Supports Teflon

Teflon support with its glass side facing the gas inlet the autoclave was evacuated (10 min, < 1 mbar), carefully filled with HCl gas (1 bar) and heated to 110°C for 15 min. After opening the autoclave the HCl vapors were blown out with a stream of cold air (5 min) and the HPTLC plate was cooled to room temperature. In order to intensify and stabilize the fluorescence the plate was dipped in a solution of liquid paraffin in chloroform (30 + 70) for 15 s. 

Foaming of Nafion. The interstices in the Teflon support lattice become discolored and develop pockmarks. This leads to zones of low mechanical stability from which pinholes may form, lead-... 

Figure 2 Beaker-type cell (a) double-walled cell (b) platinum sheet or grid on teflon support (c) electrode leads (steel rods) to d.c. power supply (d) thermometer (e) magnetic stirring bar (f) teflon stopper...

The effects of feed pressure on C02 flux and permeability, H2 flux, and C02/H2 selectivity were investigated using a membrane with a thickness of -60pm on the BHA microporous Teflon support. The feed pressures ranged from 1.5 to 2.8atm. Temperature was maintained at 110°C, and water rates were kept at 0.03cc/min for both the feed side and sweep side. The feed gas consisted of 20% C02,40% H2, and 40% N2 (on dry basis) with a feed gas rate of about 60cc/min in the gas permeation experiments. 

Grant No. 342-0561), and the Ohio State University. We would like to thank Chris Plotz and BHA Technologies, and Debbie de la Cruz and GE Infrastructure for giving us the BHA microporous Teflon support and GE E500A microporous polysulfone support, respectively, used in this work. 

The potential of grafted polymers remained unrecognized until the use of PS-PTFE support was resurrected in the 1990s under the phosphoramidite method [168]. The aminomethylated and loaded with nucleoside 3 -succinate from 12.5 to 48pmol per g-PS-Teflon support has been employed successfully in the automated synthesis of oligodeoxyribonucleotides as long 143-mer, with stepwise efficiency of up to 99.8%, comparing favorably with such popular carriers as silica beads CPG-500 and macroporous polystyrene Primer Support (Pharmacia). 

Figure 1. DSC sample head with LEDs mounted in Teflon support block.

The role of the RC (resistive-capacitative) characteristics of the inert support elements in the thin film can be appreciated by the following experiment. Similar oriented BR thin films were deposited on Teflon films of various thicknesses (6.35, 12.7, 25.4 /zm). The relaxation time course varies with the thickness of the Teflon support, but the effect is predictable by the equivalent circuit. Figure 10.3(C) shows that the time course for the thin films of 12.7 and 25.4 fj.m thickness can be predicted by the equivalent-circuit analysis based solely on data obtained at the 6.35 /U,m thin film [10]. As expected, deconvolution of either the... 

Figure 14 Isothermal displacement calorimeter with cooling module. A, stainless-steel support tube, B, vent tube C, current and potential leads for heater D, connector for feed tube E, Teflon plug F, vent plug G, heateriwire supports H, baffles I, Teflon support ], heater wires K, stirrer magnet L, stirrer paddle A,feed tube N, thermistor P, Teflon feed cup Q, water inlet tube R, copper heat sink S, 5Q era precision-bore Dewar flask T, 0-rings U, coin-silver cooling rod V, copper cup W, coin-silver support rods X, copper heat shield Y, coin-silver bar Z, cooling module (Reproduced by permission from J. them, and Eng. Data, 1966, 11, 189)...

Traditionally, products and adsorbates had to be volatile enough so that they could be carried from the cell into the mass spectrometer, either by headspace sampling, or, more commonly for near-simultaneous analysis (referred to as differential electrochemical mass spectrometry), across a nanoporous, gas-permeable membrane (e.g., Teflon) supported at the tip of a microcapillary placed close to the electrode. Alternatively, a Pt-coated membrane electrode can be used. But the advent of the so-called soft atmospheric pressure desorption/ionization techniques associated with liquid chromatography-mass spectrometry has allowed the sampling of the solvent and involatile solutes directly. The spectra are more... 

Fifteen trace elements were determined at ng/g mass fraction levels in high purity Sn by Kolotov et al. (1996) using extraction chromatography on Teflon-supported tributylphosphate (TBP). Tin, together with Sb and In radionuclides, which are formed in secondary nuclear reactions of Sn during irradiation, were retained from 6 M HCl on the column. The Na was removed from the eluted trace element fraction by sorption on hydrated antimony pentoxide (HAP). Gas phase impurities of N, C, and O were also analyzed in the same material by radiochemical photon activation analysis via N, C, and detection. 

Fig. 6.1. Photograph of an air-tight sampie chamber for making reflected iight microscopy measurements on freeze-dried ceiis on a siiicon substrate. A siiicon chip containing the cells is isolated from the normal atmosphere by a glass coverslip which is glued to a Teflon support. Reproduced from ref. (30).

Once the reaction is successful, the elastomer strip is loosened from the centrifuge wall with the non-cutting side of a thin lancet. The elastomer film is carefully removed from the cell together with the Teflon support and cut into smaller (usually two or three) pieces. For cutting the swollen polymer gel the best method is to use a carpet knife and a hammer. That way, a clean cut of both the gel and the Teflon band is achieved. It is useful, especially if working with sticky side chain elastomers, to keep some toluene at the preparation table to clean the tools before reuse. If possible, both long rims of the film should also be cut with a carpet knife, because small defects at the rim can... 

In order to remove the cast elastomer film from the Teflon support, a strip of Kapton based adhesive tape is fixed at one end of the swollen gel. Kapton is used as it can withstand high temperatures and is stable towards organic solvents. The film is now removed from the support by slowly pulUng the tape. In some cases it is useful to rinse the space between the elastomer film and the Teflon foil with toluene. The elastomer film is fixed at a metal holder and hung vertically. At the lower end of the film a small load, e.g., a paper chp, is attached and held steady with Kapton tape from both sides (Fig. 10). 

In vitro and in vivo degradation studies were performed with polymer samples in film or tube form. Polymer films were either cast from methylene chloride solution or compression molded with thicknesses between 100-300 ym. Polymer tubes from poly(caprolactone) and caprolactone copolymers were made by tightly wrapping several layers of a polymer film around a Teflon support (tubes with O.D. of 1.2 mm). The package was then heated under rotation in vacuum until a polymer tube of even wall thickness (150-600 pm) was formed. Before use the tubes were heat-sealed on both ends. 

Pappas and Million have described a gas chromatographic technique for the examination of mixtures of corrosive fluorides such as boron-, tri- and pentafluoride, free chlorine, chloryl fluoride, dichlorotetrafluoroethane, hydrofluoric acid and uranium hexafluoride. These workers used columns constructed of Teflon packed with a Teflon support and using either Kel-F or fluorocarbon oil as liquid phase. The technique was applied to halocarbon coolant analysis and in uranium fuel recovery. 

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