is determined on foils by means of test inks and test pens. It indirectly describes the adhesion or wettability of printing inks, adhesives and varnishes on films.
In the laboratory, the surface tension of films is tested using the edge angle method.As a rule of thumb, the higher the surface tension, the better the film can be wetted and the better ink and adhesives adhere to it. Surface tensions can often be increased by corona or flame pre-treatment. This is why these processes are widely used in film processing.Typical values for films are:
PE, PP: 30-32 mN/mPET: 43 mN/mPA11: 43 mN/mPVC: 39-40 mN/mPS: 33 mN/m