Creating good adhesion on all kinds of materials has been done with Corona treatment since Vetaphone’s founder Verner Eisby, invented the technology in 1951. Corona is ideal for materials where oxygen-based molecule groups on the surface increase the adhesion, but there are a few materials that have a limited reaction with oxygen due to their chemical composition. When the oxygen no longer reacts with the surface then the saturation value of the material has been reached with Corona. This is demonstrated when measuring the surface tension in dyn/cm; as shown in the graph below where the dyne level in the example goes up to 46 dyn/cm and then remains there regardless of the Corona power applied.
Typical examples are BOPP, OPP, MOPP, PP and PVDC, but also materials that have not been pre-treated upon extrusion fall under that category, where the material can be difficult to treat with Corona.
The graph shows the relation between material factor (W·min/m2) and the reached dyne level (dyn/cm) on pre-treated BOPP.
The solution in the past has been chemical; by either priming the material or changing the chemistry in the ink or adhesive so it could adhere to the material. This is both expensive and in most cases harmful to the environment and to the machine operators using the liquid solvent primers.
The new EASI-Plasma Grafting Technology solves these problems by changing the molecules on the surface to being Nitrogen based instead of oxygen-based. The result is higher dyne levels on what was otherwise known as materials hard or impossible to treat.
For example most converters today buy the a widely used material like BOPP that is primed by default. It is not even up for discussion, as they know it cannot be printed or laminated if they buy it without the primer. But this is not the case when using the EASI-Plasma Grafting Technology where an extremely good adhesion of 60 dyn/cm can be achieved on raw untreated BOPP.
The result is not only a greener solution with less negative impact on the environment and improved work environment for the operators, but it also results in a cheaper price per square area of the final product and a thinner final material.