PTFE liners

Fig. 9 The SPOS-compatible reaction vessel for the Synthos 3000. Depicted from left to right is the filtration imit, the PTFE liner (white), the pressure jacket, and a fully assembled vessel with a ceramic pressure jacket...

An important element in assuring the collected sample representativeness is the use of sample containers that sustain sample integrity. We collect water samples for VOC analysis in 40-ml VOA vials with screw-on PTFE-lined silicon rubber septum caps. The PTFE liner of the septum should always face down to contact the water. Water samples for SVOC analyses are collected into 1-liter amber glass bottles with PTFE-lined lids. Samples for metal and inorganic parameter analysis are placed either into high-density polyethylene (HDPE) or glass bottles. 

Isostatic cycle times as short as 12 seconds are possible for small simple parts. The length of the cycle increases with the complexity and size of the article. In such instances, this technique is often the only available method for the fabrication of those parts. An example is in situ formation of a PTFE liner inside a fitting such as a T-piece. 

An inspection of the failed hose clearly demonstrated that the sulphur trioxide had permeated through the PTFE liner and corroded large portions of the stainless steel liner. As a consequence, the weight of a valve that was attached to the end of the hose was partly supported by the PTFE liner itself. In addition to this axial load, the liner was also exposed to an internal pressure. A schematic representation of the applied loads acting on the liner is shown in Fig. 11.8. 

A comparison of the predicted stresses from the FE analysis with the experimentally determined strength of the PTFE liner showed that the failure of the liner was to be expected. Even if the temperature of the liner was 20°C, the combination of internal pressure and axial load could have caused the axial split in the PTFE liner that was observed. 

Acid-resistant brick (with furan-type acid mortar and mastic w/PTFE liner) 3Vi inches 45-60 —... 

Amines, either as salts or the free bases, can be formy-lated using sodium formate the base (or its salt, 1-5 mg) is treated with 98-100% formic acid (20 fxl), anhydrous sodium formate (10 mg) and acetic anhydride (200 rl) at 25 °C for 30 minutes in a reaction vial sealed with a cap containing a PTFE liner. Excess reagents are removed... 

Pesticides Organochlorine O rganophosphoms Polyaromafic hydrocarbons Polychlorinated biphenyls Add 200 ml of hexane per 41 ample (in a 4.51 amber glass bottle), shake well and deliver to the laboratory as soon as possible. Place a piece of aluminum foil over the mouth of the bottle before screwing on the cover (except when there are PTFE liners in the cap). 

Valves Caustic System Alloy 20, Durimet 20, or ductile Fe plug valves with PTFE liners... 

Different resins have been developed for use in different reduction—ratio appHcation ranges (111,112). The powders suitable for high reduction—ratio appHcations, such as wire coatings, are not necessarily suitable for the medium reduction—ratio appHcations, such as tubings, or the low reduction—ratio appHcations, such as thread-sealant tapes or pipe liners. AppHcations and processing techniques are being used, which utilize the unique combination of properties offered by PTFE in fine powder form (113—115). 

Figure 12-8A. Piston rings. The piston rod is manufactured from heat-treated stainless steel and is coated with wear-resistant overlays, such as ceramic, chromium oxide, and tungsten carbide applied by plasma techniques. Piston rod cross-head attachment has mechanical preloading system for the threads. Rider rings and seal rings are manufactured from PTFE filled resins fillers are matched to the gas, piston speed, and liner specifications. Typical fillers are glass, carbon, coke, or ceramic. (Used by permission Bui. BCNA-3P100. Howden Process Compressors Incorporated. All rights reserved.)...

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. 

For the individual rotor types, different vessels are available. The 16-vessel rotor, dedicated for the performance of standard reactions at up to 240 °C, offers 100 mL PTFE-TFM liners. Applying different pressure jackets allows continuous operation of these vessels to a maximum of 20 or 40 bar, respectively. The 8-vessel rotor is designed for high-pressure reactions, offering PTFE-TFM liners or quartz vessels, which enable reactions to be performed at 300 °C and 80 bar for several hours. 

Liner material PTFE-TFM PTFE-TFM PTFE-TFM quartz... 

Aqueous trip blanks sometimes accompany soil samples collected into metal liners or glass jars. In this capacity they do not provide any meaningful information. Soil samples do not have the same contamination pathway as water samples because they are not collected in 40-milliliter (ml) VOA vials with PTFE-lined septum caps. In addition, soil does not have the same VOC transport mechanism as water does (adsorption in soil versus dissolution in water). There are other differences that do not permit this comparison different sample handling in the laboratory different analytical techniques used for soil and water analysis and the differences in soil and water MDLs. That is why the comparison of low-level VOC concentrations in water to VOC concentrations in soil is never conclusive. 

Soil samples for VOC analysis are collected into airtight coring devices or into preserved VOA vials. Soil samples for SVOC, metal, and inorganic parameter analyses are collected into brass or stainless steel core barrel liners, acrylic liners, or into glass jars with PTFE-lined lids. The liners are capped with PTFE sheets and plastic caps. 

Sampling of subsurface soil into core barrel liners has been widely used until EPA Method 5035 came into effect. In this sampling method, after a core barrel liner has been filled with soil, it is capped with PTFE sheets or aluminum foil and plastic caps. These types of closure do not prevent the VOC loss from soil, which for some compounds may exceed 97 percent after only 6 days of cold storage (Hewitt, 1999). If sampling and storage in glass jars or core barrel liners cannot be avoided, samples must be delivered to the laboratory and analyzed within the shortest time after collection. 

If sampling for VOC is required, use an airtight coring device and quickly collect samples from the ends of the middle liner. Cap the lower liner with PTFE sheets and plastic caps, label it, and place on ice. 

The hydrogenation reactions were carried out in a 100-ml stainless-steel autoclave equipped with a 50-ml glass liner and PTFE cover to provide clean conditions. The reactor was magnetically stirred (n = 1000 min 1). The pressure was held at a constant value by a computerized constant volume - constant pressure equipment (Buchi BPC 9901). By monitoring the pressure inside the vessel and the injected pulses, the hydrogen uptake could be followed. Under standard conditions, 42 2 mg prereduced catalyst, 1.84 mmol substrate, 6.8 imol modifier and 5 ml solvent were used at 10 bar and room temperature. 

Because of its elastic recovery properties, PTFE, a self-lubricating compound, is used in sealing and flexing applications such as sanitary seals, valve diaphragms, o-rings in mechanical seals, and seals and seats of stem and rotary valves such as ball valves. It is also commonly used as a liner or coating material for valves and pumps for the pharmaceutical industry. 

Loose lining FEP PFA Modified PTFE All 60, 90, 125, 187 mils Liner fabricated outside the housing and slipped inside Liner fabricated by hand and machine welding Shop only No vacuum. Pressure OK Determined by body flange (12) and section height (12) Visual Spark Difficult... 

Another method used to weld the liner of large tanks is hot gas welding using a PFA (melt-proces-sible) rod. Sheets of skived polytetrafluoroethylene are joined together by welding to lined chemical storage tanks. PTFE is heated at the seam by hot air until it is in a gel state. Simultaneously, a PFA rod is molten and used to fill the seam. 

PFA tubes and pipe liners can be butt-welded in a similar procedure to that used for PTFE (Sec. 7.4.2). PFA does not require adhesive to form a bond. PFA is easily welded by a heated platen technique in which the liner ends contact the heated plate until a bead is formed. A heater plate temperature of 399°C, a contact time of 15-30 secs, and a soak time of 90-105 secs are required for liners with a diameter of 2.5-... 

Fabricate a liner, insert it in the steel piping and flare the ends over the flange. PTFE and PVDF account for most pipe below 12" in diameter. For pipe sizes above 14" (35 cm), the pipe is lined as a loose lining using FEP, PFA, or modified PTFE... 

PVDF, ETFE, and PFA liners are made by simple extrusion and inserted in the metallic housing, similar to PTFE. 

---