Material Drying
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EVOH '2079851475616104452 thick-wall bubbles
Problem Phenomenon
Dense bubbles 0.1-0.5mm appear inside EVOH injection molded thick-wall products, concentrated in the wall thickness center
Cause Analysis
Holding pressure insufficient <40MPa or holding time short with the thick-wall center not compacted; raw material contains moisture; injection speed too fast entraining air; poor mold venting
Solution
1) Increase holding pressure to 60-80MPa; 2) Extend holding time to fully compact the thick wall; 3) Fully dry the raw material to moisture <0.02%; 4) Add vent grooves or vent pins to the mold; 5) Gradually decelerate injection to avoid air entrainment
Key Takeaway
Thick-wall bubbles are caused by a combination of insufficient holding pressure, moisture, and poor venting
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