Material Drying
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Product dense silver streaks/bubbles
Problem Phenomenon
Large areas of silver streaks and tiny bubbles appear on PEI injection molded products
Cause Analysis
Insufficient drying with moisture content >0.05% (PEI saturated water absorption 1.25%, requires 150°C/4-6h drying); processing temperature too high exceeding the safe window (>400°C), causing decomposition and gas generation
Solution
Strictly implement 150°C/4-6h drying to make moisture content <0.02%; control the maximum melt temperature ≤390°C; increase back pressure to extrude gas
Key Takeaway
The strong hygroscopicity of PEI (1.25%) is the main cause of silver streaks and bubbles
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