NBR FR (Flame-retardant compound)
Flame-retardant grade
also Nitrile Rubber, Buna-N
Halogen or ATH loaded compound for mining hose, cable jackets and rail applications requiring flame/smoke ratings.
Values for the FR condition
Other NBR grades and fills
NBR is listed in 14 conditions; see the grade overview at NBR.
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 |
FRThis page 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 |
What is NBR FR?
NBR FR is NBR in the FR grade — halogen or ATH loaded compound for mining hose, cable jackets and rail applications requiring flame/smoke ratings. NBR FR has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 280% and the elastic modulus is 0.01 GPa (0.0012 Msi). NBR FR has a density of 1.45 g/cm³ (0.0524 lb/in³), heavier than 86% of polymer grades. Its glass-transition temperature is -35°C (-31 °F). Solid is the default condition FabDigit quotes; FR is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 280%, better than 80% of polymer grades
- Conducts heat well — 0.28 W/m·K (0.162 BTU/hr·ft·°F), better than 79% of polymer grades
Limitations
- Needs corrosion protection — 50/100, worse than 97% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- Heavy — 1.45 g/cm³ (0.0524 lb/in³), worse than 86% of polymer grades
- Low stiffness — 0.01 GPa (0.0012 Msi), worse than 82% of polymer grades
- Difficult to weld — 10/100, worse than 82% of polymer grades
NBR FR properties
Typical room-temperature values for NBR FR; 17 are specific to this condition. Other listed values are NBR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
NBR FR has a density of 1.45 g/cm³ (0.0524 lb/in³), heavier than 86% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical9
NBR FR has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 280% and the elastic modulus is 0.01 GPa (0.0012 Msi).
Thermal8
NBR FR is rated for continuous service to 95°C (203 °F). It conducts heat at 0.28 W/m·K (0.162 BTU/hr·ft·°F), better than 79% of polymer grades. Thermal expansion is 230 µm/m·K (127.8 µin/in·°F).
Electrical5
NBR FR is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 97% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of NBR FR 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 FR's machinability is poor (25/100, worse than 93% of polymer grades); weldability not recommended (10/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with NBR FR
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.
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.
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 | — |
NBR FR — frequently asked
What is NBR FR used for?
NBR FR is typically used for O-rings, fuel hoses and hydraulic seals. In short: oil-resistant nitrile rubber.
What is the tensile strength of NBR FR?
NBR FR has a typical tensile strength of 11 MPa (1.6 ksi) — weaker than 78% of polymer grades. Strength varies by condition: see the 14 listed tempers.
Is NBR FR easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% 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 FR 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 FR?
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 FR 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 FR?
NBR FR is rated for continuous use to about 95°C (203 °F), and briefly to 130°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in NBR FR?
Yes — NBR FR 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.