What is NBR Material for Gaskets?

Introduction to NBR

Nitrile Butadiene Rubber (NBR), also known as Buna-N or acrylonitrile butadiene rubber, is a synthetic elastomer widely used for manufacturing gaskets and seals. Renowned for its exceptional resistance to oils, fuels, and hydrocarbons, NBR is a cost-effective and versatile material ideal for applications in automotive, industrial, and oil & gas sectors where moderate temperature and chemical conditions prevail.

Chemical Composition

NBR is a copolymer synthesized from two primary monomers:

• Acrylonitrile (ACN): Enhances resistance to oils, fuels, and chemicals.
• Butadiene: Provides flexibility, resilience, and low-temperature performance.

The ratio of ACN to butadiene can be adjusted (typically 18% to 50% ACN content) to tailor the material’s properties. Higher ACN content improves oil resistance but reduces flexibility at lower temperatures, while lower ACN prioritizes cold-weather performance.

Key Properties of NBR Gaskets

1. Oil and Fuel Resistance

NBR exhibits outstanding resistance to petroleum-based oils, greases, fuels, aliphatic hydrocarbons, and hydraulic fluids. This makes it indispensable in automotive fuel systems, hydraulic seals, and machinery exposed to oils.

2. Mechanical Durability

• Tensile Strength: High resistance to tearing and abrasion.
• Compression Set Resistance: Maintains sealing integrity under prolonged pressure.
• Hardness Range: Available in Shore A hardness grades from 40A to 80A, with 75A being standard for general-purpose gaskets.

3. Temperature Tolerance

• Standard Range: -30°C to +100°C.
• Extended Range: Specialized formulations operate between -40°C and +120°C.
  Note: Prolonged exposure above 100°C may cause hardening and reduced flexibility.

4. Chemical Compatibility

• Resistant To: Water, vegetable oils, mild acids, and hydraulic fluids.
• Vulnerable To: Ozone, UV radiation, polar solvents (e.g., acetone, ketones), and strong acids/bases.

Applications of NBR Gaskets

NBR’s balanced properties make it a preferred choice for:

• Automotive: Fuel line seals, engine gaskets, oil pan gaskets.
• Industrial Machinery: Hydraulic systems, pump seals, conveyor belt components.
• Oil & Gas: Pipeline seals, refinery equipment gaskets.
• Food Processing: FDA-approved grades for equipment exposed to oils and greases.

NBR Material Grades

Performance varies based on ACN content:

Limitations of NBR

• Temperature Sensitivity: Unsuitable for continuous use above 120°C or extreme cold below -40°C.
• Environmental Degradation: Susceptible to ozone, UV, and weathering, leading to surface cracking.
• Chemical Weaknesses: Poor performance in polar solvents and aggressive chemical environments.

Alternatives to NBR

For harsher conditions, consider:

• FKM (Viton®): Superior high-temperature (+200°C) and chemical resistance.
• EPDM: Excellent ozone/UV resistance and flexibility in extreme cold (-50°C).
• Silicone: Extreme temperature range (-60°C to +230°C) but lower oil resistance.

Conclusion

NBR is a cost-effective, durable elastomer optimized for gaskets in oil and fuel environments. Its versatility stems from adjustable ACN ratios, enabling tailored solutions for automotive, industrial, and food-grade applications. While limitations exist in extreme temperatures and chemical exposure, proper grade selection ensures reliable performance. For specialized needs, advanced materials like FKM or EPDM offer enhanced capabilities.

Summary
NBR (Nitrile Butadiene Rubber) is a petroleum-based synthetic elastomer prized for its oil resistance, mechanical strength, and adaptability. Its composition, adjustable via ACN content, allows engineers to balance flexibility and chemical resistance, making it a staple for gaskets in moderate operating conditions.