First effective surfactants

In a detersive system containing a dilute surfactant solution and a substrate bearing a soHd polar sod, the first effect is adsorption of surfactant at the sod—bath interface. This adsorption is equivalent to the formation of a thin layer of relatively concentrated surfactant solution at the interface, which is continuously renewable and can penetrate the sod phase. Osmotic flow of water and the extmsion of myelin forms foHows the penetration, with ultimate formation of an equdibrium phase. This equdibrium phase may be microemulsion rather than Hquid crystalline, but in any event it is fluid and flushable... 

Surfactant First-effect concentration (mg/l) Test species Test duration EffecC... 

Temperature Stability The long-term thermal stability of injected surfactants in the reservoir environment is a must for an effective surfactant formulation. The thermal stability of several ionic and nonionic surfactants has been reported in terms of the time required for half of the surfactant to decompose (e.g. half-life).Most of the surfactants investigated decomposed by first-order kinetics. The interfacial activity of surfactant solutions after six months at 80°C was reported by Akstinat. The results showed that the stability of the surfactants was in the order ether sulfonates > ether carboximethylates > ether sulfates > ether phosphates. 

The presence of micelles or microemulsions will have significant effects on the biological efficacy of an insoluble pesticide. In the first instance, surfactants will affect the rate of solution of the chemical. Below the c.m.c., surfactant adsorption can aid wetting of the particles and, consequently, increases the rate of dissolution of the particles or agglomerates [8]. Above the c.m.c., the rate of dissolution is affected as a result of solubilization. According to the Noyes-Whitney relation [122], the rate of dissolution is directly related to the surface area of the particles A and the saturation solubility, Cg, i.e. 

Fluorinated surfactants can lower the interfacial tension between a fluorocarbon, such as per perfluorodecalin, and water to as low as 1 mN/m. This suggests that fluorinated surfactants should be effective emulsifiers for biomedical fluorochemicals [42]. The first fluorinated surfactants [112-121] used in fluorochemical emulsions included potassium oleate, a perfluorinated amine oxide [115,116], a nonionic fluorinated surfactant derived from perfluoroalcohol [117], a fluorinated surfactant with two perfluoroalkyl end groups [118], and perfluo-roalkylated polyols [119]. However, the toxicity of these fluorinated surfactants has hindered their intravascular use. 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

Thermal stabihty of the foaming agent in the presence of high temperature steam is essential. Alkylaromatic sulfonates possess superior chemical stabihty at elevated temperatures (205,206). However, alpha-olefin sulfonates have sufficient chemical stabihty to justify their use at steam temperatures characteristic of most U.S. steamflood operations. Decomposition is a desulfonation process which is first order in both surfactant and acid concentrations (206). Because acid is generated in the decomposition, the process is autocatalytic. However, reservoir rock has a substantial buffering effect. 

The first group is the Sherwood number, the second is the Reynolds number, and the third the Schmidt number. If surfactants are present, their effect on p should also be included [cf. Eq. (66) or (68)]. 

An evaluation of the retardation effects of surfactants on the steady velocity of a single drop (or bubble) under the influence of gravity has been made by Levich (L3) and extended recently by Newman (Nl). A further generalization to the domain of flow around an ensemble of many drops or bubbles in the presence of surfactants has been completed most recently by Waslo and Gal-Or (Wl). The terminal velocity of the ensemble is expressed in terms of the dispersed-phase holdup fraction and reduces to Levich s solution for a single particle when approaches zero. The basic theoretical principles governing these retardation effects will be demonstrated here for the case of a single drop or bubble. Thermodynamically, this is a case where coupling effects between the diffusion of surfactants (first-order tensorial transfer) and viscous flow (second-order tensorial transfer) takes place. Subject to the Curie principle, it demonstrates that this retardation effect occurs on a nonisotropic interface. Therefore, it is necessary to express the concentration of surfactants T, as it varies from point to point on the interface, in terms of the coordinates of the interface, i.e.,... 

Figure 20 shows the plot of the surface tension vs. the logarithm of the concentration (or-lg c-isotherms) of sodium alkanesulfonates C,0-C15 at 45°C. In accordance with the general behavior of surfactants, the interfacial activity increases with growing chain length. The critical micelle concentration (cM) is shifted to lower concentration values. The typical surface tension at cM is between 38 and 33 mN/m. The ammonium alkanesulfonates show similar behavior, though their solubility is much better. The impact of the counterions is twofold First, a more polarizable counterion lowers the cM value (Fig. 21), while the aggregation number of the micelles rises. Second, polarizable and hydrophobic counterions, such as n-propyl- or isopropylammonium and n-butylammonium ions, enhance the interfacial activity as well (Fig. 22). Hydrophilic counterions such as 2-hydroxyethylammonium have the opposite effect. Table 14 summarizes some data for the dodecane 1-sulfonates.

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