Extrusion & Post
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PE Film Gels and Fisheyes
Problem Phenomenon
Gel particles and fisheyes appear on the surface of LDPE/LLDPE/HDPE blown or cast films, causing ink breaks during printing and lamination, obvious on transparent films.
Cause Analysis
Unplasticized particles, degraded cross-linked matter or foreign impurities mix into the melt; LLDPE/HDPE has high molecular weight and high plasticization difficulty, and gels are more obvious when the screen pack mesh is insufficient or damaged; the film thickness is only 10~50μm, and any melt unevenness will show.
Solution
①Use a dedicated screw with barrier section + mixing section to improve the plasticization uniformity; ②densify the screen pack with a reasonable gradient configuration; ③clean the dead corners of the die head and barrel; ④control the regrind quality and ratio; ⑤strengthen raw material cleanliness management.
Key Takeaway
Troubleshoot PE film gels in the three categories of 'unplasticized/cross-linked/contaminated': plasticization and screen pack are the main line, dead corners and regrind are hidden dangers; film is a magnifying glass of melt uniformity, and plasticization must be more than sufficient.
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