Material Drying
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PC Sheet Extrusion Bubbles
Problem Phenomenon
Bubbles and bulges appear inside or on the surface of PC extruded sheets.
Cause Analysis
The raw material contains water that was not fully dried, and water vapor forms bubbles during extrusion; failure of the vacuum venting section or hopper moisture regain also introduces gas; PC has strong hygroscopicity, and drying is the prerequisite.
Solution
①Dehumidify and dry to qualified moisture content before extrusion; ②Check the vacuum degree of the vented extruder; ③Keep the hopper insulated and moisture-proof; ④Appropriately reduce the melt temperature; ⑤Stabilize the drying system.
Key Takeaway
PC extrusion: 'water content is the first cause of bubbles, venting vacuum is the insurance': drying and venting work together; PC's hygroscopicity determines that drying must run through the entire extrusion process.
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