PTFE washers

The closure must effectively and safely seal the container, while remaining inert with respect to the contents. Inertness is often achieved by using a polytetraflu-oroethylene (PTFE) washer on the inside of the closure. In some applications, some form of additional seal, double-containment may be used because the contents of the container are either dangerous or proof is required that the container has not been tampered with and/or the contents disturbed (for example, forensic samples). 

The useful screw-thread connector is becoming widely available. The simplest is the screw-capped adapter (Fig. 2.32) where the screw-capped joint is associated with a ground glass cone. The figure shows the silicone rubber ring and PTFE washer, and the adapter is useful for the insertion of gas tubes, thermometers or stirrer shafts. The screw-thread connection principle has been applied to the connection of water hoses to condensers and vacuum lines to Buchner flasks, to securing simple sealing septa to flasks, etc. 

Figure 32 Schematic of cross section of arrangement used with knife-edge PTFE washer for definition of sample area. A represents the PTFE washer, B represents the sample, C represents the assembly, including the backing plate that generally is screwed against the sample to press it against the PTFE washer, and D represents the insulated electrical contact.

Figure 123. The state that the reference cell, on which two PTFE washers and a stainless steel washer are put, has been pressed eoneentrically and firmly up to the under surface of the stainless steel jig in by raising the laboratory jack, a. Cramp of rhe srand b. Srainless steel jig HI, 75 mm in length c. Stainless steel washer, 1 mm in thiekness d. Two PITT washers, 0.3 mm each in thickness e. Glass capillary flange f, 0-ring g. Closed cell h. Silica powder i. Female cap nut j. Two PTFE washers, 0.3 mm each in thickness k. Stainless steel washer, 1 mm in thickness 1. Stainless steel jig H m. Pedestal.

The second stainless steel jig, the stainless steel jig II, the inside diameter of the lower end of which is 16.1 mm, is set anew on the pedestal. The female cap nut, on the bottom of which a stainless steel washer and two PTFE washers are put in this order, is then set in the stainless steel jig II. The outside diameter of the female cap nut is 22 mm, and, the inside diameter of the upper end and that of the flange of the stainless steel jig II are 22.2 mm and 14.2 mm, respectively. Thereafter, the reference cell is inserted into the composite of the female cap nut and the stainless steel jig II. Two PTFE washers and a stainless steel washer are then put concentrically in this order on the upper surface of the glass capillary flange (see d and c in Fig. 123). 

The reference cell, on the upper surface of the flange of which two PTFE washers and a stainless steel washer are put, is then pressed concentrically and firmly up to the under surface of the stainless steel jig M by raising the laboratory jack (Fig. 123). ... 

In the specimens with the larger siuface area, a hole is drilled. The galvanic couples and the imcoupled reference specimens are moimted in duplicate on wooden planks by means of an insulated bolt passing through the hole. PTFE washers insulate the test specimens fix>m the plank and the bolt head. 

Zirconium U-bend specimens were tested in boiling, concentrated NaOH at TWC. During the test period, the concentration changed from 50% to about 85%, and temperature increased from 150 to 300°C. The PTFE washers and tubes used to make the U bends dissolved. However, the zirconium U bends remained ductile and did not show any cracks after 20 days. It should be noted that stainless steel is susceptible to SCC in alkaline solutions, including NaOH solutions. 

Note Artificial crevice produced by a flat PTFE washer clamped to the titanium surface with a Beta C nut and bolt arrangement. The ratio of crevice to uncreviced area was approximately 1 to 10. Source D.E. Thomas, S. Ankem, W.D. Gioodin, and S.R. Seagle, in Industrial Applications of Titanium and Zirconium Fourth Volume, C.S. Young and J.C Durham, Ed., ASTM STP 917, ASTM, 1986... 

The flow cell was designed to make optimum use of the cavity and to monitor the temperature of the flow cell directly using an inbuilt IR sensor. To this end, a standard pressure rated glass tube (10 luL) is fitted with a custom built steel head and it was filled with sand (10 g) between two drilled porous frits. This is to minimize dispersion and effectively create a lattice of microchannels. It is charged with solvent (5 mL volume), sealed using polytetrafiuoroethylene (PTFE) washers and connected to an HPLC flow system with a backpressure regulator. 

Figure 6. Drawing of fitting used for connection between PVDF tube and end-block 1, PTFE sealing cone 2, neoprene rubber O-ring 3, PVDF washer 4, PVDF retaining cone 5, nut...

Fig. 33) in which a cylinder of PTFE is forced onto the top of a generally cylindrical sample. The Stern-Makrides washer suffers from same problems as does the knife-edge, but to a greater degree due to the larger surface area involved. 

Fig. 4. High-pressure/high-temperature cavity for in-situ EPR measurements (1) pressure vessel body (2) pressure vessel lid (3) nut (4) thrust washer (5) cavity top (6) cavity (7) high-pressure gas fitting (8) PTFE tuning wedge (9) tapered waveguide (10) water jacket (11) Lucalox plug (12) heater lead feedthrough (13) modulation coil feedthrough (14) thermocouple feedthrough and (15) heater assembly. Reprinted from Reference 44).

Valves for both cylinders and drums may be composed of a "Monel metal spindle, PTFE gland packing and lead outlet-washer on the cover nut. 

PA/PTFE low coefficient of friction and high temperature resistance (used with glass reinforcement). Used in mechanical parts like bearings, bushings, thrust washers, also constraction hardware like door latches. 

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