Materials / Compare
Glass vs. Plastic Polypropylene
Compare Glass vs. Plastic Polypropylene 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) | 33MPasourcetypical, tensile stress at yield 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 | 1.45GPasourcetypical, tensile modulus ISO 527 |
| Density | 2,500kg/m³sourcetypical | 900kg/m³sourcetypical, 23 °C ISO 1183-1 |
| Strength to weight | 16.4kN·m/kg | 36.7kN·m/kg2.24x higher |
| Stiffness to weight | 28.8MN·m/kg17.9x higher | 1.61MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| Shear modulus | 29.5GPa57.8x stiffer in shear | 0.511GPa |
| Bulk modulus | 42.9GPa | 3.02GPa |
| Speed of sound | 5,367m/s | 1,269m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene) |
| 100 mm part over a 50 °C swing | 41.5µm growth10.8x less | 450µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | not sourced |
| Heats up and cools (diffusivity) | 0.426mm²/s | not sourced |
| Thermal shock resistance | 50.1W/m1.75x more resistant | 28.6W/m |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 90°CsourceHDT 0.45 MPa (ISO 75B), unannealed |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), 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 Polypropylene?
Glass is stronger: its tensile strength is 41 MPa against yield strength 33 MPa for Plastic Polypropylene (24%).
Which is lighter, Glass or Plastic Polypropylene?
Plastic Polypropylene is lighter: 900 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic Polypropylene?
Glass is stiffer: Young's modulus 72 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic Polypropylene?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic Polypropylene is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic Polypropylene |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 17.9x heavier |
| Stiff beam (bending) | lighter | 2.54x heavier |
| Stiff panel or plate | lighter | 32% heavier |
| Strong rod or tie | 2.24x heavier | lighter |
| Strong beam | 2.4x heavier | lighter |
| Strong panel or plate | 2.49x 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 Polypropylene?
Glass conducts heat better: 0.937 W/m·K against 0.195 W/m·K for Plastic Polypropylene.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 90 µm/m·K for Plastic Polypropylene.