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    Wyświetlanie 1-7 z 7
    Tytuł:
    Characteristics of physicochemical and rheological properties of chitosan hydrogels based on selected hydroxy acids
    Autorzy:
    Zavyalova, Olga
    Gajewska, Sandra
    Dąbrowska-Wisłocka, Dominika
    Sionkowska, Alina
    Powiązania:
    https://bibliotekanauki.pl/articles/2058389.pdf
    Data publikacji:
    2021
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    chitosan
    lactobionic acid
    mandelic acid
    rheology
    FTIR spectra
    chitozan
    reologia
    hydrożele
    Opis:
    Chitosan is a natural cationic polymer that dissolves in an acidic environment and forms gels. Its properties depend on the degree of deacetylation and molecular weight. It is a bioactive compound with antibacterial and film-forming properties that allow to increase the regenerative capacity of the skin. Moreover, it is biodegradable, biocompatible, non-toxic, and stable. In this research, chitosan was combined with mandelic and lactobionic acids which are characterized by biological activity and low toxicity. This combination not only has a positive effect on the chitosan solubility, but it also allows to obtain new biomaterials whose positive features of the base ingredients are enhanced by their synergistic effect. The obtained hydrogels were assessed regarding the interaction of chitosan and hydroxy acid molecules, and the stability of the resulting structures was examined. The research was performed by using rheological methods and IR spectroscopy. Chitosan hydrogels made with mandelic acid are characterized by higher viscosity values, as compared to hydrogels containing lactobionic acid. The samples of the obtained hydrogels stored for 7 days showed no signs of degradation and their viscosity values were constantly increasing, which proves the ongoing process of creating new bonds between hydroxy acid molecules and chitosan chains. After this time, the hydrogels with mandelic acid revealed higher viscosity values in comparison to hydrogels made with lactobionic acid. Based on the obtained IR spectra, the shifts of the characteristic chitosan bands as a result of interaction with the tested hydroxy acids were analyzed.
    Źródło:
    Engineering of Biomaterials; 2021, 24, 161; 2--7
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Infrared spectral analysis of waste pet samples
    Autorzy:
    Vijayakumar, S.
    Rajakumar, P. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/411833.pdf
    Data publikacji:
    2012
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    butelki PET
    ABS
    FTIR
    mieszanki kompozytowe
    PET bottles
    FT-IR spectra
    blended composites
    Opis:
    There are fifteen waste pet bottles and a commercial grade ABS was collected from local supplier of Chidambaram town. The ABS was used to study the mechanical properties of PET blend composites. This study was performed by FT-IR spectroscopy. From the characteristics infra-red stretching bands the mechanical properties of samples were discussed.
    Źródło:
    International Letters of Chemistry, Physics and Astronomy; 2012, 4; 58-65
    2299-3843
    Pojawia się w:
    International Letters of Chemistry, Physics and Astronomy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Równowagi asocjacyjne alkilopochodnych mocznika i tiomocznika
    Association equilibria of alkyl derivatives of urea and thiourea
    Autorzy:
    Rospenk, M.
    Koll, A.
    Obrzud, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172815.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    model samoasocjacji
    momenty dipolowe
    średnia masa cząsteczkowa
    obliczenia DFT
    pochodne mocznika i tiomocznika
    model of self-association
    dipole moments
    average molecular weight
    FTIR spectra
    DFT calculation
    derivatives of urea and thiourea
    Opis:
    The studies and comparison of a series of molecular mono- and di-substituted derivatives of urea and thiourea in solvents of increasing polarity are presented [1–4]. These substances are characterized by a high tendency to self-associate through the formation of intermolecular hydrogen bonds due to the presence in their structure both groups as donors (NH) as well as proton acceptors (C=O) or (C=S). Studies were performed by using IR spectroscopy, method of measuring the average molecular weight and the dipole moments. The experimental data were verified by DFT quantum chemical calculations with B3PW91 correlation functional. Simultaneous use of these techniques alowed establishing not only the efficiency of aggregation, but also the structure and polarity of formed aggregates. It was shown, that in solvents with weak acidic C-H groups the aggregation was strongly limited because of molecular interactions between solute and solvent. The theoretical DFT calculations which included the impact of the environment on the nature of interactions in the complex were carried out [e.g. Scheme 4.1.4]. A combination of geometry optimization in polarizable continuum model (PCM) with the connection of chloroform molecules (1,2-dichloroethane) with urea dimers enabled to obtain the expected theoretical simulation compliance with the experiment. The equilibrium constants were calculated on the basis of data obtained in two independent methods of measurement: IR spectroscopy and measurements of average molecular weights. Good agreement of experimental data of both research techniques were found up to concentration of 0.03 mol/dm3 [Fig. 2.5]. The type of associates have been assessed following the dipole moments measured as a function of concentration, and on the results of density-functional theory (DFT) calculations on the structure and energy of particular species. All of the urea derivatives demonstrated an increase in dipole moment with increased concentration, suggesting linear-type aggregation [Fig. 4.1.3]. Contrastingly, the dipole moments of the N,N-dimethylthiourea and mono-N-alkyl-substituted thioureas decreased with concentration and suggest that cyclic dimers or trimers are formed by C=S…(HR)2N-C=S interactions [Fig. 4.2.2]. The efficiency of self-aggregation was described by use of two equilibrium constants. The first constant, K1, was describing dimer formation and the second constant, K2, the subsequent multimer formation. In N,N’-thioureas aggregation was lower than for the related urea compounds [Table 4.1.1 and Table 4.2.1]. Differences between urea and thiourea derivatives result from the fact that the ureas are stronger bases and, therefore, more active in aggregation.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 7-8; 559-608
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Przemiany struktury smarów plastycznych po testach tribologicznych
    Conversion of the structure of greases after tribological tests
    Autorzy:
    Pawelec, E.
    Siwiec, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/188552.pdf
    Data publikacji:
    2013
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    smar plastyczny
    właściwości przeciwzużyciowe
    widmo IR
    spektrofotometria w podczerwieni
    dodatki smarne
    grease
    antiwear properties
    IR spectra
    FTIR spectrophotometry
    lubricating additives
    Opis:
    W artykule przedstawiono wyniki badania składu smarów plastycznych po testach tribologicznych prowadzonych w warunkach stałego obciążenia węzła tarcia. W tym celu wykonano widma IR smaru wyjściowego i porównano je z widmami uzyskanymi dla smarów po testach tribologicznych. Zidentyfikowano pasma charakterystyczne dla badanych smarów i oceniono zmiany w tych zakresach. Uzyskane wyniki wykazały, że właściwości przeciwzużyciowe badanych smarów nie są jedynie funkcją ilościowego udziału dodatków, ale także produktów oksydacji, jakim ulegają składniki smaru.
    This paper presents the results of grease composition analysis when tribological tests are performed under constant load. The analysis was conducted by comparing the IR spectra of grease before and after tribological tests. The changes in the identified spectra characteristic of the greases were used to evaluate changes in the grease structures. The results showed that the anti-wear properties of lubricants tested are both a function of the quantitative contribution of additives and the oxidation products that are components of the grease.
    Źródło:
    Tribologia; 2013, 2; 141-150
    0208-7774
    Pojawia się w:
    Tribologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electromagnetic field of extremely low frequency has an impact on selected chemical components of the honeybee
    Autorzy:
    Koziorowska, A.
    Depciuch, J.
    Białek, J.
    Woś, I.
    Kozioł, K.
    Sadło, S.
    Piechowicz, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2087262.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Apis mellifera
    ELF-EMF
    FTIR
    spectra analysis
    body chemical composition
    Źródło:
    Polish Journal of Veterinary Sciences; 2020, 23, 4; 537-544
    1505-1773
    Pojawia się w:
    Polish Journal of Veterinary Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The impact of heat treatment on the components of plant biomass as exemplified by Junniperus sabina and Picea abies
    Autorzy:
    Drygaś, B.
    Depciuch, J.
    Puchalski, Cz.
    Zaguła, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/411289.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Oddział w Lublinie PAN
    Tematy:
    torrefaction
    biomass
    FTIR spectra
    changes
    biochars
    Opis:
    Torrefaction is the process of drying biomass at high temperatures in order to transform it into biofuels with properties and composition resembling carbon. The impact of high temperature breaks the chains of hemicellulose, lignin and cellulose and degrades the biomass to simpler organic compounds. The aim of this publication was to specify the impact of the duration of the heat treatment on the stability of biomass structures such as lignocellulose illustrated with examples of selected species of conifers. The research material consisted of shoot tips of Junniperus sabina and Picea abies. The material used in the process was air-dried, dried at 150oC and torrefied at temperatures of 200, 250 and 300oC in a LECO camera – TGA 701 apparatus for 30 minutes. Fresh needles and their torrefied products were measured spectroscopically using FTIR Vertex 70v made by Bruker. Microscopic photographs of samples were taken in the scales 10 μm, 20 μm, and 50 μm using the TESCAN VEGA3 scanning electron microscope. The unprocessed plant material did not differ significantly from one another – the FTIR spectra of both plants exhibited the same functional groups. The biomass heat treatment led to significant changes in its chemical composition and topographic changes in the obtained biochars.
    Źródło:
    ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes; 2016, 5, 3; 41-50
    2084-5715
    Pojawia się w:
    ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Properties of Soda-Lime-Silica Glasses Doped with Eggshell Powder
    Autorzy:
    Aktas, B.
    Albaskara, M.
    Yalcin, S.
    Dogru, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030117.pdf
    Data publikacji:
    2017-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    soda-lime-silica glass
    eggshell powder
    optical properties
    FTIR spectra
    Opis:
    The optical properties of soda-lime-silica glasses doped with eggshell powder were investigated using UV-visible and the Fourier transform infrared spectroscopies. Pure soda-lime-silica glass, which is colorless and transparent, turned dark green after the addition of the eggshell powder. When the eggshell powder content was ≥ 3 wt%, the glass became translucent. The maximum wavelengths in the UV spectra of the soda-lime-silica glasses doped with 0.5, 1, 3, and 5 wt% eggshell powder were observed at 300.20, 277.40, 284.40, and 312.40 nm, respectively. The Fourier transform infrared spectra of the eggshell-doped soda-lime-silica glass samples were very similar to that of the base undoped glass. The bands at approximately 770-820 cm¯¹ could be attributed to the Si-O-Si symmetric stretching of the bridging oxygen between the tetrahedra, while the bands at approximately 970 cm¯¹ were related to the Si-O-Si antisymmetric stretching of the bridging oxygen within the tetrahedra.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 3; 442-444
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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