Materials / Compare
Plastic PEEK vs. Stainless 304
Compare Plastic PEEK vs. Stainless 304 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 | 241MPasourcetypical, annealed, 70 °F (21 °C) |
| Ultimate tensile strength | not sourced | 586MPasourcetypical, annealed, 70 °F (21 °C) |
| 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 | 55%sourcetypical, annealed, in 2 in. (50.8 mm) |
| Young's modulus (stiffness) | 4GPasourcetypical (nominal) | 193GPasourcetypical, in tension |
| Density | 1,300kg/m³sourcetypical (crystalline) | 8,030kg/m³sourcetypical |
| Strength to weight | 75.4kN·m/kg2.51x higher | 30kN·m/kg |
| Stiffness to weight | 3.08MN·m/kg | 24MN·m/kg7.81x higher |
| Poisson's ratio | 0.38sourcetypical | 0.3sourcedesign value (structural stainless steels) |
| Shear modulus | 1.45GPa | 74.2GPa51.2x stiffer in shear |
| Bulk modulus | 5.56GPa | 161GPa |
| Speed of sound | 1,754m/s | 4,903m/s |
| Thermal | ||
| Thermal conductivity | 0.29W/m·Ksourcetypical, average, 23 C | 16.2W/m·Ksourceat 100 °C |
| Thermal expansion | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) | 16.9µm/m·Ksourcemean, 0–100 °C |
| 100 mm part over a 50 °C swing | 275µm growth | 84.5µm growth3.25x less |
| Specific heat | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) | 500J/kg·Ksourcemean, 0–100 °C |
| Heats up and cools (diffusivity) | 0.101mm²/s | 4.03mm²/s39.8x faster |
| Thermal shock resistance | 80.1W/m | 838W/m10.5x more resistant |
| Melting point | 343°Csourcetypical, DSC | 1,399–1,454°Csourcemelting range |
| Glass transition | 143°Csourceonset (midpoint 150 C) | not sourced |
| Max service temperature | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) | 899°Csourcecontinuous, oxidation (scaling) limit in air |
| Values for | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) | Type 304, annealed flat-rolled (Cleveland-Cliffs 304/304L Product Data Bulletin, May 2021); Poisson's ratio from the Nickel Institute/SCI structural stainless design manual |
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 304?
Stainless 304 is stronger: its yield strength is 241 MPa against 98 MPa for Plastic PEEK (2.46x).
Which is lighter, Plastic PEEK or Stainless 304?
Plastic PEEK is lighter: 1,300 kg/m³ against 8,030 kg/m³ for Stainless 304.
Which is stiffer, Plastic PEEK or Stainless 304?
Stainless 304 is stiffer: Young's modulus 193 GPa against 4 GPa for Plastic PEEK, so the same part in Stainless 304 deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Stainless 304?
For the same stiffness or strength: Plastic PEEK is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Stainless 304 is lighter for a stiff rod or tie (tension), stiff beam (bending).
| Part that must be | Plastic PEEK | Stainless 304 |
|---|---|---|
| Stiff rod or tie (tension) | 7.81x heavier | lighter |
| Stiff beam (bending) | 12% heavier | lighter |
| Stiff panel or plate | lighter | 1.7x heavier |
| Strong rod or tie | lighter | 2.51x heavier |
| Strong beam | lighter | 3.39x heavier |
| Strong panel or plate | lighter | 3.94x 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 304?
Stainless 304 conducts heat better: 16.2 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Stainless 304 expands less: 16.9 µm/m·K against 55 µm/m·K for Plastic PEEK.