Relative permittivity of PTFE
| Value | 2.06 — |
| Status | Typical value: varies by about ± 0.04 — in practice |
| Source | NIST Technical Note 1520 (Baker-Jarvis et al., 2001), Dielectric and Conductor-Loss Characterization and Measurements on Electronic Packaging Materials, Table 5: PTFE 2.06, loss tangent 0.0002 |
| Categories | ElectromagneticMaterial Properties |
| Unit | Value |
|---|---|
| ratio | 2.06 — |
| percent | 206 % |
| part per trillion | 2,060,000,000,000 ppt |
| part per billion | 2,060,000,000 ppb |
| part per million | 2,060,000 ppm |
| per cent mille | 206,000 pcm |
| basis point | 20,600 bp |
| per mille | 2,060 per mille |
Learning zone
Roy Plunkett was working on refrigerants at DuPont in 1938 when a cylinder of tetrafluoroethylene stopped delivering gas but still weighed full. He sawed it open and found a waxy white polymer that nothing would stick to, dissolve or attack. PTFE's electrical virtues turned out to be as remarkable as its chemical ones: a relative permittivity of about 2.06 that barely moves with frequency or temperature, and a loss tangent around 0.0002.
That combination made it the dielectric of choice for RF and microwave work. Semi-rigid coaxial cable, PTFE-filled connectors, and low-loss printed-circuit laminates all rely on it, and its low permittivity means a larger conductor diameter for a given impedance, which cuts loss further. Expanded PTFE with trapped air drops the effective value toward 1.4, giving the fastest propagation velocity of any practical cable dielectric: around 80% of the speed of light.
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formula.expert. (2026, November 8). Relative permittivity of PTFE. https://formula.expert/constants/relative-permittivity-ptfe