Injection Molding
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PMMA Yellowing
Problem Phenomenon
Transparent parts turn yellow.
Cause Analysis
Excessive melt temperature or too long residence causes thermal degradation; fast injection shear heat generation also causes yellowing.
Solution
①Control the melt temperature at the lower limit of the 220~250℃ range; ②Shorten the residence time; ③Slow~medium speed injection; ④Purge the barrel at startup and shutdown.
Key Takeaway
Yellowing = thermal history exceeded.
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