Materials / Compare
Plastic PEEK vs. Stainless 17-4PH
Compare Plastic PEEK vs. Stainless 17-4PH 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 | 1,275MPasourcetypical, transverse, sheet/strip |
| Ultimate tensile strength | not sourced | 1,379MPasourcetypical, transverse, sheet/strip |
| 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 | 9%sourcetypical, transverse, in 2 in. (50.8 mm) |
| Young's modulus (stiffness) | 4GPasourcetypical (nominal) | 197GPasourceH 900 |
| Density | 1,300kg/m³sourcetypical (crystalline) | 7,800kg/m³sourceH 900 |
| Strength to weight | 75.4kN·m/kg | 163kN·m/kg2.17x higher |
| Stiffness to weight | 3.08MN·m/kg | 25.3MN·m/kg8.21x higher |
| Poisson's ratio | 0.38sourcetypical | 0.272sourceH 900 (column) |
| Shear modulus | 1.45GPa | 77.4GPa53.4x stiffer in shear |
| Bulk modulus | 5.56GPa | 144GPa |
| Speed of sound | 1,754m/s | 5,026m/s |
| Thermal | ||
| Thermal conductivity | 0.29W/m·Ksourcetypical, average, 23 C | 17.9W/m·Ksourceat 149 °C (300 °F), H 900 |
| Thermal expansion | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) | 10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900 |
| 100 mm part over a 50 °C swing | 275µm growth | 54µm growth5.09x less |
| Specific heat | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) | 460J/kg·Ksourcemean, 0–100 °C, H 900 |
| Heats up and cools (diffusivity) | 0.101mm²/s | 4.99mm²/s49.2x faster |
| Thermal shock resistance | 80.1W/m | 7,809W/m97.5x more resistant |
| Melting point | 343°Csourcetypical, DSC | not sourced |
| Glass transition | 143°Csourceonset (midpoint 150 C) | not sourced |
| Max service temperature | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) | 316°Csourcestrength-retention limit (not oxidation) |
| Values for | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) | Cleveland-Cliffs 17-4 PH, Condition H 900, sheet/strip, transverse (Product Data Bulletin, May 2021) |
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 Stainless 17-4PH?
Stainless 17-4PH is stronger: its yield strength is 1,275 MPa against 98 MPa for Plastic PEEK (13x).
Which is lighter, Plastic PEEK or Stainless 17-4PH?
Plastic PEEK is lighter: 1,300 kg/m³ against 7,800 kg/m³ for Stainless 17-4PH.
Which is stiffer, Plastic PEEK or Stainless 17-4PH?
Stainless 17-4PH is stiffer: Young's modulus 197 GPa against 4 GPa for Plastic PEEK, so the same part in Stainless 17-4PH deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Stainless 17-4PH?
For the same stiffness or strength: Plastic PEEK is lighter for a stiff panel or plate, strong beam, strong panel or plate; Stainless 17-4PH is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.
| Part that must be | Plastic PEEK | Stainless 17-4PH |
|---|---|---|
| Stiff rod or tie (tension) | 8.21x heavier | lighter |
| Stiff beam (bending) | 17% heavier | lighter |
| Stiff panel or plate | lighter | 1.64x heavier |
| Strong rod or tie | 2.17x heavier | lighter |
| Strong beam | lighter | 8% heavier |
| Strong panel or plate | lighter | 1.66x 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 Stainless 17-4PH?
Stainless 17-4PH conducts heat better: 17.9 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Stainless 17-4PH expands less: 10.8 µm/m·K against 55 µm/m·K for Plastic PEEK.