Extrusion & Post
10 조회수
Melt Fracture in PU Extrusion
문제 현상
PU shows severe melt fracture at excessive extrusion rate, extrudate spirally twisted
원인 분석
PU melt elasticity too high, elastic recovery at the die exit exceeding the 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 L/D ratio to 15-20; 3) Increase extrusion temperature to 60-120°C; 4) Add a small amount of low-elasticity resin to reduce system elasticity; 5) Gradual contraction 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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