Polytetrafluoroethylene pumps

Aqueous hydrogen fluoride of greater than 60% maybe handled in steel up to 38°C, provided velocities are kept low (<0.3 m/s) and iron pickup in the process stream is acceptable. Otherwise, mbber or polytetrafluoroethylene (PTFE) linings are used. For all appHcations, PTFE or PTEE-lined materials are suitable up to the maximum use temperature of 200°C. PTEE is also the material of choice for gasketing. AHoy 20 or Monel is typically used for valve and pump appHcations. Materials unacceptable for use in HE include cast iron, type 400 stainless steel, hardened steels, titanium, glass, and siHcate ceramics. 

Perfluoroalkyl ether greases thickened with polytetrafluoroethylene (MIL-G-38220 and MIL-G-27617) are used from —40 to 200°C in missiles, aircraft, and appHcations where fuel, oil, and Hquid oxygen resistance is needed (55). Polyphenyl ether greases find special use from 10 to 315°C in high vacuum diffusion pumps and for radiation resistance. 

Aznarez et al. [2] have described a Spectrophotometric method using curcumin as chromopore for the determination of boron in soil. Boron is extracted from the soil into methyl isobutyl ketone with 2-methylpentane-2,4-diol. In this method 0.2-lg of finely ground soil is digested with 5ml concentrated nitric-perchloric acid (3 + 1) in a polytetrafluoroethylene lined pressure pump for 2h at 150°C. The filtrate is neutralized with 6M sodium hydroxide and diluted to 100ml with hydrochloric acid 1+l.This solution is triple extracted with 10ml of methyl isobutyl ketone to remove iron interference. This solution is then extracted with 10ml 2-methyl pentane-2,4 diol and this extract dried over anhydrous sodium sulphate. 

The microreactor system used was the commercial CYTOS College System [18]. The reactor is made of stainless steel, has 100 ptm channels and 2 ml volume. It has two inlets operated by two piston pumps. An additional 45 ml residence time unit (RTU) is coimected to the system after the reactor itself to increase the reaction time. The parts of the device are comiected by polytetrafluoroethylene (PTFE) tubings. 

Figure 3.3 Classification of pumps according to material of construction. PEEK, Polyethy-lethylketone Teflon, polytetrafluoroethylene.

There are some special cases for which it is unnecessary to add a lubricant. Magnetic bearings and bearings that are suspended by a pressurized gas have no metal-to-metal contact so that wear and heat buildup are avoided. Several companies sell oil-free vacuum pumps that eliminate the trouble and expense of changing the oil, disposal costs, and contamination of process chambers, which is especially important in the manufacture of semiconductors and liquid crystal crystal displays.40 Plastic gears of nylon or polytetrafluoroethylene are self-lubricating and need no added lubricant. They reduce the noise associated with ma-... 

Ryton Polyphenylene Sulfide is a new commercial plastic which is characterized by good thermal stability, retention of mechanical properties at elevated temperatures, excellent chemical resistance, a high level of mechanical properties, and an affinity for a variety of fillers. It is produced from sodium sulfide and dichlorobenzene. Its unusual combination of properties suggests applications in a variety of molded parts such as non-lubricated bearings, seals, pistons, impellers, pump vanes, and electronic components. Tough coatings of polyphenylene sulfide can be applied to metals or ceramics by a variety of techniques and are used as protective, corrosion-resistant coatings in the chemical and petroleum industries. Incorporation of small amounts of polytetrafluoroethylene provides excellent non-stick properties in both cookware and industrial applications. 

Polytetrafluoroethylene (PIPE, Teflon) Resistant, smooth solid Heart pumps, reinforcement of artery and blood vessels ... 

MS, which requires vacuum. This membrane needs to be impermeable to the liquid electrolyte, yet permit the transport of the generated gases [79]. In the case of polar solvents such as those in Li-based batteries, polytetrafluoroethylene (PTFE) is the most popular choice [80]. Typically, differential pumping systems are used to progressively approach the vacuum required by the MS. An extensive discussion of the specific modifications that enable different types of electrochemical experiments and the corresponding analytical sensitivities can be found in the literature [79]. 

The most serviceable material for centrifugal hypochlorite pumps is titanium. The major deterrent to its use is its cost. Other pump materials may be lined with fluoropoly-mers (PTFE, ETFE). Diaphragm pumps usually have polytetrafluoroethylene (PTFE) or elastomer (preferably Viton) diaphragms. FRP pumps are generally not used. 

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