Beschichtungsprozesse vollständig kontrollieren und steuern - Inline Vernetzungsgrad und Schichtdicken messen
Effective monitoring and control of coating processes - inline measurement of the degree of crosslinking and film thickness
The Fraunhofer Institute for Process Engineering and Packaging IVV and the The Fraunhofer Institute for Applied Polymer Research IAP are currently developing an inline system for measuring the degree of crosslinking and thickness of organic coatings. This system allows measurement of the degree of crosslinking and the coating thickness across the whole of the substrate surface during production. Automatic coupling to coating systems allows full control of coating processes. The measurement system is based on two fluorescent dyes, which are mixed into the coating or adhesive system in a concentration of approximate 50 ppm. The dyes are excited by LEDs via transmitted light or incident light. A coating crosslinked in two different degrees was employed for trials carried out within the framework of a project. The fact that a greater film thickness results in a higher area concentration and hence in a higher intensity of fluorescent light was used to accurately determine th e film thickness. The nonlinear increase in the wavelength specific intensity can be attributed to the Beer-Lambert law, namely that at higher film thickness more light is absorbed by the coating.