Materials / Compare
Plastic Polycarbonate vs. Steel AISI 1018
Compare Plastic Polycarbonate vs. Steel AISI 1018 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 | 65MPasourcetypical, tensile yield | 372MPasourceproducer-stated, cold drawn |
| Ultimate tensile strength | 65MPasourcetypical, stress at break | 441MPasourceproducer-stated, cold drawn |
| Flexural strength | 97MPasourcetypical, flexural strength | not sourced |
| Elongation at break | 125%sourcetypical, strain at break | 15%sourcein 2 in (50.8 mm) |
| Young's modulus (stiffness) | 2.4GPasourcetypical | 200GPasourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Density | 1,200kg/m³sourcetypical | 7,861kg/m³sourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Strength to weight | 54.2kN·m/kg14% higher | 47.3kN·m/kg |
| Stiffness to weight | 2MN·m/kg | 25.4MN·m/kg12.7x higher |
| Poisson's ratio | 0.38sourcetypical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1) | 0.32sourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Shear modulus | 0.87GPa | 75.7GPa87.1x stiffer in shear |
| Bulk modulus | 3.33GPa | 185GPa |
| Speed of sound | 1,414m/s | 5,043m/s |
| Thermal | ||
| Thermal conductivity | 0.2W/m·Ksourcetypical, through-plane, 23 C | 51.9W/m·Ksourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Thermal expansion | 65µm/m·Ksourcetypical, 23-55 C, parallel and normal | 12µm/m·Ksourcebase material: unalloyed carbon steel, Ovako family table (S275JR, 'none alloyed structural steels', C <= 0.21%); mean 20-300 °C |
| 100 mm part over a 50 °C swing | 325µm growth | 60µm growth5.42x less |
| Specific heat | 1,172J/kg·Ksourcetypical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766 | 486J/kg·Ksourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Heats up and cools (diffusivity) | 0.142mm²/s | 13.6mm²/s95.5x faster |
| Thermal shock resistance | 51.7W/m | 5,473W/m106x more resistant |
| Glass transition | 144°Csourcetypical, DSC 10 C/min | not sourced |
| Max service temperature | 125°CsourceUL 746B RTI, tensile strength, 1.5 mm | not sourced |
| Values for | Covestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical values | AISI 1018 cold drawn bar (Niagara LaSalle, cold-finished bar producer) |
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 Polycarbonate stronger than Steel AISI 1018?
Steel AISI 1018 is stronger: its yield strength is 372 MPa against 65 MPa for Plastic Polycarbonate (5.72x).
Which is lighter, Plastic Polycarbonate or Steel AISI 1018?
Plastic Polycarbonate is lighter: 1,200 kg/m³ against 7,861 kg/m³ for Steel AISI 1018.
Which is stiffer, Plastic Polycarbonate or Steel AISI 1018?
Steel AISI 1018 is stiffer: Young's modulus 200 GPa against 2.4 GPa for Plastic Polycarbonate, so the same part in Steel AISI 1018 deflects less under the same load.
Which is lighter for the same job, Plastic Polycarbonate or Steel AISI 1018?
For the same stiffness or strength: Plastic Polycarbonate is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Steel AISI 1018 is lighter for a stiff rod or tie (tension), stiff beam (bending).
| Part that must be | Plastic Polycarbonate | Steel AISI 1018 |
|---|---|---|
| Stiff rod or tie (tension) | 12.7x heavier | lighter |
| Stiff beam (bending) | 39% heavier | lighter |
| Stiff panel or plate | lighter | 1.5x heavier |
| Strong rod or tie | lighter | 14% heavier |
| Strong beam | lighter | 2.05x heavier |
| Strong panel or plate | lighter | 2.74x 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 Polycarbonate or Steel AISI 1018?
Steel AISI 1018 conducts heat better: 51.9 W/m·K against 0.2 W/m·K for Plastic Polycarbonate.
Which expands less with temperature?
Steel AISI 1018 expands less: 12 µm/m·K against 65 µm/m·K for Plastic Polycarbonate.