Material Drying
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PET vented extrusion drying-free
Problem Phenomenon
Attempting to produce PET sheet with a vented extruder completely without drying, the products still have bubbles
Cause Analysis
A vented extruder can only remove surface moisture, and the deep-layer moisture of crystallized PET pellets still requires hopper drying; venting is insurance rather than a replacement, and completely eliminating drying carries extremely high risk
Solution
①Pre-dry to 50 ppm and then use venting as a backstop; ②regularly calibrate the vacuum degree of the venting section; ③the drying process must not be canceled on the grounds of venting; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PET vented extrusion is a double-insurance mode of drying plus venting; skipping drying and relying only on venting, the deep-layer moisture will inevitably collect its debt in the form of bubbles; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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