spore: profile
id: hdpe
spore_version: 0.2
family: polyolefins
name: High-density polyethylene
abbreviation: HDPE
role: light, tough, chemically resistant thermoplastic for molded, machined and extruded parts
category: polymers
type: polyolefins
summary: |
  High-density polyethylene (HDPE) is the linear, high-density form of polyethylene, a light and tough thermoplastic. A general-purpose virgin injection grade (SCG H5818J) has a density of 0.959 g/cm3 and a tensile strength at yield of 290 kg/cm2. A machining sheet grade (Weerg PE1000) gives a yield strength of 18 MPa and a melting range of 130 to 135 °C. In a UV lamp test, pure HDPE monofilament lost 66.0% of its elongation at break after 600 hours. Polyethylene in the LDEF space experiment eroded under atomic oxygen at 3.97 x 10-24 cm3 per atom, but that sample is only named polyethylene.
best_for: Light, tough, moisture-resistant plastic parts that are kept out of sunlight and out of heat
weakest_at: 'UV and heat: pure HDPE lost 66.0% of its elongation after 600 h of UV lamp ageing, and its heat-deflection temperature is 42 to 70 °C under light load'
identity:
  formula: (C2H4)n, polymer of ethylene with a -CH2-CH2- repeat unit
  cas: 9002-88-4
  source: scg-sds
  where: Section 3, polyethylene homopolymer, CAS 9002-88-4. Section 1.1 says this SDS applies to all HDPE grades made by Thai Polyethylene.
tags:
  environments: []
  stresses:
    - uv
    - atomic-oxygen
    - extreme-heat
  applications:
    - structures
    - mechanisms
properties:
  - benchmark: density
    label: Density, general-purpose HDPE injection grade H5818J
    value: 0.959
    unit: g/cm3
    scope: material
    conditions:
      grade: H5818J (HDPE, general purpose, injection molding)
      temperature: not stated
    method: ASTM D 1505, as printed in a manufacturer grade page
    status: ground
    source: scg-h5818j
    where: Physical table, row Density
  - benchmark: melt_flow_rate
    label: Melt flow rate, HDPE injection grade H5818J
    value: 18
    unit: g/10 min
    scope: material
    conditions:
      grade: H5818J
      temperature: 190 °C
      load: 2.16 kg
    method: ASTM D 1238, as printed in a manufacturer grade page
    status: ground
    note: Melt flow rate has no entry in the canonical property list, so the name melt_flow_rate is used.
    source: scg-h5818j
    where: Physical table, row Melt Flow Rate at 190 °C and 2.16 kg
  - benchmark: yield_strength
    label: Tensile strength at yield, HDPE injection grade H5818J
    value: 290
    unit: kg/cm2
    scope: material
    conditions:
      grade: H5818J (HDPE, injection molding)
      test_speed: crosshead 50 mm/min
    method: ASTM D 638, as printed in a manufacturer grade page
    status: ground
    note: Printed in kg/cm2 and not converted. 290 kg/cm2 is about 28.4 MPa (1 kgf/cm2 = 0.0980665 MPa, a unit conversion, not a source value).
    source: scg-h5818j
    where: Mechanical table, row Tensile Strength at Yield
  - benchmark: flexural_modulus
    label: Flexural modulus, HDPE injection grade H5818J
    value: 13000
    unit: kg/cm2
    scope: material
    conditions:
      grade: H5818J (HDPE, injection molding)
      temperature: not stated
    method: ASTM D 790, as printed in a manufacturer grade page
    status: ground
    source: scg-h5818j
    where: Mechanical table, row Flexural Modulus
  - benchmark: izod_impact_strength
    label: Izod impact strength, HDPE injection grade H5818J
    value: 27
    unit: J/m
    scope: material
    conditions:
      grade: H5818J
      temperature: 23 °C
      notch: as the standard specifies
    method: ASTM D 256, as printed in a manufacturer grade page
    status: ground
    note: The name izod_impact_strength is not in the canonical property list.
    source: scg-h5818j
    where: Mechanical table, row Izod Impact Strength at 23 °C
  - benchmark: density
    label: Density, HDPE machining sheet (Protolabs)
    value: 0.955
    unit: g/cm3
    scope: material
    conditions:
      grade: HDPE sheet for CNC machining, grade name not printed
      temperature: not stated
    method: ASTM D792, as printed in a manufacturer datasheet
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Density
  - benchmark: moisture_absorption
    label: Water absorption, HDPE machining sheet (Protolabs)
    value: 0.1
    bound: upper
    unit: '%'
    scope: material
    conditions:
      test: ASTM D570
      exposure: not stated on the datasheet
    method: ASTM D570, as printed in a manufacturer datasheet (the sheet prints an upper limit)
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Water Absorption
  - benchmark: max_service_temp
    label: Maximum service temperature in air, HDPE machining sheet (Protolabs)
    value: 180
    unit: °F
    scope: material
    conditions:
      environment: air
      grade: HDPE sheet for CNC machining
    method: As printed in a manufacturer datasheet; no test standard is named on the sheet
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Maximum Service Temperature, Air
  - benchmark: heat_deflection_temperature
    label: Heat deflection temperature at 264 psi, HDPE machining sheet (Protolabs)
    value: 165
    value_high: 176
    bound: range
    unit: °F
    scope: material
    conditions:
      load: 264 psi
      test: ASTM D648
    method: ASTM D648, as printed in a manufacturer datasheet (range)
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Heat Deflection Temperature at 264 psi
  - benchmark: yield_strength
    label: Tensile strength at yield, HDPE machining sheet (Protolabs)
    value: 4000
    bound: lower
    unit: psi
    scope: material
    conditions:
      test: ASTM D638
      grade: HDPE sheet for CNC machining, grade name not printed
    method: ASTM D638, as printed in a manufacturer datasheet (lower limit)
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Tensile Strength at Yield
  - benchmark: elongation
    label: Elongation at break, HDPE machining sheet (Protolabs)
    value: 400
    bound: lower
    unit: '%'
    scope: material
    conditions:
      test: ASTM D638
      grade: HDPE sheet for CNC machining, grade name not printed
    method: ASTM D638, as printed in a manufacturer datasheet (lower limit)
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Elongation @ Break
  - benchmark: flexural_modulus
    label: Flexural modulus, HDPE machining sheet (Protolabs)
    value: 174000
    value_high: 185000
    bound: range
    unit: psi
    scope: material
    conditions:
      test: ASTM D790
      grade: HDPE sheet for CNC machining, grade name not printed
    method: ASTM D790, as printed in a manufacturer datasheet (range)
    status: ground
    source: protolabs-hdpe
    where: Properties table, row Flexural Modulus
  - benchmark: yield_strength
    label: Yield strength, HDPE PE1000 sheet (Weerg)
    value: 18
    unit: MPa
    scope: material
    conditions:
      test: ISO 527
      grade: PE1000 HDPE, grade name beyond HDPE not printed
    method: ISO 527, as printed in a manufacturer datasheet
    status: ground
    source: weerg-pe
    where: Material properties, row Yield strength ISO 527
  - benchmark: elastic_modulus
    label: Elastic modulus, HDPE PE1000 sheet (Weerg)
    value: 750
    unit: MPa
    scope: material
    conditions:
      test: ISO 527
      grade: PE1000 HDPE
    method: ISO 527, as printed in a manufacturer datasheet
    status: ground
    source: weerg-pe
    where: Material properties, row Elastic modulus ISO 527
  - benchmark: elongation
    label: Elongation at break, HDPE PE1000 sheet (Weerg)
    value: 50
    bound: lower
    unit: '%'
    scope: material
    conditions:
      test: ISO 527
      grade: PE1000 HDPE
    method: ISO 527, as printed in a manufacturer datasheet (lower limit)
    status: ground
    source: weerg-pe
    where: Material properties, row Elongation at break ISO 527
  - benchmark: heat_deflection_temperature
    label: Heat deflection temperature at 0.45 MPa, HDPE PE1000 sheet (Weerg)
    value: 70
    unit: °C
    scope: material
    conditions:
      load: 0.45 MPa
      test: ISO 75
      grade: PE1000 HDPE
    method: ISO 75, as printed in a manufacturer datasheet
    status: ground
    source: weerg-pe
    where: Material properties, row HDT 0.45 MPa ISO 75
  - benchmark: heat_deflection_temperature
    label: Heat deflection temperature at 1.8 MPa, HDPE PE1000 sheet (Weerg)
    value: 42
    unit: °C
    scope: material
    conditions:
      load: 1.8 MPa
      test: ISO 75
      grade: PE1000 HDPE
    method: ISO 75, as printed in a manufacturer datasheet
    status: ground
    source: weerg-pe
    where: Material properties, row HDT 1.8 MPa ISO 75
  - benchmark: vicat_softening_temperature
    label: Vicat softening temperature, HDPE PE1000 sheet (Weerg)
    value: 80
    unit: °C
    scope: material
    conditions:
      test: ISO 306
      grade: PE1000 HDPE
    method: ISO 306, as printed in a manufacturer datasheet
    status: ground
    source: weerg-pe
    where: Material properties, row Vicat softening temperature ISO 306
  - benchmark: melting_point
    label: Melting temperature, HDPE PE1000 sheet (Weerg)
    value: 130
    value_high: 135
    bound: range
    unit: °C
    scope: material
    conditions:
      test: ISO 11357
      grade: PE1000 HDPE
    method: ISO 11357, as printed in a manufacturer datasheet (range)
    status: ground
    source: weerg-pe
    where: Material properties, row Melting temperature ISO 11357
  - benchmark: atomic_oxygen_erosion_yield
    label: Atomic-oxygen erosion yield, polyethylene on LDEF (grade not stated)
    value: 3.97
    unit: x10^-24 cm3/atom
    scope: material
    conditions:
      material_name_in_source: Polyethylene (grade, density and form not stated)
      exposure: LDEF Experiment A0114, row 9, leading edge (flight)
      fluence: 9.0e21 atoms/cm2 assumed, stated as preliminary
      uncertainty: plus or minus 0.23
    method: Erosion yield reported by the author from erosion depth (357 plus or minus 21 micrometres); the LDEF fluence is preliminary and the author warns to check the final value
    status: flight
    note: A flight result, but the source names the polymer only as polyethylene. Treat it as the nearest data for HDPE, not an HDPE-specific value. The name atomic_oxygen_erosion_yield is not in the canonical property list.
    source: ntrs-ao
    where: Table, Erosion depths and rates for polymers on LDEF, row Polyethylene (also the comparison table, prior STS value 3.32 to 3.74)
corrosion:
  - environment: Ultraviolet light (UVA-340 lamp, continuous, 50 °C, 55% relative humidity)
    headline: Pure HDPE monofilament lost 66.0% of its elongation at break and 54.5% of its breaking strength after 600 hours of UV lamp ageing.
    effect: The same test gave a 52.0% loss of yield strength. The authors describe the failure as rapid brittle failure. Carbonyl index and unsaturation rose with exposure, and the start of thermal decomposition, by TGA, fell 28 °C for pure HDPE. Adding 20% UHMWPE to the HDPE cut the elongation loss to 54.0%.
    rating: severe
    conditions:
      lamp: UVA-340 fluorescent, irradiance 0.76 W/m2 at 340 nm
      temperature: 50 °C
      humidity: 55% relative humidity
      exposure: continuous illumination, 0 to 600 h
      material: drawn HDPE monofilament with a compound antioxidant added, not an uncoated sheet
    source: pmc-uv
    where: Section 2.3 (UV ageing conditions); Results, mechanical properties (paragraph on 600 h of aging); Abstract (thermal decomposition T5%)
  - environment: Humid air and water (moisture uptake)
    headline: 'HDPE sheet takes up very little water: under 0.10% by the ASTM D570 test.'
    effect: The Protolabs datasheet describes HDPE as having low moisture absorption and gives an upper limit of 0.10% for water absorption by ASTM D570. The datasheet does not give the immersion time or the humidity, so this is a limit, not a humidity-ageing result.
    rating: low
    conditions:
      test: ASTM D570
      exposure: not stated on the datasheet
    source: protolabs-hdpe
    where: Properties table, row Water Absorption; Description
  - environment: Heat (sustained, under load)
    headline: 'HDPE softens well below its melting range under load: a heat-deflection temperature of 42 to 70 °C is printed at light loads.'
    effect: The Weerg PE1000 sheet gives a heat-deflection temperature of 70 °C at 0.45 MPa and 42 °C at 1.8 MPa, and a Vicat softening temperature of 80 °C. The Protolabs sheet gives a maximum service temperature in air of 180 °F (82 °C) and a heat-deflection temperature of 165 to 176 °F at 264 psi. No long-term thermal ageing time or retained-property figure was read for HDPE.
    rating: moderate
    conditions:
      loads: 0.45 MPa and 1.8 MPa (ISO 75); 264 psi (ASTM D648)
      standards: ISO 75, ISO 306, ASTM D648
      service_temperature: maximum in air, no time given
    source: weerg-pe
    where: Material properties, rows HDT 0.45 MPa, HDT 1.8 MPa, Vicat softening temperature; Protolabs Properties table (Maximum Service Temperature, Air)
  - environment: Oxidising and reducing chemicals, strong acids and bases
    headline: Most HDPE grades resist strong acids, strong bases and gentle oxidants and reducing agents.
    effect: 'Wikipedia says most LDPE, MDPE and HDPE grades have excellent chemical resistance: they are not attacked by strong acids or strong bases, and they resist gentle oxidants and reducing agents. The article gives no concentration, temperature or time. Crystalline samples do not dissolve at room temperature.'
    rating: low
    conditions:
      basis: qualitative statement, no concentration, temperature or time printed
    source: wiki-polyethylene
    where: Chemical resistance section
  - environment: Atomic oxygen in low-Earth-orbit-like flight exposure (LDEF tray, leading edge)
    headline: Polyethylene eroded by about 357 micrometres at the leading edge of the LDEF tray.
    effect: 'The LDEF polyethylene sample lost 357 plus or minus 21 micrometres of depth, which gives an erosion yield of 3.97 x 10-24 cm3 per atom. The same paper lists other polymers in the same range: polystyrene 4.17, PMMA 6.3 and Kapton 2.89 (x 10-24 cm3 per atom), and PTFE 0.37. Polyethylene here is not named as HDPE, and the fluence used is preliminary.'
    rating: severe
    conditions:
      fluence: 9.0e21 atoms/cm2 assumed for row 9, preliminary
      exposure: flight, LDEF Experiment A0114
      polymer: polyethylene, grade not stated
    source: ntrs-ao
    where: Table, Erosion depths and rates for polymers on LDEF; footnote on the LDEF fluence
risks:
  hazards:
    - text: The SCG HDPE safety data sheet classes the product as not hazardous under GHS and under EU CLP, with no signal word and no hazard statements.
      ghs: []
      source: scg-sds
      where: Section 2.1 (classification) and 2.2 (labelling)
    - text: Pellets on the floor are a slipping hazard, and hot polymer can cause thermal burns to the skin and eyes.
      ghs: []
      source: scg-sds
      where: Section 2.2 and 2.3 (other hazards); Section 4 (first aid, burns)
    - text: 'Dust is the hazard at processing: pneumatic conveying and mechanical handling can generate large static charges, and dust can be ignited.'
      ghs: []
      source: scg-sds
      where: Section 7.1 (precautions for safe handling)
  failure_risks:
    - mode: Softening under load at moderate temperature
      trigger: Part held under load at or near its heat-deflection temperature (42 °C at 1.8 MPa, 70 °C at 0.45 MPa)
      consequence: The part deforms or creeps under load well before its melting range of 130 to 135 °C.
      severity: moderate
      source: weerg-pe
      where: Material properties, rows HDT 1.8 MPa and HDT 0.45 MPa; Melting temperature
    - mode: Brittle failure after UV ageing
      trigger: Continuous UV exposure at 50 °C and 55% relative humidity, 600 h, drawn monofilament
      consequence: Elongation at break falls 66.0% and breaking strength 54.5%. The authors describe the failure as rapid brittle failure, and the carbonyl index rises, which means surface oxidation.
      severity: high
      source: pmc-uv
      where: Results, mechanical properties (600 h); Abstract
  side_effects:
    - text: In a fire the product gives off carbon dioxide, carbon monoxide, other organic vapours and soot.
      affects: Fire crews and the enclosure around the part
      source: scg-sds
      where: Section 5.2 (special hazards arising from the substance)
    - text: Molten material must not be hit with a direct water jet in a fire, and contaminated firefighting water must not enter the sewer.
      affects: Fire crews and the drainage system
      source: scg-sds
      where: Section 5.3 (fire fighting procedure)
  handling:
    - text: Store in a dry, cool, dust-free, well-ventilated area below 50 °C, away from heat and direct sunlight.
      source: scg-sds
      where: Section 7.2 (conditions for safe storage)
    - text: Avoid forming dust and electrically bond and ground equipment that handles pellets or powder to reduce the risk of dust explosions.
      source: scg-sds
      where: Section 7.1 and 7.2 (handling and storage)
  mitigations:
    - text: Blending 20% UHMWPE into HDPE cut the 600 h UV loss of elongation at break from 66.0% to 54.0%, and the loss of breaking strength from 54.5% to 43.7%. The authors attribute this to the UHMWPE phase, which limits surface cracking.
      source: pmc-uv
      where: Abstract; Results, mechanical properties
uses:
  - application: structures
    device: Injection-molded general parts, household products, bottle caps and closures, and toys
    example: SCG lists the H5818J injection grade for general injection parts, household products, bottle caps and closures, and toys, with good flow for high-productivity moulding.
    source: scg-h5818j
    where: Product description and application list on the grade page (H5818J)
  - application: mechanisms
    device: Machined parts such as chain guides, tanks, pipe systems and chemical containers
    example: Protolabs lists HDPE for chain guides, water storage, tanks, pipe systems, chemical containers and food cutting boards, and gives a density of 0.955 g/cm3.
    source: protolabs-hdpe
    where: Description and applications paragraph; Properties table, row Density
supply:
  - subject: Polyethylene (feedstock is ethylene; no HDPE production split was read)
    abundance: 'Not a mineral. Demand, not production: China accounts for 34% of global polyethylene demand in 2024 (Argus, all PE grades).'
    producers: []
    critical_lists: []
    recycling: SCG lists certified post-consumer recycled HDPE grades (PCRH01BN, PCRH02BW, PCRH03BB) for blow moulding. The grades are not for food contact, pharmaceutical or medical use.
    substitutes: []
    source: scg-h5818j
    where: Grade listing on the SCG product page (PCR grades); the Argus demand share is in the abundance field and is cited as argus-pe-2024
media: []
documents:
  - title: SCG Chemicals grade page, H5818J general purpose HDPE for injection molding
    type: datasheet
    url: https://www.scgchemicals.com/en/products-grade/h5818j
    year: 2026
  - title: SCG Chemicals HDPE safety data sheet (applies to all HDPE grades made by Thai Polyethylene)
    type: sds
    url: https://www.scgchemicals.com/uploads/sdsscgc-hdpeem-sds-9001-5.pdf
    year: 2026
  - title: Weerg PE1000 HDPE technical datasheet v2.1 (CNC machining)
    type: datasheet
    url: https://weerg.com/hubfs/Datasheets/Datasheets%202024/ENG/EN_Polietilene.pdf
    year: 2024
  - title: Protolabs HDPE CNC material data sheet
    type: datasheet
    url: https://www.protolabs.com/media/rkzn2wud/2026-026-cnc-material-data-sheet_hdpe.pdf
    year: 2026
  - title: Erosion rates for polymers measured on LDEF (Experiment A0114, UAH), LDEF Workshop 1991
    type: report
    url: https://ntrs.nasa.gov/api/citations/19930002806/downloads/19930002806.pdf
    year: 1991
  - title: Fishery HDPE/UHMWPE blend monofilament UV ageing study (open access, PMC)
    type: paper
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12899940/
    year: 2026
  - title: NIST Atomic Weights and Isotopic Compositions for All Elements (carbon, hydrogen)
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=ascii
    year: 2026
gaps:
  - 'No designations found: HDPE has no UNS or EN number in any source checked, and the ASTM D4976 or D3350 PE classification did not appear on a fetched page.'
  - No producer split for HDPE by country or company was read. Argus gives a demand share for all polyethylene, which is not a production share. Ethylene feedstock (naphtha or ethane) was not confirmed from a fetched page.
  - 'No HDPE-specific atomic-oxygen result: the LDEF value is for polyethylene, grade not stated. No HDPE mass-loss or outgassing (TML or CVCM) value was read.'
  - No radiation-dose, electron or proton test result for HDPE was read in a fetched page.
  - 'Environmental stress cracking (ESCR, ASTM D1693) of HDPE: the Pertachem table gives hours at 25% Igepal, but the columns are flattened, so no figure is entered.'
  - No thermal-oxidation or long-term heat-ageing time to a retained-property figure was read for HDPE. The UV figures come from a monofilament with an antioxidant added, not from a sheet or moulding.
  - Weerg PE1000 density (0,94 g/cm3) and water absorption (0,01 %, ISO 62) print a decimal comma. They were read but are not entered as properties, because the verify script does not match a comma decimal; they are recorded here. The Weerg data are for a machining sheet, grade not named.
  - Melt flow rate and Izod impact have no canonical name in the property list; melt_flow_rate and izod_impact_strength are used and noted in the properties.
  - Recythen recycled HDPE data sheet could not be opened, so recycled-grade values are not entered.
  - Flash point and auto-ignition temperature do not appear in the SCG safety data sheet text that could be extracted (section 9 gave no such figures).
sources:
  scg-h5818j:
    title: SCG Chemicals grade page, H5818J general purpose HDPE for injection molding
    url: https://www.scgchemicals.com/en/products-grade/h5818j
    kind: datasheet
    license: Manufacturer product page (cited, not reproduced)
  scg-sds:
    title: SCG Chemicals HDPE safety data sheet (applies to all HDPE grades made by Thai Polyethylene)
    url: https://www.scgchemicals.com/uploads/sdsscgc-hdpeem-sds-9001-5.pdf
    kind: datasheet
    license: Supplier safety data sheet (cited, not reproduced)
  weerg-pe:
    title: Weerg PE1000 HDPE technical datasheet v2.1 (CNC machining)
    url: https://weerg.com/hubfs/Datasheets/Datasheets%202024/ENG/EN_Polietilene.pdf
    kind: datasheet
    license: Supplier datasheet (cited, not reproduced)
  protolabs-hdpe:
    title: Protolabs HDPE CNC material data sheet
    url: https://www.protolabs.com/media/rkzn2wud/2026-026-cnc-material-data-sheet_hdpe.pdf
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  ntrs-ao:
    title: Erosion rates for polymers measured on LDEF (Experiment A0114, UAH), J. Gregory, LDEF Workshop, Langley, November 1991
    url: https://ntrs.nasa.gov/api/citations/19930002806/downloads/19930002806.pdf
    kind: report
    license: Public domain (NASA)
  pmc-uv:
    title: Fishery HDPE/UHMWPE blend monofilament UV ageing study (open access, PMC)
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12899940/
    kind: paper
    license: Open access (PMC); check the article licence before reuse
  wiki-polyethylene:
    title: Wikipedia, Polyethylene (chemical resistance and ageing sections)
    url: https://en.wikipedia.org/wiki/Polyethylene
    kind: web
    license: CC BY-SA (Wikipedia)
    note: Used for chemical resistance and for the HDPE density definition only, not for property values.
  nist-atomic-weights:
    title: NIST Atomic Weights and Isotopic Compositions for All Elements (standard atomic weight intervals for C and H)
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=ascii
    kind: database
    license: Public domain (NIST)
    note: 'Standard atomic weight intervals printed: C [12.0096, 12.0116]; H [1.00784, 1.00811]'
  argus-pe-2024:
    title: 'Argus, Polyethylene model update: 2024 takeaways'
    url: https://www.argusmedia.com/en/news-and-insights/market-opinion-and-analysis-blog/polyethylene-model-update-2024-takeaways
    kind: web
    license: Publisher article (cited, not reproduced)
    note: China accounts for 34% of global PE demand in 2024; a demand figure, not production.
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 20
  unreachable: 2
  caveats: 5
  note: 'Read by an AI assistant on 2026-10-26 from the pages named in each entry. Unreachable as readable text: the Recythen HDPE data sheet and the Shell HDPE safety data sheet. Caveats: the LDEF value is for polyethylene with no grade named; the UV figures are for a monofilament with an antioxidant; the Weerg and Protolabs sheets name no grade beyond HDPE; no HDPE production split was read; the Argus figure is demand.'
story:
  recipe:
    line: HDPE is polyethylene made from ethylene (C2H4). Its repeat unit is -CH2-CH2-, and the chains have little branching, so they pack densely. Industrial routes use Ziegler-Natta catalysts, the Phillips slurry process with silica-based catalysts, or metallocene catalysts (Wikipedia, High-density polyethylene).
    parts:
      - name: Carbon
        symbol: C
        role: Forms the backbone of each repeat unit.
      - name: Hydrogen
        symbol: H
        role: Fills the remaining bonds on the carbon backbone. The formula is (C2H4)n.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified hazardous
      lead: The SCG safety data sheet classes HDPE as not hazardous under GHS and EU CLP. The hazards are physical, from hot polymer and dust at processing.
      points:
        - label: The pellets
          line: The data sheet gives no signal word and no hazard statements. Pellets on the floor are a slipping hazard.
        - label: Molten polymer
          line: Hot polymer can cause thermal burns to skin and eyes.
        - label: Dust
          line: Pneumatic conveying can build large static charges, and dust can be ignited. Keep dust down and bond and ground the equipment.
    - title: If it fails
      lead: The failure routes are heat under load and sunlight.
      points:
        - label: Softening under load
          line: A PE1000 sheet has a heat-deflection temperature of 70 °C at 0.45 MPa and 42 °C at 1.8 MPa. The melting range is 130 to 135 °C.
        - label: UV ageing
          line: In a UV lamp test at 50 °C, pure HDPE monofilament lost 66.0% of its elongation at break in 600 hours and was described as brittle.
        - label: In a fire
          line: The product gives off carbon dioxide, carbon monoxide, organic vapours and soot.
    - title: Handling and storage
      points:
        - label: Storage
          line: Store dry, cool and dust-free below 50 °C, away from heat and direct sunlight.
        - label: Moulding
          line: The Weerg and Protolabs sheets give no drying step. Dry the resin as the grade's own processing sheet says.
  why: 'High-density polyethylene is the light, tough and chemically resistant form of polyethylene. Its linear chains pack densely, which gives a density of 0.959 g/cm3 for the virgin injection grade. Its weaknesses are heat and sunlight: it softens under load well below its melting range, and UV exposure breaks the surface down. Where those are not the design limits, it is a light, moulded or machined material.'
  uses:
    - where: Injection-moulded parts
      line: The SCG H5818J grade is a general-purpose injection HDPE for household products, bottle caps and closures, and toys. It has a density of 0.959 g/cm3 and a tensile strength at yield of 290 kg/cm2.
    - where: Machined parts
      line: Protolabs lists HDPE sheet for chain guides, tanks, pipe systems and chemical containers. Its sheet has a density of 0.955 g/cm3, a yield strength above 4,000 psi and an elongation at break above 400%.
  can_do:
    - label: Density
      value: 0.959 g/cm3
      benchmark: density
      line: The virgin injection grade H5818J has a density of 0.959 g/cm3 (ASTM D 1505). A machining sheet is printed at 0.955 g/cm3 (ASTM D792).
    - label: Yield strength
      value: 290 kg/cm2
      benchmark: yield_strength
      line: H5818J gives a tensile strength at yield of 290 kg/cm2 (about 28 MPa, a unit conversion). The PE1000 sheet gives 18 MPa (ISO 527).
    - label: Heat
      value: 70 °C at 0.45 MPa
      benchmark: heat_deflection_temperature
      line: Heat-deflection temperature is 70 °C at 0.45 MPa and 42 °C at 1.8 MPa (ISO 75) for the PE1000 sheet. The Vicat softening temperature is 80 °C.
  compare: Within this profile, the virgin injection grade (0.959 g/cm3) and the machining sheet (0.955 g/cm3) give similar densities, and the machining sheet's yield strength (18 MPa) is lower than the injection grade's (about 28 MPa, converted from 290 kg/cm2). The sheets give a heat-deflection temperature of 42 to 70 °C under light load. Without stabilisers or a blend, UV exposure degrades HDPE quickly, so the comparison with other polymers in the collection depends on the UV limit the part must meet.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Yield strength
      benchmark: yield_strength
    - label: Maximum service temperature
      benchmark: max_service_temp
  handling:
    - The SCG safety data sheet gives no hazard classification. Use dust control, and bond and ground equipment that moves pellets.
    - Keep the material dry and below 50 °C, away from heat and direct sunlight.
    - Hot polymer causes burns; keep the molten material away from skin and eyes.
  good_for:
    - Light parts. The virgin injection grade is 0.959 g/cm3 and the machining sheet 0.955 g/cm3.
    - Moisture resistance. The machining sheet absorbs under 0.10% water by ASTM D570.
    - Chemical resistance. Most HDPE grades are not attacked by strong acids or bases.
  watch_out:
    - 'UV: 66.0% loss of elongation after 600 h of lamp ageing for pure monofilament. Stabilise or shield the part.'
    - 'Heat: 42 °C at 1.8 MPa and 70 °C at 0.45 MPa for the PE1000 sheet, so a loaded part softens far below its melting range.'
    - 'Space: LDEF eroded polyethylene by 357 micrometres. HDPE was not measured on its own, and no outgassing value was read.'
  verdict: HDPE is the practical, light and chemically resistant choice for rigid parts at room temperature. It is a poor choice for loaded parts in sunlight or heat. The sourced values are two virgin or machining HDPE grades, one set of UV ageing data for monofilament, and one LDEF flight result for polyethylene, which is not named as HDPE.