NBR
also Nitrile Rubber, Buna-N
NBR (Buna-N, Perbunan) is a copolymer of acrylonitrile and butadiene and the default oil-service elastomer, with about 16 MPa tensile strength, 400 % elongation, 1.25 g/cm³ density and continuous service near 100 °C.
Values for the Solid condition
NBR grades and fills
NBR is supplied in 14 conditions, soft to hard. Solid is the default FabDigit quotes; the values on this page are for it.
Compare all 14 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Closed-cell / expanded NBR foam | Pick for low-closure-force gasketing, oil-resistant insulation and vibration/acoustic padding where compressibility beats strength. | 2 | 150 | 20 Shore A | |
Shore A 40 | Soft, highly conformable compound for low-pressure gaskets and diaphragms on rough flanges. | 8 | 550 | 40 Shore A | |
Shore A 50 | Compliant sealing compound for static gaskets and low-load bellows. | 11 | 500 | 50 Shore A | |
Flame-retardant compound | Halogen or ATH loaded compound for mining hose, cable jackets and rail applications requiring flame/smoke ratings. | 11 | 280 | 25 Shore D | |
Shore A 60 | General O-ring hardness for moderate-pressure hydraulic and pneumatic seals. | 13 | 450 | 60 Shore A | |
Low-temperature grade | Pick for cold-climate seals down to about -45 °C, accepting more swell in fuels and oils. | 14 | 450 | 18 Shore D | |
NBR/PVC blend | Choose for outdoor hose covers, cable jackets and fuel-line outer layers needing ozone/UV resistance with oil resistance. | 14 | 350 | 22 Shore D | |
Conductive / antistatic | Specify for fuel-handling hose liners, rollers and pads where static must be bled off. | 14 | 280 | 28 Shore D | |
SolidDefault Dense vulcanized compound | Default choice for O-rings, gaskets, oil seals and hose liners where sealing force and oil resistance matter. | 16 | 400 | 22 Shore D | |
Shore A 70 | The default NBR seal hardness; best balance of extrusion resistance and sealability. | 16 | 400 | 22 Shore D | |
Shore A 80 | Harder compound for high-pressure seals, backup rings and shaft seals resisting extrusion. | 18 | 300 | 30 Shore D | |
High-ACN | Choose for aromatic fuels, biodiesel and aggressive oils where swell must be minimized; accepts a warmer low-temperature limit. | 18 | 350 | 25 Shore D | |
Shore A 90 | Use where extrusion/gap resistance or wear dominates (rod wipers, high-pressure back-ups); low sealing compliance. | 20 | 200 | 38 Shore D | |
Carboxylated nitrile | Use where abrasion and tear resistance govern (rod seals, rollers, gloves); slightly stiffer and less compression-set tolerant. | 24 | 350 | 25 Shore D |
Supply forms, finishes and certifications
Ways NBR is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FDA | FDA / food-contact and potable-water compound | Certification |
What is NBR?
NBR (Buna-N, Perbunan) is a copolymer of acrylonitrile and butadiene and the default oil-service elastomer, with about 16 MPa tensile strength, 400 % elongation, 1.25 g/cm³ density and continuous service near 100 °C. It is supplied as molded O-rings and seals, calendered sheet, sponge and extruded hose in 40–90 Shore A, plus HACN, low-temperature, XNBR, NBR-PVC, flame-retardant, FDA and ESD compounds. Resistance to ozone, weathering and polar fluids such as brake fluid and ketones is poor and heat capability stops around 100 °C; move to HNBR for heat and ozone or to FKM for aggressive chemicals. NBR has a density of 1.25 g/cm³ (0.0452 lb/in³), heavier than 64% of polymer grades. Its glass-transition temperature is -35°C (-31 °F). NBR has a tensile strength of 16 MPa (2.32 ksi), weaker than 72% of polymer grades. Elongation at break is 400% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
What is NBR used for?
- O-rings
- Fuel hoses
- Hydraulic seals
Advantages
- Ductile — tolerates forming and impact — 400%, better than 86% of polymer grades
- Forms and bends easily — 85/100, better than 81% of polymer grades
Limitations
- Needs corrosion protection — 60/100, worse than 89% of polymer grades
- Difficult to machine — 30/100, worse than 87% of polymer grades
- Low stiffness — 0.01 GPa (8.7×10⁻⁴ Msi), worse than 86% of polymer grades
- Difficult to weld — 10/100, worse than 82% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
NBR properties
Typical room-temperature values for NBR-Solid; bars are the position among polymer grades.
Physical4
NBR has a density of 1.25 g/cm³ (0.0452 lb/in³), heavier than 64% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical9
NBR has a tensile strength of 16 MPa (2.32 ksi), weaker than 72% of polymer grades. Elongation at break is 400% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal8
NBR is rated for continuous service to 100°C (212 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), better than 72% of polymer grades. Thermal expansion is 230 µm/m·K (127.8 µin/in·°F).
Electrical5
NBR is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10⁸ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 89% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of NBR takes about 110 MJ of energy and emits 4.5 kg of CO₂ — more than 64% of polymer grades. Typical recycled content is 5%.
Manufacturability5
NBR's machinability is poor (30/100, worse than 87% of polymer grades); weldability not recommended (10/100); formability excellent (85/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. NBR is highlighted; hover a dot for its name, or open the interactive family chart.
Working with NBR
Is NBR easy to machine?
Cured NBR can be lathe-turned, die-cut, waterjet or cryo-ground with very sharp tools and air cooling; expect tearing and dimensional rebound rather than chip formation.
Can NBR be welded?
Not weldable — join by cold-bonding cyanoacrylate/contact adhesive or by hot vulcanized splicing with uncured gum and a press.
Can NBR be formed, bent or molded?
Compression, transfer or injection molded and cured 3–10 min at 150–200 °C (sulfur or peroxide), with post-cure 2–4 h at 150 °C for low compression set; allow ~2 % shrinkage.
Manufacturability
The process limits FabDigit applies to NBR. Every NBR part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
Injection molding
| Mold shrinkage | — |
|---|---|
| Wall thickness | — – — |
| Recommended draft | — |
| Pre-drying | — |
NBR chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| acrylonitrilewt % of the copolymer; sets oil resistance vs low-temperature flexibility | 18 – 50 | 34 |
| carbon blackphr of compound, N550/N774 typical reinforcing filler | 20 – 60 | 40 |
| plasticizer (ester/DOP-type)phr, for softness and low-temperature performance | 0 – 20 | 8 |
| zinc oxidephr, cure activator | ≈ 5 | 5 |
| stearic acidphr, activator/process aid | ≈ 1 | 1 |
| sulfur + acceleratorsphr; peroxide cure used for lower compression set | 0.3 – 2.5 | 1.5 |
| antioxidant / antiozonantphr, TMQ/amine type | ≈ 2 | 2 |
| butadienebalance of the copolymer backbone | balance |
What surface finishes work on NBR?
Deflash by cryogenic tumbling; surfaces can be talc/PTFE dusted, chlorinated or plasma treated to cut friction, and no painting/plating is normally used.
Surface treatments FabDigit runs on polymer parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Injection Molding Coating
Metallization / Functional
Equivalent designations
Standards and trade names that resolve to NBR in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- Nitrile RubberBuna-NPerbunan
How much does NBR cost?
NBR is a standard-cost polymer ($$), cheaper than about 62% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
NBR — frequently asked
What is NBR used for?
NBR is typically used for O-rings, fuel hoses and hydraulic seals. In short: oil-resistant nitrile rubber.
What is the tensile strength of NBR?
NBR has a typical tensile strength of 16 MPa (2.32 ksi) — weaker than 72% of polymer grades. Strength varies by condition: see the 14 listed tempers.
Is NBR easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% of polymer grades). Cured NBR can be lathe-turned, die-cut, waterjet or cryo-ground with very sharp tools and air cooling; expect tearing and dimensional rebound rather than chip formation.
Can NBR be welded?
Not readily — weldability is rated not recommended (10/100). Not weldable — join by cold-bonding cyanoacrylate/contact adhesive or by hot vulcanized splicing with uncured gum and a press.
What surface finishes work on NBR?
Deflash by cryogenic tumbling; surfaces can be talc/PTFE dusted, chlorinated or plasma treated to cut friction, and no painting/plating is normally used.
Can NBR be formed, bent or molded?
Compression, transfer or injection molded and cured 3–10 min at 150–200 °C (sulfur or peroxide), with post-cure 2–4 h at 150 °C for low compression set; allow ~2 % shrinkage.
What is the maximum service temperature of NBR?
NBR is rated for continuous use to about 100°C (212 °F), and briefly to 130°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does NBR cost?
NBR is a standard-cost polymer ($$), cheaper than about 62% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in NBR?
Yes — NBR is available for injection molding; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- ASTM D412 / D2240 / D395 / D624 (tensile, hardness, compression set, tear) — ASTM (2021)
- ASM Engineered Materials Handbook Vol. 2 — Engineering Plastics & Elastomers — ASM International (1988)
- Rubber Technology / Science and Technology of Rubber (elastomer property tables) — Springer / Academic Press (2013)
- Nitrile (NBR) seal compound and O-ring material datasheets — Parker Hannifin / Trelleborg Sealing Solutions (2023)
- Perbunan / Krynac NBR grade datasheets — Arlanxeo (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.