Extrusion & Post
10 조회수
Melt fracture in PVA extrusion
문제 현상
When extrusion rate is too high, PVA shows severe melt fracture, extrudate twisted in spiral shape
원인 분석
PVA melt elasticity too high, elastic recovery at die exit exceeds critical value; die L/D ratio too short <10, melt not fully relaxed; extrusion temperature too low
해결 방법
1) Reduce extrusion rate to 2-3m/min; 2) Increase die length-to-diameter ratio to 15-20; 3) Increase extrusion temperature to 140-200°C; 4) Add a small amount of low-elasticity resin to reduce system elasticity; 5) Gradually converging die entrance design
핵심 요약
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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