Surfactants s. Surface-active

For a certain W/0 system at constant temperature and constant surfactant concentration, y /g is reduced when the surfactant s surface activity is increased. Comparing the interfacial tensions in Table 2 ([asphaltene] = 1%) and in Table 3 ([resin] = 1%), it is clear that resins are more inter-facially active than are asphaltenes. 

Y. Sela, S. Magdassi, and N. Garti Newly Designed Polysiloxane-Graft-Poly (Oxyethylene) Copolymeric Surfactants Preparation, Surface Activity and Emulsification Properties. Colloid Polym. Sci. 272, 684 (1994). 

Sela Y, Magdassi S, Garti N. Newly design polysiloxane-graft-poly-(oxyethylene) copolymeric surfactants preparation, surface activity and emulsification properties. Colloid Polym Sci 1994 272 684-691. 

Leaching/washing/flushing of soil with water or surfactant (a surface-active substance) this is not very commonly practiced, and use is limited due to a need for large quantities of water. The results are also highly dependent upon the soil s physical parameters. 

HEC has found limited use as a thickener for cosmetic formulations. Modification of this polymer with small amounts of tetramethylamine functionality expanded its end use by providing substantivity to hair and inhibiting surfactant penetration of human skin (37). Hydrophobic modification of quaternary HEC increases the polymer s surface activity (38) as reflected in its foam stability (Figure 7). 

Various expressions for HOR were proposed, expressed via the surfactant distribution coefficient between the phases, and the surfactant s adsorption activity (5). The advantage of HOR as compared to the HLB system is that, for a particular choice of the standard state, this index does not depend on the surfactant concentration, the type of the organic phase, or the presence of various additives soluble in water and oil. Methods were also proposed to determine the HOR for mixtures of surfactants (262). For these systems, however, this index is not additive anymore. The HOR values for mixtures are shifted towards that characteristic for the component which possesses the higher value of the distribution coefficient. Another deficiency of the HOR concept is its suggestiveness it was mentioned above that this value depends on the coordinate of the HLC. However, for the HOR values other than unity, the HLC position-dependent work of the introduction of a surfactant molecule into the surface layer is uniquely determined by the HOR. 

A-B, A-B-A block and BAn graft type polymeric surfactants are used to stabilise emulsions and suspensions [18]. B is the anchor chain that adsorbs very strongly at the 0/W or S/L interface, whereas the A chains are the stabilising chains that provide steric stabilisation. These polymeric surfactants exhibit surface activity at the 0/W or S/L interface. The adsorption and conformation of these polymeric surfactant at the interface has been described in detail in reference 18. 

Masayama, A. Endo, C. Takeda, S. Nojima, M. Ono, D. Takeda, T. Ozone-cleavable gemini surfactants. Their surface-active properties, ozonolysis, and biodegradability. Langmuir 2000, 16, 368-373. 

Albertsson (Paiiition of Cell Paiiicle.s and Macromolecules, 3d ed., Wiley, New York, 1986) has extensively used particle distribution to fractionate mixtures of biological products. In order to demonstrate the versatility of particle distribution, he has cited the example shown in Table 22-14. The feed mixture consisted of polystyrene particles, red blood cells, starch, and cellulose. Liquid-liquid particle distribution has also been studied by using mineral-matter particles (average diameter = 5.5 Im) extracted from a coal liquid as the solid in a xylene-water system [Prudich and Heniy, Am. Inst. Chem. Eng. J., 24(5), 788 (1978)]. By using surface-active agents in order to enhance the water wettability of the solid particles, recoveries of better than 95 percent of the particles to the water phase were obsei ved. All particles remained in the xylene when no surfactant was added. 

The inhibition of Streptococcus mutans adherence to hydroxyapatite with combinations of alkyl phosphates and nonionic surfactants was tested. Seven alkyl phosphate derivatives and three nonionic surfactants were examined for their ability to inhibit the adherence of 3H-labeled cells of S. mutans to hydroxyapatite treated with buffer or parotid saliva. No compound by itself effectively hindered binding of bacteria to hydroxyapatite. A combination of certain of the alkyl phosphates, notably a disodium phosphate of 1-octadecanol, and nonionic surfactant at a 1 1 molar ratio gave a strong inhibition of S. mutans adherence. Treatment with this combination resulted in 98% reduction of adherence. Adsorption of the two types of surface-active agents alone and in combinations was studied using 14C-labeled agents. Electrophoretic measure-... 

There are two different classes of surface-active materials in seawater, those that are naturally present and those that have been added to the oceans by man s activities. Most of the analytical methods proposed for use in seawater actually measure the anthropogenic input, and attempt as much as possible to eliminate interferences from naturally occurring compounds. Yet sea foam was known to exist long before detergents. It is to be expected that both kinds of surfactants would be concentrated at the air-sea interface. 

Surface acoustic waves (SAWs), acoustic wave sensors and, 22 270 Surface-active agent(s), 12 33. See also Surfactant entries cmc values of, 24 121t general classification of, 24 144-153 nonionic, 10 665 organic esters as, 10 519 Surface-active molecules, 12 1 foaming and, 12 3... 

Anokhina, M.S., Il in, M.M., Semenova, M.G., Belyakova, L.E., Polikarpov, Yu.N. (2005). Calorimetric investigation of the thermodynamic basics of the effect of malto-dextrins on the surface activity of legumin in the presence of small-molecule surfactants. Food Hydrocolloids, 19, 455 166. 

In addition to temperature (which decreases y), the properties of interfaces are governed by the chemistry of the molecules present, their concentration and their orientation with respect to the interface. Solutes adsorbed at an interface which reduce interfacial tension are known as surface active agents or surfactants. Surfactants reduce interfacial tension by an amount given, under ideal conditions, by the Gibb s equation ... 

The essential ingredients of all these hair and skin products are part of a broad class of compounds called surfactants, which is short for "surface active agents "All surfactant molecules are polar on one end and nonpolar on the other. Because of their nonpolar ends, they resist dissolving in water and instead cling to water s surface where their nonpolar ends stick up out of the water. Pour some oil onto the surfactant containing water and the nonpolar tails will cling to the oil s surface. In this way, surfactants bind together the surfaces of water and a nonpolar material. 

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