Extrusion & Post
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EVOH extrusion die drool carbon deposits
Problembeschreibung
After EVOH extrusion shutdown, a brown carbon deposit layer is found on the die inner wall; after restart, black specks appear on the product surface
Ursachenanalyse
EVOH is oxidized, decomposed and carbonized by prolonged heating in die stagnation zones; die not cleaned in time during shutdown; extrusion temperature too high accelerating carbonization
Lösung
1) Flush the die with pure PE for 3-5min before shutdown to remove EVOH 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 dead corners in stagnation zones
Wichtigste Erkenntnis
Die carbon deposits are caused by thermal oxidation and untimely cleaning; PE flushing and timely cleaning are key
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