Extrusion & Post
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Poor transparency of linear low-density polyethylene blown film
Problem Phenomenon
The film has high haze and transparency does not meet requirements.
Poor transparency affects product appearance and display effect, which is especially important in packaging film and optical film.
Cause Analysis
(1) Linear low-density polyethylene has high crystallinity; crystalline regions scatter light, resulting in high haze
(2) Melt temperature is on the low side and plasticization is insufficient
(3) Slow cooling rate results in high crystallinity
(4) The raw material contains impurities or gel
(5) The film surface is rough
Solution
(1) Appropriately increase extrusion temperature to the higher value within the 190-250°C range for full plasticization
(2) Improve air ring cooling efficiency, accelerate cooling and reduce crystallinity
(3) Select grades with good transparency or add nucleating agents to refine crystal grains
(4) Strengthen filtration, using 80-120 mesh screens to remove impurities
(5) Polish the die to improve film surface finish
Key Takeaway
Poor transparency is caused by high crystallinity or impurities and needs to be improved by increasing temperature, accelerating cooling and selecting suitable materials.
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