Phase inversion temperature distribution

It is generally found that the same circumstances that affect the solution characteristics of nonionic surfactants (their cmc, micelle size, cloud point, etc.) will also affect the PIT of emulsions prepared with the same materials. For typical polyoxyethylene nonionic surfactants, increasing the length of the POE chain will result in a higher PIT for a given oil-aqueous phase combination (Fig. 11.12), as will a broadening of the POE chain length distribution. The use of phase inversion temperatures, therefore, represents a very useful... 

In a novel process, FIPI was also applied to the emulsiflcation of polymer melts in water, thus providing an alternative method to emulsion polymerization for the production of latexes. " " In fact, some thermoplastic melts (such as polyethylene) cannot be obtained through the emulsion polymerization route hence, the present technique is an example of PI providing a novel product form. To achieve the emulsiflcation of thermoplastics, it is necessary to operate near or above 100°C and at elevated pressures, which necessitates the use of polymer processing equipment fitted with a MFCS mixer at the outlet. It was found that molecular surfactants could not be used to obtain the initial (water-in-polymer melt) emulsion. Instead, hydrophobically modified water-soluble polymers were used as the surface active material. After the phase inversion in the MFCS mixer, the resulting emulsion was diluted to the level required. This also freezes the molten latexes. The important attributes of FIPI emulsification include a low level of surfactant use, low temperature processing, production of submicrometer particles with a narrow size distribution, and production of novel products. 

There are a number of other parameters, in addition to those listed, such as the use of additives (low molecular weight as well as high molecular weight components), the molecular weight distribution, the ability to crystallise or aggregate, the temperature of the polymer solution and of the coagulation bath, etc., that also influence the ultimate structure obtained after phase inversion. These latter factors will not be considered here. 

One of the most useful techniques for preparing cosmetic emulsions is to apply the principle of phase inversion (described in detail in Chapters 6 and 9). For example, to prepare an O/W emulsion one could start with a W/O emulsion, which could be obtained at high temperature (above the HLB temperature of the emulsion). This W/O emulsion is then rapidly cooled to produce the final O/W emulsion. Alternatively, one may start with a W/O emulsion, by dissolving the surfactant in the oil phase and gradually adding water while mixing. When the water content reaches a certain level, inversion to O/W emulsion will occur. This emulsion will have a smaller droplet size distribution than the system produced by directly emulsifying the oil into an aqueous solution of surfactant. 

A gel polymer membrane based on P(MMA-AN-VAc) has been prepared by emulsion polymerization and phase inversion, and exhibits low crystallinity and Tg. Its ionic conductivity at room temperature is 3.48 x 10 g/cm, and its electrochemically stable voltage is above 5.0 V (vs. LP/Li). By further adding fumed silica, the semicrystalline state is changed into an amorphous porous structure. When 10 wt% fumed silica is added, the porosity of the polymer increases with an even distribution of pores. This intercoimected porous structure can improve the electrolyte retention ability and increase the ionic conductivity of the gel polymer from 3.48 x 10 g/cm to 5.13 x 10 3 S/cm. At the same time, the thermal and electrochemical stability of the membrane and the cycling performance of the assembled battery are improved. 

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