NBR Rubber: Complete Guide to Nitrile Butadiene Rubber Properties, Applications, and Manufacturing (2026)
NBR (Nitrile Butadiene Rubber), also known as Nitrile rubber or Buna-N®, has earned its reputation as the workhorse elastomer for oil-resistant sealing applications. With excellent resistance to petroleum-based oils and fuels, good mechanical properties, and competitive pricing, NBR remains the material of choice for automotive seals, hydraulic hoses, industrial gaskets, and countless other applications where petroleum fluid resistance is critical.
This comprehensive guide covers everything you need to know about NBR rubber: from fundamental properties and acrylonitrile content effects to manufacturing processes, compliance standards, and how to select a reliable supplier in China.
Table of Contents
- What is NBR Rubber?
- Key Properties of NBR
- Acrylonitrile Content Effects
- NBR Material Grades
- Chemical Resistance Guide
- Common Applications
- NBR vs. Other Elastomers
- Temperature and Pressure Ratings
- Manufacturing Processes
- Industry Compliance Standards
- How to Select a Supplier
- Pricing and MOQ
- FAQ
- Conclusion
What is NBR Rubber?
NBR (Nitrile Butadiene Rubber) is a synthetic elastomer produced through emulsion polymerization of acrylonitrile and butadiene. The resulting copolymer combines the oil resistance of acrylonitrile with the flexibility of butadiene, creating an elastomer with excellent resistance to petroleum-based fluids.
Chemical Structure
The NBR polymer chain contains:
- Acrylonitrile (ACN) units: Provide oil and fuel resistance
- Butadiene units: Provide flexibility and low-temperature properties
- Typical ACN content: 15% to 50% by weight
Trade Names and Synonyms
| Term | Description |
| NBR | Nitrile Butadiene Rubber (ASTM/DIN standard) |
| Nitrile | Common commercial term |
| Buna-N® | Historical brand name (formerly from Goodyear/Bayer) |
| Perbunan® | Historical brand (Bayer/BNK) |
| Nipol® | Brand from Zeon Chemicals |
ASTM D2000 Classification
NBR compounds are classified under ASTM D2000 as:
- BC (Low ACN content, low-temperature flexibility)
- BK (High ACN content, oil-resistant)
- BF (Medium ACN content, general purpose)
Key Properties of NBR
NBR offers an attractive balance of oil resistance, mechanical properties, and cost:
| Property | Value | Significance |
| Temperature Range | -40°F to +250°F (-40°C to +121°C) | Good operating range |
| Hardness | 40-95 Shore A | Versatile durometer options |
| Tensile Strength | 2,000-4,000 psi | Good mechanical strength |
| Elongation | 300-600% | Highly flexible |
| Compression Set | 15-40% (at 70h @ 100°C) | Good seal memory |
| Oil Resistance | Good to Excellent | Varies with ACN content |
| Abrasion Resistance | Excellent | Ideal for dynamic seals |
| Cost | $ | Most economical oil-resistant elastomer |
Advantages of NBR
- ✅ Excellent oil and fuel resistance (petroleum-based)
- ✅ Good mechanical properties (tensile, abrasion)
- ✅ Competitive pricing (most cost-effective oil-resistant elastomer)
- ✅ Wide hardness range available
- ✅ Good dynamic seal performance
- ✅ Easy processing and molding
- ✅ Widely available from multiple suppliers
Limitations of NBR
- ❌ Poor ozone and weather resistance (requires additives or protection)
- ❌ Limited high-temperature capability (max ~250°F / 121°C)
- ❌ Poor resistance to polar solvents (ketones, esters)
- ❌ Not suitable for food or medical contact (standard grades)
- ❌ Can become brittle at very low temperatures (below -40°F)
Acrylonitrile Content Effects
The acrylonitrile (ACN) content in NBR is the primary factor determining its oil resistance and low-temperature flexibility:
Low ACN Content (15-22%)
- Oil Resistance: Fair (limited to light oils)
- Low-Temp Flexibility: Excellent (-50°F / -46°C)
- Typical Applications: Refrigerant seals, cold-climate gaskets
- Trade-off: Sacrifices oil resistance for flexibility
Medium ACN Content (28-35%)
- Oil Resistance: Good (general-purpose)
- Low-Temp Flexibility: Good (-35°F / -37°C)
- Typical Applications: Automotive seals, hydraulic gaskets
- Balance: Best all-around performance
High ACN Content (36-45%)
- Oil Resistance: Excellent (heavy fuels, ATF)
- Low-Temp Flexibility: Fair (-15°F / -26°C)
- Typical Applications: Fuel system seals, severe-service gaskets
- Trade-off: Better oil resistance, reduced cold flexibility
Very High ACN Content (45-50%)
- Oil Resistance: Superior (very heavy oils, aromatic fuels)
- Low-Temp Flexibility: Limited (+5°F / -15°C)
- Typical Applications: Specialty seals for severe environments
- Cost: Premium pricing
ACN Content Comparison Table
| ACN % | Oil Resistance | Low-Temp Flex | Cost | Applications |
| 15-22% | Fair | Excellent | $ | Refrigerants, cold climate |
| 28-35% | Good | Good | $$ | General purpose |
| 36-45% | Excellent | Fair | $$$ | Fuels, ATF, heavy oils |
| 45-50% | Superior | Limited | $$$$ | Severe service |
⚠️ Important: Higher ACN content provides better oil resistance but reduces low-temperature flexibility. Select based on your actual operating environment.
NBR Material Grades
General Purpose NBR
- ACN content: 28-35%
- Temperature: -35°F to +225°F (-37°C to +107°C)
- Applications: General industrial sealing
- Cost: $
High-Temperature NBR
- Special compounds: Heat stabilizers added
- Temperature: Up to +300°F (+149°C) intermittent
- Applications: Turbocharger seals, high-temp oil
- Cost: $$
Low-Temperature NBR
- Special compounds: Cold-flex additives
- Temperature: Down to -65°F (-54°C)
- Applications: Arctic equipment, refrigeration
- Cost: $$
High-ACN NBR
- ACN content: 40-50%
- Temperature: -15°F to +250°F (-26°C to +121°C)
- Applications: Fuel system seals, severe service
- Cost: $$$
Hydrogenated NBR (HNBR)
- Process: Hydrogenation of NBR polymer
- Temperature: -40°F to +350°F (-40°C to +177°C)
- Oil Resistance: Excellent (improved vs. NBR)
- Applications: Aerospace, high-performance automotive
- Cost: $$$$$
Carboxylated NBR (XNBR)
- Modification: Carboxylic acid groups added
- Properties: Enhanced tensile, tear, and abrasion resistance
- Applications: High-stress seals, hydraulic components
- Cost: $$$
Chemical Resistance Guide
Excellent Resistance ✓
- Petroleum oils (hydraulic oil, motor oil)
- Petroleum fuels (gasoline, diesel, kerosene)
- ATF (Automatic Transmission Fluid)
- Crude oil and refined petroleum products
- Vegetable oils and animal fats (some grades)
- Water (up to 180°F / 82°C)
- Dilute acids (some concentrations)
Limited/Poor Resistance ✗
- Aromatic solvents (benzene, toluene)
- Chlorinated solvents (perchloroethylene, trichloroethylene)
- Ketones (MEK, acetone)
- Esters (acetate, phthalate plasticizers)
- Silicone oils and greases
- Brake fluids (glycol-based)
- Strong acids and alkalis
- Ozone and weathering (standard grades)
⚠️ Important: NBR is NOT suitable for:
- Phosphate ester hydraulic fluids (Skydrol, HFD-R)
- Ketone and ester solvents
- Strong oxidizing agents
- Food or medical applications (standard grades)
Oil Resistance by Application
| Application | Recommended ACN % |
| Refrigerant seals (R-134a) | 15-25% |
| Automotive engine oil | 28-35% |
| Automatic transmission | 36-45% |
| Diesel fuel | 28-35% |
| Aviation fuel (Jet A) | 36-45% |
| Crude oil immersion | 40-50% |
| ATF (Type A) | 36-45% |
Common Applications
Automotive Industry
- Engine oil pan gaskets
- Valve cover gaskets
- Transmission seals
- Fuel pump gaskets
- Brake cup diaphragms
- Hydraulic clutch seals
- Power steering seals
Industrial Equipment
- Hydraulic system seals
- Pump gaskets and seals
- Compressor seals
- Industrial hose covers
- Conveyor belt scrapers
- Lubricant reservoir seals
Oil and Gas
- Downhole packer elements
- Wellhead seals
- Pipeline gaskets
- BOP (Blowout Preventer) seals
- Subsea connection seals
- Drilling mud seals
Aerospace
- Fuel system seals
- Hydraulic system seals
- Landing gear components
- Aircraft fuel tank seals
Food Processing (Special Grades)
- Food-grade NBR for non-fatty food contact
- FDA 21 CFR 177.2600 compliant (for dry foods)
- Note: For fatty foods or medical, use silicone or FKM
Household Appliances
- Refrigerator door gaskets
- Dishwasher spray arm seals
- Washing machine door boots
- Vacuum cleaner seals
NBR vs. Other Elastomers
| Property | NBR | FKM | EPDM | Silicone |
| Temp Range | -40 to +250°F | -20 to +400°F | -65 to +300°F | -85 to +450°F |
| Oil Resistance | Excellent | Excellent | Poor | Poor |
| Weather/Ozone | Poor | Excellent | Excellent | Excellent |
| Steam Resistance | Poor | Poor | Good | Good |
| Cost | $ | $$$$ | $$ | $$$ |
| FDA Compliance | No (special) | Limited | Limited | Yes |
Best choice for:
- Oil-resistant seals at competitive price → NBR
- High-temp + oil resistance → FKM
- Outdoor/weather resistance + water → EPDM
- Extreme temps + food/medical → Silicone
- Best value oil resistance → NBR
Temperature and Pressure Ratings
Maximum Service Temperature by Grade
| Grade | Continuous | Intermittent |
| Standard NBR | 225°F (107°C) | 250°F (121°C) |
| High-Temp NBR | 300°F (149°C) | 350°F (177°C) |
| HNBR | 350°F (177°C) | 400°F (204°C) |
| Low-Temp NBR | 200°F (93°C) | 250°F (121°C) |
Minimum Service Temperature
| Grade | Minimum |
| Standard NBR | -35°F (-37°C) |
| Low-Temp NBR | -65°F (-54°C) |
| HNBR | -40°F (-40°C) |
Pressure Ratings
| Seal Type | Max Pressure |
| O-ring (static) | 3,000 psi (207 bar) |
| O-ring (dynamic) | 1,500 psi (103 bar) |
| Gasket (flat) | 1,500 psi (103 bar) |
| Lip seal | 500 psi (35 bar) |
Manufacturing Processes
Compression Molding
- Best for: Low-medium volume, large parts
- Tolerance: ±0.005" to ±0.020"
- Tooling Cost: $500-$5,000
- Per-part Cost: Moderate
- Typical MOQ: 100-500 pieces
Injection Molding
- Best for: High volume, complex parts
- Tolerance: ±0.003" to ±0.010"
- Tooling Cost: $5,000-$50,000
- Per-part Cost: Low at volume
- Typical MOQ: 2,000-10,000 pieces
Transfer Molding
- Best for: Insert molding, medium volume
- Tolerance: ±0.005" to ±0.015"
- Tooling Cost: $2,000-$15,000
- Per-part Cost: Moderate
- Typical MOQ: 500-2,000 pieces
Extrusion
- Best for: Continuous profiles, cord, tubing
- Tolerance: ±0.010" to ±0.030"
- Tooling Cost: $1,000-$10,000
- Per-part Cost: Low
- Typical MOQ: 500-2,000 meters
Calendering
- Best for: Sheet, film, die-cut parts
- Thickness: 0.020" to 0.500"
- Width: Up to 60"
- Typical MOQ: 100-500 kg
Industry Compliance Standards
Automotive
- SAE J200: Rubber material classification system
- ASTM D2000: Standard classification system for rubber products
- ISO 1629: Rubber and cords – vocabulary
- IATF 16949: Automotive quality management (suppliers)
Oil and Gas
- API 6D: Pipeline valves – for NBR valve seats
- NACE MR0175: Sour service (for oil/gas NBR compounds)
- API 618: Reciprocating compressors (NBR seals)
Industrial
- ISO 9001:2015: Quality management
- REACH/RoHS: EU chemical regulations
Food (Special Grades Only)
- FDA 21 CFR 177.2600: Rubber articles for repeated food contact
- Note: Standard NBR is NOT FDA compliant for food contact
How to Select a Supplier
When sourcing NBR parts from China:
1. Compound Verification
- Request compound data sheets
- Verify ACN content and physical properties
- Request batch test certificates
2. ACN Content Selection
- Match ACN content to your oil exposure:
- Light oils (refrigerants): 15-22% ACN
- Motor oil, diesel: 28-35% ACN
- Heavy fuels, ATF: 36-45% ACN
3. Manufacturing Capabilities
- Compression molding for custom parts
- Injection molding for high volume
- Extrusion for profiles and cord
- Finishing and bonding services
4. Quality Management
- ISO 9001:2015 certification
- PPAP (Production Part Approval Process) for automotive
- First Article Inspection (FAI) reports
5. Testing and Validation
- Physical property testing (hardness, tensile, elongation)
- Compression set testing
- Volume swell testing (ASTM D471) in actual fluid
- Low-temperature embrittlement testing
Red Flags ⚠️
- Unable to provide compound data sheets
- No batch testing or COC (Certificate of Conformance)
- Very low prices (may indicate recycled or off-spec materials)
- No sample policy
- Limited communication or response delays
Pricing and MOQ
Price Factors
- ACN content (higher ACN = higher cost)
- Compound additives (specialty compounds cost more)
- Order volume (economies of scale apply)
- Part complexity and tolerance
- Tooling requirements
Typical Pricing (USD per piece)
| Part Type | 1,000 pcs | 10,000 pcs | 50,000 pcs |
| O-ring (10mm ID) | $0.05-0.15 | $0.02-0.08 | $0.01-0.05 |
| Custom Gasket | $0.30-1.00 | $0.15-0.50 | $0.08-0.30 |
| Hydraulic Seal | $0.50-2.00 | $0.25-1.00 | $0.15-0.60 |
| Complex Molded Part | $1.00-5.00 | $0.50-2.50 | $0.30-1.50 |
Note: High-ACN and specialty NBR compounds command premium pricing.
MOQ Expectations
- Standard O-rings: 100-1,000 pieces
- Custom molded parts: 200-1,000 pieces
- Extruded profiles: 500-2,000 meters
- Specialty compounds: 500-2,000 pieces
FAQ
Q: What's the difference between NBR and HNBR?
A: Key differences:
| Property | NBR | HNBR |
| Hydrogenation | None | 90-100% saturated |
| Temperature | -40 to +250°F | -40 to +350°F |
| Oil Resistance | Good | Excellent |
| Ozone Resistance | Poor | Good |
| Cost | $ | $$$$ |
Q: Can NBR be used in transmission fluid (ATF)?
A: Yes, but select carefully:
- ATF applications: Use 36-45% ACN NBR
- ATF contains additives that can swell standard NBR
- Always validate with fluid immersion testing
Q: How does NBR perform in outdoor applications?
A: Standard NBR has poor ozone and UV resistance. For outdoor use:
- Add carbon black for UV protection
- Use EPDM for better weather resistance
- Consider specialty NBR with antioxidant packages
Q: What's the shelf life of NBR parts?
A: NBR has moderate aging resistance:
- Typical shelf life: 5-10 years (depending on storage)
- Storage conditions: Cool, dark, dry environment
- Avoid: Ozone sources, direct sunlight, chemical exposure
Q: Is NBR FDA compliant?
A: Standard NBR is NOT FDA compliant. For food contact:
- Dry foods only: Some FDA 21 CFR 177.2600 grades available
- Fatty foods: Use silicone or special FKM
- Medical applications: Use silicone, FKM, or medical-grade elastomers
Q: Can NBR be bonded to metal?
A: Yes, with proper surface treatment:
- Mechanical bonding: Overmolding to primed metal inserts
- Chemical bonding: Surface treatment + primer (like Thixon)
- Adhesive bonding: Cyanoacrylate or epoxy adhesives
Conclusion
NBR rubber remains the most cost-effective choice for oil-resistant sealing applications. Its excellent petroleum fluid resistance, good mechanical properties, and competitive pricing make it the workhorse elastomer for automotive, industrial, and oil & gas sealing applications.
When sourcing NBR parts from China, partner with suppliers who:
- Provide compound data sheets with ACN content verified
- Offer material selection guidance for your specific fluid exposure
- Have quality certifications (ISO 9001, IATF 16949 for automotive)
- Conduct batch testing for critical applications
Need custom NBR parts from a reliable China manufacturer?
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This guide is for informational purposes. Consult with our engineering team for application-specific material recommendations.
