spore: profile
id: parylene-c
spore_version: 0.2
family: parylenes
name: Parylene C conformal coating
abbreviation: Parylene C
role: conformal dielectric coating for printed circuit boards and electronics
category: electronics
type: dielectrics-and-capacitors
summary: |
  Parylene C is a chlorinated poly(p-xylylene) conformal coating, deposited from vapour at room temperature in a vacuum chamber with no solvent and no cure cycle. SCS, the coating supplier, gives a dielectric constant of 3.15 at 60 Hz and 2.95 at 1 MHz, a dielectric strength of 5,600 V/mil, and a continuous service temperature of 80 °C in air. Goddard vacuum testing per ASTM E595 gave a total mass loss of 0.07 % and collected volatile condensable material of 0.0003 % for Parylene C.
best_for: Thin, pinhole-free dielectric coating on circuit boards in aerospace and defence electronics, where low outgassing and moisture barrier matter more than heat resistance
weakest_at: 'Heat: continuous service is 80 °C in air, against 350 °C for Parylene HT in the same SCS table, and UV stability is rated at 100 hours or less in accelerated testing'
identity:
  formula: 'Poly(chloro-p-xylylene): a chlorinated poly(p-xylylene) in which one aryl hydrogen of the repeat unit is replaced by chlorine'
  source: wikipedia-parylene
  where: Varieties, Chlorinated parylenes section (one hydrogen atom in the aryl ring replaced by chlorine; repeating-unit diagram only)
tags:
  environments: []
  stresses:
    - vacuum-and-outgassing
  applications:
    - electronics-and-chips
properties:
  - benchmark: dielectric_constant
    label: Dielectric constant at 60 Hz, Parylene C
    value: 3.15
    unit: '-'
    scope: material
    conditions:
      frequency: 60 Hz
      test_method: method 2 in the SCS table (ASTM D150 per footnote)
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dielectric Constant 60 Hz row, Parylene C column
  - benchmark: dielectric_constant
    label: Dielectric constant at 1 kHz, Parylene C
    value: 3.1
    unit: '-'
    scope: material
    conditions:
      frequency: 1 kHz
    method: Manufacturer table, SCS Parylene properties
    status: ground
    note: Wikipedia gives 3.2 at 1 kHz for parylene C (next entry). The two sources disagree; both are recorded.
    source: scs-aerospace
    where: SCS Parylene properties table, Dielectric Constant 1 KHz row, Parylene C column
  - benchmark: dielectric_constant
    label: Dielectric constant at 1 kHz, Parylene C (Wikipedia)
    value: 3.2
    unit: '-'
    scope: material
    conditions:
      frequency: 1 kHz
      basis: Alkyl-substituted parylenes section, comparison with parylene M
    method: Value stated in the Wikipedia article
    status: ground
    note: Disagrees with the 3.10 at 1 kHz that SCS prints; SCS is the manufacturer's own measurement table.
    source: wikipedia-parylene
    where: Varieties, Alkyl-substituted parylenes section
  - benchmark: dielectric_constant
    label: Dielectric constant at 1 MHz, Parylene C
    value: 2.95
    unit: '-'
    scope: material
    conditions:
      frequency: 1 MHz
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dielectric Constant 1 MHz row, Parylene C column
  - benchmark: dissipation_factor
    label: Dissipation factor at 60 Hz, Parylene C
    value: 0.02
    unit: '-'
    scope: material
    conditions:
      frequency: 60 Hz
      test_method: method 2 in the SCS table
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dissipation Factor 60 Hz row, Parylene C column
  - benchmark: dissipation_factor
    label: Dissipation factor at 1 kHz, Parylene C
    value: 0.019
    unit: '-'
    scope: material
    conditions:
      frequency: 1 kHz
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dissipation Factor 1 KHz row, Parylene C column
  - benchmark: dissipation_factor
    label: Dissipation factor at 1 MHz, Parylene C
    value: 0.013
    unit: '-'
    scope: material
    conditions:
      frequency: 1 MHz
      test_method: method 2 in the SCS table
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dissipation Factor 1 MHz row, Parylene C column
  - benchmark: dielectric_strength
    value: 5600
    unit: V/mil
    scope: material
    conditions:
      test_method: method 1 in the SCS table (ASTM D149 per footnote)
      thickness: not stated in the table
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Dielectric Strength V/mil row, Parylene C column
  - benchmark: water_vapor_transmission_rate
    label: Water vapour transmission rate, Parylene C
    value: 0.08
    unit: (g·mm)/(m2·day)
    scope: material
    conditions:
      method: ASTM F1249 at 90 % relative humidity and 37 °C (footnote 5, Parylene C only)
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Water Vapor Transmission Rate row, Parylene C column
  - benchmark: moisture_absorption
    value: 0.1
    bound: upper
    unit: '%'
    scope: material
    conditions:
      time: 24 hours
    method: Water absorption after 24 hours, table method 7; the SCS table prints the value as <0.1
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Water Absorption (% after 24 hours) row, Parylene C column
  - benchmark: max_service_temp
    label: Continuous service temperature, Parylene C
    value: 80
    unit: °C
    scope: material
    conditions:
      atmosphere: continuous exposure to air
      basis: SCS says this is based on Arrhenius extrapolation of test data for 10 years of survival
    method: Manufacturer table, SCS Parylene properties (method 8 covers TGA/FTIR, DSC and thermal endurance testing)
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Service Temperature Continuous row; Thermal section
  - benchmark: max_service_temp
    label: Short-term service temperature, Parylene C
    value: 100
    unit: °C
    scope: material
    conditions:
      duration: short-term; the duration is not stated in the table
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Service Temperature Short-Term row
  - benchmark: ultimate_tensile_strength
    value: 10000
    unit: psi
    scope: material
    conditions:
      test_method: ASTM D882 (footnote 10, Parylene C only)
    method: Manufacturer table, SCS Parylene properties
    status: ground
    source: scs-aerospace
    where: SCS Parylene properties table, Tensile Strength (psi) row, Parylene C column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Parylene C (Wikipedia industry table)
    value: 10000
    unit: psi
    scope: material
    conditions:
      basis: Industry specifications table
    method: Value stated in the Wikipedia article; the table flags the strength rows as needing clarification
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Tensile strength row, Parylene C column
  - benchmark: elongation
    value: 200
    unit: '%'
    scope: material
    conditions:
      basis: Industry specifications table, elongation to break
    method: Value stated in the Wikipedia article
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Elongation to break row, Parylene C column
  - benchmark: density
    value: 1.289
    unit: g/cm3
    scope: material
    conditions:
      temperature: not stated in the table
    method: Value stated in the Wikipedia article
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Density row, Parylene C column
  - benchmark: thermal_conductivity
    value: 0.084
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 25 °C
    method: Value stated in the Wikipedia article
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Thermal conductivity at 25 °C row, Parylene C column
  - benchmark: specific_heat
    value: 0.712
    unit: J/(g·K)
    scope: material
    conditions:
      temperature: 20 °C
    method: Value stated in the Wikipedia article
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Specific heat at 20 °C row, Parylene C column
  - benchmark: cte
    value: 35
    unit: ppm
    scope: material
    conditions:
      temperature: 25 °C
      basis: linear coefficient of thermal expansion, as printed
    method: Value stated in the Wikipedia article
    status: ground
    source: wikipedia-parylene
    where: Industry specifications table, Linear CTE at 25 °C row, Parylene C column
  - benchmark: elastic_modulus
    label: Young's modulus, Parylene C (industry table)
    value: 400000
    unit: psi
    scope: material
    conditions:
      basis: Industry specifications table
    method: Value stated in the Wikipedia article
    status: ground
    note: Disagrees with the 460 kpsi (3.17 GPa) for parylene C in the alkyl-substituted section (next entry). Both are recorded.
    source: wikipedia-parylene
    where: Industry specifications table, Young's modulus row, Parylene C column
  - benchmark: elastic_modulus
    label: Tensile modulus, Parylene C (alkyl-substituted section)
    value: 460
    unit: kpsi
    scope: material
    conditions:
      basis: alkyl-substituted parylenes section, which also gives 3.17 GPa
    method: Value stated in the Wikipedia article
    status: ground
    note: Disagrees with the 400,000 psi in the industry table (previous entry).
    source: wikipedia-parylene
    where: Varieties, Alkyl-substituted parylenes section
  - benchmark: melting_point
    label: Melting point, parylene C (industry table)
    value: 290
    unit: °C
    scope: material
    conditions:
      basis: Industry specifications table
    method: Value stated in the Wikipedia article
    status: ground
    note: Disagrees with the 270 °C given in the text (next entry). Both are recorded.
    source: wikipedia-parylene
    where: Industry specifications table, Melting point row, Parylene C column
  - benchmark: melting_point
    label: Melting point, parylene C (text)
    value: 270
    unit: °C
    scope: material
    conditions:
      basis: Transparency and crystallinity section
    method: Value stated in the Wikipedia article
    status: ground
    note: Disagrees with the 290 °C in the industry table (previous entry).
    source: wikipedia-parylene
    where: Transparency and crystallinity section
  - benchmark: total_mass_loss
    label: Total mass loss, Parylene C (ASTM E595)
    value: 0.07
    unit: '%'
    scope: material
    conditions:
      standard: ASTM E595
      test: vacuum stability testing at NASA Goddard Space Flight Center, as reported by SCS
    method: Manufacturer summary of NASA Goddard vacuum stability testing
    status: ground
    note: Benchmark name is not in the canonical list; snake_case used as the brief allows.
    source: scs-aerospace
    where: Vacuum stability section, Parylene C total mass loss
  - benchmark: collected_volatile_condensable_materials
    label: Collected volatile condensable materials (CVCM), Parylene C
    value: 0.0003
    unit: '%'
    scope: material
    conditions:
      standard: ASTM E595
      test: vacuum stability testing at NASA Goddard Space Flight Center, as reported by SCS
    method: Manufacturer summary of NASA Goddard vacuum stability testing
    status: ground
    note: Benchmark name is not in the canonical list; snake_case used as the brief allows.
    source: scs-aerospace
    where: Vacuum stability section, CVCM for Parylene C
corrosion:
  - environment: Salt-fog exposure (ASTM B117, 144 hours) on coated circuit boards
    headline: Parylene C boards showed results similar to Parylene HT, which showed no corrosion or salt deposits after 144 hours.
    effect: SCS says circuit boards coated with Parylene HT showed no corrosion or salt deposits after 144 hours of salt-fog exposure, and that boards coated with Parylene C and ParyFree gave similar results. Parylene C is therefore reported to protect against salt fog, but the figure is a comparison statement and not a separate Parylene C data table.
    rating: low
    conditions:
      standard: ASTM B117-(03)
      duration: 144 hours
      test: independent testing facility, as reported by SCS
    source: scs-aerospace
    where: Properties of SCS Parylene coatings, Barrier properties; Figure 1
  - environment: Accelerated UV exposure (ASTM G154)
    headline: Parylene C is rated for 100 hours or less in accelerated UV testing. Only Parylene HT is reported at 2,000 hours.
    effect: The SCS table gives UV stability of 100 hours or less for Parylene C, Parylene N and ParyFree, and 2,000 hours or more for Parylene HT under ASTM G154. Parylene C is therefore not a long-term UV-stable choice for exterior use, and the SCS UV statement for LED use refers to Parylene HT.
    rating: moderate
    conditions:
      standard: ASTM G154
      exposure: accelerated weathering test, duration stated in the table
    source: scs-aerospace
    where: SCS Parylene properties table, UV Stability row; UV stability section
  - environment: Organic solvents and acids or bases, up to 150 °C
    headline: Parylenes resist chemical attack and are insoluble in organic solvents up to 150 °C. The statement covers the Parylene family, not Parylene C alone.
    effect: SCS says the Parylenes resist chemical attack, are insoluble in all organic solvents up to 150 °C, and show no change to their physical and chemical properties after exposure to a host of acids and bases, including harsh aerospace fluids. SCS does not give a Parylene C test result or a chemical resistance table.
    rating: low
    conditions:
      basis: general statement for the Parylene family in the SCS brochure
      temperature: up to 150 °C for solvents
    source: scs-aerospace
    where: Properties of SCS Parylene coatings, Chemical resistance
  - environment: Continuous exposure to air at elevated temperature
    headline: SCS expects Parylene C to survive 10 years of continuous exposure to air at 80 °C, based on Arrhenius extrapolation.
    effect: SCS says Parylene N, ParyFree and Parylene C are expected to survive continuous exposure to air at 60 °C, 60 °C and 80 °C respectively for 10 years, based on Arrhenius extrapolations of test data. The brochure gives no figure for longer times or higher temperatures for Parylene C in air.
    rating: moderate
    conditions:
      atmosphere: air
      duration: 10 years, extrapolated
      basis: Arrhenius extrapolation of test data, as stated by SCS
    source: scs-aerospace
    where: Properties of SCS Parylene coatings, Thermal section
risks:
  hazards:
    - text: Parylene dimer DPX-C (the precursor, not the cured film) has a legacy safety data sheet dated February 22, 2005 (SCS, OSHA-format, no GHS codes). It labels the product 'MAY CAUSE SKIN AND EYE IRRITATION' and says the chief health hazard is irritation of contaminated eyes, skin and mucous membranes. Dust is the main route of overexposure. The sheet says no component is on the OSHA, NTP, IARC or CAL/OSHA cancer lists and that no component is a known skin or respiratory sensitiser.
      ghs: []
      source: dpx-c-msds
      where: Sections 3 (hazard identification), 11 (toxicological information) and 15 (regulatory information, ANSI caution label)
    - text: The DPX-C sheet says heating can release irritating vapours and toxic gases, including carbon monoxide, hydrogen chloride and carbon dioxide, and that dioxins and furans may form under certain conditions. It gives the flash point as not applicable and says the product can ignite only if exposed to extremely high temperatures.
      ghs: []
      source: dpx-c-msds
      where: Sections 3 (flammability hazards), 5 (flash point) and 10 (decomposition products)
    - text: The SCS dimer product note (2022) says that SCS dimer 'is non-toxic and non-hazardous and emits no volatile organic compounds during storage, processing, handling or deposition'. This conflicts with the irritation labelling on the DPX-C sheet above, so both are recorded side by side. Check the current SDS for the lot in use.
      ghs: []
      source: scs-dimer-note
      where: Left-hand column, paragraph beginning 'SCS dimer is non-toxic'; copyright line dated 2022
  failure_risks:
    - mode: Thermal ageing in air above the 80 °C continuous rating
      trigger: Continuous exposure to air at or above 80 °C
      consequence: The SCS table gives 80 °C as the continuous service temperature for Parylene C, and the brochure extrapolates 10-year survival at 80 °C in air. It gives no figure for longer times or higher temperatures for this grade.
      severity: moderate
      source: scs-aerospace
      where: SCS Parylene properties table, Service Temperature; Thermal section
    - mode: UV degradation in accelerated weathering
      trigger: Accelerated UV exposure under ASTM G154
      consequence: The SCS table rates Parylene C for 100 hours or less in the accelerated UV test. Only Parylene HT is reported at 2,000 hours.
      severity: moderate
      source: scs-aerospace
      where: SCS Parylene properties table, UV Stability row
  side_effects: []
  handling:
    - text: The SCS process applies Parylene in a room-temperature vacuum chamber by vapour deposition polymerisation. It uses no solvents, catalysts or plasticizers, and no elevated-temperature cure, so it adds no cure stresses.
      source: scs-aerospace
      where: The Parylene process section
    - text: The coater SOP says that Parylene vapour entering the vacuum pump will cause pump failure, so an exhaust cold trap condenses the remaining material and the operator must monitor temperature and flow and abort the run if needed. The SOP lists electric shock, thermal burns, cryogenic contact freeze and catastrophic loss of vacuum as general hazards of the equipment.
      source: scs-pds-sop
      where: Section 2.0 (Safety) and step 5.24 (cold trap and vacuum pump)
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Satellites and space-borne instrumentation
    example: SCS says Parylenes have a long history of protecting components used in satellites, space-borne instrumentation and vehicles, and that vacuum application leaves no hidden voids that could fail at altitude.
    source: scs-aerospace
    where: Protection for advanced applications, Space section
  - application: electronics-and-chips
    device: Circuit boards for aerospace and defence
    example: SCS states that Parylene coatings meet IPC-CC-830, are listed in the QPL for MIL-I-46058C, and that Parylene C is UL (QMJU2) recognised.
    source: scs-aerospace
    where: Environment-friendly coatings and processes, certifications list
  - application: electronics-and-chips
    device: Spacecraft and space hardware (outgassing qualification)
    example: NASA says Parylene C was the first Parylene variant it tested, and that its public outgassing database lists Parylene. The test follows the ASTM method and holds the chamber under high heat in vacuum.
    source: nasa-spinoff
    where: Article text on outgassing testing and the Parylene database
supply:
  - subject: Parylene C dimer (DPX-C, dichloro-di-p-xylylene)
    abundance: 'Not stated: no quantity or market share for the dimer was found in any source we hold.'
    producers:
      - country: United States
    critical_lists: []
    substitutes: []
    source: scs-dimer-note
    where: 'Ordering section: SCS world headquarters in Indianapolis, Indiana, and the statement ''SCS dimer is manufactured under cGMP guidelines exclusively for Specialty Coating Systems'' (SCS is the only producer named). The plant location and any share of world supply are not stated. The DPX-C sheet gives the same Indianapolis address (Section 1).'
  - subject: Feedstock for parylene dimer (synthesis route)
    abundance: 'Not stated: the patent names the salt feedstock and p-xylene solvent but gives no producer, country, share or yield.'
    producers: []
    critical_lists: []
    substitutes: []
    source: patent-dimer-synthesis
    where: 'Description and Example 1: the dimers are formed by Hofmann elimination of a p-methylbenzyltrimethylammonium salt, with p-xylene used as the solvent in the examples'
documents:
  - title: SCS Parylene coatings for aerospace and defence (Specialty Coating Systems, document 004 12/18)
    type: datasheet
    url: https://www.unmannedsystemstechnology.com/wp-content/uploads/2021/07/SCS-Aerospace-Defense-Coatings.pdf
    year: 2018
  - title: Parylene Dimer DPX-C Material Safety Data Sheet (Specialty Coating Systems)
    type: sds
    url: https://nrf.aux.eng.ufl.edu/_files/documents/174.pdf
    year: 2005
  - title: SCS Parylene Dimer product note (Specialty Coating Systems)
    type: datasheet
    url: https://nrf.aux.eng.ufl.edu/_files/documents/14393.pdf
    year: 2022
  - title: US patent 5110903 A, Process for the preparation of mixed parylene dimers free of alpha-halogens
    type: report
    url: https://patents.google.com/patent/US5110903
  - title: NASA Spinoff, Health and Medicine article on outgassing testing and Parylene
    type: report
    url: https://spinoff.nasa.gov/node/11056
  - title: Coating with Parylene, Fraunhofer IBMT product information sheet
    type: datasheet
    url: https://www.ibmt.fraunhofer.de/content/dam/ibmt/en/documents/PDFs/ibmt-product-information-sheets/ibmt-biomedical-microsystems/BMS_coating_with_parylene_en.pdf
  - title: SCS PDS 2010 Labcoter 2 Parylene Deposition System, Standard Operating Procedures (Revision 1)
    type: report
    url: https://nrf.aux.eng.ufl.edu/_files/documents/192.pdf
    year: 2015
gaps:
  - No GHS classification (H-codes) for Parylene C or its dimer was found. The DPX-C dimer sheet is a pre-GHS OSHA-format MSDS with no H-codes, and PubChem was blocked in this run, so risks.hazards records what the sheets say.
  - Producer shares and country production volumes for parylene dimer were not found. SCS is the only producer named in the sources, and its plant location is not stated.
  - The CAS number for the Parylene C polymer was not read on a fetched page. The dimer CAS 28804-46-8 (DPX-C) is printed in the SCS dimer note and the DPX-C MSDS.
  - Atomic weights and atom counts per repeat unit were not read on a fetched page, so the recipe lists elements and roles only.
  - Eight sources are now cited. The NASA outgassing database and the ASTM E595 test report were not opened; the NASA figures come from SCS and the NASA Spinoff article. No open paper was reached.
  - 'Dielectric constant at 1 kHz disagrees between sources: 3.10 from SCS and 3.2 from Wikipedia. Both are recorded.'
  - Melting point disagrees within the Wikipedia article (290 °C in the table, 270 °C in the text). Both are recorded.
  - Young's modulus disagrees within the Wikipedia article (400,000 psi in the table, 460 kpsi in another section). Both are recorded.
  - Dielectric strength for Parylene C is given only by SCS. The Wikipedia article gives no separate Parylene C figure.
  - Total mass loss, CVCM and water vapour transmission rate are not in the canonical property list; snake_case names are used.
  - The SCS brochure gives radiation resistance only as a qualitative statement (high resistance to gamma rays for the Parylene family), with no dose or retention figure, so it is not recorded as a value.
  - The SCS brochure gives a 220 °C continuous service expectation in vacuum or oxygen-free atmospheres for the Parylene family, without a Parylene C test result. It is not recorded as a value.
  - Chemical-resistance and solvent statements apply to the Parylene family and have no Parylene C test table; they are recorded as family-level statements.
  - No outgassing test was read beyond the NASA Goddard ASTM E595 figures reported by SCS; the original test report was not opened.
  - Conformal-coating thickness range and pinhole-free claim rest on SCS statements (a few hundred angstroms to several mils), with no independent measurement read.
  - Wikipedia values were read from a fetched summary; verify-values is the check that each one appears in the article text.
sources:
  scs-aerospace:
    title: SCS Parylene coatings for aerospace and defence (Specialty Coating Systems brochure, document 004 12/18)
    id: Specialty Coating Systems, document 004 12/18
    url: https://www.unmannedsystemstechnology.com/wp-content/uploads/2021/07/SCS-Aerospace-Defense-Coatings.pdf
    year: 2018
    kind: datasheet
    license: manufacturer brochure, linked not reproduced
  wikipedia-parylene:
    title: Parylene, Wikipedia
    id: Parylene article, Industry specifications, Varieties and History sections
    url: https://en.wikipedia.org/wiki/Parylene
    kind: web
    license: CC BY-SA 4.0, linked not reproduced
  dpx-c-msds:
    title: Parylene Dimer DPX-C Material Safety Data Sheet (Specialty Coating Systems, OSHA-format sheet)
    id: Parylene dimer DPX-C MSDS, date of revision February 22, 2005
    url: https://nrf.aux.eng.ufl.edu/_files/documents/174.pdf
    year: 2005
    kind: datasheet
    license: manufacturer safety data sheet, linked not reproduced
  scs-dimer-note:
    title: SCS Parylene Dimer product note (Specialty Coating Systems, DPX-N, DPX-C and DPX-D)
    id: Specialty Coating Systems, Parylene dimer note, document 039 05/22
    url: https://nrf.aux.eng.ufl.edu/_files/documents/14393.pdf
    year: 2022
    kind: datasheet
    license: manufacturer product note, linked not reproduced
  patent-dimer-synthesis:
    title: US5110903A, Process for the preparation of mixed parylene dimers free of alpha-halogens
    id: US patent US5110903 A
    url: https://patents.google.com/patent/US5110903
    kind: web
    license: patent document, linked not reproduced
  nasa-spinoff:
    title: NASA Spinoff, Health and Medicine article on outgassing testing and Parylene
    id: NASA Spinoff article, node 11056
    url: https://spinoff.nasa.gov/node/11056
    kind: web
    license: NASA public article, linked not reproduced
  fraunhofer-ibmt:
    title: Coating with Parylene, Fraunhofer IBMT Biomedical Microsystems product information sheet
    id: Fraunhofer IBMT, BMS coating with parylene (English product sheet)
    url: https://www.ibmt.fraunhofer.de/content/dam/ibmt/en/documents/PDFs/ibmt-product-information-sheets/ibmt-biomedical-microsystems/BMS_coating_with_parylene_en.pdf
    kind: datasheet
    license: institute product sheet, linked not reproduced
  scs-pds-sop:
    title: SCS PDS 2010 Labcoter 2 Parylene Deposition System, Standard Operating Procedures (Revision 1)
    id: SCS PDS 2010 Labcoter 2 SOP, Revision 1.0
    url: https://nrf.aux.eng.ufl.edu/_files/documents/192.pdf
    year: 2015
    kind: report
    license: university operating procedure, linked not reproduced
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 25
  unreachable: 0
  caveats: 4
  note: 'Written by an AI assistant on 2026-11-01 from the SCS aerospace brochure (text read from the PDF) and the Wikipedia Parylene article. Deepened 2026-11-01: added the DPX-C dimer MSDS, SCS dimer note, dimer synthesis patent, NASA Spinoff, Fraunhofer IBMT sheet and SCS SOP, and the hazards and supply sections. No open paper or NASA primary report was reached. Conflicts within and between sources are recorded side by side.'
story:
  recipe:
    line: Parylene C is made by vapour deposition polymerisation. The dimer dichloro-di-p-xylylene (DPX-C) is cracked thermally to the reactive monomer, a chlorinated p-xylylene. The monomer condenses and polymerises on the cool part inside a room-temperature vacuum chamber, so no solvent or catalyst is used. The Gorham process, credited to William F. Gorham at Union Carbide, is the route for the dimer cracking step.
    parts:
      - name: Carbon
        symbol: C
        role: Forms the aromatic ring and the two-carbon backbone of each repeat unit.
      - name: Hydrogen
        symbol: H
        role: Fills the ring and backbone positions. One aryl hydrogen per repeat unit is replaced by chlorine in Parylene C.
      - name: Chlorine
        symbol: Cl
        role: Replaces one aryl hydrogen per repeat unit. Wikipedia notes that the chlorine-aryl bond breaks at high cracking temperature, so the cracking temperature must be carefully controlled.
  risk_groups:
    - title: For people
      level: 0
      verdict: No safety data read for this profile
      lead: No safety data sheet or GHS classification for Parylene C or its dimer was read in this run, so this section records only the process facts from the SCS brochure.
      points:
        - label: Process
          line: The coating is applied in a room-temperature vacuum chamber with no solvent, catalyst or plasticiser, so no solvent vapour is released during coating according to the SCS process description.
    - title: If the coating fails
      lead: The failure routes in these sources are heat and UV, not corrosion of the coating itself.
      points:
        - label: Heat
          line: SCS rates Parylene C at 80 °C continuous service in air, and 100 °C short-term. Above this, the brochure gives no figure for Parylene C.
        - label: UV
          line: SCS rates Parylene C for 100 hours or less in accelerated UV testing under ASTM G154. Only Parylene HT is reported at 2,000 hours.
  why: Parylene C is a conformal dielectric coating. It is deposited as a thin film from vapour, so it reaches edges and cavities on a circuit board. SCS reports a dielectric constant of 3.15 at 60 Hz, a dielectric strength of 5,600 V/mil, a water vapour transmission rate of 0.08 (g·mm)/(m2·day), and a total mass loss of 0.07 % in ASTM E595 vacuum testing. The brochure says Parylene coatings meet IPC-CC-830 and are listed in the QPL for MIL-I-46058C. These values explain why it is used where moisture barrier, electrical insulation and low outgassing are needed together.
  uses:
    - where: Satellites and space instrumentation
      line: SCS states that Parylenes have a long history of protecting components used in satellites, space-borne instrumentation and vehicles. The brochure says that because the coating is applied in a vacuum, it leaves no hidden voids that could fail at altitude.
    - where: Aerospace and defence circuit boards
      line: SCS says Parylene coatings meet IPC-CC-830 and are listed in the QPL for MIL-I-46058C. The brochure also says that Parylene C is UL (QMJU2) recognised.
  can_do:
    - label: Electrical insulation
      benchmark: dielectric_constant
      value: 3.15 at 60 Hz
      line: SCS gives a dielectric constant of 3.15 at 60 Hz for Parylene C, falling to 2.95 at 1 MHz. Its dielectric strength is 5,600 V/mil. Wikipedia gives a 1 kHz value of 3.2, which disagrees slightly with SCS's 3.10 at 1 kHz.
    - label: Moisture barrier
      benchmark: water_vapor_transmission_rate
      value: 0.08 (g·mm)/(m2·day)
      line: SCS gives a water vapour transmission rate of 0.08 (g·mm)/(m2·day) for Parylene C under ASTM F1249 at 90 % relative humidity and 37 °C. Its water absorption is below 0.1 % after 24 hours.
    - label: Low outgassing
      benchmark: total_mass_loss
      value: 0.07 %
      line: In NASA Goddard vacuum testing per ASTM E595, SCS reports a total mass loss of 0.07 % and a collected volatile condensable material figure of 0.0003 % for Parylene C.
    - label: Heat limit
      benchmark: max_service_temp
      value: 80 °C continuous in air
      line: SCS gives a continuous service temperature of 80 °C in air for Parylene C, and 100 °C short-term. The same table gives 350 °C continuous for Parylene HT.
  compare: Within the SCS table, Parylene C has the lowest water vapour transmission rate of all the coatings listed, at 0.08 (g·mm)/(m2·day). Its dielectric strength of 5,600 V/mil is above the four non-parylene coatings in the same table, but below Parylene N and ParyFree. Its continuous service limit of 80 °C is below the acrylic, polyurethane, epoxy and silicone entries in SCS's own table and below Parylene HT (350 °C), and above only Parylene N and ParyFree (60 °C each). Parylene C is a strong barrier and insulator, but for heat it sits in the lower part of the group.
  compare_rows:
    - label: Dielectric constant at 1 MHz
      benchmark: dielectric_constant
    - label: Dielectric strength
      benchmark: dielectric_strength
    - label: Continuous service temperature
      benchmark: max_service_temp
  handling:
    - Coating is applied at room temperature in a vacuum, with no solvent, catalyst or cure cycle, according to SCS.
    - Keep the continuous service limit of 80 °C in mind for any part that runs hot in air.
    - Do not rely on Parylene C alone for long-term UV exposure. SCS rates it for 100 hours or less under ASTM G154.
  good_for:
    - 'Moisture barrier: 0.08 (g·mm)/(m2·day) water vapour transmission rate under ASTM F1249, per SCS.'
    - 'Electrical insulation: 5,600 V/mil dielectric strength and a 60 Hz dielectric constant of 3.15, per SCS.'
    - 'Low outgassing: 0.07 % total mass loss under ASTM E595 at NASA Goddard, per SCS.'
    - 'Conformal coating for tough electronics: Fraunhofer IBMT lists Parylene C as a pinhole-free conformal coating for electronics in tough environments.'
  watch_out:
    - 'Heat: 80 °C continuous service in air, against 350 °C for Parylene HT in the same SCS table.'
    - 'UV: 100 hours or less under ASTM G154 for Parylene C, against 2,000 hours for Parylene HT.'
    - 'Conflicting values: the 1 kHz dielectric constant (3.10 SCS, 3.2 Wikipedia), the melting point (290 and 270 °C) and Young''s modulus (400,000 psi and 460 kpsi) differ between sources.'
  verdict: Parylene C is the moisture-barrier choice among the coatings in the SCS table, with a strong dielectric strength and low outgassing in ASTM E595 testing. At 80 °C continuous in air it is limited for heat compared with epoxy, silicone and Parylene HT, so it suits moderate-temperature electronics better than hot ones.