Chlorosulfonated polyethylene (CSM, Hypalon) CSM

spore: profile
id: csm-hypalon
spore_version: 0.2
family: chlorosulfonated-polyethylene
name: Chlorosulfonated polyethylene (CSM, Hypalon)
abbreviation: CSM
role: elastomer
category: seals-adhesives
type: elastomers-and-o-rings
summary: |
  Chlorosulfonated polyethylene (CSM) is a synthetic rubber made by treating polyethylene with chlorine and sulfur dioxide under UV light. DuPont sold it as Hypalon. One compound datasheet from Angst+Pfister gives a density of 1.48 g/cm³, a tensile strength of 8.00 N/mm² and an elongation at break of 300 %, with an operating range from -30 °C to 120 °C. NASA's ground outgassing table records a Hypalon cable insulation with 9.13 % total mass loss, far above the screening limits that the report describes.
best_for: Weather, ozone and chemical resistance in flexible rubber parts (family guide and compound datasheets rate ozone, sunlight and weather resistance as Excellent)
weakest_at: 'Vacuum outgassing: the Hypalon cable insulation in NASA''s table lost 9.13 % of its mass, and the sources found no grade that passes the screen in that row'
identity:
  formula: Polyethylene chain carrying chlorine atoms and chlorosulfonyl (-SO2Cl) groups; repeat unit -[CH2-CH(Cl)]x-[CH2-CH(SO2Cl)]y- (Wikipedia)
  source: wiki-hypalon
  where: Chemical structure and Synthesis sections
  designations:
    - system: Trade name
      code: Hypalon
      source: wiki-hypalon
      where: Lead section, first sentence
tags:
  stresses:
    - vacuum-and-outgassing
  applications:
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, CSM compound 70.98-01
    value: 1.48
    unit: g/cm³
    scope: material
    conditions:
      compound: CSM 70.98-01, black (Angst+Pfister)
      test_method: not named in the datasheet
      temperature: not stated
    method: Value printed in a compound datasheet, which says values are not guaranteed property values
    status: ground
    source: angst-csm70
    where: Mechanical properties block, row Density
  - benchmark: hardness_shore_a
    label: Hardness, CSM compound 70.98-01
    value: 70
    unit: Shore A
    scope: material
    conditions:
      compound: CSM 70.98-01 (Angst+Pfister)
      tolerance: printed as plus or minus 5
      test_standard: DIN ISO 7619-1
    method: Nominal value printed in a compound datasheet
    status: ground
    source: angst-csm70
    where: Mechanical properties block, row Hardness nominal
  - benchmark: hardness_shore_a
    label: Hardness, CSM75 black compound
    value: 75
    unit: ShA
    scope: material
    conditions:
      compound: CSM75 black (Polymax)
      value_type: typical value (column header)
    method: Typical value printed in a supplier datasheet
    status: ground
    source: polymax-csm75
    where: Physical property table, row Hardness, column Typical Values
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, CSM compound 70.98-01
    value: 8
    unit: N/mm²
    scope: material
    conditions:
      compound: CSM 70.98-01 (Angst+Pfister)
      test_standard: DIN 53504
      temperature: not stated
    method: Value printed in a compound datasheet
    status: ground
    source: angst-csm70
    where: Mechanical properties block, row Tensile strength
  - benchmark: elongation
    label: Elongation at break, CSM compound 70.98-01
    value: 300
    unit: '%'
    scope: material
    conditions:
      compound: CSM 70.98-01 (Angst+Pfister)
      test_standard: DIN 53504
    method: Value printed in a compound datasheet
    status: ground
    source: angst-csm70
    where: Mechanical properties block, row Elongation at break
  - benchmark: min_service_temp
    label: Minimum operating temperature, CSM compound 70.98-01
    value: -30
    unit: °C
    scope: material
    conditions:
      compound: CSM 70.98-01 (Angst+Pfister)
      basis: printed as approximate, dependent on the application
    method: Value printed in a compound datasheet
    status: ground
    source: angst-csm70
    where: Thermal properties block, row Operating temperature min.
  - benchmark: max_service_temp
    label: Maximum operating temperature, CSM compound 70.98-01
    value: 120
    unit: °C
    scope: material
    conditions:
      compound: CSM 70.98-01 (Angst+Pfister)
      basis: printed as approximate, dependent on the application
    method: Value printed in a compound datasheet
    status: ground
    source: angst-csm70
    where: Thermal properties block, row Operating temperature max.
  - benchmark: min_service_temp
    label: Low end of operating temperature range, CSM75
    value: -35
    unit: °C
    scope: material
    conditions:
      compound: CSM75 black (Polymax)
      form: range as printed in the header block
    method: Range printed in a supplier datasheet
    status: ground
    source: polymax-csm75
    where: Header block, line Operating Temperature range
  - benchmark: max_service_temp
    label: High end of operating temperature range, CSM75
    value: 125
    unit: °C
    scope: material
    conditions:
      compound: CSM75 black (Polymax)
      form: range as printed in the header block
    method: Range printed in a supplier datasheet
    status: ground
    source: polymax-csm75
    where: Header block, line Operating Temperature range
  - benchmark: total_mass_loss
    label: Total mass loss, Okonite I/C 6-61 cable insulation (DuPont Hypalon)
    value: 9.13
    unit: '%'
    scope: material
    conditions:
      product: cable insulation, Okonite I/C 6-61, Hypalon by DuPont
      data_reference: GSFC3604
      cure: blank in the row
      test: GSFC outgassing test in vacuum, as described in the NASA report
    method: Value printed in the NASA GSFC outgassing compilation
    status: ground
    source: nasa-rp1124
    where: Materials table, row CABLE I/C 6-61 BY OKONITE, DuPont HYPALON, GSFC3604, %TML column
  - benchmark: collected_volatile_condensable_material
    label: Collected volatile condensable material, same cable row
    value: 4.52
    unit: '%'
    scope: material
    conditions:
      product: cable insulation, Okonite I/C 6-61, Hypalon by DuPont
      data_reference: GSFC3604
      cure: blank in the row
      test: GSFC outgassing test in vacuum
    method: Value printed in the NASA GSFC outgassing compilation
    status: ground
    source: nasa-rp1124
    where: Materials table, row CABLE I/C 6-61 BY OKONITE, DuPont HYPALON, GSFC3604, %CVCM column
  - benchmark: total_mass_loss
    label: Total mass loss, Coverlite H fabric (Hypalon-coated nylon)
    value: 0.98
    unit: '%'
    scope: material
    conditions:
      product: COVERLITE H FABRIC 55-61811-XX, Hypalon coated nylon
      data_reference: GSFC8399
      cure_time: 72H as printed
      cure_temperature: 125 as printed (unit not given in the table legend)
      atmosphere: E-2 as printed
    method: Value printed in the NASA GSFC outgassing compilation
    status: ground
    source: nasa-rp1124
    where: Materials table, row COVERLITE H FABRIC, GSFC8399, %TML column
  - benchmark: collected_volatile_condensable_material
    label: Collected volatile condensable material, Coverlite H fabric
    value: 0.02
    unit: '%'
    scope: material
    conditions:
      product: COVERLITE H FABRIC 55-61811-XX, Hypalon coated nylon
      data_reference: GSFC8399
      cure_time: 72H as printed
      cure_temperature: 125 as printed (unit not given in the table legend)
      atmosphere: E-2 as printed
    method: Value printed in the NASA GSFC outgassing compilation
    status: ground
    source: nasa-rp1124
    where: Materials table, row COVERLITE H FABRIC, GSFC8399, %CVCM column
  - benchmark: water_vapor_regained
    label: Water vapor regained, Coverlite H fabric
    value: 0.8
    unit: '%'
    scope: material
    conditions:
      product: COVERLITE H FABRIC 55-61811-XX, Hypalon coated nylon
      data_reference: GSFC8399
      cure_time: 72H as printed
      cure_temperature: 125 as printed (unit not given in the table legend)
      atmosphere: E-2 as printed
    method: Value printed in the NASA GSFC outgassing compilation
    status: ground
    source: nasa-rp1124
    where: Materials table, row COVERLITE H FABRIC, GSFC8399, %WVR column
  - benchmark: chlorine_content
    label: Chlorine content, general description of the polymer
    value: 20
    value_high: 40
    bound: range
    unit: '%'
    scope: material
    conditions:
      basis: stated for the product as a whole, by weight
    method: Range stated in the encyclopedia entry (sentence on synthesis)
    status: ground
    note: The same page gives 20 to 45 % for commercial grades, and GreenSpec gives 27 to 45 %; the sources disagree.
    source: wiki-hypalon
    where: Synthesis section, sentence beginning 'The product contains'
  - benchmark: chlorine_content
    label: Chlorine content, commercial grades (Mark, Polymer Data Handbook)
    value: 20
    value_high: 45
    bound: range
    unit: '%'
    scope: material
    conditions:
      basis: commercial grades, by weight
    method: Range stated in the encyclopedia entry, citing Mark (Polymer Data Handbook)
    status: ground
    note: Disagrees with the 20 to 40 % range given earlier on the same page.
    source: wiki-hypalon
    where: Synthesis section, paragraph beginning 'Commercial grades typically contain'
  - benchmark: chlorine_content
    label: Chlorine content, GreenSpec description
    value: 27
    value_high: 45
    bound: range
    unit: '%'
    scope: material
    conditions:
      basis: stated under the heading What is Chlorosulfonated polyethylene
    method: Range stated on a building-materials information page
    status: ground
    note: A third range; see the two Wikipedia ranges above.
    source: greenspec-cspe
    where: What is Chlorosulfonated polyethylene section
  - benchmark: sulfur_content
    label: Sulfur content, commercial grades (Mark, Polymer Data Handbook)
    value: 1
    value_high: 2
    bound: range
    unit: '%'
    scope: material
    conditions:
      basis: commercial grades, by weight
    method: Range stated in the encyclopedia entry, citing Mark (Polymer Data Handbook)
    status: ground
    source: wiki-hypalon
    where: Synthesis section, paragraph beginning 'Commercial grades typically contain'
corrosion:
  - environment: Sunlight, ozone and weather (outdoor exposure)
    headline: CSM resists ozone, sunlight and weather well, according to the family guide and two compound datasheets.
    effect: The Robinson Rubber family guide rates ozone, sunlight and weather resistance as Excellent. Angst+Pfister describes compound 70.98-01 as having good resistance against UV and ozone. Polymax says CSM75 resists ozone, aging and weathering. No numeric UV or ozone test result, and no exposure time, was found in the sources read.
    rating: low
    conditions:
      basis: qualitative ratings in a family guide and two datasheets; no exposure time or test standard stated
    source: rrpc-csm
    where: Environmental Performance table (Ozone, Sunlight and Weather rows); Angst+Pfister datasheet description; Polymax header description
  - environment: Incompatible fluids and solvents
    headline: Aromatic and chlorinated solvents and polar fluids attack CSM75, according to its datasheet.
    effect: 'Polymax lists propane, butane, aliphatic oils, polar solvents, phosphate-ester fluids, aromatic hydrocarbons and chlorinated hydrocarbons as not compatible with CSM75. The Robinson Rubber guide rates ketones, halogenated solvents, aromatic petroleum and diester oils as Poor. The two sources disagree on aliphatic oils and fuels: the Robinson guide rates aliphatic hydrocarbon fuel Fair to Good and mineral oils Good to Very Good.'
    rating: moderate
    conditions:
      basis: compatibility list in a supplier datasheet and ratings in a family guide; no immersion test or swelling figure stated
    source: polymax-csm75
    where: Opening description paragraph (incompatibility list); Robinson Rubber Chemical Resistance table
  - environment: Acids, alkalis and oxidising media
    headline: Acids and alkalis are rated from good to excellent, according to the family guide and the CSM75 datasheet.
    effect: The Robinson Rubber guide rates dilute acids Excellent, concentrated acids Good to Excellent, and dilute and concentrated alkalies Good to Excellent. Polymax says CSM75 resists many acids and oxidising media.
    rating: low
    conditions:
      basis: qualitative ratings; concentrations and temperatures not stated in the sources read
    source: rrpc-csm
    where: Chemical Resistance table, Acids and Alkalies rows
  - environment: Heat ageing in service
    headline: No heat-ageing test result was found in the sources read.
    effect: The sources give maximum service temperatures (see properties) but no time-at-temperature test and no property-retention result for any CSM compound.
    rating: unknown
    conditions:
      basis: not found in the sources read
    source: angst-csm70
    where: Thermal properties block, operating temperature max. (stated as approximate)
risks:
  hazards:
    - text: The 2021 safety data sheet for 2990 HYPALON Adhesive, a solvent adhesive that contains a Hypalon name and is not the bare polymer, gives the signal word Danger and classes the mixture as a highly flammable liquid and vapour, a skin and eye irritant, a possible skin sensitiser, a cause of drowsiness or dizziness, and toxic to aquatic life. Butanone is the listed ingredient in the composition table; cyclohexane and acetone are named in the Contains line.
      ghs:
        - H225
        - H315
        - H317
        - H319
        - H336
        - H411
      source: sds-2990-rev
      where: Section 2.1 (classification) and Section 2 signal word and hazard statements; Section 3.2 (Mixtures table)
    - text: The older 2008 safety data sheet for the same adhesive gives the main hazards as irritating to eyes and skin and toxic to aquatic organisms, with repeated exposure possibly causing skin dryness or cracking. It names cyclohexane as a hazardous ingredient. These hazards come from the solvents in the adhesive, not from the rubber.
      ghs: []
      source: sds-2990-2008
      where: Section 2 (Hazards identification) and Section 3 (Composition)
    - text: No GHS hazard classification for the bare chlorosulfonated polyethylene polymer was found in the sources read. GreenSpec states that burning chlorosulfonated polyethylene releases hydrogen chloride and other emissions, including carbon monoxide and sulfur dioxide.
      ghs: []
      source: greenspec-cspe
      where: Environment and health section
  failure_risks:
    - mode: Excess outgassing in vacuum
      trigger: Vacuum test of a Hypalon cable insulation in NASA's GSFC outgassing compilation
      consequence: The Okonite cable insulation row shows 9.13 % total mass loss and 4.52 % collected volatile condensable material. Both are far above the low-outgassing screen that the report describes, so the cable would not meet the report's selection criteria.
      severity: high
      source: nasa-rp1124
      where: Materials table, row GSFC3604; Introduction (selection criteria)
    - mode: Swelling or breakdown in incompatible fluids
      trigger: Contact with the fluids Polymax lists as not compatible with CSM75, such as aromatic hydrocarbons and chlorinated hydrocarbons
      consequence: The sources give no swelling, volume or strength-loss figures for these fluids, so the risk is described qualitatively only.
      severity: moderate
      source: polymax-csm75
      where: Opening description paragraph (incompatibility list)
    - mode: Use below the stated low-temperature limit
      trigger: Operation colder than the low end of the stated range (-35 °C for CSM75, -30 °C for compound 70.98-01)
      consequence: The datasheets give no performance data below these limits, so the material cannot be assumed to flex or seal there.
      severity: moderate
      source: angst-csm70
      where: Thermal properties block (operating temperature min.)
  side_effects:
    - text: When burned, the polymer releases hydrogen chloride, which GreenSpec lists among its combustion products.
      affects: People near a fire and any metal or electronics it reaches
      source: greenspec-cspe
      where: Environment and health section
  handling:
    - text: Keep the rubber away from the fluids Polymax lists as not compatible, especially aromatic and chlorinated hydrocarbons.
      source: polymax-csm75
      where: Opening description paragraph
    - text: Specify the compound, because hardness, tensile strength and cure chemistry differ between the compounds in these sources.
      source: angst-csm70
      where: Header block and disclaimer
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Cable insulation and jacketing
    example: NASA's outgassing compilation records a Hypalon cable insulation from Okonite (DuPont Hypalon) and marks its row as failing the report's low-outgassing criteria, so it is a test record rather than a space-cable recommendation.
    source: nasa-rp1124
    where: Materials table, CABLE I/C 6-61 row (GSFC3604)
  - application: structures
    device: Single-ply roofing membranes for flat roofs (terrestrial building use)
    example: Wikipedia says CSM is used as single-ply roofing membranes for flat roofs, and the GreenSpec page credits its weatherability and UV stability for commercial roofing.
    source: wiki-hypalon
    where: Applications section, Construction and automotive subsection; GreenSpec 'What is it used for?' section
supply:
  - subject: Chlorosulfonated polyethylene (no USGS commodity entry)
    feedstock: Low-density or high-density polyethylene, treated with chlorine and sulfur dioxide, or sulfuryl chloride, in the presence of a radical initiator (Wikipedia)
    producers: []
    critical_lists: []
    recycling: Not found in the sources read.
    substitutes: []
    note: Tosoh Corporation in Japan makes it as Toso-CSM, and various manufacturers in China are named as producers. The sources give no production shares. DuPont Performance Elastomers announced the closure of its Beaumont, Texas plant, its sole CSM plant, and Wikipedia says the closure date was later delayed.
    source: wiki-hypalon
    where: Synthesis, Discontinuance and Current production sections
media: []
documents:
  - title: Hypalon (CSM) encyclopedia entry (redirect from Chlorosulfonated polyethylene)
    type: database
    url: https://en.wikipedia.org/wiki/Chlorosulfonated_polyethylene
  - title: 'GreenSpec: Chlorosulfonated polyethylene (CSPE), environment and health'
    type: database
    url: https://greenspec.co.uk/building-design/chlorosulfonated-polyethylene-cspe-environment-and-health/
  - title: 'NASA Reference Publication 1124 Rev. 3: Outgassing Data for Selecting Spacecraft Materials'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19940017416/downloads/19940017416.pdf
    year: 1993
  - title: CSM (Hypalon) Black 75 ShA datasheet (Polymax)
    type: datasheet
    url: https://m2dev.polymax.co.uk/media/documents/Datasheet/oring/CSM75-CSM_Hypalon_Black_75_ShA.pdf
  - title: CSM 70.98-01 technical data sheet (Angst+Pfister)
    type: datasheet
    url: https://www.apsoparts.com/media/downloads/asset//std.lang.all/8-/01/CSM_70_98-01.pdf
    year: 2025
  - title: 'Rubber Material Selection Guide: CSM or Hypalon (Robinson Rubber Products)'
    type: datasheet
    url: https://robinsonrubber.com/wp-content/uploads/2024/02/RRPC-Rubber-Selection-Guide-Hypalon-Rubber.pdf
    year: 2024
  - title: 'Safety data sheet: 2990 HYPALON Adhesive, version 1.1'
    type: sds
    url: https://defender.ca/assets/pdf/weaver/2990-hypalon-adhesive-en-v1.1.pdf
    year: 2021
  - title: 'Safety data sheet: Polymarine 2990 Hypalon Adhesive (older sheet)'
    type: sds
    url: https://defender.ca/assets/pdf/polymarine/polymarine-2990-hypalon-adhesive.pdf
    year: 2008
gaps:
  - No flight result, space radiation test or atomic-oxygen result for any chlorosulfonated polyethylene compound was found; the NASA outgassing compilation is a ground test.
  - The CAS number 68037-39-8 is not confirmed in an opened source. The PubChem record was behind an automated-access check and was not read.
  - No GHS classification for the bare polymer was found in an opened source; the hazard entries come from two adhesive safety data sheets and from GreenSpec's combustion statement.
  - Production shares by country were not found. The USGS Mineral Commodity Summaries do not cover this material, so the supply section has no share data.
  - Heat-ageing, UV-ageing and humidity test results were not found, so the corrosion section relies on qualitative ratings.
  - The Robinson Rubber family guide gives temperature limits in degrees Fahrenheit and a brittle point. These are family-level ranges, not one grade's value, so they are not recorded as properties.
  - The Minnesota Rubber compounds 399ES and 399BL (hardness, tensile strength and elongation) were read on a page whose numbers could not be matched in the raw HTML, so they are not recorded.
  - 'The cure chemistry conflicts: Wikipedia says CSM is cured with metal oxides, while the Angst+Pfister datasheet for compound 70.98-01 names sulfur as its curing agent.'
  - Chlorine content is given as 20 to 40 %, 20 to 45 % and 27 to 45 % in three sources; all three are recorded and none is chosen.
  - NASA row GSFC8372 (Hypalon-coated nylon) has a total mass loss that the PDF text layer prints as garbled characters, so that row is not recorded.
  - The NASA legend does not give a unit for cure temperature in the rows read, and the atmosphere code E-2 is not expanded in the sections read.
  - 'Property names not on the canonical list are used: hardness_shore_a, total_mass_loss, collected_volatile_condensable_material, water_vapor_regained, chlorine_content and sulfur_content.'
  - Electrical properties (dielectric strength, resistivity), density of other compounds, and radiation effects were not found or not looked up.
sources:
  wiki-hypalon:
    title: Hypalon (encyclopedia entry; the URL given is a redirect from Chlorosulfonated polyethylene)
    url: https://en.wikipedia.org/wiki/Chlorosulfonated_polyethylene
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  greenspec-cspe:
    title: 'Chlorosulfonated polyethylene (CSPE): environment and health (GreenSpec)'
    url: https://greenspec.co.uk/building-design/chlorosulfonated-polyethylene-cspe-environment-and-health/
    kind: web
    license: Web page (cited, not reproduced)
  nasa-rp1124:
    title: Outgassing Data for Selecting Spacecraft Materials, NASA Reference Publication 1124, Revision 3 (Campbell and Scialdone, GSFC)
    id: NTRS 19940017416
    url: https://ntrs.nasa.gov/api/citations/19940017416/downloads/19940017416.pdf
    year: 1993
    kind: report
    license: public domain (NASA)
  polymax-csm75:
    title: CSM (Hypalon) Black 75 ShA, product CSM75 (Polymax)
    url: https://m2dev.polymax.co.uk/media/documents/Datasheet/oring/CSM75-CSM_Hypalon_Black_75_ShA.pdf
    kind: datasheet
    license: Supplier datasheet (cited, not reproduced)
  angst-csm70:
    title: Technical Data Sheet CSM 70.98-01 (Angst+Pfister), status released
    id: compound code CSM 70.98-01
    url: https://www.apsoparts.com/media/downloads/asset//std.lang.all/8-/01/CSM_70_98-01.pdf
    year: 2025
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  rrpc-csm:
    title: 'Rubber Material Selection Guide: CSM or Hypalon, chlorosulphonated polyethylene (Robinson Rubber Products)'
    url: https://robinsonrubber.com/wp-content/uploads/2024/02/RRPC-Rubber-Selection-Guide-Hypalon-Rubber.pdf
    year: 2024
    kind: datasheet
    license: Supplier guide (cited, not reproduced)
  sds-2990-rev:
    title: Safety data sheet, 2990 HYPALON Adhesive, version 1.1 (revision date 15/12/2021)
    url: https://defender.ca/assets/pdf/weaver/2990-hypalon-adhesive-en-v1.1.pdf
    year: 2021
    kind: datasheet
    license: Manufacturer safety data sheet (cited, not reproduced)
  sds-2990-2008:
    title: Safety data sheet, Polymarine 2990 Hypalon Adhesive (issued 24/04/2008)
    url: https://defender.ca/assets/pdf/polymarine/polymarine-2990-hypalon-adhesive.pdf
    year: 2008
    kind: datasheet
    license: Manufacturer safety data sheet (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-11-02'
review:
  status: draft
  method: assistant
  checked_values: 18
  unreachable: 1
  caveats: 4
  note: 'Values read by an AI assistant on 2026-11-02 from the pages and PDFs named in each entry. Unreachable: the PubChem record (automated-access check). Caveats: datasheet values are for specific compounds and are not guaranteed; chlorine ranges disagree across sources; the NASA rows are ground outgassing tests; the hazard data come from adhesive safety data sheets, not the polymer.'
story:
  recipe:
    line: Chlorosulfonated polyethylene is made by treating polyethylene with chlorine and sulfur dioxide under UV light, which replaces hydrogen atoms along the chain with chlorine and adds chlorosulfonyl (ClSO2) groups (Wikipedia). The chlorosulfonyl groups are the cure sites. Wikipedia says CSM is cured with metal oxides, while the Angst+Pfister datasheet for compound 70.98-01 names sulfur as its curing agent.
    parts:
      - name: Polyethylene backbone
        share: not stated
        role: Low-density or high-density polyethylene is the starting polymer; chlorine and chlorosulfonyl groups are added along its chain (Wikipedia).
      - name: Chlorine
        symbol: Cl
        share: 20-45 % by weight for commercial grades (Wikipedia)
        role: Disrupts the crystallinity of the polyethylene so the polymer becomes an elastomer, and gives flame resistance and cold flexibility (Wikipedia; Polymax).
      - name: Sulfur
        symbol: S
        share: 1-2 % by weight for commercial grades (Wikipedia)
        role: Present in the chlorosulfonyl (ClSO2) groups, which react with the cure agent to form cross-links (Wikipedia).
  risk_groups:
    - title: For people
      level: 1
      verdict: Hazards from an adhesive, not the polymer
      lead: No hazard classification for the bare CSM polymer was found. The hazard data come from a solvent adhesive that carries the Hypalon name.
      points:
        - label: Adhesive
          line: The 2021 safety data sheet for 2990 HYPALON Adhesive gives the signal word Danger, with flammable-liquid, eye-irritant, skin-sensitiser and drowsiness hazards. The older 2008 sheet names cyclohexane as a hazardous ingredient.
        - label: In a fire
          line: GreenSpec says burning the polymer releases hydrogen chloride and other emissions, including carbon monoxide and sulfur dioxide.
    - title: If it fails in vacuum
      level: 2
      verdict: The one vacuum test here fails
      lead: The only space-related result is a ground outgassing test, and the cable row fails the report's criteria.
      points:
        - label: Cable insulation
          line: The Okonite cable insulation (DuPont Hypalon) in NASA's table shows 9.13 % total mass loss and 4.52 % collected volatile condensable material.
    - title: Handling and storage
      points:
        - label: Fluids
          line: Polymax lists propane, butane, aliphatic oils, polar solvents, phosphate-ester fluids, aromatic hydrocarbons and chlorinated hydrocarbons as not compatible with CSM75.
        - label: Cold
          line: The lowest stated operating temperatures are -35 °C for CSM75 and -30 °C for compound 70.98-01.
  why: Chlorosulfonated polyethylene, sold as Hypalon, is a synthetic rubber (CSM) made from polyethylene. Chlorine and chlorosulfonyl groups give it resistance to ozone, sunlight and many chemicals, according to the datasheets and the family guide. It is a rubber for weathering and chemical service, not a structural or space-qualified material, and the sources contain no flight data for it.
  uses:
    - where: Roofing and cable jacketing
      line: Wikipedia lists single-ply roofing membranes for flat roofs and jacketing for electrical cables in harsh industrial environments. GreenSpec credits CSPE's weatherability and UV stability for commercial roofing.
    - where: Spacecraft materials screening
      line: NASA's outgassing compilation includes Hypalon cable insulation and Hypalon-coated nylon fabric. The cable row (9.13 % total mass loss) fails the report's screening criteria. The Coverlite H fabric row (0.98 % total mass loss, 0.02 % collected volatile condensable material) passes both criteria the report describes.
  can_do:
    - label: Resists ozone, sunlight and weather
      line: the family guide rates each as Excellent.
    - label: Strength
      line: Operates from -35 °C to 125 °C for CSM75 and from -30 °C to 120 °C for compound 70.98-01, per the two datasheets.
    - label: Strength
      line: Stretches to 300 % at break for compound 70.98-01, per its datasheet.
    - label: Strength
      line: Carries a hardness of 70 Shore A (compound 70.98-01) to 75 ShA (CSM75), so it is a firm elastomer rather than a soft one.
  compare: The compounds in these sources differ widely. Compound 70.98-01 is 70 Shore A with 300 % elongation at break and 8.00 N/mm² tensile strength. CSM75 is 75 ShA and is rated from -35 °C to 125 °C. Among NASA's rows, the same material family spans total mass loss from 0.98 % to 9.13 %, so the cure and the product matter more than the family name. The coated fabric row passes the screening criteria and the cable row fails them.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Maximum operating temperature
      benchmark: max_service_temp
    - label: Elongation at break
      benchmark: elongation
  handling:
    - Keep it away from the fluids Polymax lists as not compatible, especially aromatic and chlorinated hydrocarbons.
    - 'Treat smoke from a fire as hazardous: the polymer releases hydrogen chloride when burned.'
    - Specify the compound, because hardness, strength and cure differ between the compounds in these sources.
  good_for:
    - Ozone, sunlight and weather exposure, where the family guide rates resistance as Excellent.
    - Flexible jackets and roofing membranes on the ground, per Wikipedia.
  watch_out:
    - 'Vacuum outgassing: the Okonite cable row shows 9.13 % total mass loss, far above the report''s screening criteria.'
    - 'Sources disagree on chlorine content: 20 to 40 %, 20 to 45 % and 27 to 45 %.'
    - 'Cure chemistry is disputed: Wikipedia says metal oxides, and the Angst+Pfister datasheet names sulfur.'
    - The hazard data come from a solvent adhesive, not from the bare polymer.
  verdict: 'Chlorosulfonated polyethylene (Hypalon) is a weather- and ozone-resistant rubber, with datasheet operating ranges of -35 °C to 125 °C for CSM75. Its weak point is vacuum outgassing: the one cable row in NASA''s table fails the screen. No hazard classification for the bare polymer was found.'