Causes
- Non-homogeneous roll coating
- Insufficient electrical insulation
- Spark discharge through roll coating
- Mechanical and thermal overload
Effects
- Damage to the product
- Microroughness not as desired
- Wetting errors of inks / adhesives
- Loss of production capacity
To enable good adhesion of adhesives or inks to film surfaces, the surface tension must be changed depending on the substrate.
Corona treatment is used to set the desired polar or non-polar surface tension for wettability. On non-polar surfaces such as PE or PP, polar groups are generated by oxidation and the surface tension is temporarily increased. This improves the wetting properties and adhesive strength on the substrate.
As a further effect, impurities are removed from the surface and micro-roughness is increased. Optimum corona treatment requires a homogeneous, foreign body-free coating with uniform insulation properties and exact geometry that is easy to clean and allows long service lives.