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Fkm

The meaning of «fkm»

FKM is a family of fluorocarbon-based fluoroelastomer materials defined by the ASTM International standard D1418,[1] while it is called FPM by ISO 1629 (both first ed. 1995 and ed. 2013).[2] It is commonly called fluorine rubber or fluoro-rubber. All FKMs contain vinylidene fluoride as a monomer. Originally developed by DuPont (under the brand name Viton, now owned by Chemours), FKMs are today also produced by many companies, including: Daikin (Dai-El),[3] 3M (Dyneon),[4] Solvay S.A. (Tecnoflon),[5] HaloPolymer (Elaftor),[6] Gujarat Fluorochemicals (Fluonox),[7] Zrunek (ZruElast),[8] and several Chinese manufacturers including VSK Industrial.[9] Fluoroelastomers are more expensive than neoprene or nitrile rubber elastomers. They provide additional heat and chemical resistance. FKMs can be divided into different classes on the basis of either their chemical composition, their fluorine content, or their cross-linking mechanism.

On the basis of their chemical composition FKMs can be divided into the following types:

There are three established cross-linking mechanisms used in the curing process of FKMs.

Fluoroelastomers provide excellent high temperature (up to 500°F or 260°C[11]) and aggressive fluids resistance when compared with other elastomers, while combining the most effective stability to many sorts of chemicals and fluids such as oil, diesel, ethanol mix or body fluid.[3]

The performance of fluoroelastomers in aggressive chemicals depends on the nature of the base polymer and the compounding ingredients used for molding the final products (e.g. o-rings). Some formulations are generally compatible with hydrocarbons, but incompatible with ketones such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, amines, and organic acids such as acetic acid.[12]

They can be easily distinguished from many other elastomers because of their high density of over 1800 kg/m3, significantly higher than most types of rubber.[13][14]

Because of their outstanding performance they find use in a number of sectors, including the following:

They are suitable for the production of wearables, due to low wear and discoloration even during prolonged lifetimes in contact with skin oils and frequent exposure to light, while guaranteeing high comfort and stain resistance;[15]

The automotive industry represents their main application sector, where constant reach for higher efficiencies push manufacturers towards high-performing materials.[16] An example are FKM o-rings used as an upgrade to the original neoprene seals on Corvair pushrod tubes that deteriorated under the high heat produced by the engine, allowing oil leakage. FKM tubing or lined hoses are commonly recommended in automotive and other transportation fuel applications when high concentrations of biodiesel are required. Studies indicate that types B and F (FKM- GBL-S and FKM-GF-S) are more resistant to acidic biodiesel. (This is because biodiesel fuel is unstable and oxidizing.)[citation needed]

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