Emulsions continued factors

These are factors whose different levels can take numerical values within a well-defined domain of variation representing the domain of variation of the factor consido ed. It is theoretically possible to choose in this domain any state (or level) for the factor. Although it often occurs that only a few discrete values can be chosen in this domain of variation, we generally consider that a quantitative factor is also a continuous factor. Examples are temperature of reaction, duration of addition, concentration of a reactant, and ccrniposition of an emulsion. 

Rust inhibitors usually are corrosion inhibitors that have a high polar attraction toward metal surfaces and that form a tenacious, continuous film which prevents water from reaching the metal surface. Typical mst inhibitors are amine succinates and alkaline-earth sulfonates. Rust inhibitors can be used in most types of lubricating oils, but factors of selection include possible corrosion of nonferrous metals or formation of emulsions with water. Because mst inhibitors are adsorbed on metal surfaces, an oil can be depleted of its mst inhibitor. In certain cases, it is possible to correct the depletion by adding more inhibitor. 

For moderate ratios (<3), the type of emulsion is decided by several factors (5), such as order of addition or type of emulsifier. One Hquid slowly added to the other with agitation usually results in the last-mentioned phase being the continuous one. Another factor is preferred solubiHty of the emulsifier the phase in which the emulsifier is soluble most probably is continuous. 

Viscosity Increase. The flocculation rate of an emulsion is iaversely proportional to the viscosity of the continuous phase and an iacrease of the viscosity from 1 mPa-s (=cP) (water at room temperature) to a value of 10 Pa-s (100 P) (waxy Hquid) reduces the flocculation rate by a factor of 10,000. Such a change would give a half-life of an unprotected emulsion of a few hours, which is of Httle practical use. 

A wellbore fluid has been developed that has a nonaqueous continuous liquid phase that exhibits an electrical conductivity increased by a factor of 10 to 10 compared with conventional invert emulsion. 0.2% to 10% by volume of carbon black particles and emulsifying surfactants are used as additives. Information from electrical logging tools, including measurement while drilling and logging while drilling, can be obtained [1563]. 

One way that contaminants are retained in the subsurface is in the form of a dissolved fraction in the subsurface aqueous solution. As described in Chapter 1, the subsurface aqueous phase includes retained water, near the solid surface, and free water. If the retained water has an apparently static character, the subsurface free water is in a continuous feedback system with any incoming source of water. The amount and composition of incoming water are controlled by natural or human-induced factors. Contaminants may reach the subsurface liquid phase directly from a polluted gaseous phase, from point and nonpoint contamination sources on the land surface, from already polluted groundwater, or from the release of toxic compounds adsorbed on suspended particles. Moreover, disposal of an aqueous liquid that contains an amount of contaminant greater than its solubility in water may lead to the formation of a type of emulsion containing very small droplets. Under such conditions, one must deal with apparent solubility, which is greater than handbook contaminant solubility values. 

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... 

Experiments on the stability of the HIPEs indicated that one of the most important factors was the solubility of the emulsifier in the continuous (formamide) phase. Thus, the higher the surfactant solubility, the more stable the emulsion. The emulsifier concentration was also important stability increased to a maximum, then decreased, with increasing surfactant concentration. Surprisingly, the HLB number did not appear to have much effect on the stability of the emulsions, over the range studied (11 to 14). This was attributed to the high concentration of emulsifier in the continuous phase, although the narrow HLB value range is probably also a factor. 

Such reactions can take place predominantly in either the continuous or disperse phase or in both phases or mainly at the interface. Mutual solubilities, distribution coefficients, and the amount of interfadal surface are factors that determine the overall rate of conversion. Stirred tanks with power inputs of 5-10 HP/1000 gal or extraction-type equipment of various kinds are used to enhance mass transfer. Horizontal TFRs usually are impractical unless sufficiently stable emulsions can be formed, but mixing baffles at intervals are helpful if there are strong reasons for using such equipment. Multistage stirred chambers in a single shell are used for example in butene-isobutane alkylation with sulfuric acid catalyst. Other liquid-liquid processes listed in Table 17.1 are numbers 8, 27, 45, 78, and 90. 

Viscosity. This parameter can be monitored by standard rheological techniques. The rheological properties of emulsions, reviewed by Sherman (1983), can be complex, and depend on the identity of surfactants and oils used, ratio of disperse and continuous phase, particle size, and other factors. Flocculation will generally increase viscosity thus, monitoring viscosity on storage will be important for assessing shelf-life. 

Statistical mechanics was originally formulated to describe the properties of systems of identical particles such as atoms or small molecules. However, many materials of industrial and commercial importance do not fit neatly into this framework. For example, the particles in a colloidal suspension are never strictly identical to one another, but have a range of radii (and possibly surface charges, shapes, etc.). This dependence of the particle properties on one or more continuous parameters is known as polydispersity. One can regard a polydisperse fluid as a mixture of an infinite number of distinct particle species. If we label each species according to the value of its polydisperse attribute, a, the state of a polydisperse system entails specification of a density distribution p(a), rather than a finite number of density variables. It is usual to identify two distinct types of polydispersity variable and fixed. Variable polydispersity pertains to systems such as ionic micelles or oil-water emulsions, where the degree of polydispersity (as measured by the form of p(a)) can change under the influence of external factors. A more common situation is fixed polydispersity, appropriate for the description of systems such as colloidal dispersions, liquid crystals, and polymers. Here the form of p(cr) is determined by the synthesis of the fluid. 

The common raw materials of particleboard are wood, adhesive, and wax emulsion. High quality particleboard at the optimum production rate demands continuous monitoring of the wood material to determine when adjustments should be made in the process or the adhesive. Monitoring of the adhesive and wax emulsion quality is a critical, but often ignored, factor in particleboard manufacture. 

When emulsion techniques are used for microsphere preparation, a number of processing factors influences the final structure of the microspheres, e.g., the choice of solvents and surfactants, phase viscosity, the ratio of the dispersed to the continuous phase, mixing speed, processing temperature, and time. Micro-... 

Let us first consider an inverted W/O emulsion made of 10% of 0.1 M NaCl large droplets dispersed in sorbitan monooleate (Span 80), a liquid surfactant which also acts as the dispersing continuous phase. At this low droplet volume fraction, the rheological properties of the premixed emulsion is essentially determined by the continuous medium. The rheological behavior of the oil phase can be described as follows it exhibits a Newtonian behavior with a viscosity of 1 Pa s up to 1000 s 1 and a pronounced shear thinning behavior above this threshold value. Between 1000 s 1 and 3000 s1, although the stress is approximately unchanged, the viscosity ratio is increased by a factor of 4. 

Polymerization processes are characterized by extremes. Industrial products are mixtures vwth molecular weights of 10 to 10. In a particular polymerization of styrene the viscosity increased by a factor of 10 as conversion went from 0 to 60 percent. The adiabatic reaction temperature for complete polymerization of ethylene is 1,800 K (3,240 R). Heat transfer coefficients in stirred tanks vwth high viscosities can be as low as 25 W/(m °C) (16.2 Btu/[h ft °Fj). Reaction times for butadiene-styrene rubbers are 8 to 12 h polyethylene molecules continue to grow for 30 min whereas ethyl acrylate in 20% emulsion reacts in less than 1 min, so monomer must be added gradually to keep the temperature vwthin limits. Initiators of the chain reactions have concentration of 10 g mol/L so they are highly sensitive to poisons and impurities. 

Unzueta et al. [18] derived a kinetic model for the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) employing both the micellar and homogeneous nucleation mechanisms and introducing the radical absorption efficiency factor for micelles, F, and that for particles, Fp. They compared experimental results with model predictions, where they employed the values of Fp=10 and Fn,=10", respectively, as adjustable parameters. However, they did not explain the reason why the value of Fp, is an order of magnitude smaller than the value of Fp. Sayer et al. [19] proposed a kinetic model for continuous vinyl acetate (VAc) emulsion polymerization in a pulsed... 

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