Extrusion International 2-2019

47 Extrusion International 2/2019 and moulds can easily spoil food ev- erywhere and can also cause serious illnesses. Nanotubes with antimicrobial essential oils The EU joint project “NanoPack”, launched in 2017, focuses precisely on these challenges and aims to de- velop state-of-the-art antimicrobial packaging solutions for perishable foods based on natural nanomate- rials in order to prevent outbreaks of food-borne diseases and reduce food waste due to early spoilage. The economic aspect of production, upscaling and validation (includ- ing regulatory requirements) was also considered in order to produce marketable and cost-effective food packaging. Halloysite nanotubes (HNTs) for use in food packaging are being inves- tigated as the basis for developing the new packaging solutions in the NanoPack project. By modifying the surface of this nanomaterial, essen- tial oils such as thyme oil can be ef- ficiently released integrated into a packaging film. The essential oils re- leased as steam reduce the growth of microbes both on the product surface and in the packaging room. The scientists at Fraunhofer IAP play a leading role in the development of treatment processes and the surface functionalization of HNTs as well as in compounding, i.e. the integration of particles – loaded HNTs – in poly- mer films. Measuring layer thickness with fluorescent inks Process control methods are also rel- evant in this context, which Fraun- hofer IAP will also present. In the production of thin, transparent lay- ers, such as in packaging films, in- line process control can contribute to quality assurance and improve- ment and expensive material com- ponents can be used efficiently. Through complete monitoring, the manufacturing process can be op- timized in such a way that only as much of a functional component (e.g. an oxygen barrier layer or a laminating adhesive) is used as is necessary for its function, which can lead to considerable material and cost savings. Fluorescent dyes are used as additives in the functional layer in order to measure the distri- bution of the layer thicknesses by measuring the fluorescent light. The dye is added to the coating material in such small quantities that it is not visible and the material properties are not affected. By combining nov- el packaging materials with effec- tive process control, scientists aim to make future food packaging safer and at the same time cheaper. Multilayer barrier layers against oxygen and water vapor The scientists at Fraunhofer IGB are also working on processes for func- tionalizing packaging films. In order to be able to produce the widest possible range of surface proper- ties, IGB is pursuing the approach of functionalizing polymer films using plasma/CVD and wet-chemi- cal processes – or combinations of these technologies. This creates bar- rier layers against the permeation of oxygen and water vapor for outer packaging as well as barrier layers that prevent the release of polymer additives from the outer packaging into a food or pharmaceutical prod- uct. The challenge here is that the layers must be elastic to a certain extent so that they do not break or crack on the polymers. The Fraunhofer researchers therefore realize the coatings in the form of several me- chanically decoupled layers, which are successively deposited “layer by layer” in the plasma. “By optimiz- ing various plasma process param- eters such as the type and quantity of precursor gas used, the excitation frequency, the gas flow, the pres- sure and the treatment time, we can successively produce glass-like layers with the desired barrier function and silicone-like elastic intermediate lay- ers”, explains Dr. Jakob Barz, group leader for “Plasma Technology and Thin Films” at IGB. In this way, the researchers were able to increase the barrier effect of plastic films against water vapor and oxygen by a factor of up to 1000 compared to untreated material. The deposited barrier layers can also be combined with another layer to improve food run-off when emptying a film pack- age. Biobased barrier layers Currently, Fraunhofer IGB is also conducting research on biobased layers with a barrier function against oxygen and water vapor. At ICE eu- rope, the institute presented the first barrier coatings and films that consist of 100 percent natural start- ing materials and also have anti- oxidant or antimicrobial properties. “We produce these films and coat- ings from a newly developed wa- ter-based dispersion that contains natural waxes and proteins. The Multilayer coating as barrier against oxygen and water vapor (© Fraunhofer IGB)