Materials / Compare
Glass vs. Plastic PEEK
Compare Glass vs. Plastic PEEK 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) | 98MPasourcetypical, tensile yield |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | not sourced |
| Compressive strength | not sourced | 125MPasourcetypical, 23 C |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | 165MPasourcetypical, flexural stress at yield, 23 C |
| Elongation at break | not sourced | 25%sourcetypical, at break |
| Young's modulus (stiffness) | 72GPasourcetypical | 4GPasourcetypical (nominal) |
| Density | 2,500kg/m³sourcetypical | 1,300kg/m³sourcetypical (crystalline) |
| Strength to weight | 16.4kN·m/kg | 75.4kN·m/kg4.6x higher |
| Stiffness to weight | 28.8MN·m/kg9.36x higher | 3.08MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.38sourcetypical |
| Shear modulus | 29.5GPa20.4x stiffer in shear | 1.45GPa |
| Bulk modulus | 42.9GPa | 5.56GPa |
| Speed of sound | 5,367m/s | 1,754m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.29W/m·Ksourcetypical, average, 23 C |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) |
| 100 mm part over a 50 °C swing | 41.5µm growth6.63x less | 275µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) |
| Heats up and cools (diffusivity) | 0.426mm²/s4.2x faster | 0.101mm²/s |
| Thermal shock resistance | 50.1W/m | 80.1W/m1.6x more resistant |
| Melting point | not sourced | 343°Csourcetypical, DSC |
| Glass transition | not sourced | 143°Csourceonset (midpoint 150 C) |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) |
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 PEEK?
Plastic PEEK is stronger: its yield strength is 98 MPa against tensile strength 41 MPa for Glass (2.39x).
Which is lighter, Glass or Plastic PEEK?
Plastic PEEK is lighter: 1,300 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Plastic PEEK?
Glass is stiffer: Young's modulus 72 GPa against 4 GPa for Plastic PEEK, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or Plastic PEEK?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic PEEK is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | Plastic PEEK |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 9.36x heavier |
| Stiff beam (bending) | lighter | 2.21x heavier |
| Stiff panel or plate | lighter | 36% heavier |
| Strong rod or tie | 4.6x heavier | lighter |
| Strong beam | 3.44x heavier | lighter |
| Strong panel or plate | 2.97x 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 PEEK?
Glass conducts heat better: 0.937 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 55 µm/m·K for Plastic PEEK.