Both resist heat. Both are rubbers. But not all high-performance elastomers are created equal. Silicone and fluoroelastomer may look similar—but choosing the wrong one can wreck a sealing system.
The main difference is that silicone offers excellent flexibility and temperature resistance, while fluoroelastomer (FKM) provides superior chemical and fuel resistance.
I often help customers pick between these two materials. They’re both premium options, but what works in a bakery won’t survive in a diesel pump—and vice versa.
What is silicone rubber best for?
Silicone is soft, flexible, and survives extreme heat and cold. It’s also biocompatible, making it ideal for food, medical, and clean applications.
Silicone rubber is best used where temperature swings, non-reactivity, and softness are needed—especially in static sealing or sensitive applications.
✅ Common Features of Silicone
| Feature | Performance |
|---|---|
| Temperature range1 | –60°C to +230°C (some to +300°C) |
| Flexibility | Excellent, even at low temps |
| Chemical resistance2 | Moderate, not for oils or fuels |
| Food/medical approval3 | Easily meets FDA, USP, biocompatible |
| Typical hardness | 30–70 Shore A (very soft options) |
I often recommend silicone for food-grade applications, low-pressure enclosures, or static gaskets in hot environments. It’s soft and stable—but not for harsh chemicals.
What is fluoroelastomer best for?
Fluoroelastomer (FKM, known by brands like Viton®) is a tougher, more chemically resistant rubber used for oils, fuels, acids, and high-pressure dynamic sealing.
Fluoroelastomer is ideal for oil exposure, fuel handling, engine seals, and chemical plant applications where aggressive media are present.
✅ Common Features of FKM
| Feature | Performance |
|---|---|
| Temperature range | –20°C to +230°C (some to +300°C) |
| Chemical resistance | Excellent—fuels, oils, acids, solvents |
| Compression set4 | Very low—good for long-term sealing |
| Abrasion resistance5 | Higher than silicone |
| Typical hardness | 60–90 Shore A |
We use FKM for crankshaft seals, pump shafts, and valve stems exposed to oil, fuel, or cleaning agents. It holds shape and performance under pressure.
Head-to-head comparison: Silicone vs Fluoroelastomer
Both materials serve high-performance roles, but they excel in different conditions. Here’s how they compare side by side:
🧪 Material Comparison Table
| Property | Silicone | Fluoroelastomer (FKM) |
|---|---|---|
| Max temp (continuous) | +230°C (short bursts to 300°C) | +230°C (some grades to 300°C) |
| Low temp flexibility | Excellent (down to –60°C) | Fair (typical limit –20°C) |
| Oil/fuel resistance6 | ❌ Poor | ✅ Excellent |
| Chemical resistance | Good (water, alcohols) | Excellent (fuels, solvents) |
| FDA/medical compliance7 | ✅ Yes | Only some grades |
| Wear resistance | Moderate | High |
| Color availability | Wide (translucent, white, red) | Mostly black or dark brown |
| Cost | Moderate | Higher |
So if you're sealing steam or a bakery oven—go silicone. If it's a fuel pump, hydraulic valve, or refinery tank—go FKM.
When to use silicone vs FKM in real-world projects?
It depends on the media, temperature, and movement in your system.
Use silicone for static, clean, or food-safe sealing in hot or cold environments. Use fluoroelastomer for oil contact, dynamic sealing, or aggressive chemicals.
📌 Example Applications
| Application | Recommended Rubber | Why |
|---|---|---|
| Oven door gasket | Silicone8 | High-temp + flexibility + food safe |
| Fuel injector O-ring | FKM9 | Fuel resistance + heat |
| Medical device diaphragm | Silicone | Biocompatible10 and soft |
| Oil pump shaft seal | FKM | Handles pressure + lubricant contact |
| Brewery cleaning port | Silicone | Handles steam, safe for food |
| Gearbox input seal | FKM | Resists oil and dynamic motion |
A client once used silicone seals in a diesel engine part. They failed in under a month due to fuel swelling. We replaced them with FKM—no issues since.
Conclusion
Silicone and fluoroelastomer serve different worlds. Silicone wins in flexibility and cleanliness. FKM wins in durability and chemical strength.
Need help choosing the right rubber for your sealing job?
Contact Julong Rubber or Request a Quote for molded silicone or FKM parts.
Or talk directly on WhatsApp:
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Understanding the temperature range of silicone can help you choose the right material for your specific application needs. ↩
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Exploring silicone's chemical resistance will guide you in selecting the right material for environments with specific chemical exposure. ↩
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Learning about silicone's FDA and USP approvals ensures safety and compliance for food-grade and medical applications. ↩
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Learning about compression set can guide you in selecting seals that maintain effectiveness over time, crucial for reliability. ↩
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Exploring abrasion resistance will provide insights into material longevity and performance in demanding environments. ↩
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Understanding the oil and fuel resistance of these materials can help you choose the right one for your application. ↩
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Learning about FDA compliance can ensure that the materials you choose meet safety standards for medical applications. ↩
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Explore the advantages of silicone, especially in high-temp and food-safe applications, to understand its versatility and safety. ↩
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Learn about FKM's unique properties that make it ideal for fuel resistance and heat applications, enhancing your material knowledge. ↩
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Discover the importance of biocompatibility in medical devices and how it ensures safety and effectiveness for patients. ↩
