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