Polytetrafluoroethylene or Teflon

Teflon tends to flow under pressure and is thus readily distorted. When filled with glass, the composite is stabilized and can be machined to precise dimensions. 

Teflon cannot be injection molded because of the high viscosity of the melt and must therefore be formed by a compression of its powders. Another fluorinated polymer of comparable properties to 

Teflon is a blend of PTFE and polyhexafluoropropylene (FEP) made by polymerization of perfluor-opropylene (C3F6). This plastic is not as thermally stable as Teflon (M.P.=290°C), but it is less opaque than Teflon and can be extruded, injection molded, or blow molded and thus presents some advantage over Teflon in particular applications. 

A Teflon-like surface is made when polyethylene bottles are blown with nitrogen containing about 1% F2. This makes the bottles less permeable to organic solvents and thus increases its usefulness. 

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Researchers are now seeking practical ways to fluorinate the surfaces of diamond films, as the resulting surfaces are expected to have very low coefficients of friction (cf. non stick polytetrafluoroethylene or Teflon, Section 12.3) and hence have applications in low-friction tools. Direct flu-orination with elemental fluorine is impractical, but photodecomposition of fluoroalkyl iodides chemically absorbed on the diamond surface looks promising.4... 

Steel [52013-36-2] suture is made from 316-L stainless steel wire. The suture may be monofilament, known as fixation wire, or multifilament twisted wires. The steel is heat-treated to improve ductility. The multifilament strands are either uncoated, or coated with Teflon (polytetrafluoroethylene) or Teflon-fluorinated ethylene—propylene copolymer. 

The reaction between hydrogen and oxygen produces water. The latter covers the surface of the catalyst and thus retards the reaction of water recombination. To avoid the formation of a water film on the catalyst surface, the catalyst carrier is treated with a hydrophobic substance, e.g. PTFE (polytetrafluoroethylene or teflon). The condensed water runs down draining paths back into the cell. The plug may be fitted with a stopper as well to prevent the H2SO4 electroljrte to get into the plug and to deactivate the catalyst. 

PTFE polytetrafluoroethylene or Teflon, metric, LOD limit of detection Source Reprinted with permission from... 

Use a heat resistant packing made of Teflon (polytetrafluoroethylene) or fluoro rubber. 

Polytetrafluoroethylene (PTFE, or Teflon) is reported to resist friction welding to other polymers even at high speeds and pressures [24]. PTFE has a much lower coefficient of friction and relatively higher softening point among the polymers. To reach the necessary conditions to weld it, sliding speed and pressure should be increased by a factor of 50 and 20 in comparison with high-density polyethylene [19]. 

Environmental samples from munitions or swabs from environmental materials should be placed in sealed glass or Teflon (polytetrafluoroethylene, manufactured by Du Pont Polymers, Wilmington, Delaware) containers, and kept dry and as cold as possible. Caution Handling a dry or powdered toxin can be very dangerous because the toxin may adhere to skin and clothing and could be inhaled. 

In 1938, Plunkett of Du Pont, discovered polytetrafluoroethylene (ptfe), or Teflon as it is commonly known. 

A major area of concern in chemical processes is the use of volatile organic compounds as solvents for reactions. The solvent is not generally consumed in the reaction, but there are unavoidable releases to the atmosphere even in the most carefully controlled processes. Further, the solvent may be toxic or may decompose at least to some extent during reaction, thus creating wastes. The use of supercritical fluids ("Chemistry at Work" box. Section 11.4) represents a way to replace the conventional solvent by CO2, a nontoxic gas already present in the atmosphere that can be recycled. Du Pont chemical company, for example, has invested in a production facility to make polytetrafluoroethylene, — [CF2Cp2] — (Teflon M) and copolymers with tetrafluoroethylene in liquid or supercritical CO2. In this case the CO2 replaces chlorofluorocarbon solvents, which, aside from their costs, have harmful effects on Earth s ozone layer (Section 18.3). 

A variety of low-dielectric, low-loss resin systems are available for high-speed circuit apph-cations. These include polytetrafluoroethylene (FTFE or Teflon ), cyanate ester, epoxy blends, and allylated polyphenylene ether (APPE). Likewise, a few different reinforcements and fillers are available that can be used to modify the electrical properties of the base material. Although E-glass is stm the most commonly used fiberglass reinforcement, it should be noted that others are available. In addition, inorganic fillers are sometimes used to modify electrical properties as well. Table 9.6 provides electrical property data on some of the available fiberglass materials. Table 9.7 provides data on some of the base material composites available. 

The use of polytetrafluoroethylene or PTFE for printed wiring substrate fabrication is a relatively well-established practice brought about by the need for improved high-frequency materials. The critical properties in this field of application are a low dissipation factor, a uniform dielectric constant which exhibits little variation with frequency over a wide bandwidth up to 15 GHz, combined with environmental and temperature stabilities. These properties can be achieved in a number of teflon/glass or teflon/glass/ceramic composites based on both fabrics and random glass. The dissipation factor at 1 MHz is more than 100 times less than a typical epoxy FR4, as shown in Table 9.4. 

In 1938 yet another serendipitous observation led to the discovery of polytetrafluoroethylene, PTFE or Teflon, as it became known. In this polymer atoms of fluorine replace the hydrogen... 

Fourth, because hardcoat is a naturally porous substance, it is used in many areas in which the bonding or impregnation of other materials to aluminum is needed. This coating bonds very well with paints and adhesives. Also, it can be impregnated with teflon (polytetrafluoroethylene, or PTFE) and many dry film lubricants to impart lubricating properties to the coating. 

Membrane degasification units generally use hydrophobic hollow-fiber polypropylene or polytetrafluoroethylene (PTFE) (Teflon) microporous membrane (Wiesler, 1996). Hollow-fiber modules are made by potting the desired number of fibers into an external shell. The potting compound may be polyurethane, epoxy, polyolefin, or fluorinated polymers. Since the membranes are hydrophobic and have small pores (Fig. 13.15), water will not easily pass through the pores. 

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