Material Drying
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PPO Discoloration and Thermal History
Problem Phenomenon
[Problem Phenomenon] PPO products turn yellow and dark in color, with hue drifting between batches
Cause Analysis
Excessive melt temperature, residence time exceeding 2 hours, and drying temperature exceeding 150°C can all cause discoloration; discoloration often indicates that the material has already degraded; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Measure actual melt temperature and residence time; check drying temperature records; when discoloration is severe, clean the barrel and check for carbonized material in dead spots; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Three-way troubleshooting for PPO discoloration: melt temperature, residence and drying temperature, check residence first; 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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