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Das Vakuumgießen von Polyurethan (PUR) ist ein industriell weitverbreitetes Verfahren zur Herstellung von Prototypen und Kleinserien. Dabei wird zur Vervielfältigung eines Urmodells ein Gießwerkzeug aus Silikon hergestellt. In dieses wird dann ein reaktives PUR-Gießharz gefüllt, welches aus den zwei Komponenten Isocyanat und Polyol besteht. Aufgrund der Diffusion des Isocyanats in die Silikon-Oberfläche, kommt es zur Alterung des Silikons, was nach wenigen Gießzyklen zur Beschädigung der Werkzeugkavität führt. Obwohl das Verfahren seit Jahrzehnten industriell eingesetzt wird, gab es bisher kaum eine wissenschaftliche Auseinandersetzung mit der Thematik. Deshalb liefert diese Arbeit eine eingehende materialwissenschaftliche Analyse der Alterung von Silikon-Gießwerkzeugen beim Polyurethan-Vakuumgießen. Dabei werden die wichtigsten Einflussfaktoren sowie die chemischen Mechanismen auf molekularer Ebene erklärt und die makroskopischen Erscheinungsmerkmale der Alterung quantifiziert. Die Polymerisation des absorbierten Isocyanats innerhalb des Silikons mit eingelagertem Wasser zu Polyharnstoff führt zur sukzessiven Alterung und schließlich zur Beschädigung des Gießwerkzeugs unter Entformungsspannungen. Zur Beschreibung des nicht-Fick‘schen Diffusionsprozesses werden verschiedene mathematische Modelle vorgestellt. Weiterhin werden verschiedene Methoden zur Prävention der Alterung vorgestellt und hinsichtlich ihrer Eignung für das Vakuumgießen experimentell untersucht. Mit Hilfe von Beschichtungen und Füllstoffen konnten im Labormaßstab bereits vielversprechende Resultate erzielt werden, die den Grundstein für eine signifikante Erhöhung der Werkzeugstandzeit legen., Vacuum casting of polyurethane (PUR) is an industrially well-established process for the production of prototypes and small batches. For the replication of the master pattern, a silicone casting mold is manufactured. A reactive PUR casting resin is then poured into the mold, which consists of the two components isocyanate and polyol. The diffusion of the isocyanate into the silicone surface causes aging of the silicone, which leads to damage of the molds cavity after a few casting cycles. Although the process has been used industrially for decades now, there has so far been hardly any scientific examination of the subject. This thesis therefore provides an extensive materials science analysis of the aging of silicone molds in polyurethane vacuum casting. The most important influencing factors as well as the underlying chemical mechanisms are explained on a molecular level and the macroscopic manifestations of the aging are quantified. The polymerization of the absorbed isocyanate within the silicone with embedded water to form polyurea leads to successive deterioration of the mechanical properties and finally to material breakdown under demolding tension. Various mathematical models are presented to describe the non-Fickian diffusion process. Moreover, different methods for the prevention of the ageing process are introduced and examined experimentally regarding their suitability for vacuum casting. Using coatings and fillers, promising results have been obtained on a laboratory scale, which lay the foundation for a significant increase in the molds service life.

New ecological trends and changes in consumer behavior are known to favor biofilm formation in household appliances, increasing the need for new antimicrobial materials and surfaces. Their development requires laboratory-cultivated biofilms, or biofilm model systems (BMS), which allow for accelerated growth and offer better understanding of the underlying formation mechanisms. Here, we identified bacterial strains in wildtype biofilms from a variety of materials from domestic appliances using matrix-assisted laser desorption/ionization-time of flight mass spectroscopy (MALDI-TOF-MS). Staphylococci and pseudomonads were identified by MALDI-TOF-MS as the main genera in the habitats and were analyzed for biofilm formation using various in vitro methods. Standard quantitative biofilm assays were combined with scanning electron microscopy (SEM) to characterize biofilm formation. While Pseudomonas putida, a published lead germ, was not identified in any of the collected samples, Pseudomonas aeruginosa was found to be the most dominant biofilm producer. Water-born Pseudomonads were dominantly found in compartments with water contact only, such as in detergent compartment and detergent enemata. Furthermore, materials in contact with the washing load are predominantly colonized with bacteria from the human.

Thermally stabilized and subsequently carbonized nanofibers are a promising material for many technical applications in fields such as tissue engineering or energy storage. They can be obtained from a variety of different polymer precursors via electrospinning. While some methods have been tested for post-carbonization doping of nanofibers with the desired ingredients, very little is known about carbonization of blend nanofibers from two or more polymeric precursors. In this paper, we report on the preparation, thermal treatment and resulting properties of poly(acrylonitrile) (PAN)/poly(vinylidene fluoride) (PVDF) blend nanofibers produced by wire-based electrospinning of binary polymer solutions. Using a wide variety of spectroscopic, microscopic and thermal characterization methods, the chemical and morphological transition during oxidative stabilization (280 &deg, C) and incipient carbonization (500 &deg, C) was thoroughly investigated. Both PAN and PVDF precursor polymers were detected and analyzed qualitatively and quantitatively during all stages of thermal treatment. Compared to pure PAN nanofibers, the blend nanofibers showed increased fiber diameters, strong reduction of undesired morphological changes during oxidative stabilization and increased conductivity after carbonization.

This thesis examines from a public law perspective the legal institutionalization of human rights impact assessments ( HRIA ) with a focus on the EU. In a first step, the thesis analyzes why EU institutions have to assess the human rights impacts of their acts regardless of where these impacts occur. In a next step, the thesis analyzes and evaluates the legal rules and principles that determine how HRIAs are to be carried out, considering in particular that HRIAs are instruments to respond to factual and normative uncertainty. A comparison with the law of environmental impact assessment helps to shed light on how law, scientific analysis and political discretion relate to each other in this regard. Finally, the thesis is drawing on compliance and regulation theories to identify factors that can contribute to ensuring that the rules and principles guiding and regulating the conduct of HRIAs are respected. These factors are used to evaluate the ability of institutionalized HRIAs in the EU to influence decision-making and to protect human rights through ex-ante procedures.

Electrospinning is a new technology whose scope is gradually being developed. For this reason, the number of known polymer–solvent combinations for electrospinning is still very low despite the enormous variety of substances that are potentially available. In particular, electrospinning from low-toxic solvents, such as the use of dimethyl sulfoxide (DMSO) in medical technology, is rare in the relevant scientific literature. Therefore, we present in this work a series of new polymers that are applicable for electrospinning from DMSO. From a wide range of synthetic polymers tested, poly(vinyl alcohol) (PVOH), poly(2ethyl2oxazolene) (PEOZ), and poly(vinylpyrrolidone) (PVP) as water-soluble polymers and poly(styrene-co-acrylonitrile) (SAN), poly(vinyl alcohol-co-ethylene) (EVOH), and acrylonitrile butadiene styrene (ABS) as water-insoluble polymers were found to be suitable for the production of nanofibers. Furthermore, the influence of acetone as a volatile solvent additive in DMSO on the fiber morphology of these polymers was investigated. Analyses of the fiber morphology by helium ion microscopy (HIM) showed significantly different fiber diameters for different polymers and a reduction in beads and branches with increasing acetone content.

Fused deposition modeling (FDM) is a three-dimensional (3D) printing technology that is usually performed with polymers that are molten in a printer nozzle and placed line by line on the printing bed or the previous layer, respectively. Nowadays, hybrid materials combining polymers with functional materials are also commercially available. Especially combinations of polymers with metal particles result in printed objects with interesting optical and mechanical properties. The mechanical properties of objects printed with two of these metal-polymer blends were compared to common poly (lactide acid) (PLA) printed objects. Tensile tests and bending tests show that hybrid materials mostly containing bronze have significantly reduced mechanical properties. Tensile strengths of the 3D-printed objects were unexpectedly nearly identical with those of the original filaments, indicating sufficient quality of the printing process. Our investigations show that while FDM printing allows for producing objects with mechanical properties similar to the original materials, metal-polymer blends cannot be used for the rapid manufacturing of objects necessitating mechanical strength.