Extrusion & Post
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LDPE Film Wet Marks
Problem Phenomenon
Cast film surface shows wet-mark water-stain-like defects, appearance is downgraded, and temperature adjustment gives inconsistent results
Cause Analysis
Wet marks are a sign that the film cooling rate is too slow: melt temperature too high, chill roll temperature high, and line speed fast cause the film to not be fully cooled before leaving the roll surface, and the surface shows wet marks
Solution
① Lower the chill roll temperature in 5℃ steps but not below the lower limit of 15℃; ② reduce extrusion and line speed to reduce cooling load; ③ lower the die lip temperature in 3℃ steps; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The radical cure for LDPE film wet marks lies in the cooling rate; roll temperature, speed, and die lip temperature are three parameters linked to lower the temperature; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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