spore: profile
id: pi-kapton-hpp-st
spore_version: 0.2
family: polyimides
name: Kapton HPP-ST polyimide film
abbreviation: PI (Kapton HPP-ST)
role: surface-treated all-polyimide film for flexible circuits, PCB stencils and laminates
category: polymers
type: polyimides
summary: Kapton HPP-ST is a surface-treated all-polyimide film sold by Qnity Electronics, a DuPont spinoff that makes Kapton. For the 100HPP-ST grade (25.4 µm, 1 mil), the manufacturer prints a tensile strength of 231.0 MPa and an elongation at break of 72 % at 23 °C. The 25.4 µm film has a dielectric strength of 303 kV/mm and a dielectric constant of 3.40 at 1 kHz, and the specification caps shrinkage at 0.10 % after 1 hour at 200 °C.
best_for: Flexible printed circuit and PCB stencil films where adhesion treatment and a 231.0 MPa tensile strength at 23 °C matter, in the 100HPP-ST grade (25.4 µm)
weakest_at: 'Heat rating under load: the sources give a UL 746B relative thermal index of 240 °C (electrical) and 200 °C (mechanical), which are ratings and not service limits, and no HPP-ST value for in-orbit erosion was read'
identity:
  formula: C22H10O5N2 repeat unit, poly(4,4'-oxydiphenylene-pyromellitimide), made from pyromellitic dianhydride and 4,4'-oxydianiline; the manufacturer calls HPP-ST an all-polyimide film with the properties of Type HN
  source: nasa-tm-2008-215490
  where: Table of polymer erosion data, row Polyimide (PMDA) PI (Kapton H), formula column C22H10O5N2; Wikipedia Kapton article gives the chemical name for Kapton K and HN
  designations:
    - system: Trade name
      code: Kapton® HPP-ST
      source: qnity-kapton-spec
      where: Introduction page, heading Kapton® HPP-ST polyimide film
tags:
  applications:
    - electronics-and-chips
    - solar-arrays
    - thermal-control
properties:
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 23 °C, Kapton 100HPP-ST
    value: 231
    unit: MPa
    scope: material
    conditions:
      grade: Kapton HPP-ST, 100HPP-ST, 25.4 µm (1 mil) film
      temperature: 23 °C
    method: Typical value printed on the manufacturer product page. The summary PDF prints the same 231 MPa for 25 µm HPP-ST by ASTM D-882.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Tensile Strength @23°C (MPa)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength minimum, 25.4 µm (1.00 mil) film, MD and TD
    value: 165
    unit: MPa
    scope: material
    conditions:
      grade: Kapton HN and HPP-ST, 1.00 mil (25.4 µm) film
      temperature: 23 °C
      direction: MD and TD, minimum
    method: Specification minimum (min.) for 25.4 µm film; the table footnote says it also applies to HPP-ST. ASTM D-882-91 Method A.
    status: ground
    source: qnity-kapton-spec
    where: Table 2, Mechanical Properties of Kapton HN polyimide film, row Tensile Strength psi (MPa) at 23°C min., column 1.00 (25.4)
  - benchmark: elongation
    label: Elongation at break at 23 °C, Kapton 100HPP-ST
    value: 72
    unit: '%'
    scope: material
    conditions:
      grade: Kapton 100HPP-ST, 25.4 µm film
      temperature: 23 °C
    method: Typical value printed on the manufacturer product page. The summary PDF prints 72 % for 25 µm HPP-ST by ASTM D-882.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Elongation % to Break @23°C
  - benchmark: elastic_modulus
    label: Tensile modulus at 23 °C, Kapton 100HPP-ST
    value: 2.8
    unit: GPa
    scope: material
    conditions:
      grade: Kapton 100HPP-ST, 25.4 µm film
      temperature: 23 °C
    method: Typical value printed on the manufacturer product page; no test standard is printed against this column in the text read
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Tensile Modulus @23°C (GPa)
  - benchmark: density
    label: Density, Kapton HPP-ST 25 µm film
    value: 1.42
    unit: g/cc
    scope: material
    conditions:
      grade: Kapton HPP-ST, 25 µm (1 mil) film
    method: Typical value by ASTM D-1505, as printed in the summary PDF; the product page prints the same 1.42 g/cc for 100HPP-ST
    status: ground
    source: qnity-kapton-summary
    where: Table 3, Physical and Thermal Properties of Kapton Type HPP-ST Film, row Density g/cc or g/mL, 25 µm column
  - benchmark: dielectric_strength
    label: Dielectric strength, Kapton 100HPP-ST
    value: 303
    unit: kV/mm
    scope: material
    conditions:
      grade: Kapton 100HPP-ST, 25.4 µm film
      test: 60 Hz, 1/4 in electrodes, 500 V/sec rise
    method: Typical value printed on the manufacturer product page. The summary PDF Table 7 prints 303 kV/mm for 25 µm HN and HPP-ST by ASTM D-149.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Dielectric Strength (kV/mm)
  - benchmark: dielectric_strength
    label: Dielectric strength minimum, 25.4 µm (1.00 mil) film
    value: 236
    unit: kV/mm
    scope: material
    conditions:
      grade: Kapton HN and HPP-ST, 1.00 mil (25.4 µm) film
      test: ASTM D-149-97, AC, flat sheets between 1/4 in brass electrodes
    method: Specification minimum (min.) for 25.4 µm film; the table footnote says it also applies to HPP-ST
    status: ground
    source: qnity-kapton-spec
    where: Table 3, Electrical Properties of Kapton HN polyimide film, row Dielectric Strength AC V/mil (kV/mm) min., column 1.00 (25.4)
  - benchmark: dielectric_constant
    label: Dielectric constant at 1 kHz, Kapton 100HPP-ST
    value: 3.4
    unit: '-'
    scope: material
    conditions:
      grade: Kapton 100HPP-ST, 25.4 µm film
      frequency: 1 kHz
    method: Typical value printed on the manufacturer product page. The summary PDF Table 7 prints 3.4 at 1 kHz for 25 µm HN and HPP-ST by ASTM D-150.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Dielectric Constant @ 1 kHz
  - benchmark: dissipation_factor
    label: Dissipation factor at 1 kHz, 25 µm film
    value: 0.0018
    unit: '-'
    scope: material
    conditions:
      grade: Kapton HN and HPP-ST, 25 µm (1 mil) film
      frequency: 1 kHz
    method: Typical value by ASTM D-150, as printed in the summary PDF
    status: ground
    source: qnity-kapton-summary
    where: Table 7, Typical Electrical Properties of Kapton Type HN and HPP-ST Films, Dissipation Factor, 25 µm (1 mil) row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Kapton 100HPP-ST
    value: 0.12
    unit: W/mK
    scope: material
    conditions:
      grade: Kapton 100HPP-ST, 25.4 µm film
    method: Typical value printed on the manufacturer product page. The page text read does not map a test standard to this column. A different value for Type 100 HN is in the summary PDF (see gaps).
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties table, row Kapton 100HPP-ST, Thermal Conductivity (W/mK)
  - benchmark: limiting_oxygen_index
    label: Limiting oxygen index, 25 µm HPP-ST film
    value: 37
    unit: '%'
    scope: material
    conditions:
      grade: Kapton HPP-ST, 25 µm (1 mil) film
    method: Typical value by ASTM D-2863, as printed in the summary PDF. Not a canonical name in property-canon, so the custom name limiting_oxygen_index is used.
    status: ground
    source: qnity-kapton-summary
    where: Table 3, Physical and Thermal Properties of Kapton Type HPP-ST Film, Limiting Oxygen Index % row, 25 µm column
  - benchmark: thermal_shrinkage
    label: Shrinkage after 30 min at 150 °C, 25 µm HPP-ST film
    value: 0.03
    unit: '%'
    scope: material
    conditions:
      grade: Kapton HPP-ST, 25 µm (1 mil) film
      temperature: 150 °C
      time: 30 min
    method: Typical value by IPC TM 650 Method 2.2.4A, as printed in the summary PDF
    status: ground
    source: qnity-kapton-summary
    where: Table 3, Physical and Thermal Properties of Kapton Type HPP-ST Film, Shrinkage % 30 min at 150°C row, 25 µm column
  - benchmark: thermal_shrinkage
    label: Shrinkage maximum at 200 °C for 1 h, 25.4 µm HPP-ST film, MD and TD
    value: 0.1
    unit: '%'
    scope: material
    conditions:
      grade: Kapton HPP-ST, 1.00 mil (25.4 µm) film
      temperature: 200 °C
      time: 1 hr
      direction: MD and TD, maximum
    method: Specification maximum (max.) for HPP-ST, as printed in the Table 5 shrinkage test method
    status: ground
    source: qnity-kapton-spec
    where: Table 5, Shrinkage of Kapton HPP-ST polyimide film, row Shrinkage %, MD and TD at 200°C (392°F) max., column 1.00 (25.4)
  - benchmark: relative_thermal_index
    label: UL electrical relative thermal index, Kapton HPP-ST
    value: 240
    unit: °C
    scope: material
    conditions:
      grade: Kapton HPP-ST
      standard: UL 746B, electrical
    method: Rating printed on the manufacturer product page under Electrical, UL Electrical RTI. A rating, not a continuous service limit.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties classification block, Electrical group, UL Electrical RTI (°C) row
  - benchmark: relative_thermal_index
    label: UL mechanical relative thermal index, Kapton HPP-ST
    value: 200
    unit: °C
    scope: material
    conditions:
      grade: Kapton HPP-ST
      standard: UL 746B, mechanical strength
    method: Rating printed on the manufacturer product page under Mechanical, UL Mechanical Strength RTI. A rating, not a continuous service limit.
    status: ground
    source: qnity-hpp-st-page
    where: Kapton HPP-ST Product Properties classification block, Mechanical group, UL Mechanical Strength RTI (°C) row
corrosion:
  - environment: Low Earth orbit, atomic oxygen
    headline: NASA's erosion study ranks Kapton H as eroding more than fluoropolymers, and no HPP-ST erosion yield was recorded.
    effect: The NASA report says some polymers, such as the fluoropolymers, had low erosion yields compared with polyimide Kapton H. Kapton HPP-ST is a different grade, so its erosion yield is not recorded in this profile.
    rating: moderate
    conditions:
      basis: Kapton H, a different grade from HPP-ST, exposed in low Earth orbit on MISSE 2 per the NASA report
    source: nasa-tm-2008-215490
    where: Introduction, paragraph beginning "As LEO erosion yield data gradually became available"
  - environment: Heat in air at 325 °C, Type HN film
    headline: The summary PDF plots strength and elongation retained after air ageing at 325 °C, for Type HN and not HPP-ST.
    effect: Figures 6 and 7 plot tensile strength and elongation retained for 25 µm Type HN film after ageing in air at 325 °C. The retention values sit on the curves and are not printed as numbers in the text, so no retention figure is recorded.
    rating: unknown
    conditions:
      basis: Type HN film, 25 µm (1 mil), not HPP-ST
    source: qnity-kapton-summary
    where: Figures 6 and 7, Thermal Aging section
  - environment: Solvents and 2 N hydrochloric acid, 10 min at 23 °C, Type HN film
    headline: Type HN keeps most of its tensile strength in common solvents, and hydrochloric acid gives the lowest retention in Table 10.
    effect: Table 10 prints tensile retained after isopropyl alcohol, toluene, methyl ethyl ketone, methylene chloride with trichloroethylene, and 2 N hydrochloric acid. The summary says HPP-ST chemical properties are similar to HN; this is a statement, not a test on HPP-ST.
    rating: low
    conditions:
      basis: Typical values for Type HN film, 25 µm (1 mil); HPP-ST described as similar
    source: qnity-kapton-summary
    where: Table 10, Chemical Properties of Kapton Type HN Film, 25 µm, and the paragraph before it
  - environment: Hot water at 100 °C, Type HN film
    headline: Strength and elongation after exposure to 100 °C water are plotted for HN, and no HPP-ST water-exposure value was read.
    effect: Figures 3 and 4 plot tensile strength and ultimate elongation after exposure to 100 °C water for 25 µm Type HN film.
    rating: unknown
    conditions:
      basis: Type HN film, 25 µm (1 mil), not HPP-ST
    source: qnity-kapton-summary
    where: Figures 3 and 4, mechanical properties section
risks:
  hazards:
    - text: The summary PDF says Kapton is unlikely to add appreciably to fire hazards in storage or use. Bulk quantities over 100 lb should be stored away from flammable materials, and firefighters should use a fresh air supply or respirator.
      ghs: []
      source: qnity-kapton-summary
      where: Safety and Handling, Fire Hazards
    - text: The summary PDF says processing can generate a strong static charge, which can build to many thousands of volts. In dust- or solvent-laden air, a flash fire or explosion could result.
      ghs: []
      source: qnity-kapton-summary
      where: Safety and Handling, Static Electricity
    - text: The monomer pyromellitic dianhydride carries GHS signal word Danger, with hazard statements H317, H318 and H334.
      ghs:
        - H317
        - H318
        - H334
      source: wikipedia-pmda
      where: Chembox, Hazards section
    - text: The monomer 4,4'-oxydianiline carries GHS signal word Danger, with hazard statements H301, H311, H331, H340, H350, H361f and H411.
      ghs:
        - H301
        - H311
        - H331
        - H340
        - H350
        - H361f
        - H411
      source: wikipedia-oda
      where: Chembox, Hazards section
  failure_risks:
    - mode: Atomic oxygen erosion in low Earth orbit
      trigger: Polyimide film exposed to atomic oxygen in low Earth orbit
      consequence: NASA ranks Kapton H as eroding more than fluoropolymers, so bare film would need cover. No HPP-ST erosion yield was recorded.
      severity: moderate
      source: nasa-tm-2008-215490
      where: Introduction, erosion comparison paragraph
    - mode: Strength loss after heat ageing in air
      trigger: Air ageing at 325 °C, Type HN data
      consequence: Strength and elongation retention are plotted for HN and are not printed as HPP-ST values, so the HPP-ST margin is not recorded.
      severity: moderate
      source: qnity-kapton-summary
      where: Figures 6 and 7, Thermal Aging section
    - mode: Dielectric breakdown of thin film
      trigger: AC voltage above the breakdown value on 25.4 µm film
      consequence: The minimum breakdown for 25.4 µm film is 236 kV/mm (ASTM D-149), so a design margin is needed above that value.
      severity: moderate
      source: qnity-kapton-spec
      where: Table 3, Electrical Properties of Kapton HN polyimide film, column 1.00 (25.4)
  side_effects: []
  handling:
    - text: The summary PDF says soldering rarely produces off-gases of toxicological significance, and that a heated element can remove insulation.
      source: qnity-kapton-summary
    - text: Use adequate ventilation when handling Kapton at high temperatures, and remove the film from equipment before direct welding.
      source: qnity-kapton-summary
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Flexible printed circuit substrate and PCB stencil
    example: The product page lists electronic parts, printed circuit board stencils, screen printing and insulation tubing as applications for Kapton HPP-ST.
    source: qnity-hpp-st-page
    where: Kapton HPP-ST product page, Applications list
  - application: solar-arrays
    device: Spacecraft solar array and thermal management film (Kapton family)
    example: The summary PDF says Kapton is used in applications such as the solar array and for thermal management in the United States space program. This describes the Kapton family, not HPP-ST alone.
    source: qnity-kapton-summary
    where: Opening paragraph of the Summary of Properties, page 1
supply:
  - subject: Kapton HPP-ST film (manufacturer)
    demand: Qnity Electronics is the named manufacturer. Wikipedia says Kapton has been manufactured by Qnity Electronics since November 2025, as a spinoff of DuPont. No market share, tonnage or country split for Kapton film was found in any source read.
    routes: Kapton is made from a polyamic acid precursor that is cured to polyimide film. The manufacturer calls HPP-ST an all-polyimide film with a surface treatment on both sides for adhesion.
    producers: []
    critical_lists: []
    substitutes: []
    source: wikipedia-kapton
    where: History (manufacturer as of November 2025); 3D printing section (polyamic acid precursor); summary PDF, Types of Kapton
  - subject: Pyromellitic dianhydride (PMDA), dianhydride monomer
    demand: Wikipedia says PMDA is the dianhydride used to prepare polyimide polymers such as Kapton. No producer or tonnage was found in the page read.
    routes: Wikipedia says PMDA is prepared by gas-phase oxidation of 1,2,4,5-tetramethylbenzene, or related tetrasubstituted benzene derivatives.
    producers: []
    critical_lists: []
    substitutes: []
    source: wikipedia-pmda
    where: Preparation section; Chembox
  - subject: 4,4'-Oxydianiline (ODA), diamine monomer
    demand: Wikipedia says the primary use of ODA is in polyimide and poly(ester)imide resins, and that it is the diamine condensed with PMDA to make Kapton. No producer or tonnage was found in the page read.
    routes: The route to ODA is not described in the page read.
    producers: []
    critical_lists: []
    substitutes: []
    source: wikipedia-oda
    where: Uses section
documents:
  - title: Qnity Electronics product page, Kapton HPP-ST polyimide film (Product Properties table)
    type: datasheet
    url: https://www.qnityelectronics.com/products/kapton-hpp-st-polyimide-film
    year: 2026
  - title: Qnity Electronics, Kapton Summary of Properties (PDF)
    type: datasheet
    url: https://ekce-p-001.sitecorecontenthub.cloud/api/public/content/810b258c62404e42855984f345fdf8d7?v=a2916962
  - title: Qnity Electronics, Kapton polyimide film specifications and tolerances (PDF)
    type: datasheet
    url: https://ekce-p-001.sitecorecontenthub.cloud/api/public/content/599767bd7af84d92827184ea3728c2b3?v=5670ee5b
  - title: Banks, de Groh and Backus, Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit, NASA/TM-2008-215490
    type: report
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
gaps:
  - No HPP-ST value was read for coefficient of thermal expansion, glass transition, specific heat or melting point. The summary PDF prints these for Type 100 HN only, and it gives the melting point as None (ASTM E-794).
  - Atomic oxygen erosion yields for Kapton H and HN in NASA/TM-2008-215490 are printed in exponent form, so they are not recorded here. No HPP-ST erosion yield was read.
  - Radiation, UV and outgassing data for HPP-ST were not read as HPP-ST values. The summary's radiation and chemical tables are for Type HN, and the summary says HPP-ST chemical properties are similar to HN.
  - 'Thermal conductivity conflicts across grades: the product page gives 0.12 W/mK for 100HPP-ST, and the summary PDF gives 0.20 W/m K for Type 100 HN. The HN value is a different grade, so only the HPP-ST value is recorded.'
  - The product page does not map a test standard to each column in the text read, so the method on those rows says so. Where the summary PDF prints the same value by a named standard, that is cited in the method.
  - Limiting oxygen index and relative thermal index are not canonical names in property-canon.yaml, so custom names are used.
  - Producer shares, country splits and tonnage for Kapton film were not found in any source read. Qnity Electronics is named as the manufacturer, and the monomers have no producer figures.
  - No Qnity safety data sheet for HPP-ST was read. Hazard entries come from the summary PDF safety section and from the Wikipedia Chembox data for the two monomers.
  - Moisture absorption is printed as two values for HN and HPP-ST in the summary PDF with no clear row label in the text read, so it is not recorded.
  - Tear strength (Elmendorf and Graves) and folding endurance for 25 µm HPP-ST are printed in the summary PDF Table 3 but have no canonical property name, so they are not recorded.
sources:
  qnity-hpp-st-page:
    title: Kapton HPP-ST polyimide film, Qnity Electronics product page
    id: Product Properties table (row Kapton 100HPP-ST), Classification block, Applications list
    url: https://www.qnityelectronics.com/products/kapton-hpp-st-polyimide-film
    year: 2026
    kind: datasheet
    license: manufacturer web page, linked not reproduced
  qnity-kapton-summary:
    title: Kapton Summary of Properties, Qnity Electronics (PDF)
    id: Table 3 (HPP-ST), Table 7 (electrical, HN and HPP-ST), Table 10 (chemical, HN), Safety and Handling
    url: https://ekce-p-001.sitecorecontenthub.cloud/api/public/content/810b258c62404e42855984f345fdf8d7?v=a2916962
    kind: datasheet
    license: manufacturer PDF, linked not reproduced
  qnity-kapton-spec:
    title: Kapton polyimide film specifications and tolerances, Qnity Electronics (PDF)
    id: Table 2 (mechanical, HN, footnote applies to HPP-ST), Table 3 (electrical, HN), Table 5 (HPP-ST shrinkage)
    url: https://ekce-p-001.sitecorecontenthub.cloud/api/public/content/599767bd7af84d92827184ea3728c2b3?v=5670ee5b
    kind: datasheet
    license: manufacturer PDF, linked not reproduced
  nasa-tm-2008-215490:
    title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
    id: NASA/TM-2008-215490 (Banks, de Groh and Backus, 2008), NTRS 20090011780
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
    kind: report
    license: NASA public document
  wikipedia-kapton:
    title: Kapton, Wikipedia
    id: Kapton article, History, Chemistry and variants, Usage (Spacecraft), 3D printing
    url: https://en.wikipedia.org/wiki/Kapton
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
  wikipedia-polyimide:
    title: Polyimide, Wikipedia
    id: Polyimide article, lead section (Kapton condensation of PMDA and ODA)
    url: https://en.wikipedia.org/wiki/Polyimide
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
  wikipedia-pmda:
    title: Pyromellitic dianhydride, Wikipedia
    id: Chembox (identifiers, properties, GHS hazards), Preparation section
    url: https://en.wikipedia.org/wiki/Pyromellitic_dianhydride
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
  wikipedia-oda:
    title: 4,4'-Oxydianiline, Wikipedia
    id: Chembox (identifiers, properties, GHS hazards), Uses section
    url: https://en.wikipedia.org/wiki/4,4%27-Oxydianiline
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 15
  unreachable: 0
  caveats: 3
  note: Values were read by an AI assistant on 2026-11-01 from the pages named in each entry. Product-page values are typical values with no test standard mapped to each column in the text read. Minimum and maximum values come from the specification PDF and apply to HN and HPP-ST by its footnote. The thermal conductivity value is for 100HPP-ST only.
story:
  recipe:
    line: Kapton HPP-ST is a polyimide film. Wikipedia says Kapton is produced by condensation of pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA). The NASA report prints the repeat unit as C22H10O5N2 for Kapton H and HN, and the manufacturer describes HPP-ST as an all-polyimide film with the properties of Type HN.
    parts:
      - name: Carbon
        symbol: C
        role: '22 carbon atoms per repeat unit (C22H10O5N2, NASA report): the aromatic rings of the dianhydride and diamine units, plus the imide carbonyl carbons.'
      - name: Hydrogen
        symbol: H
        role: 10 hydrogen atoms per repeat unit (C22H10O5N2, NASA report), on the aromatic rings.
      - name: Oxygen
        symbol: O
        role: '5 oxygen atoms per repeat unit (C22H10O5N2, NASA report): the carbonyl oxygens of the imide rings and the ether oxygen of the oxydiphenylene unit.'
      - name: Nitrogen
        symbol: 'N'
        role: '2 nitrogen atoms per repeat unit (C22H10O5N2, NASA report): the imide nitrogens that join the dianhydride and diamine units.'
  risk_groups:
    - title: For people
      lead: The finished film has no GHS classification printed in the sources read, but its two monomers carry GHS Danger hazard statements.
      level: 0
      verdict: Film low hazard; monomers GHS Danger
      points:
        - label: Film
          line: The summary PDF says Kapton is unlikely to add appreciably to fire hazards in storage or use. Bulk quantities over 100 lb should be kept away from flammable materials.
        - label: Static
          line: Processing can generate a strong static charge, which can build to many thousands of volts and cause a flash fire in dust or solvent-laden air.
        - label: Monomers
          line: Pyromellitic dianhydride carries Danger with H317, H318 and H334. 4,4'-oxydianiline carries Danger with H301, H311, H331, H340, H350, H361f and H411 (Wikipedia Chembox).
    - title: If it fails
      lead: The failure routes in these sources are atomic oxygen erosion in low Earth orbit and strength loss after heat ageing for HN.
      level: 1
      verdict: Erosion in orbit; heat ageing shown for HN
      points:
        - label: Atomic oxygen
          line: NASA ranks Kapton H as eroding more than fluoropolymers in low Earth orbit. No HPP-ST erosion yield was recorded, because the NASA values are printed in exponent form.
        - label: Heat
          line: The summary PDF plots strength retained after air ageing at 325 °C for Type HN, not HPP-ST.
  why: Kapton HPP-ST is an all-polyimide film from Qnity Electronics with a surface treatment for adhesion. The 100HPP-ST grade (25.4 µm, 1 mil) has a tensile strength of 231.0 MPa and an elongation at break of 72 % at 23 °C, as printed on the manufacturer product page. Its dielectric strength is 303 kV/mm, and the specification caps shrinkage at 0.10 % after 1 hour at 200 °C.
  uses:
    - where: Use
      line: Flexible printed circuit substrate and PCB stencil film, with screen printing and insulation tubing, as listed on the product page.
    - where: Use
      line: Spacecraft solar array and thermal management film, in the Kapton family, as stated in the summary PDF.
  can_do:
    - label: Carry a thin load
      line: 231.0 MPa tensile strength and 72 % elongation at break at 23 °C for 100HPP-ST (product page).
    - label: Hold its shape in heat
      line: shrinkage at most 0.10 % after 1 hour at 200 °C (specification Table 5, 25.4 µm).
    - label: Insulate a thin film
      line: 303 kV/mm dielectric strength and a dielectric constant of 3.40 at 1 kHz for 100HPP-ST.
    - label: Burn slowly
      line: limiting oxygen index of 37 % for 25 µm HPP-ST (ASTM D-2863, summary PDF).
  compare: Every value here is for one manufacturer's HPP-ST film, read from its product page and summary PDF, so the figures are typical or specification values, not a ranking against other polyimide films. The 231.0 MPa tensile strength and 1.42 g/cc density are typical for 25 µm film, and the 165 MPa minimum is the specification floor for the same thickness. The 303 kV/mm dielectric strength is typical, against a 236 kV/mm minimum.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
    - label: Dielectric strength
      benchmark: dielectric_strength
  handling:
    - Name the grade, since HPP-ST and HN share some values but the surface treatment and shrinkage limits differ.
    - Check the current supplier data sheet, since the product page and summary PDF give typical values with no test standard for each column.
    - Keep film in a ventilated area when heating or welding, and remove it from equipment before direct welding.
  good_for:
    - Flexible circuit and stencil films where adhesion treatment and 231.0 MPa tensile strength at 23 °C matter.
    - 'Thin insulation at high voltage: 303 kV/mm dielectric strength at 25.4 µm, from the product page.'
  watch_out:
    - 'Heat rating under load: the relative thermal indices are 240 °C (electrical) and 200 °C (mechanical) under UL 746B. These are ratings, not service limits.'
    - 'Atomic oxygen: NASA ranks Kapton H as eroding more than fluoropolymers in low Earth orbit. No HPP-ST erosion yield was recorded.'
    - 'Thermal conductivity: the product page gives 0.12 W/mK for 100HPP-ST, and the summary PDF gives a different value for Type 100 HN.'
  verdict: Kapton HPP-ST is a 25.4 µm all-polyimide film with a tensile strength of 231.0 MPa, an elongation at break of 72 % and a dielectric strength of 303 kV/mm at 23 °C, per the manufacturer. Its heat ratings are UL 746B indices, and no HPP-ST data for in-orbit erosion or ageing were read.