Wyniki wyszukiwania - BazTech

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Proces samo-dysproporcjowania enancjomerów podczas chromatografii kolumnowej

Wzorek Alicja, Kwiatkowska Magdalena, Urbaniak Mariusz, Gawdzik Barbara

Wiadomości Chemiczne

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2023

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[Z] 77, 5-6

425--448

EN

The review is devoted to self-disproportionation of enantiomers (SDE) phenomenon which has been observed for many different classes of chiral organic compounds. The SDE phenomenon occurs when the fractionation of an enantioenriched sample due the application of a physicochemical process under achiral conditions results in the variation of the proportion of the enantiomers present across the fractions, though the overall composition in terms of the sample ee remains unchanged. The SDE process can be considered in terms of separating the excess enantiomer from the racemate. The basic terminology related to SDE was described. The formation of the SDE under chromatographic conditions is the result of an association process occurring in a solution of a chiral, non-racemic compound. Information on preferred interactions leading to homo-/heterochiral supramolecules can be provided by quantum chemical calculations, NMR spectroscopy and comparison of crystal structures of the racemic and enantiomeric crystals. Several examples of the chromatographic experiments with different classes of compounds were given in two purposes 1) to highlight the possibility of application SDE during column chromatography as the method for enantiopurification of the chiral, non-racemic compounds; 2) to demonstrate that a standard workup (chromatographic purification, evaporation) can alter the stereochemical outcome of asymmetric reactions.

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Mechanical Properties of Composites Reinforced with Technical Embroidery Made of Flax Fibers

Poniecka Agata, Barburski Marcin, Urbaniak Mariusz

Autex Research Journal

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2022

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Vol. 22, no. 4

438--445

EN

The main purpose of the article is to present the new possibilities of producing composite reinforcement with the use of a computer embroidery machine. This kind of production is in line with the principles of sustainable development. The study below presents the results of strength tests of composites containing sevenfold embroidery systems. Each variant included different directions of arrangement of individual layers as a reinforcement. Flax roving was used to strengthen the composite. Flax fibers are characterized by the highest strength among all-natural fibers, at the level of 50–80 cN/tex. The composite was made using the vacuum bag method, using epoxy resin. The embroidery was made on a ZSK embroidery machine, type JCZA 0109-550. The test material was subjected to strength tests-tensile strength, tensile elongation, and bending strength, on the INSTRON machine. Based on the research, it can be concluded that the arrangement of the roving in the direction of the tensile force allowed to obtain the best mechanical properties.

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Comparison of Mechanical Properties of Biaxial and Triaxial Fabric and Composites Reinforced by Them

Barburski Marcin, Urbaniak Mariusz, Samal Sanjeeb Kumar

Fibres & Textiles in Eastern Europe

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2019

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Vol. 27, no. 1 (133)

37--44

EN

In this article, the mechanical properties of biaxial and triaxial woven aramid fabric and respective reinforced composites were investigated. Both fabrics had the same mass/m2. The first part of the experimental investigation was focused on the mechanical properties of different non-laminated aramid fabrics (biaxial and triaxial). The second part was concerned with the mechanical properties of composites made of a different combination of layers of fabric reinforced with an epoxy resin matrix in the order of biaxial+biaxial, trixial+triaxial and biaxial+triaxial. The composites were tested for tensile strength, flexural strength, strain and Young’s and flexural modulus. It can be seen from the results that the density and direction of the yarns are the most important parameters for determination of the strength of the fabric reinforced composite. The biaxial composite clearly showed better tensile strength, while the bi-tri axial order showed good flexural strength compared to the other composite combinations. These fabric reinforced composites have suitable applications in the areas of medical, protection and in the automotive industries.

PL

W artykule przedstawiono wyniki badań właściwości mechanicznych tkaniny aramidowej dwuosiowej i trójosiowej oraz kompozytów duroplastycznych wzmocnionych tymi tkaninami. Obie tkaniny posiadały tę samą masę powierzchniową. Pierwsza część badań eksperymentalnych skupiona była na analizie właściwości mechanicznych obu tkanin aramidowych. Druga część dotyczyła analizy właściwości mechanicznych kompozytów wzmocnionych tkaninami w różnej konfiguracji: dwuosiowa + dwuosiowa, trójosiowa + trójosiowa,dwuosiowa + trójosiowa. Zbadano wytrzymałości na rozciąganie oraz zginanie, odkształcenie i moduł Younga trzech kompozytów w kierunku wzdłużnym, poprzecznym oraz pod kątem 45°. Na podstawie wyników stwierdzono, że liczność oraz kierunek przędzy są najważniejszymi parametrami określającymi wytrzymałość kompozytu wzmocnionego tkaniną. Kompozyt wzmocniony dwiema warstwami tkaniny dwuosiowej wykazywał wyraźnie lepszą wytrzymałość na rozciąganie. Kompozyt wzmocniony tkaniną trójosiową i dwuosiową wykazał się największą sztywnością zginania. Tego typu wyroby kompozytowe mogą mieć szerokie zastosowanie w obszarach przemysłu medycznego, ochronnego i motoryzacyjnego.