A part that sags in a hot car, deforms near a motor or creeps under load at temperature has outgrown its material. The fix is usually a move up the heat ladder, ideally the smallest step that solves the problem, since every step costs more.
Read the right number
- Heat deflection temperature (HDT) is where a test bar bends a set amount under load. Check which load it was measured at (0.45 MPa or 1.8 MPa); the numbers differ a lot.
- Continuous use temperature (or relative thermal index) is what the material can take long-term without degrading. For parts that stay hot, this matters more than HDT.
- Glass fiber raises the HDT of semi-crystalline resins like nylon and PBT dramatically, much more than for amorphous resins.
A typical upgrade ladder
| Starting point | Common step up |
|---|---|
| Polypropylene | Talc- or glass-filled PP, or nylon |
| ABS | PC/ABS, then polycarbonate |
| Unfilled nylon | Glass-filled nylon 66 |
| Polycarbonate | PPO / PPE, or PEI for much higher heat |
| Glass-filled nylon or PBT | PEI or PEEK for the highest temperatures |
General direction only; actual values vary widely by grade.
Don’t forget
- Heat and chemicals together are harder on plastics than either alone.
- Creep (slow deformation under constant load) gets worse with heat; filled grades resist it better.
- Moving up the ladder often changes processing temperatures and drying needs.
PC/ABS · PPO / PPE · PEI · PEEK · Tell us the grade you run now →