Polyacrylonitrile can be used as a base material for thermochemical conversion into carbon. Especially nanofiber mats, produced by electrospinning, are of interest to create carbon nanofibers. Optimal stabilization and carbonization parameters, however, strongly depend on the spatial features of the original material. While differences between nano- and microfibers are well known, this paper shows that depending on the electrospinning method and the solvent used, considerable differences between various nanofiber mats have to be taken into account for the optimization of the stabilization conditions. Here, we examine for the first time polyacrylonitrile nanofiber mats, electrospun with wire electrospinning from the low-toxic dimethyl sulfoxide as a solvent, instead of the typically used needle electrospinning from the toxic dimethylformamide. Additionally, we used inexpensive polyacrylonitrile from knitting yarn instead of highly specialized material, tailored for carbonization. Our results show that by carefully controlling the maximum stabilization temperature and especially the heating rate, fully stabilized polyacrylonitrile fibers without undesired interconnections can be created as precursors for carbonization.

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.

The industrial production of prototypes made of polyurethane via silicone molds in the vacuum casting process is one of the most widespread applications of rapid tooling. The silicone molds show progressive deterioration, as the isocyanate component of the polyurethane resin diffuses into the mold cavity surface during the casting process, thus limiting their durability. Here, we present the first comprehensive description of the underlying chemical and physical mechanisms on a molecular level. It is shown that the isocyanate polymerizes inside the polydimethylsiloxane matrix with moisture to polyurea. Polyurea clusters, which emerge from the resulting interpenetrating polymer network with continuing isocyanate exposure, promote fissure formation under mechanical demolding stresses. The mechanism was investigated with a wide variety of characterization methods, and qualitative variations were demonstrated using different commercial materials. Influencing factors such as mold geometry, process flow, and different aspects of the material composition were examined experimentally. A thorough understanding of the deterioration mechanism paves the way for the development of durable molds and an economical midseries technology in plastics processing.

3D printing is a technology which has recently found its way into the fi eld of textile fabrics, from fashion design to technical textiles. By combining both technologies with their advantages, new composites with novel physical properties can be created. Increasing adhesion between both components, however, still remains challenging. This paper suggests a new method to improve the adhesion of a 3D printed object on a textile fabric by previously coating the latter with a polymer layer. In this way, adhesion can be substantially enhanced without signifi cantly changing the bending stiff ness and haptic properties of a fabric. In this study, this procedure worked especially well for printing PLA (poly(lactic acid)) on PMMA (poly(methyl methacrylate)) or PLA coatings, while for printing ABS (acrylonitrile butadiene styrene), the best textile coatings were ABS and PLA.

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.