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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Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07)
Plastic Polycarbonate
Covestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical values
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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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Makrolon 2405 Technical Data SheetCovestroPlastic Polycarbonate · Yield strength: typical, tensile yieldPlastic Polycarbonate · Ultimate tensile strength: typical, stress at breakPlastic Polycarbonate · Flexural strength: typical, flexural strengthPlastic Polycarbonate · Elongation at break: typical, strain at breakPlastic Polycarbonate · Young's modulus (stiffness): typicalPlastic Polycarbonate · Density: typicalPlastic Polycarbonate · Thermal conductivity: typical, through-plane, 23 CPlastic Polycarbonate · Thermal expansion: typical, 23-55 C, parallel and normalPlastic Polycarbonate · Glass transition: typical, DSC 10 C/minPlastic Polycarbonate · Max service temperature: UL 746B RTI, tensile strength, 1.5 mm
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VICTREX PEEK for Use in Fluid Management (2020)VictrexPlastic PEEK · Poisson's ratio: typical
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Engineering Polymers Part and Mold Design: Thermoplastics, A Design GuideCovestroarchived copyPlastic Polycarbonate · Poisson's ratio: typical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1)
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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)
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Makrolon 2405 Data Sheet, ASTM valuesBayer MaterialSciencearchived copyPlastic Polycarbonate · Specific heat: typical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766
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 PEEK stronger than Plastic Polycarbonate?
Plastic PEEK is stronger: its yield strength is 98 MPa against 65 MPa for Plastic Polycarbonate (1.51x).
Which is lighter, Plastic PEEK or Plastic Polycarbonate?
Plastic Polycarbonate is lighter: 1,200 kg/m³ against 1,300 kg/m³ for Plastic PEEK.
Which is stiffer, Plastic PEEK or Plastic Polycarbonate?
Plastic PEEK is stiffer: Young's modulus 4 GPa against 2.4 GPa for Plastic Polycarbonate, so the same part in Plastic PEEK deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Plastic Polycarbonate?
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 PEEK
Plastic Polycarbonate
Stiff rod or tie (tension)
lighter
1.54x heavier
Stiff beam (bending)
lighter
19% heavier
Stiff panel or plate
lighter
9% heavier
Strong rod or tie
lighter
39% heavier
Strong beam
lighter
21% heavier
Strong panel or plate
lighter
13% heavier
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).
Which is more ductile, Plastic PEEK or Plastic Polycarbonate?
Plastic Polycarbonate stretches further before it breaks: 125% elongation at break against 25% for Plastic PEEK.
Thermal
Which conducts heat better, Plastic PEEK or Plastic Polycarbonate?
Plastic PEEK conducts heat better: 0.29 W/m·K against 0.2 W/m·K for Plastic Polycarbonate.
Which expands less with temperature?
Plastic PEEK expands less: 55 µm/m·K against 65 µm/m·K for Plastic Polycarbonate.