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1.
N. I. Egorenkov D. G. Lin V. A. Belyi 《Journal of Thermal Analysis and Calorimetry》1976,10(3):357-362
Differential thermal analysis (DTA) and infrared (IR) spectroscopy have been used to investigate the effects of an antioxidant (neozone D) and an oxidation catalyst (dispersed copper) on polyethylene melt oxidation under nonisothermal conditions (samples were heated at a constant rate). An increase in the content of the antioxidant or the oxidation catalyst gives similar results: a decrease in the thickness of the oxidized surface layer and accordingly in the total amount of oxidation in polyethylene samples. This is due to an increase in the rate of oxidation of the polymer. 相似文献
2.
The present study is to examine the photo‐stabilization effect of an antioxidant on the photo‐oxidation of ethylene‐propylene‐diene monomer (EPDM)–clay nanocomposites. During the preparation of EPDM–clay nanocomposites via melt processing antioxidants are usually incorporated along with clay, which allows phenolic antioxidant molecules to get adsorbed onto acidic clay platelets and their interaction with metallic impurities reduces the stabilizing efficiency of the antioxidant. The nanocomposites were obtained by solution dispersion followed by melt compounding of EPDM and organophilic montmorillonite (OMMT). The samples were characterized by conventional tools such as X‐ray diffraction (XRD), Fourier Transform Infra Red (FT‐IR) spectroscopy, and thermo‐gravimetric analysis (TGA). It was found, upon photo‐irradiation (λ > 290 nm) studies by following the changes in functional groups and surface morphology, that photo‐degradation was lowered by the antioxidant and the efficiency of the antioxidant could be improved by initial incorporation of antioxidant in the EPDM matrix. In EPDM–clay nanocomposites, a stabilizing activity of the antioxidant was observed above some threshold concentration of the antioxidant. The relationship between the nanoclay reinforcement and stabilizing efficiency in terms of photo‐oxidation and surface morphology for their applicability are discussed. The methodology adopted for this study is also justified through our observation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
Yu. Bolbukh P. Kuzema V. Tertykh I. Laguta 《Journal of Thermal Analysis and Calorimetry》2008,94(3):727-736
High-density polyethylene, its composites with hydrophilic/hydrophobic silica and the antioxidant BHT (butylated hydroxytoluene)
were studied using the thermogravimetric analysis. It has been shown that filling with silica as well as introducing BHT into
the unfilled polymer increases the thermal-oxidative stability of the polymer. Immobilized BHT is inactive and it suppresses
the stabilizing effect of hydrophobic silica surface in the processes of thermal oxidation at the initial stage. However,
being gradually released from the surface antioxidant prolongs the resistance of the polymer against oxidation. 相似文献
4.
Metal–Organic Framework‐Derived Copper Nanoparticle@Carbon Nanocomposites as Peroxidase Mimics for Colorimetric Sensing of Ascorbic Acid 下载免费PDF全文
Dr. Hongliang Tan Chanjiao Ma Li Gao Qian Li Prof. Yonghai Song Dr. Fugang Xu Prof. Tao Wang Prof. Li Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16377-16383
Metal–organic frameworks (MOFs) have emerged as very fascinating functional materials due to their diversity nature. A nanocomposite consisting of copper nanoparticles dispersed within a carbon matrix (Cu NPs@C) is prepared through a one‐pot thermolysis of copper‐based metal–organic framework precursors. Cu NPs@C can catalyze the oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) to form a colored product in the presence of H2O2. As a peroxidase mimic, Cu NPs@C not only has the advantages of low cost, high stability, and easy preparation, but also follows Michaelis–Menten behaviors and shows strong affinity to H2O2. As the Cu NPs’ surfaces are free from stabilizing agent, Cu NPs@C exhibited a higher affinity to H2O2 than horseradish peroxidase. On the basis of the inhibitory effect of ascorbic acid (AA) on oxidation of TMB, this system serves as a colorimetric method for the detection of AA, suggesting that the present work would expand the potential applications of MOF‐derived nanocomposites in biomedical fields. 相似文献
5.
C Zhang F Liu Y Zhai H Ariga N Yi Y Liu K Asakura M Flytzani-Stephanopoulos H He 《Angewandte Chemie (International ed. in English)》2012,51(38):9628-9632
Addition of alkali metal ions significantly promotes the activity of the Pt/TiO(2) catalyst for the HCHO oxidation reaction by stabilizing an atomically dispersed Pt-O(OH)(x) alkali metal species and opening a new low-temperature reaction pathway. The atomically dispersed Na-Pt-O(OH)(x) species can effectively activate H(2) O and catalyze the facile reaction between surface OH and formate species to total oxidation products. 相似文献
6.
The performance of Irganox 1010 phenolic antioxidant was studied in relation to the procedure of its introduction into a stock of the polymer and dispersed filler powders. Three procedures were used for introducing the antioxidant: the antioxidant was deposited onto the surface of filler (procedure I) or polymer powder (procedure II) particles prior to mixing the components, or it was deposited after mixing the polymer and filler powders (procedure III). We studied mixtures with an inert filler (aluminum oxide) and with fillers active in polymer oxidation and regeneration of the phenolic antioxidant (dispersed zinc, zinc oxide). The film samples for the studies were prepared from powder stocks by hot pressing. The antioxidant performance was evaluated by the induction period of oxidation, which was determined from the time dependences of accumulation of carbonyl groups in the polymer structure. 相似文献
7.
Polytriazolylamines were synthesized by the copper(I)-catalyzed ligation of azides and alkynes. The C3-symmetric derivative, TBTA, was shown to be a powerful stabilizing ligand for copper(I), protecting it from oxidation and disproportionation, while enhancing its catalytic activity. 相似文献
8.
Viktor A. Timoshnikov Lilia A. Kichigina Olga Yu. Selyutina Nikolay E. Polyakov George J. Kontoghiorghes 《Molecules (Basel, Switzerland)》2021,26(16)
Deferasirox is an orally active, lipophilic iron chelating drug used on thousands of patients worldwide for the treatment of transfusional iron overload. The essential transition metals iron and copper are the primary catalysts of reactive oxygen species and oxidative damage in biological systems. The redox effects of deferasirox and its metal complexes with iron, copper and other metals are of pharmacological, toxicological, biological and physiological importance. Several molecular model systems of oxidative damage caused by iron and copper catalysis including the oxidation of ascorbic acid, the peroxidation of linoleic acid micelles and the oxidation of dihydropyridine have been investigated in the presence of deferasirox using UV-visible and NMR spectroscopy. Deferasirox has shown antioxidant activity in all three model systems, causing substantial reduction in the rate of oxidation and oxidative damage. Deferasirox showed the greatest antioxidant activity in the oxidation of ascorbic acid with the participation of iron ions and reduced the reaction rate by about a 100 times. Overall, deferasirox appears to have lower affinity for copper in comparison to iron. Comparative studies of the antioxidant activity of deferasirox and the hydrophilic oral iron chelating drug deferiprone in the peroxidation of linoleic acid micelles showed lower efficiency of deferasirox in comparison to deferiprone. 相似文献
9.
The oxidation resistance of polyethylene films in which the antioxidant is concentrated exclusively in the surface layer of
the polymer or in the layer contacting with the support was studied. Specific features of oxidation of polyethylene films
with heterogeneous distribution of an amine (Neozon D) or phenolic (Irganoks 1010) antioxidant on a catalytically active copper
support were examined in relation to the kind of the antioxidant. 相似文献
10.
《Arabian Journal of Chemistry》2023,16(1):104442
This study reports the electrochemical synthesis, antimicrobial and catalytic activity of copper-arabinoxylan nanocomposite. The synthesis was achieved without use of any hazardous reducing and stabilizing agent. The spherical copper nanoparticles (size approx. 40 nm) dispersed in the arabinoxylan matrix as they formed and got stabilized. In the absence of arabinoxylan the particles rapidly converted to copper oxide suggesting a high stability for the composite. Electrolysis was carried out with copper plate as the sacrificial anode, carbon rod as the cathode and sodium nitrate (1.00 % in 1 % arabinoxylan suspension) as an electrolyte. The copper nanoparticles dispersed in arabinoxylan were characterized by surface plasmon resonance spectroscopy, X-ray diffraction, electron microscopy and zeta potential measurements. The synthesized composite exhibited good antimicrobial activity against P. aeruginosa, Staph. aureus and E. coli and a catalytic activity in conversion of CO2 to methanol. 相似文献
11.
Klimov E. S. Davydova O. A. Buzaeva M. V. Dubrovina V. V. Kalyukova E. N. 《Russian Journal of Applied Chemistry》2010,83(9):1657-1659
Direct oxidation of copper in organic media with complexones (sterically hindered o-quinones; acetylacetone and pyridine as stabilizing ligands) was studied. From the complexes obtained, the initial components
can be regenerated. 相似文献
12.
M. Yu. Chaika T. A. Kravchenko L. N. Polyanskii V. A. Krysanov 《Russian Journal of Electrochemistry》2008,44(11):1244-1250
Electrochemical reduction of molecular oxygen was studied on a [dispersed copper]-[macroporous KU-23 15/100S sulfocation exchanger with various metal concentrations] composite electrode. It was found that a high proton concentration in the ion-exchange matrix causes a decrease in the oxygen reaction overvoltage. The nanostructured state of copper particles causes stabilization of the intermediate product, i.e., hydrogen peroxide. Using the rotating disk electrode method, it was detected that the process is limited by external diffusion of oxygen to composite grains. The oxygen reaction is mostly concentrated on the grain surface and surface layers; oxygen is reduced in the bulk due to dispersed copper oxidation. 相似文献
13.
Zhao H Yang J Wang L Tian C Jiang B Fu H 《Chemical communications (Cambridge, England)》2011,47(7):2014-2016
Small and highly dispersed palladium nanoparticles supported on graphene nanosheets were fabricated via a strategy of etching a copper template with Pd(2+). The obtained hybrid exhibited significant catalytic activity for formic acid oxidation. 相似文献
14.
WANG Ye AN DongLi & ZHANG QingHong State Key Laboratory of Physical Chemistry of Solid Surfaces National Engineering Laboratory for Green Chemical Productions of Alcohols Ethers Esters 《中国科学:化学》2010,(2)
Selective oxidation or oxidative functionalization of methane and ethane by both homogeneous and heterogeneous catalysis is presented concerning: (1) selective oxidation of methane and ethane to organic oxygenates by hydrogen peroxide in a water medium in the presence of homogeneous osmium catalysts, (2) selective oxidation of methane to formaldehyde over highly dispersed iron and copper heterogeneous catalysts, (3) selective oxidation of ethane to acetaldehyde and formaldehyde over supported molybdenum cat... 相似文献
15.
D. G. Lin E. V. Vorob'eva N. V. Marchenko 《Russian Journal of Applied Chemistry》2005,78(9):1503-1507
Thermal oxidation of polyethylene containing amine and phenolic antioxidants during contact with copper (metal support, powder) and the trends in variation of the antioxidant performance were studied. 相似文献
16.
E. V. Shinkareva V. D. Koshevar O. A. Plikus 《Russian Journal of Applied Chemistry》2012,85(8):1282-1288
The effect exerted by adsorption of nonionic surfactants on the stabilizing ability of latexes in preparation of epoxy emulsions and on the structural-rheological properties of these emulsions was examined. The stabilizing effect was attributed to heterostabilization of particles of the mixed dispersed phase and to the strength of the structural framework formed. 相似文献
17.
D. I. Potemkin P. V. Snytnikov V. P. Pakharukova G. L. Semin E. M. Moroz V. A. Sobyanin 《Kinetics and Catalysis》2010,51(1):119-125
A series of copper-cerium oxide catalysts was prepared by the Pechini method, and their physicochemical and catalytic properties
in CO oxidation in hydrogen-containing gas mixtures were studied. The method chosen for catalyst preparation yields finely
dispersed copper and cerium oxides in the catalyst. 相似文献
18.
Martínez-Arias A Hungría AB Fernández-García M Iglesias-Juez A Soria J Conesa JC Anderson JA Munuera G 《Physical chemistry chemical physics : PCCP》2012,14(7):2144-2151
Catalysts of 1 wt% copper oxide supported on cerium oxide or cerium-terbium mixed oxides are comparatively examined with respect to their redox and catalytic properties for CO oxidation. Characterization of the catalysts had shown that they contain highly dispersed CuO-type entities on the corresponding nanostructured fluorite supports with copper dispersion increasing with increasing amounts of terbium in the support. In contrast, the CO oxidation catalytic activity decreases with increasing amounts of terbium in the support. On the basis of operando-DRIFTS experiments, one of the factors that could explain such behaviour is related to the greater difficulty in generating reduced copper sites active for the reaction in the presence of terbium, which in turn is evidenced to constitute an induction stage. Analysis of the redox properties is complemented by XPS which confirms the greater resistance to copper reduction in the presence of terbium. 相似文献
19.
D. Das D. Das T. K. Kundu M. K. Dey S. Chakraborty D. Chakravorty 《Journal of Chemical Sciences》2003,115(5-6):341-348
Composites of nanometre-sized copper core-copper oxide shell with diameters in the range 6.1 to 7.3 nm dispersed in a silica
gel were synthesised by a technique comprising reduction followed by oxidation of a suitably chosen precursor gel. The hot
pressed gel powders mixed with nanometre-sized copper particles dispersed in silica gel showed electrical resistivities several
orders of magnitude lower than that of the precursor gel. Electrical resistivities of the different specimens were measured
over the temperature range 30 to 300°C. Activation energies for the coreshell nanostructured composites were found to be a
fraction of that of the precursor gel. Such dramatic changes are ascribed to the presence of an interfacial amorphous phase.
The resistivity variation as a function of temperature was analysed on the basis of Mott’s small polaron hopping conduction
model. The effective dielectric constant of the interfacial phase as extracted from the data analysis was found to be much
higher than that of the precursor glass. This has been explained as arising from the generation of very high pressure at the
interface due to the oxidation step to which the copper nanoparticles are subjected.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
20.
Robab Abbasi Khalil Farhadi Sepideh Banisaeid Nader Nowroozi Pesyan Arezu Jamali Fatemeh Rahmani 《催化学报》2014,35(7):1098-1104
A polytyramine-copper oxalate nanocomposite modified copper(PTCOxNMC) electrode prepared by electropolymerization was examined for electrocatalytic activity towards the oxidation of methanol in alkaline solution using cyclic voltammetry and impedance spectroscopy. The prepared PTCOxNMC electrode showed a significantly high response for adsorbed methanol oxidation. The effects of various parameters such as potential scan rate and methanol concentration on the electrocatalytic oxidation at the surface of the PTCOxNMC electrode were investigated. Spectrometry techniques such as Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine the surface physical characteristics of the modified electrode and revealed that the polytyramine-copper oxalate nanocomposite particles were highly dispersed on the surface of the copper electrode with a narrow size up to 40 nm. The very high current density obtained for the catalytic oxidation may have resulted from the high electrode surface area caused by modification with the poly-tyramine-copper oxalate nanocomposite. 相似文献