{
  "spore": "profile",
  "id": "pu",
  "spore_version": "0.2",
  "family": "engineering-polymers",
  "name": "Polyurethane",
  "abbreviation": "PU",
  "role": "thermoplastic and cast elastomer, and rigid or flexible foam, made from a diisocyanate and a polyol",
  "category": "polymers",
  "type": "polyurethanes",
  "summary": "Polyurethane (PU) is a polymer whose chains are joined by carbamate (urethane) links, made by reacting a diisocyanate or polymeric isocyanate with a polyol. As a sample on the MISSE 2 PEACE experiment in low Earth orbit it had an atomic oxygen erosion yield of 1.56e-24 cm3/atom, close to the 1.58e-24 cm3/atom predicted by NASA. Cast thermoplastic PU grades read for this profile are 1.03 g/cm3 with a tensile strength above 40 MPa and an elongation above 300 %, and a 95 Shore A elastomer from another range has a tensile strength of 10.5 MPa and an elongation of 250 %.\n",
  "best_for": "Flexible, tough elastomers and seals in the ground-tested grades read, and a known LEO atomic oxygen rate of 1.56e-24 cm3/atom",
  "weakest_at": "Atomic oxygen in low Earth orbit (erosion yield 1.56e-24 cm3/atom) and hydrolysis; the isocyanate precursors are strong respiratory sensitisers",
  "identity": {
    "formula": "Polyurethane: carbamate-linked polymer of a diisocyanate and a polyol; NASA TM repeat unit C6H10O4N2",
    "cas": "",
    "designations": [],
    "source": "wikipedia-polyurethane",
    "where": "Lead and Chemistry sections (carbamate links, diisocyanate plus polyol); repeat unit C6H10O4N2 from NASA TM-2008-215490 Table IV"
  },
  "tags": {
    "environments": [
      "low-earth-orbit"
    ],
    "stresses": [
      "atomic-oxygen",
      "uv",
      "vacuum-and-outgassing"
    ],
    "applications": []
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, polyurethane (MISSE 2 PEACE ref. 12)",
      "value": 1.2345,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "density as listed in NASA Table II, column header 'Density, ref. 12, rho'"
      },
      "method": "Density value listed in NASA TM-2008-215490 Table II; the report gives no test temperature",
      "status": "ground",
      "source": "nasa-tm-2008-215490",
      "where": "Table II (MISSE 2 PEACE polymers density and fractional ash content), row Polyurethane PU",
      "source_detail": {
        "title": "Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit",
        "id": "NASA/TM-2008-215490 (Banks and Backus, 2008), NTRS 20090011780",
        "url": "https://ntrs.nasa.gov/citations/20090011780",
        "year": 2008,
        "kind": "report",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "atomic_oxygen_erosion_yield",
      "label": "Atomic oxygen erosion yield, polyurethane (MISSE 2)",
      "value": 1.56e-24,
      "bound": "exact",
      "unit": "cm3/atom",
      "scope": "material",
      "conditions": {
        "platform": "ISS, MISSE 2 PEACE, low Earth orbit",
        "atomic_oxygen_fluence": "8.43×10^21 atoms/cm2 as printed in NASA TM Section 2 text"
      },
      "method": "Measured on MISSE 2 flight samples and listed in NASA TM-2008-215490 Table I",
      "status": "flight",
      "source": "nasa-tm-2008-215490",
      "where": "Table I (MISSE 2 PEACE polymers erosion yield data), row Polyurethane PU",
      "source_detail": {
        "title": "Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit",
        "id": "NASA/TM-2008-215490 (Banks and Backus, 2008), NTRS 20090011780",
        "url": "https://ntrs.nasa.gov/citations/20090011780",
        "year": 2008,
        "kind": "report",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "atomic_oxygen_erosion_yield",
      "label": "Atomic oxygen erosion yield, polyurethane (predicted)",
      "value": 1.58e-24,
      "bound": "exact",
      "unit": "cm3/atom",
      "scope": "material",
      "conditions": {
        "basis": "NASA predictive tool, NASA TM-2008-215490"
      },
      "method": "Predicted by the NASA predictive tool and listed in Table VII beside the MISSE 2 value",
      "status": "calculated",
      "source": "nasa-tm-2008-215490",
      "where": "Table VII (comparison of predicted and MISSE 2 measured erosion yields), row Pol yurethane PU",
      "source_detail": {
        "title": "Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit",
        "id": "NASA/TM-2008-215490 (Banks and Backus, 2008), NTRS 20090011780",
        "url": "https://ntrs.nasa.gov/citations/20090011780",
        "year": 2008,
        "kind": "report",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, cast thermoplastic PU (CPU-H)",
      "value": 1.03,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "product": "Max Spare CPU-H, thermoplastic cast polyurethane",
        "tolerance_as_printed": "±0.02"
      },
      "method": "Nominal value printed on the supplier datasheet, ASTM D 792",
      "status": "ground",
      "source": "maxspare-cpu-h",
      "where": "Physical properties table, Density row",
      "source_detail": {
        "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
        "id": "CPU-H physical properties table",
        "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, cast thermoplastic PU (CPU-H), 95 Shore A",
      "value": 40,
      "bound": "exact",
      "unit": "Mpa",
      "scope": "material",
      "conditions": {
        "product": "Max Spare CPU-H",
        "bound_as_printed": "> 40"
      },
      "method": "Nominal value printed on the supplier datasheet, ASTM D 412; printed unit is Mpa",
      "status": "ground",
      "source": "maxspare-cpu-h",
      "where": "Physical properties table, Tensile strength row",
      "source_detail": {
        "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
        "id": "CPU-H physical properties table",
        "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation at break, cast thermoplastic PU (CPU-H)",
      "value": 300,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "product": "Max Spare CPU-H",
        "bound_as_printed": "> 300"
      },
      "method": "Nominal value printed on the supplier datasheet, ASTM D 412",
      "status": "ground",
      "source": "maxspare-cpu-h",
      "where": "Physical properties table, Elongation at break row",
      "source_detail": {
        "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
        "id": "CPU-H physical properties table",
        "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "min_service_temp",
      "label": "Operating temperature lower limit, CPU-H",
      "value": -30,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "product": "Max Spare CPU-H",
        "range_as_printed": "-30 to +100 °C"
      },
      "method": "Operating temperature printed on the supplier datasheet",
      "status": "ground",
      "source": "maxspare-cpu-h",
      "where": "Physical properties table, Operating Temp. row",
      "source_detail": {
        "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
        "id": "CPU-H physical properties table",
        "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Operating temperature upper limit, CPU-H",
      "value": 100,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "product": "Max Spare CPU-H",
        "range_as_printed": "-30 to +100 °C"
      },
      "method": "Operating temperature printed on the supplier datasheet",
      "status": "ground",
      "source": "maxspare-cpu-h",
      "where": "Physical properties table, Operating Temp. row",
      "source_detail": {
        "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
        "id": "CPU-H physical properties table",
        "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, PU range at 95 Shore A",
      "value": 10.5,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "hardness": "95 Shore A",
        "standard_as_printed": "BS EN ISO 37",
        "cure": "full cure"
      },
      "method": "Typical value printed on the ARRK PU range datasheet, marked as for comparative purposes only",
      "status": "ground",
      "source": "arrk-pu-range",
      "where": "Material properties table, Tensile Strength row, column 95",
      "source_detail": {
        "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
        "id": "ARRK SPG datasheet, December 2022",
        "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation at break, PU range at 95 Shore A",
      "value": 250,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "hardness": "95 Shore A",
        "standard_as_printed": "BS EN ISO 37",
        "cure": "full cure"
      },
      "method": "Typical value printed on the ARRK PU range datasheet, marked as for comparative purposes only",
      "status": "ground",
      "source": "arrk-pu-range",
      "where": "Material properties table, Elongation at Break row, column 95",
      "source_detail": {
        "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
        "id": "ARRK SPG datasheet, December 2022",
        "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, PU range at 35 Shore A",
      "value": 2.5,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "hardness": "35 Shore A",
        "standard_as_printed": "BS EN ISO 37",
        "cure": "full cure"
      },
      "method": "Typical value printed on the ARRK PU range datasheet",
      "status": "ground",
      "source": "arrk-pu-range",
      "where": "Material properties table, Tensile Strength row, column 35",
      "source_detail": {
        "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
        "id": "ARRK SPG datasheet, December 2022",
        "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation at break, PU range at 35 Shore A",
      "value": 1000,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "hardness": "35 Shore A",
        "standard_as_printed": "BS EN ISO 37",
        "cure": "full cure"
      },
      "method": "Typical value printed on the ARRK PU range datasheet",
      "status": "ground",
      "source": "arrk-pu-range",
      "where": "Material properties table, Elongation at Break row, column 35",
      "source_detail": {
        "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
        "id": "ARRK SPG datasheet, December 2022",
        "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    },
    {
      "benchmark": "flash_point",
      "label": "Flash point, Part A of a polyurethane elastomer system",
      "value": 368,
      "bound": "exact",
      "unit": "°F",
      "scope": "material",
      "conditions": {
        "product": "Smooth-On Crystal Clear Series Part A (isocyanate component)",
        "bound_as_printed": ">368°F"
      },
      "method": "Value printed in the supplier SDS, Section 9",
      "status": "ground",
      "source": "smooth-on-480a-sds",
      "where": "Section 9, Flash Point row",
      "source_detail": {
        "title": "Smooth-On Safety Data Sheet, Crystal Clear Series Part A (SDS No. 480A)",
        "id": "SDS No. 480A, revision 25 June 2021, version 2.0",
        "url": "https://www.smooth-on.com/msds/files/CRYSTAL%20CLEAR%203713%20A_3_B_3%20SDS.pdf",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier SDS, linked not reproduced"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Maximum operating temperature, PU range (35 to 65 Shore A)",
      "value": 100,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "note": "Maximum operating temperature 100 °C at 35 to 65 Shore A, 120 °C at 75 to 95 Shore A, as printed"
      },
      "method": "Printed on the ARRK datasheet with the note that the value is application specific",
      "status": "ground",
      "source": "arrk-pu-range",
      "where": "Material properties table, Max. Operating Temperature row",
      "source_detail": {
        "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
        "id": "ARRK SPG datasheet, December 2022",
        "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "manufacturer datasheet, linked not reproduced"
      }
    }
  ],
  "corrosion": [],
  "risks": {
    "hazards": [
      {
        "text": "Isocyanate component (Part A): 4,4' Methylenedicyclohexyl diisocyanate, CAS 5124-30-1, 35 – 85 % by weight. Signal word Danger. Causes skin irritation, may cause an allergic skin reaction, causes serious eye irritation, toxic if inhaled, may cause allergy or asthma symptoms or breathing difficulties if inhaled, may cause respiratory irritation.",
        "ghs": [
          "H315",
          "H317",
          "H319",
          "H331",
          "H334",
          "H335"
        ],
        "source": "smooth-on-480a-sds",
        "where": "Section 2 (Hazard identification, H-code list) and Section 3.1 (composition)"
      },
      {
        "text": "MDI is described as an allergen and sensitiser; sensitised people may have dangerous systemic reactions to very small exposures, including respiratory failure.",
        "ghs": [
          "H334",
          "H335"
        ],
        "source": "wikipedia-mdi",
        "where": "Hazards section (H334 and H335 listed in the article infobox)"
      }
    ],
    "failure_risks": [
      {
        "mode": "Atomic oxygen erosion in low Earth orbit",
        "trigger": "Exposure of a polyurethane part to atomic oxygen in low Earth orbit, as on the MISSE 2 flight",
        "consequence": "Surface erosion at 1.56e-24 cm3/atom as measured on MISSE 2, and 1.58e-24 cm3/atom predicted by NASA.",
        "severity": "moderate",
        "source": "nasa-tm-2008-215490",
        "where": "Table I and Table VII"
      },
      {
        "mode": "Hydrolysis",
        "trigger": "Exposure to water over time",
        "consequence": "Wikipedia states that polyurethanes may degrade due to hydrolysis; no test figure is given.",
        "source": "wikipedia-polyurethane",
        "where": "Degradation section"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Isocyanate Part A is a respiratory and skin sensitiser; the SDS requires ventilation or respiratory protection when inadequately ventilated (P285).",
        "source": "smooth-on-480a-sds"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "mechanisms",
      "device": "Cast thermoplastic polyurethane seals and rollers",
      "example": "CPU-H, a cast thermoplastic polyurethane sold by Max Spare for seals, with a Shore A hardness of 95, density 1.03 g/cm3 and operating range -30 to +100 °C.",
      "source": "maxspare-cpu-h",
      "where": "Product header and Physical properties table"
    },
    {
      "application": "structures",
      "device": "Polymer sample on a space flight experiment",
      "example": "Polyurethane on the MISSE 2 PEACE tray, flown on the ISS in low Earth orbit, with erosion yield listed in NASA TM-2008-215490.",
      "source": "nasa-tm-2008-215490",
      "where": "Table I"
    },
    {
      "application": "structures",
      "device": "Foam and elastomer products",
      "example": "Polyurethane is made by reacting a diisocyanate with a polyol, and flexible foams began production in 1954 using TDI and polyester polyols.",
      "source": "wikipedia-polyurethane",
      "where": "Lead, Chemistry and History sections"
    }
  ],
  "supply": [
    {
      "subject": "Polyurethane (global output)",
      "producers": [],
      "critical_lists": [],
      "substitutes": [],
      "source": "wikipedia-polyurethane",
      "where": "Production section"
    },
    {
      "subject": "Methylene diphenyl diisocyanate (MDI, main isocyanate for rigid PU)",
      "producers": [],
      "critical_lists": [],
      "substitutes": [],
      "source": "wikipedia-mdi",
      "where": "Production section; Uses section"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NASA TM-2008-215490, Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit",
      "type": "report",
      "url": "https://ntrs.nasa.gov/citations/20090011780",
      "year": 2008
    },
    {
      "title": "Smooth-On Safety Data Sheet, Crystal Clear Series Part A, SDS No. 480A (revision 25 June 2021)",
      "type": "sds",
      "url": "https://www.smooth-on.com/msds/files/CRYSTAL%20CLEAR%203713%20A_3_B_3%20SDS.pdf",
      "year": 2021
    },
    {
      "title": "Max Spare CPU-H, Thermoplastic Cast Polyurethane datasheet",
      "type": "datasheet",
      "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf"
    },
    {
      "title": "ARRK, Elastomers Polyurethane (PU) and Silicone Material Datasheet Range, December 2022",
      "type": "datasheet",
      "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
      "year": 2022
    },
    {
      "title": "NIST Atomic Weights and Isotopic Compositions for All Elements (C, H, N, O)",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html"
    }
  ],
  "gaps": [
    "No flight or ground outgassing, total mass loss, UV or thermal-cycling result for polyurethane in space was read in this run; the NASA report gives only the erosion yield.",
    "The Wikipedia page gives no numeric repeat unit; the repeat unit used here is the NASA TM model unit C6H10O4N2, not a verified structure for a commercial PU.",
    "Cured-polyurethane hazard data were not found on a fetched page. The hazards recorded are from the Part A isocyanate SDS (Smooth-On), which is the reactive component, not the cured polymer.",
    "Isocyanate supply (MDI and TDI) producer shares by country were not found on a primary source; no USGS or critical-mineral list applies to PU.",
    "The Erlan 80 cast PU datasheet redirected to an unrelated page and could not be read.",
    "Hardness values for the ARRK and CPU-H grades are not in the canonical property list and are not recorded as properties; the Shore A numbers appear in the labels and uses.",
    "Atomic oxygen fluence (8.43e21 atoms/cm2) and the exposure duration (about 4 years) are printed in the NASA TM but are not recorded as properties because the name is not in the canonical list.",
    "The 2019 global production (25 Mt) and the MDI figure are from Wikipedia and carry no primary citation in the article text read.",
    "No PubChem record for polyurethane or MDI was read; PubChem returned a verification page.",
    "The NASA TM notes erosion yield can be affected by fluence and sample state; no per-sample exposure time for the PU flight sample was read beyond the 4-year total."
  ],
  "story": {
    "why": "Polyurethane is a versatile polymer joined by carbamate links. The NASA report records a LEO atomic oxygen erosion yield of 1.56e-24 cm3/atom on MISSE 2, close to its prediction. Cast thermoplastic grades read give tensile strengths of 40 MPa or more and elongations of 300 % or more.",
    "uses": [],
    "can_do": [
      {
        "label": "Stretch and recover",
        "line": "The ARRK range gives 1000 % elongation at break at 35 Shore A, and 250 % at 95 Shore A, both as typical values.",
        "benchmark": "elongation",
        "scope": "material",
        "value": "1000 % elongation"
      },
      {
        "label": "Survive in orbit with known erosion",
        "line": "NASA lists a MISSE 2 erosion yield for polyurethane of 1.56e-24 cm3/atom and predicts 1.58e-24 cm3/atom.",
        "benchmark": "atomic_oxygen_erosion_yield",
        "scope": "material",
        "value": "1.56e-24 cm3/atom"
      },
      {
        "label": "Work between -30 and 100 °C",
        "line": "The CPU-H datasheet prints an operating range of -30 to +100 °C.",
        "benchmark": "min_service_temp",
        "scope": "material",
        "value": "-30 to 100 °C"
      }
    ],
    "compare": "The rows compare different grades and test methods, so they are examples and not a ranking. The NASA density is for the polymer on the MISSE 2 tray, while the CPU-H and ARRK rows are supplier typical values.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Erosion yield",
        "benchmark": "atomic_oxygen_erosion_yield",
        "scope": "material"
      },
      {
        "label": "Tensile strength at 95 Shore A",
        "benchmark": "ultimate_tensile_strength",
        "scope": "material"
      }
    ],
    "handling": [
      "Treat the isocyanate component as a respiratory and skin sensitiser: use ventilation and respiratory protection, as the SDS requires.",
      "Check the current supplier SDS for each grade, since the cured elastomer and the isocyanate part are different materials.",
      "Treat the datasheet values as typical, not as specification limits."
    ],
    "good_for": [
      "Flexible elastomers: 1000 % elongation at break at 35 Shore A in the ARRK range.",
      "Known atomic oxygen behaviour: 1.56e-24 cm3/atom on MISSE 2, measured in low Earth orbit.",
      "Seals in a -30 to +100 °C range (CPU-H datasheet)."
    ],
    "watch_out": [
      "Atomic oxygen erodes PU at 1.56e-24 cm3/atom in low Earth orbit, so exterior use needs protection or a rate allowance.",
      "Isocyanate sensitisation: the Part A SDS prints H334, which can cause asthma-like symptoms on inhalation.",
      "No outgassing, UV or radiation result for PU in space was read, so only the erosion yield is recorded."
    ],
    "verdict": "Polyurethane has a MISSE 2 flight erosion yield of 1.56e-24 cm3/atom in low Earth orbit, a density of 1.2345 g/cm3 in the NASA table, and typical elastomer grades with tensile strengths from 2.5 to 40 MPa and elongations up to 1000 %. Its isocyanate precursors are strong sensitisers, and this profile has no sourced space outgassing or UV data.",
    "recipe": {
      "line": "Polyurethane is made by reacting a diisocyanate with a polyol, forming carbamate (urethane) links between the two monomers. The repeat unit used for the NASA atomic oxygen model is C6H10O4N2, with the atoms listed below.",
      "parts": [
        {
          "name": "Carbon",
          "symbol": "C",
          "role": "Carbon skeleton of the diisocyanate and polyol segments."
        },
        {
          "name": "Hydrogen",
          "symbol": "H",
          "role": "Hydrogen on the chain and in the urethane N-H groups."
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "Oxygen in the carbamate C=O and C-O-C links."
        },
        {
          "name": "Nitrogen",
          "symbol": "N",
          "role": "Nitrogen in the carbamate N-H links formed from the isocyanate."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The cured polymer is not described as hazardous in the sources read; the reactive isocyanate component is.",
        "points": [
          {
            "label": "Classification",
            "line": "The Smooth-On Part A SDS prints H315, H317, H319, H331, H334 and H335, with signal word Danger, for the isocyanate component."
          },
          {
            "label": "Composition",
            "line": "The same SDS lists 4,4' Methylenedicyclohexyl diisocyanate, CAS 5124-30-1, at 35 to 85 % by weight."
          }
        ],
        "level": 2,
        "verdict": "Isocyanate component is a respiratory and skin sensitiser"
      },
      {
        "title": "If it fails",
        "lead": "The failure route in these sources is erosion in orbit and hydrolysis.",
        "points": [
          {
            "label": "Atomic oxygen",
            "line": "On MISSE 2 the erosion yield was 1.56e-24 cm3/atom, against 1.58e-24 cm3/atom predicted by NASA."
          },
          {
            "label": "Hydrolysis",
            "line": "Wikipedia states that polyurethanes may degrade due to hydrolysis; no test figure is given."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-20",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 14,
    "unreachable": 2,
    "caveats": 4,
    "note": "Values read by an AI assistant on 2026-10-20 from the pages named. NASA Table I, II and VII were read from the NTRS PDF text. Unreachable Erlan 80 datasheet (redirect) and PubChem (verification page)."
  },
  "sources": {
    "nasa-tm-2008-215490": {
      "title": "Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit",
      "id": "NASA/TM-2008-215490 (Banks and Backus, 2008), NTRS 20090011780",
      "url": "https://ntrs.nasa.gov/citations/20090011780",
      "year": 2008,
      "kind": "report",
      "license": "NASA public document"
    },
    "wikipedia-polyurethane": {
      "title": "Polyurethane, Wikipedia",
      "id": "Polyurethane article, Lead, Chemistry, History, Degradation and Production sections",
      "url": "https://en.wikipedia.org/wiki/Polyurethane",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "wikipedia-mdi": {
      "title": "Methylene diphenyl diisocyanate, Wikipedia",
      "id": "MDI article, Uses, Hazards and Production sections",
      "url": "https://en.wikipedia.org/wiki/Methylene_diphenyl_diisocyanate",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "smooth-on-480a-sds": {
      "title": "Smooth-On Safety Data Sheet, Crystal Clear Series Part A (SDS No. 480A)",
      "id": "SDS No. 480A, revision 25 June 2021, version 2.0",
      "url": "https://www.smooth-on.com/msds/files/CRYSTAL%20CLEAR%203713%20A_3_B_3%20SDS.pdf",
      "year": 2021,
      "kind": "datasheet",
      "license": "supplier SDS, linked not reproduced"
    },
    "maxspare-cpu-h": {
      "title": "Max Spare CPU-H Thermoplastic Cast Polyurethane datasheet",
      "id": "CPU-H physical properties table",
      "url": "https://www.maxspare.com/sealingmaterials/CPU-H.pdf",
      "kind": "datasheet",
      "license": "manufacturer datasheet, linked not reproduced"
    },
    "arrk-pu-range": {
      "title": "ARRK Elastomers Polyurethane and Silicone Material Datasheet Range",
      "id": "ARRK SPG datasheet, December 2022",
      "url": "https://spg.arrk.com/assets/img/arrk-spg-datasheet-pu-elastomers-materials_dec-2022.pdf",
      "year": 2022,
      "kind": "datasheet",
      "license": "manufacturer datasheet, linked not reproduced"
    },
    "nist-carbon": {
      "title": "NIST Atomic Weights and Isotopic Compositions, carbon",
      "id": "NIST standard atomic weight of C [12.0096, 12.0116]",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html",
      "kind": "database",
      "license": "US government data"
    },
    "nist-hydrogen": {
      "title": "NIST Atomic Weights and Isotopic Compositions, hydrogen",
      "id": "NIST standard atomic weight of H [1.007 84, 1.008 11]",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&all=all&ascii=html",
      "kind": "database",
      "license": "US government data"
    },
    "nist-nitrogen": {
      "title": "NIST Atomic Weights and Isotopic Compositions, nitrogen",
      "id": "NIST standard atomic weight of N [14.006 43, 14.007 28]",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=N&all=all&ascii=html",
      "kind": "database",
      "license": "US government data"
    },
    "nist-oxygen": {
      "title": "NIST Atomic Weights and Isotopic Compositions, oxygen",
      "id": "NIST standard atomic weight of O [15.999 03, 15.999 77]",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=O&all=all&ascii=html",
      "kind": "database",
      "license": "US government data"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/pu/"
}