Teflon® PTFE

Carbon steel Sch. 40 Fiberglass reinforced polyester Fiberglass reinforced vinylester Glass pipe Aluminum Sch. 40 304 stainless steel Sch. 5 Saran-lined steel Polypropylene- lined steel Rubber-linedsteel Sch. 40 316 stainless steel Sch. 5 304 stainless steel Sch. 40 Kynar-Ifned steel 316 stainless steel Sch. 40 Alloy 20 Sch. 5 FEP Teflon-lined steel PFA Teflon-lined steel Armored-glass pipe PTFE Teflon-lined steel Monel 400 Sch. 5 Nickel 200 Sch. 5 Alloy 20 Sch. 40 Monel 400 Sch. 40 Inconel 600 Sch. 5 Titanium Sch. 5 Nickel 200 Sch. 40 Titanium Sch. 40 Inconel 600 Sch. 40 Glass-lined steel Sch. 40 Hastelloy C-276 Sch. 5 Zirconium Sch. 5 Hastelloy B Sch. 5 Zirconium Sch. 40 Hastelloy C-276 Sch. 40 Hastelloy B Sch. 40 Tantalum-lined steel Sch. 5 Tantalum-lined steel Sch. 40... 

This is a standard friction problem. A glance at Fig. 25.5 shows that, when polymers slide on metals and ceramics, x can be as low as 0.04. Among the polymers with the lowest coefficients are PTFE (Teflon ) and polyethylene. By coating the ski or sledge runners with these materials, the coefficient of friction stays low, even when the temperature is so low that frictional heating is unable to produce a boundary layer of water. Aircraft and sports skis now have polyethylene or Teflon undersurfaces the Olympic Committee has banned their use on bob-sleds, which already, some think, go fast enough. 

Polymers such as PVC and PTFE ( Teflon ) are very stable. Use the bond enthalpy values E(C-C1) = +346kJmor and E(C-F) = + 480kjmor to explain this fact. (2)... 

Antidripping PTFE Teflon 60 Hostaflon 9202 DuPont Hoechst... 

Chemically universally stabile is poly-tetrafluoroethylene (PTFE, Teflon ), but it is relatively expensive. A problem is the cold flow , that is, the polymer is slowly deformed under the mechanical stress of the pressure on the gaskets and a leakage of the cell can occur (PTFE compounds, e.g. with glass powder or graphite, show a better behavior.)... 

Low-temperature p-hydrogen requires the use of materials that retain good ductility at low temperatures. Austenitic stainless steel (e.g. AISI 316L and 304L) or aluminum and aluminum alloys (Series 5000) are recommended. Polytetrafluor-oethylene (PTFE, Teflon) and 2-chloro-l,l,2-trifluoroethylene (Kel-F) can also be used. 

Polystyrene Polyimide (Kapton) PTFE (Teflon) Diamond SiOj... 

The modified parfait method developed here replaced silica gel with porous polytetrafluoroethylene (PTFE, Teflon). Properly wetted Chromosorb T, an aggregate of aqueous dispersion-polymerized PTFE, is an efficient adsorbent for many hydrophobic substances in water... 

Membrane materials often employed are hydrophobic polysulfone or hydrophilic regenerated cellulose or cellulose acetate other materials are nylon, polytetrafluoro-ethylene (PTFE, Teflon), polyether ether ketone (PEEK) or poly(divinyl fluoride) (PDVF). 

Nearly complete thermal decoupling is enabled by the use of a special backbone element used for insulation (see Figure 4.39). This element is made of fiber-reinforced PTFE (Teflon ), which is chemically fairly inert and possesses an extremely small heat conductivity coefficient of 0.25 W mK4 compared with the standard backbone materials steel (16 W mK 1 and aluminum (204 W mKT1). 

Since about 1950 polymer-bonded (or plastic-bonded) explosives (PBX) have been developed in order to reduce sensivity and to facilitate safe and easy handling. PBX also show improved processibility and mechanical properties. In such materials the crystalline explosive is embedded in a rubber-like polymeric matrix. One of the most prominent examples of a PBX is Semtex. Semtex was invented in 1966 by Stanislav Brebera, a chemist who worked for VCHZ Synthesia in Semtin (hence the name Semtex), a suburb of Pardubice in the Czech Republic. Semtex consists of varying ratios of PETN and RDX. Usually polyisobutylene is used for the polymeric matrix, and phthalic acid n-octylester is the plasticizer. Other polymer matrices which have been introduced are polyurethane, polyvinyl alcohol, PTFE (teflon), Viton, Kel-F and various polyesters. 

Resistance. The pump should be inert to the various solvents, buffer salts and solutes to which it will be exposed in general use. In the vast majority of applications, stainless steel is used for metallic parts that contact the mobile phase, and this is perfectly acceptable. Elsewhere in the pump, resistant minerals such as sapphire or ruby are used for the pistons and in valve components subject to hard wear, and materials such as PTFE (Teflon ) are used for gaskets and seals. 

Injection valves designed for FIA are produced by a number of manufacturers. These valves are often microprocessor controlled (26) and are quite versatile. However, for all of the analyses described later, a simple low-pressure rotary injection valve designed for liquid chromatography is adequate (e.g., Rheodyne Model 50). Pneumatic and electric actuators are available for automated operation. An injection valve that can be machined quite easily from poly(tetrafluoroethylene) (PTFE, Teflon) and Plexiglas is described elsewhere (25, 27). 

The product, commonly referred to as Teflon PFA (for perfluoro alkoxy), has a melting point (melt transition temperature, Tm) of about 305°C. It retains many of the desirable properties of PTFE (Teflon) homopolymer, and is much more readily melt-formable into products than PTFE itself. 

Polymeric materials for MF membranes cover a very wide range from relatively hydrophilic to very hydrophobic materials. Typical hydrophilic materials are polysulfone (PS), poly ether sulfone (PES), cellulose (CE) and cellulose acetate (CA), polyamide (PA), polyimide (PI), polyetherimide (PEI), and polycarbonate (PC). Typical hydrophobic materials are polyethylene (PE), polypropylene (PP), polytetra-fluoroethylene (PTFE, Teflon), and polyvinylidene fluoride (PYDF). 

Polytetrafluoroethylene (PTFE Teflon) was discovered accidently by PlunkettCZ nd commercialized by DuPont in the 1940 s. This polymer has a solubility parameter of about 6H and a high melting point of 327°C and is not readily moldable. Poly-chlorotrifluoroethylene (CTFE, Kel-F), the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF, Kynar), the copolymer of tetrafluoroethylene and ethylene (ETFE), the copolymer of vinylidene fluoride and hexafluoroisobutylene (CM-1), perfluoroalkoxyethylene (PFA) and polyvinyl fluoride (PVF, Tedlar) are all more readily processed than PTFE. However, the lubricity and chemical resistance of these fluoropolymers is less than that of PTFE. 

Solid perfluorocarbon surfaces also have extremely low surface energies Thus, poly(tetrafluoroethylene) (PTFE, Teflon) has a y value of 18.5 dyn cm which is the reason for the anti-stick and low-friction properties used for frying pans and other applications. That this effect is directly related to the fluorine content becomes obvious on comparison of the surface energies of poly(difluoro-ethylene) (25 dyn cm ), poly(fluoroethylene) (28 dyn cm ), and polyethylene (31 dyn cm Y If only one fluorine atom in PTFE is replaced by more polarizable chlorine, the surface energy of the resulting poly(chlorotrifluoroethylene) jumps to 31 dyn cm , the same value as for polyethylene [8]. 

---