Blow Molding
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Severe parison sag in PVA extrusion '2079851475616104457
Problem Phenomenon
PVA extrusion '2079851475616104457 parison sag of 20-40mm, causing bottle bottom wall thickness of only 0.3-0.4mm
Cause Analysis
PVA melt strength low, parison stretches and thins under gravity; parison extrusion speed slow, increasing sag time; parison temperature too high, viscosity low, aggravating sag
Solution
1) Add slight crosslinking agent 0.3-0.5wt% to increase melt strength; 2) Increase parison extrusion speed to shorten sag time; 3) Lower parison temperature by 10-15°C to increase viscosity; 4) Wall thickness controller to compensate sag
Key Takeaway
Parison sag is caused by low melt strength; slight crosslinking and wall thickness control are key
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