Materials / Compare
Iron vs. Plastic PEEK
Compare Iron vs. Plastic PEEK 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 | 186MPasourcetypical (0.2% YS), hot rolled + SRA/recrystallization anneal | 98MPasourcetypical, tensile yield |
| Ultimate tensile strength | 290MPasourcetypical, SRA/recrystallization anneal | not sourced |
| Compressive strength | not sourced | 125MPasourcetypical, 23 C |
| Flexural strength | not sourced | 165MPasourcetypical, flexural stress at yield, 23 C |
| Elongation at break | 38%sourcetypical, gauge 4D0 | 25%sourcetypical, at break |
| Young's modulus (stiffness) | 207GPasourcetypical, after SRA/recrystallization anneal | 4GPasourcetypical (nominal) |
| Density | 7,860kg/m³sourcetypical | 1,300kg/m³sourcetypical (crystalline) |
| Strength to weight | 23.7kN·m/kg | 75.4kN·m/kg3.19x higher |
| Stiffness to weight | 26.3MN·m/kg8.56x higher | 3.08MN·m/kg |
| Poisson's ratio | 0.282sourceNIST critically evaluated best value (polycrystalline iron) | 0.38sourcetypical |
| Shear modulus | 80.7GPa55.7x stiffer in shear | 1.45GPa |
| Bulk modulus | 158GPa | 5.56GPa |
| Speed of sound | 5,132m/s | 1,754m/s |
| Thermal | ||
| Thermal conductivity | 73.2W/m·Ksourcetypical at 20 °C | 0.29W/m·Ksourcetypical, average, 23 C |
| Thermal expansion | 13.7µm/m·Ksourcemean, 20-399 °C | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) |
| 100 mm part over a 50 °C swing | 68.5µm growth4.01x less | 275µm growth |
| Specific heat | 450J/kg·Ksourcetypical | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) |
| Heats up and cools (diffusivity) | 20.7mm²/s204x faster | 0.101mm²/s |
| Thermal shock resistance | 3,447W/m43x more resistant | 80.1W/m |
| Melting point | 1,532°Csourcetypical | 343°Csourcetypical, DSC |
| Glass transition | not sourced | 143°Csourceonset (midpoint 150 C) |
| Max service temperature | not sourced | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) |
| Values for | Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal. | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) |
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 Iron stronger than Plastic PEEK?
Iron is stronger: its yield strength is 186 MPa against 98 MPa for Plastic PEEK (1.9x).
Which is lighter, Iron or Plastic PEEK?
Plastic PEEK is lighter: 1,300 kg/m³ against 7,860 kg/m³ for Iron.
Which is stiffer, Iron or Plastic PEEK?
Iron is stiffer: Young's modulus 207 GPa against 4 GPa for Plastic PEEK, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Iron or Plastic PEEK?
For the same stiffness or strength: Iron is lighter for a stiff rod or tie (tension), stiff beam (bending); Plastic PEEK is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Iron | Plastic PEEK |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 8.56x heavier |
| Stiff beam (bending) | lighter | 19% heavier |
| Stiff panel or plate | 1.62x heavier | lighter |
| Strong rod or tie | 3.19x heavier | lighter |
| Strong beam | 3.94x heavier | lighter |
| Strong panel or plate | 4.39x 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).
Which conducts heat better, Iron or Plastic PEEK?
Iron conducts heat better: 73.2 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Iron expands less: 13.7 µm/m·K against 55 µm/m·K for Plastic PEEK.