Viton^TM O-Rings: FKM Material, Properties, Grades, Applications, and Best Recommendations

Viton^TM O-rings are widely used in demanding sealing applications where ordinary rubber materials may fail under heat, oil, fuel, or chemical exposure. In many industries, the term “Viton O-rings” is commonly used to describe FKM O-rings, also known as fluoroelastomer O-rings or fluorocarbon rubber O-rings.

However, it is important to understand that Viton^TM is a brand name, not the generic material name. The generic material is FKM, and Viton^TM is one of the most well-known branded FKM materials. Because Viton^TM has become highly recognized in the sealing industry, many users refer to FKM O-rings as Viton O-rings in daily communication.

At Katon, our FKM O-ring series are organized around the major fluoroelastomer performance classes that customers commonly recognize through Viton^TM grade names, including general-purpose FKM, enhanced chemical- and fuel-resistant FKM, low-temperature FKM, and extreme chemical-resistant FKM.

1. What Are Viton^TM O-Rings?

FKM O-Rings, commonly known as Viton^TM O-rings, are O-rings made from FKM fluoroelastomer material. FKM is a high-performance synthetic rubber known for its excellent resistance to heat, oils, fuels, lubricants, hydraulic fluids, and many chemicals.

In industrial sealing, O-rings must maintain their shape and elasticity while being exposed to pressure, temperature changes, and aggressive media. FKM O-rings are selected because they provide a much higher level of durability than many standard elastomers such as NBR, EPDM, or natural rubber.

Although “Viton^TM O-ring” is a common search term, the technically correct material name is FKM O-ring. Viton^TM is a registered brand of FKM material, and people often use “Viton” as a general term when they are actually looking for FKM rubber seals.

Understanding Viton^TM and FKM

FKM is the international material designation for fluoroelastomer rubber. Viton^TM is a branded FKM product family that includes many different grades, such as:

• Viton^TM A
• Viton^TM B
• Viton^TM F
• Viton^TM Type-GLT
• Viton^TM Extreme / ETP

Each material grade is designed for different sealing environments. Some focus on general oil and heat resistance, some offer better fuel and chemical resistance, while others are developed for low-temperature flexibility or extreme chemical exposure.

Common Viton^TM Material Types

• Viton^TM A is a general-purpose FKM material. It is commonly used for standard oil, fuel, lubricant, and high-temperature sealing applications. It is often considered the basic or standard FKM grade.
• Viton^TM B offers improved chemical resistance compared with Viton^TM A. It is often used where better resistance to fuels, acids, and more aggressive fluids is required.
• Viton^TM F is designed for enhanced resistance to fuels, oxygenated fuels, and certain aggressive chemical environments. It is commonly selected for automotive fuel systems and applications involving modern fuel blends.
• Viton^TM GLT is developed for improved low-temperature flexibility. Standard FKM can become less flexible in cold conditions, but GLT-type materials help improve sealing performance at lower temperatures.
• Viton^TM GFLT combines improved low-temperature performance with better fuel and chemical resistance. It is useful when both low-temperature sealing and fuel resistance are important.
• Viton^TM Extreme / ETP is designed for aggressive chemical environments where conventional FKM grades may not be sufficient. They offer broader resistance to chemicals such as low-molecular-weight ketones, aldehydes, esters, caustics, and amines.

For Katon products, the material positioning can be understood as follows:

• Katon 1000 Series FKM is equivalent to general-grade FKM, commonly compared with Viton^TM Type A.
  Katon 2000 Series is equivalent to higher-performance FKM grades, commonly compared with Viton^TM B and Viton^TM F.
  Katon 3000 Series is equivalent to low-temperature FKM, commonly compared with Viton^TM GLT.
  Katon 5000 Series is equivalent to extreme chemical-resistant FKM, commonly compared with Viton^TM Extreme ETP.

 

2. Key Properties of Viton^TM O-Rings

FKM O-Rings, commonly known as Viton^TM O-rings, are chosen because they provide a strong balance of heat resistance, chemical resistance, compression set performance, and long service life. These properties make FKM O-rings suitable for applications where sealing failure could lead to leakage, downtime, contamination, or equipment damage.

Excellent Oil, Fuel, and Lubricant Resistance

Viton^TM (FKM) O-rings are especially well known for resistance to:

• Petroleum oils
• Mineral oils
• Diesel fuel
• Gasoline
• Lubricating oils
• Greases
• Many hydraulic fluids
• Many hydrocarbon-based chemicals

This is why FKM O-rings are widely used in automotive, oil and gas, fuel handling, and industrial equipment applications.

Chemical Resistance

FKM materials resist many chemicals better than standard elastomers. Compared with NBR or silicone, FKM offers superior resistance to many fuels, oils, solvents, and industrial fluids.

However, chemical resistance depends strongly on the exact FKM grade. A general-purpose FKM such as a Viton^TM A-type material (Katon 1000 Series) may be suitable for oils and standard fuels, while more aggressive chemicals may require Viton^TM B, Viton^TM F, GFLT, or Extreme ETP-type materials (Katon 2000,3000,5000 Series).

Low Compression Set

Compression set refers to the ability of an O-ring to return to its original shape after being compressed. A low compression set means the O-ring can maintain sealing force over time.

FKM O-rings usually offer good compression set resistance, especially in high-temperature environments. This is important for long-term sealing applications where the O-ring remains compressed for months or years.

Good Aging, Weather, and Ozone Resistance

FKM O-rings have excellent resistance to aging, ozone, sunlight, and general weather exposure. This makes them suitable for outdoor equipment, automotive systems, aerospace applications, and industrial machinery exposed to harsh environments.

Limitations of Viton^TM O-Rings

Although Viton^TM O-rings are highly durable, they are not the best choice for every environment. Standard FKM is generally not recommended for:

• Steam
• Hot water
• Ketones
• Some polar solvents
• Certain amines
• Some strong bases
• Low-temperature dynamic sealing without a special grade

For these conditions, another elastomer such as EPDM, silicone, FFKM, or a special FKM grade may be more suitable.

 

3. Temperature Range and Performance

Standard FKM Temperature Range

General-purpose FKM O-rings, such as materials comparable to Viton^TM A, are commonly used in applications where the temperature is above −20°C and below +200°C. This range is suitable for many automotive, industrial, and oil-resistant sealing applications.

High-Temperature Performance

At elevated temperatures, many rubber materials lose strength, harden, crack, or suffer from excessive compression set. FKM performs better than many common elastomers under heat, making it suitable for engine compartments, hot oil systems, compressors, pumps, and chemical processing equipment.

For continuous high-temperature operation, it is important to select the right compound and confirm whether the O-ring will be exposed to air, oil, fuel, chemicals, pressure, or dynamic movement.

Low-Temperature Performance

Standard FKM materials may become less flexible at low temperatures. This can reduce sealing performance, especially in dynamic applications or systems with cold-start conditions.

Low-temperature grades, such as materials similar to Viton^TM GLT or Viton^TM GFLT are often preferred. These grades are designed to improve flexibility and sealing reliability in colder environments.

Factors That Affect O-Ring Performance

Temperature rating alone does not determine whether FKM O-ring will work in an application. Performance can be affected by:

• Fluid or chemical compatibility
• Continuous vs peak temperature
• Pressure level
• Static or dynamic sealing
• Groove design
• O-ring hardness
• Compression percentage
• Exposure time
• Frequency of temperature cycling
• Cleaning agents or process chemicals

For critical sealing applications, it is always recommended to review both the operating environment and the exact FKM compound before selecting an O-ring.

 

4. Common Applications

FKM O-rings are used in industries where seals must withstand aggressive media, high temperatures, and long service life requirements. Their strong resistance to oils, fuels, and chemicals makes them one of the most widely used high-performance rubber sealing materials.

Automotive Applications

In the automotive industry, FKM O-rings are commonly used in:

• Fuel systems
• Fuel injectors
• Engines
• Transmissions
• Turbocharger systems
• Oil pumps
• Valve seals
• Sensors
• Emission control systems

Modern vehicles often use complex fuels, lubricants, and high-temperature engine environments. FKM O-rings help maintain reliable sealing where standard NBR or silicone materials may not provide enough resistance.

Oil and Gas Applications

Oil and gas environments often involve hydrocarbons, pressure, temperature, and aggressive fluids. Viton^TM (FKM) O-rings are used in sealing systems for:

• Valves
• Pumps
• Compressors
• Downhole tools
• Drilling equipment
• Pipeline components
• Fuel transfer systems

For harsher hydrocarbon environments, higher-grade FKM materials such as Katon 2000 series or Katon 5000 series materials may be selected.

Chemical Processing

Chemical processing equipment requires seals that can resist aggressive fluids while maintaining dimensional stability. Viton^TM O-rings are commonly used in:

• Chemical pumps
• Valves
• Mixers
• Pipelines
• Reactors
• Filtration equipment
• Dosing systems

For general chemical resistance, standard FKM may be enough. For more aggressive chemicals, a higher-performance FKM grade or FFKM may be required.

Aerospace Applications

Aerospace sealing applications require high reliability, fuel resistance, temperature resistance, and long-term performance. FKM O-rings are used in:

• Fuel systems
• Hydraulic systems
• Engine components
• Actuation systems
• High-performance sealing assemblies

Depending on the operating temperature and fluid exposure, low-temperature FKM or higher fuel-resistant FKM may be required.

Industrial Machinery

In industrial equipment, Viton^TM (FKM) O-rings are used where seals are exposed to oil, grease, heat, and mechanical stress. Common applications include:

• Hydraulic systems
• Pneumatic systems
• Gearboxes
• Compressors
• Pumps
• Motors
• High-temperature machinery
• Lubrication systems

Because FKM O-rings offer durability and long service life, they can help reduce maintenance frequency and unplanned downtime.

5. Viton^TM (FKM) vs Other O-Ring Materials

Choosing the right O-ring material depends on the application environment. FKM is excellent for heat, oils, fuels, and many chemicals, but other elastomers may perform better in water, steam, low-temperature, or cost-sensitive applications.

Viton^TM (FKM) vs NBR O-Rings

NBR, also known as nitrile rubber, is widely used for oil-resistant sealing. It is cost-effective and performs well in many general oil and hydraulic applications.

Compared with NBR, FKM O-rings offer:

• Better high-temperature resistance
• Better fuel resistance
• Better chemical resistance
• Better aging and ozone resistance
• Longer service life in harsh environments

However, NBR is usually more economical and may be sufficient for standard oil applications where high temperature or aggressive chemicals are not present.

Viton^TM (FKM)  vs EPDM O-Rings

EPDM O-rings are excellent for water, steam, weathering, brake fluids, and many outdoor applications. However, EPDM is generally not suitable for petroleum oils and fuels.

Compared with EPDM, FKM O-rings are much better for:

• Oils
• Fuels
• Hydrocarbons
• Lubricants
• High-temperature oil environments

However, EPDM is usually better for:

• Hot water
• Steam
• Coolants
• Weather sealing
• Some water-based chemicals

If the application involves oil or fuel, FKM is often preferred. If the application involves steam or hot water, EPDM is often a better choice.

Viton^TM (FKM)  vs Silicone O-Rings

Silicone O-rings are known for excellent flexibility over a wide temperature range, especially at low temperatures. They are often used in food, medical, and low-temperature applications.

Compared with silicone, FKM O-rings generally provide:

• Better mechanical strength
• Better abrasion resistance
• Better fuel and oil resistance
• Better chemical resistance
• Better sealing durability in industrial applications

However, silicone usually performs better in very low-temperature environments and may be selected where flexibility is more important than chemical or mechanical resistance.

Viton^TM vs FFKM O-Rings

FFKM, or perfluoroelastomer, is one of the highest-performance O-ring materials available. It offers exceptional chemical and temperature resistance, often used in semiconductor, pharmaceutical, chemical, and extreme industrial applications.

Compared with FFKM, Viton^TM O-rings are:

• More cost-effective
• Easier to source
• Suitable for many demanding applications
• A practical choice for oils, fuels, and many chemicals

However, FFKM provides better performance in extreme chemical environments, high-purity processes, and very high-temperature applications. When standard FKM is not enough, a material such as Viton^TM Extreme ETP-type FKM may provide an intermediate solution before moving to FFKM.

6. How to Choose the Right Viton^TM (FKM)  O-Ring

Selecting the correct FKM O-ring requires more than choosing the size. The right material grade, hardness, temperature capability, and chemical compatibility are all important for long-term sealing performance.

Check Fluid and Chemical Compatibility

The first step is to identify all fluids and chemicals that will contact the O-ring. This includes not only the main operating fluid but also cleaning agents, additives, lubricants, fuels, and possible contaminants.

For standard oils and fuels, general FKM may be suitable. For aggressive fuels, oxygenated fuels, acids, or mixed chemicals, higher-performance FKM grades may be required.

Confirm the Temperature Range

Temperature should be evaluated as both continuous operating temperature and peak temperature. A seal that can survive a short temperature spike may not perform well under continuous exposure at the same temperature.

For normal high-temperature applications, general FKM may be suitable. For very high-temperature operation, a special FKM compound should be selected. For low-temperature environments, GLT or GFLT-type FKM may be required.

Consider Hardness

O-ring hardness is usually measured in Shore A durometer. Common FKM O-ring hardness values include 70 Shore A, 75 Shore A, and 90 Shore A.

A softer O-ring may seal better under low pressure or uneven surfaces, while a harder O-ring may resist extrusion better in high-pressure applications. The correct hardness depends on the groove design, pressure, gap clearance, and sealing movement.

Static vs Dynamic Sealing

Static applications involve little or no movement after installation. Dynamic applications involve movement, sliding, rotation, or repeated pressure cycling.

For dynamic sealing, material selection becomes more critical because friction, wear, lubrication, and temperature buildup can affect performance. Low-temperature flexibility and compression set are also important in dynamic applications.

Evaluate Required Certifications

Some industries require specific approvals or certifications. Depending on the application, FKM O-rings may need to meet requirements such as:

• FDA
• USP Class VI
• Aerospace specifications
• Automotive specifications
• Oil and gas standards
• Customer-specific material approvals

Not all FKM compounds meet the same certifications, so this should be confirmed before ordering.

 

7. Pros and Cons

FKM O-rings offer many advantages, but they also have limitations. Understanding both helps prevent incorrect material selection.

Pros	Cons
Excellent heat resistance Strong oil and fuel resistance Good chemical resistance Low compression set Long service life Good aging and ozone resistance Cost-effective compared with FFKM	Poor resistance to steam and hot water Limited low-temperature flexibility Not suitable for some polar solvents Higher cost than standard rubber

Grade selection is important
Not all FKM materials are the same. Choosing the wrong FKM grade can lead to premature failure, swelling, hardening, or leakage.

 

FKM O-rings Recommendation

aton offers different FKM and fluoroelastomer O-ring series for various sealing environments. These products are designed for applications where customers commonly request Viton™ O-rings, FKM O-rings, or specific fluoroelastomer performance classes.

Katon Series	Common Performance Class	Best For	Key Features	Recommended Applications
Katon 1000 Series FKM O-Rings	General-grade FKM, commonly associated with Viton™ Type A performance	Standard oil, fuel, lubricant, and high-temperature sealing applications	Provides a strong balance of heat resistance, oil resistance, fuel resistance, and long-term sealing performance. Suitable for general industrial and automotive sealing applications where reliable FKM performance is required.	Automotive engines, oil pumps, fuel systems, gearboxes, hydraulic systems, industrial machinery, lubrication systems
Katon 2000 Series FKM O-Rings	Enhanced fuel- and chemical-resistant FKM, commonly associated with Viton™ B and Viton™ F-type performance	Improved fuel resistance, chemical resistance, and harsh hydrocarbon environments	Designed for more demanding sealing conditions than standard FKM. Suitable for applications requiring enhanced resistance to fuels, oils, additives, and certain chemicals.	Automotive fuel systems, fuel injectors, modern fuel blends, oil and gas equipment, chemical pumps, valves, compressors, hydrocarbon processing equipment
Katon 3000 Series Low-Temperature FKM O-Rings	Low-temperature FKM, commonly associated with Viton™ GLT-type performance	Low-temperature sealing with FKM oil, fuel, and heat resistance	Designed for applications where standard FKM may become too stiff at low temperatures. Provides improved low-temperature flexibility while maintaining the main advantages of FKM rubber.	Cold-start automotive systems, aerospace fuel systems, outdoor industrial equipment, low-temperature oil sealing, fuel systems exposed to cold environments, precision sealing applications requiring flexibility
Katon 5000 Series Extreme Chemical-Resistant FKM O-Rings	Extreme chemical-resistant fluoroelastomer, commonly associated with Viton™ Extreme ETP-type performance	Aggressive chemical environments and applications requiring broader chemical resistance	Designed for applications where conventional FKM may not provide enough resistance to aggressive chemicals. A cost-effective option for demanding chemical sealing applications where FFKM may not be required.	Chemical processing equipment, aggressive fluid handling, pumps and valves, industrial chemical systems, mixed chemical environments, applications where FFKM is too costly

 

Conclusion

Viton™ O-rings are widely used for sealing applications involving heat, oil, fuel, and chemicals. While Viton™ is a brand name, many customers use “Viton O-rings” when referring to FKM O-rings or fluoroelastomer rubber seals.

Choosing the right FKM grade depends on the application. Katon 1000 Series is suitable for general-purpose FKM applications, Katon 2000 Series for improved fuel and chemical resistance, Katon 3000 Series for low-temperature sealing, and Katon 5000 Series for extreme chemical-resistant applications.

By selecting the right Katon FKM O-ring series, customers can improve sealing reliability, reduce maintenance needs, and achieve longer service life in demanding industrial, automotive, oil and gas, aerospace, and chemical processing environments.

 

Trademark note: Viton™ is a trademark of The Chemours Company FC, LLC. References to Viton™ are used only to describe commonly recognized FKM performance classes.