Both resist heat. Both resist chemicals. But only one stretches—and the other slides. If you’re choosing between PTFE and fluoroelastomer, understanding their strengths could save your system from premature failure.
The key difference is that PTFE (polytetrafluoroethylene) is a rigid, non-elastomeric plastic with unmatched chemical resistance and low friction, while fluoroelastomer (FKM) is a flexible rubber used for sealing under compression.
In practice, I’ve seen customers confuse the two—expecting PTFE to behave like rubber, or assuming FKM resists everything PTFE does. They’re both fluorinated materials, but serve very different roles.
What is PTFE?
PTFE, commonly known as Teflon®, is a white, waxy polymer known for being nearly non-reactive and extremely slippery.
PTFE is a non-elastomeric fluoropolymer used for gaskets, seals, valve seats, and bushings in aggressive chemical environments and high-friction applications.
✅ Key Properties of PTFE
| Property | Performance |
|---|---|
| Temperature resistance1 | –200°C to +260°C |
| Chemical resistance2 | Outstanding – resists almost everything |
| Friction coefficient3 | Extremely low |
| Flexibility | Rigid, not elastic |
| Wear resistance | Moderate to good |
| Compression sealing | Poor unless filled or combined with rubber |
I use PTFE when sealing acids, solvents, or gases that destroy rubber—even FKM. It doesn’t flex, but it doesn’t break down either.
What is fluoroelastomer?
Fluoroelastomer (FKM), known by brand names like Viton®, is a flexible, chemically resistant rubber used in dynamic and static seals.
FKM is an elastomer that offers high heat resistance and good sealing performance in fuels, oils, and chemicals. It compresses and returns to shape, making it ideal for O-rings and shaft seals.
✅ Key Properties of Fluoroelastomer
| Property | Performance |
|---|---|
| Temperature resistance | –20°C to +230°C (some to 300°C) |
| Chemical resistance | Excellent in fuels, oils, many acids |
| Flexibility | Elastic and compressible |
| Friction coefficient | Moderate |
| Wear resistance4 | High |
| Dynamic sealing | Excellent |
We use FKM for rotary shaft seals in pumps, gearboxes, and engines. It’s flexible, seals under pressure, and holds up under temperature and chemical attack—within limits.
PTFE vs Fluoroelastomer: What’s the difference?
They’re both fluorinated and both high-end. But their physical properties and sealing mechanisms are fundamentally different.
PTFE is plastic, rigid, and used where motion or contact is a concern. FKM is rubber, compressible, and used where sealing is required under load.
🧪 Side-by-Side Comparison
| Property | PTFE | Fluoroelastomer (FKM) |
|---|---|---|
| Material type | Thermoplastic | Elastomer (rubber) |
| Flexibility | Rigid | Flexible, elastic |
| Chemical resistance | Best overall | Excellent but not universal |
| Temperature range | –200°C to +260°C | –20°C to +230°C (some to 300°C) |
| Sealing under compression | Requires backup/rubber | Excellent with proper groove |
| Friction resistance | Ultra-low | Medium |
| Wear under motion | May need fillers | Better for dynamic seals |
| FDA food-grade availability5 | ✅ Yes | ✅ Some grades |
| Color availability | White/off-white | Black, brown, green |
So: PTFE is unbeatable when nothing else will survive chemically. But it needs careful engineering to seal. FKM is more forgiving in grooves and easier to install.
When should you choose PTFE over FKM?
If the environment is extremely corrosive, the media is reactive, or you need ultra-low friction—go PTFE.
PTFE is best when sealing against harsh acids, solvents, or gases, especially where elasticity is not needed.
📌 Choose PTFE6 when:
- You’re sealing nitric, sulfuric, or hydrofluoric acid
- The temperature drops below –30°C
- The seal must not swell or deform under load
- You need a dry-lubricated contact surface7
We once supplied PTFE seats for a chlorine valve8 where rubber failed after two weeks. The PTFE parts ran two years with zero degradation.
When should you use FKM instead of PTFE?
If you need flexibility, dynamic sealing, or ease of installation, FKM is your material.
Fluoroelastomer is best in systems with oil, fuel, heat, and pressure—where flexible sealing is required.
📌 Choose FKM when:
- You're sealing crankshafts or pump shafts
- Fuel or hydraulic oil is involved
- The seal must compress and recover
- High pressure demands tight static sealing
We regularly use FKM in dynamic shaft seals9 for HVAC compressors10. Silicone or PTFE can’t handle the combination of movement and oil exposure—FKM can.
Can PTFE and FKM be used together?
Yes. In fact, some of the best-performing seals are hybrids.
PTFE is often used as a contact face in combination with an FKM energizer (spring or O-ring core), creating a seal that handles both motion and chemistry.
These composite seals are common in rotary unions, pharmaceutical valves, and high-pressure gas equipment.
Conclusion
PTFE and fluoroelastomer each dominate their own field—one for chemistry and slip, the other for compression and motion.
Need help choosing between PTFE and FKM for your sealing system?
Contact Julong Rubber or Request a Quote for molded FKM, machined PTFE, or hybrid seals.
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Understanding PTFE's temperature resistance is crucial for applications in extreme conditions. Explore this link for detailed insights. ↩
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PTFE's exceptional chemical resistance makes it ideal for various industries. Discover more about its advantages over other materials. ↩
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The low friction coefficient of PTFE is vital for reducing wear in mechanical applications. Learn more about its benefits and applications. ↩
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Wear resistance is key for durability in mechanical applications. Learn more about how fluoroelastomer excels in this aspect. ↩
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Knowing the FDA compliance of these materials is essential for food-related applications, ensuring safety and regulatory adherence. ↩
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Explore the advantages of PTFE, especially in harsh chemical environments, to understand its superior performance and durability. ↩
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Discover the concept of dry-lubricated surfaces and their benefits in reducing friction and wear in various applications. ↩
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Learn about chlorine valves and the materials that enhance their longevity and performance, including PTFE. ↩
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Learn about dynamic shaft seals to see how they function in various applications, including HVAC compressors, enhancing your knowledge of sealing technologies. ↩
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Discover the importance of HVAC compressors in climate control systems and how they utilize seals like FKM for efficiency. ↩
