Extrusion & Post
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LDPE Film Strain Hardening Fluctuation
Problem Phenomenon
Bubble width and internal pressure are unstable, and the film shows wrinkles and weak spots.
Cause Analysis
The melt is stretched too fast longitudinally and strain hardening occurs; although LDPE has high melt strength, it still occurs when the formulation has many low-molecular-weight components.; During on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Reduce the draw ratio; ②Optimize the formulation to improve strain hardening stability; ③Haul off smoothly; ④Check resin batch differences.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
Strain hardening is instability at the rheological level; matching the formulation with the draw ratio is the control key.; After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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