What are seals made from
Key Material Requirements for Seals
Before delving into specific materials, it’s important to understand the key requirements that guide material selection for hydraulic and pneumatic seals:
Durability: The material must resist wear and tear caused by friction and pressure.
Elasticity: Flexibility and the ability to return to original shape are vital for effective sealing.
Temperature Resistance: Seals must withstand extreme temperatures, whether hot or cold.
Chemical Compatibility: Resistance to oils, fuels, solvents, and other chemicals is critical in many applications.
Low Permeability: For pneumatic seals, preventing air leakage is essential.
Common Materials Used in Hydraulic and Pneumatic Seals
Acrylonitrile Butadiene Rubber (NBR)
Properties: Nitrile rubber is one of the most widely used materials for seals due to its excellent resistance to petroleum-based oils and fuels. It also offers good abrasion resistance and a broad operating temperature range (-40°C to 120°C).
Applications: NBR is commonly used in hydraulic systems, automotive applications, and industrial machinery.
Limitations: It is not suitable for use with ozone, sunlight, or certain chemicals such as ketones.
Ethylene Propylene Diene Monomer (EPDM)
Properties: EPDM is known for its excellent resistance to water, steam, and weathering. It is also compatible with certain chemicals and has a broad temperature range (-50°C to 150°C).
Applications: EPDM seals are used in water systems, automotive cooling systems, and outdoor equipment.
Limitations: It is not compatible with petroleum-based oils and fuels.
Fluorocarbon Rubber (FKM)
Properties: Also known by the brand name Viton, FKM is valued for its high resistance to heat, oils, fuels, and chemicals. It can operate in temperatures up to 200°C.
Applications: FKM seals are used in aerospace, automotive, and chemical processing industries.
Limitations: FKM is relatively expensive and may not perform well in low-temperature environments.
Polyurethane (PU)
Properties: Polyurethane is known for its exceptional mechanical strength, wear resistance, and elasticity. It performs well in high-pressure environments and has a moderate temperature range (-40°C to 90°C).
Applications: PU seals are commonly found in hydraulic cylinders, heavy machinery, and construction equipment.
Limitations: It is less resistant to high temperatures and certain chemicals compared to other materials.
Polytetrafluoroethylene (PTFE)
Properties: PTFE, commonly known as Teflon, is a highly versatile material with exceptional chemical resistance and the ability to operate in extreme temperatures (-200°C to 260°C). It has a low coefficient of friction, making it ideal for dynamic applications.
Applications: PTFE is used in applications requiring high chemical resistance, such as in the pharmaceutical, chemical, and food industries.
Limitations: PTFE is less elastic than other materials, which can affect its sealing ability in dynamic conditions.
Silicone Rubber (VMQ)
Properties: Silicone rubber is highly flexible and resistant to extreme temperatures (-60°C to 200°C). It also has excellent weathering and ozone resistance.
Applications: VMQ seals are used in food processing, medical devices, and applications requiring high flexibility.
Limitations: Silicone has lower mechanical strength and wear resistance compared to other materials.
Less Common and Specialized Materials Used in Hydraulic and Pneumatic Seals
Aflas (TFE/P)
Properties: Aflas is a specialized fluoroelastomer with excellent resistance to heat, chemicals, and steam. It can operate in temperatures up to 200°C and is resistant to amines, bases, and acids.
Applications: Commonly used in chemical processing, oil and gas applications, and high-temperature environments.
Limitations: Aflas may not perform well in low-temperature conditions.
Ethylene Acrylate Rubber (AEM/Vamac®)
Properties: AEM, marketed under the trade name Vamac®, is known for its resistance to heat, ozone, and automotive fluids. It has a moderate temperature range (-30°C to 150°C).
Applications: Used in automotive applications, such as sealing components in engine and transmission systems.
Limitations: It is less resistant to certain aggressive chemicals and low temperatures.
Fluorosilicone Rubber
Properties: Fluorosilicone combines the properties of silicone with enhanced chemical resistance. It performs well in extreme temperatures (-60°C to 200°C) and offers resistance to fuels, oils, and solvents.
Applications: Commonly used in aerospace and automotive fuel systems.
Limitations: Fluorosilicone has lower mechanical strength and is more expensive than standard silicone.
Hydrogenated Nitrile Butadiene Rubber (HNBR)
Properties: HNBR is an upgraded form of nitrile rubber with improved temperature resistance (-40°C to 150°C) and enhanced resistance to oil, fuel, and wear.
Applications: Used in automotive systems, oil drilling, and industrial applications requiring durability.
Limitations: HNBR is less resistant to ozone and weathering compared to EPDM.
Natural Rubber (NR)
Properties: Natural rubber offers excellent elasticity, tensile strength, and resilience. It performs well in moderate temperatures and provides good abrasion resistance.
Applications: Found in shock absorbers, industrial machinery, and low-pressure systems.
Limitations: Natural rubber is susceptible to heat, oil, and weathering degradation.
Neoprene (CR)
Properties: Neoprene is a versatile material known for its resistance to oil, weathering, and ozone. It operates in a moderate temperature range (-40°C to 120°C).
Applications: Commonly used in refrigeration systems, automotive components, and marine applications.
Limitations: Neoprene is not suitable for use with strong acids or hydrocarbons.
Perfluoroelastomer (FFKM)
Properties: FFKM, also known as Kalrez, offers the highest chemical resistance among elastomers. It can withstand extreme temperatures (-10°C to 325°C) and aggressive chemicals.
Applications: Used in critical applications, such as semiconductor manufacturing and chemical processing.
Limitations: FFKM is extremely expensive, limiting its use to specialized industries.
Polyacrylate (ACM)
Properties: Polyacrylate rubber is resistant to heat, oil, and oxidation. It has a temperature range of -30°C to 150°C and offers good sealing performance in automotive applications.
Applications: Commonly used in transmission and power steering systems.
Limitations: ACM is less resistant to water and low temperatures.
Thermoplastic Elastomers (TPE)
Properties: TPE materials combine the elasticity of rubber with the processability of plastics. They offer good wear resistance and flexibility, with moderate chemical and temperature resistance.
Applications: TPE seals are often used in consumer products, medical devices, and low-pressure systems.
Limitations: Their performance may not match specialized rubbers in demanding environments.