Phase inversion emulsion

Fernandez, P., Andre, V., Rieger, J. and Kuhnle, A. (2004) Nano-emulsion formation by emulsion phase inversion. Colloids and Surfaces A Physicochemical and Engineering Aspects, 251, 53-58. 

P. Fernandez, V. Andre, J. Rieger, and A. Ktlhnle Nano-Emulsion Formation by Emulsion Phase Inversion. Colloid and Surfaces A Physicochem. Eng. Aspects 251, 53 (2004). 

Aveyard R, Binks BP, Fletcher PDI, Ye X. Coalescence lifetimes of oil and water drops at the planar oil-water interface and their relation to emulsion phase inversion. Progr Colloid Polym Sci 1992 89 114-117. 

Because of the complex flow behavior ofviscoelastic polymer blends its interpretation becomes easier when compared with the simpler, model systems discussed in Sections 2.1.1 and 2.1.2. For the dominant immiscible blends the emulsions of one liquid dispersed in another provide the best model. While compatibilizers are used for stabilization of blends, in emulsion a diversity of surfactants has been employed. As in blends, a progressive increase of concentration of the emulsion minor phase invariably leads to the co-continuity of phases and phase inversion. However, while emulsion phase inversion is controlled mainly by the emulsifier, in blends the inversion mainly depends on the viscosity ratio, A = th/th (Figure 2.3) [4]. 

The most common procedure for assessing phase inversion is to measure the conductivity or the viscosity of the emulsion as a function of c ), increasing temperature and/or addition of electrolyte. For example, for an 0/W emulsion phase inversion to W/0 is accompanied by a rapid decrease in conductivity and viscosity. 

FIGURE 15.1. When water and oil are mixed in the presence of an emulsifier, an emulsion is formed. The type of emulsifier influences the type of emulsion Emulsifier A (hydrophilic) forms o/w emulsions and Emulsifier B (lipophilic ) forms w/o emulsions. Heating an o/w emulsion can convert it to a w/o emulsion (phase inversion). 

The phase-inversion temperature (PIT) is defined as the temperature where, on heating, an oil—water—emulsifier mixture inverts from O/W to a W/O emulsion [23]. The PIT correlates very well with the HLB as illustrated in Fig. XIV-10 [72, 73]. The PIT can thus be used as a guide in emulsifier selection. 

If a linear mbber is used as a feedstock for the mass process (85), the mbber becomes insoluble in the mixture of monomers and SAN polymer which is formed in the reactors, and discrete mbber particles are formed. This is referred to as phase inversion since the continuous phase shifts from mbber to SAN. Grafting of some of the SAN onto the mbber particles occurs as in the emulsion process. Typically, the mass-produced mbber particles are larger (0.5 to 5 llm) than those of emulsion-based ABS (0.1 to 1 llm) and contain much larger internal occlusions of SAN polymer. The reaction recipe can include polymerization initiators, chain-transfer agents, and other additives. Diluents are sometimes used to reduce the viscosity of the monomer and polymer mixture to faciUtate processing at high conversion. The product from the reactor system is devolatilized to remove the unreacted monomers and is then pelletized. Equipment used for devolatilization includes single- and twin-screw extmders, and flash and thin film evaporators. Unreacted monomers are recovered for recycle to the reactors to improve the process yield. 

At low temperature, nonionic surfactants are water-soluble but at high temperatures the surfactant s solubUity in water is extremely smaU. At some intermediate temperature, the hydrophile—Hpophile balance (HLB) temperature (24) or the phase inversion temperature (PIT) (22), a third isotropic Hquid phase (25), appears between the oil and the water (Fig. 11). The emulsification is done at this temperature and the emulsifier is selected in the foUowing manner. Equal amounts of the oil and the aqueous phases with aU the components of the formulation pre-added are mixed with 4% of the emulsifiers to be tested in a series of samples. For the case of an o/w emulsion, the samples are left thermostated at 55°C to separate. The emulsifiers giving separation into three layers are then used for emulsification in order to find which one gives the most stable emulsion. 

The phase inversion temperature (PIT) method is helpful when ethoxylated nonionic surfactants are used to obtain an oil-and-water emulsion. Heating the emulsion inverts it to a water-and-oil emulsion at a critical temperature. When the droplet size and interfacial tension reach a minimum, and upon cooling while stirring, it turns to a stable oil-and-water microemulsion form. " ... 

Phase inversion technique the external phase is added to the internal phase. For example, if an O/W emulsion is to be prepared, the aqueous phase is added to the oil phase. First a W/O emulsion is formed. At the inversion point, the... 

Phase Inversion The phase inversion of brine/oil/surfactant systems was established routinely by measuring solution conductivity employing a Jenway FWA 1 meter and cell. The process identifies the range over which a large decrease in conductivity occurs as the sytem under test is converted from an oil in water emulsion to a water in oil emulsion. Phase... 

Optimal Salinities Phase inversions at optimal salinity were assessed routinely by salt titrations into systems maintained at constant temperature. For the Leonox IOS surfactant system, increasing levels of salinity were necessary to cause the emulsion state to phase invert as the alkane molecular weight increased (Figure 11). Ihe initial conductivity value at the condition where zero salt had been added may in part reflect the salt contamination naturally present within the supplied formulation. Ihe internal olefin sulphonate species again revealed a linear relationship between EACN and optimal salinity as did all ionic formulations under test (see Figures 12 and 13, plus Table III). Ihe estimation of EACN values for both toluene... 

Izquierdo, P., Esquena, J., Tadros, T.F., Dederen, C., Garcia, M.J., Azemar, N. and Solans, C. (2002) Formation and stability of nano-emulsions prepared using the phase inversion temperature method. Langmuir, 18 (1), 26-30. 

Thus, an estimation can be made of the hydrophilicity of the crown ring. The acetal-type crown ring obtained from hexaethyl-ene glycol and a higher aliphatic aldehyde is estimated to be e-quivalent to about four OE units in an alkyl POE monoether, from our study of the cloud point (11). Moroi et al. concluded, from a comparison of the cmc, that a diaza-18-crown-6 is equivalent to 20 OE units in the usual type of nonionic (12). Okahara s group evaluated the effective HLB based on the cloud point, phenol index and phase-inversion-temperature in emulsion of oil/water system and they concluded that 18-crown-6 and monoaza-18-crown-6 rings with dodecyl group are approximately equivalent to 4.0 and 4.5 units, respectively, of OE chains with the same alkyl chain (17). 

The most frequent emulsiflcation using phase inversion is known as the PIT (Phase Inversion Temperature) method [81-83] and occurs through a temperature quench. This method is based on the phase behavior of nonionic surfactants and the correlation existing between the so-called surfactant spontaneous curvature and the type of emulsion obtained. 

Phase inversion may be used to emulsify highly viscous substances such as bitumen (the viscosity of which can be as high as 10 Pa-s at room temperature) [134]. The most frequent industrial technique used to prepare bitumen-in-water emulsions consists of mixing hot bitumen (130°C) with an aqueous phase ( 60°C at... 

D.J. Miller, T. Henning, and W. Grtibein Phase Inversion of W/O Emulsions by Adding Hydrophilic Surfactant—a Technique for Making Cosmetics Products. ... 

K. Shinoda and H. Aral The Correlation between Phase Inversion Temperature in Emulsion and Cloud Point in Solution of Nonionic Emulsifier. J. Phys. Chem. 68,... 

B.W. Brooks and H.N. Richmond Phase Inversion in Non-Ionic Surfactant-Oil-Water Systems, I. The Effect of Transitional Inversion on Emulsion Drop Size. Chem. Eng. Sci. 49, 1053 (1994). 

P. Izquierdo, J. Esquena, T.F. Tadros, J.C. Dederen, M.J. Garcia, N. Azemar, and C. Solans Formation and Stability of Nano-Emulsions Prepared Using the Phase Inversion Method. Langmuir 18, 26 (2002). 

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