Teflon encapsulated O-rings are highly resistant to compression set, making them ideal for long-term sealing applications in harsh environments. Their design combines the elasticity of an elastomer core with the chemical and thermal resistance of a Teflon (PTFE, FEP, or PFA) outer layer, ensuring dimensional stability and sealing integrity even under prolonged compression. While they excel in most chemical exposures, certain aggressive substances like hydrofluoric acid and extreme conditions (e.g., molten alkali metals, fluorinating agents, or temperatures beyond their rated limits) can compromise performance. Their compression set resistance is a key factor in their reliability for critical sealing tasks.
Key Points Explained:
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Compression Set Resistance
- Teflon encapsulated O-rings exhibit excellent compression set resistance, meaning they retain their original shape and sealing force after prolonged compression. This is critical for applications where seals must maintain integrity over time without frequent replacement.
- The elastomer core provides resilience, while the Teflon (seal teflon o ring) encapsulation adds durability against deformation.
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Material Composition and Performance
- The combination of an elastomer (e.g., silicone or Viton) with Teflon (PTFE, FEP, or PFA) balances flexibility and chemical resistance.
- Temperature limits: FEP withstands up to 200°C, while PFA handles up to 260°C. Beyond these thresholds, compression set resistance may degrade.
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Chemical Compatibility
- These O-rings resist most acids, bases, and solvents (rated 8–10 on the chemical resistance scale).
- Exceptions: Hydrofluoric acid (HF), molten alkali metals, and strong fluorinating agents can damage the Teflon layer, indirectly affecting compression set performance.
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Mechanical Stress Considerations
- While resistant to compression set, excessive mechanical stress (e.g., over-tightening) can cause permanent deformation. Proper gland design and installation are essential to maximize longevity.
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Applications in Harsh Environments
- Their stability under compression makes them suitable for aerospace, chemical processing, and high-temperature industrial systems where seals face constant pressure and aggressive media.
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Limitations
- Avoid direct flame or extreme thermal cycling, as rapid temperature changes may reduce elasticity and increase compression set risk over time.
By understanding these factors, purchasers can confidently select Teflon encapsulated O-rings for demanding applications where compression set resistance is paramount.
Summary Table:
| Feature | Benefit |
|---|---|
| Compression Set Resistance | Retains shape and sealing force under prolonged compression |
| Material Composition | Elastomer core + Teflon (PTFE/FEP/PFA) for flexibility + chemical resistance |
| Temperature Limits | FEP: 200°C, PFA: 260°C (beyond these, performance may degrade) |
| Chemical Compatibility | Resists most acids/bases/solvents (avoid HF, molten alkali metals, fluorinating agents) |
| Applications | Aerospace, chemical processing, high-temperature industrial systems |
| Limitations | Avoid direct flame, extreme thermal cycling, or over-tightening |
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