Quality assurance

Process control of organic coatings with an inline fluorescence determination system

Insufficient process control of the curing and the layer thickness of lacquer and adhesive systems can lead to failing productions and with this to problems with the finished product. Especially in the field of food packaging, migration of incompletely cross-linked parts of the adhesive or lacquer systems through the package to the food is a risk for the customer. In the production of high-barrier films consisting of alternating organic and inorganic layers, the quality of each layer, in order to achieve a high overall barrier against water vapour and oxygen, is decisive. An organic layer, which is not completely cured, can lead to a defective production and thus to high economic damage. Up to now, it was not possible to measure the curing degree inline.

The team of the Fraunhofer Alliance POLO® has developed a technology to monitor the distribution of the layer thickness and the curing degree of lacquers and adhesives during the coating pro­cess. For the inspection, two different fluorescent dyes are mixed into the lacquer or adhesive system and the distribution of fluorescence intensity over the coated area is recorded by an optical measurement system.

Fraunhofer-Institut für Verfahrenstechnik und Verpackung IVV, D-85354 Freising, Germany, www.ivv.fraunhofer.de