NBR · grade
NBR Sponge
Properties of the Sponge condition, compared with the other NBR grades.
Pick for low-closure-force gasketing, oil-resistant insulation and vibration/acoustic padding where compressibility beats strength.
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 84% of polymer grades. Elongation at break is 150% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi). NBR Sponge has a density of 0.5 g/cm³ (0.0181 lb/in³), lighter than 83% 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
- Lightweight — 0.5 g/cm³ (0.0181 lb/in³), better than 83% of polymer grades
Limitations
- Low stiffness — 0.01 GPa (7.25×10⁻⁴ Msi), worse than 89% of polymer grades
- Difficult to machine — 30/100, worse than 88% of polymer grades
- Poor heat conductor — 0.06 W/m·K (0.0347 BTU/hr·ft·°F), worse than 84% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
NBR Sponge properties
Typical room-temperature values for NBR Sponge — 9 properties are specific to this condition; the rest are grade-level values shared by every NBR grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical4
NBR Sponge has a density of 0.5 g/cm³ (0.0181 lb/in³), lighter than 83% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical7
NBR Sponge has a tensile strength of 2 MPa (0.218 ksi), weaker than 84% of polymer grades. Elongation at break is 150% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ 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 & Environmental2
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%.
Manufacturability3
NBR Sponge's machinability is poor (30/100, worse than 88% of polymer grades).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other NBR grades and fills
NBR is also supplied in 14 other conditions. The full side-by-side table is on the NBR overview.
- SolidDefaultDefault choice for O-rings, gaskets, oil seals and hose liners where sealing force and oil resistance matter.16 MPa tensile
- SpongePick for low-closure-force gasketing, oil-resistant insulation and vibration/acoustic padding where compressibility beats strength.2 MPa tensile
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 84% of polymer grades. Strength varies by condition: see the 15 listed tempers.
Is NBR Sponge easy to machine?
Not especially — machinability is rated poor (30/100, worse than 88% 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 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 sheet metal and injection molding with instant online pricing. 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.