Thermoplastic comparison
PET vs Polypropylene (PP)
Every value below is a typical room-temperature figure with its source, test method and conditions — the same dataset that drives the calculators.
| Property | PET | Polypropylene (PP) | Difference |
|---|---|---|---|
| Density | 1.37 g/cm³ | 0.905 g/cm³ | PET — 51% higher |
| Young's modulus E | 2.9 GPa | 1.4 GPa | PET — 2.1× higher |
| Tensile strength | 60 MPa | 34 MPa | PET — 76% higher |
| Glass transition Tg | 76 °C | -10 °C | PET — 86 °C higher |
| Melting point Tm | 255 °C | 165 °C | PET — 90 °C higher |
Where these numbers come from
- Callister & Rethwisch, Materials Science and Engineering, 10th ed.
Typical room-temperature values for learning and preliminary design; grades vary widely and a supplier datasheet always overrides a textbook figure. Confirm against the datasheet before design work.