Fluoroelastomers FKM

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. 

These compounds possess the rapid recovery from deformation, or resilience, of a true elastomer and exhibit mechanical properties of the same order of magnitude as those of conventional S5mthetic rubbers. 

FKM are manufactured under various trade names by different manufacturers. Three t) ical materials are listed below. 

Fluoroelastomers have been approved by the U.S. Food and Drug Administration for use in repeated contact with food products. More details are available in the Federal Register, Vol. 33, No. 5, Tuesday January 9, 1968, Part 121—Food Additives, Subpart F—Food Additives Resulting from Contact with Containers or Equipment and Food Additives Otherwise Affecting Food—Rubber Articles Intended for Repeated Use. 

The biological resistance of FKM is excellent. A typical compound tested against specification MIL-E-5272C showed no fungus growth after 30 days. This specification covers four common fungus groups. 

Mullins, Rubber Chem. Technol., 42, 339 (1969). J.A.C. Harwood and A.R. Payne, Journal of Applied Polymer Science 10,315,1966 http // en.wikipedia.org/wiki/Mullins effect. 

Payne A. R. (1962). The Dynamic Properties of Carbon Black-Loaded Natural Rubber Vulcanizates. Part I, J. Appl. Polym. Sci. 6 (19), pp 57-53. http //en.wikipedia.org/wiki/Payne effect  

Fletcher W. P. and Gent A. N. (1953). Non-Linearity in the Dynamic Properties of Vulcanised Rubber Compounds, Trans. Inst. Rubber Ind. 29, pp 266-280 

Jean Lebras Rubber-fundamentals of its science and technology page 95,1957 Chemical Publishing Co, INC NY USA. 

http //en.wikipedia.org/wiki/Hansen solubility parameter. 

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Amine Cross-Linking. Two commercially important, high performance elastomers which are not normally sulfur-cured are the fluoroelastomers (FKM) and the polyacrylates (ACM). Polyacrylates typically contain a small percent of a reactive monomer designed to react with amine curatives such as hexamethylene-diamine carbamate (Diak 1). Because the type and level of reactive monomer varies with ACM type, it is important to match the curative type to the particular ACM ia questioa. Sulfur and sulfur-beating materials can be used as cure retarders they also serve as age resistors (22). Fluoroelastomer cure systems typically utilize amines as the primary cross-linking agent and metal oxides as acid acceptors. 

Carbon Filled carbon Fluoroelastomer (FKM) Flexible graphite Flardfacing... 

Fluoro rubber of the polymethylene type having substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups on the polymer chain Fluoroelastomer FKM... 

Properties of Fluoroelastomers. FKM elastomers can have reasonably low glass transition temperatures, in the range of-18 to -40°C. The tensile properties of fluoroelastomers vulcanizates are fairly good but can decrease considerably with increasing temperatures. 

Uses of Fluoroelastomers. FKM elastomers are expensive, but their demand is high because of their unusual stability in very severe environments. They are used in specialty products, e.g., shaft seals of internal combustion engines, and components in aircraft and rockets. Products include seals, gaskets, liners, hoses, protective fabric coatings, diaphragms, roll covers, and cable jacketing. 

Ethylene propylene diene monomer (EPDM) Ethylene propylene monomer (EPM) Fluoroelastomers (FKM)... 

The fluoroelastomers (FKMs) are manufactured under various tradenames by different manufacturers. Typical materials are ... 

In the early part of this century, shortages of mined fluorspar caused restrictions in the manufacture of fluoroelastomers (FKMs), which impacted many rubber fabricators. 

Use other oil-resistant, specialty elastomers such as fluoroelastomers (FKM) however, the cost would be greater. 

Another category of fluoroelastomers, called FEPM has been created recently for base resistant fluoroelastomers. For higher temperature and chemical resistance fiiUy fluorinated materials, called perfluoroelastomers, are available in the form of molded seals and parts, such as Kalrez perfluoroelastomers parts and Chemraz Perfluoroelastomer Compounds. They bear the classification of JK or HK depending on supplier and compound offered, JK offering a continuous service temperature of 315°C. FFKM compounds are available from most FKM suppliers but gums are rarely available and in this chapter we focus on fluoroelastomers FKM and FEPM. 

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