Extrusion & Post
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Excessive thermal shrinkage rate of PET biaxially stretched film
Problem Phenomenon
The thermal shrinkage rate of PET film exceeds the standard (longitudinal >3%, transverse >2%), causing inaccurate printing registration.
Cause Analysis
Insufficient heat setting treatment after stretching (temperature on the low side or time insufficient); large draw ratio results in high internal stress; cooling is too fast.
Solution
Increase heat setting temperature to 200-230°C; increase setting time; appropriately reduce the draw ratio; control cooling rate.
Key Takeaway
PET film thermal shrinkage rate is dominated by the heat setting process.
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