When selecting a sealing solution for your machinery, system, or product line, choosing the right material is just as important as selecting the right shape or size. Whether you’re dealing with an Silicone, NBR seal, an EPDM seal, or a high-performance FKM O ring, the material directly influences durability, chemical resistance, temperature tolerance, and overall system reliability. In this guide, we dive deep into the science and practicality of sealing materials—from everyday use to extreme environments. Know more..
The Role of Material in Seal Function
Seals are the unsung heroes of mechanical engineering. They retain pressure, prevent contamination, and keep systems running smoothly. But their effectiveness depends heavily on their material properties:
- Elasticity and compression set
- Resistance to oils, fuels, and chemicals
- Temperature stability
- Weathering and ozone resistance
A poor material match can lead to swelling, hardening, cracking, or total failure.
NBR (Nitrile Butadiene Rubber): The Everyday Performer
The NBR seal is the go-to solution for basic oil and fuel sealing applications. It combines affordability with decent performance, making it a popular choice across automotive, hydraulic, and industrial sectors.
Key Properties:
- Good resistance to petroleum-based oils and fuels
- Temperature range: -40°C to +120°C
- Moderate abrasion resistance
- Economical and widely available
Applications:
- Fuel lines and carburetors
- Hydraulic systems
- Pneumatic tools
- Low-cost general-purpose seals
Best use case: Choose an NBR seal when the operating environment is stable, cost is a concern, and petroleum resistance is needed without exposure to aggressive chemicals or extreme temperatures.
EPDM (Ethylene Propylene Diene Monomer): The Weatherproof Warrior
An EPDM seal stands out for its exceptional weathering, ozone, and steam resistance. It’s ideal for outdoor applications or systems exposed to water-based fluids.
Key Properties:
- Excellent resistance to UV, ozone, and water
- Handles steam and glycol-based brake fluids
- Temperature range: -50°C to +150°C
- Poor compatibility with petroleum-based oils
Applications:
- HVAC systems
- Drinking water systems (FDA- and NSF-compliant variants)
- Outdoor electrical enclosures
- Brake systems (non-mineral oil based)
Best use case: Use an EPDM seal when sealing against water, steam, or environmental exposure is critical. Avoid if exposed to fuels or oils.
FKM (Fluoroelastomer): The Chemical and Heat Specialist
The FKM O ring (often referred to by the brand name Viton) is a premium sealing solution for demanding conditions, including high temperatures and aggressive chemicals.
Key Properties:
- Outstanding chemical resistance (hydrocarbons, acids, solvents)
- Temperature range: -20°C to +250°C (short bursts to 300°C)
- Excellent compression set resistance
- Limited cold flexibility compared to NBR or EPDM
Applications:
- Automotive fuel systems
- Chemical processing plants
- Aerospace engines and turbines
- High-temperature hydraulic systems
Best use case: The FKM O ring is the material of choice for systems involving aggressive chemicals, elevated heat, or a need for long service life with minimal maintenance.
Silicone: The Flexible Generalist
Silicone rubber seals offer flexibility, low toxicity, and excellent thermal stability. While not as durable in aggressive chemical environments, they shine in clean or medical applications.
Key Properties:
- Wide operating temperature range: -60°C to +230°C
- Soft and flexible
- Excellent for food, beverage, and medical use
- Poor resistance to oils and fuels
Applications:
- Medical equipment and implants
- Food-grade gaskets and tubing
- High-temp insulation systems
- Static seals in clean environments
Best use case: Choose silicone for sensitive applications requiring non-reactive, soft seals with high heat resistance but minimal chemical exposure.
Comparison Table: NBR vs. EPDM vs. FKM vs. Silicone
| Property | NBR Seal | EPDM Seal | FKM O Ring | Silicone |
| Temp Range | -40°C to +120°C | -50°C to +150°C | -20°C to +250°C | -60°C to +230°C |
| Oil/Fuel Resistance | Excellent | Poor | Excellent | Poor |
| Chemical Resistance | Moderate | Moderate | Outstanding | Low |
| UV/Ozone Resistance | Fair | Excellent | Good | Excellent |
| Flexibility | Moderate | High | Moderate | Excellent |
| Cost | Low | Moderate | High | Moderate |
Material and Application Matching
Understanding your application environment is essential when selecting a seal material:
- For automotive fuel systems: Use an FKM O ring to resist gasoline and engine heat.
- For water pumps or steam systems: Opt for an EPDM seal.
- For hydraulic cylinders: An NBR seal offers good performance at a low cost.
- For food-grade or cleanroom setups: Choose silicone for purity and flexibility.
Customization and Compound Variants
Many suppliers offer hybrid materials or compound formulations:
- Hydrogenated NBR (HNBR): Improved thermal and chemical resistance vs. standard NBR
- Peroxide-cured EPDM: Better compression set for static seals
- Specialty FKM blends: Enhanced low-temperature flexibility
Work with suppliers to match the right compound to your specific sealing challenge.
Real-World Case Studies
1. Hydraulic Repair Shop
A client replaced a failing NBR seal in a hydraulic press with an FKM O ring to handle higher operating temperatures and reduce swelling. Seal life doubled, and pressure losses dropped by 30%.
2. Solar Panel Manufacturer
Outdoor junction boxes previously using NBR seals began leaking. Switching to EPDM seals resolved the issue, with zero degradation after 12 months in full sun.
3. Pharma Equipment Supplier
For tablet presses, silicone gaskets were selected due to their FDA compliance and soft sealing. The system met regulatory audit with no modifications.
Maintenance, Storage, and Inspection
No matter the material, proper seal handling is essential:
- Store seals in cool, dry places away from UV light
- Avoid stretching during installation
- Use compatible lubricants to prevent swelling or degradation
- Regularly inspect for cracking, hardening, or chemical damage
By matching the NBR seal, EPDM seal, or FKM O ring to its proper application and maintaining it properly, you can dramatically reduce failure risk and downtime.
Emerging Trends in Seal Materials
- Bio-based elastomers: Lower carbon footprint, but still under development
- Smart seals: Embedded sensors to monitor wear, pressure, or chemical exposure
- Nanocomposite fillers: Improve mechanical strength and resistance
Expect future FKM O ring variants with enhanced flexibility and EPDM compounds that rival FKM’s chemical resistance.
Final Thoughts: Material Matters
Your seal is only as good as the material it’s made from. While the NBR seal may be perfect for a standard hydraulic application, it would fail quickly in a steam line or chemical washdown. Similarly, an EPDM seal can handle outdoor weathering with ease but won’t survive a splash of diesel. And while the FKM O ring might carry a premium price, it’s the best investment for long-term performance in harsh conditions.
The next time you spec out a seal, go beyond size and shape. Consider the environment, the fluid, the pressure, and the maintenance window. That way, your system runs cleaner, longer, and more efficiently—thanks to the right material, in the right place, doing the right job.
