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