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In this study, electron beam (EB) curable acrylates are investigated for their use as planarization layers. Planarization layers can be used in multilayer thin film encapsulations for all kinds of flexible electronics, such as organic light emitting diodes (OLED), organic photovoltaics (OPV) and printed switching circuits, antennas, and sensors. Planarization layers cover particles and defects of the substrate and thus a plain smooth surface is created for optimized growing conditions of thin films, optimizing encapsulation properties. The thin film encapsulation prevents organic electronics from degradation due to invasive oxygen and water vapor. Several commercially available monomers and oligomers with different molar mass and number of reactive double bonds are investigated. The acrylates are deposited on polyethylene terephthalate (PET) web and glass substrates and cured by EB. The surfaces are analyzed using white light interferometry (WLI) and scanning electron microscopy (SEM). Density measurements and nanoindentation are also carried out to get information about the volume shrinkage and the elastic modulus. The correlation between chemical properties, degree of crosslinking, volume shrinkage and surface roughness are investigated. This work demonstrates that electron beam curing of acrylates is a promising method to generate smooth surfaces. It presents an increasing degree of crosslinking and volume shrinkage with decreasing molecular weight between crosslinks. Also, for comparable molecular weight between crosslinks, the volume shrinkage is higher for acrylates forming thermoplastics than for elastomers or duromers.

Structural parts made of fiber reinforced plastics do not play a predominant role in automobile mass production due to the costs associated with storage condition, low level of automation, long processing times and safety and health regulations. The idea was to develop a holistic approach which can solve the problems with understanding the whole process chain from molecule to the finished product and integration in common technical infrastructure. A promising strategy was to create a matrix resin which combines easy processing of thermoplastics with superior mechanical properties of thermosets. The new matrix can pre-applied on all type of fibers. The resulting tack-free prepreg has a long shelf life at room temperature in consequence of phase separation of matrix raw materials which can be eliminated by raising the temperature. The resulting material has high reactivity and can be cured to a thermoset within a few minutes. Individual specification of the material like glass temperature, cure rate and toughness can be adjusted.

Wood foam and metal sponges are exotic materials with interesting properties that deviate from those of conventional materials. By merging both materials, the Fraunhofer Institutes WKI, IFAM and IWU generate a novel, lightweight composite that is sustainable both in its production and in its use.

The onycophoran Epiperipatus hilkae secrets a sticky slime that solidifies almost immediately upon contact with air and under high humidy environmental condition forming a glassy like material. The general adhesive biochemical composition, the releasing and hardening mechanism have been partially described. In this study, the structural characterization of the extracellular microstructures and nanostructures forming the solid adhesive of the secretion from Epiperipatus hilkae velvet worm is presented. The adhesive secretion is formed by macro-threads, which, in their solid state, are composed of globular particles approximately 700 nm in diameter that are distributed homogeneously throughout the matrix surface, and nanoparticles approximately 70 nm in diameter that self-assemble forming fiber-like structures. Nanoparticles with non roundish forms are also observed. These 70 nm particles could be associated to proteins that form high density coverage films with low roughness; suggesting the formation of two dimensional ordered films. A crystalline and an amorphous phase composes the solidified secretion. The glassy or viscoelastic properties depend on the time in contact with air before being adhered to a solid surface and/or the mechanical stimulus; suggesting a key role of the drying on the hardening process.

For the use as RFID antennas conductive adhesives were developed and investigated which are UV curable and could be applied with printing methods like offset printing or flexography. Further investigated aspects of the materials have been the range of the distance between emitter and receiver. The resulting formulations which are based on acrylates filled with silver pigments for the conductivity allow to cure layers with a thickness of up to 50 μm with a maximal volume resistance of 1.6 x 10 -5 Ω/cm.

Common available conductive adhesives are filled with about 70-90 weight percent of silver particles. There is the technical need to lower the filler content for decreasing the viscosity and the pressure to finally decrease the costs for the highly expensive silver. Our approach to decrease the silver content with at the same time similar conductivity was to use nano-sized silver particles with different modified surfaces to obtain self-organized distribution of the silver particles in the liquid adhesive film followed by conventional curing techniques like temperature or UV curing. Through the self-organization, a bridging of the particles should be achieved which gives a similar conductivity as in highly filled commercial adhesives which follows percolation theory. The influence of the surface modification on the strength of the interaction between differently modified silver particles and the distribution in the liquid adhesive was simulated with Dissipative Particle Dynamics (DPD). Surface modification was verified with surface enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS). The distribution of the silver particles in the cured adhesive film was investigated with scanning electron microscopy (SEM).