Processing Machinery
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HDPE film insufficient longitudinal strength
Problem Phenomenon
The longitudinal tensile strength of the film is tested to be low, and it is easy to tear longitudinally after bag making.
Cause Analysis
A too small draw ratio causes insufficient longitudinal molecular orientation; too high melt temperature causes molecular chain breakage; too fast cooling and uneven crystallization also weaken the strength.; when troubleshooting on site, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Increase the draw ratio to 1.5~3 times; ②lower the rear section temperature of the barrel to prevent degradation; ③adjust the frost line to optimize the cooling gradient; ④test the degree of orientation.; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Longitudinal strength is jointly determined by orientation and molecular weight; draw ratio and temperature are the main process levers.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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