Injection Molding
3 visualizaciones
PET Preform White Haze Crystallization (Slow Cooling)
Fenómeno del problema
The preform, especially the middle and lower part of the body, presents a milky white hazy turbidity and loses transparency; the white haze cannot be eliminated after blowing.
Análisis de la causa
Insufficient cooling rate after injection or melt temperature too high causes PET to form spherulitic crystallization in the mold; the crystallized zone scatters light producing white haze, and this defect cannot be reversed in the blowing process.
Solución
①Reduce the melt temperature to within the process window; ②strengthen mold cooling (mold temperature 5~15℃) and shorten cooling time; ③check whether the hot runner is locally overheated; ④improve rapid cooling efficiency after injection.
Conclusión clave
White haze crystallization is an irreversible defect and must be prevented at the preform injection stage; controlling melt temperature and cooling rate is the core, and preforms with white haze should be directly scrapped.
¿Le ha resultado útil?
0 personas encontraron esto útil
¡Gracias por sus comentarios!