This article is written by Axis (Xi'an) Technology Co., Ltd., a professional custom rubber sealing components manufacturer based in Xi'an, China. We specialize in custom O-rings, oil seals, and gaskets for industrial and automotive applications.
NBR: NBR (Nitrile Rubber) is the cost-effective choice for most general-purpose oil and hydraulic applications up to 120°C
FKM: FKM (Fluorocarbon Rubber / Viton) delivers superior performance in high-temperature and chemical environments up to 230°C, but costs more
Selection: The right choice depends entirely on your operating temperature, chemical exposure, and budget
Standards: Both materials work with international standards (ASTM/AS568/ISO 3601) and we can produce custom sizes for any application
NBR and FKM are two of the most common rubber materials used for industrial sealing, but many engineers struggle to choose between them. The short answer is simple: if your application stays under 120°C and doesn't handle aggressive chemicals, go with NBR to save money. If you need higher temperature or chemical resistance, spend the extra on FKM.
Let's break down the key differences to help you make the right call for your project.
NBR is the most widely used rubber material for general industrial sealing — and for good reason.
Temperature range: -30°C to 120°C continuous operation
Hardness options: 60-90 Shore A
Oil resistance: Excellent (5/5 rating)
Cost: Low — typically 1/3 to 1/2 the price of FKM
Standards compliance: Meets ASTM D2000 for general industrial use
General hydraulic systems
Fuel system components
Automotive oil seals
General-purpose O-rings for static applications
NBR is perfectly reliable for most common industrial environments. It's what we recommend for most customers when operating conditions don't push beyond its limits.
FKM is the premium choice when your application pushes the limits of what NBR can handle. The higher cost buys you dramatically better performance in extreme conditions.
Temperature range: -20°C to 230°C continuous operation
Hardness options: 70-90 Shore A
Chemical and heat resistance: Exceptional (5/5 rating)
Compression set: < 10% after 72h at 200°C — much better than NBR
Cost: High — but you get what you pay for
Standards compliance: Meets AMS/ASTM specifications for aerospace and chemical processing
Chemical processing equipment
Automotive engine compartments (high underhood temperatures)
Aerospace fuel systems
High-temperature industrial processes
If your application goes beyond 120°C, or you need resistance to aggressive chemicals, FKM is almost always the right long-term choice — the extra upfront cost avoids costly downtime from premature failure.
Property | NBR | FKM |
Max Continuous Temperature | 120°C | 230°C |
Min Temperature | -30°C | -20°C |
Hardness Range | 60-90 Shore A | 70-90 Shore A |
Oil Resistance | Excellent (5/5) | Excellent (5/5) |
Chemical Resistance | Good | Exceptional |
Compression Set | Moderate | < 10% at 200°C |
Cost | Low (1/3 to 1/2 of FKM) | High |
Typical Standards | ASTM D2000 | AMS/ASTM |
Ask yourself these three questions:
1. Temperature: What's your maximum continuous operating temperature? — If it's over 120°C, go FKM.
2. Chemicals: What chemicals will the seal contact? — Aggressive chemicals → FKM. General hydraulic oil → NBR works fine.
3. Budget: What's your budget? — If cost is critical and conditions fit NBR, it will serve you well.
Still unsure? Send us your application details, our engineering team will recommend the best material for free.
Q: Can FKM replace NBR in all applications?
A: Technically yes, but it's almost always overkill and a waste of money. NBR does the job just fine for most common applications at a much lower cost.
Q: Do you offer both materials in custom sizes?
A: Yes, we produce custom NBR and FKM seals to any drawing or sample, following AS568/ISO 3601 tolerance standards.
Q: What's the minimum order quantity for custom seals?
A: Our standard MOQ is 500 pieces for custom molded seals. We can accept smaller trial orders for product development (customer covers shipping cost).
Q: Are your materials certified?
A: Yes. All our materials meet relevant international certifications: ISO 9001:2015, REACH (EU), FDA for food-grade materials, and AMS/ASTM for FKM.
Choosing between NBR and FKM doesn't have to be complicated. Stick to this simple rule: go with NBR for general applications under 120°C to save money, upgrade to FKM when you need higher temperature or chemical resistance.
At Axis Rubber, we produce custom NBR and FKM seals to your exact specifications, with all the required certifications and consistent tolerance control. Whether you need 500 pieces or 50,000 pieces, we can deliver on time at competitive prices.
If you have an upcoming sealing project and need a quote, get in touch with our team today:
peter@axisrubber.com | www.axisrubber.com
