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Modified and Unmodified Zinc Oxide as Coagent in Elastomer Compounds

100%
Kołodziejczak-Radzimska A., Jesionowski T., Maciejewska M., Zaborski M.
Polish Journal of Chemical Technology
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2014
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vol. 16
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issue 3
63-68
EN
The aim of this work was to study the activity of unmodified and modified ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) and ethylene-propylene copolymer (EPM). In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodified and modified zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modification method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modification of zinc oxide by maleic acid is a promising technique.
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CHITIN NANOFIBRES AS REINFORCEMENT FOR HYDROXYAPATITE-BASED COMPOSITE PREPARATION

88%
Machałowski T., Kozłowski M., Kołodziejczak-Radzimska A., Jakubowicz J., Jesionowski T.
Progress on Chemistry and Application of Chitin and its Derivatives
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2022
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vol. 27
162-174
EN
The development and improvement of chitin applications have drawn special attention from the global scientific community due to their extraordinary features and abundance. In this study, β-chitin nanofibres were obtained using the ultrasonication treatment method. Then, hydroxyapatite/nanochitin (HAp/NCh) composites were prepared at different maturation times. In this case, mixtures of various amounts of β-chitin nanofibres (1%, 2%, and 5%) were added during the HAp precipitation approach. The prepared HAp/NCh materials were characterised with Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The surface of prepared specimens was observed using scanning electron microscopy. The presence of nanofibres was confirmed by non-invasive backscattering with dynamic light scattering particle size analysis. Moreover, the synergic effect of chitin nanofibres on the mechanical resistance of HAp-based composite was investigated. The sample with 5% of chitin nanofibres exhibited about 10 times higher compression strength than the pure HAp. All these results essentially indicate that the prepared material can be a potential candidate for bone tissue engineering applications and further development.
3
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Immobilization ofAmano Lipase Aonto Stöber silica surface: process characterization and kinetic studies

64%
Zdarta J., Sałek K., Kołodziejczak-Radzimska A., Siwińska-Stefańska K., Szwarc-Rzepka K., Norman M., Klapiszewski Ł., Bartczak P., Kaczorek E., Jesionowski T.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
The immobilization of Amano Lipase A from Aspergillus niger by adsorption onto Stöber silica matrix obtained by sol-gel method was studied. The effectiveness of the enzyme immobilization and thus the usefulness of the method was demonstrated by a number of physicochemical analysis techniques including Fourier Transform Infrared Spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TG), porous structure of the support and the products after immobilization from the enzyme solution with various concentration at different times. The analysis of the process’ kinetics allowed the determination of the sorption parameters of the support and optimization of the process. The optimum initial concentration of the enzyme solution was found to be 5 mg mL-1, while the optimum time of the immobilization was 120 minutes. These values of the variable parameters of the process were obtained by as ensuring the immobilization of the largest possible amount of the biocatalyst at
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