Fiedler, Bodo

This dissertation covers production, manipulation and application of carbon nanoparticle modified polymer resin systems and their nanocomposites. Carbon nanoparticles of different morphology are considered. The experimental work including results and discussion is presented in three parts beginning with the dispersion process via three-roll mill. A novel in-line monitoring method is presented und discussed with relevant material systems. The second parts reports on permanent-magnetic manipulation of carbon nanoparticle dispersions. As a possible application of nanocomposites their performance as temperature sensors under cyclic thermal loading is presented.

Incorporation of carbon nanoparticles in high performance polymer composites promises extensive potential for enhancement of their physical properties. Here the dispersion of the particles is the crucial factor. Only a defined dispersion results in the desired adjustment of properties. On the one hand, the market offers a high variety of industrially available carbon based nanoparticles. These are: Carbon blacks (CB), multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT) and graphenes. On the other hand, the demand for nano-enabled products is given. Unfortunately, the bottleneck lies within the incorporation of these particles into the polymer, namely the carbon intermediate production. A commonly used effective technique for the dispersion of carbon-based nanoparticles into high performance epoxy resins (EP), in their liquid state, is the three roll milling (TRM) process. However, it is time consuming and requires a lot of manual handling of the material. In-line analysis enables the expansion of the technological bottleneck and leads to a cost-efficient and quality-controlled dispersion process for the future industrial application. In a first step, the carbon nanoparticles were characterized regarding their geometry, specific surface area and elementary composition. Rheological characterization of the different molecular weight epoxy resins built a starting point for further investigations. Rheo-electrical characterization of the nanocomposites revealed the applied strain amplitude as predominant driving force for dispersion and not the shear rate. Optical coherence tomography (OCT) allowed the direct evaluation of the particle size distribution over the dispersion process. Analysis of the dependency of the complex impedance on the frequency via impedance spectroscopy revealed the network formation on macro and even on micro scale. Next generation three roll mills are enabled to monitor occurring process forces. The analysis of the line forces during processing allows an assessment of the homogeneity of dispersion. The combination of these in-line quality-monitoring methods enables a process time reduction of 70 % for a demonstrator masterbatch production of typical batch size. The evaluated impact of the particle type, filler loading and epoxy resin on the viscosity during processing and the resulting thermo-mechanical, electrical and fracture behavior (mode I and II) revealed the potential for industrial applications. Here, SWCNT showed the best property enhancement regarding the electrical conductivity and fracture toughness without increase of viscosity at ultra-low filler loading of 0.01 wt.%. This allowed the manufacturing of a bright colored glass fiber reinforced polymer (GFRP) with antistatic discharge protection. Subsequently, the presented results enable the manufacturing of nano-intermediates in an efficient way with controllable dispersion quality.

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