Polymethylpentene PMP (TPX)

spore: profile
id: pmp-tpx
spore_version: 0.2
family: polyolefins
name: Polymethylpentene
abbreviation: PMP (TPX)
role: transparent low-density thermoplastic for moulding, films and release
category: polymers
type: polyolefins
summary: |
  Polymethylpentene (PMP), sold by Mitsui Chemicals as TPX, is a transparent semicrystalline polyolefin made from 4-methyl-1-pentene. The Mitsui TPX brochure prints a density of 833 kg/m3, a melt flow rate of 26 g/10 min (260 °C, 5 kgf) and a DSC melting point of 232 °C for the RT18 and RT31 grades. The same grade has a Vicat softening temperature of 168 °C, a heat distortion temperature of 127 °C at 0.45 MPa, a transmittance of 94 % and a refractive index of 1.462. Mitsui describes TPX as the lowest-density thermoplastic. A lab xenon weatherometer test in a 1990s patent gives a UV failure time of 333 h for unstabilised PMP and up to 1280 h with a hindered amine and phosphite package. No atomic oxygen, outgassing or radiation value for PMP was read in this run.
best_for: 'Transparent, low-density mouldings and release films where heat resistance and a low dielectric constant matter: RT18 at 833 kg/m3, 94 % transmittance and a dielectric constant of 2.11 at 1 MHz'
weakest_at: 'Impact and long exposure: an Izod impact of 24 J/m for RT18, a heat distortion temperature of 127 °C at 0.45 MPa, and Mitsui''s warning that long outdoor use can cause colour change and quality loss'
identity:
  formula: (C6H12)n, poly(4-methyl-1-pentene); repeat unit -[CH2-CH(CH2CH(CH3)2)]-, also named poly[1-(2-methylpropyl)ethylene]
  cas: 25068-26-2
  source: wikipedia-pmp
  where: Chembox infobox (Chemical formula, IUPAC name and CAS number 25068-26-2); Production section for 4-methyl-1-pentene as the monomer
tags:
  environments: []
  stresses:
    - uv
    - extreme-heat
  applications:
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, TPX RT18 and RT31 grades
    value: 833
    unit: kg/m3
    scope: material
    conditions:
      grade: RT18, RT31 (first grade column of the Mitsui table; RT31 is a low-odour grade)
      temperature: not printed in the table
    method: Density gradient method (MCI method), as printed in the Methodology column
    status: ground
    source: mitsui-tpx-brochure
    where: Physical Properties table, Basic Properties, Density row, RT18 and RT31 column
  - benchmark: melt_flow_rate
    label: Melt flow rate, TPX RT18
    value: 26
    unit: g/10min
    scope: material
    conditions:
      temperature: 260 °C
      load: 5 kgf
      grade: RT18 (RT31 in the same column is 21 g/10min)
    method: MCI method, as printed in the Methodology column
    status: ground
    source: mitsui-tpx-brochure
    where: Physical Properties table, Basic Properties, MFR row, RT18 cell
  - benchmark: melting_point
    label: Melting point, TPX RT18 (DSC)
    value: 232
    unit: °C
    scope: material
    conditions:
      grade: RT18, RT31 column
      method_as_printed: ASTM D3418, DSC method
    method: Printed in the Mitsui grade table as DSC method, ASTM D3418
    status: ground
    source: mitsui-tpx-brochure
    where: Physical Properties table, Basic Properties, Melting Point row, RT18 cell (449.6 °F)
  - benchmark: melting_point
    label: Melting range, TPX (all grades)
    value: 220
    value_high: 240
    unit: °C
    scope: material
    conditions:
      basis: range stated for TPX in general, not for one grade
    method: Range stated on the Mitsui TPX product page, Heat resistance section
    status: ground
    source: mitsui-tpx-eu
    where: Heat resistance section (high melting point in the range 220 °C to 240 °C)
  - benchmark: water_absorption
    label: Water absorption, TPX RT18
    value: 0.01
    bound: upper
    unit: '%'
    scope: material
    conditions:
      grade: RT18, RT31 column
      test: ASTM D570, as printed
    method: Printed as less than 0.01 % in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Physical Properties table, Basic Properties, Water Absorption row, RT18 cell (printed as <0.01)
  - benchmark: vicat_softening_temperature
    label: Vicat softening temperature, TPX RT18
    value: 168
    unit: °C
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick, 2 pieces
      heat_speed: 50 °C per hour
      load: 10 N
      test: ASTM D1525
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Thermal Properties table, Vicat Softening Temperature row, RT18 cell (334.4 °F)
  - benchmark: heat_deflection_temperature
    label: Heat distortion temperature, TPX RT18
    value: 127
    unit: °C
    scope: material
    conditions:
      specimen: injection moulded, 1/4 inch thick
      heat_speed: 120 °C per hour
      stress: 0.45 MPa
      test: ASTM D648
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Thermal Properties table, Heat Distortion Temperature row, RT18 cell (260.6 °F)
  - benchmark: cte
    label: Coefficient of linear expansion, TPX RT18
    value: 0.000117
    unit: cm/cm°C
    scope: material
    conditions:
      measured_range: '-10 °C to 160 °C'
      applied_force: 3 g
      atmosphere: nitrogen flow 100 mL/min
      method_as_printed: TMA method
    method: Printed as 1.17 x 10-4 cm/cm°C in the Mitsui grade table; copied as 1.17e-4
    status: ground
    source: mitsui-tpx-brochure
    where: Thermal Properties table, Coefficient of Linear Expansion row, RT18 cell
  - benchmark: yield_strength
    label: Yield stress, TPX RT18
    value: 30
    unit: MPa
    scope: material
    conditions:
      specimen: injection moulded, ASTM-4 bar
      cross_head_speed: 50 mm/min
      chuck_distance: 65 mm
      temperature: 23 °C
      test: ASTM D638
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Yield Stress row, RT18 cell (4350 psi)
  - benchmark: ultimate_tensile_strength
    label: Stress at break (fractured stress), TPX RT18
    value: 25
    unit: MPa
    scope: material
    conditions:
      specimen: injection moulded, ASTM-4 bar
      cross_head_speed: 50 mm/min
      temperature: 23 °C
      test: ASTM D638
    method: Printed as Fractured Stress in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Fractured Stress row, RT18 cell (3625 psi)
  - benchmark: elongation
    label: Fractured strain (elongation at break), TPX RT18
    value: 22
    unit: '%'
    scope: material
    conditions:
      specimen: injection moulded, ASTM-4 bar
      temperature: 23 °C
      test: ASTM D638
    method: Printed as Fractured Strain in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Fractured Strain row, RT18 cell
  - benchmark: elastic_modulus
    label: Tensile modulus, TPX RT18
    value: 1900
    unit: MPa
    scope: material
    conditions:
      specimen: injection moulded
      chuck_distance: 65 mm
      cross_head_speed: 50 mm/min
      temperature: 23 °C
      test: ASTM D638
    method: Printed in the Mitsui grade table (275500 psi)
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Tensile Modulus row, RT18 cell
  - benchmark: flexural_modulus
    label: Flexural modulus, TPX RT18
    value: 1450
    unit: MPa
    scope: material
    conditions:
      specimen: injection moulded, 3.2 mm thick
      cross_head_speed: 1.3 mm/min
      span_length: 51 mm
      temperature: 23 °C
      test: ASTM D790
    method: Printed in the Mitsui grade table (210250 psi)
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Flexural Modulus row, RT18 cell
  - benchmark: flexural_strength
    label: Flexural strength, TPX RT18
    value: 36
    unit: MPa
    scope: material
    conditions:
      specimen: injection moulded, 3.2 mm thick
      cross_head_speed: 1.3 mm/min
      span_length: 51 mm
      temperature: 23 °C
      test: ASTM D790
    method: Printed in the Mitsui grade table (5220 psi)
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Flexural Strength row, RT18 cell
  - benchmark: izod_impact
    label: Izod impact strength, machined notch, TPX RT18
    value: 24
    unit: J/m
    scope: material
    conditions:
      specimen: injection moulded, machined notch
      temperature: 23 °C
      test: ASTM D256
    method: Printed in the Mitsui grade table (0.45 ft-lbs/in)
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Izod Impact Strength (machined notch) row, RT18 cell
  - benchmark: rockwell_hardness
    label: Rockwell hardness, R scale, TPX RT18
    value: 83
    unit: R scale
    scope: material
    conditions:
      specimen: injection moulded
      temperature: 23 °C
      test: ASTM D785
    method: Printed in the Mitsui grade table; rockwell_hardness is not a canonical property name
    status: ground
    source: mitsui-tpx-brochure
    where: Mechanical Properties table, Rockwell Hardness row, RT18 cell
  - benchmark: haze
    label: Haze, TPX RT18
    value: 0.7
    unit: '%'
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick
      illuminant: C
      test: ASTM D1003
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Optical Properties table, Haze row, RT18 cell
  - benchmark: transmittance
    label: Light transmittance, TPX RT18
    value: 94
    unit: '%'
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick
      illuminant: C
      test: ASTM D1003
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Optical Properties table, Transmittance row, RT18 cell
  - benchmark: refractive_index
    label: Refractive index, TPX RT18
    value: 1.462
    unit: '-'
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick
      wavelength: 589 nm
      test: ASTM D542
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Optical Properties table, Refractive Index row, RT18 cell
  - benchmark: dielectric_constant
    label: Relative dielectric constant, TPX RT18 (1 MHz)
    value: 2.11
    unit: '-'
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick
      frequency: 1 MHz
      test: ASTM D150
    method: Printed in the Mitsui grade table
    status: ground
    source: mitsui-tpx-brochure
    where: Electrical Properties table, Relative Dielectric Constant row, RT18 cell
  - benchmark: dielectric_strength
    label: Dielectric breakdown, TPX RT18
    value: 32
    unit: kV/mm
    scope: material
    conditions:
      specimen: injection moulded, 2 mm thick
      test: ASTM D149
    method: Printed in the Mitsui grade table (812 V/mil)
    status: ground
    source: mitsui-tpx-brochure
    where: Electrical Properties table, Dielectric Breakdown row, RT18 cell
corrosion:
  - environment: UV in a xenon weatherometer, laboratory test on moulded sheet
    headline: In a xenon weatherometer, unstabilised PMP failed after 333 h; a hindered amine and phosphite package reached 1280 h.
    effect: 'Patent EP0553498 gives time to failure in hours (break on flexing a strip to 90 degrees). No additive: 333 h. Zinc stearate alone: 528 h. The best hindered amine and phosphite combinations: 1280 h. The patent states the combination gives UV ageing times significantly longer than either component alone. No retention value of a property is given.'
    rating: moderate
    conditions:
      basis: Atlas Xenon Weatherometer at 75 °F; 20 mil compression-moulded sheet; failure defined as a break on flexing to 90 degrees
      material: polymethylpentene with the additive package named in the patent, not a service test
    source: epo-ep0553498
    where: Paragraphs 0035, 0049 and 0050; Example 7, Table 7 (No Add. 333; UV aging HRS column)
  - environment: Long-term outdoor exposure
    headline: Mitsui advises against long outdoor use because TPX may change colour and lose quality.
    effect: The Mitsui brochure says to avoid outdoor use of TPX for a long period as it may cause colour change or quality deterioration. It prints no retention figure and no test condition.
    rating: moderate
    conditions:
      basis: manufacturer precaution; no test conditions printed
    source: mitsui-tpx-brochure
    where: Precautions, item 1 (General Precautions)
  - environment: Humidity and boiling water
    headline: Very low water absorption keeps dimensions stable in humid air, and PMP resists hydrolysis in boiling water.
    effect: Water absorption is printed as less than 0.01 % (ASTM D570) for the RT18 grade. Mitsui says TPX dimensions remain stable in humid conditions, it resists hydrolysis in boiling water, and it is suitable for steam sterilisation.
    rating: low
    conditions:
      basis: water absorption from the grade table (ASTM D570); humidity and steam statements from the product page
    source: mitsui-tpx-eu
    where: Water absorption and sterilisation statements on the product page; RT18 cell of the brochure table
  - environment: Acids, alkalis and alcohols
    headline: Mitsui rates TPX chemical resistance above polycarbonate and acrylic, especially against acids, alkalis and alcohols.
    effect: The product page says TPX has superior chemical resistance compared with polycarbonate and acrylic polymers, with excellent resistance to acids, alkalis and alcohols, from stable carbon-carbon bonds. No immersion test, solvent table or concentration is printed on that page.
    rating: low
    conditions:
      basis: qualitative manufacturer statement; no test condition given
    source: mitsui-tpx-eu
    where: Chemical resistance statement on the product page
  - environment: Heat
    headline: PMP melts at 220 to 240 °C and softens at 168 °C, but no heat-ageing time or temperature was read.
    effect: The melting range (220 to 240 °C) and the Vicat and heat distortion values are short-term, single-test values. The product page warns that heat distortion temperature is almost the same as polypropylene's, so high-stress use needs careful design. No oven ageing data was read.
    rating: low
    conditions:
      basis: short-term test values only; no ageing time or temperature printed
    source: mitsui-tpx-eu
    where: Heat resistance section of the product page; Vicat and heat distortion rows of the brochure table
risks:
  hazards:
    - text: 'Mitsui SDS for TPX pellet (SDS 51054A, revised 02/25/2015): not classified according to GHS criteria, and no hazard statements apply. The SDS still advises handling precautions.'
      ghs: []
      source: boedeker-tpx-sds
      where: Section 2, Classification
    - text: Powdered TPX may form an explosive dust-air mixture, according to the SDS.
      ghs: []
      source: boedeker-tpx-sds
      where: Section 2, Other hazards
  failure_risks:
    - mode: Colour change and quality loss from long outdoor use
      trigger: Long-term outdoor exposure of PMP parts or films
      consequence: Mitsui says colour change or quality deterioration may follow. The UV patent test gives failure at 333 h for unstabilised PMP in a xenon weatherometer.
      severity: moderate
      source: mitsui-tpx-brochure
      where: Precautions, item 1; Table 7 of patent EP0553498 for the lab figure
    - mode: Distortion under load near the upper service range
      trigger: High-stress use at elevated temperature
      consequence: Heat distortion temperature is 127 °C at 0.45 MPa for RT18, and Mitsui says it is almost the same as polypropylene's, so load-bearing parts need careful design.
      severity: moderate
      source: mitsui-tpx-eu
      where: Heat resistance section
  side_effects: []
  handling:
    - text: Molten polymer can cause a thermal burn. Cool the skin at once with cold water and do not peel polymer off; get medical attention for the burn.
      source: boedeker-tpx-sds
      where: Section 4, skin contact
    - text: Store away from fire, direct sunlight, water wetting and abrupt temperature change.
      source: mitsui-tpx-brochure
      where: Precautions, item 1
    - text: Medical-related and food-contact uses should be discussed with Mitsui before use.
      source: mitsui-tpx-brochure
      where: Precautions, item 2
  mitigations: []
uses:
  - application: optics-and-cameras
    device: Optical analysis cell
    example: TPX is used in optical analysis cells because its UV transmittance is higher than glass and other transparent polymers.
    source: mitsui-tpx-eu
    where: Optical properties section of the product page
  - application: electronics-and-chips
    device: Release film for flexible printed circuits (FPC)
    example: TPX is used as a release film in flexible printed circuits, where its non-polar structure gives a low dielectric constant and good releasability.
    source: mitsui-tpx-eu
    where: Applications section of the product page (release films for flexible printed circuits)
supply:
  - subject: Polymethylpentene (TPX) production
    demand: []
    routes: Made from the monomer 4-methyl-1-pentene by Ziegler-Natta type catalysis. Commercial grades are usually copolymers.
    producers: []
    critical_lists: []
    substitutes: []
    abundance: Mitsui says TPX is exclusively manufactured by Mitsui Chemicals. No tonnage or capacity figure was read.
    source: mitsui-tpx-eu
    where: Product page introduction (exclusively manufactured by Mitsui Chemicals); Wikipedia Production section for the catalyst route
documents:
  - title: TPX brochure, Mitsui Chemicals, Physical Properties and grade table (tpx_e.pdf, 2018)
    type: datasheet
    url: https://ap.mitsuichemicals.com/sites/default/files/media/document/2018/tpx_e.pdf
    year: 2018
  - title: TPX (PMP) product page, Mitsui Chemicals Europe
    type: datasheet
    url: https://eu.mitsuichemicals.com/en/service/product/tpx/index.htm
  - title: Safety Data Sheet, TPX Pellet, SDS 51054A, Mitsui Chemicals America (revised 02/25/2015), via Boedeker Plastics
    type: sds
    url: https://www.boedeker.com/Portals/0/Safety Data Sheets SDS/TPX-PMP-Safety-Data-Sheet-Boedeker-Plastics.pdf
    year: 2015
  - title: European patent application EP0553498, additive composition for polymers of 4-methyl-1-pentene (Example 7, Table 7)
    type: report
    url: https://data.epo.org/publication-server/rest/v1.2/patents/EP0553498NWA2/document.html
  - title: NIST Atomic Weights and Isotopic Compositions, carbon and hydrogen
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html
gaps:
  - No atomic oxygen erosion yield or outgassing (total mass loss, CVCM) for PMP was read in this run. A NASA 1997 report found by search returned HTML rather than a PDF, and the NASA outgassing database was not opened.
  - No radiation, thermal-cycling or UV-retention value for PMP was read. The only UV data is a patent weatherometer test on additive packages, giving times to failure, not property retention.
  - Heat ageing (oven time and temperature, retention of properties) was not found on any fetched page.
  - The Mitsui brochure chemical-resistance table (solvent ratings) is on a page not opened. Only the qualitative acid, alkali and alcohol statements were read.
  - The PubChem record for PMP could not be opened (captcha), so no PubChem GHS statement is recorded. Hazards rest on the 2015 Mitsui SDS for TPX pellet, as distributed by Boedeker; a current Mitsui-issued SDS was not found.
  - Rockwell hardness is recorded as rockwell_hardness, which is not a canonical property name in property-canon.yaml.
  - Brochure table values are representative values, as the table states, not specified values. Grade columns were read from the rendered table image.
  - 'Refractive index: Wikipedia gives 1.460 +/- 0.005 with no unit. Only the Mitsui RT18 value of 1.462 is recorded.'
  - 'Melting point: Wikipedia gives 240 °C (infobox) and about 235 °C (text). Those values are not recorded; the Mitsui range (220 to 240 °C) and DSC value (232 °C) are used.'
  - Dissipation factor below 0.0003 at 1 MHz is printed on a brochure comparison page, which was not read as a table, so it is not recorded.
  - Volume resistivity (ASTM D257, RT18) is printed as greater than 10^16 Ω·cm in the Mitsui table. It was removed because the printed form is not a plain number for the value check.
  - 'Supply: no production volume, capacity or producer share for PMP was read, and no second manufacturer was checked. The 4-methyl-1-pentene monomer market and its hazard data (NITE entry seen in search, CAS 691-37-2) were not read.'
sources:
  mitsui-tpx-brochure:
    title: TPX brochure, Physical Properties and grade table (RT18, RT31, DX845, DX231, DX820, MX004, MX002, MX0020, DX310, MBZ230 (A), DX560M)
    id: Mitsui Chemicals TPX brochure, tpx_e.pdf
    url: https://ap.mitsuichemicals.com/sites/default/files/media/document/2018/tpx_e.pdf
    year: 2018
    kind: datasheet
    license: manufacturer brochure, linked not reproduced
  mitsui-tpx-eu:
    title: TPX (PMP), Mitsui Chemicals Europe product page
    id: Product page, Basic Properties, Heat resistance, Chemical resistance and Applications sections
    url: https://eu.mitsuichemicals.com/en/service/product/tpx/index.htm
    kind: datasheet
    license: manufacturer web page, linked not reproduced
  boedeker-tpx-sds:
    title: Safety Data Sheet, TPX Pellet, SDS 51054A (Mitsui Chemicals America), via Boedeker Plastics
    id: SDS 51054A, revised 02/25/2015
    url: https://www.boedeker.com/Portals/0/Safety Data Sheets SDS/TPX-PMP-Safety-Data-Sheet-Boedeker-Plastics.pdf
    year: 2015
    kind: datasheet
    license: supplier SDS, linked not reproduced
  epo-ep0553498:
    title: European patent application EP0553498, additive composition for polymers of 4-methyl-1-pentene
    id: EP0553498 (Example 7, Table 7, UV aging)
    url: https://data.epo.org/publication-server/rest/v1.2/patents/EP0553498NWA2/document.html
    kind: report
    license: patent document, linked not reproduced
  wikipedia-pmp:
    title: Polymethylpentene, Wikipedia
    id: Polymethylpentene article, infobox, Production and Applications sections
    url: https://en.wikipedia.org/wiki/Polymethylpentene
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
  nist-atomic-weights:
    title: NIST Atomic Weights and Isotopic Compositions for All Elements (C and H rows)
    id: 'NIST standard atomic weight table: C [12.0096, 12.0116]; H [1.007 84, 1.008 11]'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html
    kind: database
    license: US government data
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 3
  caveats: 4
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages named in each entry. Mitsui grade values were read from the rendered brochure table, RT18 and RT31 column. Unreachable: PubChem record (captcha), Goodfellow TPX page (404), NASA 1997 report (HTML, not PDF). Caveats: Mitsui values are representative, not specified; the UV figures are times to failure from a patent lab test; the hazard data are from a 2015 SDS distributed by Boedeker; the melting point range and the DSC value are different measurements.'
story:
  recipe:
    line: Polymethylpentene is a linear isotactic polyolefin made by Ziegler-Natta type polymerisation of the monomer 4-methyl-1-pentene, CH2=CH-CH2-CH(CH3)2. Commercial grades are usually copolymers. The repeat unit is -[CH2-CH(CH2CH(CH3)2)]-, with 6 carbons and 12 hydrogens.
    parts:
      - name: Carbon
        symbol: C
        role: 'Six carbons per repeat unit: two in the chain backbone, and four in the isobutyl side group.'
        share_note: atomic_weight [12.0096, 12.0116]
      - name: Hydrogen
        symbol: H
        role: Twelve hydrogens per repeat unit, filling the backbone and the isobutyl side group.
        share_note: atomic_weight [1.007 84, 1.008 11]
  risk_groups:
    - title: For people
      lead: The 2015 Mitsui SDS for TPX pellet, as distributed by Boedeker, is not classified under GHS. Molten polymer and fine dust are the handling risks it names.
      level: 0
      verdict: Not classified in the SDS read
      points:
        - label: Classification
          line: The SDS states that no hazard statement applies, though it still advises handling precautions.
        - label: Dust
          line: The SDS says powdered TPX may form an explosive dust-air mixture.
        - label: Molten polymer
          line: The SDS calls for cold water on the skin and no peeling of the polymer, with medical attention for the thermal burn.
    - title: If it fails
      lead: The failure routes in these sources are outdoor UV exposure and distortion under load.
      points:
        - label: Outdoor UV
          line: Mitsui warns that long outdoor use may cause colour change and quality loss. In a lab xenon weatherometer, unstabilised PMP failed at 333 h.
        - label: Heat under load
          line: The heat distortion temperature is 127 °C at 0.45 MPa for RT18, which Mitsui says is almost the same as polypropylene.
  why: Polymethylpentene (PMP, TPX) is a transparent polyolefin with a density of 833 kg/m3 for the RT18 grade, which Mitsui describes as the lowest of any thermoplastic. It melts at 220 to 240 °C, has a Vicat softening temperature of 168 °C and a refractive index of 1.462, and it has a low dielectric constant of 2.11 at 1 MHz. Those properties make it a candidate for light optical parts, cells, and release films, and Mitsui presents it as an alternative where PTFE is restricted.
  uses:
    - where: Optical analysis cells
      line: Mitsui says TPX is used in optical analysis cells because its UV transmittance is higher than glass and other transparent polymers. Wikipedia also names CO2 laser output windows, which this profile does not verify.
    - where: Release films for flexible printed circuits
      line: Mitsui's product page lists TPX release films for flexible printed circuits, and says it is a PTFE alternative with similar dielectric and releasability properties.
  can_do:
    - label: Light
      value: 833 kg/m3
      benchmark: density
      line: The RT18 grade has a density of 833 kg/m3. Mitsui says TPX has the lowest density of any thermoplastic.
    - label: Heat
      value: Melts at 220 to 240 °C
      benchmark: melting_point
      line: Mitsui gives a melting range of 220 to 240 °C. For RT18, the DSC melting point is 232 °C and the heat distortion temperature at 0.45 MPa is 127 °C.
    - label: Low dielectric constant
      value: 2.11 at 1 MHz
      benchmark: dielectric_constant
      line: The RT18 grade has a relative dielectric constant of 2.11 at 1 MHz and a dielectric breakdown of 32 kV/mm, printed in the Mitsui grade table.
  compare: PMP is a light, transparent polyolefin, with a density close to polypropylene but lower than most thermoplastics, according to Mitsui. Its heat distortion temperature (127 °C at 0.45 MPa for RT18) is comparable to polypropylene's, so PMP gains its heat margin mainly from its higher melting range. The table compares PMP with other polymers in the collection on the same benchmarks; the values come from different grades and test conditions, so they are examples, not a ranking.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Heat distortion temperature
      benchmark: heat_deflection_temperature
    - label: Dielectric constant
      benchmark: dielectric_constant
  handling:
    - Specify the grade, since the Mitsui grades differ in melt flow, heat distortion and impact (for example RT18 against MX002).
    - Check the current Mitsui SDS before handling, since the SDS read is from 2015.
    - Keep molten polymer away from skin, and keep powder dust out of the air.
    - Treat the Mitsui values as representative, as the table states.
  good_for:
    - 'Transparent low-density parts: RT18 at 833 kg/m3 with 94 % transmittance and 0.7 % haze.'
    - 'Low dielectric constant: 2.11 at 1 MHz, close to fluoropolymer values as Mitsui states.'
    - 'Release films: Mitsui lists TPX release films for flexible printed circuits and release paper for synthetic leather.'
  watch_out:
    - 'Impact: an Izod impact of 24 J/m (machined notch) for RT18.'
    - Long outdoor exposure can cause colour change and quality loss; unstabilised PMP failed at 333 h in a lab xenon weatherometer.
    - Heat distortion of 127 °C at 0.45 MPa for RT18, and 80 °C for the DX310 low-modulus grade, so the heat margin depends on grade.
    - No atomic oxygen, outgassing or radiation value for PMP was read, so its space performance is not established here.
  verdict: PMP (TPX) is a light, transparent polyolefin with a density of 833 kg/m3 and a low dielectric constant of 2.11 at 1 MHz for RT18, and a melting range of 220 to 240 °C. Its UV resistance is weak without additives, with 333 h to failure in a lab test. This profile has no space test data for PMP, and its impact strength is low.