Material Drying
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PC Silver Streaks from Insufficient Raw '2079851475616104451
Problembeschreibung
Fan-shaped silver-white streaks appear on the PC product surface, mostly radiating outward from the gate, transparent parts and appearance parts are directly scrapped, often accompanied by tiny bubbles.
Ursachenanalyse
PC is a strongly hygroscopic engineering plastic; trace moisture rapidly vaporizes in the 280~320°C barrel, enters the cavity with the melt, and leaves silver streaks on the surface; insufficient drying time, the dryer's dew point not meeting the standard, or secondary moisture absorption after drying are the main causes, and PC allows an extremely low moisture content.
Lösung
①Use a dehumidifying dryer with dew point ≤-40°C; ②Fully dry according to grade requirements (generally around 120°C, more than 4 hours); ③Use the Karl Fischer method to verify moisture content ≤0.02% before starting the machine; ④Store sealed after drying and use up within a limited time; ⑤Appropriately reduce injection speed and increase back pressure for venting.
Wichtigste Erkenntnis
PC silver streaks are almost always a drying problem: PC is extremely sensitive to moisture, and moisture content must be managed at the 0.02% level; verify moisture before adjusting the machine, speak with data, instead of repeatedly trying process parameters, which only wastes time and material.
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