Fluoroelastomers polymer structure

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. 

As shown in the previons section, many of the fundamental properties of the polymers depend on their structure, mainly on the nature of monomeric units composing them. This section concentrates on the specific properties of individual fluoropolymers— more specifically fluoroplastics—and how they relate to their utility in practical applications. The properties of fluoroelastomers are discussed in Chapter 5. 

Traditionally, a fluoropol5mier or fluoroplastic is defined as a polymer consisting of carbon (C) and fluorine (F). Sometimes these are referred to as per-fluoropolymers to distinguish them from partially flu-orinated pol miers, fluoroelastomers, and other polymers that contain fluorine in their chemical structure. For example, fluorosilicone and fluoroacrylate polymers are not referred to as fluoropolymers. An example of a linear fluoropol5mier is tetrafluoroeth-ylene pol5mier (PTFE) ... 

Fluoroelastomers are fluorine-containing hydrocarbon polymers with a saturated structure obtained by polymerizing fluorinated monomers such as vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene. The result is a high-performance s)mthetic rubber with exceptional resistance to oils and chemicals at elevated temperatures. Initially, this material was used to produce O-rings for use in severe conditions. Although this remains a major area of application, these compoimds have found wide use in other applications because of their chemical resistance at high temperatures and other desirable properties. 

Fluoroelastomers are fluorine containing hydrocarbon polymers with a saturated structure obtained by polymerizing fluorinated monomers such as vinylidene fluoride, hexafluoroprene, and tetrafluoroethylene. The result is a high performance rubber with exceptional resistance to oils and chemicals at elevated temperatures. 

Scheirs, J. Structure/FYoperty Considerations for Huoropolymers and Fluoroelastomers to Avoid In-service Failure. In Modem Fluoropolymers, High Performance Polymers for Diverse Applications, Scheirs, J., Ed. John Wiley Sons Chichester, UK, 1997 pp 1-69. 

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