PBT
misse2-pbtIn short
On the International Space Station's forward-facing side, oxygen atoms ate away 768 µm of PBT in 3.95 years, about 194 µm a year. A standard 25 µm film of it would last about 2 months there. It erodes 3.0 times faster than Kapton H, the reference film.
Benchmarks
The benchmarks that matter for this material's applications, each compared with the reference engineers use.
| Benchmark | Result | Compared with reference |
|---|---|---|
| Atomic oxygen erosionHow fast low-orbit oxygen eats the surface. Lower is better. | 9.11×10⁻²⁴ cm³/atomLow Earth orbit, 3.95 years in flight | 3.04× Kapton HErodes 3.0× faster |
Not measured yet (5): darkening under UV and particles (Δα); outgassing, total mass loss (TML); outgassing, condensable (CVCM); thermal cycling survival; flammability (crewed vehicles).
Applications
Where materials like PBT are considered, the benchmarks that decide each use, and what the measured data says so far.
| Application | Deciding benchmarks | What the data says |
|---|---|---|
| External surfaces in low Earth orbit1 of 2 deciding benchmarks measured |
| Atomic oxygen resistance is poor (3.04×): unprotected, it wears through quickly on forward-facing low-orbit surfaces and would need a protective coating. Still needed: darkening under UV and particles (Δα). |
| Thermal blankets (MLI) outer layer1 of 4 deciding benchmarks measured |
| Atomic oxygen resistance is poor (3.04×): unprotected, it wears through quickly on forward-facing low-orbit surfaces and would need a protective coating. Still needed: darkening under UV and particles (Δα); outgassing, total mass loss (TML); outgassing, condensable (CVCM). |
"What the data says" is Space Mushroom's reading of the measured values, not a flight qualification. Deciding benchmarks come from the Benchmark Framework.
What it went through
| Where | ISS, MISSE 2, PEC 2 tray 1 (outside the Quest airlock) |
|---|---|
| When | 2001-08-16 to 2005-07-30 (3.95 years) |
| Atomic oxygen dose | 8.43×10²¹ atoms/cm² |
| Sunlight | 5,000–6,700 equivalent sun hours |
| Temperature | Cycled between −30 °C and 40 °C |
| Also exposed to | Solar UV and charged particle radiation, in vacuum |
How it compares
Materials flown on the same tray, ranked from least to most eroded. PBT is number 38 of 40.
| Rank | Material | Compared with Kapton H | Lost in 3.95 years |
|---|---|---|---|
| 5 | FEPFluorinated ethylene propylene | 0.067× | 17 µm |
| 25 | Kapton HPolyimide (PMDA) | 1.00× | 253 µm |
| 36 | PMMAPolymethyl methacrylate | >1.87× | >472 µm |
| 37 | CR-39Allyl diglycol carbonate | >2.27× | >573 µm |
| 38 | PBTPolybutylene terephthalate | 3.04× | 768 µm |
| 39 | DelrinPolyoxymethylene (acetal) | 3.05× | 771 µm |
| 40 | Upilex-SPolyimide (BPDA) | 3.07× | 777 µm |
How the numbers are calculated
- Erosion yield is NASA's measurement: volume of material removed per oxygen atom.
- Thickness lost = erosion yield × oxygen dose = 9.11×10⁻²⁴ cm³/atom × 8.43×10²¹ atoms/cm² = 0.0768 cm = 768 µm.
- Compared with Kapton H = erosion yield ÷ 3.00×10⁻²⁴ (Kapton H's value on the same flight).
- Film life = 25 µm ÷ 194 µm per year, for the same exposure.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0.
spore: passport
id: misse2-pbt
spore_version: 0.1
status: measured
org: nasa
dataset: misse2-peace
material:
name: "Polybutylene terephthalate"
abbreviation: "PBT"
family: Other polymer
category: polymers
type: polyesters
tags:
environments: [low-earth-orbit]
stresses: [atomic-oxygen, uv, total-radiation-dose, thermal-cycling, vacuum-and-outgassing]
applications: []
exposures:
- environment: low Earth orbit
platform: ISS, MISSE 2, PEC 2 tray 1 (outside the Quest airlock)
start: 2001-08-16
end: 2005-07-30
duration_years: 3.95
atomic_oxygen_fluence: {value: 8.43e21, unit: atoms/cm2}
solar_exposure: {value: "5000-6700", unit: equivalent sun hours}
thermal_cycling: {min_c: -30, max_c: 40, note: nominal base-plate range}
results:
- property: atomic oxygen erosion yield
value: 9.11e-24
unit: cm3/atom
lower_bound: false
sources:
- title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
id: NASA/TM-2008-215490 (Banks, Backus and de Groh, December 2008)
url: https://ntrs.nasa.gov/citations/20090011780
where: Table I; exposure details in section 2.1
license: CC-BY-4.0
Sources
- Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit. NASA/TM-2008-215490 (Banks, Backus and de Groh, December 2008), Table I; exposure details in section 2.1.