Extrusion & Post
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LDPE Extrusion Coating Neck-in
Problem Phenomenon
During extrusion coating/lamination, the two edges of the molten film shrink back, and the effective coating width narrows.
Cause Analysis
Elastic shrinkage of the molten film after exiting the die + fast edge cooling; low die temperature, fast haul-off and large melt elasticity all increase neck-in.
Solution
①Raise melt temperature; ②reduce haul-off speed; ③optimize air gap distance; ④select low neck-in grades.
Key Takeaway
Neck-in = elastic shrinkage; adjust oppositely to lowering temperature and increasing speed.
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