Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources5 documents: LyondellBasell, Victrex, INEOS Olefins & Polymers USA
Plastic HDPE
LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values
Plastic PEEK
Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07)
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Hostalen 23050 B Product DataLyondellBasellPlastic HDPE · Yield strength: typical, tensile stress at yield 23 °C, 50 mm/min ISO 527Plastic HDPE · Young's modulus (stiffness): typical, tensile modulus 23 °C ISO 527Plastic HDPE · Density: typical, ISO 1183
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VICTREX PEEK 450G Technical Data SheetVictrexPlastic PEEK · Yield strength: typical, tensile yieldPlastic PEEK · Compressive strength: typical, 23 CPlastic PEEK · Flexural strength: typical, flexural stress at yield, 23 CPlastic PEEK · Elongation at break: typical, at breakPlastic PEEK · Young's modulus (stiffness): typical (nominal)Plastic PEEK · Density: typical (crystalline)Plastic PEEK · Thermal conductivity: typical, average, 23 CPlastic PEEK · Thermal expansion: average of flow/cross-flow, below Tg (<143 C)Plastic PEEK · Melting point: typical, DSCPlastic PEEK · Glass transition: onset (midpoint 150 C)Plastic PEEK · Max service temperature: UL 746B RTI, mechanical strength (continuous use index)
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Typical Engineering Properties of High Density PolyethyleneINEOS Olefins & Polymers USAarchived copyPlastic HDPE · Poisson's ratio: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal conductivity: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal expansion: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Specific heat: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)
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VICTREX PEEK for Use in Fluid Management (2020)VictrexPlastic PEEK · Poisson's ratio: typical
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VICTREX PEEK 450G Technical Data Sheet (2012)Victrexarchived copyPlastic PEEK · Specific heat: typical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012)
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Plastic HDPE stronger than Plastic PEEK?
Plastic PEEK is stronger: its yield strength is 98 MPa against 24 MPa for Plastic HDPE (4.08x).
Which is lighter, Plastic HDPE or Plastic PEEK?
Plastic HDPE is lighter: 950 kg/m³ against 1,300 kg/m³ for Plastic PEEK.
Which is stiffer, Plastic HDPE or Plastic PEEK?
Plastic PEEK is stiffer: Young's modulus 4 GPa against 0.9 GPa for Plastic HDPE, so the same part in Plastic PEEK deflects less under the same load.
Which is lighter for the same job, Plastic HDPE or Plastic PEEK?
For the same stiffness or strength: Plastic PEEK is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Plastic HDPE
Plastic PEEK
Stiff rod or tie (tension)
3.25x heavier
lighter
Stiff beam (bending)
1.54x heavier
lighter
Stiff panel or plate
20% heavier
lighter
Strong rod or tie
2.98x heavier
lighter
Strong beam
1.87x heavier
lighter
Strong panel or plate
48% heavier
lighter
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Thermal
Which conducts heat better, Plastic HDPE or Plastic PEEK?
Plastic HDPE conducts heat better: 0.445 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Plastic PEEK expands less: 55 µm/m·K against 120 µm/m·K for Plastic HDPE.