Fabrication technology phase separation

The term compatibility is used extensively in the blend literature and is used synonymously with the term miscibility in a thermodynamic sense. Compatible polymers are polymer mixtures that do not exhibit gross symptoms of phase separation when blended or polymer mixtures that have desirable chemical properties when blended. However, in a technological sense, the former is used to characterize the ease of fabrication or the properties of the two polymers in the blend [3-5]. 

The first two points represent a general motivation for miniaturization in separation science independent of the actual fabrication technology. The benefit of a reduction of the consumption of sample, reagents, and mobile phase in chemical and biochemical analysis is self-evident and does not need to be discussed further (reduced consumption of precious samples and reagents, reduced amounts of waste, environmental aspects). This advantage is, however, sharply contrasted by its severe implications on the detection side, as discussed elsewhere in this volume in detail. The detection of the separated zones of very small sample volumes critically depends on the availability of highly sensitive detection methods. It is not surprising that extremely sensitive laser-induced-fluorescence (LIF) has been the mostly used detection principle for chip-based separation systems so far. 

Finally, the current status of the inorganic membrane technology is summarized for an overall perspective. The future is speculated based on that perspective to provide a framework for future developments in the synthesis, fabrication and assembly of inorganic membranes and their uses for traditional liquid-phase separation, high-temperature gas separation and membrane reactor applications. 

Fong, J.W. Microencapsulation by solvent evaporation and organic phase separation processes. In Controlled Release Systems Fabrication Technology Hsieh, D., Ed. CRC Press Boca Raton, 1988 1, 81-108. 

Despite the advantages of CEC over CE and HPLC, particle-packed columns are plagued with problems such as the difficulty in the preparation of frits to retain the stationary phase and bubble formation that results in current leakage and EOF breakdown. These problems set the pace for the development of column technology to overcome the problems associated with particle-packed columns and to improve on the speed of separation of analytes in mixtures. The fabrication of a continuous porous rod (monoliths), not requiring any frits and ensuring a constant and uniform current flow to give a stable EOF has so far proved a potential development for microseparations. ... 

A wide variety of approaches are currently being used in the fabrication and technology of columns for capillary electrochromatography (CEC). Continuous polymer bed, or monolithic columns (see Section 3.4), manufactured by in-situ polymerization within the columns, have been used in numerous application areas and have been shown to be highly efficient. In a second approach, a sol-gel process is employed to form a silica xerogel within the capillary, followed by bonding of the stationary-phase group alternatively, the separation medium itself may be polymerized in situ. 

The body of scientific knowledge behind food fabrication started to accumulate less than 50 years ago. It has been in the last 20 years that the study of foods as materials has become a field in its own. It has been fostered by advances in related areas, most notably polymer science, mesoscopic physics, microscopy, and other advanced physical techniques. Progress in separations science has led to economically feasible processes that make available refined and functional food ingredients that replace or complement traditional raw materials. New technologies, most notably the use of membranes and microdevices, promise to bring the scale of fabrication closer to that of micro structural elements in dispersed phases (droplets, bubbles). 

Uranous nitrate [U(N03)4] solution is used for the quantitative reduction of plutonium from loaded tributyl phosphate (TBP) phase [8]. Membrane cell technology was investigated for the production of 100% uranous nitrate solution [9], which is to be used in the partition cycle of the PUREX process in the fuel reprocessing plant. The membranes used hitherto have suffered from mechanical instability. A study was carried out at the BARC to obtain 100% uranous nitrate solution using a membrane-based electrolytic cell. The membrane used in this study was a thin polymer film reinforced with a Teflon fabric. The film was used as a separator between the anolyte and catholyte chambers, which are made of perfluorinated polymers, thus offering high thermal and chemical stability. 

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