Extrusion & Post
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LLDPE blown film transverse tear
Problem Phenomenon
Film transverse tear strength is poor, and bag sides crack easily after bag making
Cause Analysis
Insufficient blow-up ratio leaves transverse molecular chains not fully extended; LLDPE's extensional softness makes transverse orientation harder; biaxial mechanical properties are unbalanced; when troubleshooting on site, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
①Increase blow-up ratio to 2-4 times to balance biaxial properties; ②dual-lip air ring enhances transverse cooling and setting; ③verify tear strength by application; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
LLDPE transverse tear is opened up by the blow-up ratio; the 2-4 times range plus dual-lip air ring setting is the standard combination; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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