Materials of Construction - Fluoro Rubber
November 15, 2003
Description
| Common Name | FKM, FPM, FFKM |
| Chemical Name | Fluoro Rubber |
| Trade Names | VITON® (registered trademark of the DuPont Dow Elastomers) FLUOREL® (registered trademark of the 3M Company) |
| General | FKM is a M Class Rubber - Contains a saturated chain of the polymethylene type
- Fluoro rubber of the polymethylene type having substituent fluoro and perfluoroalkyl groups on the polymer chain
Fluorocarbon elastomers are inherently compatible with a broad spectrum of chemicals. Because of this extensive chemical compatibility, which spans considerable concentration and temperature ranges, fluorocarbons have gained wide acceptance as a material of construction for butterfly valve o-rings and seats. Excellent resistance to mineral acids, salts solutions, oils and many aliphatic and aromatic hydrocarbons. Attacked by caustic (sodium hydroxide) and low molecular weight organics. There are several different grades of material available. Care should be taken in selecting the right grade for the application. |
| Application | General - Not suitable for steam service
- Gaskets
- O-rings
- Bellows
Sulphuric Acid Plants - Seals and gaskets in the gas cleaning system handling weak sulphuric acid.
- Plate heat exchanger gaskets
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Viton
DuPont produces several different grades of Viton. There are three major families of standard Viton Fluoroelastomers: A, B and F. The designation refer to their relative resistance to attacks by fluids and chemicals. The differences in fluid resistance that exist are the result of different levels of fluorine in the polymer which is determined by the types and relative amounts of monomers that comprise the polymer.
| Type | Chemical Composition | Fluorine Content | Description |
| A | -CH2-CF2-CF3CFCF2- | 66% | The most common fluoroelastomer composition used in O-rings. Comprised of vinylidene fluoride (VF2) and hexafluoropropylene (HFP). |
| B | -CH2-CF2-CF3CFCF2-CF2-CF2- | 67% | Improved acid and alcohol resistance over A type. Comprised of vinylidene fluoride (VF2), hexafluoropropylene (HFP) and tetrafluoroethylene (TFE). |
| GF or F | | 70% | Improved fuel and alcohol resistance. Comprised of vinylidene fluoride (VF2), hexafluoropropylene (HFP) and tetrafluoroethylene (TFE). |
| GLT | | 65% | Often referred to as “Good for Low Temperature”. Good performance down to –40oC. Introduced in 1976, this type was the first commercial fluoroelastomer to use the fluorinated vinyl ether monomer. |
| GFLT | | 68% | Often referred to as “Good for Fluids and Low Temperature”. Good performance down to –35oC. |
| AFLAS | -CF2-CF2-CH3CHCH2- | 55 to 60% | Excellent resistance to bases, amines and solvents. |
| Super FKM | -CF2-CF2-CF3OCFCF2-CH2-CH2- | 72 to 74% | Resistance to fluids is increased with the higher fluorine content |
| Perfluoroelastomers FFKM | -CF2-CF2-CFOCFCF2- | 75% | Family of fully-fluorinated fluorocarbon elastomers |
The chemical make-up of the polymer contributes to the differences in physical properties and chemical resistance between the materials. As well, the compounding method, particularly the cross-linking or curing system used imparts certain physical characteristics to the material.
GLT types are peroxide cured which provides fast cure rates and imparts excellent physical properties. As such, only the G type of fluoroelastomers are suitable for service in sulphuric acid.
Viton B is the original grade of Viton used in plate heat exchangers when they were first introduced into sulphuric acid plants.
Viton G is Alfa Laval's recommended material for hot concentrated sulphuric acid. The material Vton G contains substantially more fluorine than other grades which improves its resistance to hot concentrated sulphuric acid. The gasket material is also peroxide cured which provides the lowest temperature relaxation and the lowest acid absorption.
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Naming
With the wide range of materials available a naming system was created to identify the material more accurately.
Viton A-401C
1st Character (letter)
Represents the type of viton: A, B or F
A “G” prefix, in addition to a type prefix, indicates that the polymer can be crosslinked with the peroxide cure system.
An “L” designation indicates that the polymer provides slightly improved low temperature flexibility.
An “LT” designation indicates a more significant improvement in low temperature performance criteria.
2nd Character (Number)
Represents nominal Mooney Viscosity of the product – ML 1 + 10 at 121oC (250oF)
3rd Character (Number)
Represents the relative level of curative in a precompound on a scale of 10 to 1 (10 is represented by 0)
0 – High curative level (for optimum compression set)
9 to 2 – Intermediate, decreasing levels of curative (increased elongation at break, tear resistance)
1 – Low curative level (for optimum tear, flex resistance)
4th Character (Number)
Represents a slightly different version of a particular compound (e.g. Viton A-402C contains process aid, A-401C does not).
5th Character (Letter)
No letter suffix indicates that the product is a gum polymer only and containes no curatives (may contain process aid).
“C” indicates that the product is a precompound, containing accelerator and curative.
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FAQs
Among other things, the fluoro rubber compounds produced by RADO are used to manufacture hoses, such as fuel and turbocharger hoses for the automotive industry. However, fluorocarbon rubber is also suitable for making seals, cable insulation, linings, diaphragms and protective gloves.
Is fluoro rubber the same as Viton? ›
Fluoro-Elastomer is usually referred to as FKM FPM or as VITON™ after the popular brand which produces it. You may see this rubber listed in different places with these different names, but they are all one and the same. Originally developed by Du Pont, it is produced by a number of companies around the world.
What is fluoride rubber? ›
Fluoride rubbers are mixed polymers. The first type, a copolymer made of vinylidene fluoride and hexa fluoride propylene was introduced to the market in 1958 by DU PONT under the name of VITON.
Is fluorocarbon rubber or plastic? ›
Due to its wide range of chemical compatibility, temperature range, low compression set, and excellent aging characteristics, fluorocarbon rubber is the most significant single elastomer developed in recent history.
Is fluoroelastomer safe? ›
Fluoroelastomers are first compounded into required formulations with a variety of ingredients; some of them may be reactive and/or toxic. In mixing and subsequent processing into finished products, some components of the formulations may generate toxic byproducts.
Is fluoroelastomer the same as silicone? ›
In summary, fluoroelastomer is a better choice for applications that require chemical resistance and high temperature resistance, while silicone rubber is a better choice for applications that require heat resistance, weatherability, and electrical insulation properties.
Is fluoro rubber food grade? ›
Fluorocarbon is known for its high temperature resistance, chemical resistance, and improved resistance to steam with selective grades. Fluorocarbon o-rings do not absorb water, allowing them to seal effectively without excessive swell. These features make fluorocarbon an excellent choice for FDA grade applications.
Which is better Viton or EPDM? ›
In fact, Viton offers near-universal chemical resistance for sealing applications for oils, fuels, and mineral acids. It's also exceptionally strong and durable. EPDM's performance in low temperatures makes it a better choice over Viton in cold environments.
What is better than Viton? ›
Buna is effective to 250°F. However, it can effectively seal mechanical objects at low temperatures to –22°F. Viton seals are rendered ineffective at temperatures below 5°F, with the material becoming hard and inflexible. Environmental conditions also differentiate the application of Buna vs.
What is the generic name for Viton? ›
Fluoroelastomer, FKM, FPM, and Viton® are all different names for the same synthetic rubber material family.
Viton® is the brand name for fluorocarbon rubber polymers of the Chemours Company. This type of polymer is used extensively by ERIKS, however we do not claim or promote the use of any specific brands of polymers in our compounds.
Is it FKM or Viton? ›
To this day, that material is now used in a number of other industries, including the automotive, appliance, and chemical and fluid industries. Originally trademarked by DuPont (now the Chemours Company), Viton® is now a generally accepted generic term for a brand of fluroelastomer called FKM.
What are the disadvantages of fluorocarbons? ›
Because of the rigidity of fluorocarbon, the angles imposed on a line by various knots weaken the line regardless of whether you wet it or not. Add to this the impact from usage and strain from catching fish, and fluorocarbon can break down at critical points such as during the hookset and while fighting a fish.
Why is fluorocarbon expensive? ›
Fluorocarbon lines have a retail price that is often 2X-3X higher than nylon(monofilament) lines. The higher retail cost is a direct result of the fluorocarbon raw materials being more expensive than nylon options. This higher cost can be compounded if you are a new angler or an angler that backlashes frequently.
Is fluorocarbon good or bad? ›
Fluorocarbon is more of a stiffer material, and it tends to flatten though the rod rings and slap against the blank, so it's only really good for shorter distances.
Why is rubber used for hoses? ›
Rubber hose is widely used in conveying systems for both pipeline and bends and in systems where a degree of natural flexibility is required. Its particular properties also make it ideal for use in systems where the material being conveyed may be friable, abrasive, or cohesive.
What is a rubber tubing used for? ›
Rubber tubing, also referred to as rubber hose or rubber piping, is a synthetic or natural rubber that is primarily used to transport and circulate liquids and gases. As well as being used within households, rubber tubing is widely used for industrial applications, due to its durability and flexibility.
What is rubber cord used for? ›
These cords find applications in diverse sealing requirements, such as sealing outer lid gaskets for cases, automotive O-rings, sealing rubber rods in the oil industry, high-pressure gauges and meters, plugging holes in extruded rubber fenders, jewellery manufacturing, and more.
Which is better Viton or NBR? ›
Depending on the construction and grade of the seal, a Viton seal can withstand temperatures as low as -20ºC and as high as 210ºC. On the other hand, NRB can withstand temperatures as low as -30ºC and as high as 100ºC. NRB seals can't compete with Viton seals in situations with high temperatures.
