Materials / Compare
Glass vs. Plastic Polycarbonate
Compare Glass vs. Plastic Polycarbonate 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) | 65MPasourcetypical, tensile yield |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | 65MPasourcetypical, stress at break |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | 97MPasourcetypical, flexural strength |
| Elongation at break | not sourced | 125%sourcetypical, strain at break |
| Young's modulus (stiffness) | 72GPasourcetypical30x stiffer | 2.4GPasourcetypical |
| Density | 2,500kg/m³sourcetypical | 1,200kg/m³sourcetypical2.08x lighter |
| Strength to weight | 16.4kN·m/kg | 54.2kN·m/kg3.3x higher |
| Stiffness to weight | 28.8MN·m/kg14.4x higher | 2MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.38sourcetypical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1) |
| Shear modulus | 29.5GPa33.9x stiffer in shear | 0.87GPa |
| Bulk modulus | 42.9GPa | 3.33GPa |
| Speed of sound | 5,367m/s | 1,414m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.2W/m·Ksourcetypical, through-plane, 23 C |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 65µm/m·Ksourcetypical, 23-55 C, parallel and normal |
| 100 mm part over a 50 °C swing | 41.5µm growth7.83x less | 325µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 1,172J/kg·Ksourcetypical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766 |
| Heats up and cools (diffusivity) | 0.426mm²/s2.99x faster | 0.142mm²/s |
| Thermal shock resistance | 50.1W/m | 51.7W/m3% more resistant |
| Glass transition | not sourced | 144°Csourcetypical, DSC 10 C/min |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 125°CsourceUL 746B RTI, tensile strength, 1.5 mm |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | Covestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical 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 Polycarbonate?
Plastic Polycarbonate is stronger: its yield strength is 65 MPa against tensile strength 41 MPa for Glass (1.59x).
Which is lighter, Glass or Plastic Polycarbonate?
Plastic Polycarbonate is lighter: 1,200 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic Polycarbonate?
Glass is stiffer: Young's modulus 72 GPa against 2.4 GPa for Plastic Polycarbonate, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic Polycarbonate?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic Polycarbonate is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic Polycarbonate |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 14.4x heavier |
| Stiff beam (bending) | lighter | 2.63x heavier |
| Stiff panel or plate | lighter | 49% heavier |
| Strong rod or tie | 3.3x heavier | lighter |
| Strong beam | 2.83x heavier | lighter |
| Strong panel or plate | 2.62x 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 Polycarbonate?
Glass conducts heat better: 0.937 W/m·K against 0.2 W/m·K for Plastic Polycarbonate.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 65 µm/m·K for Plastic Polycarbonate.