Extrusion & Post
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Poor Transparency of High-Density Polyethylene Blown Film
Problem Phenomenon
The film haze is high, and the transparency does not meet the requirements.
Poor transparency affects the product appearance and display effect, and is especially important in packaging films and optical films.
Cause Analysis
（1）The crystallinity of high-density polyethylene is high, and the crystalline regions scatter light, resulting in high haze
（2）The melt temperature is low, and the plasticization is insufficient
（3）The cooling rate is slow, and the crystallinity is high
（4）The raw material contains impurities or gel
（5）The film surface is rough
Solution
（1）Appropriately increase the extrusion temperature to a higher value within the 180-260°C range for sufficient plasticization
（2）Improve the air ring cooling efficiency, accelerate cooling, and reduce crystallinity
（3）Select grades with good transparency or add nucleating agents to refine the crystal grains
（4）Strengthen filtration and use 80-120 mesh filter screens to remove impurities
（5）Polish the die to improve the film surface finish
Key Takeaway
Poor transparency is caused by high crystallinity or impurities, and needs to be improved by increasing the temperature, accelerating cooling, and selecting suitable materials.
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