Material Drying
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PMMA Surface Silver Streaks (Degradation Type)
Problem Phenomenon
Silver streaks still appear after sufficient drying; after lowering barrel temperature by 10~15℃ the silver streaks disappear, confirmed as degradation type.
Cause Analysis
Excessively high melt temperature or excessive shear causes local PMMA degradation and gas generation; the gas is stretched into silver thread-like patterns during filling; similar in appearance to moisture-type silver streaks.
Solution
①Lower barrel temperature by 10~15℃; ②shorten residence time; ③reduce screw speed and back pressure; ④clean the barrel.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
Silver streaks must be distinguished between moisture and degradation sources; if drying is ineffective, switch to temperature investigation to avoid repeated drying delaying treatment.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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