Extrusion & Post
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Pearl luster spots on PET bottle body
Problem Phenomenon
Pearl-like shiny spots appear locally on the PET bottle body, obviously different gloss from surroundings.
Cause Analysis
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.
Solution
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.
Key Takeaway
PET pearl luster spots are a manifestation of local excessive crystallization; heating temperature control is key.
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