Materials / Compare
Plastic Polypropylene vs. Steel
Compare Plastic Polypropylene vs. Steel 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 | 33MPasourcetypical, tensile stress at yield ISO 527 | 385MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISC |
| Ultimate tensile strength | not sourced | 505MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey) |
| Elongation at break | not sourced | not sourced |
| Young's modulus (stiffness) | 1.45GPasourcetypical, tensile modulus ISO 527 | 200GPasourcedesign value (AISC 360-16) |
| Density | 900kg/m³sourcetypical, 23 °C ISO 1183-1 | 7,850kg/m³sourcenominal (constructional data) |
| Strength to weight | 36.7kN·m/kg | 49kN·m/kg34% higher |
| Stiffness to weight | 1.61MN·m/kg | 25.5MN·m/kg15.8x higher |
| Poisson's ratio | 0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) | 0.3sourcedesign value (AISC 360-16 Commentary) |
| Shear modulus | 0.511GPa | 76.9GPa151x stiffer in shear |
| Bulk modulus | 3.02GPa | 167GPa |
| Speed of sound | 1,269m/s | 5,048m/s |
| Thermal | ||
| Thermal conductivity | 0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) | 48W/m·Ksourcenominal at 20 °C |
| Thermal expansion | 80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) | 12µm/m·Ksourcenominal (constructional data, no temperature range stated) |
| 100 mm part over a 50 °C swing | 450µm growth | 60µm growth7.5x less |
| Specific heat | not sourced | 460–480J/kg·Ksourcebase material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C |
| Heats up and cools (diffusivity) | not sourced | 13mm²/s |
| Thermal shock resistance | 28.6W/m | 5,390W/m188x more resistant |
| Max service temperature | 90°CsourceHDT 0.45 MPa (ISO 75B), unannealed | not sourced |
| Values for | LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values | Generic structural steel, cited as ASTM A992 (the current US structural grade): ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards. |
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 Polypropylene stronger than Steel?
Steel is stronger: its yield strength is 385 MPa against 33 MPa for Plastic Polypropylene (11.7x).
Which is lighter, Plastic Polypropylene or Steel?
Plastic Polypropylene is lighter: 900 kg/m³ against 7,850 kg/m³ for Steel.
Which is stiffer, Plastic Polypropylene or Steel?
Steel is stiffer: Young's modulus 200 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Steel deflects less under the same load.
Which is lighter for the same job, Plastic Polypropylene or Steel?
For the same stiffness or strength: Plastic Polypropylene is lighter for a stiff panel or plate, strong beam, strong panel or plate; Steel is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.
| Part that must be | Plastic Polypropylene | Steel |
|---|---|---|
| Stiff rod or tie (tension) | 15.8x heavier | lighter |
| Stiff beam (bending) | 35% heavier | lighter |
| Stiff panel or plate | lighter | 1.69x heavier |
| Strong rod or tie | 34% heavier | lighter |
| Strong beam | lighter | 1.7x heavier |
| Strong panel or plate | lighter | 2.55x 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 Polypropylene or Steel?
Steel conducts heat better: 48 W/m·K against 0.195 W/m·K for Plastic Polypropylene.
Which expands less with temperature?
Steel expands less: 12 µm/m·K against 90 µm/m·K for Plastic Polypropylene.