Extrusion & Post
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Material Overflow at EVOH Vacuum Vent
Problem Phenomenon
Material overflows at EVOH extrusion vacuum vent, vent hole clogged
Cause Analysis
EVOH melt viscosity low, overflowing at vacuum section; vacuum section temperature too high, viscosity even lower, aggravating overflow; vent hole design improper
Solution
1) Reduce vacuum section temperature by 5-10°C to increase viscosity; 2) Add baffle above vent hole to prevent overflow; 3) Increase screw speed to accelerate conveyance and reduce residence
Key Takeaway
Overflow is caused by low melt viscosity; cooling and adding baffle are key
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