Materials / Compare
Plastic POM/Acetal vs. Stainless 304
Compare Plastic POM/Acetal vs. Stainless 304 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 | 69MPasourcetypical (single ASTM D638 tensile strength) | 241MPasourcetypical, annealed, 70 °F (21 °C) |
| Ultimate tensile strength | 69MPasourcetypical | 586MPasourcetypical, annealed, 70 °F (21 °C) |
| Compressive strength | 124MPasourcecompressive stress at 10% deformation | not sourced |
| Flexural strength | 99MPasourceflexural yield strength, typical | not sourced |
| Elongation at break | 75%sourcetypical | 55%sourcetypical, annealed, in 2 in. (50.8 mm) |
| Young's modulus (stiffness) | 2.8GPasourcetypical | 193GPasourcetypical, in tension |
| Density | 1,420kg/m³sourcetypical (DuPont product information for Delrin 100 NC010; 'The data listed here fall within the normal range of product properties') | 8,030kg/m³sourcetypical |
| Strength to weight | 48.6kN·m/kg1.62x higher | 30kN·m/kg |
| Stiffness to weight | 1.97MN·m/kg | 24MN·m/kg12.2x higher |
| Poisson's ratio | 0.35sourcetypical | 0.3sourcedesign value (structural stainless steels) |
| Shear modulus | 1.04GPa | 74.2GPa71.6x stiffer in shear |
| Bulk modulus | 3.11GPa | 161GPa |
| Speed of sound | 1,404m/s | 4,903m/s |
| Thermal | ||
| Thermal conductivity | 0.4W/m·Ksourcetypical | 16.2W/m·Ksourceat 100 °C |
| Thermal expansion | 122µm/m·Ksourcemean, 29 to 60 °C | 16.9µm/m·Ksourcemean, 0–100 °C |
| 100 mm part over a 50 °C swing | 610µm growth | 84.5µm growth7.22x less |
| Specific heat | 1,465J/kg·Ksourceaverage -18 to 100 °C, Delrin acetal resins (not grade-specific) | 500J/kg·Ksourcemean, 0–100 °C |
| Heats up and cools (diffusivity) | 0.192mm²/s | 4.03mm²/s21x faster |
| Thermal shock resistance | 52.5W/m | 838W/m16x more resistant |
| Melting point | 175°Csourcecrystalline melting point | 1,399–1,454°Csourcemelting range |
| Max service temperature | 125°CsourceHDT 1.8 MPa (annealed) | 899°Csourcecontinuous, oxidation (scaling) limit in air |
| 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 | Type 304, annealed flat-rolled (Cleveland-Cliffs 304/304L Product Data Bulletin, May 2021); Poisson's ratio from the Nickel Institute/SCI structural stainless design manual |
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 304?
Stainless 304 is stronger: its yield strength is 241 MPa against 69 MPa for Plastic POM/Acetal (3.49x).
Which is lighter, Plastic POM/Acetal or Stainless 304?
Plastic POM/Acetal is lighter: 1,420 kg/m³ against 8,030 kg/m³ for Stainless 304.
Which is stiffer, Plastic POM/Acetal or Stainless 304?
Stainless 304 is stiffer: Young's modulus 193 GPa against 2.8 GPa for Plastic POM/Acetal, so the same part in Stainless 304 deflects less under the same load.
Which is lighter for the same job, Plastic POM/Acetal or Stainless 304?
For the same stiffness or strength: Plastic POM/Acetal is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Stainless 304 is lighter for a stiff rod or tie (tension), stiff beam (bending).
| Part that must be | Plastic POM/Acetal | Stainless 304 |
|---|---|---|
| Stiff rod or tie (tension) | 12.2x heavier | lighter |
| Stiff beam (bending) | 47% heavier | lighter |
| Stiff panel or plate | lighter | 38% heavier |
| Strong rod or tie | lighter | 1.62x heavier |
| Strong beam | lighter | 2.46x heavier |
| Strong panel or plate | lighter | 3.03x 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 304?
Stainless 304 conducts heat better: 16.2 W/m·K against 0.4 W/m·K for Plastic POM/Acetal.
Which expands less with temperature?
Stainless 304 expands less: 16.9 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.