Greene, Tweed develops seals and o-rings using a variety of compounds to meet the needs of sealing applications across a broad range of industries and environments. Although the rigorous operating conditions of the primary industries we serve often require an FKM or FFKM sealing solution, there are several other sealing materials that are commonly used in a variety of applications. Although this page provides a high-level overview of these materials and their capabilities, Greene, Tweed’s engineering team can help determine the best fit for your needs - Contact us today for more information.
NBR, or nitrile rubber (also commonly referred to as buna-N rubber or perbunan), is a synthetic rubber copolymer of acrylonitrile (ACN) and butadiene. Higher ACN content yields better resistance to hydrocarbon oils, while lower ACN content provides better flexibility in low-temperature applications. NBR seals with a medium ACN content (approximately 30-45%) are the most commonly used because of their balanced attributes and applicability to most environments.
HNBR, or hydrogenated nitrile butadiene rubber, has a higher temperature rating than standard NBR, and also exhibits high tensile strength and great resistance to oil and chemicals.
FEPM is the ASTM designation for a range of alternating copolymers of tetrafluoroethylene (TFE) and propylene. FEPM offers great heat and excellent chemical resistance to a wide range of aggressive media.
Ethylene propylene (EPM or EP) rubber is a form of non-polar synthetic rubber that can only be cured with peroxide or radiation. EPDM consists of an additional monomer, diene, and can be cured using peroxide- or sulfur-based chemistries.
EPM and EPDM seals only differ slightly in performance. Both present outstanding resistance to hot water/steam and polar solvents, along with excellent ozone resistance.
Polyurethane (AU/EU/PU) rubber is most commonly formed by reacting a polyol with di- or poly-isocyanate. Polyurethane seals have high-wear, high-abrasion resistance, as well as great permeation resistance.
Chloroprene, or CR, rubber is a synthetic rubber based on the organic compound, 2-chlorobuta-1, 3-diene. Chloroprene seals provide high resistance to heat, ozone, and weathering.
Fluorosilicone (FVMQ) is the common shorthand for fluorovinylmethyl silicone. Fluorosilicone elastomers perform well in a wide range of temperatures, from as low as -73°C (-100°F), and as high as 177°C (350°F). Because of limited tear strength and abrasion resistance, however, they are generally only used in static applications.
Note: Characteristic metrics are provided as generally accepted industry ranges. Actual ranges may vary, depending on specific industry applications, such as additives, formulations, curatives used, etc.
|Temperature Range||-51°C - 149°C (-60°F - 300°F)||-51°C - 149°C (-60°F - 300°F)||-29°C - 177°C (-20°F - 350°F)||54°C - 150°C (-65°F - 302°F)||-60°C - 180°C (-76°F - 356°F)||-40°C - 82°C (-40°F - 180°F)|
|Tensile Strength||200-3,500 psi||1,500-3,500 psi||500-3,000 psi||1,015-3,045 psi||200-1,500 psi||500-6,000 psi|
|Minimum/ Maximum Hardness (Shore A)||20/90||30/95||20/95||40/90||40/80||40/90|
|Maximum Elongation (%)||600||340||600||600||480||580|
|Compression Set||Good to excellent||Good to excellent||Poor to good||Good||Fair to good||Fair to good|
|Chemical Resistance||Aliphatic hydrocarbons, vegetable & mineral oils, greases||Aliphatic hydrocarbons, vegetable & mineral oils, greases||Silicone oil & grease, refrigerants, ammonia, carbon dioxide||Hot water & steam, glycol-based brake fluids, cleaning agents, silicone oil & grease. Resistant to phosphate esterbased hydraulic fluids used in aerospace applications||Aromatic mineral oils, fuels, low molecular weight aromatic hydrocarbons||Pure aliphatic hydrocarbons, mineral & silicone oil & grease|
|Primary Industry Uses||Petrochemical Aerospace||Petrochemical Aerospace||Oil and Energy||Automotive Aerospace||Aerospace||Automotive|
|Limitations/ Not Recommended for||Not resistant to weathering, sunlight (UV), ozone||Direct sunlight (UV)|