Extrusion & Post
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Pearl luster spots on PET bottle body
Problembeschreibung
Pearl-like shiny spots appear locally on the PET bottle body, obviously different gloss from surroundings.
Ursachenanalyse
The stretching temperature in that area is in the fastest PET crystallization range (140-170°C); stress-induced crystallization produces large amounts of tiny grains.
Lösung
Optimize preform heating temperature distribution to avoid local overheating; adjust infrared lamp power distribution; increase stretching speed to quickly pass through the crystallization temperature zone.
Wichtigste Erkenntnis
PET pearl luster spots are a manifestation of local excessive crystallization; heating temperature control is key.
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