Material Drying
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PET Preform Insufficient Drying (Hydrolysis)
Fenómeno del problema
After bottle blowing, the bottle body is hazy and brittle, fine bubbles may appear on the surface, but the preform appearance is normal.
Análisis de la causa
PET is highly hygroscopic; residual moisture triggers hydrolysis during reheating, molecular chains break, molecular weight decreases and acetaldehyde and micropores are produced, scattering light to form haze; preforms stored in damp conditions are most prone to this.
Solución
①Fully dehumidify and dry preforms before use (reference 140~160℃, 4~5 hours, dew point ≤-40℃); ②extend drying by 30~60 minutes for damp-stored inventory preforms; ③sealed storage to prevent moisture absorption; ④new vs. old preform comparison test for quick verification.
Conclusión clave
For PET haze, first check the preform's moisture; one new preform is enough for comparison.
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