Materials / Compare
Plastic PEEK vs. Plastic Polypropylene
Compare Plastic PEEK vs. Plastic Polypropylene 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 | 33MPasourcetypical, tensile stress at yield ISO 527 |
| Ultimate tensile strength | not sourced | not sourced |
| 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 | not sourced |
| Young's modulus (stiffness) | 4GPasourcetypical (nominal) | 1.45GPasourcetypical, tensile modulus ISO 527 |
| Density | 1,300kg/m³sourcetypical (crystalline) | 900kg/m³sourcetypical, 23 °C ISO 1183-1 |
| Strength to weight | 75.4kN·m/kg2.06x higher | 36.7kN·m/kg |
| Stiffness to weight | 3.08MN·m/kg1.91x higher | 1.61MN·m/kg |
| Poisson's ratio | 0.38sourcetypical | 0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| Shear modulus | 1.45GPa2.84x stiffer in shear | 0.511GPa |
| Bulk modulus | 5.56GPa | 3.02GPa |
| Speed of sound | 1,754m/s | 1,269m/s |
| Thermal | ||
| Thermal conductivity | 0.29W/m·Ksourcetypical, average, 23 C | 0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| Thermal expansion | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) | 80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| 100 mm part over a 50 °C swing | 275µm growth1.64x less | 450µm 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/m2.8x more resistant | 28.6W/m |
| 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) | 90°CsourceHDT 0.45 MPa (ISO 75B), unannealed |
| Values for | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) | LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values |
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 Polypropylene?
Plastic PEEK is stronger: its yield strength is 98 MPa against 33 MPa for Plastic Polypropylene (2.97x).
Which is lighter, Plastic PEEK or Plastic Polypropylene?
Plastic Polypropylene is lighter: 900 kg/m³ against 1,300 kg/m³ for Plastic PEEK.
Which is stiffer, Plastic PEEK or Plastic Polypropylene?
Plastic PEEK is stiffer: Young's modulus 4 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Plastic PEEK deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Plastic Polypropylene?
For the same stiffness or strength: Plastic PEEK is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam, strong panel or plate; Plastic Polypropylene is lighter for a stiff panel or plate.
| Part that must be | Plastic PEEK | Plastic Polypropylene |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 1.91x heavier |
| Stiff beam (bending) | lighter | 15% heavier |
| Stiff panel or plate | 3% heavier | lighter |
| Strong rod or tie | lighter | 2.06x heavier |
| Strong beam | lighter | 43% heavier |
| Strong panel or plate | lighter | 19% 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 Polypropylene?
Plastic PEEK conducts heat better: 0.29 W/m·K against 0.195 W/m·K for Plastic Polypropylene.
Which expands less with temperature?
Plastic PEEK expands less: 55 µm/m·K against 90 µm/m·K for Plastic Polypropylene.