Material Drying
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Five Mechanisms of PLA Thermal Degradation
Problem Phenomenon
After PLA extrusion the molecular weight drops greatly, and different batches degrade to different degrees at the same temperature
Cause Analysis
PLA thermal degradation has five parallel paths: trace moisture hydrolysis, zipper-type depolymerization, oxidative random chain scission, intermolecular transesterification, and intramolecular transesterification generating lactic acid; humidity is the key variable
Solution
①Strictly control moisture to cut off the hydrolysis path; ②Dual control of temperature and residence time; ③Monitor the degradation degree by molecular weight or melt index; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PLA degradation is multi-mechanism superposition; joint control of the three variables humidity, temperature and residence, and monitoring the melt index to quantify degradation; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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