Tetrafluoroethylene modified PTFE

Modified PTFE represents a relatively new technology that is designed to overcome the limitations of conventional PTFE, namely, poor creep resistance (i.e., tendency to cold flow), difficult welding, and high level of microvoids [35], These changes of properties are accomplished by addition of small amount comonomer in amounts less than 0.1%. Such modifier is most frequently perfluoropropylvinyl ether (PPVE). The copolymerization is carried out in aqueous suspension under practically the same conditions as the homopolymerization of tetrafluoroethylene, that is, at TEE pressures in the range 5 to 20 bar (72 to 290 psi) and temperature range 35°C to 90°C (95°E to 194°E) [36]. There is more on modified PTFE in Section 7.7. 

Copolymeis of ethylene [74-85-1] and tetiafluoioethylene [116-14-3] (ETFE) have been alaboiatory curiosity for more than 40 years. These polymers were studied in connection with a search for a melt-fabricable PTFE resin (1 5) interest in them fell with the discovery of TFE—HFP (FEP) copolymers (6). In the 1960s, however, it became evident that a melt-fabricable fluorocarbon resin was needed with higher strength and stiffness than those of PTFE resins. Earlier studies indicated that TFE—ethylene copolymers [11939-51 -6] might have the right combination of properties. Subsequent research efforts (7) led to the introduction of modified ethylene—tetrafluoroethylene polymer [25038-71-5] (Tefzel) by E. I. du Pont de Nemours Co., Inc, in 1970. 

Modified poiytetrafluoroethylene (PTFE) Copolymer of tetrafluoroethylene (TFE) and of a small amount (less than 1%) of other perfluorinated monomer (e.g., perfluoroalkoxy monomer) exhibiting considerably improved physical properties, moldability, and much lower microporosity. 

The sulfide group in PPS can be oxidized in a mixture of glacial acetic acid, concentrated sutfijric acid, and concentrated hydrogen peroxide at 55°C within 3 h to 5deld a polymer with sulfone groups. This modified polymer is used with poly(tetrafluoroethylene) (PTFE) for composites with improved abrasion resistance. 

Hexafluoropropylene/vinylidene fluoride/ tetrafluoroethylene teipolymer, Viton A-100 Viton A-200 fluoroelastomer, tank coatings Hexafluoropropylene/vinylidene fluoride/ tetrafluoroethylene terpolymer fluoroelastomer, tank solution coatings Viton A-100 Viton A-200 fluoroelastomer, thin film Fluordatex 200 fluoropolymer modifier Dynasylan F 8815 fluoropolymer, coatings Dyneon THV 220A Teflon PTFE 30 Teflon TE-3667N... 

For areas with special application requirements, specifically modified polyester fabrics, as well as fabrics from aramid fibres, fluorine polymers and arylamides like Kevlar (ref. DuPont), have proved to be satisfactory. The membranes show different characteristics depending on the coatings used. Fluorine polymers such as PVDF (polyvinylidene fluoride) are used on PES fabrics (refs Mehler and Ferrari) a PTFE (polytetrafluoroethylene) coating is very suitable for fibreglass fabrics (ref Verseidag) and there is a newly developed composite membrane with THV (ret Dyneon), a polymeric blend of tetrafluoroethylene, hexafluoropropylene and vinylidenefluorine, used as a coating on PES fabrics, of which VALMEX vivax (ret Mehler) is one example. 

This basic polymer is modified by substituting fluorine for the hydrogen. This process is applied to many other compounds and is called petfluorination. The mer is called tetrafluoroethylene The modified polymer, shown in Figure 4.3, is polytetrafluoroethy-lene, or PTFE. It is also sold as Teflon, the registered trademark of ICI. This remarkable... 

In this chapter, synthesis and properties of major monomers for polymerization of melt-processible fluo-roplastics are discussed. Tetrafluoroethylene is the primary monomer. Small amounts of other monomers are incorporated in the TFE polymer structure to modify its properties and processing characteristics. These monomers include hexafluoropropylene (HFP), per-fluoroalkylvinylethers (PAVE), and chlorotrifluoro-ethylene (CTFE). A number of specialty monomers, though less common, are also used to modify the PTFE structure. Examples include perfluoroisopropyl vinyl ether and perfluorobutyl ethylene. Preparation of important monomers including vinyl fluoride and vinylidene fluoride are reviewed. 

Trogadas and Ramani summarized the modification of PEM membranes, including Nafion modified by zirconium phosphates, heteropolyacids, hydrogen sulfates, metal oxides, and silica. Membranes with sulfonated non-fluorinated backbones were also described. The base polymers polysulfone, poly(ether sulfone), poly(ether ether ketone), polybenzimidazole, and polyimide. Another interesting category is acid-base polymer blend membranes. This review also paid special attention to electrode designs based on catalyst particles bound by a hydrophobic poly-tetrafluoroethylene (PTFE) structure or hydrophilic Nafion, vacuum deposition, and electrodeposition method. Issues related to the MEA were presented. In then-study on composite membranes, the effects of particle sizes, cation sizes, number of protons, etc., of HPA were correlated with the fuel cell performance. To promote stability of the PTA within the membrane matrix, the investigators have employed PTA supported on metal oxides such as silicon dioxide as additives to Nafion. 

Dodecanoic Acid Ethylene Tetrafluoroethylene Copolymer (ETFE) Polyamideimide (PAI) Polyethylene, Crosslinked (XPE) Polyketone, Polyetheretherketone (PEEK) Polyphenylene Ether, Modified Polyphenylene Sulfide (PPS) Polysulfone Polytetrafluoroethylene (PTFE) Polyvinylidene Fluorides (PVDF) Epoxy 8 9 8 9 Ethanoic Acid ... 

The commercially important fluorocarbon polymers are poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly[tetrafluoroethylene-co-(perfluoroaJkylvinyl ether)] (PFA), and amorphous fluoropolymer (AF), typically copolymers of tetrafluoro-ethylene and fluorinated dioxole. The second group of fluoropolymers includes modified poly(tetrafluoroethylene-co-ethylene) (ETFE), poly(vinylidene fluoride) (PVDF) (sometimes referred to as PVF2), and copolymers of vinylidene fluoride, poly(chlorotrifluoroethylene) (PCTFE), poly(chlorotrifluorethylene-co-ethylene) (E/CTFE) and poly(vinyl fluoride) PVF. 

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