Thermoplastic comparison
PBT (polybutylene terephthalate) vs PEI (Ultem)
Every value below is a typical room-temperature figure with its source, test method and conditions — the same dataset that drives the calculators.
| Property | PBT (polybutylene terephthalate) | PEI (Ultem) | Difference |
|---|---|---|---|
| Density | 1.31 g/cm³ | 1.27 g/cm³ | PBT (polybutylene terephthalate) — 3% higher |
| Young's modulus E | 2.6 GPa | 3.2 GPa | PEI (Ultem) — 23% higher |
| Tensile strength | 55 MPa | 105 MPa | PEI (Ultem) — 91% higher |
| Glass transition Tg | 45 °C | 217 °C | PEI (Ultem) — 172 °C higher |
Where these numbers come from
- CAMPUS plastics database — typical grade datasheet values (campusplastics.com)
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.