spore: profile
id: peek
spore_version: 0.2
family: high-performance-polymers
name: Polyetheretherketone
abbreviation: PEEK
role: structural/insulating polymer
category: polymers
type: high-performance
summary: |
  PEEK is a stiff, heat-tolerant engineering thermoplastic. A Victrex datasheet gives a glass transition midpoint of 150 degC, melting at 343 degC and a tensile yield stress of 98.0 MPa. In low Earth orbit it erodes under atomic oxygen at about the rate of Kapton H (2.99e-24 against 3.00e-24 cm3/atom on the MISSE 2 flight), and film flown for 46 months on the ISS kept its stiffness and yield strength but only about 15% of its original elongation at break.
best_for: A stiff, heat-tolerant, low-outgassing structural and electrically insulating plastic (printed PEEK lost 0.19% of its mass in an outgassing test)
weakest_at: Ultraviolet and atomic-oxygen exposure in low Earth orbit (embrittled to about 15% of its original elongation on the ISS), and loss of strength between 77 K and 20 K
identity:
  formula: (-O-C6H4-O-C6H4-CO-C6H4-)n
  cas: 31694-16-3
  source: pubchem-peek
  where: Substance record SID 135076451 (synonym poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), CAS 31694-16-3); formula written out by Space Mushroom from that name; the Victrex safety data sheet section 1.2 lists CAS 31694-16-3 or 29658-26-2
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
    - uv
    - vacuum-and-outgassing
    - extreme-cold
    - total-radiation-dose
  applications:
    - structures
    - mechanisms
    - cryogenic-fuel
properties:
  - benchmark: density
    label: Density (crystalline), VICTREX PEEK 450G
    value: 1.3
    unit: g/cm3
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 1183
      state: crystalline
    method: Value listed in the manufacturer's online datasheet
    status: ground
    note: Datasheet values are nominal and depend on part geometry and processing. A 3D-printed part measured lower, 1.244 +/- 0.025 g/cm3 (outgassing specimen) and 1.221 +/- 0.036 g/cm3 (tensile specimen) in Rinaldi et al. Table 8.
    source: victrex-450g
    where: Material Properties > Physical (page last updated 17 March 2026)
  - benchmark: tensile_modulus
    label: Tensile modulus
    value: 4000
    unit: MPa
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 527-1
      temperature: 23 degC
    method: Value listed in the manufacturer's online datasheet
    status: ground
    note: Flexural modulus in the same table is 3800 MPa (ISO 178, 23 degC).
    source: victrex-450g
    where: Material Properties > Mechanical
  - benchmark: tensile_yield_stress
    label: Tensile yield stress
    value: 98
    unit: MPa
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 527-2
      temperature: 23 degC
    method: Value listed in the manufacturer's online datasheet
    status: ground
    note: Tensile strain at break on the same page is 25% (ISO 527-2, 23 degC).
    source: victrex-450g
    where: Material Properties > Mechanical
  - benchmark: glass_transition_temp
    label: Glass transition temperature (midpoint)
    value: 150
    unit: degC
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 11357-2
      point: midpoint
    method: Value listed in the manufacturer's online datasheet (differential scanning calorimetry)
    status: ground
    note: The onset of the glass transition on the same page is 143 degC. The unirradiated film in Nakamura and Fujita measured 142.3 degC by DSC (Table 3).
    source: victrex-450g
    where: Material Properties > Thermal
  - benchmark: melting_point
    label: Melting temperature
    value: 343
    unit: degC
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 11357-3
    method: Value listed in the manufacturer's online datasheet (differential scanning calorimetry)
    status: ground
    note: The Victrex safety data sheet also lists a melting point of 343 degC and a decomposition temperature above 450 degC.
    source: victrex-450g
    where: Material Properties > Thermal
  - benchmark: thermal_conductivity
    label: Thermal conductivity (average)
    value: 0.29
    unit: W/(m K)
    scope: material
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 22007-4
      temperature: 23 degC
      direction: average (0.32 along flow)
    method: Value listed in the manufacturer's online datasheet
    status: ground
    source: victrex-450g
    where: Material Properties > Thermal
  - benchmark: atomic_oxygen_erosion_yield
    value: 2.99e-24
    unit: cm3/atom
    scope: material
    conditions:
      experiment: MISSE 2 PEACE polymers, exterior of the International Space Station
      exposure: 3.95 yr in low Earth orbit, 16 August 2001 to 30 July 2005
      fluence: 8.43e21 atoms/cm2
      comparison: Kapton H polyimide measured 3.00e-24 cm3/atom in the same table
    method: Mass-loss erosion yield from the MISSE 2 flight samples, as compiled in the NASA report (the experiment is described in the report's references 11 and 12)
    status: flight
    note: Density used for PEEK in the report is 1.2259 g/cm3 and ash fraction 8.26e-3 (Table II). The report says some stacked thin-film samples eroded through, so some listed yields are lower bounds; PEEK is listed without a greater-than sign.
    source: banks2008
    where: Table I (MISSE 2 PEACE polymers erosion yield data); Section 2.1 for exposure; Table II for density
  - benchmark: outgassing_tml
    label: Total mass loss, 3D-printed PEEK (ECSS test)
    value: 0.19
    unit: '% mass'
    scope: material
    conditions:
      specimen: fused-filament-printed PEEK (APIUM filament, nozzle 410 degC)
      test_standard: ECSS-Q-ST-70-02C
      temperature: 125 degC for 24 h
      vacuum: below 1e-5 mbar
      collector: 25 degC
      samples: 3 (0.187, 0.186, 0.185)
    method: Thermal-vacuum outgassing test run by the paper's authors; the table value is the average of three samples
    status: ground
    note: The same table quotes the NASA outgassing database for PEEK 450 pellets as TML 0.3%, CVCM 0.02%, RML 0.12% (second-hand; we did not open the database entry). The printed material's tensile test (ASTM D638, XY orientation) gave 78.0 +/- 7.2 MPa strength and 2.9 +/- 0.3 GPa modulus, below the datasheet figures (Table 7).
    source: rinaldi2020
    where: Table 9 (outgassing results)
  - benchmark: outgassing_cvcm
    label: Collected volatile condensable material, 3D-printed PEEK (ECSS test)
    value: 0.01
    unit: '% mass'
    scope: material
    conditions:
      specimen: fused-filament-printed PEEK (APIUM filament, nozzle 410 degC)
      test_standard: ECSS-Q-ST-70-02C
      temperature: 125 degC for 24 h
      vacuum: below 1e-5 mbar
      collector: 25 degC
      samples: 3, each 0.01
    method: Thermal-vacuum outgassing test run by the paper's authors
    status: ground
    note: The limits listed in the paper are CVCM below 0.10% and recovered mass loss below 1.0%. The printed PEEK's recovered mass loss averaged 0.11%. Water vapour regained was not reported.
    source: rinaldi2020
    where: Table 9 (outgassing results)
  - benchmark: elongation_retained_leo
    label: Elongation at break retained after 46 months on the ISS
    value: 15
    unit: '% of pristine'
    scope: material
    conditions:
      specimen: extruded PEEK film 0.4 mm thick (FS-1100C, Sumitomo Bakelite), cut along the extrusion direction
      exposure: 46 months (1403 days) on the ISS Russian Service Module, mean altitude 371 km
      initial_tensile_load: 0, 1.6 or 4.7 MPa (results similar after 46 months)
      test: tensile, ASTM D882-95a, strain rate 0.1 /min, 23 degC and 50% relative humidity
    method: Tensile tests on flown samples compared with pristine film (the paper states 'about 15%')
    status: flight
    note: Elastic modulus and yield strength were unchanged. Pristine yield strength was about 85 MPa and pristine elongation about 200%. The paper estimates the real atomic-oxygen fluence was only 2 to 3e20 atoms/cm2, far less than predicted, and that a silicon-oxide contamination layer may have shielded the samples. Ground tests point to ultraviolet crosslinking as the main cause of embrittlement.
    source: nakamura2008
    where: Section 2.1; Section 3.3 (Fig. 10); Section 5.2; Section 6, conclusion (3)
  - benchmark: tensile_strength_cryogenic
    label: Ultimate tensile strength at 77 K
    value: 198.14
    unit: MPa
    scope: material
    conditions:
      temperature: 77 K
      crosshead_speed: 2 mm/min
      specimen: dumbbell cut from flat sheet by waterjet (ISO 37 Type I profile), PEEK grade not stated
      mean_of_repeats: standard deviation 1.33 MPa
    method: Tensile test in a cryogenic test rig
    status: ground
    uncertainty: standard deviation 1.33 MPa
    note: At the same speed the mean was 99.55 MPa at room temperature (Table 1) and 114.57 MPa at 20 K (Table 3), where strain at break was only 2.70%. In the same room-temperature test PTFE gave 18.15 MPa and UHMWPE 31.99 MPa; at 77 K they gave 86.22 and 129.77 MPa. Modulus was 5.32 GPa at 77 K. This is a preprint version.
    source: wang2024
    where: Table 2 (77 K); Tables 1 and 3 for notes
  - benchmark: gamma_dose_tested
    label: Highest gamma dose in a tensile and nano-indentation study
    value: 5
    unit: MGy
    scope: material
    conditions:
      source_of_radiation: cobalt-60 gamma irradiator, average dose rate 11.6 kGy/hr
      doses: 10 kGy, 100 kGy, 1 MGy and 5 MGy
      time_at_5_MGy: 17.9 days
      specimen: 25 mm x 25 mm PEEK sample, grade and form not stated
      tensile_test: ambient 28 to 30 degC, 3 subsamples per dose
    method: Raman, X-ray diffraction, nano-indentation and tensile tests before and after irradiation
    status: ground
    note: A dose tested, not a tolerance limit. The abstract says mechanical characteristics stay relatively unchanged up to 5 MGy, but the body reports a distinct reduction in strain at failure after 100 kGy, a surprising decline in tensile strength, and modulus and hardness that rose up to 1 MGy then levelled off. The authors say sample numbers were too few for statistics. Raman showed no change.
    source: cryer2025
    where: Section 4; Section 5.4 and Fig. 14 (tensile); Table 4; Section 6 and 7
corrosion:
  - environment: Atomic oxygen in low Earth orbit
    headline: Atomic oxygen eroded PEEK at about the same rate as Kapton H polyimide on the ISS.
    effect: On the MISSE 2 flight PEEK had an erosion yield of 2.99e-24 cm3/atom, against 3.00e-24 for Kapton H in the same table. Fluoropolymers were far lower, for example FEP at 2.00e-25 and PTFE at 1.42e-25. On the ISS Russian Service Module, PEEK film lost only 9.2 micrometres of thickness in 46 months and the surface developed a cone-like pattern typical of atomic-oxygen attack.
    rating: moderate
    conditions:
      flight: MISSE 2, 3.95 yr, fluence 8.43e21 atoms/cm2
      second_flight: MPAC&SEED, 0.4 mm film, 46 months, thickness loss 9.2 micrometres with no applied load
    source: banks2008
    where: Table I; Nakamura and Fujita Section 3.2 and Section 5.2
  - environment: Space ultraviolet light and charged particles (ISS exterior)
    headline: Film turned brown and lost most of its stretch after 46 months, but kept its stiffness and yield strength.
    effect: Flown PEEK film browned with exposure time and its elongation at break fell to about 15% of pristine after 46 months; elastic modulus and yield strength were unchanged. Ground tests found the electron beam hardly changed tensile properties and ultraviolet light caused the same trend, so the authors attribute the embrittlement mainly to ultraviolet-induced crosslinking. Samples were also covered by a silicon-oxide contamination layer.
    rating: moderate
    conditions:
      exposure: 46 months (1403 days), ISS Russian Service Module, 371 km mean altitude
      film: 0.4 mm FS-1100C
    source: nakamura2008
    where: Sections 3.1, 3.3, 5.1, 5.2 and 6
  - environment: Concentrated sulphuric acid
    headline: The supplier lists concentrated sulphuric acid as the one incompatible material but gives no rate.
    effect: The Victrex safety data sheet gives concentrated sulphuric acid as the incompatible material and lists 'none known' for storage incompatibilities. It reports PEEK as insoluble in water and other solvents. It gives no corrosion rate or test, and we did not open a quantitative chemical-resistance table.
    rating: unknown
    conditions:
      basis: supplier safety data sheet, covers PEEK granules including 450G
      revision: 20 May 2022
    source: victrex-sds
    where: Section 10.5; Sections 7.2 and 9.1
  - environment: Water, 23 degC and 100 degC
    headline: PEEK takes up only a little water, under 1% by mass even in boiling water.
    effect: Saturation water absorption of PEEK 450G is 0.45% at 23 degC and 0.55% at 100 degC.
    rating: low
    conditions:
      grade: VICTREX PEEK 450G
      test_standard: ISO 62
      state: saturation
    source: victrex-450g
    where: Material Properties > Physical
risks:
  hazards:
    - text: 'Victrex safety data sheet (issue 1, 20 May 2022, covering PEEK granules including 450G): not classified as dangerous under the EU CLP regulation, no pictograms, signal word or hazard statements. Inhaled dust gives mechanical irritation of the respiratory tract; repeated skin contact may cause irritation; dust may irritate the eyes. Many toxicology fields read ''Not known''.'
      ghs: []
      source: victrex-sds
      where: Sections 2 and 11
    - text: Molten polymer sticks to skin and causes severe thermal burns. Dust is ignitable but will not sustain combustion; the sheet warns of explosive dust clouds and gives a minimum ignition spark energy above 5000 mJ and an auto-ignition point of 595 degC.
      ghs: []
      source: victrex-sds
      where: Sections 5.3, 7.1, 9.1 and 11
  failure_risks:
    - mode: Embrittlement in low Earth orbit
      trigger: 46 months on the ISS Russian Service Module (ultraviolet, atomic oxygen, particles)
      consequence: Elongation at break fell to about 15% of pristine, while modulus and yield strength were unchanged, so a part that should stretch before breaking becomes brittle.
      severity: moderate
      source: nakamura2008
      where: Section 3.3 and Section 6
    - mode: Strength loss at hydrogen temperature
      trigger: Cooling from 77 K to 20 K
      consequence: At 2 mm/min ultimate tensile strength fell from 198.14 MPa at 77 K to 114.57 MPa at 20 K, and strain at break from 8.09% to 2.70%.
      severity: moderate
      source: wang2024
      where: Tables 2 and 3
    - mode: Loss of ductility under gamma radiation
      trigger: Cobalt-60 gamma doses of 100 kGy and above
      consequence: A distinct reduction in strain at failure after 100 kGy, with the 5 MGy samples significantly less ductile than unirradiated ones, from three subsamples per dose.
      severity: moderate
      source: cryer2025
      where: Section 5.4 and Fig. 14
  side_effects:
    - text: Flown film was covered with a pale silicon-and-oxygen contamination layer over about 70 to 80% of the exposed area; the authors suggest it shielded the samples from atomic oxygen and ultraviolet light, so the real exposure was much lower than predicted.
      affects: Interpretation of the flight result
      source: nakamura2008
      where: Section 3.1 and Section 5.2
    - text: Gamma irradiation discoloured the PEEK samples in step with dose.
      affects: Appearance (a possible passive dose indicator, according to the authors)
      source: cryer2025
      where: Section 5 and Section 6
  handling:
    - text: Store enclosed in the original packing at room temperature; storage life more than 10 years. Avoid build-up of dust, use local exhaust ventilation, and take precautions against static discharge. Purging a machine with other polymers at high temperature can be hazardous.
      source: victrex-sds
      where: Sections 6.1, 7.1 and 7.2
    - text: Decomposes above 450 degC and gives off oxides of carbon in a fire. Do not use concentrated sulphuric acid with it.
      source: victrex-sds
      where: Sections 5.2, 9.1 and 10
  mitigations:
    - text: Wear eye protection with side shields, insulating heat gloves when handling heated material, and a fine-dust breathing mask if exposure limits may be exceeded. The sheet lists general dust limits of 10 mg/m3 inhalable and 4 mg/m3 respirable.
      source: victrex-sds
      where: Section 8
uses:
  - application: structures
    device: 3D-printed PEEK structure for a 2U CubeSat-class nanosatellite for low Earth orbit (design and ground tests only in the paper)
    example: A fused-filament-printed PEEK structure, 10 x 10 x 21 cm, was designed with topology optimisation for mass savings; the paper's space-relevant test is the outgassing measurement above.
    source: rinaldi2020
    where: Abstract; Section 1 and Table 9
  - application: structures
    device: PEEK film samples on the exterior of the ISS Russian Service Module (flight exposure experiment)
    example: JAXA's MPAC&SEED experiment exposed 0.4 mm PEEK film under tensile load from October 2001 to August 2005 as a candidate for deployable structures such as large antennas, solar arrays and sails.
    source: nakamura2008
    where: Section 1 and Section 2.1
  - application: cryogenic-fuel
    device: Candidate seal or liner material for liquid-hydrogen systems (ground tensile tests only)
    example: Tensile and thermal-contraction tests at room temperature, 77 K and 20 K were run to judge thermoplastics as alternatives to metal seals in cryogenic fuel systems.
    source: wang2024
    where: Abstract and Section 1
  - application: mechanisms
    device: Robot components for fusion maintenance in high-gamma environments (ground irradiation tests only)
    example: UKAEA irradiated PEEK to 5 MGy gamma as a candidate structural polymer for remote-handling robots.
    source: cryer2025
    where: Abstract and Section 3
supply:
  - subject: PEEK polymer (resin)
    producers: []
    source: victrex-what-is-peek
    where: "Victrex product page presents Victrex as a maker of PEEK polymers. Wikipedia PEEK page says the PEEK division of ICI was acquired through a management buyout, giving rise to Victrex PLC. Solvay (KetaSpire) and Evonik (VESTAKEEP) were named in the brief but could not be read in this run: the Solvay page returned an access error and the Evonik page had no product text. No country shares were found."
documents:
  - title: VICTREX PEEK 450G datasheet (manufacturer web page)
    type: datasheet
    url: https://www.victrex.com/en/downloads/datasheets/victrex-peek-450g
    year: 2026
  - title: 'Victrex safety data sheet: PEEK powders and granules (VIML-MSDS-011, 20 May 2022)'
    type: sds
    url: https://www.boedeker.com/Portals/0/Safety%20Data%20Sheets%20SDS/Victrex/PEEK_MSDS_Powder_Granules_English_May2022.pdf
    year: 2022
  - title: 'NASA/TM-2008-215490: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit'
    type: report
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
  - title: Effects of LEO Environment on Mechanical Properties of PEEK Films under Tensile Stress (JAXA-SP-08-015E)
    type: paper
    url: https://jaxa.repo.nii.ac.jp/record/5226/files/64307010.pdf
    year: 2008
  - title: 'Additive Manufacturing of PEEK for Space Applications: A Nanosat Polymeric Structure (open access)'
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7792942/
    year: 2020
  - title: Evaluating the potential of thermoplastic polymers for cryogenic sealing applications (arXiv preprint)
    type: paper
    url: https://arxiv.org/abs/2406.01165
    year: 2024
  - title: Radiation impact on robot-relevant polymers for high gamma environments (UKAEA preprint)
    type: paper
    url: https://scientific-publications.ukaea.uk/wp-content/uploads/UKAEA-CCFE-PR25317.PDF
    year: 2025
gaps:
  - "No country shares for PEEK producers: only the Victrex page was readable (Solvay returned an access error and Evonik had no product text), and no USGS or similar source for PEEK feedstock was read."
  - "Monomer formulas for hydroquinone and 4,4'-difluorobenzophenone were not read on a fetched page, so monomer atoms are not entered; the recipe uses the repeat unit only."
  - No PubChem compound record with GHS data was found for PEEK; PubChem has only a substance record (ChemIDplus) with no GHS information, so hazard data rest on one Victrex safety data sheet.
  - The NASA outgassing database entries for PEEK could not be searched here (the database is an interactive page); the NASA figure appears only second-hand in Rinaldi et al. Table 9, and the ASTM E595 result for the grade was not read from NASA.
  - Several other datasheet values on the Victrex page (deflection temperature under load, expansion coefficients, electrical properties, flammability) were not entered to keep this profile light.
  - Thermal expansion at cryogenic temperatures (about 0.9% contraction at 20 K, Wang et al. Fig. 8 and Table 4) was read but not entered as a property.
  - No quantitative chemical-resistance table was opened; the corrosion section rests on the safety data sheet and the datasheet water-absorption figures.
  - The PEEK grade and sample form are not stated in the cryogenic preprint or the gamma-irradiation preprint, so those values cannot be tied to a datasheet grade.
  - No thermal-cycling, vacuum-friction or proton-irradiation result for PEEK was entered.
sources:
  wiki-peek:
    title: Polyether ether ketone (Wikipedia)
    id: Wikipedia article, accessed 2026-10-19; infobox molar mass, synthesis and manufacturer sections
    url: https://en.wikipedia.org/wiki/Polyether_ether_ketone
    year: 2026
    kind: web
    license: CC BY-SA 4.0
  victrex-what-is-peek:
    title: What is Poly-ether-ether-ketone (PEEK) polymer? (Victrex)
    id: Victrex web page, accessed 2026-10-19
    url: https://www.victrex.com/en/what-is-peek
    year: 2026
    kind: web
    license: manufacturer web page, linked not reproduced
  nist-atomic-weights:
    title: Atomic Weights and Isotopic Compositions for All Elements (NIST)
    id: NIST composition tables, accessed 2026-10-19
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&all=all&ascii=html
    year: 2026
    kind: database
    license: public domain (NIST)
  victrex-450g:
    title: VICTREX PEEK Polymer 450G - Datasheet (Victrex plc)
    id: Victrex online datasheet, last updated 17 March 2026
    url: https://www.victrex.com/en/downloads/datasheets/victrex-peek-450g
    year: 2026
    kind: datasheet
    license: manufacturer document, linked not reproduced
  victrex-sds:
    title: 'Safety Data Sheet: VICTREX PEEK Powder and Granules (including 450G)'
    id: VIML-MSDS-011, issue 1 rev 1, 20 May 2022
    url: https://www.boedeker.com/Portals/0/Safety%20Data%20Sheets%20SDS/Victrex/PEEK_MSDS_Powder_Granules_English_May2022.pdf
    year: 2022
    kind: datasheet
    license: manufacturer document, linked not reproduced
  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)
  nakamura2008:
    title: Effects of LEO Environment on Mechanical Properties of PEEK Films under Tensile Stress
    id: JAXA-SP-08-015E, MPAC&SEED symposium, Tsukuba, 10-11 March 2008
    url: https://jaxa.repo.nii.ac.jp/record/5226/files/64307010.pdf
    year: 2008
    kind: paper
    license: JAXA repository document, linked not reproduced
  rinaldi2020:
    title: 'Additive Manufacturing of Polyether Ether Ketone (PEEK) for Space Applications: A Nanosat Polymeric Structure'
    id: doi:10.3390/polym13010011 (Polymers 13, 11, PMC7792942)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7792942/
    year: 2020
    kind: paper
    license: CC BY 4.0
  wang2024:
    title: 'Evaluating the potential of thermoplastic polymers for cryogenic sealing applications: strain rate and temperature effects'
    id: arXiv:2406.01165 (pre-final version)
    url: https://arxiv.org/abs/2406.01165
    year: 2024
    kind: paper
    license: CC BY-NC-ND 4.0
  cryer2025:
    title: Radiation impact on robot-relevant polymers for high gamma environments
    id: UKAEA-CCFE-PR(25)317, preprint submitted to Radiation Physics and Chemistry
    url: https://scientific-publications.ukaea.uk/wp-content/uploads/UKAEA-CCFE-PR25317.PDF
    year: 2025
    kind: paper
    license: UKAEA preprint; the acknowledgements state a CC BY licence is applied to the accepted manuscript where permitted
  pubchem-peek:
    title: PubChem substance record, Polyetheretherketone (SID 135076451, source ChemIDplus)
    id: SID 135076451; CAS 31694-16-3
    url: https://pubchem.ncbi.nlm.nih.gov/substance/135076451
    year: 2026
    kind: database
    license: public domain (NCBI)
license: CC-BY-4.0
updated: '2026-10-17'
review:
  status: draft
  method: assistant
  checked_values: 4
  unreachable: 2
  caveats: 5
  note: Written by an AI assistant on 2026-10-17. 4 values (MISSE 2 erosion yield, ISS elongation, 77 K strength, 5 MGy gamma) were read directly in text extracted from the source PDF. The other 8 were read once through a web-page summary and not independently re-read. 2 sources could not be used (the NASA outgassing database search page and a Sigma-Aldrich product listing timed out). 5 values carry caveats noted in the file. No values were taken from memory.
story:
  recipe:
    line: "PEEK is made by step-growth polymerization. The disodium salt of hydroquinone, generated in situ by deprotonation with sodium carbonate, reacts with 4,4'-difluorobenzophenone by dialkylation of the bisphenolate salts (Wikipedia). The repeat unit is C19H12O3 (Wikipedia infobox formula)."
    parts:
      - {name: Carbon, symbol: C, atoms: 19, atomic_weight: 12.011, role: "Three benzene rings and the ketone carbon of each repeat unit."}
      - {name: Hydrogen, symbol: H, atoms: 12, atomic_weight: 1.008, role: "Four hydrogens on each of the three phenylene rings."}
      - {name: Oxygen, symbol: O, atoms: 3, atomic_weight: 15.999, role: "Two ether oxygens and one ketone oxygen per repeat unit."}
  risk_groups:
    - title: For people
      level: 1
      verdict: Not classified; hot PEEK burns
      lead: The supplier does not classify PEEK granules as hazardous, but toxicology data are mostly listed as unknown, and heated PEEK can burn skin badly.
      points:
        - label: The solid and its dust
          line: The Victrex safety data sheet (20 May 2022) says the granules are not classified as dangerous and carry no hazard label. Dust gives mechanical irritation of the respiratory tract and may irritate the eyes, and many toxicology entries read 'Not known'.
        - label: Molten polymer
          line: Molten PEEK sticks to skin and causes severe burns. The sheet advises cooling the area with water, not removing hardened product, and getting medical attention. Insulating gloves are advised when handling heated material.
        - label: Dust and fire
          line: Dust is ignitable but does not sustain combustion, and the sheet warns that dust clouds can be explosive. It gives a minimum ignition spark energy above 5000 mJ and an auto-ignition point of 595 °C. Burning gives off oxides of carbon, and the polymer decomposes above 450 °C.
    - title: If it fails
      lead: These results are from flight exposure and laboratory tests on films and sheets, not from failures of finished spacecraft parts.
      points:
        - label: In orbit
          line: PEEK film flown for 46 months on the ISS Russian Service Module kept its modulus and yield strength but retained only about 15% of its elongation at break, so it became brittle. Ground tests point to ultraviolet crosslinking as the main cause.
        - label: At hydrogen temperature
          line: In tensile tests at 2 mm/min, strength rose to 198.14 MPa at 77 K but fell to 114.57 MPa at 20 K, and strain at break dropped from 8.09% to 2.70%.
        - label: Under gamma radiation
          line: In a cobalt-60 study to 5 MGy, PEEK showed a distinct reduction in strain at failure after 100 kGy. The authors had expected little change and note that only three subsamples were tested per dose.
    - title: Handling and storage
      points:
        - label: Storage
          line: Keep the granules enclosed in their original packing at room temperature. The supplier gives a storage life of more than 10 years and lists no incompatible material for storage.
        - label: Dust control
          line: Avoid build-up of dust, use local exhaust ventilation and guard against static discharge. A fine-dust breathing mask is advised if exposure limits may be exceeded.
        - label: Chemicals
          line: The sheet names concentrated sulphuric acid as the incompatible material. Purging a machine with another polymer at high temperature can also be hazardous.
  why: Polyetheretherketone (PEEK) is a thermoplastic, a polymer that softens when heated and can be melted and reshaped. Each repeat unit of its chain joins three benzene rings (phenylene groups) through two ether links (a carbon-oxygen-carbon bridge) and one ketone group (a carbon double-bonded to oxygen), which is where the name comes from. The rings make the chain stiff, so PEEK keeps its stiffness to high temperature. Two temperatures mark the limits. The glass transition temperature, where the disordered regions of the plastic change from glassy to rubbery, is 150 °C (midpoint) for the Victrex 450G grade, and the crystalline regions melt at 343 °C. PEEK is also electrically insulating and absorbs little water. Those properties explain why it is considered for structures and mechanisms that must stay stiff when hot, but the record collected here also shows that space ultraviolet light and atomic oxygen degrade it, so it is not a drop-in material for every orbit.
  uses:
    - where: Printed nanosatellite structure
      line: A paper designed a fused-filament-printed PEEK structure for a 2U CubeSat-class nanosatellite, 10 x 10 x 21 cm, for low Earth orbit. The paper reports design work and ground tests, and the space-relevant test is the outgassing measurement described below.
    - where: Flown on the ISS as film
      line: JAXA exposed 0.4 mm PEEK film under tensile load on the exterior of the ISS Russian Service Module from October 2001 to August 2005, as a candidate for deployable structures such as large antennas, solar arrays and sails.
    - where: Tested on the ground for hydrogen systems
      line: Researchers tested PEEK in tension at room temperature, 77 K and 20 K to judge thermoplastics as alternatives to metal seals in cryogenic fuel systems. These were laboratory tests, not a seal in service.
    - where: Tested on the ground for robots in radiation
      line: UKAEA irradiated PEEK to 5 MGy of gamma radiation as a candidate structural polymer for remote-handling robots in fusion maintenance. This was a laboratory irradiation, not a deployment.
  can_do:
    - label: Strength and stiffness
      value: 98.0 MPa
      line: The Victrex datasheet gives a tensile yield stress of 98.0 MPa and a tensile modulus of 4000 MPa for the 450G grade, tested to ISO 527 at 23 °C. These are nominal values; a printed PEEK part in another study measured 78.0 MPa and 2.9 GPa.
    - label: Heat
      value: Melts at 343 °C
      line: The datasheet gives a glass transition midpoint of 150 °C and a melting temperature of 343 °C for the 450G grade. Above the glass transition the plastic is much less stiff, so useful loads are carried well below the melting point.
    - label: Low temperature
      value: 198.14 MPa at 77 K
      line: In tensile tests at 2 mm/min the ultimate tensile strength was 99.55 MPa at room temperature, 198.14 MPa at 77 K and 114.57 MPa at 20 K. The grade of PEEK was not stated in the preprint.
    - label: In orbit
      value: Kept about 15% of its stretch
      line: After 46 months on the ISS, PEEK film kept its modulus and yield strength but only about 15% of its original elongation at break. Its atomic-oxygen erosion yield on the MISSE 2 flight was 2.99 × 10⁻²⁴ cm³/atom over 3.95 years at a fluence of 8.43e21 atoms/cm².
    - label: Outgassing
      value: 0.19% mass loss
      line: Outgassing is the release of trapped gases and volatile compounds in vacuum, which can then condense on optics and sensors. A 3D-printed PEEK specimen heated at 125 °C for 24 hours in vacuum under the ECSS-Q-ST-70-02C method lost 0.19% of its mass (total mass loss, TML) and condensed 0.01% of its mass on a collector (CVCM).
  compare: In a room-temperature tension test at 2 mm/min, PEEK reached 99.55 MPa, against 18.15 MPa for PTFE and 31.99 MPa for UHMWPE (ultra-high-molecular-weight polyethylene). At 77 K the same polymers reached 198.14, 86.22 and 129.77 MPa. In low Earth orbit, PEEK eroded at 2.99 × 10⁻²⁴ cm³/atom, almost the same as the 3.00 × 10⁻²⁴ measured for Kapton H polyimide in the same flight table, while fluoropolymers such as FEP (2.00 × 10⁻²⁵) and PTFE (1.42 × 10⁻²⁵) eroded far less. No source in this record compares PEEK with metals or composites, so no such comparison is made.
  handling:
    - Granules are not classified as hazardous by the supplier; keep them enclosed at room temperature.
    - Avoid dust build-up and use local exhaust ventilation; dust clouds can be explosive.
    - Molten PEEK sticks to skin and burns it severely, so use insulating gloves when it is hot.
    - Concentrated sulphuric acid is the incompatible material named by the supplier.
  good_for:
    - Stiffness at temperature. The 450G datasheet gives a tensile modulus of 4000 MPa at 23 °C and a glass transition midpoint of 150 °C.
    - Low outgassing. A printed PEEK specimen lost 0.19% of its mass and condensed 0.01% in a 125 °C vacuum test.
    - Cryogenic strength. Tensile strength reached 198.14 MPa at 77 K, higher than PTFE or UHMWPE in the same test.
  watch_out:
    - Ultraviolet and atomic oxygen. Film on the ISS kept only about 15% of its elongation at break after 46 months, and its atomic-oxygen erosion yield was about equal to Kapton H.
    - Very cold temperatures. Strength fell from 198.14 MPa at 77 K to 114.57 MPa at 20 K.
    - Gamma radiation. Strain at failure fell distinctly after 100 kGy in a study up to 5 MGy, though sample numbers were small.
    - Process matters. Printed PEEK was weaker than the datasheet values (78.0 MPa against 98.0 MPa), and datasheet figures are nominal.
  verdict: PEEK is a stiff, heat-tolerant, low-outgassing plastic with flight exposure data on the ISS, but that data shows ultraviolet embrittlement and atomic-oxygen erosion like Kapton H. It suits parts that are shielded from the orbital surface environment, and every use above is a ground test or proof of concept except the two flight exposures.
  compare_rows:
    - label: Density
      benchmark: density
      scope: material
    - label: Melting point
      benchmark: melting_point
      scope: material
    - label: Thermal conductivity
      benchmark: thermal_conductivity
      scope: material