Extrusion & Post
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Die drool and carbon deposits at PVA extrusion die
Problem Phenomenon
After PVA extrusion shutdown, brown carbon deposit layer found on the die inner wall, black specks on product surface after restart
Cause Analysis
PVA in die residence zone heated for a long time, oxidized, decomposed and carbonized; die not cleaned in time at shutdown; extrusion temperature too high, accelerating carbonization
Solution
1) Flush the die with pure PE for 3-5min before shutdown to remove PVA residue; 2) Disassemble and clean the die immediately after shutdown; 3) Lower extrusion temperature by 5-10°C to reduce carbonization tendency; 4) Optimize die flow channel to reduce residence zone dead corners
Key Takeaway
Die carbon deposits are caused by thermal oxidation and untimely cleaning; PE flushing and timely cleaning are key
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