Material Drying
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Silvery white streaks appear on the product surface along the melt flow direction
Problem Phenomenon
Silvery white streaks appear on the product surface along the melt flow direction, distributed in fan shape or radial pattern, extending from near the gate to the interior of the product
Cause Analysis
Raw material moisture exceeds standard, vaporizing at high temperature to produce bubbles
Barrel temperature too high (exceeding the 170-230°C upper limit) causing thermal degradation
Screw speed too fast, back pressure insufficient, poor venting
Nozzle temperature low, cold slug produced entraining air
Poor mold venting, gas compressed
Solution
Fully dry the raw material, cellulose acetate butyrate drying conditions 75-85°C/3-4h, moisture content ≤0.02%
Lower barrel temperature to a reasonable value within the 170-230°C range
Increase back pressure 5-10MPa, reduce screw speed
Raise nozzle temperature to prevent cold slug
Check mold vent groove depth 0.02-0.04mm
Key Takeaway
Silver streaks are mainly caused by moisture, thermal degradation or poor venting; investigation is needed from the three aspects of drying, temperature and venting
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