Membrane by heat

The first reported membrane modification method involved annealing of porous membranes by heat-treatment. Zsigmondy and Bachmann in 1922 demonstrated that... 

Evaporation is the oldest process for the concentration of liquid foods. Temperatures are higher compared to those of the more modern membrane filtration or freeze concentration processes. Tocopherols, carotenes, ascorbic acid, flavonoids and other phenolic antioxidants are partially destroyed by heating. Therefore, it is necessary to minimise the time needed for evaporation, and heating to the evaporation temperature should be carried out very rapidly. The temperature may be decreased if the pressure is reduced. The process is then more expensive, but losses of antioxidants become substantially lower. 

Membranes (50 pi in a total assay volume of 100 pi) were incubated with UDP-Gal (0.1 mM) and MgSO (10 mM) in 25 mM Tris-HCl buffer pH 7.5, for 10 or 60 min. Reactions were stopped by heating at 100°C for 3 min. Lupin galactan (0.1 mg) was added as a 0.1% solution, methanol was added to give a final concentration of 70% by volume, and the tubes were capped, heated at 70°C for 5 min and centrifuged (13000g 5 min). Supernatants were discarded or retained for analysis. Pellets were washed twice more with 70% methanol at 70 C and the supernatants were discarded. The final pellets were either dissolved in preparation for scintillation counting, or were suspended in water and freeze dried in preparation for analysis. 

In the first example, procaine penicillin, an aqueous vehicle containing the soluble components (such as lecithin, sodium citrate, povidone, and polyoxyethylene sorbitan monooleate) is filtered through a 0.22 pm membrane filter, heat sterilized, and transferred into a presterilized mixing-filling tank. The sterile antibiotic powder, which has previously been produced by freeze-drying, sterile crystallization, or spray-drying, is aseptically added to the sterile solution while mixing. After all tests have been completed on the bulk formulation, it is aseptically filled. 

In general, aqueous ophthalmic solutions are manufactured by methods that call for the dissolution of the active ingredient and all or a portion of the excipients into all or a portion of the water and the sterilization of this solution by heat or by sterilizing filtration through sterile depth or membrane filter media into a sterile receptacle. If incomplete at this point, this sterile solution is then mixed with the additional required sterile components, such as previously sterilized solutions of viscosity-imparting agents, preservatives, and so on, and the batch is brought to final volume with additional sterile water. 

Randomly - Crosslinked PDMS. The polydimethylsiloxane (PDMS) used to make random networks was obtained from General Electric. Membrane osmometry showed to be 430,000 g/g-mole. The polymer was mixed with various amounts of a free-radical crosslinking agent, dicumylperoxide (Di-Cup R, Hercules Chemical Co.). Samples were then pressed into sheets and crosslinking was effected by heating for 2 h at 150°C in a heated press. Mc values were calculated using equation 2, and are included in Table I. 

A similar approach has been described by the same authors for the synthesis of related cyclic peptidomimetics [44]. A set often nucleophiles was employed for the substitution of the chlorine atom of the cyclic triazinyl-peptide bound to the cellulose membrane. By virtue of the aforementioned rate enhancement effects for nucleophilic substitution of the solid-supported monochlorotriazines, these reactions could be rapidly carried out by microwave heating. All products were obtained in high purity, enabling systematic modification of the molecular properties of the cyclic peptidomimetics. 

A membrane prepared by PVA blending with PAcr.Ac. in aqueous solution, casting, solvent evaporation and then crosslinking by heat treatment (at 150 °C), has been used. 

The last step in the construction of the MOSFET-heater model includes the description of an appropriate heating process. Due to the source-drain current flow, the membrane is heated by resistive Joule heating in the channel region. By assuming that all electric power dissipated in the device is converted into heat, the corresponding heating power is ... 

Diacetylenes like [30o] after being laboriously prepared, are not polymerized either by heat or ultraviolet irradiation (Iwamura, 1990). Control of molecular packing in crystals is now needed. Introduction of the technology of liquid crystals or Langmuir-Blodgett membranes (Hupfer et al., 1981 Koch and Ringsdorf, 1981) may be of help. 

The supernatant was first extracted with dichloromethane (2 x 3 L) to eliminate the remaining IMI. The aqueous fraction was then extracted with ethyl acetate (3 L). The ethyl acetate extract, containing 5-hydroxy IMI, wais dried with 30 g anhydrous sodium sulfate and concentrated to about l/20th of the original volume in a vacuum rotary evaporator and then filtered with 0.22 pm pore size ultrafiltration membranes. The filtered solution was evaporated again until white crystals were produced. The crystals were filtered, washed twice with dichloromethane and then dissolved in 10 mL acetonitrile by heating. At 4 °C, the 5-hydroxy IMI crystallized from the above solution and was filtered and dried under vacuum. A total of 413 mg of 5-hydroxy IMI was obtained. 

The Pt current collector was first used to deposit short ( 2 pm) Pt nanoposts [37,73] into the template membrane (Fig. 21A). These Pt nanoposts anchor the alumina membrane to the Pt surface and will serve to make electrical contact to the LiMu204 nanotubes. After Pt deposition, the pores in the membrane were filled with an aqueous solution that was 0.5 M in LiNOs and 1 M in Mn(N03)2 (Fig. 21B). The excess solution was wiped from the membrane surface, and the solvent (water) was removed by heating (50°C) in vacuum for 1 hour. The assembly was then heated at 500°C in air for 5 hours. This burns away the plastic tape and also causes tubules of LiMu204 to form within the pores (Figs. 21C, 22). 

Membranes with extremely small pores ( < 2.5 nm diameter) can be made by pyrolysis of polymeric precursors or by modification methods listed above. Molecular sieve carbon or silica membranes with pore diameters of 1 nm have been made by controlled pyrolysis of certain thermoset polymers (e.g. Koresh, Jacob and Soffer 1983) or silicone rubbers (Lee and Khang 1986), respectively. There is, however, very little information in the published literature. Molecular sieve dimensions can also be obtained by modifying the pore system of an already formed membrane structure. It has been claimed that zeolitic membranes can be prepared by reaction of alumina membranes with silica and alkali followed by hydrothermal treatment (Suzuki 1987). Very small pores are also obtained by hydrolysis of organometallic silicium compounds in alumina membranes followed by heat treatment (Uhlhom, Keizer and Burggraaf 1989). Finally, oxides or metals can be precipitated or adsorbed from solutions or by gas phase deposition within the pores of an already formed membrane to modify the chemical nature of the membrane or to decrease the effective pore size. In the last case a high concentration of the precipitated material in the pore system is necessary. The above-mentioned methods have been reported very recently (1987-1989) and the results are not yet substantiated very well. 

The shutdown property of separators is measured by measuring the impedance of a separator while the temperature is linearly increased. Figure 7 shows the actual measurement for Celgard 2325 membrane. The heating rate was around 60 °C/min, and the impedance was measured at 1 kHz. The rise in impedance corresponds to a collapse in pore structure due to melting of the separator. A 1000-fold increase in impedance is necessary for the separator to stop thermal runaway in the battery. The drop in impedance corresponds to opening of the separator due to coalescence of the polymer and/or to penetration of the separator by the electrodes this phenomenon is... 

Heat Treated PVA Membranes. The concept of independent water and salt transport through PVA Is further supported by the permeability properties of heat treated PVA membranes. It was found that by subjecting the PVA membranes to heat treatment, a sharp decrease of the water and salt permeabilities Is caused. The... 

---