Extrusion & Post
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PVA vacuum vent section material overflow
Problem Phenomenon
Material overflow at the PVA extrusion vacuum vent section, vent hole clogging
Cause Analysis
PVA melt viscosity low, overflowing at the vacuum vent section; vacuum vent section temperature on the high side, viscosity even lower, aggravating overflow; vent hole design improper
Solution
1) Lower vacuum vent section temperature by 5-10°C to increase viscosity; 2) Add a baffle above the vent hole to prevent overflow; 3) Increase screw speed to accelerate conveying and reduce residence
Key Takeaway
Overflow is caused by low melt viscosity; temperature reduction and baffle are the key
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