Polymers and elastomers · Banned
PTFE (Teflon)
PTFEvalues describe: virgin PTFE
Why it's out
Cold flow under clamp load, high permeation, radiation damage. Not banned everywhere, rationed everywhere.
Where it hides
Scroll pump tip seals (a known particle and outgassing source), limited wire insulation.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: NASA outgassing database; O'Hanlon, A User's Guide to Vacuum Technology.
Wet cleaning
| Recipe | IPA wipe, then bake |
|---|---|
| Forbidden | using it as a structural seal, which is the actual ban |
| Limit | creep, not chemistry |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-7 mbar·L/s/cm² |
|---|---|
| Outgassing, baked | 1e-9 mbar·L/s/cm² |
| Vapour pressure | low; fluorinated fragments above 260 °C |
Temperature
| Bake, assembled | 200 °C |
|---|---|
| Vacuum degas | 200 °C |
| Metallurgical limit | THE CONDEMNING MECHANISM: cold flow under any sustained load, far below its 327 °C melt |
Thermal
| CTE | 135 ppm/K |
|---|---|
| Thermal conductivity | 0.25 W/m·K |
| Specific heat | 1000 J/kg·K |
| Emissivity | 0.9 |
| Melting / softening | 327 °C |
Mechanical
| Strength | 20–35 tens MPa |
|---|---|
| Tensile | 20–35 MPa |
| Elongation | 200–400 % |
| Young's modulus | 0.5 GPa |
| Hardness | 50–55 Shore D |
| Density | 2.2 g/cm3 |
Electrical and magnetic
| Relative permeability | 1.0 |
|---|---|
| Resistivity | >1e18 Ω·cm |
| Dielectric strength | 60 kV/mm |
Engineering
| Corrosion | inert to essentially everything |
|---|---|
| Joining | not bondable without etching |
| Process notes | fine as wire insulation, never as a gasket |
| Availability and cost | commodity |
Outgassing
3 sourced measurements for this card. A rate means nothing without the pumping time it was read at, so each one states it or declares it missing. The whole base, filters included, is at /tools/outgassing/.
Signature: 1e-6 unbaked to no baked reading baked.
| Material as published | Species | State | Pumping time | Rate |
|---|---|---|---|---|
| Gaflon (PTFE) (fresh) | total | unbaked | the abscissa of the curve below | 2.21e-7 at 1 h to 4.41e-8 at 10 h |
| PTFE | total | unbaked | the abscissa of the curve below | 4.00e-7 at 1 h to 2.00e-7 at 10 h |
| Teflon | total | unbaked | the abscissa of the curve below | 8.67e-8 at 1 h to 3.33e-8 at 10 h |
Sources: S-ELSEY-1975-II. Full citations and conditions at the base and in /data/outgassing.json.