NBR Sponge
Grade
also Nitrile Rubber, Buna-N
Sponge = closed-cell / expanded NBR foam
Pick for low-closure-force gasketing, oil-resistant insulation and vibration/acoustic padding where compressibility beats strength.
Values for the Sponge 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 |
|---|---|---|---|---|---|
SpongeThis page 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 |
What is NBR Sponge?
NBR Sponge is NBR in the Sponge grade — pick for low-closure-force gasketing, oil-resistant insulation and vibration/acoustic padding where compressibility beats strength. NBR Sponge has a tensile strength of 2 MPa (0.218 ksi), weaker than 85% of polymer grades. Elongation at break is 150% and the elastic modulus is 0 GPa (1.45×10⁻⁴ Msi). NBR Sponge has a density of 0.5 g/cm³ (0.0181 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -35°C (-31 °F). Solid is the default condition FabDigit quotes; Sponge is available on request or by drawing note.
Advantages
- Forms and bends easily — 90/100, better than 91% of polymer grades
- Lightweight — 0.5 g/cm³ (0.0181 lb/in³), better than 84% of polymer grades
Limitations
- Low stiffness — 0 GPa (1.45×10⁻⁴ Msi), worse than 98% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- High mold shrinkage — 2.5%, worse than 93% of polymer grades
- Needs corrosion protection — 58/100, worse than 92% of polymer grades
- Poor heat conductor — 0.06 W/m·K (0.0347 BTU/hr·ft·°F), worse than 84% of polymer grades
NBR Sponge properties
Typical room-temperature values for NBR Sponge; 19 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 Sponge has a density of 0.5 g/cm³ (0.0181 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical9
NBR Sponge has a tensile strength of 2 MPa (0.218 ksi), weaker than 85% of polymer grades. Elongation at break is 150% and the elastic modulus is 0 GPa (1.45×10⁻⁴ Msi).
Thermal8
NBR Sponge is rated for continuous service to 90°C (194 °F). It conducts heat at 0.06 W/m·K (0.0347 BTU/hr·ft·°F), worse than 84% of polymer grades. Thermal expansion is 230 µm/m·K (127.8 µin/in·°F).
Electrical5
NBR Sponge 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 (58/100), worse than 92% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of NBR Sponge 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 Sponge's machinability is poor (25/100, worse than 93% of polymer grades); weldability not recommended (10/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with NBR Sponge
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 Sponge — frequently asked
What is NBR Sponge used for?
NBR Sponge is typically used for O-rings, fuel hoses and hydraulic seals. In short: oil-resistant nitrile rubber.
What is the tensile strength of NBR Sponge?
NBR Sponge has a typical tensile strength of 2 MPa (0.218 ksi) — weaker than 85% of polymer grades. Strength varies by condition: see the 14 listed tempers.
Is NBR Sponge 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 Sponge 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 Sponge?
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 Sponge 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 Sponge?
NBR Sponge is rated for continuous use to about 90°C (194 °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 Sponge?
Yes — NBR Sponge 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.