Molds & Tooling
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PVC Yellowing Graded Early Warning
Fenómeno del problema
Slight yellowing of products was not taken seriously; after continued production it quickly turned brown and black, and the whole batch was scrapped
Análisis de la causa
The color evolution of PVC degradation is a graded early warning: yellowing at 200-210°C, browning with HCl release at 210-220°C, blackening above 230°C; conjugated polyene sequences develop color, and color is the indicator of degradation degree
Solución
①Immediately lower temperature and troubleshoot upon finding yellowing; ②scrap the entire batch of browned material and do not reuse it; ③establish a color grading and disposal comparison table to train operators; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability
Conclusión clave
Color is the thermometer of PVC degradation; yellow means warn, brown means stop, black means scrap—graded response is written into the work instruction; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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