Extrusion & Post
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Dense EVOH Surface Pits
Problem Phenomenon
EVOH product surfaces show dense 0.1-0.3mm pits affecting appearance and coating adhesion
Cause Analysis
Raw material contains impurity particles >0.05%; mold cavity surface damage or corrosion pits
Solution
1) Replace with pure raw material with impurities <0.01%; 2) Repair and polish mold cavity to Ra<0.2μm; 3) Filter raw material to remove particles
Key Takeaway
Pits are caused by raw material impurities and mold damage; pure raw material and mold maintenance are key
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