The pros and cons of FKM (Viton®) Hydraulic Seals

When it was first introduced, Viton^® filled a need in the aerospace industry for a high-performance elastomer. 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. It is a mixture of synthetic rubber and fluoropolymer elastomer often used to manufacture O-rings, fuel system seals and hoses and a variety of other molded and extruded goods.

Viton^® has been dubbed, in some circles, the most durable and highest performing rubber on the market. It is also considered the best commercially available rubber in terms of fluid resistance.

Characteristics of Viton®

Viton^® fluroelastomers, often assigned a category under the ISO 1629 and ASTM D1418 designation of FKM, are part of the elastomer family, which is composed of copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP), as well as perfluoromethylvinylether (PMVE). Generally, Viton^®’s fluorine content hovers between 66% and 70%.

Applications of Viton®

There are different Viton^® polymer families suitable for a number of applications. These include:

• A (dipolymers of VF2/HFP): This family of polymers is used in general-purpose sealing, aerospace fuels and lubricants and automotive applications.
• B (terpolymers of VF2/HFP/TFE): This family of polymers is used for power utility seals and gaskets and in chemical process plants.
• Specialty types, including GLT, GBLT, GFLT and Viton^® Extreme (copolymers of TFE/propylene and ethylene/TFE/PMVE): Specialty types of Viton^® can be used for industries such as the automotive industry and the oil exploration industry.

Viton^® is also used in expansion joints and gaskets, shaft seals, fuel system seals and hoses.

Advantages of Viton® Seals

There are many tradeoffs to evaluate when considering Viton^® materials for a particular sealing application.

Compatibility
Viton® is compatible with hydrocarbons, lubricating and fuel oil, hydraulic oil, gasoline, kerosene, vegetable oils, alcohol and diluted acids.

Resistance
Of equal importance is that Viton® is abrasive, solvent and oil resistant as well as tear resistant. This means that seals composed of Viton® will last longer under a variety of conditions and in an assortment of environments.

Performance
In terms of performance, Viton® adheres well to metal and has a lower probability of catching fire than other sealing rubbers. Viton® is also less susceptible to decay under increased oxygen conditions.

Perhaps most important is that Viton® performs well in harsh environments, in temperature extremes and with harsh chemicals. The rubber is ideal for operating in hot and corrosive environments in temperatures up to 200 °C or even 220 °C for short periods of time — indications that Viton® is both weather and ozone resistant.

Figures: FKM (Viton®) V-Ring type A, for rotary shafts; O-Ring; Quad-Ring® and Kantseal for static solutions from Seals-Shop. Source: Seals-Shop

Disadvantages of Viton® Seals

Incompatibility
Despite the material being compatible with a whole host of oils and hydrocarbons, Viton^® is incompatible with ketones such as acetone, methyl ethyl ketone, ester solvents such as ethyl acetate, amines, and organic acids such as acetic acid.

Performance
Performance-wise, Viton^® isn’t ideal for every application. For instance, under excessively high temperatures (or fire), fluoroelastomers like Viton^® decompose, often releasing hydrogen fluoride, which is toxic and associated with ongoing respiratory tract irritation. Conversely, at excessively low temperatures, Viton^® seals can become hard and, consequently, inflexible.

Summary

In summary, Viton^®, which, as noted above, is a brand of fluroelastomer called FKM, is ideal for use in several industries, including the automotive, appliance and chemical and fluid industries, offering high-performance sealing solutions and capable of withstanding high temperatures. Considered the most durable rubber on the market, Viton^® is tear resistant as well as resistant to oils, solvents and abrasives, making it ideal for applications such as shaft seals, expansion joints and gaskets, power utility seals and general sealing, to name just a few.

About Seals-Shop

In Seals-Shop.com, the online shop of Trelleborg Sealing Solutions, we offer a wide number of hydraulic and pneumatic seals for a variety of applications, including many FKM (Viton®) products, such as O-rings, Quad-Rings^®, static seals and rotary seals, as well as O-ring energized rod seals and piston seals that can be found here.

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