Molding Process
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Coarse internal crystallization of PU
Fenómeno do problema
Internal spherulites of PU products >50μm coarse, causing decreased transparency and low impact
Análise das causas
Cooling rate too slow <5°C/min allowing spherulites to fully grow; no nucleating agent used to control crystallization
Solução
1) Increase cooling rate to >20°C/min to refine spherulites; 2) Add 0.2-0.3wt% nucleating agent to control crystallization; 3) Lower mold temperature to accelerate cooling
Conclusão principal
Coarse crystallization is caused by slow cooling; fast cooling and nucleating agent are key
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