PTFE (Polytetrafluoroethylene) generally exhibits a hardness range of 50-60 on the Shore D scale, with a typical value around 55D. This places it on the softer end of the spectrum compared to engineering plastics like Nylon or PEEK, which often exceed 80D. The material's hardness can be modified slightly through the addition of fillers like glass or carbon, but its inherent properties prioritize chemical resistance and thermal stability over rigidity. For applications requiring custom PTFE parts, this hardness range balances flexibility with sufficient structural integrity for most non-load-bearing uses.
Key Points Explained:
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Standard Hardness Range (50-60 Shore D)
- Multiple references confirm PTFE consistently falls within this range, with 55D being the most frequently cited value.
- Measured per ASTM D2240 standards, ensuring reproducibility across testing conditions.
- The softness stems from PTFE's molecular structure, which prioritizes low friction and chemical inertness over rigidity.
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Comparative Softness vs. Other Plastics
- Materials like Nylon (80-85D) and PEEK (85-95D) are significantly harder, making PTFE unsuitable for high-stress mechanical applications.
- This trade-off is intentional: PTFE excels in non-abrasive environments where lubrication-free movement or chemical resistance is critical.
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Effect of Fillers on Hardness
- Additives like glass fibers or carbon can marginally increase hardness (e.g., 5-10% higher), but PTFE's core properties remain dominant.
- Useful for custom PTFE parts requiring enhanced wear resistance without sacrificing thermal stability (-200°C to 260°C).
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Practical Implications for Purchasers
- Flexibility vs. Rigidity: The 50-60D range allows PTFE to conform to irregular surfaces (e.g., gaskets) while maintaining shape under light loads.
- Load Considerations: With a compressive strength of only 5 MPa at 1% deformation, PTFE isn't ideal for heavy structural components.
- Temperature Resilience: Hardness remains stable across its extreme temperature range, unlike materials that become brittle or soften.
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Testing and Specification Clarity
- Always verify hardness data aligns with ASTM D2240 to ensure comparability.
- For critical applications, request certified test reports from suppliers, especially for filled PTFE variants where hardness may vary.
This balance of properties makes PTFE a versatile choice for seals, liners, and insulating components—applications where hardness is secondary to performance in harsh environments.
Summary Table:
| Property | PTFE (Shore D) | Comparative Materials |
|---|---|---|
| Hardness Range | 50-60 | Nylon (80-85D), PEEK (85-95D) |
| Key Characteristics | Low friction, chemical inertness | High rigidity, mechanical strength |
| Effect of Fillers | Slight increase (5-10%) | N/A |
| Temperature Stability | -200°C to 260°C | Varies by material |
| Best Applications | Seals, liners, insulating components | High-stress mechanical parts |
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