Understanding Fluoroelastomers (FKM & Viton™) Rubber;

Properties, Applications, and Common Questions

By Cody David

Fluoroelastomers, also known as FKM or FPM, represent a significant class of synthetic rubber material designed for high-performance applications. FKM is a premier elastomer, possessing three critical characteristics:

  • Exceptional chemical resistance
  • High-temperature stability
  • Excellent weathering & environmental resistance

Fluoroelastomers (FKM) can be manufactured into various products as required by the application, such as:

  • Calendered Sheet
  • Rubber Extrusions
  • Compression, Injection, and Transfer Molded Rubber Parts

First developed in the late 1950s by DuPont de Nemours, Inc. under the trade name “Viton™”¹, FKM has since become the premier choice for addressing critical sealing solutions in various extreme environments.

Viton™, a Brand of Chemours Company Partner, Logo

Understanding FKM’s Properties

When deciding on which material to use in your application, the following charts serve as a starting point to determine when to consider using FKM. We recommend consulting with your rubber manufacturer or material design specialists when making this selection.

Table 1: General Physicals of Fluoroelastomer (FKM) Rubber

PropertyValue
Hardness (Shore A)60 to 85
Tensile strength (psi)700 to 1600
Elongation at break (%)125 to 400
Compression Set (%)<15
Temperature Range (°F)-20 to 500

Additionally, rubber compounds based on FKM elastomers are subjected to two stages of cure in order to optimize physical and mechanical properties. Compression set and tensile strength are the main properties usually improved by the post-cure stage.

Table 2: Chemical Resistance Guide

ChemicalResistance Capability
Mineral oils and greasesExcellent
FuelsExcellent
Hydraulic fluidsExcellent
Aliphatic hydrocarbonsExcellent
Aromatic hydrocarbonsFair to good
AlcoholsGood
AcidsPoor to fair
BasesPoor to fair

For a comprehensive guide on chemical resistances and recommendations for common rubber polymers including FKM rubber, see our guide at warco.com/chemical.

Table 3: Fluoroelastomer (FKM) Characteristics

CategoryPropertyPerformance
MechanicalAbrasion ResistanceGood
Impact ResistanceGood
Rebound RatingGood
Tear ResistanceGood
Flex Cracking ResistanceGood
EnvironmentalChemical ResistanceExcellent
Oil ResistanceOutstanding
Weather ResistanceOutstanding
Ozone ResistanceOutstanding
Oxidation ResistanceOutstanding
Sunlight ResistanceOutstanding
Application SpecificFlame ResistanceExcellent
Minimum Service TemperaturesGood
Maximum Service TemperaturesOutstanding
Gas PermeabilityVery Good
Radiation ResistanceGood

For more specific information about FKM rubber products and their characteristics, visit our webpage on FKM & Viton™ at warco.com/fkm-viton. Topics covered include

  • General Information
  • Physical Properties
  • Mechanical Properties
  • Chemical Resistances
  • And much more

Applications Ideally Suited to FKM Rubber

FKM’s exceptional properties make it an ideal choice for a wide range of applications across various industries, including but not limited to:

Aerospace

  • O-Rings: FKM O-rings are widely used in aircraft engines and systems due to their excellent chemical resistance and temperature stability.
  • Gaskets and Seals: FKM gaskets and seals are used in fuel systems, hydraulic systems, and landing gear systems.

Automotive

  • Fuel System Seals: FKM seals in fuel injectors, fuel pumps, and fuel tanks due to their outstanding resistance to fuels and oils.
  • Engine Seals: FKM gaskets and seals in engine components such as valve covers and oil pans due to their high-temperature stability.

Chemical Processing

  • Pump and Valve Seals: FKM seals and gaskets are used in pumps, valves, and reactors due to their excellent chemical resistance.
  • Flange Gaskets: FKM gaskets are used in chemical pipelines and reactors due to their outstanding chemical resistance.

Oil & Gas

  • Drilling Equipment Seals: FKM seals and gaskets are used in drilling equipment and valves due to their excellent chemical resistance and temperature stability.
  • Pipeline Seals: FKM seals are used in oil and gas pipelines due to their resistance to hydrocarbons and harsh environmental conditions.

Food Processing

FKM FDA approved compounds are suitable for use in food processing equipment where resistance to high temperatures and chemicals is required, including:

  • Gaskets and Seals: FKM gaskets and seals in food processing equipment such as mixers, blenders, and pumps.

FKM Rubber Products

This selection of FKM rubber products, including WARCO’s Fluorozone® Performance FKM and sheet rubber made with genuine Viton™. These products cover a diverse range of applications, especially those requiring superior chemical resistance, excellent heat stability, and physical dynamic properties. Many of these products are available as rubber sheet, rubber extrusions, or custom molded rubber.

FKM ProductPrimary Feature
Fluorozone® Premium FKMExceptional chemical & weathering resistances
Fluorozone® Blue Premium FKMApplication-specific premium grade variation (blue)
Fluorozone® Brown Premium FKMApplication-specific premium grade variation (brown)
Fluorozone® Mil-Spec FKMMeets AMS 3216G, MIL-R-83248C Type II Class 1 specifications
Fluorozone® FDA FKMContaining FDA approved ingredients per 21 CFR 177.2600
Viton™ A Sheet
Exceptional chemical & weathering resistances
Viton™ A Brown SheetApplication-specific A type variation (brown)
Viton™ B SheetExcellent elastic retention under duress & temperature
Viton™ A FDA SheetContaining FDA approved ingredients per 21 CFR 177.2600
Viton™ A Specification Grade SheetMeets AMS 3216G, MIL-R-83248C Type II Class 2 specifications

Common Questions about FKM

Throughout our extensive 114-year history of formulating and manufacturing rubber products for diverse applications, we have compiled a list of commonly encountered questions pertaining to Fluoroelastomers. Should you have any additional questions about rubber applications please contact us at sales@warco.com or 714-532-3355.

Q1: What is the temperature range of FKM?
FKM has a temperature range of -20°F to 500°F. However, specialty formulated grades can adjust this maximum or minimum range.

Q2: What is FKM’s chemical resistance?
FKM exhibits excellent resistance to mineral oils, greases, fuels, hydraulic fluids, and aliphatic hydrocarbons. However, its resistance to acids and bases is poor to fair.

Q3: Is FKM food safe or FDA approved?
Yes, certain FKM compounds are mixed using FDA approved ingredients per 21 CFR 177.2600 for use in food processing applications where resistance to high temperatures and various chemicals is required.

Q4: What is the difference between Viton™ A and Viton™ B?
Viton™ A has a better compression set, while Viton™ B exhibits greater chemical resistance and retains flexibility better after dry heat aging.

Q5: What is the shelf life of FKM?
FKM rubber products have an expected shelf life of 20 years if stored properly in a cool, dry, and dark environment away from direct sunlight. Learn more at warco.com/shelf-life.

Q6: How does FKM compare to other materials like EPDM, Nitrile, Neoprene, or Silicone?
FKM provides superior chemical resistance compared to nitrile, neoprene, and silicone. While nitrile is less expensive and offers good resistance to petroleum-based oils and fuels, FKM has a wider temperature range and better chemical resistance. Neoprene is less resistant to heat and chemicals compared to FKM. Silicone has a higher flexibility but lower chemical resistance compared to FKM. EPDM is less resistant to hydrocarbons and high temperatures, when compared to FKM.

Takeaways

Fluoroelastomers offer exceptional chemical resistance and thermal stability, making them a preferred choice in various demanding industrial applications. Understanding the characteristics, applications, and limitations of FKM is crucial in selecting the right sealing solution for specific requirements. Whether it’s in aerospace, automotive, or chemical processing, FKM remains a reliable choice for sealing solutions.

Unlike many other rubber manufacturers that depend upon external laboratories, mixing and testing facilities, WARCO can develop compounds, mix materials, thoroughly test and process your rubber products in a single facility. Our wealth of experience in material design and engineering, unique manufacturing processes, and tight control over each step of production, are among the key contributors to how WARCO remains America’s Choice.

If you have any questions, email your questions to sales@warco.com, or contact us directly at (714) 532-3355.

¹Note that “Viton™” is currently a registered trademark of the Chemours Company. Should your application specify Chemours Viton™ as a requirement, request a certification from your manufacturer or look for the “Made with Viton™” sticker that identifies an official brand licensee.