Surfactant composite

TABLE 26 Changes in the Surfactant Composition of German (European) Manual Dishwashing Detergents... 

By simple evaporation of the volatile components of nanoparticle-containing w/o microemulsions, it is possible to obtain very interesting nanoparticle/surfactant composites [214],... 

Tolbert, SH Firouzi, A Stucky, GD Chmelka, BF, Magnetic Field Alignment of Ordered Silicate-Surfactant Composites and Mesoporous Sihca, Science 278, 264, 1997. 

Below some critical surfactant concentration, the system is two-phase with excess oil or water depending on the oil/water concentration. On adding more surfactant, the system moves into a one-phase region with normal micelles forming in water-rich systems. The water constitutes the continuous phase, solvating the headgroups of the surfactant whose hydro-phobic tails solubilise oil in the core of the micelle. In oil rich systems, reverse-micelles form. With further increases in surfactant composition. 

Differential pressure sticking occurs when the drill pipe becomes imbedded in the mud wall cake opposite a permeable zone. The difference between the hydrostatic pressure in the drill pipe and the formation pressure holds the pipe in place, resulting in a sticking pipe. Differential sticking may be prevented, and a stuck drill bit may be freed, using an oil-mud or an oil- or water-based surfactant composition. 

FB Rosevear. Liquid crystals The mesomorphic phases of surfactant compositions. J Soc Cosmet Chem 19 581, 1968. 

TRADE NAME SUPPLIER CHEMICAL FORMULA OF MAJOR SYNTHESISED PRODUCT % SURFACTANT ACTIVITY NATURE OF SURFACTANT COMPOSITION INORGANIC SALT CONTENT/ WATER CONTENT/ ... 

Although silicone oils by themselves or hydrophobic particles (e.g., specially treated silica) are effective antifoams, combinations of silicone oils with hydrophobic silica particles are most effective and commonly used. The mechanism of film destruction has been studied with the use of surface and interfacial tensions, measurements, contact angles, oil-spreading rates, and globule-entering characteristics for PDMS-based antifoams in a variety of surfactant solutions.490 A very recent study of the effect of surfactant composition and structure on foam-control performance has been reported.380 The science and technology of silicone antifoams have recently been reviewed.491... 

Surfactants are used in a variety of applications, frequently in the form of dilute aqueous solutions. However, it is not cost effective to transport, store, and display in retail outlets surfactant products such as household detergents in this form. Accordingly, it is important to have products that dissolve quickly and to understand what aspects of surfactant composition and structure promote rapid dissolution. The dissolution process is more complex for surfactants than for most other materials because it typically involves formation of one or more concentrated and highly viscous liquid crystalline phases, which are not present initially and which could potentially hinder dissolution. In this article the rates and mechanisms of surfactant dissolution are reviewed and discussed. 

The mixture CMC is plotted as a function of monomer composition in Figure 1 for an ideal system. Equation 1 can be seen to provide an excellent description of the mixture CMC (equal to Cm for this case). Ideal solution theory as described here has been widely used for ideal surfactant systems (4.6—18). Equation 2 can be used to predict the micellar surfactant composition at any monomer surfactant composition, as illustrated in Figure 2. This relation has been experimentally confirmed (ISIS) As seen in Figure 2, for an ideal system, if the ratio XA/yA < 1 at any composition, it will be so over the entire composition range. In classical phase equilibrium thermodynamic terms, the distribution coefficient between the micellar and monomer phases is independent of composition. 

The equilibrium in these systems above the cloud point then involves monomer-micelle equilibrium in the dilute phase and monomer in the dilute phase in equilibrium with the coacervate phase. Prediction o-f the distribution of surfactant component between phases involves modeling of both of these equilibrium processes (98). It should be kept in mind that the region under discussion here involves only a small fraction of the total phase space in the nonionic surfactant—water system (105). Other compositions may involve more than two equilibrium phases, liquid crystals, or other structures. As the temperature or surfactant composition or concentration is varied, these regions may be encroached upon, something that the surfactant technologist must be wary of when working with nonionic surfactant systems. 

The variation of the mixture critical micelle concentration (CMCf ) with temperature and with overall surfactant composition has been studied using ultrafiltration for two binary mixed nonionic/anionic systems. 

Sample Calculations. For the PSM model, computer-calculations have been done (17). All concentrations are normalized with respect to c - In Figure 3 we show mixed cmc s versus overall surfactant composition calculated for mixed surfactants with c /cj = 3.0, A = 0.0, B = 0.0, cjc — 0.0, and varying values of y j, P- For a given value of a, the calculated cmc for the nonionic/ionic system (y j = 0.6, P = a) is... 

C FNa-CioSNa and C-7FNa-Cla5Na systems. These are the mixed anionic-anionic surfactants systems. The surface tension (interfacial tension) - concentration relationships are shomn in Fig, 1 to 3. There are surfactant compositions at which uniform or homogeneous mixed micelle do not exist in these two systems due to the "mutual pho-bicity" between FC- and HC-chains of the surfactants (4,7) Therefore the molecular interaction parameterof the two surfactants in micelles can not be calculated from the Surface tension curves because this cmc has no longer the physical meaning of mixture cmc. However, we can obtain the /3(t values from the surface tension curves by means of equation 13, Table 1 and 2 show the results. 

Since the latex is slightly polydisperse the specific surface area of the latex cannot be calculated with sufficient accuracy. We will therefore present the adsorption results per unit mass of the latex. Note, that we are in this work only concerned with the surfactant composition on the surface and not the absolute value of the amount of adsorbed surfactant per unit area. 

As for the close packed surface layer it is assumed that the micelles do not contain any water, i.e. x + x = 1. Assuming ideal mixing of the two surfactant types in the mixed micelle, i.e. f. = f2 = 1, Equation 23 shows that the cmc is the arithmetic mean or the two single surfactant erne s with the surfactant composition in the micelle as the variable. 

Equation 28 differs formally from Equation 17 only in that the term involving the interaction with the surface is missing in Equation 28. Thus, there are two factors determining the distribution of the surfactants between the solution and the micelles. The first involves the cmc s of the two single surfactants and the second factor involves the interaction between the two surfactants in the micelle. In the ideal case, i.e. where x. 2 the surfactant composition in the micelle is related to the solution composition, at the onset of micelle formation, through... 

Critical Micelle Concentration. Figure 1 shows the cmc as a function of the surfactant composition, a, defined as. 

Assuming ideal mixing, the surfactant composition in the micelles can be calculated from Equation 29, or alternatively from the experi-... 

The results are presented in Figure 2 where the surfactant composition in the micelles is plotted as a function of the total surfactant composition at the critical micelle concentration of the mixture. The figure reveals a strong enrichment of NP-EOin the micelles. 

In order to check how the introduction of the surfactant-surfactant interaction affects the calculated cmc and the surfactant composition in the micelles, we used Equations 25 and 26 to obtain an average value of x 2 which was found to be -1.6. The dashed lines in Figures 1 and 2 show that introducing a non-zero value of x 2 not affect the calculated cmc or the surfactant composition in the micelles very much. This is because the dominating term in Equation 28 involves the difference in the cmc of the two surfactants. Thus, to obtain an assessment of the importance of surfactant-surfactant interaction in the mixed micelles, one should choose surfactants with their cmc s close to each other. 

Figure 2. The calculated surfactant composition in the micelles, x , as a function of the surfactant composition in the bulk solution, a. The curves are calculated from Equation 28 with X = 0 (ideal case, solid line) and X (dashed line). The experimental points are calculated from Equation 31.

Table II presents the experimental data, obtained from using bulk solutions of different NP-EO q/SDS ratios. Figure 6 shows the surfactant composition on the polystyrene latex surface as a function of the surfactant composition in the bulk solution at concentrations corresponding to the onset of micellization. If the surfactant composition on the surface were the same as that in the bulk solution, the experimental points would fall on the dashed line in the figure. Thus, the...

Figure 5. Dependence of the surfactant composition in the bulk solution on the total surfactant concentration, a) cmc curve and b) in the presence of latex. The crossing of the curves gives the solution composition and concentration at close packing of the surfactants on the PS surface.

In particular, we would like to point out two conclusions of practical importance. Firstly, a surface analysis of the serum (bulk solution) cannot give direct information on either the surfactant composition on the latex surface or in the total system. This is an important conclusion since such analyses are frequently carried out in industrial laboratories. Secondly, Figure 6 shows that if NP-EOiq is added to a system stabilized with SDS, the latter will desorb. In practice, this causes foaming problems. Such problems can be predicted, as is shown below. 

Thus, there is a simple way to predict the surfactant composition on a hydrophobic surface for a mixed surfactant system. The... 

The reason for the success of such a simple model is that the dominating force in determining the surfactant composition on the surface originates from the free energy gain of replacing hydrocarbon-water contacts with hydrocarbon-hydrocarbon and water-water contacts when a surfactant molecule is adsorbed into the surfactant monolayer. 

Beckman et al. (3) prepared an oil drilling surfactant composition consisting of a resin blend of two 98% hydrolyzed polyvinyl alcohols where the viscosity of one of the resin components was at least 50% greater than the other. 

We could show that the modification of transition metal alkoxides is a versatile tool to adjust the reactivity of precursors for the needs in lyotropic crystalline templating processes. In case of high surfactant concentrations where the liquid crystalline template is formed prior to the addition of the precursor the use of a modifier may become unnecessary. The synthesis of nanostructured rhenium dioxide and the utilization of MTO as precursor for this purpose clearly shows that in some cases the use of unusual specialized compounds is imperative. First promising results in the synthesis of nanostructured chromium oxide surfactant composites have been displayed although hydrolysis of the precursor seems to be still uncompleted within the nanostructure. The possibility of tailoring the d-values in a desired way besides the synthesis of certain particle morphologies encourages for further work in the future. 

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