Extrusion & Post
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MP extrusion melt fracture
Problembeschreibung
MP shows severe melt fracture at excessive extrusion rate, extrudate twisted in a spiral shape
Ursachenanalyse
MP melt elasticity too high, elastic recovery at the die exit exceeds the critical value; die L/D ratio too short <10, melt not fully relaxed; extrusion temperature low
Lösung
1) reduce extrusion rate to 2-3m/min; 2) increase die L/D ratio to 15-20; 3) raise extrusion temperature to 150-170°C; 4) add a small amount of low-elasticity resin to reduce system elasticity; 5) gradually converging die entrance design
Wichtigste Erkenntnis
melt fracture is caused by elastic recovery exceeding the critical value; reducing speed and lengthening the die are the core countermeasures
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