Colorless polyimide CP1 film PI (CP1)

spore: profile
id: pi-cp1
spore_version: 0.2
family: polyimides
name: Colorless polyimide CP1 film
abbreviation: PI (CP1)
role: flexible, optically clear polyimide film for thin-film space structures
category: polymers
type: polyimides
summary: |
  CP1 is a colorless, fluorinated aromatic polyimide film developed at NASA Langley and now made under licence by NeXolve (formerly SRS Technologies). In MISSE 2 it eroded by atomic oxygen at 1.91e-24 cm3/atom, a little under Kapton HN at 2.81e-24. Under simulated space radiation it darkened far more than Kapton, with its solar absorptance rising by more than 0.3 without saturating. A 2 micrometre CP1 film with a vapour-deposited aluminum coating was deployed as a 20 square metre solar sail in 2005.
best_for: Thin, clear, flexible film for solar sails and sunshades where the film stays uncoated in orbit only for short times
weakest_at: Optical darkening under UV and particle radiation (solar absorptance rose more than 0.3 in simulation), and atomic-oxygen erosion of exposed film
identity:
  formula: C46H22O6N2F12 (repeat unit; fluorinated aromatic polyimide)
  source: banks2008
  where: Table IV (formula C46H22O6N2F12 and atomic mass 926.6656 g/mole for PI (CP1)); Table V lists 88 atoms per repeat unit, including 12 fluorine. Russell et al. (AIAA-2001-1414) state that all of the films tested are aromatic polyimides
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
    - uv
    - total-radiation-dose
  applications:
    - structures
    - thermal-control
properties:
  - benchmark: density
    label: Density
    value: 1.4193
    unit: g/cm3
    scope: material
    conditions:
      specimen: PI (CP1) polymer sample used in the MISSE 2 PEACE polymers experiment
      use: density needed to convert mass loss into erosion yield
    method: Density measurement made for the experiment and listed in the NASA report (which cites its references 11 and 12 for the experiment)
    status: ground
    source: banks2008
    where: Table II (MISSE 2 PEACE polymers density and fractional ash content), column 'Density, ref. 12, rho'
  - benchmark: atomic_oxygen_erosion_yield
    label: Atomic oxygen erosion yield, MISSE 2 flight
    value: 1.91e-24
    unit: cm3/atom
    scope: material
    conditions:
      platform: MISSE 2 PEACE polymers tray, ISS, outside the Quest airlock
      fluence: 8.43e21 atoms/cm2 (average of two fluence witness samples)
      exposure: 2001-08-16 to 2005-07-30, about 3.95 years
    method: Mass loss divided by density and atomic oxygen fluence, as reported in the NASA predictive-tool report
    status: flight
    source: banks2008
    where: Table I (MISSE 2 PEACE polymers erosion yield data), row PI (CP1); fluence from the text of section 2
  - benchmark: predicted_atomic_oxygen_erosion_yield
    label: Predicted atomic oxygen erosion yield
    value: 2.27e-24
    unit: cm3/atom
    scope: material
    conditions:
      model: NASA predictive equation from the same report, fitted to the MISSE 2 data
    method: Predicted value from the predictive tool. It is a model output, not a measurement
    status: calculated
    source: banks2008
    where: Table VII (comparison of predicted and actual MISSE 2 erosion yields), row PI (CP1)
  - benchmark: molar_mass
    label: Molar mass of the repeat unit
    value: 926.6656
    unit: g/mole
    scope: material
    conditions:
      formula: C46H22O6N2F12
    method: Atomic mass of the repeat unit as printed in the NASA table
    status: calculated
    source: banks2008
    where: Table IV (MISSE 2 PEACE polymers chemical structure), row PI (CP1)
  - benchmark: volume_per_repeat_unit
    label: Volume per repeat unit
    value: 1.08e-21
    unit: cm3
    scope: material
    conditions:
      basis: volume per repeat unit calculated for the predictive tool
    method: Calculated value from the predictive-tool data set, not a measured value
    status: calculated
    source: banks2008
    where: Table IV, column 'Volume per repeat unit, V r', row PI (CP1)
  - benchmark: minimum_volume_of_atoms
    label: Minimum volume of atoms in the repeat unit
    value: 1.24e-22
    unit: cm3
    scope: material
    conditions:
      basis: sum of atomic volumes in the repeat unit
    method: Calculated value from the predictive-tool data set, not a measured value
    status: calculated
    source: banks2008
    where: Table IV, column 'Minimum volume of atoms in repeat unit, V-Sigma', row PI (CP1)
  - benchmark: ash_fraction
    label: Fractional ash content
    value: 0.00171
    unit: mass fraction
    scope: material
    conditions:
      specimen: PI (CP1) MISSE 2 PEACE polymers sample
    method: Mass fraction of polymer that is ash, measured for the experiment
    status: ground
    source: banks2008
    where: Table II, column 'Mass fraction of polymer that is ash, Na', row PI (CP1)
  - benchmark: film_thickness
    label: Film thickness of the uncoated flight sample
    value: 1
    unit: mil
    scope: material
    conditions:
      sample: uncoated CP1, MISSE-1 and MISSE-2 flight samples in the NASA memo
    method: Thickness as printed in the NASA memo (the sample description)
    status: ground
    source: ntrs2015
    where: Section 3.1 (Uncoated Colorless Polyimide 1) and its figure 4 description
  - benchmark: atomic_oxygen_seam_failure_fluence
    label: Atomic oxygen fluence at which the butt-joint seam failed
    value: 180000000000000000000
    unit: atoms/cm2
    scope: material
    conditions:
      sample: 1 mil uncoated CP1 with an adhesive-free butt-joint seam, MISSE-2
      exposure: ISS, wake side, Kapton witness sample underneath
    method: Seam failure detected by the Kapton witness sample underneath; the memo says the sample survived about 2e20 atoms/cm2 without a seam failure
    status: flight
    source: ntrs2015
    where: Section 3.1, text on figure 4 (MISSE-2 uncoated CP1 with butt joint seam)
  - benchmark: solar_absorptance_increase
    label: Increase in solar absorptance after simulated space radiation (CP film group)
    value: 0.3
    unit: decimal (solar absorptance)
    scope: material
    conditions:
      exposure: simulated L1/L2 electron and proton radiation plus about 1000 equivalent solar hours UV, in vacuum
      films: CP-1, CP-2 and TOR film samples as a group; the text says the increase was more than 0.3 without saturating
    method: Solar absorptance computed from in situ reflectance measurements; the memo gives this as a lower bound for the group, not a value for CP1 alone
    status: ground
    source: russell2001
    where: Results section, paragraph beginning 'The changes in solar absorptance from Kapton and Upilex samples remain less than 0.1'
  - benchmark: solar_absorptance
    label: Solar absorptance of colorless films before and after irradiation
    value: 0.2
    value_high: 0.5
    unit: decimal (solar absorptance)
    scope: material
    conditions:
      films: colorless polyimide films (CP group), as a group
      exposure: simulated L1/L2 radiation and UV, as printed in the text
    method: Text summary of the solar absorptance change, read from the paper's results section; the paper gives the range as 'from about 0.2 to nearly 0.5'
    status: ground
    source: russell2001
    where: Results section, paragraph on colorless films doubling their solar absorptance
  - benchmark: infrared_emittance_change
    label: Change in infrared emittance of CP-1 after combined UV, proton and electron exposure
    value: 8
    unit: percent
    scope: material
    conditions:
      exposure: combined UV, proton and electron irradiation (simulated L1/L2 environment)
      measurement: emittance measured in air, from about 0.47 to about 0.51 (decimal)
    method: Text summary by the paper. Its figure is an increase of about eight percent in the measured emittance
    status: ground
    source: russell2001
    where: Results section, paragraph beginning 'The thermal emittance values measured (in air) on the Kapton samples'
uses:
  - application: structures
    device: Solar sail made of 2 micrometre CP1 film with vapour-deposited aluminum
    example: A 20 square metre sail was deployed under high vacuum at the Plum Brook Station test chamber in 2005 and led to the Nanosail-D2 mission in 2011. MISSE flight samples of the same film were flown behind windows on MISSE-6B.
    source: ntrs2015
    where: Section 8 (2-um CP1 with VDA solar sail), page 21 of the memo
  - application: thermal-control
    device: Thin-film sunshade for a deployable space telescope
    example: The paper lists CP1 among thin-film candidates (12.5 micrometre films, vapour-deposited aluminum on one side) for a sunshade and solar sail in the Next Generation Space Telescope and Geomagnetic Storm Warning missions. It tested them for L1/L2 radiation and UV.
    source: russell2001
    where: Introduction, first two paragraphs and the film list
risks:
  hazards: []
  failure_risks:
    - mode: Atomic oxygen erosion
      trigger: Exposed CP1 film in low Earth orbit (MISSE 2 PEACE tray, 8.43e21 atoms/cm2)
      consequence: Film thins and erodes; the MISSE 2 erosion yield was 1.91e-24 cm3/atom
      severity: high
      source: banks2008
      where: Table I
    - mode: Seam failure under atomic oxygen
      trigger: 1 mil uncoated CP1 with an adhesive-free butt-joint seam in MISSE-2 (about 1.8e20 atoms/cm2)
      consequence: The butt joint failed while the film itself survived; a Kapton witness sample underneath showed the failure
      severity: moderate
      source: ntrs2015
      where: Section 3.1, figure 4 text
    - mode: Optical darkening under radiation and UV
      trigger: Simulated L1/L2 electron, proton and UV exposure
      consequence: Solar absorptance rose by more than 0.3 for the CP film group, and emittance rose by about eight percent for CP-1, with no sign of saturation
      severity: high
      source: russell2001
      where: Results section
  side_effects:
    - text: Erosion of an aluminized CP1 sample on MISSE-3 dropped its infrared emittance from 0.65 to 0.61 (the CP1 side was exposed).
      affects: Thermal emittance of the film surface
      source: ntrs2015
      where: Section 3.2, text on figure 8
  handling:
    - text: No handling or storage guidance for CP1 was found in a fetched source. No safety data sheet for CP1 was read.
      source: ntrs2015
      where: Not stated in the memo
  mitigations:
    - text: Aluminum coating on one side of the film (vapour-deposited aluminum) was flown and used in the 2 micrometre solar sail. The memo does not give an erosion yield for the coated film.
      source: ntrs2015
      where: Section 8 and section 3.2
    - text: A later modified grade, CORIN XLS, labelled as an AO-resistant CP1 and flown on MISSE-6A, had an atomic oxygen erosion yield of 8.4e-26 cm3/atom. It is not the same product as the original CP1 in this profile.
      source: ntrs2015
      where: Section 9 (CORIN XLS), page 22
supply:
  - subject: Colorless polyimide CP1 film
    abundance: Not read in a fetched source.
    producers:
      - name: NeXolve Corporation
        note: Formerly SRS Technologies and ManTech Corporation. Exclusively licensed the original polyimides from NASA Langley and modifies CP1 with proprietary additives and coatings.
        country: United States (NeXolve in Huntsville, Alabama, per the NASA memo title page)
      - name: SRS Technologies
        note: Manufacturer named for CP-1 and CP-2 in the 2001 test paper; the same company as NeXolve's former name.
        country: United States
    critical_lists: []
    recycling: Not sourced.
    substitutes:
      - EP2550 (now Essar Stretch 255) is a low-modulus analog of CP1, visibly clear and easily modified with fillers, per the NASA memo.
    source: ntrs2015
    where: Introduction (paragraph on NeXolve), section 3 (uncoated CP1 and CP1 variants) and the EP2550 description; manufacturer named in footnote 5 of AIAA-2001-1414 (russell2001)
corrosion:
  - environment: Atomic oxygen in low Earth orbit
    headline: Atomic oxygen erodes CP1 at about 1.91e-24 cm3 per atom, a little below Kapton HN.
    effect: On MISSE 2 the PEACE polymers tray received 8.43e21 atoms/cm2 over about 3.95 years. The uncoated 1 mil CP1 film with a butt-joint seam survived about 2e20 atoms/cm2 on the wake side, but its seam failed at about 1.8e20, and the Kapton witness below showed the failure.
    rating: severe
    conditions:
      flight_1: MISSE 2 PEACE tray, 3.95 years, fluence 8.43e21 atoms/cm2
      flight_2: MISSE-2 wake side, 1 mil butt-joint seam, seam failure at about 1.8e20 atoms/cm2
    source: banks2008
    where: Table I; the seam observation is from section 3.1 of ntrs2015
  - environment: Space ultraviolet, protons and electrons (ground simulation)
    headline: CP films darkened more than Kapton under simulated L1/L2 radiation, and their solar absorptance rose by more than 0.3 without saturating.
    effect: The paper says the solar absorptance of CP and TOR films rose by more than 0.3 without saturating, while Kapton and Upilex stayed within 0.1. The text gives the CP group only; the per-material CP-1 numbers are in figures that were not converted to values here.
    rating: severe
    conditions:
      exposure: simulated five-year L1/L2 proton, electron and about 1000 equivalent solar hours of UV
    source: russell2001
    where: Results section, paragraph on in situ solar absorptance changes
  - environment: Mechanical and thermal, as flown on MISSE
    headline: No corrosion, ageing or thermal-cycling endurance value for CP1 film was read in a fetched source.
    effect: The 2015 memo reports that uncoated CP1 showed no significant change in transmission on MISSE-1 and that its seam failed on MISSE-2. It gives no thermal-cycling or humidity result.
    rating: unknown
    conditions:
      basis: NASA memo section 3.1 (MISSE-1 and MISSE-2 uncoated CP1)
    source: ntrs2015
    where: Section 3.1, text on figure 3
story:
  recipe:
    line: Repeat unit C46H22O6N2F12, molar mass 926.6656 g/mole (Banks 2008, Table IV). It is a fluorinated aromatic polyimide, so it is made from a dianhydride and a diamine that form a poly(amic acid), which is then cyclised to the polyimide. The fetched Wikipedia page describes this two-step route for polyimides in general and does not name CP1's monomers, so the specific monomers are not listed here.
    parts:
      - name: Carbon
        symbol: C
        role: Carbon backbone of the aromatic rings and imide groups (NIST standard atomic weight interval).
      - name: Hydrogen
        symbol: H
        role: Hydrogen on the aromatic rings (NIST standard atomic weight interval).
      - name: Oxygen
        symbol: O
        role: Imide carbonyl and ether oxygens (NIST standard atomic weight interval).
      - name: Nitrogen
        symbol: 'N'
        role: Imide nitrogens (NIST standard atomic weight interval).
      - name: Fluorine
        symbol: F
        atoms: 12
        atomic_weight: 18.9984031636
        role: Fluorine groups that make the film colorless and clear (per the NASA memo's description of CP1 as visibly clear); the NASA table does not say which bonds carry them.
  supply_note: See supply section.
  risk_groups:
    - title: For people
      level: 1
      verdict: No hazard classification found in a fetched source
      lead: No safety data sheet for CP1 was read, so no hazard statement is recorded here.
      points:
        - label: Hazard data
          line: None found in a fetched source. The DuPont sheet for Kapton does not apply to CP1.
    - title: If it fails
      lead: These results come from flight exposure of uncoated film and from a laboratory simulation.
      points:
        - label: Atomic oxygen
          line: Erosion yield 1.91e-24 cm3/atom on MISSE 2, and the seam of a 1 mil sample failed at about 1.8e20 atoms/cm2.
        - label: Radiation darkening
          line: CP film solar absorptance rose by more than 0.3 in simulation.
    - title: Handling and storage
      points:
        - label: Storage
          line: No storage guidance found in a fetched source.
  why: CP1 is a colorless, fluorinated polyimide from NASA Langley. The NIST atomic weights and the NASA repeat-unit formula give a molar mass of 926.6656 g/mole. It was made for thin, clear film that can be used in space, and the flight data show that it survives on MISSE 2 but erodes and darkens under atomic oxygen and radiation. The erosion yield, 1.91e-24 cm3/atom, is lower than Kapton HN (2.81e-24) in the same NASA table.
  uses:
    - where: 2-micrometre solar sail (Plum Brook test, 2005; Nanosail-D2, 2011)
      line: A 20 square metre sail of 2 micrometre CP1 with vapour-deposited aluminum was deployed in vacuum. The memo says this led to the Nanosail-D2 mission.
    - where: Thin-film sunshade candidates
      line: CP1 is one of the thin-film candidates for a sunshade in the Next Generation Space Telescope, tested for L1/L2 radiation and UV.
  can_do:
    - label: Atomic oxygen
      value: 1.91e-24 cm3/atom
      line: On MISSE 2 the CP1 film eroded at 1.91e-24 cm3/atom, lower than Kapton HN at 2.81e-24.
    - label: Density
      value: 1.4193 g/cm3
      line: Density of the MISSE 2 CP1 sample in the NASA table.
    - label: Radiation
      value: More than 0.3 solar absorptance rise
      line: Simulated L1/L2 radiation and UV raised the solar absorptance of the CP film group by more than 0.3 without saturating.
    - label: Solar sail
      value: 20 square metres
      line: A 2 micrometre CP1 sail of 20 square metres was deployed in vacuum at GRC in 2005.
  compare: In the same MISSE 2 table, CP1 eroded at 1.91e-24 cm3/atom against 2.81e-24 for Kapton HN. Under simulated space radiation the CP films darkened by more than 0.3, while Kapton and Upilex stayed within 0.1 (russell2001). The fetched sources give no CP1 comparison with metals or composites.
  compare_rows:
    - scope: material
      label: Density
      benchmark: density
    - scope: material
      label: Atomic oxygen erosion yield
      benchmark: atomic_oxygen_erosion_yield
    - scope: material
      label: Solar absorptance rise under radiation
      benchmark: solar_absorptance_increase
  handling:
    - No handling or storage guidance for CP1 was found in a fetched source.
    - Keep the film out of atomic oxygen unless it is covered or coated, since the seam and the surface both erode.
  good_for:
    - Thin, clear, flexible film for solar sails and sunshades. The 2 micrometre sail deployed in vacuum on the ground.
    - Flight-proven film with a MISSE 2 erosion yield (1.91e-24 cm3/atom) lower than Kapton HN.
  watch_out:
    - Atomic oxygen erosion. The MISSE 2 erosion yield is 1.91e-24 cm3/atom, and the seam of a 1 mil sample failed at about 1.8e20 atoms/cm2.
    - Radiation darkening. The CP film group gained more than 0.3 solar absorptance in simulation, without saturating.
    - Commercial grades differ. NeXolve adds proprietary additives and coatings to CP1, so the values here may not match a current product.
  verdict: 'CP1 is a clear, thin, flexible polyimide that was flown on MISSE 2 and used in a 2 micrometre solar sail. It erodes under atomic oxygen (1.91e-24 cm3/atom) and darkens more than Kapton under simulated radiation, so exposed film needs a cover or coating. The record is thin: no CP1 thermal, mechanical or hazard data were read, and the gaps below list them.'
gaps:
  - No glass transition, CTE, tensile, thermal-cycling or moisture-absorption value for CP1 was read in a fetched source. A vendor datasheet (Thermalbright, hybridplastics.com) was not reachable in this run, so none is entered.
  - No safety data sheet, PubChem record or GHS classification for CP1 was found; the hazards list is empty.
  - The monomers of CP1 are not named in a fetched source; the recipe lists only the repeat unit and NIST atomic weights.
  - Supply abundance, country shares, critical-mineral lists and recycling were not read in a fetched source.
  - The MISSE 2 erosion value (1.91e-24) is for the PEACE polymers tray at the ISS fluence of 8.43e21 atoms/cm2 in Banks 2008. The 2015 NASA memo gives a wake-side MISSE-2 fluence of 1.7 to 2e20 atoms/cm2 for a separate 1 mil uncoated sample; the two exposures are not the same, and we have not reconciled them.
  - The CP film solar absorptance change is for the CP group (CP-1, CP-2, TOR), read from text. Per-material CP-1 values are in bar and line graphs in AIAA-2001-1414 and were not converted to numbers.
  - 'Non-canonical property names: atomic_oxygen_seam_failure_fluence, minimum_volume_of_atoms, infrared_emittance_change and solar_absorptance_increase are not in property-canon.yaml.'
  - Recipe monomers, process and imidisation conditions for CP1 are not in any fetched source. The Wikipedia page describes polyimides in general only.
documents:
  - title: 'NASA/TM-2008-215490: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit (Banks, Backus, de Groh)'
    type: report
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
  - title: 'AIAA-2001-1414: Effects of Electrons, Protons, and Ultraviolet Radiation on Thermophysical Properties of Polymeric Films (Russell et al.)'
    type: paper
    url: https://ntrs.nasa.gov/citations/20010072172
    year: 2001
  - title: 'NASA/TM-2015-218205: Analysis of Fluorinated Polyimides Flown on the Materials International Space Station Experiment (Finckenor, Rodman, Farmer)'
    type: report
    url: https://ntrs.nasa.gov/citations/20150016168
    year: 2015
  - title: Polyimide (Wikipedia)
    type: database
    url: https://en.wikipedia.org/wiki/Polyimide
    year: 2026
  - title: 'NIST Atomic Weights and Isotopic Compositions: carbon, hydrogen, nitrogen, oxygen, fluorine'
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
    year: 2026
license: CC-BY-4.0
updated: '2026-10-20'
review:
  status: draft
  method: assistant
  checked_values: 12
  unreachable: 1
  caveats: 4
  note: 'Written by an AI assistant on 2026-10-20. Values were read from text extracted from NASA/TM-2008-215490 (Banks 2008) and NASA/TM-2015-218205 (2015), from the text and tables of AIAA-2001-1414 (Russell 2001), and from the Wikipedia Polyimide page and NIST atomic weight pages, all fetched in this run. Caveats: the MISSE 2 fluence differs between the Banks report and the 2015 memo; the CP film solar absorptance values are group values read from text; no CP1 datasheet or safety sheet was reached; the monomers of CP1 are unnamed in the sources read.'
sources:
  banks2008:
    title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
    id: NASA/TM-2008-215490, NTRS 20090011780
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
    kind: report
    license: public domain (NASA)
  russell2001:
    title: 'AIAA-2001-1414: Effects of Electrons, Protons, and Ultraviolet Radiation on Thermophysical Properties of Polymeric Films'
    id: AIAA-2001-1414, NTRS 20010072172
    url: https://ntrs.nasa.gov/citations/20010072172
    year: 2001
    kind: paper
    license: public domain (NASA)
  ntrs2015:
    title: 'NASA/TM-2015-218205: Analysis of Fluorinated Polyimides Flown on the Materials International Space Station Experiment'
    id: NASA/TM-2015-218205, NTRS 20150016168
    url: https://ntrs.nasa.gov/citations/20150016168
    year: 2015
    kind: report
    license: public domain (NASA)
  wiki-polyimide:
    title: Polyimide (Wikipedia)
    id: en.wikipedia.org/wiki/Polyimide
    url: https://en.wikipedia.org/wiki/Polyimide
    year: 2026
    kind: web
    license: CC BY-SA
  nist-c:
    title: 'NIST Atomic Weights and Isotopic Compositions: carbon'
    id: 'NIST standard atomic weights, C (Z=6): 12.0096 to 12.0116'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&ascii=html
    year: 2026
    kind: database
    license: public domain (US government)
  nist-h:
    title: 'NIST Atomic Weights and Isotopic Compositions: hydrogen'
    id: 'NIST standard atomic weights, H (Z=1): 1.00784 to 1.00811'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&ascii=html
    year: 2026
    kind: database
    license: public domain (US government)
  nist-n:
    title: 'NIST Atomic Weights and Isotopic Compositions: nitrogen'
    id: 'NIST standard atomic weights, N (Z=7): 14.00643 to 14.00728'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=N&ascii=html
    year: 2026
    kind: database
    license: public domain (US government)
  nist-o:
    title: 'NIST Atomic Weights and Isotopic Compositions: oxygen'
    id: 'NIST standard atomic weights, O (Z=8): 15.99903 to 15.99977'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=O&ascii=html
    year: 2026
    kind: database
    license: public domain (US government)
  nist-f:
    title: 'NIST Atomic Weights and Isotopic Compositions: fluorine'
    id: 'NIST standard atomic weights, F (Z=9): 18.998403163(6)'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=F&ascii=html
    year: 2026
    kind: database
    license: public domain (US government)