Extrusion & Post
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LDPE Film Sharkskin
Fenómeno del problema
Periodic ripples like sharkskin appear on the film bubble surface, and the gloss of transparent film is lost
Análisis de la causa
Melt fracture is a manifestation of extrusion shear stress exceeding the critical value; die temperature too low or resin melt index too low both trigger it; the elastic melt of LDPE long branched chains is sensitive to this
Solución
① Raise the die temperature by 10-20℃; ② switch to high melt index resin; ③ add fluorinated elastomer processing aid PPA; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Conclusión clave
The essence of sharkskin is the shear critical; the three routes of raising die temperature, changing melt index, and adding PPA are selected according to cost; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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