Materials / Compare
Glass vs. Plastic PMMA
Compare Glass vs. Plastic PMMA 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) | not given (tensile used) |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | 80MPasourcetypical, 23 °C |
| Compressive strength | not sourced | 110MPasourcecompressive yield stress, typical |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | 115MPasourcetypical |
| Elongation at break | not sourced | 5.5%sourcetypical |
| Young's modulus (stiffness) | 72GPasourcetypical | 3.3GPasourcetypical, short-term |
| Density | 2,500kg/m³sourcetypical | 1,190kg/m³sourcetypical2.1x lighter |
| Strength to weight | 16.4kN·m/kg | 67.2kN·m/kg4.1x higher |
| Stiffness to weight | 28.8MN·m/kg10.4x higher | 2.77MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.37sourcetypical |
| Shear modulus | 29.5GPa24.5x stiffer in shear | 1.2GPa |
| Bulk modulus | 42.9GPa | 4.23GPa |
| Speed of sound | 5,367m/s | 1,665m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.19W/m·Ksourcetypical |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 70µm/m·Ksource0-50 °C |
| 100 mm part over a 50 °C swing | 41.5µm growth8.43x less | 350µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 1,470J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 0.426mm²/s3.92x faster | 0.109mm²/s |
| Thermal shock resistance | 50.1W/m21% more resistant | 41.5W/m |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 80°Csourcemax. permanent service temperature |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1) |
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 PMMA?
Plastic PMMA is stronger: its tensile strength is 80 MPa against 41 MPa for Glass (1.95x).
Which is lighter, Glass or Plastic PMMA?
Plastic PMMA is lighter: 1,190 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic PMMA?
Glass is stiffer: Young's modulus 72 GPa against 3.3 GPa for Plastic PMMA, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic PMMA?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic PMMA is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic PMMA |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 10.4x heavier |
| Stiff beam (bending) | lighter | 2.22x heavier |
| Stiff panel or plate | lighter | 33% heavier |
| Strong rod or tie | 4.1x heavier | lighter |
| Strong beam | 3.28x heavier | lighter |
| Strong panel or plate | 2.93x 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 PMMA?
Glass conducts heat better: 0.937 W/m·K against 0.19 W/m·K for Plastic PMMA.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 70 µm/m·K for Plastic PMMA.