Extrusion & Post
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Poor Transparency of Polypropylene Blown Film
Problem Phenomenon
The film haze is high, and the transparency does not meet the requirements.
Poor transparency affects product appearance and display effect, and is especially important in packaging films and optical films.
Cause Analysis
(1) Polypropylene has high crystallinity, and the crystalline regions scatter light, resulting in high haze
(2) The melt temperature is too low, and 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 the higher value within the range of 200-280°C for full plasticization
(2) Improve the cooling efficiency of the air ring, accelerate cooling, and reduce crystallinity
(3) Select a grade with good transparency or add a nucleating agent to refine the crystal grains
(4) Strengthen filtration, using an 80-120 mesh filter screen to remove impurities
(5) Polish the die to improve the surface finish of the film
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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