Material Drying
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Silver Streaks Caused by Moisture in EVOH Processing
Fenómeno del problema
EVOH injection molded product surfaces show white silver streak marks
Análisis de la causa
Raw material moisture content >0.05% vaporizes during high-temperature processing forming bubbles that are stretched into silver streaks; insufficient drying or moisture condensation in the hopper
Solución
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 hopper to prevent moisture condensation
Conclusión clave
Silver streaks are caused by moisture vaporization and stretching; drying and venting are the main countermeasures
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