NBR O-Rings (Nitrile Rubber)
The industry-standard sealing material for hydraulic systems, fuel lines and petroleum-based fluid applications.
Overview
NBR (Acrylonitrile Butadiene Rubber), commonly known as Nitrile, is the most widely used O-ring material in industrial sealing. Its exceptional resistance to petroleum-based oils, hydraulic fluids and fuels makes it the default choice for hydraulic cylinders, pneumatic systems, fuel handling equipment and general industrial machinery.
With an operating temperature range of -40C to +120C and hardness options from 40 to 90 Shore A, NBR O-rings provide reliable sealing across a broad range of static and dynamic applications. The material offers excellent compression set resistance, good mechanical strength and outstanding abrasion resistance for reciprocating shaft seals.
NBR is also the most cost-effective elastomeric sealing material, making it the preferred option where oil resistance is required without the elevated cost of fluorocarbon compounds. Standard acrylonitrile content is 33-34%, with high-nitrile grades (39-40% ACN) available for improved fuel resistance.
Material Properties
| Temperature Range | -40C to +120C (-40F to +248F) |
| Hardness Range | 40-90 Shore A |
| Tensile Strength | 10-20 MPa |
| Elongation at Break | 200-350% |
| Compression Set (70h/100C) | <=25% |
| Specific Gravity | 1.00-1.25 |
| Color (standard) | Black |
| Standards | AS568, ISO 3601, DIN 3771 |
Typical Applications
Hydraulics
Cylinder seals, valve seals, piston rod seals in hydraulic systems using mineral oil-based fluids
Automotive
Engine oil seals, fuel system O-rings, transmission seals and brake system components
Pneumatics
Air cylinder seals, valve body seals and pneumatic fitting O-rings
Oil & Gas
Wellhead equipment seals, valve stem seals and pipeline flange gaskets in petroleum service
Industrial Machinery
Pump seals, gearbox seals, compressor seals and general mechanical assembly sealing
Chemical Compatibility Summary
Compatible With
- - Mineral oils
- - Hydraulic fluids
- - Gasoline and diesel fuels
- - Aliphatic hydrocarbons
- - Silicone oils and greases
Incompatible With
- - Ozone
- - Strong acids
- - Polar solvents (ketones, esters)
- - Aromatic hydrocarbons
- - Chlorinated hydrocarbons
Compare Nearby Materials
Further Reading
HNBR vs NBR O-Rings
When to stay with standard nitrile and when hydrogenated nitrile is worth the upgrade.
Read articleBest Material for Fuel Systems
Fuel compatibility, temperature, and when FKM displaces NBR in real systems.
Read articleKey Advantages
Excellent Oil and Fuel Resistance
Outstanding resistance to aliphatic hydrocarbons, petroleum oils, mineral hydraulic fluids and many fuels. The acrylonitrile content determines the level of oil resistance.
Wide Hardness Range
Available from 40 Shore A (soft, low-friction) to 90 Shore A (hard, high-pressure). Hardness selection depends on groove design and system pressure.
Cost Effective
NBR is the most economical O-ring material. For petroleum-fluid applications, it delivers strong performance at a fraction of the cost of fluorocarbon compounds.
Good Mechanical Properties
High tensile strength and abrasion resistance make NBR suitable for dynamic sealing applications including rotary and reciprocating shaft seals.
Frequently Asked Questions - NBR
What is the maximum temperature for NBR O-rings?
Standard NBR O-rings operate reliably up to +120C in continuous service. Short-term excursions to +135C are possible. For higher temperatures, FKM or EPDM should be considered depending on the fluid media.
Can NBR O-rings be used with water?
NBR has acceptable resistance to fresh water and some aqueous solutions at moderate temperatures. However, for hot water, steam or water-glycol hydraulic fluids above 80C, EPDM is the preferred material.
What fluids are NBR O-rings not compatible with?
NBR is not suitable for ozone, strong oxidizing agents, ketones (MEK, acetone), esters, chlorinated solvents or aromatic hydrocarbons. For aggressive chemical environments, FKM or PTFE should be used.
What hardness NBR O-ring should I use for hydraulic sealing?
For hydraulic cylinder seals with system pressures up to 40 MPa, 70 Shore A NBR is the standard recommendation. For higher pressures or to prevent extrusion, 80-90 Shore A with anti-extrusion rings is advisable.
Do you supply FDA-grade NBR O-rings?
Standard NBR is not FDA compliant for direct food contact. For food and beverage applications, we recommend FDA-grade EPDM or VMQ (Silicone) instead. Contact us for food-grade material options.
What AS568 sizes do you have in NBR?
We carry the full AS568 range (AS568-001 through AS568-395) in standard 70 Shore A black NBR from stock. Other hardnesses and compound specifications are available on a short lead time.