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Plastic Polypropylene vs. Stainless 17-4PH

Compare Plastic Polypropylene vs. Stainless 17-4PH strength, stiffness, weight and thermal properties.

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Plastic PolypropyleneBulk polymer (molded or machined)
Stainless 17-4PHWrought
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Mechanical
Yield strength33MPasourcetypical, tensile stress at yield ISO 5271,275MPasourcetypical, transverse, sheet/strip
Ultimate tensile strengthnot sourced1,379MPasourcetypical, transverse, sheet/strip
Elongation at breaknot sourced9%sourcetypical, transverse, in 2 in. (50.8 mm)
Young's modulus (stiffness)1.45GPasourcetypical, tensile modulus ISO 527197GPasourceH 900
Density900kg/m³sourcetypical, 23 °C ISO 1183-17,800kg/m³sourceH 900
Strength to weight36.7kN·m/kg163kN·m/kg4.46x higher
Stiffness to weight1.61MN·m/kg25.3MN·m/kg15.7x higher
Poisson's ratio0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)0.272sourceH 900 (column)
Shear modulus0.511GPa77.4GPa152x stiffer in shear
Bulk modulus3.02GPa144GPa
Speed of sound1,269m/s5,026m/s
Thermal
Thermal conductivity0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)17.9W/m·Ksourceat 149 °C (300 °F), H 900
Thermal expansion80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900
100 mm part over a 50 °C swing450µm growth54µm growth8.33x less
Specific heatnot sourced460J/kg·Ksourcemean, 0–100 °C, H 900
Heats up and cools (diffusivity)not sourced4.99mm²/s
Thermal shock resistance28.6W/m7,809W/m273x more resistant
Max service temperature90°CsourceHDT 0.45 MPa (ISO 75B), unannealed316°Csourcestrength-retention limit (not oxidation)
Values forLyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO valuesCleveland-Cliffs 17-4 PH, Condition H 900, sheet/strip, transverse (Product Data Bulletin, May 2021)

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 Stainless 17-4PH?

Stainless 17-4PH is stronger: its yield strength is 1,275 MPa against 33 MPa for Plastic Polypropylene (38.6x).

Which is lighter, Plastic Polypropylene or Stainless 17-4PH?

Plastic Polypropylene is lighter: 900 kg/m³ against 7,800 kg/m³ for Stainless 17-4PH.

Which is stiffer, Plastic Polypropylene or Stainless 17-4PH?

Stainless 17-4PH is stiffer: Young's modulus 197 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Stainless 17-4PH deflects less under the same load.

Which is lighter for the same job, Plastic Polypropylene or Stainless 17-4PH?

For the same stiffness or strength: Plastic Polypropylene is lighter for a stiff panel or plate, strong panel or plate; Stainless 17-4PH is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam.

Part that must bePlastic PolypropyleneStainless 17-4PH
Stiff rod or tie (tension)15.7x heavierlighter
Stiff beam (bending)34% heavierlighter
Stiff panel or platelighter1.69x heavier
Strong rod or tie4.46x heavierlighter
Strong beam32% heavierlighter
Strong panel or platelighter39% 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 Stainless 17-4PH?

Stainless 17-4PH conducts heat better: 17.9 W/m·K against 0.195 W/m·K for Plastic Polypropylene.

Which expands less with temperature?

Stainless 17-4PH expands less: 10.8 µm/m·K against 90 µm/m·K for Plastic Polypropylene.

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 1045Steel AISI 4340Steel A992Stainless 303Aluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic UHMWPEPlastic HDPEPlastic 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 PolypropyleneStainless 17-4PH
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 1045Steel AISI 4340Steel A992Stainless 303Aluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic PTFEPlastic UHMWPEPlastic HDPEPlastic 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 PolypropyleneStainless 17-4PH
Strength against density

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