For more information refer to www.gelifesciences.com/handbooks 2-D Electrophoresis Principles and Methods GE Healthcare Life Sciences 2-D Electrophoresis using immobilized pH gradients Principles and Methods 80-6429-60 Affinity Chromatography

Electrospun poly(acrylonitrile) (PAN) nanofibers are typical precursors of carbon nanofibers. During stabilization and carbonization, however, the morphology of pristine PAN nanofibers is not retained if the as-spun nanofiber mats are treated without an external mechanical force, since internal stress tends to relax, causing the whole mats to shrink significantly, while the individual fibers thicken and curl. Stretching the nanofiber mats during thermal treatment, in contrast, can result in fractures due to inhomogeneous stress. Previous studies have shown that stabilization and carbonization of PAN nanofibers electrospun on an aluminum substrate are efficient methods to retain the fiber mat dimensions without macroscopic cracks during heat treatment. In this work, we studied different procedures of mechanical fixation via metallic substrates during thermal treatment. The influence of the metallic substrate material as well as different methods of double-sided covering of the fibers, i.e. sandwiching, were investigated. The results revealed that sandwich configurations with double-sided metallic supports not only facilitate optimal preservation of the original fiber morphology but also significantly accelerate the carbonization process. It was found that unlike regularly carbonized nanofibers, the metal supports allow complete deoxygenation at low treatment temperature and that the obtained carbon nanofibers exhibit increased crystallinity.

Polyacrylonitrile (PAN) nanofibers, prepared by electrospinning, are often used as a precursor for carbon nanofibers. The thermal carbonization process necessitates a preceding oxidative stabilization, which is usually performed thermally, i.e., by carefully heating the electrospun nanofibers in an oven. One of the typical problems occurring during this process is a strong deformation of the fiber morphologies—the fibers become thicker and shorter, and show partly undesired conglutinations. This problem can be solved by stretching the nanofiber mat during thermal treatment, which, on the other hand, can lead to breakage of the nanofiber mat. In a previous study, we have shown that the electrospinning of PAN on aluminum foils and the subsequent stabilization of this substrate is a simple method for retaining the fiber morphology without breaking the nanofiber mat. Here, we report on the impact of different aluminum foils on the physical and chemical properties of stabilized PAN nanofibers mats, and on the following incipient carbonization process at a temperature of max. 600 °C, i.e., below the melting temperature of aluminum.

3D printing is nowadays used for many applications far beyond pure rapid prototyping. As tools to prepare custom-made objects which may be highly complex, different 3D printing techniques have emerged into areas of application where the mechanical, thermal, optical and other properties have to meet high requirements. Amongst them, applications for space, e.g. for microsatellites, make extreme demands regarding the stability under high temperatures. Nevertheless, polymeric 3D printed materials have several advantages for space application in comparison with metal objects. Here we thus investigate the impact of temperatures up to 85 °C and 185 °C, respectively, on typical 3D printing materials for fused deposition modeling (FDM) or stereolithography (SLA). The materials are found to differ strongly in terms of mechanical properties and dimensional stability after the treatment at higher temperature, with SLA resins and co-polyester (CPE) showing the best dimensional stability, while acrylonitrile-butadiene-styrene (ABS) and SLA resin after long UV post-treatment have the best mechanical properties.

Electrospun polyacrylonitrile (PAN) nanofi brous mats belong to typical precursor materials of carbon nanofibres. They have, however, the problem that they need to be fi xed or even stretched during stabilisation and ideally also during carbonisation in order to avoid undesired conglutinations and deformations of the original nanofi bre morphology, resulting in brittle behaviour of the macroscopic nanofi brous mat, which impedes several applications. In an earlier investigation, blending PAN with ZnO was shown to increase fi bre diameters and lead to unproblematic stabilisation and carbonisation of nanofi brous mats. ZnO, on the other hand, may have a negative impact on biotechnological applications such as tissue engineering. Here, we thus report on the morphological and chemical modifi cations due to blending PAN electrospinning solutions with diff erent amounts of casein. By optimising the PAN : casein ratio, relatively thick, straight nanofibres are obtained, which can be stabilised and carbonised unambiguously, without the well-known negative impact on cell adhesion due to the addition of ZnO.Elektropredene nanovlaknate koprene iz poliakrilonitrila (PAN) predstavljajo tipične prekurzorje za izdelavo ogljikovih nanovlaken. Med stabilizacijo in po možnosti tudi med karbonizacijo morajo biti pritrjene, da bi lahko preprečili neželeno zlepljenje in deformacijo prvotne nanovlaknate oblike, ki vodi v krhkost makroskopske nanovlaknate koprene in zmanjša možnosti njene uporabe. V predhodni raziskavi je bilo ugotovljeno, da mešanje PAN z ZnO vpliva na povečanje premera vlaken in omogoči stabilizacijo ter karbonizacijo nanovlaknatih kopren. ZnO pa lahko po drugi strani negativno vpliva na biotehnološke aplikacije, kot je tkivni inženiring. V članku so zato predstavljene morfološke in kemijske modifi kacije, ki so bile dosežene z uporabo predilnih raztopin za elektropredenje PAN z dodatkom različnih količin kazeina. Z optimizacijo razmerja PAN : kazein dobimo relativno debela, ravna nanovlakna, ki jih je moč stabilizirati in karbonizirati, brez da bi zaradi dodatka ZnO prišlo do dobro znanega negativnega vpliva na celično adhezijo.