Surfactant concentration, influencing factors

High molecular weight monodisperse polystyrene latexes have been prepared by this method [158]. A number of factors were found to influence the size and dispersity of the particles. The size decreased with increasing surfactant concentration and decreasing internal phase volume, and a more monodisperse latex... 

In work, the reaction of alkylated branched PEI-10 (APEI-10) bearing tetradecyl substituents (PEI5) with phosphinate 12 is studied in the presence of PM in toluene. The kobs versus Cpm dependence has an extremum. A maximum twofold acceleration of the reaction is observed, followed by a ca. 5-7-fold inhibition with the further increase in the surfactant concentration. Similar to the above phosphorylation reaction, the unfavorable influence of the microenvironment and the prevalent positive contribution of the concentration factor occur in this system. In particular, the values Em = 0.55 and Fc = 31.0 are obtained when fitting the kinetic data in terms of Equation 15.1 (Table 15.1). 

The bidimensional mapping does not take into account several secondary factors that are, however, known to influence the emulsion type and properties. Recent research has shown that they may be accounted for as a modification of the bidimensional map character istics. First, it was found that an increase in surfactant concentration tends to widen the A zone (195), i.e., the region in which the emulsion type is determined by the formulation. 

Alteration of the surface tension of the DEG-l-OP-10 system with temperature is greatly influenced by the surfactant concentration (Fig. 2.2). At llkg/m of OP-10, the surface tension does not depend on temperature, and at high surfactant concentrations even increases. The OP-10 associations with DEG-1 must be of increased solubility and must easily desorb from the boundary surface in the course of raising the temperature. Thus, temperature increase may result both in decrease of the surface tension on account of increase of the thermal motion of the molecules eind in its increase due to the desorption of surfactant molecules, and this increase has a direct dependence on the sxufactant concentration. Superposition of these factors for certain surfactant concentrations can bring about independence of the system siuface tension on temperature, confirmed by experiment. In the case of siuTactant desorption, the system entropy increased due... 

The adsorption of ionic surfactant on metalic surfaces at the liquid-solid interface is influenced and controlled by many factors, such as the surfactant concentration, counterion concentration and surface charge. The effect of these factors on the adsorption of alkylpyridinium on silver surfaces studied by means of the SERS spectroscopy are presented and discussed in this section. 

In more concentrated surfactant solutions where rod-like and branched mieelles exist, theoretical descriptions of these associative thickeners are lacking. What is clearly understood is that the nature of the surfactants profoundly influences the rheology of personal care formulations (105-107). Factors that influence the electrical environment of the formulation, such as salt and pH, also affect the behavior of these thickeners. Unfortunately, the lack of understanding typically means that formulators must use trial and error to develop stable formulations. 

Abstract. This article describes a hydrodynamic model of collaborative flnids (oil, water) flow in porons media for enhanced oil recovery, which takes into account the influence of temperature, polymer and surfactant concentration changes on water and oil viscosity. For the mathematical description of oil displacement process by polymer and surfactant injection in a porous medium, we used the balance equations for the oil and water phase, the transport equation of the polymer/surfactant/salt and heat transfer equation. Also, consider the change of permeabihty for an aqueous phase, depending on the polymer adsorption and residual resistance factor. Results of the numerical investigation on three-dimensional domain are presented in this article and distributions of pressure, saturation, concentrations of poly mer/surfactant/salt and temperature are determined. The results of polymer/surfactant flooding are verified by comparing with the results obtained from ECLIPSE 100 (Black Oil). The aim of this work is to study the mathematical model of non-isothermal oil displacement by polymer/surfactant flooding, and to show the efficiency of the combined method for oil-recovery. 

The absolute values of the interfacial tensions varied between different amphi-philes and solvents (Table 1). AOT, which is well known in the literature for the formation of microemulsions, showed the lowest surface tension at the interface of both solvents. The other nonionic snrfactants mentioned here. Span 80 and Brij 72 showed shghtly higher valnes. This was also observed for Lecithine, but this lipid precipitated partly during the spinning-drop measurements. Due to this phenomenon, it was not possible to measure accurate data for this emulsifying compound. The interfacial tension had also some influence on the mean size of the emulsion droplets and on the stability of the vesicles (Table 3). In addition to the stationary values of the surface tension, dynamic processes as the surfactant diffusion represented another important factor for the process of stimulated vesicle formation. If an aqueous droplet passed across the fluid interface it carried-over a thin layer of emulsifiers and thereby lowered the local surfactant concentration in the vicinity of the oil-water interface. In the short time span, before the next water droplet approached the interface, the surfactant films should entirely reform and this only occurred, if the surfactant diffusion was fast enough. 

Herein are (p the dispersed phase content, Afgurf the molar mass of the surfactant, Csurf the concentration of surfactant, (I32 the Sauter mean diameter of the droplet collective, /Omonomer the density of the monomer, Na the Avogadro constant and (1-Cb/ctotai) is a correction factor which accounts for the surfactant that does not adsorb at the interface but resides in the continuous bulk phase. Asurf shows the influence of the inorganic particles on the surfactant concentration needed to stabilize a certain amount of interface can be seen directly. 

The influence of surfactants and plant species on the retention of spray solution has been examined by de Ruiter and Uffing. They reported a linear relationship between retention and the logarithm of surfactant concentrations. It would appear that there is a need to add a surfactant concentration far in excess of the critical micelle concentration (CMC) and that the diffusion of surfactant from the bulk to the surface of the flattening drop is a retention-determining factor. The dynamic surface tension is regarded as a useful parameter determining surfactant type and concentration with respect to efficient surface retention. 

The final factor influencing the stabiHty of these three-phase emulsions is probably the most important one. Small changes in emulsifier concentration lead to drastic changes in the amounts of the three phases. As an example, consider the points A to C in Figure 16. At point A, with 2% emulsifier, 49% water, and 49% aqueous phase, 50% oil and 50% aqueous phase are the only phases present. At point B the emulsifier concentration has been increased to 4%. Now the oil phase constitutes 47% of the total and the aqueous phase is reduced to 29% the remaining 24% is a Hquid crystalline phase. The importance of these numbers is best perceived by a calculation of thickness of the protective layer of the emulsifier (point A) and of the Hquid crystal (point B). The added surfactant, which at 2% would add a protective film of only 0.07 p.m to emulsion droplets of 5 p.m if all of it were adsorbed, has now been transformed to 24% of a viscous phase. This phase would form a very viscous film 0.85 p.m thick. The protective coating is more than 10 times thicker than one from the surfactant alone because the thick viscous film contains only 7% emulsifier the rest is 75% water and 18% oil. At point C, the aqueous phase has now disappeared, and the entire emulsion consists of 42.3% oil and 57.5% Hquid crystalline phase. The stabilizing phase is now the principal part of the emulsion. 

Some investigations have emphasized the importance of micellar size as a control parameter of nanoparticle size [224]. It has been suggested that other factors also influence the nanoparticle size, such as the concentration of the reagents, hydration of the surfactant head group, intermicellar interactions, and the intermicellar exchange rate [198,225-228],... 

Cellulase and all chemicals used in this work were obtained from Sigma. Hydrolysis experiments were conducted by adding a fixed amount of 2 x 2 mm oflSce paper to flasks containing cellulase in 0.05 M acetate buffer (pH = 4.8). The flasks were placed in an incubator-shaker maintained at 50 °C and 100 rpm. A Box-Behnken design was used to assess the influence of four factors on the extent of sugar production. The four factors examined were (i) reaction time (h), (ii) enzyme to paper mass ratio (%), (iii) amount of surfactant added (Tween 80, g/L), and (iv) paper pretreatment condition (phosphoric add concentration, g/L), as shown in Table 1. Each factor is coded according to the equation... 

The reverse microemulsion method can be used to manipulate the size of silica nanoparticles [25]. It was found that the concentration of alkoxide (TEOS) slightly affects the size of silica nanoparticles. The majority of excess TEOS remained unhydrolyzed, and did not participate in the polycondensation. The amount of basic catalyst, ammonia, is an important factor for controlling the size of nanoparticles. When the concentration of ammonium hydroxide increased from 0.5 (wt%) to 2.0%, the size of silica nanoparticles decreased from 82 to 50 nm. Most importantly, in a reverse microemulsion, the formation of silica nanoparticles is limited by the size of micelles. The sizes of micelles are related to the water to surfactant molar ratio. Therefore, this ratio plays an important role for manipulation of the size of nanoparticles. In a Triton X-100/n-hexanol/cyclohexane/water microemulsion, the sizes of obtained silica nanoparticles increased from 69 to 178 nm, as the water to Triton X-100 molar ratio decreased from 15 to 5. The cosurfactant, n-hexanol, slightly influences the curvature of the radius of the water droplets in the micelles, and the molar ratio of the cosurfactant to surfactant faintly affects the size of nanoparticles as well. 

It is worth reviewing how kinetic and thermodynamic factors generally affect the growth of nanostructures under the influence of surfactants. Though they used CdSe and PbS respectively to study the surfactant-assisted synthesis of nanorods, Peng et al. and Lee et al. have produced a pair of quite complimentary studies. Peng etal. observed that kinetic control via monomer concentration was the principle factor in their growth... 

A number of factors greatly influence the stability of high internal phase emulsions, including the nature of the surfactant, its concentration, the nature of the continuous phase, the temperature and the presence of salts in the aqueous... 

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