Which is better, NBR or Viton?

When it comes to selecting the ideal sealing material for your application, two of the most common contenders are NBR (nitrile butadiene rubber) and Viton® (fluoroelastomer, FKM). Both have proven track records and offer unique strengths. Yet depending on operating conditions—temperature extremes, chemical exposure, mechanical demands, and cost constraints—one may outperform the other. In this article, we reorganize and refine the key performance criteria for NBR and Viton®, so you can quickly determine which material best suits your needs.

1. Temperature Performance

NBR (Nitrile Rubber)

• Standard temperature range: –25 °C to +100 °C.
• Extended formulations: approximately –40 °C to +120 °C with specialized compounding.
• Limitations: prolonged exposure above +120 °C accelerates aging and lead to hardening or cracking.

Viton® (FKM)

• Typical service range: –20 °C to +260 °C.
• Specialty grades (e.g., GLT, GFLT) can endure –40 °C low end or continuous peak temperatures above +250 °C.
• Advantages: maintains elastic properties at high temperatures, making it ideal for engine seals and chemical processing units.

Summary: If your application routinely exceeds +120 °C or faces repeated thermal cycling at high temperature, Viton® is the superior choice. For moderate temperatures and cost-sensitive projects below +100 °C, NBR remains highly effective.

2. Chemical and Oil Resistance

NBR

• Excellent resistance to petroleum-based oils, greases, hydraulic fluids, vegetable and animal fats.
• Vulnerabilities: ozone, UV, and solvents such as ketones (e.g., acetone) and esters (e.g., ethyl acetate) can degrade the polymer.
• Acrylonitrile content: higher levels increase oil resistance but reduce low-temperature flexibility.

Viton®

• Outstanding resistance to a wide variety of chemicals: aromatic and chlorinated hydrocarbons, strong acids, alkalis, and most non-flammable hydraulic fluids.
• Also resists ozone, oxidation, and UV exposure, ensuring long-term outdoor durability.
• Limitation: certain polar solvents (e.g., ketones and esters) can still attack some Viton® grades.

Summary: In corrosive chemical environments or where exposure to acids, solvents, or UV/ozone is expected, Viton® offers unmatched reliability. For general oil and fuel sealing under mild chemical exposure, NBR provides a cost-effective solution.

3. Mechanical Properties

NBR

• High tensile strength and tear resistance, giving excellent abrasion performance in dynamic sealing applications such as rotating shafts and reciprocating pumps.
• Good compression-set properties, though over time static seals may show slight deformation under constant load.

Viton®

• Superior compression-set resistance, meaning Viton® seals recover more completely after prolonged compression—critical for maintaining tight seals in high-pressure static applications.
• Lower gas permeability and higher electrical resistance compared to NBR.
• Slightly lower abrasion resistance but still adequate for most industrial uses.

Summary: Choose NBR where wear resistance and flexibility under motion are prioritized. Opt for Viton® when compression-set and long-term seal integrity under static or high-pressure conditions are critical.

4. Cost and Availability

NBR

• Among the most economical elastomers available.
• Widely produced, with mature manufacturing processes and broad supplier base.

Viton®

• Typically 5–10× the cost of NBR per unit volume, reflecting raw material and processing complexities.
• Specialized grades may incur additional lead times.

Summary: For budget-restricted projects or mass-market applications (automotive hydraulic seals, general industrial gaskets), NBR delivers the best value. When performance demands justify higher material investment—such as aerospace, chemical plants, or critical engine components—Viton®’s cost premium is offset by its extended service life and reliability.

5. Regulatory and Special Certifications

NBR

• Food-grade and drink-safe formulations exist; many NBR compounds meet FDA and NSF-61 standards for potable water.
• Used in food processing equipment gaskets, beverage dispensers, and medical device seals.

Viton®

• Fewer off-the-shelf food-grade or medical-grade options, though customized FFKM blends can achieve NFPA, FDA, or USP Class VI certifications.
• High-temperature sterilization and autoclave resistance make it suitable for some pharmaceutical applications.

Summary: If your seal must comply with stringent food or potable-water regulations, NBR often offers ready-made compliance. For specialized medical or pharmaceutical uses requiring high-temperature sterilization, consider certified Viton® variants.

Recommended Use Cases

Real-World Examples

• Automotive Engine Seals: Early rubber seals made from standard NBR often failed after prolonged operation at +105 °C. Upgrading to HNBR (hydrogenated nitrile) improved heat aging, but the best long-term performance was achieved by switching critical seals to Viton® FKM grades, despite higher cost.
• Food & Beverage Valve Seats: Manufacturers commonly select FDA-approved NBR because it resists oils and meets regulatory standards, while keeping equipment costs down.
• Chemical Plant Valves: In chlorinated or acidic service, Viton® FKM offers leak-free operation for years under harsh conditions, outlasting NBR by a significant margin.

Conclusion

Neither NBR nor Viton® is universally “better”—each excels in different regimes:

• Choose NBR when low cost, resistance to petroleum-based media, and dynamic wear resistance at moderate temperatures are your primary concerns.
• Choose Viton® when extreme heat, aggressive chemicals, UV/ozone exposure, or strict compression-set recovery are critical, and a higher material investment is justified.

By matching the material’s strengths to your specific temperature, chemical, mechanical, and regulatory requirements, you can ensure reliable, long-lasting sealing performance in your application.