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Plastic Polycarbonate vs. Steel AISI 1045

Compare Plastic Polycarbonate vs. Steel AISI 1045 strength, stiffness, weight and thermal properties.

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Plastic PolycarbonateBulk polymer (molded or machined)
Steel AISI 1045Wrought
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Mechanical
Yield strength65MPasourcetypical, tensile yield531MPasourceproducer-stated, cold drawn
Ultimate tensile strength65MPasourcetypical, stress at break627MPasourceproducer-stated, cold drawn
Flexural strength97MPasourcetypical, flexural strengthnot sourced
Elongation at break125%sourcetypical, strain at break12%sourcein 2 in (50.8 mm)
Young's modulus (stiffness)2.4GPasourcetypical210GPasourcetypical87.5x stiffer
Density1,200kg/m³sourcetypical6.5x lighter7,800kg/m³sourcetypical
Strength to weight54.2kN·m/kg68.1kN·m/kg26% higher
Stiffness to weight2MN·m/kg26.9MN·m/kg13.5x higher
Poisson's ratio0.38sourcetypical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1)0.3sourcetypical
Shear modulus0.87GPa80.8GPa92.9x stiffer in shear
Bulk modulus3.33GPa175GPa
Speed of sound1,414m/s5,189m/s
Thermal
Thermal conductivity0.2W/m·Ksourcetypical, through-plane, 23 C40–45W/m·Ksourcetypical range, ambient
Thermal expansion65µm/m·Ksourcetypical, 23-55 C, parallel and normal12µm/m·Ksourcetypical, mean 20-300 °C
100 mm part over a 50 °C swing325µm growth60µm growth5.42x less
Specific heat1,172J/kg·Ksourcetypical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766460–480J/kg·Ksourcetypical range, 50/100 °C
Heats up and cools (diffusivity)0.142mm²/s11.6mm²/s81.5x faster
Thermal shock resistance51.7W/m6,269W/m121x more resistant
Glass transition144°Csourcetypical, DSC 10 C/minnot sourced
Max service temperature125°CsourceUL 746B RTI, tensile strength, 1.5 mmnot sourced
Values forCovestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical valuesAISI 1045 cold drawn bar (Niagara LaSalle) for mechanical; Ovako C45 (lists 'SAE 1045' as a similar designation) for physical constants

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 1045?

Steel AISI 1045 is stronger: its yield strength is 531 MPa against 65 MPa for Plastic Polycarbonate (8.17x).

Which is lighter, Plastic Polycarbonate or Steel AISI 1045?

Plastic Polycarbonate is lighter: 1,200 kg/m³ against 7,800 kg/m³ for Steel AISI 1045.

Which is stiffer, Plastic Polycarbonate or Steel AISI 1045?

Steel AISI 1045 is stiffer: Young's modulus 210 GPa against 2.4 GPa for Plastic Polycarbonate, so the same part in Steel AISI 1045 deflects less under the same load.

Which is lighter for the same job, Plastic Polycarbonate or Steel AISI 1045?

For the same stiffness or strength: Plastic Polycarbonate is lighter for a stiff panel or plate, strong beam, strong panel or plate; Steel AISI 1045 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.

Part that must bePlastic PolycarbonateSteel AISI 1045
Stiff rod or tie (tension)13.5x heavierlighter
Stiff beam (bending)44% heavierlighter
Stiff panel or platelighter46% heavier
Strong rod or tie26% heavierlighter
Strong beamlighter1.6x heavier
Strong panel or platelighter2.27x 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 1045?

Steel AISI 1045 conducts heat better: 42.5 W/m·K against 0.2 W/m·K for Plastic Polycarbonate.

Which expands less with temperature?

Steel AISI 1045 expands less: 12 µm/m·K against 65 µm/m·K for Plastic Polycarbonate.

Among 59 materials

1k10k0.1110100Density (kg/m³)Young's modulus (GPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonAluminumSteelIronTitaniumSteel AISI 1018Stainless 304Stainless 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 4340Steel A992Stainless 303Stainless 17-4PHAluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelPlastic PolycarbonateSteel AISI 1045
Stiffness against density
1k10k101001kDensity (kg/m³)Yield strength (MPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonRubberAluminumSteelIronTitaniumSteel AISI 1018Stainless 304Stainless 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 4340Steel A992Stainless 303Stainless 17-4PHAluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic PTFEPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLA Resin Elastic 50ASLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelBrickPlastic PolycarbonateSteel AISI 1045
Strength against density

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