Crystallinity in neck/body (white spots)
Cause
Slow cooling or overheating crystallizes PET, creating brittle white zones.
Corrective action
Improve mold cooling, reduce cycle time appropriately, check hot-runner hot spots.
Diagnosis guide: Preform semi-crystalline (whitened body)
What you will see
Preform body shows white or opaque coloration instead of being clear. PET has converted to crystalline phase — cannot blow into a usable bottle (will pearlescence or crack).
Likely causes
- IM cooling time too long at high temp (Delta plant)
- IM barrel temperature too high
- Resin grade incorrect for IM conditions
Do this first
STOP receiving. Visual inspection: clear vs white-tinted body.
How to diagnose it
- Hold preform up to light
- Clear preform: transparent body
- Crystalline preform: white opacity in body
- Tap suspect preform — brittle = confirmed crystalline
How to fix it
- Quarantine lot
- Contact Delta — this is a critical defect