Material Drying
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Color Darkening of PBT Injection-Molded Parts (Yellowing/Browning)
Problem Phenomenon
The color of PBT products changes from white or natural color to yellow or brown.
Cause Analysis
The processing temperature is too high or the residence time is too long, causing thermal oxidative degradation; insufficient drying of the raw material causes hydrolytic degradation; the regrind ratio is too high.
Solution
Strictly control the processing temperature ≤260°C; shorten the residence time; dry fully; control the regrind ratio.
Key Takeaway
PBT color change is an early warning signal of degradation.
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