Materials / Compare
Glass vs. Plastic POM/Acetal
Compare Glass vs. Plastic POM/Acetal strength, stiffness, weight and thermal properties.
| Try it on a partA sample part to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | not given (tensile used) | 69MPasourcetypical (single ASTM D638 tensile strength) |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | 69MPasourcetypical |
| Compressive strength | not sourced | 124MPasourcecompressive stress at 10% deformation |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | 99MPasourceflexural yield strength, typical |
| Elongation at break | not sourced | 75%sourcetypical |
| Young's modulus (stiffness) | 72GPasourcetypical25.7x stiffer | 2.8GPasourcetypical |
| Density | 2,500kg/m³sourcetypical | 1,420kg/m³sourcetypical (DuPont product information for Delrin 100 NC010; 'The data listed here fall within the normal range of product properties') |
| Strength to weight | 16.4kN·m/kg | 48.6kN·m/kg2.96x higher |
| Stiffness to weight | 28.8MN·m/kg14.6x higher | 1.97MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.35sourcetypical |
| Shear modulus | 29.5GPa28.5x stiffer in shear | 1.04GPa |
| Bulk modulus | 42.9GPa | 3.11GPa |
| Speed of sound | 5,367m/s | 1,404m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.4W/m·Ksourcetypical |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 122µm/m·Ksourcemean, 29 to 60 °C |
| 100 mm part over a 50 °C swing | 41.5µm growth14.7x less | 610µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 1,465J/kg·Ksourceaverage -18 to 100 °C, Delrin acetal resins (not grade-specific) |
| Heats up and cools (diffusivity) | 0.426mm²/s2.22x faster | 0.192mm²/s |
| Thermal shock resistance | 50.1W/m | 52.5W/m5% more resistant |
| Melting point | not sourced | 175°Csourcecrystalline melting point |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 125°CsourceHDT 1.8 MPa (annealed) |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | DuPont Delrin 100 acetal homopolymer, Table 2 'Typical Properties of Delrin Acetal Resins' (ASTM methods), Delrin Design Guide Module III hosted on delrin.com |
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 Glass stronger than Plastic POM/Acetal?
Plastic POM/Acetal is stronger: its yield strength is 69 MPa against tensile strength 41 MPa for Glass (1.68x).
Which is lighter, Glass or Plastic POM/Acetal?
Plastic POM/Acetal is lighter: 1,420 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic POM/Acetal?
Glass is stiffer: Young's modulus 72 GPa against 2.8 GPa for Plastic POM/Acetal, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic POM/Acetal?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic POM/Acetal is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic POM/Acetal |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 14.6x heavier |
| Stiff beam (bending) | lighter | 2.88x heavier |
| Stiff panel or plate | lighter | 1.68x heavier |
| Strong rod or tie | 2.96x heavier | lighter |
| Strong beam | 2.49x heavier | lighter |
| Strong panel or plate | 2.28x heavier | lighter |
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, Glass or Plastic POM/Acetal?
Glass conducts heat better: 0.937 W/m·K against 0.4 W/m·K for Plastic POM/Acetal.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.