Epxvalues describe: Torr Seal class
Quantum hardwareBig science (accelerators, light sources, public fusion)Space test
Why it wins
The named exceptions to the adhesive ban: leak patching, feedthrough potting, cryogenic bonding, conductive attach. Each grade exists because it passed outgassing screening; nothing else in the glue aisle did.
Why not the alternative
Generic epoxies and CA glues outgas uncharacterized; that is the whole reason the anti-table exists.
Watch out
Mind bake ceilings and CTE mismatch at cryo: fillets crack windows.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated.
Provisional provenance: NASA outgassing database; ECSS space product assurance standards.
Wet cleaning
| Recipe | substrates solvent-cleaned and abraded before bonding; the joint itself is never cleaned after |
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| Forbidden | mould release or silicone anywhere near the bond line |
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| Limit | the full cure schedule: an undercured joint outgasses for months |
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Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-7 mbar·L/s/cm² |
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| Outgassing, baked | 1e-9 mbar·L/s/cm² |
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| Vapour pressure | uncured resin is far worse than cured; the cure schedule is the specification |
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Temperature
| Bake, assembled | 120 °C |
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| Vacuum degas | 150 °C |
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| Metallurgical limit | Tg 60–150 °C by system |
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Thermal
| CTE | 60 ppm/K |
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| Thermal conductivity | 0.2 W/m·K |
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| Specific heat | 1100 J/kg·K |
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| Emissivity | 0.9 |
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Mechanical
| Strength | 30–70 tens MPa |
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| Tensile | 30–70 MPa |
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| Elongation | 2–5 % |
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| Young's modulus | 3 GPa |
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| Density | 1.15 g/cm3 |
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Electrical and magnetic
| Relative permeability | 1.0 |
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| Resistivity | >1e14 Ω·cm |
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| Dielectric strength | 15–20 kV/mm |
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Engineering
| Corrosion | moderate |
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| Joining | it is the joint |
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| Process notes | every joint is an outgassing source and a future leak |
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| Availability and cost | commodity |
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Outgassing
1 sourced measurement for this card, 1 declared absence.
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/.
Sourced outgassing measurements for this card| Material as published | Species | State | Pumping time | Rate |
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| MasterBond EP30-2 epoxy | total | not-stated | NOT STATED by the source | 7.47e-11mbar·L/s/cm² |
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- Epo-Tek 353ND epoxy. A single outgassing figure of 1e-15 torr-liter/s/cm2 is published for this epoxy, but the species column it belongs to could not be resolved.Row A14 of Table 1 carries one number across four species columns, JTotal, Jwater, JH2 and JHC, and the column alignment did not survive text extraction of the source. Nothing is written rather than guessing the species. Underlying qualification documents named by the table: LIGO-E1300653-v1 and LIGO-E1300654-v1.
Sources: S-LIGO-E960050-V13. Full citations and conditions at
the base and in /data/outgassing.json.
Grades
| Torr Seal (Hysol 1C) | the leak-stop and general vacuum epoxy |
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| Stycast 2850FT | filled, CTE-matched: the cryogenic potting standard |
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| Stycast 1266 | unfilled, low viscosity, cryo impregnation |
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| EPO-TEK H20E | silver conductive attach |
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| EPO-TEK H77 | thermal, insulating attach |
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Sources · 2
- NASA outgassing database
- Henkel and Epoxy Technology datasheets
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