Fluoropolymer Elastomers

The poly(fluoroalkoxyphosphazene) elastomers offer a unique combination of properties including a wide operating temperature range, excellent fuel and oil resistance and low temperature properties superior to those of the fluoros11leones and fluoropolymer elastomers. 

Fluoropolymer elastomers (or Viton, a registered trademark of the DuPont Performance Elastomer LLC) consist of hexafluoropropylene (HFP), vinylidene fluoride (VDF), and tetrafluoroethylene. The 3M Corporation uses the trade name Fluorel. The structures of each of these monomers are shown in Figure 8.14. The fluorine content of these terpolymers is typically around 70% for Viton. Four basic types of this material are shown in Table 8.8 however, Viton Extreme comprises more types. 

Fluoroelastomer Fluoropolymer elastomer Fluorocarbon elastomer Fluorine rubber... 

Poly(vinyl fluoride) is included, although it shows greater similarities to poly(vinyl chloride) than to the other fluoropolymers. It also should be mentioned that a wide variety of fluoropolymer elastomers is used under extreme conditions of temperature and chemical environment. 

The brand name of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other moulded or extruded goods. The name is trademarked by DuPont Performance Elastomers L.L.C.,... 

Other sources of by-product HCl include allyl chloride, chlorobenzenes, chlorinated paraffins, linear alkylbenzene, siHcone fluids and elastomers, magnesium, fluoropolymers, chlorotoluenes, benzyl chloride, potassium sulfate, and agricultural chemicals. 

Peduoropolyethers, which constitute special class of fluoropolymer, are useful as lubricants,1 elastomers,2 and heat-transfer fluids under demanding conditions. Several commerical products are available, which are generally prepared by ring-opening polymerization of hexafluoropropylene oxide or by the random copolymerization oftetrafluoroethylene and hexafluoropropylene with oxygen under ultraviolet irradiation.3 Direct fluorination of hydrocarbon ethers has been reported4 but must be done very slowly under carefully controlled... 

Since fluorocarbon elastomers being discussed here contain hydrogen in their molecules, they have the tendency to cross-link in addition to scission, common in fluoropolymers when exposed to radiation. The cross-linking predominates, but there is still a significant degree of chain scission. ... 

Cross-linkable polymers used for wire and cable insulations are polyolefins, certain fluoropolymers, and elastomers. Among these, radiation cross-linked polyethylene is the most widely used. The radiation cross-linking process of PE has also been the most widely studied. ... 

The great value of the unique characteristics of fluorinated polymers in the development of modern industries has ensured an increasing technological interest since the discovery of the first fluoropolymer, poly(chlorotrifluoro-ethylene) in 1934. Hence, their fields of applications are numerous paints and coatings [10] (for metals [11], wood and leather [12], stone and optical fibers [13, 14]), textile finishings [15], novel elastomers [5, 6, 8], high performance resins, membranes [16, 17], functional materials (for photoresists and optical fibers), biomaterials [18], and thermostable polymers for aerospace. 

Monomers for commercially important large-volume fluoropolymers and their basic properties are shown in Table 1.1. These can be combined to yield homopolymers, copolymers, and terpolymers. The resulting resins range from rigid resins to elastomers with unique properties not achievable by any other polymeric materials. Details about the basic chemistry and polymerization methods are included in Chapter 2, fundamental properties of the resulting products are discussed in Chapter 3, and processing and applications in Chapter 4. 

Essentially, the high thermal and chemical stability of fluorocarbon elastomers, as of any fluoropolymers, is related to the high bond energy of the C-F bond, and also to the high bond energy of the C-C and C-H links, caused by the presence of fluorine.5... 

The glass transition temperature of PMTFPS is -75°C (-103°F). Moreover, it does not exhibit low-temperature crystallization at -40 C (-40°F) as PMDS does. Because of this and the low Tg, fluorosilicone elastomers remain very flexible at very low temperatures. For example, the brittleness temperature by impact (ASTM D 746B) of a commercial fluorosilicone vulcanizate was found to be -59°C (-74°F).62 This is considerably lower than the values typically measured on fluorocarbon elastomers. Fluorosilicones combine the superior fluid resistance of fluoropolymers with the very good low-temperature flexibility of silicones. 

The following fluoropolymers are commercially available in aqueous systems PTFE, PFA, MFA, FEP, ETFE, PVDF, THV Fluoroplastic, fluorocarbon elastomers, fluoroacrylates, and fluorinated polyurethanes. 

Currently, there is concern about the use of ammonium perfluorooctanoate (APFO), also known as C8 , which is necessary for the manufacture of fluorinated plastics and elastomers in water. C8 is a perfluorinated anionic surfactant used as a dispersing agent in the polymerization and copolymerization of many fluoropolymers, including poly(tetrafluoroethylene) (PTFE), poly(vinylidene... 

During the last two decades, many special fluoropolymers have been developed, such as fluorosilicones fluorinated polyurethanes fluorinated thermoplastic elastomers new, second-generation polymers and copolymers based on PTEE amorphous... 

Coatings and sealants for varied industrial applications are made by dissolving compounds of low-viscosity FKM elastomers (e.g., Viton C-10, Viton A-35, Dyneon 2145) in methyl ethyl ketone, ethyl acetate, methyl isobutyl ketone, amyl acetate, or other related ketones [68], Such products have typical useful storage life of 7 days at 24°C (75°F) and cure within 2 weeks [80], This subject is covered in more detail in Modern Fluoropolymers (Scheirs, J Ed.), Chapter 23 (Ross, E. W. Jr. and Hoover, G. S.), John Wiley Sons, New York (1997). 

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