Molds & Tooling
5 مشاهدة
PET melt temperature too high causing degradation
ظاهرة المشكلة
The preforms turn yellow, IV testing shows a decline, the AA value rises, and carbonized black specks can be seen during barrel cleaning, confirming that the processing temperature exceeds the range the material can withstand.
تحليل الأسباب
When the melt temperature stays above the 290℃ upper limit for a long time, PET thermo-oxidative degradation accelerates; the superposition of screw shear heat and hot runner overshoot can also make the actual melt temperature exceed the set value.
الحل
①Adjust the temperatures of all zones back to the 270~290℃ window; ②actually measure the melt temperature to calibrate the thermocouple; ③reduce the screw speed to reduce shear heat; ④clean the hot runner to eliminate dead corners.
الخلاصة الأساسية
PET thermal degradation simultaneously produces the triple hazards of yellowing, AA increase, and IV decline; regularly measuring the actual melt temperature rather than only looking at the display is a basic requirement of temperature control management.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
هل كان هذا مفيدًا؟
0 شخص وجدوا هذا مفيدًا
شكرًا لك على ملاحظاتك!