Processing Machinery
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PC Discoloration and Yellowing
Problem Phenomenon
[Problem Phenomenon] PC products turn yellow with color drift, more obvious on transparent parts
Cause Analysis
Excessive melt temperature and long residence cause thermal degradation; shear overheating; regrind contamination; yellowing indicates that the molecular weight has already dropped; when troubleshooting on site, verify each item according to this mechanism one by one, and avoid blindly adjusting the machine based on experience alone
Solution
Measure the actual melt temperature and shorten the residence; reduce shear; regrind management; clean the yellowed material; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes, so as to locate effective measures
Key Takeaway
PC yellowing is a degradation alarm; check the melt temperature, residence and shear; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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