Teflon gaskets

Gasket — Teflon envelope with EPDM insert, steam resistant, inside diameters as specified for tubing... 

Tetrafluoroethene F2C = CF2 (-CF2-CF2-) (Teflon) Nonstick coating for cooking utensils bearings gaskets and fittings... 

DMAC is a good solvent for many resins therefore, flange gaskets and pump and valve packing should be limited to Teflon fluorocarbon resins. 

Eig. 19. CME monopolar electrolyzer a, membrane b, cathode element c, half-cathode element d, current distributor e. Teflon tube f, CI2 + depleted brine manifold g, conductor rod h, CI2 + depleted brine outlet nozzle i, base frame j, recycled NaOH manifold k, recycled NaOH inlet nozzle 1, gasket (the gasket-to-element ratio is quite small) m, tie rod n, anode element o, H2 + NaOH manifold p, end plate, q, under cell bus bar (simplifies piping... 

Thiols iateract readily with many mbber-containing materials. For this reason, care should be taken ia the selection of gasket and hose materials. Teflon, Kel-F, Viton, or other suitable fluoroelastomers function as gasket materials. Viton is suitable for hoses. Carbon steel is useful for many thiols, although some thiols become very discolored when carbon steel is utilized. In these cases, the use of stainless steel is very desirable. Isolation from air and water also minimizes color formation. 2-Mercaptoethanol and 1,2-ethanedithiol should be stored ia stainless steel (61). 

SmaH quantities of carbon tetrachloride can be shipped in 1, 5, and 55 gaHon (208 L) metal containers. Larger quantities are shipped by tank tmck, tank car, barge, and ship. Seamless stainless steel. Teflon, or seamless bronze hose is recommended with asbestos. Teflon, Viton, or neoprene gaskets. Special precautions should be taken to prevent contact with aluminum, magnesium metal, and their aHoys (48). 

Figure 9.7 Schematic illustration of the flow-gating interface. A channeled Teflon gasket was sandwiched between two stainless steel plates to allow for flow into the electrophoresis capillary, either from the flush buffer reservoir or from the LC microcolumn during an electiokinetic injection.

Solid nonabsorbent gaskets such as Teflon should be used when necessary. 

Tetrafluoroethylene Teflon Gaskets, insulation, bearings, pan coatings... 

PTFE, known under the trade names Teflon and Fluon, is resistant to all chemicals, except molten alkalies and fluorine, and can be used at temperatures up to 250°C. It is a relatively weak material, but its mechanical strength can be improved by the addition of fillers (glass and carbon fibres). It is expensive and difficult to fabricate. PTFE is used extensively for gaskets and gland packings. As a coating, it is used to confer non-stick properties to surfaces, such as filter plates. It can also be used as a liner for vessels. 

Tests showed that Teflon gaskets containing more than 0.35 wt% of sorbed trichloroethylene were potentially hazardous in contact with liquid fluorine. 

Figure 2 Schematic diagram of a 100-mL UV-autoclave. a = gas and sampling valve, b = thermocouple, c = quartz window, d = Teflon O-rings, e = autoclave lid, f = rupture disc, g = valve and pressure gauge, h gaskets, i = autoclave body, k = glass insert, 1 = temperature control, m stirring bar. (Pmax 300 bar, Tmax = 150 °C) (Reproduced with permission from Ref. 7. Copyright 1983 Elsevier Sequoia.)...

Chemically universally stabile is poly-tetrafluoroethylene (PTFE, Teflon ), but it is relatively expensive. A problem is the cold flow , that is, the polymer is slowly deformed under the mechanical stress of the pressure on the gaskets and a leakage of the cell can occur (PTFE compounds, e.g. with glass powder or graphite, show a better behavior.)... 

Teflon is manufaetured by heating tetrafluoroethene with a free radical or persulphate catalyst at high pressures. It Is ehemleally inert and resistant to attack by corrosive reagents. It Is used in making oil seals and gaskets and also used for non - stick surface coated utensils. 

The next stage of development went to polymer chemists and development engineers, as the expertise of Roy Plunkett was really in fluorine chemistry. The first great application was in the separation of the isotope U-235 from U-238 by gaseous diffusion of UFe to make atomic bombs, as the gas uranium hexafluoride was exceedingly corrosive and destroyed conventional gaskets and seals. PTFE was just what was needed to form the diffusion membrane, as it was not attacked by fluorine. When peace returned, PTFE registered the trademark of Teflon in 1944. 

Figure 4.12 — (A) Flow-cell for the simultaneous determination of four analytes (1) ion-selective electrodes (2) reference electrode (3) Pt wire for grounding (4) Teflon gasket (5) carrier (6) inlet for reference solution (7) waste (8) screws (9) diecast box (10) rubber sheet for sealing. (B) Seven-electrode holder (the reference electrode is placed from the top into die central bore). ISEs for Na, K, Ca ", NOj", Cr, and HCO, (NH, electrode with internal buffer of 0.1 mmol/L NaHCOj) are placed horizontally around the reference electrode, the metal waste tubes being connected to the waste via filter-paper strips. (Reproduced from [124] and [108] with permission of Elsevier Science Publishers and VCH Publishers, respectively).

Of particular interest are quantitative syntheses of extremely deliquescent and reactive alkyliminium salts by milling of solid imines with oxonium salts (178), triphenylmethylium tetrafluoroborate (180), or triphenylmethyl chloride (183) (dry atmosphere in these cases). The sensitive salts 179, 181, and 184 are formed in pure form without any waste by an easy experimental technique [10]. Precisely weighed samples of 178 (ca. 2 mmol), 180 (ca. 1 mmol), or 183 (1.00 mmol) were placed in a ball-mill under argon together with the precise equivalent of 54a,f,g, or 54f, or 182, respectively. The Teflon gasket was closed... 

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