Material Drying
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ASA insufficient drying silver streak
Fenómeno do problema
ASA product surface shows silver streaks and misty water marks, distributed along the flow direction near the gate, and the product is accompanied by impact strength decrease and embrittlement.
Análise das causas
ASA is hygroscopic, residual moisture vaporizes in the 190~230℃ melt to form gas streaks; Ravago clearly points out that moisture at molding temperature causes both appearance defects and product embrittlement.
Solução
①Full pre-drying at 80~85℃×3~5 hours (Toray TOYOLAC standard); ②hopper heat preservation to prevent moisture regain; ③when silver streaks appear, verify drying first before adjusting process; ④extend drying time in humid seasons.
Conclusão principal
90% of ASA silver streaks originate from insufficient drying; 3~5 hours drying is a supplier specification rather than a suggestion; if the moisture problem is not solved, any process adjustment is only treating the symptoms.
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