Properties of Tetrafluoroethylene

PERFLUORINATED POLYMERS, PTFE Table 1. Physical Properties of Tetrafluoroethylene V0I.3... 

Table 4.1 lists the properties of tetrafluoroethylene. It is a colorless, odorless, tasteless, nontoxic... 

Table 5.56. Properties of Tetrafluoroethylene and Ethylene Copolymers Made by Redox Catalysis> i...

Table 5.57. A Comparison of the Properties of Tetrafluoroethylene and Ethylene Terpolymersi ...

Tetrafluoroethylene. Emulsion polymerisation of tetrafluoroethylene, catalysed by oxygen, yields polytetrafluoroethylene (Tejlon) as a very tough horn-hke material of high melting point. It possesses excellent electrical insulation properties and a remarkable inertness towards all chemical reagents, including aqua regia. 

The ETEE copolymer can be cross-linked by radiation (30), despite the high content of tetrafluoroethylene units. Cross-linking reduces plasticity but enhances high temperature properties and nondrip performance. The irradiated resia withstands a 400°C solder iron for 10 min without noticeable effect. 

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

In 1989 Du Pont introduced Teflon AF, said to be a copolymer of tetrafluoroethylene and trifluoromethyldifluorodioxol. This amorphous fluoro-polymer has a similar heat and chemical resistance to PTFE but possesses several notable properties, including ... 

In attempts to further improve the stability of fluorine-containing elastomers Du Pont developed a polymer with no C—H groups. This material is a terpolymer of tetrafluoroethylene, perfluoro(methyl vinyl ether) and, in small amounts, a cure site monomer of undisclosed composition. Marketed as Kalrez in 1975 the polymer withstands air oxidation up to 290-315°C and has an extremely low volume swell in a wide range of solvents, properties unmatched by any other commercial fluoroelastomer. This rubber is, however, very expensive, about 20 times the cost of the FKM rubbers and quoted at 1500/kg in 1990, and production is only of the order of 1 t.p.a. In 1992 Du Pont offered a material costing about 75% as much as Kalrez and marketed as Zalak. Structurally, it differs mainly from Kalrez in the choice of cure-site monomer. 

Catalytic properties of the active acid form of the composites obtained in comparison with random copolymers of tetrafluoroethylene and PFAVESF (Nafion-type) were investigated in esterification, oligomerization, and aromatic compounds alkylation reactions. 

Polytetrafluoroethylene ionomers, properties of, 14 475 76 Poly(tetrafluoroethylene-co-hexafluoropropylene) films, 23 720... 

Teflon HP Plus copolymers, 18 331 in lotus effect surfaces, 22 117 Teflon PFA. See also Tetrafluoroethylene-perfluorovinyl ether applications of, 18 338-339 chemical properties of, 18 332-333 economic aspects of, 18 338 electrical properties of, 18 334 health and safety factors related to, 18 338... 

PEP, copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HEP), has physical and chemical properties similar to those of PTFE, but it differs from it in that it can be processed by standard melt processing techniques. 

The Teflon AF family consists of copolymers of tetrafluoroethylene, (TFE) and 2,2-bis-trifluoromethyl-4,5-difluoro-l,3-dioxole, (PDD), whose structure is shown in Figure 2.1. The properties of these amorphous copolymers vary with the relative amounts of the comonomers. At present the two commercial grades of Teflon AF are AF-1600 and AF-2400 with glass transition temperatures of 160 and 240°C respectively. The variation of glass transition temperature with composition is shown in Figure 2.2. Thus AF-1600 and AF-2400 contain 64 and 83 mol % PDD, respectively. 

However, there are many misconceptions concerning uses, applications, and attributes of fluorocarbons. The use of fluorocarbons can be classified into two major categories (1) use of inherent bulk properties, and (2) modification of the surface properties of underlying materials. Once this has been established, the proper choice of fluorocarbon can be evaluated. For the purpose of this discussion, fluorocarbons will be grouped into two categories (1) polymers based on highly fluorinated monomers such as tetrafluoroethylene (TFE), hexafluoropropylene. 

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