Viscosity microemulsion

One approach is to add a cosolvent such as alcohol. An alternative to the use of alcohol is to blend two dissimilar surfactants (Hirasaki et al 2008). During the surfactant screening process in the laboratory, we must make sure the formulation produces low viscosity microemulsions with fluid interfaces and little tendency to exhibit gels or macroemulsions. This can be observed qualitatively by tilting pipettes and observing the interface fluidity (the movement or lack of movement of the interface Levitt et al., 2006). This is the only estimate of viscosity during the sahnity scan period, and it does require some experience to make a judgment. 

Despite the fact that here one has the typical composition of a microemulsion, i.e., surfactant-water-oil, one does not find a low viscosity microemulsion but instead a highly viscous system. The addition of water results in the formation of flexible cylindrical reverse micelles that form a transient network of entangled micelles and has been characterized by means of dynamic shear viscosity measurements [73,74]. Light scattering experiments on systems with cyclohexane as the oil have demonstrated that a water-induced micellar growth occurs and that these systems may be described analogously to semidilute polymer solutions [75-77]. 

The energy requirements for the formation of macroemulsions can be quite substantial. The formation of small droplets requires that the system overcome both the adverse positive interfacial free energy between the two immiscible phases working toward drop coalescence and bulk properties of the dispersed phase such as viscosity. Microemulsions, on the other hand, form spontaneously or with very gentle agitation when the proper composition is reached. 

The presence of a chromophore group in the hydrophilic or hydrophobic moieties in the surfactant molecular structure makes it sensitive to different physical responses, in particular, for the control of physicochemical parameters of colloidal systems such as surface activity, aggregation structure, viscosity, microemulsion separation, and solubilization. 

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

High Water-Base Fluids. These water-base fluids have very high fire resistance because as Httle as 5% of the fluid is combustible. Water alone, however, lacks several important quaUties as a hydrauHc fluid. The viscosity is so low that it has Httle value as a sealing fluid water has Httle or no abiHty to prevent wear or reduce friction under boundary-lubrication conditions and water cannot prevent mst. These shortcomings can be alleviated in part by use of suitable additives. Several types of high water-based fluids commercially available are soluble oils, ie, od-in-water emulsions microemulsions tme water solutions, called synthetics and thickened microemulsions. These last have viscosity and performance characteristics similar to other types of hydrauHc fluids. 

The use of surfactants has been an important positive factor for several reasons. They form O/W microemulsions, which must have low viscosity and contain a high oil content later on this oil must be separated fairly easily. 

X 10 cm by measuring molecularly dispersed water in toluene and by correcting for local viscosity differences between toluene and these microemulsions [36]. Values for Dfnic were taken as the observed self-diffusion coefficient for AOT. The apparent mole fraction of water in the continuous toluene pseudophases was then calculated from Eq. (1) and the observed water proton self-diffusion data of Fig. 9. These apparent mole fractions are illustrated in Fig. 10 (top) as a function of... 

The draft-tube airlift bioreactor was studied using water-in-kerosene microemulsions [263], The effect of draft tube area vs. the top-section area on various parameters was studied. The effect of gas flow rates on recirculation and gas carry over due to incomplete gas disengagement were studied [264], Additionally, the effect of riser to downcomer volume was also studied. The effect of W/O ratio and viscosity was tested on gas hold-up and mass transfer coefficient [265], One limitation of these studies was the use of plain water as the aqueous phase in the cold model. The absence of biocatalyst or any fermentation broth from the experiments makes these results of little value. The effect of the parameters studied will greatly depend on the change in viscosity, hold-up, phase distribution caused due to the presence of biocatalyst, such as IGTS8, due to production of biosurfactants, etc., by the biocatalyst. Thus, further work including biocatalyst is necessary to truly assess the utility of the draft-tube airlift bioreactor for biodesulfurization. 

Because the presence of an electrolyte increases the dimensions of micelles and microemulsion droplets [115], it may be expected that in presence of ions the size of microgels is also increased. This expectation could be confirmed external electrolyte increases Mw (Fig. 21) as well as dz and [r ] (Fig. 22) up to the limit of the emulsion stability. Therefore, the addition of an external electrolyte to the reaction mixture for the ECP of EUP and comonomers is a means to vary the molar mass, the diameter and the intrinsic viscosity of microgels from EUP and comonomers deliberately. 

In the water-flooding process, mixed emulsifiers are used. Soluble oils are used in various oil-well-treating processes, such as the treatment of water injection wells to improve water injectivity and to remove water blockage in producing wells. The same method is useful in different cleaning processes with oil wells. This is known to be effective since water-in-oil microemulsions are found in these mixtures, and with high viscosity. The micellar solution is composed essentially of hydrocarbon, aqueous phase, and surfactant sufficient to impart micellar solution characteristics to the emulsion. The hydrocarbon is crude oil or gasoline. Surfactants are alkyl aryl... 

With even higher water concentrations in the microemulsion the activity of the ADH decreases again. In this composition range a increasing viscosity is also observed, which indicates the beginning of the phase separation into a surfactant-rich aqueous phase and a w/o-microemulsion. As a consequence, the... 

At low water contents (-10-20%) the mixtures will generally be milky and at some composition will become clear - at this composition a microemulsion is produced and the boundary point has been ascertained and can be plotted. On increasing the water content a second transition is reached (at typically about 60% water), which is more difficult to observe. This is the formation of a gel of high viscosity and marks the other boundary of the microemulsion region. 

Figure 6 is a plot of specific conductance against mole ratios of methanol to bis(2-ethylhexyl) sodium sulfosuccinate. Like the viscosity data, there are three regions. In the first region, a rapid rise in conductance occurs, which indicates the formation of a microemulsion. It is in this region that the swollen micellar solution and liquid crystalline phase of methanol in bis(2-ethylhexyl) sodium sulfosuccinate is breaking with the formation of microspheres that constitute the microemulsion (13). 

In addition, viscosity considerations may be as important or more important than capillarity fortunately, microemulsions also have relatively low viscosities ... 

Emulsions are two-phase systems formed from oil and water by the dispersion of one liquid (the internal phase) into the other (the external phase) and stabilized by at least one surfactant. Microemulsion, contrary to submicron emulsion (SME) or nanoemulsion, is a term used for a thermodynamically stable system characterized by a droplet size in the low nanorange (generally less than 30 nm). Microemulsions are also two-phase systems prepared from water, oil, and surfactant, but a cosurfactant is usually needed. These systems are prepared by a spontaneous process of self-emulsification with no input of external energy. Microemulsions are better described by the bicontinuous model consisting of a system in which water and oil are separated by an interfacial layer with significantly increased interface area. Consequently, more surfactant is needed for the preparation of microemulsion (around 10% compared with 0.1% for emulsions). Therefore, the nonionic-surfactants are preferred over the more toxic ionic surfactants. Cosurfactants in microemulsions are required to achieve very low interfacial tensions that allow self-emulsification and thermodynamic stability. Moreover, cosurfactants are essential for lowering the rigidity and the viscosity of the interfacial film and are responsible for the optical transparency of microemulsions [136]. 

With 7ow close to zero, microemulsions will form spontaneously and are thermodynamically stable. The droplets of microemulsions tend to be monodispersed. A microemulsion may form as a separate phase in equilibrium with excess oil (O/W) or water (W/O) (i.e. it is saturated with respect to droplets). Microemulsions are usually of low viscosity. 

The importance of a surfactant - rich phase, particularly a lamellar one, to detergency performance was noted for liquid soils such as C16 and mineral oil (3.6). Videomicroscopy experiments indicated that middle phase microemulsion formation for C12E04 and Cjg was enhanced at 30 °C, while at 18 °C, oil - in - water, and at 40 °C, water - in - oil microemulsions were found to form at the oil - bath interface (3.6). A strong temperature dependence of liquid soil removal by lamellar liquid crystals, attributed to viscosity effects, has been noted for surfactant - soil systems where a middle - phase microemulsion was not formed (10). 

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