Extrusion & Post
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PET film biaxial stretching
Problem Phenomenon
BOPET film breaks frequently during stretching, the thickness tolerance is large, and the corona treatment effect is uneven
Cause Analysis
Uneven crystallinity of the cast sheet makes the stretching behavior differ greatly; mismatch of the longitudinal and transverse stretch ratios and temperature causes film breakage; uneven crystallization orientation of the film affects the consistency of corona treatment; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Control the cast sheet cooling uniformly for crystallinity; ②optimize the longitudinal and transverse stretching temperature and speed ratio; ③inspect the film surface state before corona; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
BOPET's stretching window is built on cast sheet quality; uniform crystallization is the prerequisite for high-speed stable stretching; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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