X-ray studies on polyurethanes containing arabinose-based polyurethanes the phase sugar derivatives in the main chain were separation is defined least of all. Glucoseperformed. I t was demonstrated that the and dulcitol-based polymers are intermemicrophase separation of rigid and flexible diates as to their supermolecular organizafragments was dependent on the nature of tion. Supermolecular organization models sugar derivatives. The supermolecular or-for block copolyurethanes under investiganization in disaccharide-based polymers gation were proposed. is the most ordered one. In xylose-and

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Domestic and imported graphite-containing crucibles are investigated by the petrographic method after operation in holding furnaces for casting aluminum alloys and copper bronze.Carbon and oxide compositions have been used traditionally in the technology for crucibles for melting and casting nonferrous metals. The carbon component provides thermal stability and metal and slag resistance, whereas the oxide component provides the strength properties.A charge for manufacturing crucibles usually contains natural fine-flake graphite with a low content of ash and a high degree of anisotropy of the physical properties, which makes it possible to choose a preferable orientation of the flakes and thus control the properties and application range of the material. In addition, graphite is less capable of planar oxidation, being a more stable phase than more ordered carbon such as coke or ash. The charge also contains silicon carbide, ferrosilicon, metallic silicon, and other additions that are less oxidizable than graphite or impede the process of its oxidation. For the same purpose graphite-containing crucibles are covered with a glaze whose components amount to 2 -5 wt

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