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    Tytuł:
    The kinetic degradation of LDPE films subjected to aggressive environments
    Kinetyczna degradacja folii LDPE poddanych działaniu agresywnych środowisk
    Autorzy:
    Kashi, Imad
    Zeghouan, Ouahida
    Moussaceb, Karim
    Powiązania:
    https://bibliotekanauki.pl/articles/2200482.pdf
    Data publikacji:
    2022
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
    Tematy:
    low-density polyethylene
    modeling
    kinetic degradation
    half-life time
    thermo-oxidative
    polietylen małej gęstości
    modelowanie
    kinetyczna degradacja
    okres półtrwania
    termoutlenianie
    Opis:
    The effect of natural and thermo-oxidative aging on the structure and physicochemical properties of LDPE films stabilized with hindered amine light stabilizers (HALS) was investigated. Based on multiple linear regression analysis (MLRA) mathematical models to predict the lifetime of the LDPE were developed. Four statistical criteria were used to evaluate the developed models: residual variance, coefficient of determination, Student’s test and the Fisher-Snedecor test. The half-life times predicted by the mathematical models were found to be statistically significant (p < 0.05).
    Zbadano wpływ starzenia w warunkach naturalnych i starzenia termooksydacyjnego na strukturę i właściwości fizykochemiczne folii LDPE stabilizowanych aminowymi fotostabilizatorami z zawadą przestrzenną (HALS). W oparciu o wielokrotną analizę regresji liniowej (MLRA) opracowano modele matematyczne do przewidywania czasu życia folii LDPE. Do oceny opracowanych modeli stosowano cztery kryteria statystyczne: wariancję szczątkową, współczynnik determinacji, test Studenta i test Fishera-Snedecora. Stwierdzono, że okresy półtrwania przewidywane przez modele matematyczne są istotne statystycznie (p < 0,05).
    Źródło:
    Polimery; 2022, 67, 6; 250--255
    0032-2725
    Pojawia się w:
    Polimery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metody określania struktury polisacharydów
    Methods for determining polysaccharides structure
    Autorzy:
    Samaszko-Fiertek, J.
    Kuźma, M.
    Dmochowska, B.
    Ślusarz, R.
    Madaj, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172410.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    polisacharydy
    monosacharydy
    degradacja oksydacyjna
    analiza metylacyjna
    acetoliza
    NMR
    magnetyczny rezonans jądrowy
    MS
    polysaccharides
    monosaccharides
    oxidative degradation
    methylation analysis
    acetolysis
    nuclear magnetic resonance (NMR)
    Opis:
    Sequencing of polysaccharides is difficult to achieve because of the heterogeneous nature of the polysaccharide structure, high molecular weight (the size of a polysaccharide varies between approximately 16,000 and 16,000,000 daltons (Da)), and polydispersity of the polymer chains. The following information is essential to determine the primary structure of a polysaccharide: • monosaccharide composition: nature and molar ratios of the monosaccharide building blocks; • relative configuration of monosaccharides: d or l; • anomeric configuration: α- or β-configuration of the glycosidic linkage; • ring size: presence and distinction of furanosidic and pyranosidic rings; • linkage patterns: linkage positions between the monosugars and branches; • sequences of monosaccharide residues in the repeating units; • substitutions: position and nature of OH–modifications, such as O–phosphorylation, acetylation, O-sulfation, etc.; • molecular weight and molecular weight distribution. A polysaccharide extracted from plant materials or food products is usually purified before being subjected to structural analysis. The first step of characterizing a polysaccharide is the determination of its purity, which is reflected by its chemical composition, including total sugar content, level of uronic acids, proteins, ash, and moisture of the preparation. The second step is the determination of monosaccharide composition, which will unveil structural information such as the number of monosaccharides present in the polysaccharide and how many of each sugar unit. NMR spectroscopy has become the most powerful and noninvasive physicochemical technique for determining polysaccharide structures. It can provide detailed structural information of carbohydrates, including identification of monosaccharide composition, elucidation of α- or β-anomeric configurations, establishment of linkage patterns, and sequences of the sugar units in oligosaccharides and/or polysaccharides. Monosaccharide composition can be determined also by analysis of totally acid hydrolyzed polysacharide using high performance liquid chromatography (HPLC) or gas chromatography (GC). The ring size and glycosidic linkage positions of sugar units in a polysaccharide could be established by methylation analysis and/or cleavage reduction. The anomeric configuration is conventionally determined by oxidation, and this method can be combined with mass spectrometry to obtain more structural information.
    Źródło:
    Wiadomości Chemiczne; 2016, 70, 5-6; 299-318
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of the strength properties of materials intended for tracheobronchial tubes
    Autorzy:
    Sobota, Robert
    Markowski, Jarosław
    Joszko, Kamil
    Gzik-Zroska, Bożena
    Kawlewska, Edyta
    Gzik, Marek
    Powiązania:
    https://bibliotekanauki.pl/articles/1844981.pdf
    Data publikacji:
    2020
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    thermoplastic elastomer
    tracheobronchial tubes
    oxidative degradation
    hydrolytic degradation
    Opis:
    The desire to increase the comfort of patients and to continue production despite the decreasing amount of available materials on the market has led to the constant search for novel materials that could be used to obtain tracheobronchial tubes. The aim of this study is to determine the mechanical properties of a new thermoplastic elastomer. Two materials - the thermoplastic elastomer and the natural rubber were subjected to three tests: static tensile test, static compression test and static three-point bending test. During the static tensile test, samples of the tested materials were examined, and during the next two examinations, the final products. The materials underwent the processes of sterilization, hydrolytic degradation and degradation by oxidation. The treated samples were also tested in order to compare the obtained results. The mechanical properties of the tested materials improved both after the hydrolytic degradation and oxidative degradation, as well as after the sterilization process. Yet the thermoplastic elastomer revealed a more noticeable increase. The elastomer hardening is a positive phenomenon potentially leading to fewer accidental closures of the tubes cross-section. Both the sterilization process and various degradation methods improved the mechanical properties by strengthening the tested materials. This phenomenon seems to be desirable to avoid the closure of the implemented tube during its application.
    Źródło:
    Engineering of Biomaterials; 2020, 23, 156; 10-16
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Degradation of p-aminophenol by Fenton’s process. Influence of operational parameters
    Autorzy:
    Ghosh, P.
    Ghime, D.
    Lunia, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/206932.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    environmental pollutants
    oxidative degradation
    iron compounds
    Fenton process
    zanieczyszczenia środowiskowe
    degradacja oksydacyjna
    związki żelaza
    proces Fentona
    Opis:
    Oxidative degradation of a model environmental pollutant, p-Aminophenol (PAP), in aqueous solution has been investigated in an environmentally friendly advanced oxidation Fenton process. Effects of various operating parameters such as pH of solutions, dosage of hydrogen peroxide and ferrous ions, initial PAP concentration and temperature on the degradation of PAP have been studied using a batch stirred ceil. Degradation kinetics for this pollutant was also investigated to determine the apparent rate constants (min-1)- The optimum conditions for the degradation of PAP solution (200-500 mg/dm3) were found to be pH = 3.0, 2400 mg H2O2dm, 300 mg Fe2+/dm3, 30°C. Under the optimum conditions, the degradation efficiency of PAP was 75% after 50 min of reaction. It was observed that process parameters play a major role in the overall degradation process.
    Źródło:
    Environment Protection Engineering; 2017, 43, 3; 255-267
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of Nano-Copper – Substituted Lead Zirconate as Surface Catalyst for Oxidative Degradation of Organic Dye
    Autorzy:
    Elsabawy, Khaled M.
    Bediwya, Marwa M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1193007.pdf
    Data publikacji:
    2016
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Cu-doped-PLZ
    Fuchsine dye
    Kinetics
    SE-microscopy
    X-ray Diffraction
    oxidative Degradation
    Opis:
    The oxidative decomposition reactions of fuchsine dye on the surface of nano-catalyst Cu0.5Pb0.5ZrO3 were studied carefully in an aqueous solution in the presence of H2O2 under condition of pseudo-first order reaction. The catalyst was prepared by solid state route using pure nominal composition of metal oxides. The structural and micro-structural properties of the catalyst were characterized well by XRD, SEM and AFM respectively. Many of the kinetic parameters were investigated in this article, results obtained indicated that, the rate of oxidative degradation of acid fuchsine dye was found to be pH-dependent. The mechanism was proposed and the activation parameters were calculated.
    Źródło:
    World Scientific News; 2016, 31; 111-124
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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