Directional thermally induced phase

Hydrophilic MF membranes can be made by the dry-wet phase inversion technique, which can also be used to make PVDF membranes. On the other hand, other hydrophobic microflltration membranes are made by the thermally induced phase separation technique. In particular, semicrystalline PE, PP, and PTFE are stretched parallel to the direction of film extrusion so that the crystalline regions are aligned in the direction of stretch, while the noncrystalline region is ruptured, forming long and narrow pores. Hydrophobic membranes do not allow penetration of water into the pore until the transmembrane pressure drop reaches a threshold called the liquid entry pressure of water (LEPw). These membranes can therefore be used for membrane distillation. The track-etching method is applied to make microfiltration membranes from PC. 

The sequence and temperature of thermal induced phase transformations in the activated samples are extremely sensitive to preliminary mechanical treatment duration (Fig.8). Mechanical treatment increases the upper temperature boundary of the y- and x- AI2O3 existence up to coexistence with a-AbOa, i.e. direct formation of a-AbOs proceeds. This stabilization of low-temperature aluminas never observed previously. 

Thermally-induced phase separation (TIPS) has been shown to be an excellent way to make microporous polymeric membranes. Microporous membranes are generally prepared by TIPS process, which is based on the phenomenon that the solvent quality decreases when the temperature is decreased. On removing the thermal energy by cooling or quenching, a polymer-diluent solution phase separation occurs. After the phase separation, the diluent is removed, typically by solvent extraction, and the extractant is evaporated to yield a microporous structure. Typically, the TIPS process has been used to produce isotropic structures that is, the pore size does not vary with direction in the membrane. A few studies have been reported on the formation of... 

For describing thermally-induced phase transitions in aqueous polymers and gels, we require a solution model which accounts for directionally-specific interactions. Prange et al [11] recently proposed such a model and applied it for describing LCST behavior in aqueous/polymer solutions and temperature-induced collapse in an aqueous/gel system. Here we review the physical premise of that model, the resulting expression for and some Important results for the systems of interest here. 

A. Crowson, R.W. Hiley, T. Ingham, T. Mccreedy, A.J. Pilgrim, A. Townshend, Investigation into the detection of nitrated organic compounds and explosives by direct chemiluminescent emission during thermally induced gas phase decomposition reactions , Anal. Commun. 34 (1997) 213-216. 

An electrochemical cell [93,94] was used to obtain an efficient anodic deposition of no carrier added F-fluoride solubilized in the target water. The radioisotope is electrochemically adsorbed on the anode (glassy carbon electrode) and can be easily dried. An opposite electrical field releases the radionuclide directly into a solution of a phase transfer catalyst in dipolar aprotic solvents. The nucleophilic fluorination can be performed simultaneously if the electrochemically and thermally induced desorption of radioactivity is done in the presence of the precursor. However, the yields remain poor (3 % in the electrochemical n.c.a [ F]fluorination of anisole). 

Chlorination of Alkanes. The most direct and economical method for the manufacture of chloromethanes is the thermal free-radical chlorination of methane.176 177 Whereas in the 1940s and 1950s photochlorination was practiced in some plants, thermal chlorination is the principal industrial process today. The product chloromethanes are important solvents and intermediates. Commercial operations perform thermal chlorination at about 400-450°C. Vapor-phase photochemical chlorination of methane may be accomplished at 50-60°C. Fast and effective removal of heat associated with thermally induced free-radical substitution is a crucial point. Inadequate heat control may lead to explosion attributed to the uncontrollable pyrolysis liberating free carbon and much heat ... 

The thermal induced transformations in the mechanical treated aluminas are less studied. It is already known that mechanical treatment of y-AlaOs carried out with the compression of the material, or with the use of ball mills, accelerates the formation of the a-AbOa phase without any changes of the temperature of this process [3], More intensive affect with impact waves [5] or with heavy balls in planetary mills [6-9] reduces the temperature of the a-Al20a formation, which was observed even directly after mechanical treatment. 

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