Material Drying
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PARA Mold Temperature Too Low, Insufficient Crystallization
Fenómeno del problema
PARA products show poor surface appearance, increased moisture absorption, large creep tendency and abnormal shrinkage, concentrated in batches molded with low-temperature molds.
Análisis de la causa
PARA is a semi-crystalline polymer with a glass transition temperature of 85°C; when mold temperature is below 120°C crystallinity is insufficient; the large amorphous region proportion increases moisture absorption; failure to reach maximum crystallinity leads to post-crystallization risk and performance defects.
Solución
①Mold temperature must be at least 120°C, recommended 120~140°C; ②Use a temperature probe to measure the actual cavity surface temperature for verification; ③DSC analysis of crystallinity to confirm no 80~120°C exothermic peak; ④Evaluate scrapping of low-temperature mold batches.
Conclusión clave
PARA's 120°C mold temperature red line is determined by the 85°C Tg; the DSC post-crystallization peak is direct evidence of insufficient crystallization; mold temperature verification must be measured rather than the displayed value.
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