Extrusion & Post
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Excessive thermal shrinkage of EAA film
Problem Phenomenon
The thermal shrinkage of EAA film at 80°C is >12%, exceeding the 5% dimensional stability requirement
Cause Analysis
EAA extrusion orientation is released after heating, causing large shrinkage; EAA has a large thermal expansion coefficient; film cooling freezes a large amount of orientation stress
Solution
1) Reduce the extrusion draw ratio to reduce orientation freezing; 2) Anneal the film at 60-80°C to release orientation stress; 3) Add 5-10wt% rigid resin to reduce thermal shrinkage; 4) Use a biaxial stretching process to balance orientation
Key Takeaway
Film thermal shrinkage is caused by orientation freezing; reducing the draw ratio and annealing treatment are the key
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