Extrusion & Post
13 مشاهدة
PET Blowing Milky White Whitening (Overheated Crystallization)
ظاهرة المشكلة
Porcelain-white turbid areas appear on the bottle body, mostly at the bottom or thick-wall areas; the whitened areas have increased brittleness and decreased strength.
تحليل الأسباب
The preform is locally overheated, and PET has thermally crystallized before stretching; the crystallized zone cannot be normally oriented and stretched, and appears milky white after blowing with deteriorated mechanical properties.
الحل
①Reduce the temperature of the corresponding heating zone and shorten heating time; ②strengthen preform temperature measurement and thermal image monitoring; ③check lamp aging and reflector condition; ④reject crystallized preforms.
الخلاصة الأساسية
Milky white whitening is caused by overheated crystallization, and its machine adjustment direction is opposite to that of pearlescent whitening, so they must be accurately distinguished first; thermal imager monitoring of heating uniformity is an effective preventive means.
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