Material Drying
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Silver Streaks Caused by Insufficient Drying of PEEK
Problem Phenomenon
Silvery whitish filamentary streaks appear on the surface of PEEK products along the flow direction; in severe cases they are accompanied by bubbles and a hazy appearance, mostly occurring near the gate and in thin-wall areas.
Cause Analysis
Although PEEK has a low water absorption rate, its processing temperature is as high as above 380℃; trace moisture (exceeding 0.02%) vaporizes at high temperature and triggers hydrolytic degradation, and the gas leaves silver streak marks on the surface as the melt fills.
Solution
①Strictly perform dehumidifying drying at 150~160℃×3~4 hours and verify the moisture content with a moisture analyzer; ②Keep the hopper warm after drying to prevent moisture regain; ③When silver streaks appear, measure moisture first before investigating other factors.
Key Takeaway
PEEK silver streak investigation should follow the order of moisture first, equipment second; drying is the lowest-cost defect prevention means; moisture content verification should be incorporated into the first-article inspection process of each shift, avoiding judgment based on experience.
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