Polymers and elastomers · Banned
Standard elastomers (Buna-N, EPDM)
NBRvalues describe: NBR
Why it's out
Plasticizer outgassing and high permeation.
Where it hides
Fine in rough vacuum, banned beyond.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: O'Hanlon, A User's Guide to Vacuum Technology; NASA outgassing database.
Wet cleaning
| Recipe | IPA wipe if used in rough vacuum |
|---|---|
| Forbidden | expecting it to survive a bake |
| Limit | the temperature ceiling |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 0.000005 mbar·L/s/cm² |
|---|---|
| Outgassing, baked | not bakeable |
| Vapour pressure | continuous plasticiser evolution |
Temperature
| Bake, assembled | 100 °C |
|---|---|
| Metallurgical limit | THE CONDEMNING NUMBER: 100–120 °C maximum, so no real bakeout is possible, on top of the worst outgassing rate in common use |
Thermal
| CTE | 230 ppm/K |
|---|---|
| Thermal conductivity | 0.25 W/m·K |
| Specific heat | 1900 J/kg·K |
| Emissivity | 0.9 |
Mechanical
| Strength | 10–20 tens MPa |
|---|---|
| Tensile | 10–20 MPa |
| Elongation | 300–500 % |
| Young's modulus | 0.005 GPa |
| Hardness | 70–80 Shore A |
| Density | 1.2 g/cm3 |
Electrical and magnetic
| Relative permeability | 1.0 |
|---|
Engineering
| Corrosion | poor against ozone and oxidisers |
|---|---|
| Joining | compressed in a groove |
| Process notes | rough vacuum only |
| Availability and cost | the cheapest seal there is |
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-4 unbaked to no baked reading baked.
| Material as published | Species | State | Pumping time | Rate |
|---|---|---|---|---|
| Neoprene | H2O | unbaked | 10 h | about1.00e-5mbar·L/s/cm² |
| Neoprene | total | unbaked | the abscissa of the curve below | 4.00e-5 at 1 h to 2.40e-5 at 4 h |
| Neoprene | total | unbaked | the abscissa of the curve below | 4.00e-6 at 1 h to 1.93e-6 at 4 h |
Sources: S-CHIGGIATO-CAS-2017, S-ELSEY-1975-II. Full citations and conditions at the base and in /data/outgassing.json.