Extrusion & Post
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PET Preform Color Streaks
Problem Phenomenon
Colored preforms show streaks or cloud-like color bands of varying shades on the body; after blowing, the color streaks are stretched and more obvious, and the appearance is unqualified.
Cause Analysis
The colorant and PET raw material are mixed unevenly, the melt is not fully homogenized during plasticization, or the temperature of each hot runner point is uneven, causing differences in the dispersion state of the color masterbatch, forming streaks.
Solution
①Switch to pre-mixed material or improve color masterbatch dispersibility; ②optimize screw plasticization and back pressure to promote homogenization; ③calibrate hot runner temperature consistency; ④check the metering accuracy of color masterbatch addition.
Key Takeaway
The root cause of color streaks lies in dispersion and temperature uniformity; transparent colored products are appearance-sensitive, and streaks should be eliminated through homogenization process and temperature control, and if necessary, replace with a color masterbatch with good dispersibility.
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