The transparency of composite film is very high, but in the composite processing of plastic film, the composite film often has problems such as insufficient transparency. So, what is the reason for affecting the transparency of the composite film? This article analyzes one by one for reference.

Improper selection of adhesives:

Such as the color of the adhesive itself is dark or the fluidity is insufficient, the leveling performance is poor, and it cannot be fully spread on the composite base film. Generally, the higher the solid content of the main glue, the better the fluidity, which is conducive to spreading on the film. In general, 75% of the glue is better than 50% of the transparent effect, 50% of the glue is better than 40% or 35% of the glue. For compliant films with high transparency requirements, the use of 50% and 40% adhesive composite is difficult to meet the requirements.

Process problems:

First of all, the drying temperature of the drying channel of the composite machine is too high, and the solvent on the surface of the adhesive liquid is quickly dispersed (steam), and the adhesive liquid is crusts on the surface prematurely. Then, when the heat goes deep into the inside of the adhesive liquid layer, the solvent under the adhesive film will vaporize. When the gas breaks through the epidermal adhesive film to form a ring like a volcanic vent, which also makes the adhesive layer not transparent enough. Secondly, if the conforming roller or scraper is defective, a certain point is not compacted, forming a neutral, which will also cause the compliant film to be opaque.

There is too much dust in the air added to the working environment, and there is also dust in the hot air sucked into the drying channel after gluing, which is stuck on the surface of the adhesive layer or sandwiched between the two layers of the base film when composite, and a lot of dust causes opacity or poor transparency. The solution is to close the glue part of the composite machine, and use a high mesh filter on the air inlet of the baking channel to block the suction of dust (that is, the dust in the hot air of the baking channel).

In addition, if there is no roll or the roll is not clean, it will make the composite film not transparent enough, or the amount of composite glue is insufficient, the glue is uneven and there is a blank, and there are small bubbles, resulting in speckles or opacity. The solution is to check and adjust the amount of glue so that it is sufficient and evenly coated, resulting in the common name of "pockmarked face film".

Other problems

It should be noted that the composite hot drum temperature is not enough, the hot melt part of the glue fails to melt, the cooling roller temperature is too high, and the failure to cool suddenly can cause poor transparency of the compliant film.

Solution: The temperature of the hot drum shall not be lower than 70 degrees, and the hot melt part of the colloid begins to melt when the temperature reaches 65 degrees, and not only the transparency is improved after melting, but the composite stiffness is also increased. Cooling roller to use cooling water or chilled water circulation cooling, the faster the cooling speed, the better the transparency, the better the flatness of the composite film, the better the firmness.