Materials / Compare
Plastic POM/Acetal vs. Stainless 17-4PH
Compare Plastic POM/Acetal vs. Stainless 17-4PH strength, stiffness, weight and thermal properties.
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|---|---|---|
| Mechanical | ||
| Yield strength | 69MPasourcetypical (single ASTM D638 tensile strength) | 1,275MPasourcetypical, transverse, sheet/strip |
| Ultimate tensile strength | 69MPasourcetypical | 1,379MPasourcetypical, transverse, sheet/strip |
| Compressive strength | 124MPasourcecompressive stress at 10% deformation | not sourced |
| Flexural strength | 99MPasourceflexural yield strength, typical | not sourced |
| Elongation at break | 75%sourcetypical | 9%sourcetypical, transverse, in 2 in. (50.8 mm) |
| Young's modulus (stiffness) | 2.8GPasourcetypical | 197GPasourceH 900 |
| Density | 1,420kg/m³sourcetypical (DuPont product information for Delrin 100 NC010; 'The data listed here fall within the normal range of product properties') | 7,800kg/m³sourceH 900 |
| Strength to weight | 48.6kN·m/kg | 163kN·m/kg3.36x higher |
| Stiffness to weight | 1.97MN·m/kg | 25.3MN·m/kg12.8x higher |
| Poisson's ratio | 0.35sourcetypical | 0.272sourceH 900 (column) |
| Shear modulus | 1.04GPa | 77.4GPa74.7x stiffer in shear |
| Bulk modulus | 3.11GPa | 144GPa |
| Speed of sound | 1,404m/s | 5,026m/s |
| Thermal | ||
| Thermal conductivity | 0.4W/m·Ksourcetypical | 17.9W/m·Ksourceat 149 °C (300 °F), H 900 |
| Thermal expansion | 122µm/m·Ksourcemean, 29 to 60 °C | 10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900 |
| 100 mm part over a 50 °C swing | 610µm growth | 54µm growth11.3x less |
| Specific heat | 1,465J/kg·Ksourceaverage -18 to 100 °C, Delrin acetal resins (not grade-specific) | 460J/kg·Ksourcemean, 0–100 °C, H 900 |
| Heats up and cools (diffusivity) | 0.192mm²/s | 4.99mm²/s25.9x faster |
| Thermal shock resistance | 52.5W/m | 7,809W/m149x more resistant |
| Melting point | 175°Csourcecrystalline melting point | not sourced |
| Max service temperature | 125°CsourceHDT 1.8 MPa (annealed) | 316°Csourcestrength-retention limit (not oxidation) |
| Values for | DuPont Delrin 100 acetal homopolymer, Table 2 'Typical Properties of Delrin Acetal Resins' (ASTM methods), Delrin Design Guide Module III hosted on delrin.com | Cleveland-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 POM/Acetal stronger than Stainless 17-4PH?
Stainless 17-4PH is stronger: its yield strength is 1,275 MPa against 69 MPa for Plastic POM/Acetal (18.5x).
Which is lighter, Plastic POM/Acetal or Stainless 17-4PH?
Plastic POM/Acetal is lighter: 1,420 kg/m³ against 7,800 kg/m³ for Stainless 17-4PH.
Which is stiffer, Plastic POM/Acetal or Stainless 17-4PH?
Stainless 17-4PH is stiffer: Young's modulus 197 GPa against 2.8 GPa for Plastic POM/Acetal, so the same part in Stainless 17-4PH deflects less under the same load.
Which is lighter for the same job, Plastic POM/Acetal or Stainless 17-4PH?
For the same stiffness or strength: Plastic POM/Acetal 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 be | Plastic POM/Acetal | Stainless 17-4PH |
|---|---|---|
| Stiff rod or tie (tension) | 12.8x heavier | lighter |
| Stiff beam (bending) | 1.53x heavier | lighter |
| Stiff panel or plate | lighter | 33% heavier |
| Strong rod or tie | 3.36x heavier | lighter |
| Strong beam | 27% heavier | lighter |
| Strong panel or plate | lighter | 28% 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 POM/Acetal or Stainless 17-4PH?
Stainless 17-4PH conducts heat better: 17.9 W/m·K against 0.4 W/m·K for Plastic POM/Acetal.
Which expands less with temperature?
Stainless 17-4PH expands less: 10.8 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.
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