O-rings Material Selection

O-rings and seals are used in a wide range of industries to help you tightly seal the connections in pipes, tubes, and other elements of complex hydraulic and pneumatic systems. Several materials are widely used in O-ring production, each offering distinct advantages based on the requirements of the application:

NBR

NBR - Nitrile Rubber, also called Buna-N, is a copolymer of butadiene and acrylonitrile. Nitrile is recommended for: general purpose sealing,petroleum oils and fluids, water, silicone greases and oils,di-ester based lubricants (such as MIL-L-7808),and ethylene glycol based fluids (Hydrolubes). It is not recommended for: halogenated hydrocarbons, nitro hydrocarbons (such as nitrobenzene and aniline), phosphate ester hydraulic fluids (Skydrol, Cellulube, Pydraul), ketones (MEK, acetone), strong acids, ozone, and automotive brake fluid. Its temperature range is -30° to 107°C, although this would involve more than one compound and would depend upon the stress state of the component in service.

Nitrile rubber is one of the most common materials used for O-rings. It is ideal for applications where oil, grease, and fuels are present. NBR provides excellent resistance to petroleum-based fluids and has good mechanical properties, making it ideal for automotive, fuel systems, and industrial sealing applications.

• Best For: Fuel systems, automotive seals, general industrial use.
• Advantages: Excellent oil resistance, affordable, good wear resistance.
• Limitations: Not suitable for high temperatures or aggressive chemicals.

EPDM

EPDM - Ethylenepropylene rubber is an elastomer prepared from ethylene and propylene monomers. EPDM (Ethylene-Propyline-Diene-Monomer) is well known for its excellent ozone, weathering and aging resistance. It also has excellent water and stream resistance, maintains its flexibility at low temperatures, features excellent resistance to alkalis, acids and oxygenated solvents, and is very color stable. It is not recommended for resistance to oil, gasoline and hydrocarbon solvents. EPDM is found in a wide range of applications and is excellent for outdoor use.

EPDM O-rings are excellent for applications requiring resistance to water, steam, and weathering. They perform well in outdoor and automotive applications and are highly resistant to ozone, UV light, and extreme weather conditions.

• Best For: HVAC systems, outdoor equipment, water-based applications.
• Advantages: Excellent weathering, ozone, and UV resistance.
• Limitations: Not suitable for oils or fuels.

FKM

FKM - This is a fluoroelastomer of the polymethylene type having substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups on the polymer chain. Viton® and Fluorel® are the most common trade names. FKM is recommended for: petroleum oils, di-ester based lubricants, silicate ester based lubricants (such as MLO 8200, MLO 8515, OS-45), silicone fluids and greases, halogenated hydrocarbons, selected phosphate ester fluids, and some acids. It is not recommended for: ketones, Skydrol 500, amines (UDMH), anhydrous ammonia, low molecular weight esters and ethers, and hot hydrofluoric and chlorosulfonic acids. Its temperature range is -29° to 232°C (This extended range would require special grades and would limit use on each end of the range.).

FKM O-rings, made from a fluorocarbon elastomer, are highly resistant to high temperatures, chemicals, and oils. They are commonly used in applications where harsh environments are encountered, such as chemical processing, automotive engines, and aerospace.

• Best For: Chemical processing, high-temperature applications, automotive engines.
• Advantages: High resistance to oils, fuels, and chemicals; high-temperature stability.
• Limitations: Higher cost compared to other materials.

VMQ

VMQ - This is the most general term for silicone rubber. Silicone rubber can be designated MQ, PMQ, and PVMQ, where the Q designates any rubber with silicon and oxygen in the polymer chain, and M, P, and V represent methyl, phenyl, and vinyl substituent groups on the polymer chain. This elastomer is used only for static seals due to its poor mechanical properties. Its temperature range is -55° to 250°C).

Silicone O-rings offer excellent flexibility and high-temperature resistance, making them ideal for medical, food processing, and high-temperature sealing applications. They are often used in environments requiring sterilization or exposure to extreme temperatures.

• Best For: Food processing, medical devices, high-temperature applications.
• Advantages: High flexibility, high-temperature resistance, biocompatibility.
• Limitations: Limited resistance to oils and fuels.

The information contained herein is extracted from data we believe to be reliable. However, because of variable service conditions over which we have no control, we do not in any way make any warranty, either express or implied, as to the properties of any materials or as to the performance of any such materials in any particular application, and we hereby expressly disclaim any responsibility for the accuracy of any of the information set forth herein.