Materials / Compare
Plastic PEEK vs. Plastic UHMWPE
Compare Plastic PEEK vs. Plastic UHMWPE strength, stiffness, weight and thermal properties.
| Try it on a partA bracket to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | 98MPasourcetypical, tensile yield | 20MPasourcetypical, tensile stress at yield ISO 527, 50 mm/min |
| Ultimate tensile strength | not sourced | 43MPasourcetypical, tensile stress at break ISO 527, 50 mm/min |
| Compressive strength | 125MPasourcetypical, 23 C | not sourced |
| Flexural strength | 165MPasourcetypical, flexural stress at yield, 23 C | not sourced |
| Elongation at break | 25%sourcetypical, at break | 465%sourcetypical, nominal elongation at break ISO 527 |
| Young's modulus (stiffness) | 4GPasourcetypical (nominal) | 0.66GPasourcetypical, tensile modulus ISO 527, 1 mm/min |
| Density | 1,300kg/m³sourcetypical (crystalline) | 930kg/m³sourcetypical |
| Strength to weight | 75.4kN·m/kg3.51x higher | 21.5kN·m/kg |
| Stiffness to weight | 3.08MN·m/kg4.34x higher | 0.71MN·m/kg |
| Poisson's ratio | 0.38sourcetypical | not sourced |
| Shear modulus | 1.45GPa | not sourced |
| Bulk modulus | 5.56GPa | not sourced |
| Speed of sound | 1,754m/s | 842m/s |
| Thermal | ||
| Thermal conductivity | 0.29W/m·Ksourcetypical, average, 23 C | 0.4W/m·Ksourcetypical, unfilled (narrative value, generic Celanese UHMWPE) |
| Thermal expansion | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) | 200µm/m·Ksourcetypical, 20 to 100 °C (generic Celanese UHMWPE) |
| 100 mm part over a 50 °C swing | 275µm growth3.64x less | 1,000µm growth |
| Specific heat | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) | not sourced |
| Heats up and cools (diffusivity) | 0.101mm²/s | not sourced |
| Thermal shock resistance | 80.1W/m | not sourced |
| Melting point | 343°Csourcetypical, DSC | 130–138°CsourceDSC 10 K/min |
| Glass transition | 143°Csourceonset (midpoint 150 C) | not sourced |
| Max service temperature | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) | 80°Csourcerecommended max constant operating temperature |
| Values for | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) | Celanese GUR 4120 (avg. molecular weight 4.7x10^6 g/mol), typical values on compression-molded specimens; CTE and thermal conductivity from Celanese's generic UHMWPE guide (grade not named) |
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Plastic PEEK stronger than Plastic UHMWPE?
Plastic PEEK is stronger: its yield strength is 98 MPa against 20 MPa for Plastic UHMWPE (4.9x).
Which is lighter, Plastic PEEK or Plastic UHMWPE?
Plastic UHMWPE is lighter: 930 kg/m³ against 1,300 kg/m³ for Plastic PEEK.
Which is stiffer, Plastic PEEK or Plastic UHMWPE?
Plastic PEEK is stiffer: Young's modulus 4 GPa against 0.66 GPa for Plastic UHMWPE, so the same part in Plastic PEEK deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Plastic UHMWPE?
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 UHMWPE |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 4.34x heavier |
| Stiff beam (bending) | lighter | 1.76x heavier |
| Stiff panel or plate | lighter | 30% heavier |
| Strong rod or tie | lighter | 3.51x heavier |
| Strong beam | lighter | 2.06x heavier |
| Strong panel or plate | lighter | 1.58x 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 conducts heat better, Plastic PEEK or Plastic UHMWPE?
Plastic UHMWPE conducts heat better: 0.4 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 200 µm/m·K for Plastic UHMWPE.