Material Drying
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Color darkening in PET extrusion pelletizing
Problem Phenomenon
After extrusion pelletizing of PET recycled material, pellet color obviously darkens (yellowing), IV value decreases.
Cause Analysis
Extrusion temperature too high or residence time too long causes thermal degradation, residual moisture in recycled material causes hydrolysis, screw shear too strong generates shear heat.
Solution
Control extrusion temperature 260-280°C; fully dry recycled material; use low-shear screws; nitrogen protection in the hopper to prevent oxidation.
Key Takeaway
PET recycling pelletizing color and IV value control are key indicators of recycling quality.
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