Extrusion & Post
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CMC extrusion melt fracture
Fenómeno del problema
When the extrusion rate of CMC is too high, severe melt fracture occurs and the extrudate is twisted in a spiral shape
Análisis de la causa
The CMC melt elasticity is too high and the elastic recovery at the die outlet exceeds the critical value; the die L/D ratio is too short <10 and the melt is not fully relaxed; the extrusion temperature is low
Solución
1) Reduce the extrusion rate to 2-3m/min; 2) Increase the die aspect ratio to 15-20; 3) Increase the extrusion temperature to 20-25°C; 4) Add a small amount of low-elasticity resin to reduce the elasticity of the system; 5) Gradually shrink the die inlet design
Conclusión clave
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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