Molding Process
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EVOH Surface Stress Whitening
Problem Phenomenon
Stress whitening on stressed areas of EVOH product surfaces, affecting appearance and strength
Cause Analysis
EVOH molecular orientation under local stress causes refractive index difference and whitening; areas of internal stress concentration in the product
Solution
1) Reduce injection speed to decrease orientation stress; 2) Anneal at 80°C/2h to release stress; 3) Product design to avoid stress-concentrating sharp corners
Key Takeaway
Stress whitening is caused by orientation and internal stress; reducing orientation and annealing are key
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