result in this have already been discussed. The nonionic surfactant should have a high cloud point. Otherwise the amount of nonionic surfactant which can be added to the system is limited to low levels before phase separation occurs. If possible, a mixed ionic surfactant should be used for reasons Just discussed. There is no such benefit to using mixed nonionic surfactants, although this is not necessarily detrimental either. [Pg.22]

The majority of the recipes described in the literature are based on the anionic sodium dodecylsulfate (SDS) as a model system. The possibility of using cationic surfactants such as octadecyl pyridinium bromide for the preparation of miniemulsions was first exploited in 1976. However, the emulsions were prepared by stirring and the resulting emulsions showed broadly distributed droplet sizes [2,39,50]. Recent work on steady-state miniemulsions showed that cationic and nonionic surfactants form well-defined miniemulsions for further miniemulsion polymerization processes, resulting in narrow size distributed stable cationic and nonionic latex particles [51]. Similar molecular amounts of the simple cationic surfactant, cetyltrimethylammonium bromide or chloride... [Pg.88]

Nonionic miniemulsions can be made by using 3-5% of a polyfethylene oxide) derivative as surfactant, resulting in larger, but also very well defined latexes [51]. Chern and Liou used a nonionic surfactant nonylphenol poly-ethoxylate with an average of 40 ethylene oxide units per molecule [53]. Particle sizes between 135 and 280 nm were realized. The particle size mainly depends on the type and amount of the hydrophobe and therefore on the degree of the suppression of Ostwald ripening [53]. [Pg.89]

Effect of the synthesis time. Hanoka et al. studied the influence of synthesis time, defined as the time from the hydrazine injection to the TEOS addition . In nonionic surfactant/organic solvents and anionic surfactant/or-ganic solvents, the particle size was independent of the synthesis time furthermore, the particle size range in such systems was very narrow. In cationic surfactant/organic solvent the rhodium particle size increased with the synthesis time. [Pg.281]

The potential importance of the temperature effect on surfactant properties has been recognized for some time and led to the concept of using the PIT as a quantitative tool for the evaluation of surfactants in emulsion systems. As a general procedure, emulsions of oil, aqueous phase, and approximately 5% surfactant were prepared by shaking at various temperatures. The temperature at which the emulsion was found to be inverted from o/w to w/o (or vice versa) was then defined as the PIT of the system. Since the effect of temperature on the solubility of nonionic surfactants is reasonably well understood, the physical principles underlying the PIT phenomenon follow directly. [Pg.283]


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