Emulsifying devices

Emulsions are usually prepared by the application of mechanical energy produced by a wide range of agitation techniques. These disrupt droplets by the application of either shear forces in laminar flow or inertial forces in turbulent flow. Emulsifying devices ranging from simple hand mixers and stirrers to the use of propeller or turbine mixers, static mixers, colloid mills, homogenizers, and ultrasonic devices have been used. 

Hence, such a plot should be prepared for the particular application and emulsifying device to be dealt with. As far as some advice could be helpful, it may be said that above 60-70% internal idiase. most emulsions become p.seu-doplasiic fluids and their viscosity depends on applied shear r e. often according to a power law model. Above 85—90% internal phase, the emulsion no longer behaves as a simple fluid and a viscoelastic description is often useful. 

If Pb > Pa, liquid in the jet flows from B to A and deformation of the jet will be restored. This occurs when < 2%R. i > liiR, Pa > Pb and the ensuing flow of liquid from A to B will cause rupture of the jet. Applications of the phenomenon of capillary instability are found, for example, in sprayers that produce aerosols, in emulsifying devices, and in spray drying. 

Schuster [59] discussed the different emulsifying devices and the emulsification mechanism. 

If two liquids of only slight mutual solubility are dispersed by high-turbulence devices in the absence of a surfactant or emulsifying agent, a... 

In the early 1970s Li [13] proposed a method that is now called Emulsion (surfactant) Liquid Membrane (ELM) or Double Emulsion Membrane (DEM) (Fig. 3). The name reveals that the three liquid system is stabilized by an emulsifier, the amount of which reaches as much as 5 % or more with respect to the membrane liquid. The receiving phase R, which usually has a smaller volume than the donor solution, F of similar nature, is finally dispersed in the intermediate phase, M. In the next step the donor solution F is contacted with the emulsion. For this purpose, the emulsion is dispersed in the donor solution F by gentle mixing typically in a mixer-settler device. After this step, the emulsion is separated and broken. The enriched acceptor solution is further processed and the membrane liquid M is fed back for reuse. 

A schematic arrangement of latest Hajek s device is shown in Fig J. It consists of a double-walled cylindrical vessel, 15-mm ID, insulated with glass wool and contg 20 g of Al + Fe203 + emulsifier, but no water (D). 

Dr. A. Shaw at the University of Maryland Eastern Shore in Princess Anne, Maryland, is evaluating textile substrate for pesticide barrier effectiveness and comfort. Tests will be conducted to assess effectiveness of decontamination processes for these personal protection devices. Diazinon emulsifiable concentrates will be used to contaminate fabrics. Simulated wear studies will be conducted in the laboratory to assess the efficacy of these fabrics in protecting human health. 

The top-down approach involves size reduction by the application of three main types of force — compression, impact and shear. In the case of colloids, the small entities produced are subsequently kinetically stabilized against coalescence with the assistance of ingredients such as emulsifiers and stabilizers (Dickinson, 2003a). In this approach the ultimate particle size is dependent on factors such as the number of passes through the device (microfluidization), the time of emulsification (ultrasonics), the energy dissipation rate (homogenization pressure or shear-rate), the type and pore size of any membranes, the concentrations of emulsifiers and stabilizers, the dispersed phase volume fraction, the charge on the particles, and so on. To date, the top-down approach is the one that has been mainly involved in commercial scale production of nanomaterials. For example, the approach has been used to produce submicron liposomes for the delivery of ferrous sulfate, ascorbic acid, and other poorly absorbed hydrophilic compounds (Vuillemard, 1991 ... 

Centrifugal Contactors. These devices have large capacities per unit, short residence times, and small holdup. They can handle systems that emulsify easily or have small density differences or large interfacial tensions or need large ratios of solvent to feed. Some types are employed as separators of mixtures made in other equipment, others as both mixers and settlers, and some as differential contactors. 

By many properties emulsion aqueous films are analogous to foam films. There are several review articles dedicated to properties of emulsion aqueous films [e.g. 320,503-506]. The properties of microscopic emulsion aqueous films (kinetics of thinning, determination of equilibrium thickness, etc.) are studied employing devices quite similar to those used for foam films [503]. Analogous to foam films, stable (metastable) emulsion films are formed only in the presence of surfactants (emulsifiers) at concentrations higher than the critical concentration of formation of black spots C or the concentration, corresponding to... 

Ray and Schork (1980) have developed an on-Hne device for measuring surface tension. A bubble rise technique is used. If this method or the light scattering technique of Hamielec were used in a oMitrol system one could presumably alter the feed rate of a kq/ ingredient, probsbiy emulsifier, to prevent undesired transients. More work is needed to demonstrate the potential of these methods. 

The fact that most vegetable oils and fats are nontoxic allows them to be used as reliable excipients or carriers in many pharmaceutical formulations. Vegetable oils and fats have been approved as excipients to facilitate delivery of bioactive compounds, to act as fillers, binders, lubricants, solubilizers, emulsifiers, and emollients in a variety of delivery forms including tablets, capsules, suppositories, emulsions (enteral/parenteral), ointments, creams, and lotions. Other nondirect applications include artificial blood, gene delivery, diagnostic imaging, and medical devices (27). 

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