The dielectric strengths of PTFE products are primarily defined by ASTM standards, which vary based on product form and thickness. Thin films can exceed 250 kV/mm, while thicker materials may drop to 20 kV/mm. Key standards include ASTM D4894 for resins, D3293 for sheets (4-24 kV/mm), D3294 for shapes (12-24 kV/mm), D3295 for thin-walled tubes (35-55 kV/mm), D3308 for skived tapes (20-250 kV/mm), and D1710 for thick-walled tubes (10-30 kV/mm). PTFE maintains stable dielectric performance up to 300°C, with strength inversely related to thickness and frequency.
Key Points Explained:
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ASTM Standards for PTFE Dielectric Strength
- Granular resins: ASTM D4894 (no specific kV/mm range provided)
- Sheets: ASTM D3293 (4–24 kV/mm)
- Basic shapes: ASTM D3294 (12–24 kV/mm)
- Thin-walled tubes: ASTM D3295 (35–55 kV/mm)
- Skived tapes: ASTM D3308 (20–250 kV/mm)
- Thick-walled tubes: ASTM D1710 (10–30 kV/mm)
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Thickness Dependency
- Thin films (<15 µm) can exceed 250 kV/mm due to reduced defect density.
- Thicker materials (100+ µm) exhibit lower strengths (~20 kV/mm) as voids and impurities scale with volume.
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Frequency and Temperature Stability
- Dielectric strength decreases with higher frequencies but remains stable up to 300°C, critical for high-temperature applications like aerospace or custom PTFE parts.
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Complementary Dielectric Properties
- Dielectric constant: 2–13 (frequency-dependent)
- Dissipation factor: 0.0004 (minimal energy loss)
- Volume resistivity: >10¹⁶ ohm/cm (excellent insulation)
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Design Considerations for Purchasers
- Prioritize ASTM-compliant materials for traceability.
- Match thickness to voltage requirements (e.g., thin films for high-voltage tapes).
- Verify thermal stability if used in extreme environments.
For tailored applications, consult manufacturers to align ASTM standards with performance needs, especially for custom PTFE parts requiring non-standard dimensions or operating conditions.
Summary Table:
| PTFE Product Form | ASTM Standard | Dielectric Strength Range (kV/mm) |
|---|---|---|
| Granular resins | ASTM D4894 | Not specified |
| Sheets | ASTM D3293 | 4–24 |
| Basic shapes | ASTM D3294 | 12–24 |
| Thin-walled tubes | ASTM D3295 | 35–55 |
| Skived tapes | ASTM D3308 | 20–250 |
| Thick-walled tubes | ASTM D1710 | 10–30 |
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