Material Drying
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PET sheet bubbles and moisture
Problem Phenomenon
Visible bubbles inside PET sheet and surface blistering; both transparency and '2079851475616104458 performance decrease
Cause Analysis
When pellets are insufficiently dried with moisture content exceeding 0.005%, moisture vaporizes during melt extrusion to form bubbles; poor vacuum venting and volatilization of impurities in recycled material also produce gas; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
① Improve drying efficiency to moisture content <0.005%; ② optimize vacuum venting performance; ③ strengthen washing of recycled material and equip with high-efficiency melt filtration; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Ninety percent of PET sheet bubbles can be traced back to moisture; drying, venting, and filtration are three lines of defense, and drying is the first and most important one; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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