spore: profile
id: pet
spore_version: 0.2
family: polyesters
name: Polyethylene terephthalate (PET), including biaxially oriented film (Mylar)
abbreviation: PET
role: Polyester film for thermal blankets, solar sails and electrical insulation
category: polymers
type: polyesters
summary: |
  PET is a polyester made from terephthalic acid and ethylene glycol. Biaxially oriented PET film, sold as Mylar by DuPont Teijin Films, is a tough, flat, chemically resistant film with a density of 1.390 g/cm3 and a melting point of 254 degC (DSC). It was on the MISSE 2 tray outside the ISS for about four years, where its atomic-oxygen erosion yield was 3.01e-24 cm3/atom. Aluminized PET film is the reflective core of multilayer insulation blankets and of the 4.5 micron sails on NASA's LightSail spacecraft.
best_for: Thin, lightweight, flexible film where low mass and tensile strength matter, and where it sits in vacuum away from direct sunlight (multilayer insulation, sails, electrical insulation)
weakest_at: 'Water and heat over time: Mylar hydrolyzes under high temperature and humidity, and in LEO atomic oxygen erodes it (MISSE 2, 3.01e-24 cm3/atom)'
identity:
  formula: (C10H8O4)n, repeat unit C10H8O4 (polyethylene terephthalate, from terephthalic acid and ethylene glycol)
  cas: 25038-59-9
  source: nasa-tm2008
  where: Polymer physical properties table, section 2.2 of NASA/TM-2008-215490 (repeat unit C10H8O4, molar mass 192.1708); CAS number from the Lumirror SDS (section 3, composition)
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
    - uv
    - thermal-cycling
    - vacuum-and-outgassing
    - hydrolysis
  applications:
    - thermal-control
    - propulsion-and-tanks
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, Mylar polyester film (typical)
    value: 1.39
    unit: g/cm3
    scope: material
    conditions:
      grade: Mylar, Mylar 1000A and 92A types as listed in the bulletin
      test: ASTM D1505
    method: Typical value printed in the DuPont Mylar physical-thermal properties table (Table 1)
    status: ground
    source: dupont-bulletin
    where: Table 1, Density
  - benchmark: density
    label: Density, polyethylene terephthalate (Goodfellow ES300 film)
    value: 1.35
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 degC (77 degF)
    method: Value printed in the supplier safety data sheet; a cross-check on the Mylar figure above
    status: ground
    source: goodfellow-sds
    where: Section 9, Density
  - benchmark: melting_point
    label: Melting point, Mylar polyester film
    value: 254
    unit: degC
    scope: material
    conditions:
      method: DSC
    method: Typical value printed in the DuPont Mylar physical-thermal properties table (Table 1)
    status: ground
    source: dupont-bulletin
    where: Table 1, Melt Point
  - benchmark: melting_point
    label: Melting point, PET film (Questar SDS)
    value: 256
    value_high: 265
    unit: degC
    scope: material
    conditions:
      note: Lower for modified resins, as the SDS states
    method: Range printed in the Questar film safety data sheet
    status: ground
    source: questar-sds
    where: Section 9, Melting Point
  - benchmark: glass_transition_temperature
    label: Glass transition temperature, PET bottle-grade copolymer
    value: 76
    unit: degC
    scope: material
    conditions:
      basis: semi-crystalline PET copolymer quoted in the introduction of the UV-aging paper; not a Mylar datasheet value
    method: Approximate value quoted by the cited paper in its introduction (approximately 76 degC)
    status: ground
    source: pmc-uv-aging
    where: Introduction, first paragraph on PET bottles
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Mylar A film 50 micron, machine direction
    value: 190
    unit: MPa
    scope: material
    conditions:
      thickness: 50 micron
      direction: MD
      test: ASTM D 882
    method: Typical value in the DuPont Teijin Mylar A 50 to 125 micron product information; the text says the tensile strength averages 190 MPa
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Tensile Strength row, 50 micron column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Mylar A film 50 micron, transverse direction
    value: 210
    unit: MPa
    scope: material
    conditions:
      thickness: 50 micron
      direction: TD
      test: ASTM D 882
    method: Typical value from the same table
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Tensile Strength row, TD, 50 micron column
  - benchmark: elastic_modulus
    label: Tensile modulus, Mylar A film 50 micron, machine direction
    value: 3800
    unit: MPa
    scope: material
    conditions:
      thickness: 50 micron
      direction: MD
      test: ASTM D 882
    method: Typical value printed in the DuPont Teijin Mylar A product information
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Modulus row, 50 micron column
  - benchmark: elongation
    label: Elongation at break, Mylar A film 50 micron, machine direction
    value: 140
    unit: '%'
    scope: material
    conditions:
      thickness: 50 micron
      direction: MD
      test: ASTM D 882
    method: Typical value printed in the DuPont Teijin Mylar A product information
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Elongation row, 50 micron column
  - benchmark: elongation
    label: Elongation at break, Mylar A 12 micron (MD)
    value: 100
    unit: '%'
    scope: material
    conditions:
      thickness: 12 micron
      direction: MD
      test: ASTM D 882
    method: Typical value printed in the DuPont Teijin Mylar A 12 to 36 micron product information
    status: ground
    source: dupont-mylar-a-12-36
    where: Film Properties table, Elongation row, 12 micron column
  - benchmark: specific_heat
    label: Specific heat, Mylar polyester film
    value: 0.28
    unit: cal/g/degC
    scope: material
    conditions:
      temperature: not stated in the bulletin
    method: Typical value in the DuPont Mylar physical-thermal properties bulletin, printed in calories as the bulletin gives it
    status: ground
    source: dupont-bulletin
    where: Table 1, Specific Heat
  - benchmark: cte
    label: Coefficient of thermal expansion, Mylar
    value: 0.000017
    unit: in/in/degC
    scope: material
    conditions:
      test: ASTM D 696
    method: Typical value printed in the bulletin (text gives 9.5e-6 in/in/degF)
    status: ground
    source: dupont-bulletin
    where: Table 1, Coefficients of Thermal Expansion; text under Thermal Expansion
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Mylar 1000A
    value: 0.00037
    unit: cal cm/(cm2 s degC)
    scope: material
    conditions:
      temperature: 25 to 75 degC (77 to 167 degF)
      grade: Mylar 1000A
    method: Value printed in the DuPont Mylar bulletin; printed unit kept as given
    status: ground
    source: dupont-bulletin
    where: Table 1, Thermal Conductivity (Mylar 1000A)
  - benchmark: max_service_temp
    label: Maximum recommended service temperature, Mylar
    value: 150
    unit: degC
    scope: material
    conditions:
      exposure: air, uncoated film
    method: Recommended maximum printed in the bulletin under Heat Aging; coatings are said to improve heat-aging resistance
    status: ground
    source: dupont-bulletin
    where: Heat Aging section
  - benchmark: dielectric_strength
    label: Dielectric strength (minimum), Mylar A 50 micron
    value: 7.7
    unit: kV
    scope: material
    conditions:
      thickness: 50 micron
      test: ASTM D 149
      type: minimum
    method: Minimum value printed in the DuPont Teijin Mylar A 50 to 125 micron table; printed unit kV
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Dielectric Strength row
  - benchmark: atomic_oxygen_erosion_yield
    label: Atomic oxygen erosion yield, PET (Mylar), MISSE 2 PEACE
    value: 3.01e-24
    unit: cm3/atom
    scope: material
    conditions:
      exposure: ISS, MISSE 2 PEACE tray 1, 2001-08-16 to 2005-07-30 (3.95 years)
      fluence: 8.43e21 atoms/cm2
      solar: 5000 to 6700 equivalent sun hours
      thermal_cycling: '-30 to 40 degC (nominal base-plate range)'
    method: Flight-measured erosion yield listed in Table I of NASA/TM-2008-215490; copied from the MISSE 2 passport (misse2-pet-mylar)
    status: flight
    source: nasa-tm2008
    where: Table I, MISSE 2 PEACE polymers erosion yield data, Polyethylene terephthalate PET (Mylar) row
  - benchmark: total_mass_loss
    label: Total mass loss (TML), Mylar Type A film, NASA outgassing data
    value: 0.19
    unit: '%'
    scope: material
    conditions:
      test: ASTM E595, vacuum outgassing
      supplier: DuPont, GSC sample 10368
    method: Value from the NASA Goddard outgassing data compilation (NASA RP-1124, revision 4)
    status: ground
    source: nasa-rp1124
    where: Films and Sheet Materials section, row MYLAR TYPE A FILM
  - benchmark: collected_volatile_condensable_material
    label: Collected volatile condensable material (CVCM), Mylar Type A film
    value: 0
    unit: '%'
    scope: material
    conditions:
      test: ASTM E595, vacuum outgassing
      supplier: DuPont, GSC sample 10368
    method: Value from the NASA Goddard outgassing data compilation (NASA RP-1124, revision 4)
    status: ground
    source: nasa-rp1124
    where: Films and Sheet Materials section, row MYLAR TYPE A FILM
  - benchmark: water_vapor_regained
    label: Water vapor regained (WVR), Mylar Type A film
    value: 0.14
    unit: '%'
    scope: material
    conditions:
      test: ASTM E595, vacuum outgassing
      supplier: DuPont, GSC sample 10368
    method: Value from the NASA Goddard outgassing data compilation (NASA RP-1124, revision 4)
    status: ground
    source: nasa-rp1124
    where: Films and Sheet Materials section, row MYLAR TYPE A FILM
  - benchmark: dimensional_shrinkage_150c_30min
    label: Dimensional shrinkage at 150 degC for 30 min, Mylar A 50 micron, machine direction
    value: 1.2
    unit: '%'
    scope: material
    conditions:
      thickness: 50 micron
      direction: MD
      test: ASTM D 1204
    method: Typical value printed in the DuPont Teijin Mylar A 50 to 125 micron product information (name not in property-canon.yaml)
    status: ground
    source: dupont-mylar-a-50-125
    where: Film Properties table, Shrinkage 150 degC for 30 min row, 50 micron column
  - benchmark: elongation
    label: Elongation after UV aging, amorphous PET film (A-PET, not Mylar)
    value: 5.61
    unit: '%'
    scope: material
    conditions:
      film: amorphous PET (A-PET), three-layer, 100 pct virgin
      uv_exposure: 1 h at 2.45 W/m2 dose rate in the UV aging chamber
      before_uv: 16.84 %
    method: Average relative elongation after one hour of UV exposure, as reported in the UV-aging study; this is a different film from biaxially oriented Mylar
    status: ground
    source: pmc-uv-aging
    where: Results, relative elongation at the breaking force (Figure 11 discussion)
corrosion:
  - environment: Atomic oxygen in low Earth orbit (MISSE 2 PEACE, ISS, about 4 years)
    headline: Erosion yield of 3.01e-24 cm3/atom after 3.95 years, compared with 3.74e-24 for polyethylene in the same table.
    effect: PET is eroded by atomic oxygen at about the rate recorded for other common polymers. The flight value comes from the same table as the 3.01e-24 yield in the properties section, so it is directly comparable with other polymers on MISSE 2.
    rating: moderate
    conditions:
      fluence: 8.43e21 atoms/cm2
      environment: LEO flight, 2001 to 2005
    source: nasa-tm2008
    where: Table I; exposure details in section 2.1
  - environment: Ultraviolet light in air (accelerated chamber and sunny day)
    headline: Amorphous PET film lost much of its plasticity after brief UV exposure, falling from 16.84 % to 5.61 % relative elongation after one hour.
    effect: The UV-aging study on A-PET found a significant loss of plasticity even after brief exposure to solar irradiance, and the recycled film degraded more. The same paper reports a melting-point drop for aged PET bottles from 249.8 degC to 243.1 degC indoors and to 245.6 degC in sunlight, and a glass-transition rise from 74 degC to 87 degC after 670 days outdoors. These are bottle-grade and amorphous films, not Mylar, so they show the trend but are not Mylar values.
    rating: severe
    conditions:
      dose_rate: 2.45 W/m2
      test: UV aging chamber, then tensile testing at 21.1 degC and 43 % RH
      film: amorphous PET (A-PET)
    source: pmc-uv-aging
    where: Abstract; Results; Discussion of UV aging of PET bottles
  - environment: High temperature and humidity (hydrolysis)
    headline: Mylar hydrolyzes and becomes brittle under high temperature and humidity; steam exposure at 100 degC reduces strength and modulus.
    effect: Hydrolysis needs water. The DuPont bulletin says more than 0.1 % water must be present before the film embrittles, and recommends drying at 160 degC for 4 hours (vacuum drying). Keep hermetic units dry.
    rating: moderate
    conditions:
      steam: 100 degC (212 degF)
      drying: 160 degC for 4 hr
    source: dupont-bulletin
    where: Hydrolytic Stability section; Figures 7 to 10
  - environment: Dry heat (air)
    headline: Continuous service is recommended up to 150 degC; processing should stay below 200 degC.
    effect: At 220 degC for 30 min the film loses about 10 % of its tensile strength, and it becomes brittle and shatters after heating at 235 degC for under one minute.
    rating: moderate
    conditions:
      air: uncoated Mylar
      heat_aging_temp: 150 degC in air, time axis of Figures 11 and 12
    source: dupont-bulletin
    where: Heat Aging section; text on processing conditions
  - environment: Thermal cycling and humidity changes (dimensional stability)
    headline: Strain-relief shrinkage at 150 degC is 1.2 % MD and 1.1 % TD for Mylar A at 50 micron, and 1.8 % MD for Mylar 92A at 150 degC.
    effect: Film shrinks when heated because it relaxes strains from manufacture. Mylar A shrinkage at 200 degC for 30 min is 2.8 % MD at 50 micron, so the 200 degC figure is more than twice the 150 degC figure.
    rating: low
    conditions:
      test: ASTM D 1204, 150 degC or 200 degC for 30 min
    source: dupont-mylar-a-50-125
    where: Film Properties table, Shrinkage rows (50 micron); bulletin Dimensional Stability table
risks:
  hazards:
    - text: 'Supplier SDS for polyethylene terephthalate (Lumirror, more than 99 % PET, CAS 25038-59-9): not classified under GHS (US), and labelling not applicable as the product is an article under 29 CFR 1910.1200.'
      ghs: []
      source: lumirror-sds
      where: Sections 2.1, 2.2 and 2.3
    - text: 'Goodfellow SDS for polyethylene terephthalate (ES300): classification not classified; hazard statements read no known significant effects or critical hazards.'
      ghs: []
      source: goodfellow-sds
      where: Section 2 and section 11
    - text: Decomposition temperature above 300 degC (Questar SDS). Flash or ignition temperature 497 degC, and combustible dust may form when processing.
      ghs: []
      source: questar-sds
      where: Section 9, Flash/Ignition Temp; section 9, Decomposition
    - text: Dust from processing may be combustible, and processing may form combustible dust concentrations in air.
      ghs: []
      source: lumirror-sds
      where: Section 2.3 and section 5 (fire hazard)
  failure_risks:
    - mode: Overheating above the processing limit
      trigger: Heating at 220 degC for 30 min, or at 235 degC for under one minute
      consequence: Loses about 10 % of tensile strength at 220 degC and becomes brittle, shattering at 235 degC.
      severity: moderate
      source: dupont-bulletin
      where: Heat Aging section
    - mode: Hydrolytic embrittlement
      trigger: High temperature and humidity, with more than 0.1 % water in a sealed system
      consequence: Film becomes brittle; tensile strength and modulus fall after steam exposure at 100 degC.
      severity: moderate
      source: dupont-bulletin
      where: Hydrolytic Stability section
    - mode: Atomic oxygen erosion in low Earth orbit
      trigger: LEO exposure, 8.43e21 atoms/cm2 fluence over 3.95 years
      consequence: Erodes the surface at 3.01e-24 cm3/atom; thin films can erode through completely.
      severity: moderate
      source: nasa-tm2008
      where: Table I and section 2.1
  side_effects:
    - text: Decomposition in a fire or at high temperature may release acetaldehyde (CAS 75-07-0) at a low level, and the SDS warns of toxic fumes when heated to decomposition.
      affects: People in the area of an overheating film or fire; nearby hardware
      source: questar-sds
      where: Section 10, Decomposition
    - text: Molten film causes thermal burns on contact, and the material can take on a static charge during handling.
      affects: Operators during processing or hot-melt handling
      source: lumirror-sds
      where: Sections 2.3 and 7
  handling:
    - text: 'Dry the film before sealing: heat for 4 hr at 160 degC to bring water below 0.1 %. Drying at lower temperatures is less effective (bulletin Figure 10).'
      source: dupont-bulletin
      where: Hydrolytic Stability section
    - text: Keep processing below 200 degC; film can be damaged above that temperature.
      source: dupont-bulletin
      where: Heat Aging section
    - text: Avoid dust formation. Use exhaust ventilation where dust forms and avoid breathing fumes from molten material.
      source: lumirror-sds
      where: Sections 7 and 8
  mitigations:
    - text: Keep the film dry in hermetically sealed units, and coat it to improve heat-aging resistance (the bulletin says coatings are available).
      source: dupont-bulletin
      where: Hydrolytic Stability and Heat Aging sections
    - text: 'Count on atomic-oxygen erosion in LEO: MISSE 2 PET eroded at 3.01e-24 cm3/atom over about four years, so flight film needs a protective coating or thicker stack.'
      source: nasa-tm2008
      where: Table I
uses:
  - application: thermal-control
    device: Multilayer insulation (MLI) blankets for spacecraft and cryogenic tanks
    example: A typical MLI system uses a large number of highly reflective shields of aluminized polyester film, separated by low-conductivity spacers such as silk netting. Performance approaches the ideal when heat transfer normal to the shields is pure radiation.
    source: nasa-tn-mli-1971
    where: Introduction
  - application: propulsion-and-tanks
    device: Solar sail membrane (LightSail spacecraft)
    example: LightSail's sail is aluminized 4.5 micron Mylar film, giving 32 square meters of sail area fully deployed. LightSail-A flew in 2015 and LightSail-B in 2016.
    source: nasa-sail-2017
    where: LightSail-A and -B slide
  - application: electronics-and-chips
    device: Electrical insulation film and laminates
    example: DuPont Teijin says Type A Mylar is primarily used for release applications, office supplies, electrical insulation and laminations with other flexible materials.
    source: dupont-mylar-a-50-125
    where: Product Description
supply:
  - subject: PET resin (bottle-grade capacity; film is made from the same polymer)
    abundance: In 2022 global effective capacity for bottle-grade PET resin was around 34.7 m tonnes, up from about 16 m tonnes in 2010.
    producers:
      - country: China
        share_percent: 38
        year: 2022
    critical_lists: []
    recycling: Not read in a source for this run.
    substitutes: []
    source: czapp-pet-capacity
    where: Where in the World is PET Resin Produced; China share is of world PET resin capacity, a percentage the page gives as around 38 %
  - subject: Terephthalic acid (PTA), the main feedstock
    abundance: It takes 0.855 metric tons of PTA to produce 1 metric ton of PET (CZCE). PTA is one of the end products of petroleum refining.
    producers: []
    critical_lists: []
    recycling: Not read in a source for this run.
    substitutes: []
    source: czce-pta
    where: Section II, Major uses; Section III, production process
  - subject: Mono ethylene glycol (MEG), the second feedstock
    abundance: It takes 0.335 metric tons of mono ethylene glycol to produce 1 metric ton of PET (CZCE).
    producers: []
    critical_lists: []
    recycling: Not read in a source for this run.
    substitutes: []
    source: czce-pta
    where: Section II, Major uses
documents:
  - title: DuPont Teijin Films, Mylar polyester film physical-thermal properties bulletin (copy hosted at stenbacka.fi)
    type: datasheet
    url: https://stenbacka.fi/wp-content/uploads/sites/3/2016/07/mylar_a_fysikaaliset_ominaisuudet.pdf
    year: 2016
  - title: DuPont Teijin Films, Mylar A product information, 12 to 36 micron
    type: datasheet
    url: https://docs.rs-online.com/aafb/0900766b81111eb5.pdf
    year: 2016
  - title: Lumirror PET film safety data sheet
    type: sds
    url: https://www.lakeshore.com/docs/default-source/product-downloads/safety-data-sheets/msds-sheet-lumirror-pet.pdf?sfvrsn=6dea7f27_4
    year: 2020
  - title: Goodfellow safety data sheet, polyethylene terephthalate (ES300), version 0.1, revised 01/03/2024
    type: sds
    url: https://www.goodfellow.com/usa/safety-data-sheet/download/pdf/ES300
    year: 2024
  - title: Questar polyester film safety data sheet (Filmquest)
    type: sds
    url: https://www.petfilm.com/wp-content/uploads/2021/05/Filmquest-Questar-SDS.pdf
    year: 2019
  - title: 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
  - title: NASA RP-1124 Rev 4, Outgassing Data for Selecting Spacecraft Materials
    type: report
    url: https://www.vacseal.net/wp-content/uploads/2017/09/Outgassing-Data-for-Selecting-Spacecraft-Materials-REV3.pdf
    year: 1997
  - title: UV aging of A-PET films, Polymers 2023, 15(20):4166 (open access, PMC10610990)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC10610990/
    year: 2023
  - title: NASA Technical Note on thermal analysis of customized multilayer insulation on an unshrouded liquid hydrogen tank
    type: report
    url: https://ntrs.nasa.gov/api/citations/19710012082/downloads/19710012082.pdf
    year: 1971
  - title: From Solar Sails to Laser Sails, Les Johnson (NASA Marshall), 2017
    type: report
    url: https://ntrs.nasa.gov/api/citations/20170012350/downloads/20170012350.pdf
    year: 2017
  - title: CZCE PTA futures and options, overview of PTA (exchange document)
    type: report
    url: https://english.czce.com.cn/en/rootfiles/2023/03/30/1681344050124601-1681344050137474.pdf
    year: 2023
gaps:
  - No Mylar-specific glass transition temperature in a datasheet. The 76 degC value is for a bottle-grade PET copolymer quoted in a paper. The DuPont bulletin gives only a Transition Point on a figure with no number.
  - No PubChem or ECHA hazard record for PET or its monomers could be opened (PubChem returned a reCAPTCHA page). Hazard data for terephthalic acid and ethylene glycol were not read, so their residual-monomer hazards are not covered.
  - Mass percentages of C, H and O in the repeat unit were not computed, because no atomic-weight table was read in this run. Atoms per repeat unit are given instead.
  - No USGS Mineral Commodity Summaries entry covers PTA, MEG or PET. Supply figures come from an industry explainer (CZAPP, 2022 capacity) and an exchange document (CZCE, feedstock ratio), not a government source.
  - The NASA outgassing values are from RP-1124 Rev 4 (1997) for one Mylar Type A sample. The live NASA outgassing portal was not opened.
  - UV numbers come from amorphous A-PET films, not biaxially oriented Mylar. No Mylar UV transmission or tensile-retention datasheet was read.
  - Hydrolysis is described qualitatively in the DuPont bulletin; its rate curves are figures with no numbers in text.
  - Dimensional shrinkage, total mass loss, collected volatile condensable material and water vapor regained use benchmark names outside property-canon.yaml (dimensional shrinkage is not canonical; TML, CVCM and WVR are not canonical). They are noted here for the import step.
  - Only one flight value for PET erosion (MISSE 2, 3.01e-24 cm3/atom). No other LEO or GEO flight of PET film was found in an opened source.
  - Recycling and critical-mineral status for PTA and MEG were not found in an opened source.
sources:
  nasa-tm2008:
    title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit, NASA/TM-2008-215490
    id: NASA/TM-2008-215490 (Banks and Backus, December 2008)
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
    kind: report
    license: NASA public document
  nasa-rp1124:
    title: NASA RP-1124 Rev 4, Outgassing Data for Selecting Spacecraft Materials (Goddard Space Flight Center)
    id: NASA RP-1124 Rev 4
    url: https://www.vacseal.net/wp-content/uploads/2017/09/Outgassing-Data-for-Selecting-Spacecraft-Materials-REV3.pdf
    year: 1997
    kind: report
    license: NASA public document
  dupont-bulletin:
    title: 'DuPont Teijin Films, Mylar polyester film: physical-thermal properties (bulletin)'
    id: DuPont Teijin Films Mylar bulletin, copy hosted at stenbacka.fi
    url: https://stenbacka.fi/wp-content/uploads/sites/3/2016/07/mylar_a_fysikaaliset_ominaisuudet.pdf
    year: 2016
    kind: datasheet
    license: Manufacturer product information (cited, not reproduced)
  dupont-mylar-a-50-125:
    title: DuPont Teijin Films, Mylar A product information, 50 to 125 micron
    id: DuPont Teijin Films Mylar A 50-125 um
    url: https://docs.rs-online.com/aafb/0900766b81111eb5.pdf
    year: 2016
    kind: datasheet
    license: Manufacturer product information (cited, not reproduced)
  dupont-mylar-a-12-36:
    title: DuPont Teijin Films, Mylar A product information, 12 to 36 micron
    id: DuPont Teijin Films Mylar A 12-36 um
    url: https://docs.rs-online.com/aafb/0900766b81111eb5.pdf
    year: 2016
    kind: datasheet
    license: Manufacturer product information (cited, not reproduced)
  lumirror-sds:
    title: Lumirror polyester (PET) film safety data sheet
    id: Lumirror PET SDS
    url: https://www.lakeshore.com/docs/default-source/product-downloads/safety-data-sheets/msds-sheet-lumirror-pet.pdf?sfvrsn=6dea7f27_4
    year: 2020
    kind: datasheet
    license: Supplier SDS (cited, not reproduced)
  goodfellow-sds:
    title: Goodfellow safety data sheet, polyethylene terephthalate ES300
    id: Goodfellow ES300 SDS
    url: https://www.goodfellow.com/usa/safety-data-sheet/download/pdf/ES300
    year: 2024
    kind: datasheet
    license: Supplier SDS (cited, not reproduced)
  questar-sds:
    title: Questar polyester film safety data sheet (Filmquest)
    id: Questar SDS, May 2019
    url: https://www.petfilm.com/wp-content/uploads/2021/05/Filmquest-Questar-SDS.pdf
    year: 2019
    kind: datasheet
    license: Supplier SDS (cited, not reproduced)
  pmc-uv-aging:
    title: Degradation of Mechanical Properties of A-PET Films after UV Aging, Polymers 2023, 15(20):4166
    id: PMC10610990, doi 10.3390/polym15204166
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC10610990/
    year: 2023
    kind: paper
    license: CC BY 4.0
  nasa-tn-mli-1971:
    title: NASA Technical Note on thermal analysis of customized multilayer insulation on an unshrouded liquid hydrogen tank
    id: NTRS 19710012082
    url: https://ntrs.nasa.gov/api/citations/19710012082/downloads/19710012082.pdf
    year: 1971
    kind: report
    license: NASA public document
  nasa-sail-2017:
    title: From Solar Sails to Laser Sails (Les Johnson, NASA Marshall), presentation
    id: NTRS 20170012350
    url: https://ntrs.nasa.gov/api/citations/20170012350/downloads/20170012350.pdf
    year: 2017
    kind: report
    license: NASA public document
  czce-pta:
    title: 'CZCE, PTA futures and options: overview of PTA'
    id: CZCE PTA overview (exchange document)
    url: https://english.czce.com.cn/en/rootfiles/2023/03/30/1681344050124601-1681344050137474.pdf
    year: 2023
    kind: report
    license: Exchange document (cited, not reproduced)
  czapp-pet-capacity:
    title: 'CZAPP explainer: Global PET Resin Capacity and Projects'
    id: CZAPP explainer
    url: https://www.czapp.com/explainers/global-pet-resin-capacity-and-projects/
    kind: web
    license: Industry web page (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-19'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 1
  caveats: 4
  note: Read by an AI assistant on 2026-10-19 from fetched DuPont Teijin, NASA, SDS and paper pages. PubChem was blocked by a reCAPTCHA. The Mylar glass transition and the UV values for Mylar were not found.
story:
  recipe:
    line: PET is a polyester made by reacting terephthalic acid with ethylene glycol. Each repeat unit (C10H8O4) joins one terephthalate group to one ethylene group, joined through ester links. Biaxially oriented film is made by stretching the molten polymer in two directions, which gives Mylar its strength.
    parts:
      - name: Carbon
        symbol: C
        atoms: 10
        role: Carbon backbone of the terephthalate ring and the ethylene linker.
      - name: Hydrogen
        symbol: H
        atoms: 8
        role: Four hydrogens on the benzene ring and four on the ethylene linker.
      - name: Oxygen
        symbol: O
        atoms: 4
        role: Two ester groups, each with a carbonyl and an ether oxygen.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified hazardous
      lead: The PET film SDSs read here do not classify the material under GHS. Hazards come from heating and from dust.
      points:
        - label: The film
          line: The Lumirror and Goodfellow SDSs classify PET as not classified. The Lumirror SDS says it is an article, so no label applies.
        - label: Dust and molten film
          line: Dust may be combustible, and molten film causes thermal burns on contact. Use ventilation where dust forms.
        - label: In a fire
          line: Heating to decomposition gives toxic fumes. The Questar SDS notes decomposition above 300 degC and a low level of acetaldehyde.
    - title: If it overheats
      lead: The Mylar bulletin gives the processing and service limits. Above them the film loses strength and becomes brittle.
      points:
        - label: Service limit
          line: The recommended maximum is 150 degC in air. Processing should stay below 200 degC.
        - label: Heating damage
          line: Heating at 220 degC for 30 min loses about 10 % of tensile strength, and the film shatters after 235 degC for under one minute.
    - title: Handling and storage
      points:
        - label: Water
          line: Mylar hydrolyzes when hot and humid. Dry it at 160 degC for 4 hours to bring the water below 0.1 %, especially in sealed units.
        - label: Space
          line: In LEO, MISSE 2 PET eroded at 3.01e-24 cm3/atom over about four years, so flight film needs a coating or a thicker stack.
  why: Polyethylene terephthalate (PET) is a polyester. Biaxially oriented film is sold as Mylar. It is light, strong and transparent. Its properties are stable in a dry vacuum, which makes it useful as the reflective base of multilayer insulation and as a solar sail. Its weakness is water and heat, because the ester links can hydrolyze, and atomic oxygen in low Earth orbit erodes it.
  uses:
    - where: Multilayer insulation
      line: NASA describes a typical MLI system as many highly reflective shields of aluminized polyester film separated by low-conductivity spacers. Its performance approaches the ideal when heat moves across the shields by pure radiation.
    - where: Solar sails
      line: LightSail's sail was aluminized 4.5 micron Mylar, with 32 square meters of area fully deployed. LightSail-A flew in 2015 and LightSail-B in 2016.
    - where: Electrical insulation
      line: DuPont Teijin Films says Type A Mylar is used for release films, office supplies, electrical insulation and laminations with other flexible materials.
  can_do:
    - label: Strength
      benchmark: ultimate_tensile_strength
      line: Mylar A at 50 micron has a tensile strength of 190 MPa in the machine direction and 210 MPa across it, with 140 % elongation at break. Film of this thickness is tough without plasticisers.
    - label: Heat
      benchmark: max_service_temp
      line: Mylar runs continuously up to 150 degC in air, and melts at 254 degC by DSC. Above 200 degC it begins to degrade.
    - label: Vacuum
      benchmark: atomic_oxygen_erosion_yield
      line: The MISSE 2 flight value is 3.01e-24 cm3/atom after 3.95 years in LEO, with a total mass loss of 0.19 % in the NASA outgassing test of Mylar Type A.
  compare: PET film has a strong, flexible, low-outgassing profile in vacuum (total mass loss 0.19 %, and no CVCM). Its atomic-oxygen erosion yield (3.01e-24 cm3/atom) is lower than the other polymers in the MISSE 2 table that were read for this profile. Its service limit of 150 degC is modest against high-temperature polyimides. The compare table sets PET against these benchmarks.
  compare_rows:
    - scope: material
      label: Density
      benchmark: density
    - scope: material
      label: Melting point
      benchmark: melting_point
    - scope: material
      label: Atomic oxygen erosion yield
      benchmark: atomic_oxygen_erosion_yield
  handling:
    - Dry the film before sealing it in a unit, using 160 degC for 4 hours (vacuum), to bring water to below 0.1 %.
    - Keep processing below 200 degC and do not heat the film above 150 degC in service.
    - Keep dust under control and wear protection when handling molten film. The film is not classified as hazardous.
  good_for:
    - Low-mass thermal blankets and solar sails. Mylar is the standard film for aluminized MLI and for the LightSail sails.
    - Electrical insulation and laminates, where tensile strength (190 MPa) and dielectric strength (7.7 kV minimum at 50 micron) matter.
  watch_out:
    - Hot, humid conditions, which cause hydrolysis and embrittlement.
    - Atomic oxygen in LEO. MISSE 2 PET eroded at 3.01e-24 cm3/atom over about four years.
    - UV. The A-PET film test shows large losses in plasticity after brief sunlight, although that film is not Mylar.
  verdict: PET (Mylar) is a light, tough and low-outgassing film. It is a sound choice for thermal blankets and sails in vacuum, provided it is kept dry, kept below 150 degC, and shielded from atomic oxygen and UV in LEO.