Injection Molding
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PETG injection molded product optical birefringence
Problem Phenomenon
Transparent products show colored stripes under polarized light (stress birefringence).
Cause Analysis
Uneven internal stress distribution causes refractive index anisotropy, produced by uneven filling flow and cooling.
Solution
Increase the mold temperature to reduce the cooling rate; anneal to eliminate stress; optimize gate position to improve flow.
Key Takeaway
PETG birefringence is the optical manifestation of uneven stress.
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