Extrusion & Post
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LLDPE Blown Film Melt Fracture
Problem Phenomenon
The film surface is overall orange-peel-like and thread-like rough, more severe than sharkskin.
Cause Analysis
The outlet shear rate far exceeds the critical value, and the melt becomes overall unstable; low die temperature and excessive output are the main causes.
Solution
① Reduce output/line speed; ② raise the die temperature; ③ enlarge the die lip gap to reduce shear; ④ use PPA; ⑤ check whether there are abrupt changes in the die flow channel.
Key Takeaway
For melt fracture, first reduce shear, then raise temperature.
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