O-Ring Materials for Check Valves: Specifications & Compatibility

The O-ring material used in a check valve affects sealing performance, chemical compatibility, and how the valve performs under different operating conditions. Selecting the right material requires evaluating the fluids or gases in your system, operating temperatures, material hardness, and application requirements.

Smart Products offers seven O-ring material options for our low-pressure, low-flow check valves. Use the comparison chart and specifications below to evaluate available materials and identify options for further testing in your application.

For optimal valve performance, it is important to discuss all liquids/gasses coming into contact with the valves, as well as environmental conditions with a Product & Application Specialist. Once we select a plastic, o-rings, and pressure requirements, we can create test samples based on specific project criterion.

Compare O-Ring Materials for Your Application

Each O-ring material has different temperature limits, chemical resistance, and mechanical properties. The following chart provides a starting point for comparing the materials available from Smart Products.

O-Ring Material	Temperature Range	Available Durometer	Common Compatibility
Buna-N (Nitrile)	-70°F to 250°F	50–70	Petroleum oils, fuels, water, glycol fluids, dilute acids, alkali and salt solutions
EPDM	-70°F to 500°F	50–70	Water, steam, ozone, certain acids and bases
Viton® (FKM)	-15°F to 400°F	60–75	Petroleum fuels, oils, selected chemicals, ozone, weathering, aging resistance
Silicone	-175°F to 500°F	50–70	Dry heat, ozone, weathering
Fluorosilicone	-100°F to 350°F	70 standard; 60 on select models	Hydrocarbon fuels, jet fuel, low-temperature environments, ozone, UV weathering
Aflas®	-15°F to 450°F	80	Steam, amines, petroleum fluids, phosphate esters, hot water
Kalrez®	-15°F to 100°F	80–90	Selected aggressive chemicals, chlorinated hydrocarbons, high-temperature environments, water and steam

What Should You Consider When Selecting an O-Ring Material?

O-ring selection involves more than identifying a material that can withstand a particular temperature or fluid. Several factors can affect sealing performance and the suitability of an O-ring for your check valve.

Fluid and Chemical Compatibility

Start by identifying every liquid or gas that may contact the O-ring during operation. This includes process fluids, cleaning solutions, and other substances the valve may encounter.

Different elastomers respond differently to chemical exposure. A material compatible with one type of oil, solvent, or cleaning agent may not perform the same way with another.

Chemical concentration, temperature, and exposure duration can also affect compatibility. Use published material information to narrow your options, then verify compatibility under actual operating conditions.

Operating Temperature

Every O-ring material has a recommended temperature range. Exposure outside that range can affect flexibility, hardness, and the material’s ability to maintain a seal.

For example, some materials retain flexibility at very low temperatures, while others offer greater resistance to elevated temperatures.

Keep in mind that an O-ring’s temperature rating does not establish the temperature limits of the complete check valve. The plastic valve body, spring, and other components must also be suitable for the operating environment.

Durometer (Material Hardness)

Durometer measures the hardness of an O-ring, typically using the Shore A scale. Lower numbers indicate softer materials, while higher numbers indicate harder materials.

Softer O-rings generally conform more easily to sealing surfaces. Harder materials resist deformation differently and may be more appropriate for certain operating conditions.

In a spring-loaded check valve, O-ring hardness can influence how the sealing components interact. Material and durometer availability may also depend on the valve series and required opening pressure.

Sealing and Mechanical Performance

Material properties such as compression set resistance, resilience, wear resistance, and permeation resistance can affect O-ring performance over time.

These properties are especially important when evaluating applications involving repeated valve operation, extended compression, or exposure to different gases and fluids.

See the O-Ring Mechanical Properties Comparison below for a general comparison of available materials.

Application-Specific Requirements

Some applications have additional requirements related to sterilization, material documentation, or environmental exposure.

For example, certain medical and food-contact applications may require specific material compliance documentation. Other applications may involve gamma sterilization, steam exposure, or aggressive cleaning agents.

Requirements should be evaluated for the specific O-ring compound and complete valve assembly rather than the general material family alone.

For additional information about sealing materials and valve performance, visit our O-Ring FAQs.

O-Ring Material Specifications

The following sections provide detailed information about the seven O-ring materials offered by Smart Products, including available hardness, temperature ranges, compatible media, and check valve series.

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Buna-N (Nitrile) O-Rings

Buna-N, also known as nitrile rubber or NBR, is an economical and versatile O-ring material used in a wide range of applications. Its resistance to petroleum-based oils and fuels makes it a common choice for general-purpose sealing applications.

Performance Considerations

Buna-N has good ratings for wear resistance, compression set resistance, short-term resilience, and permeation resistance in Smart Products’ mechanical properties comparison.

Its combination of properties makes it a useful starting point for applications involving compatible oils, fuels, and other general-purpose fluids.

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EPDM (Ethylene-Propylene) O-Rings

EPDM is commonly considered for applications involving water, steam, and exposure to environmental conditions such as sunlight and ozone. It also offers resistance to certain chemicals and is available in multiple compound options.

Performance Considerations

EPDM has good ratings for wear resistance, compression set resistance, and permeation resistance, with moderate short-term resilience.

Smart Products offers peroxide-cured and sulfur-cured EPDM compounds, depending on application requirements. Peroxide-cured compounds may be preferred for applications involving ozone exposure.

Certain EPDM compounds with USP Class VI testing documentation may be available upon request. These options typically require a higher durometer, such as 60 or 70 Shore A.

The appropriate compound should be confirmed based on chemical exposure, environmental conditions, and applicable documentation requirements.

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Viton® (FKM) O-Rings

Viton® is a fluoroelastomer material commonly considered for applications involving petroleum fuels, oils, and certain chemicals. Its resistance to elevated temperatures makes it an option for applications where general-purpose elastomers may not provide the required performance.

Performance Considerations

Viton® has good wear resistance and excellent ratings for compression set resistance and permeation resistance in Smart Products’ comparison. Its short-term resilience is rated moderate.

Although Viton® offers broad resistance to many fluids, compatibility varies by chemical and compound formulation. Buyers should confirm suitability for the specific media and temperatures involved.

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Silicone O-Rings

Silicone is a flexible O-ring material that maintains useful properties across a broad temperature range. Its softness and ability to conform to sealing surfaces make it an option for check valve applications where sealing behavior is a primary consideration.

Performance Considerations

Silicone’s flexibility and conformability can offer sealing advantages in certain valve configurations. However, sealing performance depends on the O-ring compound, valve components, operating conditions, and required opening pressure.

In Smart Products’ mechanical properties comparison, silicone has excellent ratings for compression set resistance and permeation resistance, but poor ratings for wear resistance and short-term resilience.

Certain silicone compounds with applicable food-contact or USP Class VI documentation may be available upon request. Buyers should confirm the exact compound and documentation required for their application.

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Fluorosilicone O-Rings

Fluorosilicone combines a broad operating temperature range with resistance to certain fuels, oils, and chemicals. Its low-temperature flexibility makes it particularly useful to consider for applications involving cold environments and compatible hydrocarbon fluids.

Performance Considerations

Fluorosilicone offers the lowest published minimum temperature among Smart Products’ listed O-ring materials.

Its mechanical properties are rated moderate for compression set resistance and short-term resilience, and poor for wear resistance and permeation resistance.

These characteristics should be considered when evaluating applications involving repeated movement, extended compression, or permeation-sensitive fluids and gases.

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Aflas® O-Rings

Aflas® is a fluoroelastomer material considered for demanding applications involving elevated temperatures, steam, petroleum fluids, and certain chemicals.

Its chemical resistance characteristics make it an option when other elastomer materials may not be suitable for the operating environment.

Performance Considerations

Aflas® is available from Smart Products in an 80 Shore A durometer, making it harder than many of the standard O-ring options listed on this page.

Due to the material and available valve configurations, Smart Products does not offer Aflas® O-rings with spring opening pressures below 0.5 PSI.

Buyers should confirm the required opening pressure, chemical compatibility, and valve configuration before selecting this material.

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Kalrez® O-Rings

Kalrez® is a perfluoroelastomer (FFKM) material designed for demanding environments involving high temperatures and selected aggressive chemicals.

It is generally a higher-cost material option, but may warrant consideration when chemical exposure or temperature requirements limit the suitability of other elastomers.

Performance Considerations

Kalrez® has good ratings for wear resistance, compression set resistance, and permeation resistance in Smart Products’ comparison. Its short-term resilience is rated moderate.

Kalrez® is available in harder durometers than many other listed materials. Smart Products does not offer Kalrez® O-rings with spring opening pressures below 0.5 PSI.

Although the published material temperature range extends to 615°F, this does not represent the operating temperature limit of the complete check valve assembly.

Specific chemical compatibility, compound selection, and operating conditions must be verified before use.

O-Ring Mechanical Properties Comparison

In addition to chemical compatibility and temperature limits, mechanical properties can influence how an O-ring performs in a check valve.

Four properties are useful when comparing materials:

• Wear Resistance: The material’s ability to resist surface damage caused by friction or repeated contact.
• Compression Set Resistance: The ability to recover after being compressed for an extended period, which can affect long-term sealing.
• Short-Term Resilience: The ability to return to its original shape after temporary deformation.
• Permeation Resistance: The ability to limit the passage of gases or fluids through the O-ring material.

The following table summarizes Smart Products’ published qualitative material ratings.

Material	Wear Resistance	Compression Set Resistance	Short-Term Resilience	Permeation Resistance
Buna-N	Good	Good	Good	Good
EPDM	Good	Good	Moderate	Good
Viton®	Good	Excellent	Moderate	Excellent
Silicone	Poor	Excellent	Poor	Excellent
Flourosilicone	Poor	Moderate	Moderate	Poor
Aflas®	N/A	N/A	N/A	N/A
Kalrez®	Good	Good	Moderate	Good

Gamma Sterilization Testing Results

Certain check valve applications involve sterilization requirements that may affect O-ring material selection.

Smart Products has published the following results for gamma radiation exposure at a dose of 39.9 kGy. The results describe observed visual and functional effects on the tested materials.

Material	Visual Effects	Functional Effects	Grade
Buna-N	None	None	A
EPDM	None	Enlarged	C
Viton®	None	Enlarged, deformed	C
Silicone	None	None	A
Flourosilicone	None	None	A
Aflas®	N/A	N/A	N/A
Kalrez®	N/A	N/A	N/A

These results provide a reference for evaluating material response to the stated gamma radiation exposure. They do not establish suitability for all sterilization processes, repeated sterilization cycles, or complete valve assemblies.

Gamma radiation and steam autoclaving are different sterilization methods. Compatibility with one method does not automatically establish compatibility with the other.

Customers should verify material performance and any applicable sterilization requirements under their intended operating conditions.

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Evaluate O-Ring and Check Valve Material Compatibility

O-ring selection is only one part of determining whether a check valve is suitable for an application. The plastic valve body and other wetted components must also be compatible with the fluids, temperatures, and operating conditions involved.

Explore our Plastic Body Materials resource to compare additional material specifications.

Have Your Check Valve Specifications Ready?

Smart Products offers a range of O-ring materials and configurations for low-pressure, low-flow check valves. If you’re evaluating material options, share your application’s fluid or gas, operating temperature, required opening pressure, and other specifications with our team to discuss available options.