Processing Machinery
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Difficult PVA purging
Problem Phenomenon
PVA purging requires 2-3h, time-consuming, affecting changeover efficiency
Cause Analysis
PVA has strong adhesion forming a firm adhered layer on the screw and barrel; PVA has poor thermal stability and becomes sticky at high temperature, harder to remove
Solution
1) Flush with high-viscosity PE before purging to carry away PVA residue; 2) Lower purging temperature below the PVA softening point to reduce adhesion; 3) Use a dedicated purging compound
Key Takeaway
Difficult purging is caused by strong PVA adhesion; PE flushing and temperature reduction are the key
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