Extrusion & Post
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CEF film thermal shrinkage rate too large
Problem Phenomenon
The thermal shrinkage rate of the CEF film at 80°C is >12%, exceeding the 5% dimensional stability requirement
Cause Analysis
The CEF extrusion orientation is released after heating, leading to large shrinkage; CEF has a large thermal expansion coefficient; the film cooling froze 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 the thermal shrinkage rate; 4) 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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