Common Sealing Materials

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.

Materials Overview

NBR/HNBR

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

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.

EPM/EPDM

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.

AU

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.

CR

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.

FVMQ

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.

Materials Comparison

MaterialNBRHNBRCREPM/EPDMFVMQAU/EEU
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 Strength200-3,500 psi1,500-3,500 psi500-3,000 psi1,015-3,045 psi200-1,500 psi500-6,000 psi
Minimum/ Maximum Hardness (Shore A)20/9030/9520/9540/9040/8040/90
Maximum Elongation (%)600340600600480580
Compression SetGood to excellentGood to excellentPoor to goodGoodFair to goodFair to good
Chemical ResistanceAliphatic hydrocarbons, vegetable & mineral oils, greasesAliphatic hydrocarbons, vegetable & mineral oils, greasesSilicone oil & grease, refrigerants, ammonia, carbon dioxideHot water & steam, glycol-based brake fluids, cleaning agents, silicone oil & grease. Resistant to phosphate esterbased hydraulic fluids used in aerospace applicationsAromatic mineral oils, fuels, low molecular weight aromatic hydrocarbonsPure aliphatic hydrocarbons, mineral & silicone oil & grease
Primary Industry UsesPetrochemical AerospacePetrochemical AerospaceOil and EnergyAutomotive AerospaceAerospaceAutomotive
Features
  • Good mechanical properties
  • High wear resistance
  • Wide range of temperature resistance
  • High oil & fuel resistance
  • Excellent abrasion & tear properties
  • Resists ozone, sun-light, & other atmospheric environments
  • High wear resistance
  • Wide range of temperature resistance
  • Good oil, ozone, weather, aging, refrigeration, & chemical resistance
  • Good mechanical properties over a wide temperature range
  • Excellent resistance to phosphate ester fluids (Skydrol), brake fluids (glycol base), steam, weather, & ozone
  • Very good heat & oxidation resistance
  • High gas permeability
  • Poor tear & abrasion resistance
  • Very good chemical, fuel, & oil resistance
  • Generally resistant to ozones, hydrocarbons, moderate chemicals, oils, greases
  • Returns to original shape once load is removed w/little compression set
  • High temperature resistance
Limitations/ Not Recommended forNot resistant to weathering, sunlight (UV), ozoneDirect sunlight (UV)
  • Aromatic / chlorinated hydrocarbons
  • Acetones
  • Non-polar fluids
  • Hydrocarbon oils
  • Lubricants
  • Greases
  • Not recommended for dynamic sealing, brake fluids, hydrazine, ketones
  • Limited physical strength
  • Poor abrasion resistance
  • Acids
  • Ketones
  • Esters
  • Ethers
  • Alcohols
  • Glycols Hot water/steam
  • Alkalis
  • Amines


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