Molding Process
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Surface stress whitening of PU
Problem Phenomenon
Stress whitening on the surface of stressed areas of PU products, affecting appearance and strength
Cause Analysis
PU molecular orientation under local stress causes refractive index difference and whitening; internal stress concentration areas of the product
Solution
1) Reduce injection speed to reduce orientation stress; 2) Annealing treatment at 80°C/2h to release stress; 3) Product design avoiding stress concentration sharp corners
Key Takeaway
Stress whitening is caused by orientation and internal stress; reducing orientation and annealing are key
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