Material Drying
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Silver streaks caused by moisture in PU processing
Problembeschreibung
White silver streaks appear on the surface of PU injection molded products
Ursachenanalyse
Raw material contains moisture >0.05%, which vaporizes during high-temperature processing to form bubbles that are stretched into silver streaks; insufficient drying or moisture condensation in the hopper
Lösung
1) Dry raw material at 80°C for 3-4h to moisture <0.02%; 2) Increase back pressure 0.5-1MPa for venting; 3) Reduce injection speed to avoid air entrapment; 4) Heat the hopper to prevent moisture condensation
Wichtigste Erkenntnis
Silver streaks are caused by moisture vaporization and stretching; drying and venting are the main countermeasures
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