Material Drying
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PET bottle-grade drying temperature
Fenómeno del problema
Bottle-grade PET is dried at 150℃ for 8 hours, and the chip IV value drops significantly with the preform body turning yellow
Análisis de la causa
Bottle-grade PET drying temperature should be 165-175℃ to ensure crystallization and dehydration efficiency; when the temperature is too low, the drying time is forced to be extended, which instead aggravates thermal oxidation, and IV loss and yellowing follow
Solución
Bottle-grade PET is dried at 165-175℃ for 4-6 hours, crystallizing first and then drying; compensating for insufficient drying by extending the time is inferior to ensuring the temperature; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Conclusión clave
Bottle-grade drying is a high-temperature short-time route, and low-temperature long-time instead harms the material; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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