Processing Machinery
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PMMA Melt Overheating Yellowing
Fenómeno del problema
Transparent products are yellow overall with decreased light transmittance, degraded material is visible when cleaning the barrel, and yellowing is reduced after lowering the temperature.
Análisis de la causa
PMMA is heat-sensitive; excessively high melt temperature or excessively long residence time causes thermal degradation yellowing; stagnant material carbonized in barrel dead corners can also cause yellow spots on products.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solución
①Control melt temperature within the reasonable range of 200~250℃; ②shorten barrel residence time; ③clean barrel dead corners; ④stabilize production rhythm to avoid material sitting for long periods.
Conclusión clave
Yellowing is an irreversible result of thermal degradation; temperature and residence time management is the core of maintaining PMMA optical quality, and yellowed products can only be scrapped.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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