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Interfacial tension detergency

Thus, adding surfactants to minimize the oil-water and solid-water interfacial tensions causes removal to become spontaneous. On the other hand, a mere decrease in the surface tension of the water-air interface, as evidenced, say, by foam formation, is not a direct indication that the surfactant will function well as a detergent. The decrease in yow or ysw implies, through the Gibb s equation (see Section III-5) adsorption of detergent. [Pg.485]

Detergents may be produced by the chemical reaction of fats and fatty acids with polar materials such as sulfuric or phosphoric acid or ethylene oxide. Detergents emulsify oil and grease because of their abiUty to reduce the surface tension and contact angle of water as well as the interfacial tension between water and oil. Recent trends in detergents have been to lower phosphate content to prevent eutrification of lakes when detergents are disposed of in municipal waste. [Pg.135]

Furthermore, in a series of polyoxyethylene nonylphenol nonionic surfactants, the value of varied linearly with the HLB number of the surfactant. The value of K2 varied linearly with the log of the interfacial tension measured at the surfactant concentration that gives 90% soil removal. Carrying the correlations still further, it was found that from the detergency equation of a single surfactant with three different polar sods, was a function of the sod s dipole moment and a function of the sod s surface tension (81). [Pg.535]

Even if the interfacial tension is measured accurately, there may be doubt about its applicability to the surface of bubbles being rapidly formed in a solution of a surface-active agent, for the bubble surface may not have time to become equihbrated with the solution. Coppock and Meiklejohn [Trans. Instn. Chem. Engrs., 29, 75 (1951)] reported that bubbles formed in the single-bubble regime at an orifice in a solution of a commercial detergent had a diameter larger than that calculated in terms of the measured surface tension of the solution [Eq. (14-206)]. The disparity is probably a reflection of unequihbrated bubble laminae. [Pg.1418]

One concerned with the measurement of gas-hquid interfacial tension should consult the useful reviews of methods prepared by Harkius [in Chap. 9 of Weissberger, Techniques of Organic Chemstry, 2d ed., vol. I, part 2, Interscience, New York, 1949), Schwartz and coauthors [Suiface Active Agents, vol. I, Interscience, New York, 1949, pp. 263-271 Suiface Active Agents and Detergents, vol. 2, Interscience, New York, 1958, pp. 389—391, 417—418], and by Adamson [Physical Chemistry of Suifaces, Interscience, New York, I960]. [Pg.1418]

Detergency may be defined as the removal of dirt from solid surfaces by surface chemical means [29], and may be related to several surfactant properties, including wetting and rewelting ability, foam generation, and surface and interfacial tension. It has long been observed... [Pg.770]

Detergency, or the power of a detergent product to remove soil, depends on the ability of surfactants to lower the interfacial tension between different phases. This can be explained for a typical case where removal of liquid soil is aided by surfactant adsorption onto the soil and substrate surfaces from the cleaning bath (Figure 2) using Young s equation,... [Pg.243]

The Gibbs equation relates the extent of adsorption at an interface (reversible equilibrium) to the change in interfacial tension qualitatively, Eq. (4.3) predicts that a substance which reduces the surface (interfacial) tension [(Sy/8 In aj) < 0] will be adsorbed at the surface (interface). Electrolytes have the tendency to increase (slightly) y, but most organic molecules, especially surface active substances (long chain fatty acids, detergents, surfactants) decrease the surface tension (Fig. 4.1). Amphi-pathic molecules (which contain hydrophobic and hydrophilic groups) become oriented at the interface. [Pg.89]

Wettability Dependence of Detergency. The dependence of Dr on i]/ was described above. The purpose of this section will be to develop an expression for in terms of experimentally accessible interfacial tension quantities. To begin with, the TPL has a geometry as shown in Figure 7. For this system, the Young-Dupre"" equation (14-16) can be written as... [Pg.248]

Girifalco-Good Plot of Wettability Data From Detergency and Interfacial Tension Data. [Pg.252]

Wetting Parameters in the Detergency Equation. The detergency system has three interfaces which have three interfacial tensions at equilibrium with all three phases Ksw> Yfs and Yfw When only two phases are in equilibrium, three other surface tensions are possible Ysw> Yfs> Yfw (however, when the fiber is an insoluble solid, Ysw Y w> Ysw will be... [Pg.253]

The film pressure values for the detergency system are also listed in Table 2. These quantities represent the difference in interfacial tension between two pure phases and the interfacial tension of the same two phases which are at saturation equilibrium with the third phase. Since the PEG fiber surface was assumed insoluble in either the bath or soil, = 0. [Pg.258]

All molecules that, when dissolved in water, reduce surface tension are called surface-active substances (e.g., soaps, surfactants, detergents). This means that such substances adsorb at the surface and reduce surface tension. The same will happen if a surface-active substance is added to a system of oil-water. The interfacial tension of the oil-water interface will be reduced accordingly. Inorganic salts, on the other hand, increase the surface tension of water. [Pg.43]

The surface tension of the system can also be changed by grinding with liquid, thus decreasing interfacial tension. This gives rise to a variety of parameters since, by adding suitable chemicals (electrolytes or surface-active agents), one can modify the end-product properties. Conversely, the size of crystals formed from a supersaturated solution of a substance is related to the surface tension (at the solid-liquid interface). Thus, to obtain fine crystals, a suitable detergent is added, and thus, finer crystals are obtained. [Pg.155]

Bioaccumulation All classes of surfactant are active surface tension depressants. At the critical micelle concentration (CMC) abrupt changes occur in the characteristic properties of surfactants such that surface and interfacial tensions in an aqueous system are at their minimum while osmotic pressure and surface detergent properties are significantly increased. The CMC for most surfactants is reached around 0.01% (18, 19). These effects have an impact on the potential for bioaccumulation of the pesticide, and in the organisms monitored the presence of Dowanol and nonylphenol increased the accumulation of fenitrothion and aminocarb at least 20-300% respectively, over the accumulation obtained in their absence (20). In effect, these adjuvants... [Pg.354]

Surfactants fulfil many functions, such as detergency, micelle stabilization, interfacial tension reduction, wetting, and so on. In hydrocarbons, however, surfactants are not capable of lowering the surface tension, because these solvents... [Pg.67]

The characteristic effect of surfactants is their ability to adsorb onto surfaces and to modify the surface properties. Both at gas/liquid and at liquid/liquid interfaces, this leads to a reduction of the surface tension and the interfacial tension, respectively. Generally, nonionic surfactants have a lower surface tension than ionic surfactants for the same alkyl chain length and concentration. The reason for this is the repulsive interaction of ionic surfactants within the charged adsorption layer which leads to a lower surface coverage than for the non-ionic surfactants. In detergent formulations, this repulsive interaction can be reduced by the presence of electrolytes which compress the electrical double layer and therefore increase the adsorption density of the anionic surfactants. Beyond a certain concentration, termed the critical micelle concentration (cmc), the formation of thermodynamically stable micellar aggregates can be observed in the bulk phase. These micelles are thermodynamically stable and in equilibrium with the monomers in the solution. They are characteristic of the ability of surfactants to solubilise hydrophobic substances. [Pg.54]

Figure 3.12 Two liquids A (detergent) and B (oily soil) on a solid surface (a) separated and (b) in contact, yA and yB = wetting tensions, yAB = interfacial tension, R = interfacial wetting tension [3]. Figure 3.12 Two liquids A (detergent) and B (oily soil) on a solid surface (a) separated and (b) in contact, yA and yB = wetting tensions, yAB = interfacial tension, R = interfacial wetting tension [3].
It also demonstrates that in both cases a similar reflectance vs temperature curve exists. In the region of the liquid crystal dispersion, i.e. between 20°C and 40°C, the oil removal increases significantly. Above the phase transition W + La — W + L3, between 40°C and 70°C, no further increase in oil removal takes place. For olive oil, a small decrease in detergent performance is observed. The interfacial tensions between aqueous solutions of C12E3 and mineral oil lie at about 5 mN m 1 at 30°C and 50°C and these relatively high values indicate that, in this system, the interfacial activity is not the decisive factor in oil removal from fabrics. [Pg.66]

Figure 3.22 (right) represents the three-phase temperature intervals for Q2E4 and Q2E5 vs the number n of carbon atoms of n-alkanes (for the phase behaviour of ternary systems see Section 3.4.2, Figure 3.26). The left part of Figure 3.22 shows the detergency of these surfactants for hexadecane. Both parts of Figure 3.22 indicate that the maximum oil removal is in the three-phase interval of the oil used (n-hexadecane) [22]. This means that not only the solubilisation capacity of the concentrated surfactant phase, but probably also the minimum interfacial tension existing in the range of the three-phase body is responsible for the maximum oil removal. Further details about the influence of the polarity of the oil, the type of surfactant and the addition of salt are summarised in the review of Miller and Raney [23]. Figure 3.22 (right) represents the three-phase temperature intervals for Q2E4 and Q2E5 vs the number n of carbon atoms of n-alkanes (for the phase behaviour of ternary systems see Section 3.4.2, Figure 3.26). The left part of Figure 3.22 shows the detergency of these surfactants for hexadecane. Both parts of Figure 3.22 indicate that the maximum oil removal is in the three-phase interval of the oil used (n-hexadecane) [22]. This means that not only the solubilisation capacity of the concentrated surfactant phase, but probably also the minimum interfacial tension existing in the range of the three-phase body is responsible for the maximum oil removal. Further details about the influence of the polarity of the oil, the type of surfactant and the addition of salt are summarised in the review of Miller and Raney [23].
This behaviour has a particular importance for the soil removal process in detergency. During the oil removal from stained fabrics or hard surfaces, ternary systems occur where three phases coexist in equilibrium. As already pointed out above, in this region the interfacial tension is particularly low. Because the interfacial tension is generally the restraining force,... [Pg.72]


See other pages where Interfacial tension detergency is mentioned: [Pg.210]    [Pg.3]    [Pg.465]    [Pg.486]    [Pg.489]    [Pg.53]    [Pg.276]    [Pg.535]    [Pg.261]    [Pg.97]    [Pg.99]    [Pg.262]    [Pg.89]    [Pg.263]    [Pg.132]    [Pg.37]    [Pg.128]    [Pg.129]    [Pg.255]    [Pg.48]    [Pg.144]    [Pg.66]    [Pg.252]    [Pg.95]    [Pg.227]    [Pg.395]    [Pg.46]   
See also in sourсe #XX -- [ Pg.67 , Pg.68 ]




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