PBT and PET are both engineering polyesters, usually used glass-filled. (Bottle-grade PET is a different product.) The biggest difference is how easily they crystallize in the mold.
Side by side
| PBT | PET | |
|---|---|---|
| Crystallization | Fast; easy to mold | Slow; needs hot molds for full properties |
| Mold temperature | Moderate | High for engineering grades |
| Stiffness and strength (glass-filled) | High | Higher |
| Heat resistance (glass-filled) | High | Higher |
| Surface finish | Good | Excellent |
| Moisture absorption | Low; must still be dried | Low; must be dried thoroughly |
| Typical uses | Connectors, sensors, electrical housings | Structural parts, appliance and automotive components |
Typical, general comparisons. Individual grades vary; check the data sheet.
Choose PBT when
- Fast cycles and easy molding
- Connectors and electrical parts, especially FR
Choose PET when
- Maximum stiffness, heat and surface gloss
- You can run hot molds
Glass-filled PBT · PET / PBT · Drying guide · Tell us the grade you run now →