Materials / Compare
Plastic PBT GF30 vs. Steel AISI 1018
Compare Plastic PBT GF30 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 | not given (tensile used) | 372MPasourceproducer-stated, cold drawn |
| Ultimate tensile strength | 140MPasourcestress at break, 23 °C | 441MPasourceproducer-stated, cold drawn |
| Flexural strength | 210MPasourcetypical, 23 °C | not sourced |
| Elongation at break | 3%sourcestrain at break, 23 °C | 15%sourcein 2 in (50.8 mm) |
| Young's modulus (stiffness) | 9.8GPasourcetypical, 23 °C | 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 | 1,530kg/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 | 91.5kN·m/kg1.93x higher | 47.3kN·m/kg |
| Stiffness to weight | 6.41MN·m/kg | 25.4MN·m/kg3.97x higher |
| Poisson's ratio | not sourced | 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 | not sourced | 75.7GPa |
| Bulk modulus | not sourced | 185GPa |
| Speed of sound | 2,531m/s | 5,043m/s |
| Thermal | ||
| Thermal conductivity | 0.27W/m·Ksourcetypical (DIN 52612-1) | 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 | 25µm/m·Ksourcelongitudinal (flow), mean 23-55 °C | 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 | 125µm growth | 60µm growth2.08x less |
| Specific heat | 1,050J/kg·Ksourcetypical, 23 °C | 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) | 0.168mm²/s | 13.6mm²/s80.8x faster |
| Thermal shock resistance | not sourced | 5,473W/m |
| Melting point | 223°CsourceDSC (ISO 11357) | not sourced |
| Max service temperature | 205°CsourceHDT 1.8 MPa | not sourced |
| Values for | BASF Ultradur B 4300 G6 (PBT, 30% glass fibre), injection moulding grade; product information sheet 09/2026, typical values for uncoloured product at 23 °C. | 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 PBT GF30 stronger than Steel AISI 1018?
Steel AISI 1018 is stronger: its yield strength is 372 MPa against tensile strength 140 MPa for Plastic PBT GF30 (2.66x).
Which is lighter, Plastic PBT GF30 or Steel AISI 1018?
Plastic PBT GF30 is lighter: 1,530 kg/m³ against 7,861 kg/m³ for Steel AISI 1018.
Which is stiffer, Plastic PBT GF30 or Steel AISI 1018?
Steel AISI 1018 is stiffer: Young's modulus 200 GPa against 9.8 GPa for Plastic PBT GF30, so the same part in Steel AISI 1018 deflects less under the same load.
Which is lighter for the same job, Plastic PBT GF30 or Steel AISI 1018?
For the same stiffness or strength: Plastic PBT GF30 is lighter for a stiff beam (bending), 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).
| Part that must be | Plastic PBT GF30 | Steel AISI 1018 |
|---|---|---|
| Stiff rod or tie (tension) | 3.97x heavier | lighter |
| Stiff beam (bending) | lighter | 14% heavier |
| Stiff panel or plate | lighter | 1.88x heavier |
| Strong rod or tie | lighter | 1.93x heavier |
| Strong beam | lighter | 2.68x heavier |
| Strong panel or plate | lighter | 3.15x 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 PBT GF30 or Steel AISI 1018?
Steel AISI 1018 conducts heat better: 51.9 W/m·K against 0.27 W/m·K for Plastic PBT GF30.
Which expands less with temperature?
Steel AISI 1018 expands less: 12 µm/m·K against 25 µm/m·K for Plastic PBT GF30.