Extrusion & Post
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PP Cast Film Gel Particle (Fisheye)
Problem Phenomenon
Gel particles, fisheyes, or bright spots appear on CPP cast film surfaces, causing ink breaks and wrinkles during printing and laminating—obvious on transparent films.
Cause Analysis
Unplasticized particles, degraded crosslinked matter, or foreign impurities pass through the die with the melt; insufficient or broken screen mesh lets impurities through, and gel particles increase significantly with high regrind ratio and poor plasticization.
Solution
①Raise plasticization temperature and mixing effect to ensure full melting; ②check and replace screens (reasonable gradient configuration); ③clean dead spots in die and barrel; ④control regrind quality and ratio; ⑤strengthen raw material cleanliness management.
Key Takeaway
CPP gel particles must be distinguished into 'unplasticized' and 'contamination/crosslinking' types: the former relies on plasticization and screens, the latter on cleaning and dead-spot control; transparent film demands extremely high melt uniformity—plasticization and filtration must both be in place.
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