Polytetrafluroethylene 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. 

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The evaluation of combustion performance and safety of Mg/polytetrafluroethylene (PTFE) pyrotechnic compositions by means of TG-DTA has been reported by Miyake and co-workers [83]. Similar work on different pyrotechnic systems containing a chlorinated rubber binder has made use of TG-DSC and TG-DTA-MS [59-62], The hyphenated technique TG-DTA (DSC) has recently been reviewed [56]. 

Courtaulds developed many products [153] based on carbon fibers prepreg as warp sheet and tape, random fiber mats, preferred orientation mats, chopped fiber, thermoset and thermoplastic molding compounds and polytetrafluroethylene (PTFE) impregnated tow. Oxidized PAN fiber was available as continuous tow, tops, yarns, woven and knitted fabrics. 

The frictional and wear properties of the polymers used for gears can be greatly enhanced by the addition of internal lubricants. The most commonly used additives are polytetrafluroethylene, PTFE (Teflon, Fluon) silicone fluids graphite molybdenum sulphide, M0S2. PTFE, with its exceptionally low coefficient of friction is very effective as an internal lubricant. Initial shear causes it to form a high-lubricity film over the surface. It is, of course, expensive, and will generally reduce the mechanical properties of the material. 

There are two types of plastics, thermoplastics and thermosetting polymers. Thermoplastics are the plastics that do not undergo chemical change in their composition when heated and can be molded again and again, examples are polyethylene, polystyrene, polyvinyl polystyrene, polyvinyl chloride, and polytetrafluroethylene (PTFE). The raw materials needed to make most plastics come from petroleum and natural gas. 

In marked contrast to AVFs, AVGs do not have a problem with early maturation failure, with the vast majority being cannulated between 3-6 weeks after surgery. Unfortunately, they do have significant problems with stenosis (most commonly at the graft-vein anastomosis) and thrombosis, with a recorded one year unassisted primary patency as low as 23% [9]. In addition, polytetrafluroethylene (PTFE) grafts have an infection rate of approximately 10% over the lifetime of the graft. 

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