Extrusion International 2-2019

48 Extrusion International 2/2019 PACKAGING FILMS – FROM THE RESEARCH dispersion can be processed using conventional coating techniques,” explains Dr. Michaela Müller, head of the IGB research group “Poly- meric Interfaces and Biomaterials”. The big advantage is that the lay- ers are also 100 percent degradable and can thus help to reduce plastic waste. The development is part of the IGF project BioActiveMaterials, in which the Fraunhofer IVV is also involved. Functionalization for lamination and adhesion The Stuttgart/Germany research- ers are modifying polymer films with specific chemically functional groups in order to change surface properties that are required for subsequent process steps such as adhesion. Amino functionalization can also be limited to the edge area of packaging films using gas-phase and wet-chemical process steps and used for laminating the films. Safe food through physical disinfection For a longer shelf life of food, the packaging must be free of contami- nating germs. Depending on the material, microorganisms on pack- aging are usually inactivated by heat, gas, ionizing or UV radiation. Low-temperature plasmas used at IGB are a material-friendly alterna- tive to sterilization at high tempera- tures. They are not only suitable for creating layers, but can also inacti- vate microorganisms due to reactive molecules and UV radiation in the plasma process. “With plasma steril- ization, even highly resistant endo- spores of different Bacillus species become unable to reproduce after relatively short treatment times”, says Barz. In addition, scientists at Fraun- hofer IGB have further developed UV treatment in order to minimize the number of reproductive micro- organisms on surfaces. With new, specially designed excimer lamps or the latest UV LED technology, pack- aging films can be sterilized quickly and effectively. These processes can be scaled up on packaging machines and adapted to individual require- ments. Rollcoater for high-speed finishing The market for packaging films is ex- tremely price-sensitive. Fraunhofer FEP devotes itself to this aspect by developing highly productive fin- ishing processes, which are char- acterized in particular by very high speeds. One example is the produc- tion of transparent barrier layers of aluminum oxide against external influences such as moisture or oxy- gen on plastic films using plasma-ac- tivated high-rate deposition at web speeds of several meters per second. Therefore, Fraunhofer FEP operates so-called roll coaters, which can ef- ficiently coat film material with a width of up to 700 mm and web lengths of several kilometers. The researchers are currently working on qualifying this established tech- nology for use on biobased materi- als. A further example is the modifica- tion of polymer materials when they already exist as films. For this purpose, Fraunhofer FEP operates a roll-to-roll system that uses elec- tron beam irradiation to modify the structure of the polymer molecules. Effects such as the adaptation of the modulus of elasticity or the ther- mal resistance can be achieved. The proof for fossil-based polymer films has already been provided in the past. The extent to which the ef- fects can also be determined with biobased materials is currently be- ing investigated. Dr. Steffen Gün- ther explains: “This treatment takes place at atmospheric pressure and not under vacuum. The pilot plant at Fraunhofer FEP atmoFlex 1250 is used for this purpose. Due to its web width of 1250 mm, a high through- put in the treatment of films at web speeds of up to 150 m/min can be achieved. Both aspects allow a very cost-efficient processing of the films.” With their research, the three Fraun- hofer Institutes want to make a significant contribution to waste avoidance. While at the same time increasing the shelf life of food, the approaches presented for the devel- opment of biobased packaging films are intended to generate positive benefits for customers, the environ- ment and producers. The scientists from the Fraunhofer Institutes IAP, IGB and FEP present- ed the research results, the latest coated packaging films and the first packaging film with encapsulated essential oil at ICE europe in Munich, Germany. Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP Winterbergstr. 28, 01277 Dresden, Germany www.fep.fraunhofer.de Green fluorescence of a dye solution excited with blue light (© Fraunhofer IAP) Fluorescence of a lacquer strip