PTFE (Polytetrafluoroethylene) is a versatile fluoropolymer known for its unique combination of properties, including chemical resistance, low friction, and high-temperature stability. Its Shore D hardness is 55, measured per ASTM D2240, indicating a moderately soft material that still offers durability. The compression strength is 5 MPa at 1% deformation (ASTM D695), reflecting its ability to withstand moderate loads while maintaining structural integrity. These properties make PTFE suitable for applications requiring flexibility, non-reactivity, and resistance to wear, though filler additives can enhance hardness and strength for more demanding uses.
Key Points Explained:
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Shore Hardness of PTFE
- PTFE has a Shore D hardness of 55 (ASTM D2240).
- Shore D scale measures harder plastics and elastomers (range: 0–100).
- A value of 55 indicates PTFE is softer than many engineering plastics (e.g., nylon ~80D) but retains enough rigidity for structural applications.
- This moderate hardness contributes to its flexibility and non-abrasive nature, ideal for seals and bearings.
- PTFE has a Shore D hardness of 55 (ASTM D2240).
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Compression Strength of PTFE
- Compression strength is 5 MPa at 1% deformation (ASTM D695).
- ASTM D695 evaluates a material’s resistance to compressive forces.
- PTFE’s low compression strength limits its use in high-load scenarios unless reinforced with fillers (e.g., glass or carbon fibers).
- For custom PTFE parts, fillers can significantly improve strength and wear resistance while retaining core benefits like chemical inertness.
- Compression strength is 5 MPa at 1% deformation (ASTM D695).
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Factors Influencing PTFE Properties
- Fillers: Additives like glass (15–40% typical) can increase hardness (up to 65–70 Shore D) and compression strength (up to 15–20 MPa).
- Temperature: PTFE maintains properties from -200°C to +260°C, but creep (cold flow) can reduce effective strength under prolonged load.
- Design Considerations: For compression-heavy applications, thicker walls or support structures may compensate for PTFE’s inherent softness.
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Trade-offs and Applications
- PTFE’s low compression strength and moderate hardness are balanced by its nonstick surface, chemical resistance, and biocompatibility.
- Common uses:
- Gaskets and seals (where deformation under load is acceptable).
- Liners for corrosive environments (leveraging chemical resistance).
- Low-friction components (e.g., bushings) in machinery.
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Standards and Testing
- Hardness: ASTM D2240 ensures consistency across batches.
- Compression: ASTM D695 provides comparable data for engineering design.
- For critical applications, additional tests (e.g., creep resistance per ASTM D2990) may be necessary.
PTFE’s properties make it a niche material where performance outweighs structural limitations. For tailored solutions, custom PTFE parts with fillers or hybrid designs can bridge gaps in hardness and strength. Would a filler-enhanced formulation better suit your project’s load requirements?
Summary Table:
| Property | Value (ASTM Standard) | Notes |
|---|---|---|
| Shore D Hardness | 55 (ASTM D2240) | Moderately soft, ideal for seals and bearings. |
| Compression Strength | 5 MPa (ASTM D695) | Suitable for moderate loads; fillers can improve strength. |
| Temperature Range | -200°C to +260°C | Maintains properties across extreme temperatures. |
| Filler Enhancements | Up to 65–70 Shore D | Glass/carbon fibers boost hardness and compression strength. |
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