NBR

Nitrile Rubber, also known as NBR or Buna-N, is a synthetic copolymer
of acrylonitrile (ACN) and butadiene. It is widely used because of its
resistance to petroleum oils, fuels, and many chemicals.

NBR is designated under ASTM D1418. Under ASTM D2000, NBR compounds
commonly fall under codes such as BF, BG, BK, or CH. These codes describe
required performance, including heat and oil resistance, rather than
identifying the polymer chemistry itself.

NBR is commonly used in:

• Automotive, marine, and aeronautical fuel systems
• O-rings, gaskets, oil seals, and shaft seals
• Hydraulic hoses and pneumatic seals
• Disposable non-latex gloves for medical and industrial use
• Belts, hoses, and adhesives
• Footwear and oil-resistant floor mats
• Oil and gas seals compliant with NORSOK M-710

Temperature ranges are general guidance for the NBR polymer family.
The usable range of a specific component depends on its grade, compound,
cure system, exposure time, and actual service conditions.

• Standard NBR: typically -40°C to +100°C (-40°F to +212°F)
• Special low-temperature compounds: down to approximately -55°C (-67°F)
• Special high-temperature compounds: limited excursions toward +125°C to +135°C (+257°F to +275°F)
• For continuous service above 100°C, HNBR or AEM may be more suitable

Always confirm the temperature range against the specific compound
datasheet and validate it under real service conditions.

NBR compounds are generally available in hardness values ranging from
40 to 90 Shore A. A hardness of 70 Shore A is the most common choice
for general sealing applications.

NBR is designated as NBR under ASTM D1418. Under ASTM D2000, it is
specified through type and class codes, commonly BF, BG, BK, or CH
for nitrile compounds.

The type letter reflects the required heat resistance, while the class
letter reflects oil resistance. Additional suffixes may define properties
such as compression set and low-temperature performance.

ASTM D2000 describes the performance a compound must achieve.
It does not classify the material solely by polymer chemistry.

Nitrile Rubber resists petroleum-based oils, aliphatic hydrocarbons,
and many lubricants. Its oil resistance is influenced by its
acrylonitrile content. Higher ACN generally improves oil resistance,
but reduces flexibility at low temperatures.

Resistance to gasoline and diesel depends on the compound’s ACN content,
the aromatic or alcohol content of the fuel, and the service temperature.
Modern oxygenated fuels can be more aggressive than traditional
reference fuels.

Compatibility should therefore be confirmed using the actual fuel
specification and operating temperature. FKM may be more suitable
for particularly aggressive fuel environments.

Yes. The acrylonitrile content can be adjusted to change the balance
between oil resistance and low-temperature flexibility:

• Low ACN, 15–25%: better low-temperature flexibility and moderate oil resistance
• Medium ACN, 28–35%: balanced properties for general applications
• High ACN, 39–44%: high oil resistance with reduced low-temperature flexibility
• Extra-high ACN, 49–51%: maximum oil resistance but greater brittleness at low temperatures

NBR can also be sulfur-cured or peroxide-cured. The chosen cure system
influences heat resistance, compression set, and long-term performance.

Nitrile Rubber performs well with mineral oils, vegetable oils,
silicone oils, greases, many petroleum fuels, ethylene glycol,
dilute acids, and water below 100°C.

It also offers good abrasion resistance and useful chemical resistance
at a competitive price. This makes it a common choice for industrial,
automotive, hydraulic, and pneumatic sealing applications.

Compression set depends on the specific compound and cure system.
Peroxide-cured and specially formulated grades generally perform better
than standard sulfur-cured compounds when retained sealing force is critical.

NBR generally has limited resistance to:

• Ozone, sunlight, and prolonged weather exposure
• Strong acids and oxidizing agents
• Ketones, esters, ethers, and aromatic hydrocarbons
• Glycol-based automotive brake fluids such as DOT 3 and DOT 4
• Chlorinated hydrocarbons and polar solvents

EPDM or HNBR may be better options for outdoor or ozone-exposed
applications.

The standard color for NBR is black because most compounds are
reinforced with carbon black. Red, blue, white, and green compounds
are also available using non-black fillers.

Colored compounds may offer lower mechanical performance than
comparable black NBR compounds. The correct formulation should
therefore be selected according to the application’s requirements.

HNBR is a hydrogenated form of NBR. Most of the double bonds in the
butadiene portion are saturated with hydrogen, improving several
performance characteristics.

• Heat resistance: HNBR compounds typically serve up to approximately 150°C, compared with around 100°C for standard NBR
• Ozone resistance: HNBR offers good resistance, while standard NBR performs poorly
• Aging resistance: HNBR retains its properties for longer periods

HNBR is usually more expensive than standard NBR. It is commonly used
when the performance improvement justifies the added cost, including
oil and gas seals, automotive timing belts, and air-conditioning systems.

Yes, when the correct formulation is used. High-grade NBR compounds
qualified to NORSOK M-710 are used for O-rings and seals exposed to
hydrocarbons and hydrogen sulfide in upstream oil and gas applications.

HNBR or FKM may be preferred for higher temperatures or demanding
sour-service environments. Material selection should be based on the
actual pressure, temperature, fluid exposure, and operating conditions.