Polytetrafluoroethylen polymerization

The most diffused material for membranes is based on co-polymers of tetrafluoroethylene (TEE) with perfluorosulfonate monomers. The resulting co-polymer is constituted by polytetrafluoroethylene polymeric chain (PTFE, commercially known as Teflon) in which some fluorine atoms are substituted by sulfonated side chains. The monomer perfluoro-sulfonyfluoride ethyl-propyl-vinyl ether is used in membranes commercialized by Dupont with the registered trademark Nafion (Fig. 3.2), which is the most well-known material used as electrolyte in PEM fuel cells. 

The analysis of heat capacity of a given homopolymer thus starts with the evaluation of the experimental crystalline and amorphous heat capacities over as wide a temperature range as possible. For amorphous polymers, the glassy and liquid heat capacities are directly measurable. For crystallizing polymers, the crystalline and amorphous heat capacities may have to be extrapolated, as illustrated in the polyethylene example in Fig. 5.17. Only in rare cases are almost completely crystalline polymers samples available (as for example, for polyethylene, polytetrafluoroethylene, polymeric selenium, and polyoxymethylene). 

Polymerization polyethylene (PE), Teflon (polytetrafluoroethylene, PTFE), polystyrene (PS), and etc. 

Being microwave-transparent, the reaction vessels will be no hotter than their contents. As mentioned above, they usually are made from insulating polymeric materials like polytetrafluoroethylene (PTFE), which have inherent advantages for cleaner processing. In contrast with other materials, PTFE is resistant to attack by strong bases or HF and is not corroded by halide ions. 

Instead of using plasma-polymerized polyfluorocarbon as HIL, Qiu et al. utilized a thermally deposited Teflon (polytetrafluoroethylene) thin layer as a HIL, which results in... 

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

Aqueous corrosion resistance, 13 513 Aqueous dispersion polymerization, 18 291 of acrylonitrile, 11 197-200 Aqueous dispersions, 13 292. See also Aqueous polytetrafluoroethylene dispersions... 

Aqueous perchlorate solutions, 18 274 Aqueous plugs, in microfluidics, 26 968 Aqueous polytetrafluoroethylene dispersions, 18 291 Aqueous potassium permanganate solutions, 15 597-600 Aqueous ring-opening metathesis polymerization (ROMP), 15 495... 

Polytetrafluoroethylene (Tf) is a polymeric fluorine compound that consists of a -C2F4- molecular structure,ini which contains a mass fraction of fluorine of 0.75. Tf is insoluble in water and its specific mass is in the range 3550-4200 kg nr in peUe-... 

Since many polymeric materials are used as clothing, household items, components of automobiles and aircraft, etc. flammability is an important consideration. Some polymers such as polytetrafluoroethylene and PVC are naturally flame-resistant, but most common polymers such as PE and PP are not. Small-scale horizontal flame tests have been used to estimate the flammability of solid (ASTM D-635), cellular (ASTM D-1692-74), and foamed (ASTM D-1992) polymers, but these tests are useful for comparative purposes only. Large-scale tunnel tests (ASTM E-84) are more accurate, but they are also more expensive to run than ordinary laboratory tests cited before. 

V.N. Vasilets, G. Hermel, U. Konig, C. Werner, M. Muller, F. Simon, K. Grundke, Y. Ikada, H.J. Jacobasch, Microw/ave CO2 plasma-initiated vapour phase graft polymerization of acrylic acid onto polytetrafluoroethylene for immobilization of human thrombomodulin. Biomaterials 18 (1997) 1139-1145. 

Polymeric hydrocarbons, such as polyolefins, are readily combustible and can actually serve as a fuel source. In contrast, polytetrafluoroethylene (ptfe) does not bum in air but burns in oxygen or in nitrogen-oxygen mixtures which have a very high oxygen concentration. 

Tetrafluoroethylene (TFE), also known as perfluoroethylene, is a colorless, flammable, toxic gas. It is the monomer used for polytetrafluoroethylene (PTFE), which is sold under the DuPont tradename of Teflon. TFE is co-polymerized with other compounds to produce a variety of Teflons. TFE is produced by heating chlorodifluoromethane (CHC1F2, Freon-22) or trifluoromethane (CldF3, Freon-23). TFE is used almost exclusively as a monomer in the production of PTFE. PTFE is a vinyl polymer, which means it is made from a monomer with carbon-carbon double bonds. PTFE is made from TFE by free radical polymerization. 

Polyethylene terephthalate [25038-59-9] (8) is a polyester produced by the condensation polymerization of dimethyl terephthalate and ethylene glycol. Polyethylene terephthalate sutures are available white (undyed), or dyed green with D C Green No. 6, or blue with D C Blue No. 6. These may be coated with polybutylene adipate (polybutilate), polyydimethylsiloxane, or polytetrafluoroethylene [9002-84-0]. The sutures are distributed under the trade names Ethibond Exel, Mersilene, Polydek, Silky II Polydek, Surgidac, Tevdek II, Polyester, and Tl.Cron. 

In starting a residue analysis in foods, the choice of proper vials for sample preparation is very important. Available vials are made of either glass or polymeric materials such as polyethylene, polypropylene, or polytetrafluoroethylene. The choice of the proper material depends strongly on the physicochemical properties of the analyte. For a number of compounds that have the tendency to irreversible adsorption onto glass surfaces, the polymer-based vials are obviously the best choice. However, the surface of the polymer-based vials may contain phthalates or plasticizers that can dissolve in certain solvents and may interfere with the identification of analytes. When using dichloromethane, for example, phthalates may be the reason for the appearance of a series of unexpected peaks in the mass spectra of the samples. Plasticizers, on the other hand, fluoresce and may interfere with the detection of fluorescence analytes. Thus, for handling of troublesome analytes, use of vials made of polytetrafluoroethylene is recommended. This material does not contain any plasticizers or organic acids, can withstand temperatures up to 500 K, and lacks active sites that could adsorb polar compounds on its surface. 

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... 

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