Materials / Compare
Glass vs. Plastic HDPE
Compare Glass vs. Plastic HDPE 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) | 24MPasourcetypical, tensile stress at yield 23 °C, 50 mm/min ISO 527 |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | not sourced |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | not sourced |
| Elongation at break | not sourced | not sourced |
| Young's modulus (stiffness) | 72GPasourcetypical | 0.9GPasourcetypical, tensile modulus 23 °C ISO 527 |
| Density | 2,500kg/m³sourcetypical | 950kg/m³sourcetypical, ISO 1183 |
| Strength to weight | 16.4kN·m/kg | 25.3kN·m/kg1.54x higher |
| Stiffness to weight | 28.8MN·m/kg30.4x higher | 0.947MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.4–0.45sourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) |
| Shear modulus | 29.5GPa93.4x stiffer in shear | 0.316GPa |
| Bulk modulus | 42.9GPa | 2GPa |
| Speed of sound | 5,367m/s | 973m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.4–0.49W/m·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 120µm/m·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) |
| 100 mm part over a 50 °C swing | 41.5µm growth14.5x less | 600µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 2,250J/kg·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) |
| Heats up and cools (diffusivity) | 0.426mm²/s2.05x faster | 0.208mm²/s |
| Thermal shock resistance | 50.1W/m | 56.9W/m13% more resistant |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | not sourced |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values |
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 HDPE?
Glass is stronger: its tensile strength is 41 MPa against yield strength 24 MPa for Plastic HDPE (1.71x).
Which is lighter, Glass or Plastic HDPE?
Plastic HDPE is lighter: 950 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic HDPE?
Glass is stiffer: Young's modulus 72 GPa against 0.9 GPa for Plastic HDPE, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic HDPE?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic HDPE is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic HDPE |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 30.4x heavier |
| Stiff beam (bending) | lighter | 3.4x heavier |
| Stiff panel or plate | lighter | 1.64x heavier |
| Strong rod or tie | 1.54x heavier | lighter |
| Strong beam | 1.84x heavier | lighter |
| Strong panel or plate | 2.01x 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 HDPE?
Glass conducts heat better: 0.937 W/m·K against 0.445 W/m·K for Plastic HDPE.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 120 µm/m·K for Plastic HDPE.