The main factors affecting the transparency of packaging bags are as follows:
1. Dispensing issues
Improper mixing procedures will result in insufficient mixing of the main agent and curing agent. There may be “colloidal particles”.
2. The adhesive itself is black
The color of the adhesive itself is too dark, with dark yellow, yellowish red, and sometimes even dark red like soy sauce soup. It is also the corresponding color remaining on the film. Therefore, when high transparency is required, a light yellow or even colorless high-transparency adhesive should be selected.
3. Transparency of substrate
When there are obvious quality problems such as “shark skin”, “flow marks”, and crystal dots on the surface of the inner substrate, it will seriously affect the transparency of the composite product. When printing, the fog ink transferred to the non-graphic part will also significantly affect the transparency of the composite film.
4. Improper temperature setting of drying tunnel
When entering the drying channel at the beginning, the temperature is too high and the drying speed is too fast, so that the solvent on the surface of the glue layer will quickly evaporate, resulting in a local increase in the concentration of the glue on the surface and scaling on the surface. When the heat penetrates into the glue layer, the solvent under the glue film evaporates and penetrates the glue film to form a ring like a crater. One circle after another will also make the glue layer uneven, which is also called “orange peel”. Therefore, the temperature of the oven should gradually increase from the inlet to the outlet, from low to high, and have a gradient so that the solvent can evaporate in an orderly and continuous manner from the inside to the outside.