What material is equivalent to FKM?

Fluoroelastomer, FKM, FPM, and Viton® are all different names for the same synthetic rubber material family. There are even more names for this material than we have listed here, these are simply the most common names. Why does the same material have so many different names?

You will get efficient and thoughtful service from Sanshi.

Here is what each of those names means:

• Fluoroelastomers are a family of fluoropolymer rubbers.
• FKM is the American standard (ASTM) short form name for Fluoroelastomers or fluoro rubber material. F stands for Fluoro; the K is an abbreviation of the German word Kohlenstoff, meaning Carbon; and the M is the designation of saturated backbone rubber from ASTM.
• FPM is the international ISO and ISO/TS standard registration for Fluoroelastomers.
• Viton® is a registered trademark of DuPont Performance Elastomers LLC. Back in they developed this compound to meet the stringent requirements of the aerospace industry for a higher-performing elastomer. The use of the material quickly spread to other industries such as automotive, chemical, and fluid power industries.

This highly fluorinated carbon-based polymer is divided into five classes based on chemical composition, fluorine content, or their cross-linking mechanism. Fluoroelastomers with higher fluorine content have increasing fluid resistance as the fluorine levels go up.

Like most elastomers, Fluoroelastomers are composed of multiple monomers. Specifically, there are six major monomers used to create the various types of Fluoroelastomers:

• Ethylene (E)
• Hexafluoropropylene (HFP)
• Perfluoro Methyl Vinyl Ether (PMVE)
• Propylene (P)
• Tetrafluoroethylene (TFE)
• Vinylidene Fluoride (VDF)

This chart gives a quick overview of these monomers and type of Fluoroelastomers:

Fluorine ContentMonomers in straight chain segments  Monomers with bulky side groups  Examples VDFTFEEHFPPMVEPCSM 66%X  X   Viton A66-70%XX X   Viton B, F, AL65.5-70%XX X  XViton GAL-S, GBL-S, GF-S64.5-67%XX  X XViton GLT-S, GBLT-S, GFLT-S66% XX X XViton ETP-S60% X   XXViton TBR-S, Aflas %XX   XXAflas -74% X  X XPerfluoroelastomer

Fluoroelastomers have extraordinary resistance to most fluids at high temperatures. The material can withstand extreme temperatures with a useful service life above 473°F/225°C, chemicals, heat, and oil. For these reasons, Fluoroelastomer has become one of the most widely used materials to create O-rings and seals. The material&#;s composition of monomers can be customized to provide a boost to its attractive properties, changes such as:

• Improved temperature resistance (both low and high)
• Good oil and grease resistance
• Excellent resistance to aggressive oxidation, acids, fuels, or chemicals
• Good resistance to extreme environments
• Low compression set
• Low gas absorption rate
• And more

Though, keep in mind that all types typically have limited resistance to methanol, hot water (above 212°F or 100°C), steam, and other highly polar fluids. The other main drawback of this family of materials is its intolerance to low temperatures (limit of -22°F or -30°C).

What are Fluoroelastomers used for?

This family of materials is used in a variety of industries such as automotive, semiconductor manufacturing, air transportation, medical, food manufacture, chemical processing, power generation, and many more.

Here are a few popular industries that utilize Fluoroelastomers and how they are used:

IndustryApplicationAerospaceO-rings and seals used in auxiliary power units, connectors, line fittings, hydraulic actuators, pumps, valves, oil reservoirs, and more.AutomotiveO-rings and seals used in fuel injection, head, and intake manifolds, and more.IndustrialO-rings and seals used in oil and gas systems, pumps, valves, tanks, heat exchange equipment, and more.SemiconductorWafer fabrication

Fluoroelastomers can be fabricated into O-rings, seals, hoses, and so much more for a variety of industries. These polymers enhance sealing reliability, safety, and prevent material leakages in a range of high-performance applications.

UC Components, Inc. can help!

UC Components, Inc. RediVac® O-rings are specially processed for use in critical applications. Our standard O-rings are manufactured from top quality fluoroelastomer materials. Buna, silicone, and other materials are available upon request. Specific chemistries may also be available upon request.

All of our O-rings are cleaned and packaged in our certified Class 100/ISO Class 5 Cleanroom, making them suitable for immediate use in most HV, UHV, EUV, or other clean-critical applications. Vacuum baked O-rings are available for reduced outgassing under vacuum.

UC Components, Inc. has been the world leader in high vacuum hardware since . We specialize in O-rings and fasteners for High Vacuum, Ultra High Vacuum, and other critical applications. View our parts catalog online to find the components you need, request a quote, or contact us for more assistance or additional information.

Material

FKM is a family of fluorocarbon-based fluoroelastomer materials defined by ASTM International standard D,[1] and ISO standard .[2] It is commonly called fluorine rubber or fluoro-rubber. FKM is an abbreviation of Fluorine Kautschuk Material.[3] All FKMs contain vinylidene fluoride as the common monomer, to which different other monomers are added for specific types and functionalities, fitting the desired application.

Originally developed by DuPont (under the brand name Viton, now owned by Chemours), FKMs are today also produced by many other companies, including: Daikin (Dai-El),[4] 3M (Dyneon),[5] Solvay S.A. (Tecnoflon),[6] HaloPolymer (Elaftor),[7] Gujarat Fluorochemicals (Fluonox),[8] and several Chinese manufacturers. Fluoroelastomers are more expensive than neoprene or nitrile rubber elastomers. They provide additional heat and chemical resistance.[9] FKMs can be divided into different classes on the basis of either their chemical composition, their fluorine content, or their cross-linking mechanism.

Types

[

edit

]

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

• Type-1 FKMs are composed of vinylidene fluoride (VDF) and hexafluoropropylene (HFP). Copolymers are the standard type of FKMs showing a good overall performance. Their fluorine content is approximately 66 weight percent.
• Type-2 FKMs are composed of VDF, HFP, and tetrafluoroethylene (TFE). Terpolymers have a higher fluorine content compared to copolymers (typically between 68 and 69 weight percent fluorine), which results in better chemical and heat resistance. Compression set and low temperature flexibility may be affected negatively.
• Type-3 FKMs are composed of VDF, TFE, and perfluoromethylvinylether (PMVE). The addition of PMVE provides better low temperature flexibility compared to copolymers and terpolymers. Typically, the fluorine content of type-3 FKMs ranges from 62 to 68 weight percent.
• Type-4 FKMs are composed of propylene, TFE, and VDF. While base resistance is increased in type-4 FKMs, their swelling properties, especially in hydrocarbons, are worsened. Typically, they have a fluorine content of about 67 weight percent.
• Type-5 FKMs are composed of VDF, HFP, TFE, PMVE, and ethylene. Known for base resistance and high-temperature resistance to hydrogen sulfide.

  [

  10

  ]

Cross-linking mechanisms

[

edit

]

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

The company is the world’s best FKM Oil Seal supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

• Diamine cross-linking using a blocked diamine. In the presence of basic (alkaline) media, VDF is vulnerable to dehydrofluorination, which enables the addition of the diamine to the polymer chain. Typically, magnesium oxide is used to neutralize the resulting hydrofluoric acid and rearrange into magnesium fluoride and water. Although rarely used today, diamine curing provides superior rubber-to-metal bonding properties as compared with other cross-linking mechanisms. The diamine's capability to be hydrated makes the diamine cross-link vulnerable in aqueous media.
• Ionic cross-linking (dihydroxy cross-linking) was the next step in curing FKMs. This is today the most common cross-linking chemistry used for FKMs. It provides superior heat resistance, improved hydrolytic stability and better compression set than diamine curing. In contrast to diamine curing, the ionic mechanism is not an addition mechanism but an aromatic nucleophilic substitution. Dihydroxy aromatic compounds are used as the cross-linking agent, and quaternary phosphonium salts are typically used to accelerate the curing process.
• Peroxide cross-linking was originally developed for type 3 FKMs containing PMVE as diamine and bisphenolic cross-linking systems can lead to cleavage in a polymer backbone chain containing PMVE. While diamine and bisphenolic cross-linking are ionic reactions, peroxide cross-linking is a free-radical mechanism. Though peroxide cross-links are not as thermally stable as bisphenolic cross-links, they normally are the system of choice in aqueous media and nonaqueous electrolyte media.

Properties

[

edit

]

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.[4]

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.

They can be easily distinguished from many other elastomers because of their high density of over kg/m3, significantly higher than most types of rubber.[12][13][14]

Applications

[

edit

]

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

• Chemical process and petroleum refining, where they are used for seals, pumps, gaskets and so on, due to their resistance to chemicals;
• Analysis and process instruments: separators, diaphragms, cylindrical fittings, hoops, gaskets, etc.
• Semiconductor manufacturing;
• Food and pharmaceutical, because of their low degradation, also in contact with fluids;
• Aviation and aerospace: high operating temperatures and high altitudes require superior heat and low-temperature resistance.

  [

  4

  ]

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]

FKM O-rings have been used safely for some time in SCUBA diving by divers using gas blends referred to as nitrox. FKMs are used because they have a lower probability of catching fire, even with the increased percentages of oxygen found in nitrox. They are also less susceptible to decay under increased oxygen conditions.

While these materials have a wide range of applications, their cost is prohibitive when compared to other types of elastomers, meaning that their adoption must be justified by the need for outstanding performance (as in the aerospace sector) and is inadvisable for low-cost products.

FKM/butyl gloves are highly impermeable to many strong organic solvents that would destroy or permeate commonly used gloves (such as those made with nitriles).

Precautions

[

edit

]

At high temperatures or in a fire, fluoroelastomers decompose and may release hydrogen fluoride. Any residue must be handled using protective equipment.

See also

[

edit

]

• Magnesium/Teflon/Viton
• FFKM, perfluoro-elastomers
• FEPM, tetrafluoro ethylene/propylene elastomers
• PVDF, polyvinylidene fluoride

References

[

edit

]

Want more information on NBR Oil Seal? Feel free to contact us.