Material Drying
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Silver streaks caused by moisture during PVA processing
Fenómeno do problema
PVA injection molded product surface shows white silver streak marks
Análise das causas
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
Solução
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 entrainment; 4) Heat the hopper to prevent moisture condensation
Conclusão principal
Silver streaks are caused by moisture vaporization and stretching; drying and venting are the main countermeasures
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