Injection Molding
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Severe excessive orientation of PU
Problem Phenomenon
Longitudinal-transverse performance difference of PU products >50%, excessive orientation
Cause Analysis
Injection speed too fast, molecular chains highly oriented in the flow direction; gate design causing unidirectional flow
Solution
1) Reduce injection speed to reduce orientation; 2) Multi-point gates to reduce unidirectional flow; 3) Annealing treatment to partially release orientation
Key Takeaway
Excessive orientation is caused by fast unidirectional flow; speed reduction and multi-point gates are key
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