Injection Molding
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Post-shrinkage of PBT injection molded parts
Problem Phenomenon
PBT products continue to shrink after demolding, the size keeps changing, affecting assembly accuracy.
Cause Analysis
PBT cools quickly in the mold and crystallization is incomplete; after demolding, crystallization continues at ambient temperature (post-crystallization), accompanied by volume shrinkage.
Solution
Ensure the mold temperature is high enough (80-120°C) for sufficient crystallization; extend the cooling time; anneal at 120°C/1-2h after molding.
Key Takeaway
The root cause of PBT post-shrinkage is incomplete crystallization; mold temperature and annealing are the control means.
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