scholarly journals Kinetic Analysis on the Stabilization Effects of Substituted POSS Powders Embedded in γ-Radiolyzed Polypropylene

2021 ◽  
Vol 5 (5) ◽  
pp. 124
Author(s):  
Traian Zaharescu ◽  
Ignazio Blanco ◽  
Tunde Borbath ◽  
Istvan Borbath ◽  
Marius Mariș
Keyword(s):  
Kinetic Analysis ◽  
Oxidative Degradation ◽  
Kinetic Approach ◽  
Additive Concentration ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Γ Irradiation ◽  
Accelerated Degradation ◽  
Radiation Induced ◽  
Influence Of Substituents

The present paper proposes a reliable alternative for the increasing stability of polypropylene (PP) by modified polyhedral oligomeric silsesquioxanes (POSS). The chemiluminescence measurements and FTIR records point complementarily out the determinant influence of substituents on the progress of oxidation during the accelerated degradation caused by γ-irradiation. The main kinetic approach of oxidation acting in radiation-induced aging recommends some of the studied structures of modified POSS as appropriate compounds for improving stability of polypropylene at low additive concentration. The analysis of the present results is based on the implication of substituted POSS, whose contribution to the limitation of oxidation is conditioned by the influence of substituents. The delay of the oxidative degradation in studied γ-irradiated polypropylene is the consequence of the interaction between molecular PP fragments and the silanol moieties generated during radiolysis, which are the most vulnerable points of POSS structure.

scholarly journals The effect of polyhedral oligomeric silsesquioxanes (POSSs) incorporation in ethylene-propylene-diene-terpolymer (EPDM): a thermal study

2021 ◽  
Author(s):  
Ignazio Blanco ◽  
Traian Zaharescu
Keyword(s):  
Room Temperature ◽  
Thermal Characterization ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Dsc Analysis ◽  
Γ Irradiation ◽  
Scanning Calorimetry ◽  
Ethylene Propylene ◽  
Oligomeric Silsesquioxane ◽  
Ethylene Propylene Diene Terpolymer ◽  
Dynamic Heating

AbstractA series of ethylene-propylene-diene-terpolymer (EPDM)/polyhedral oligomeric silsesquioxane (POSS) composites at different percentage of POSS were prepared and subjected to γ-irradiation. Both irradiated and non-irradiated EPDM and composites were investigated by the means of thermal analysis to verify if the presence of POSS molecules is able to reduce the oxidation level of free radicals generated during the degradation and to evaluate the effects of the irradiation. EPDM composites at 1, 3 and 5 mass% of POSS were thus degraded in a thermogravimetric (TG) balance in dynamic heating conditions (25–700 °C), in both inert and oxidative atmosphere by flowing nitrogen and air respectively. Thermal characterization was then completed by carrying out Differential Scanning Calorimetry (DSC) analysis from sub-ambient to better highlight the melting of the polymer and polymer composites occurring just above the room temperature. FTIR spectroscopy was also performed for the prepared samples to check the presence of the molecular filler in the composites and for the TG’s residue at 700 °C, in order to evaluate its nature. DSC and TGA parameters were detected and discussed to have information about the effect of the degradation’s environment, the effect of irradiation on polymer stabilization and the effect of POSS content in the polymer matrix.

scholarly journals Stabilization Effects of Natural Compounds and Polyhedral Oligomeric Silsesquioxane Nanoparticles on the Accelerated Degradation of Ethylene-Propylene-Diene Monomer

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4390
Author(s):  
Traian Zaharescu ◽  
Ignazio Blanco
Keyword(s):  
Antioxidant Properties ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Natural Antioxidants ◽  
Rosemary Extract ◽  
Γ Irradiation ◽  
Ethylene Propylene ◽  
Radical Intermediates ◽  
Accelerated Degradation ◽  
Evaluation Procedures ◽  
Oligomeric Silsesquioxane

In this work the analysis on the stabilization activities of some natural antioxidants (rosemary extract, capsaicin, quercetin or oleanolic acid) is presented. A similar contribution of an inorganic structure—polyhedral oligomeric silsesquioxane (POSS) nanoparticles—is also evaluated. The stabilization effects on the oxidation protection were investigated for several formulations based on ethylene-propylene-diene-terpolymer (EPDM). The samples were examined in pristine state or after γ-irradiation, when the accelerated degradation scission of polymer macromolecules followed by the mitigation of oxidation. Three evaluation procedures: chemiluminescence, FTIR spectroscopy and thermal analysis were applied for the characterization of stability efficiency. The delaying effect of oxidative aging in EPDM matrix is illustrated by the values of activation energy, which are correlated with the type and concentration of embedded compounds. The durability of studied EPDM formulations is discussed for the assessment of material life. The improved behavior of structured hybrids useful for the optimization application regimes is essentially based on the antioxidant properties of polyphenolic components in the cases of natural antioxidants or on the penetration of free radical intermediates into the free volumes of POSS.

scholarly journals Reaction of a satirically hindered iron(III) porphyrin with peroxyacetic acid: Degradation kinetics

2005 ◽  
Vol 70 (8-9) ◽  
pp. 1105-1111 ◽  
Author(s):  
P. Prakash ◽  
Mary Francisca
Keyword(s):  
Reaction Mechanism ◽  
Spectroscopic Study ◽  
Kinetic Analysis ◽  
Peracetic Acid ◽  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
Peroxyacetic Acid ◽  
Porphyrin Ligand ◽  
Uv Visible ◽  
Reversible Formation

A kinetic analysis of the reaction between peracetic acid (AcOOH), and tetrakis (pentafluorophenyl) - 21H, 23H-porphine iron(III) chloride Fe(F20TPP)Cl, in acetonitrile showed that the peracetic acid oxidatively destroys Fe(F20TPP)Cl. This is in contrast to an assumption that the oxidative degradation of metalloporphyrins can be prevented by the introduction of electron-withdrawing substituents into the phenyl groups of the porphyrin ligand. A UV-visible spectroscopic study showed a degree of macro cycle destruction of the tetrapyrrole conjucation of the metalloporphyrin. The degradation takes place via oxoperferryl species. The first step of the reaction mechanism is the reversible formation of an adduct ?X? (k1/k-1) between Fe(F20TPP)Cl and peracetic acid, followed by an irreversible step (k2) for the formation of oxoperferryl species.

Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

2020 ◽  
Vol 105 (7) ◽  
pp. 1051-1059
Author(s):  
José R. Toledo ◽  
Raphaela de Oliveira ◽  
Lorena N. Dias ◽  
Mário L.C. Chaves ◽  
Joachim Karfunkel ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Color Centers ◽  
Hydroxyl Groups ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Radiation Induced ◽  
Induced Defects ◽  
Electron Paramagnetic ◽  
Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

Radiation Defects in Lime Mortars and Plasters Studied by EPR Spectroscopy

Radiocarbon ◽  
2020 ◽  
Vol 62 (3) ◽  
pp. 713-724
Author(s):  
Zuzanna Kabacińska ◽  
Danuta Michalska ◽  
Bernadeta Dobosz
Keyword(s):  
Epr Spectroscopy ◽  
Organic Radical ◽  
Radiation Defects ◽  
Paramagnetic Centers ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Crystalline Materials ◽  
Lime Mortars ◽  
Radiation Induced ◽  
Artificial Uv

ABSTRACTElectron paramagnetic resonance (EPR) spectroscopy is a well-established method of dating based on trapped charges, applied to various crystalline materials, including carbonates, bones, and teeth. It provides a detailed insight into the structure of radiation defects—paramagnetic centers generated by irradiation, without the need of a painstaking sample preparation, often challenging in other methods. Using EPR we studied the effect of γ radiation on lime mortars and plasters from ancient settlement Hippos in Israel, in order to analyze the process of defect generation. Analysis of the complex spectra revealed the presence of radiation-induced species, including CO2–, NO32– and organic radical. Using an artificial UV source, we generated relatively strong signals of paramagnetic centers, analogous to those created by γ irradiation, reaching their maximum intensity after 5–6 hr of UV exposure. Our results confirm the previous reports that radiation defects can also be generated, instead of bleached, in calcite by UV radiation, which is crucial for identifying the issues related to light exposition, affecting the accuracy of age determinations in trapped-charge dating methods.

Radiation-induced polymerization of ethylene in pilot plant. IV. Kinetic analysis

1980 ◽  
Vol 25 (2) ◽  
pp. 277-285 ◽  
Author(s):  
Hiromasa Watanabe ◽  
Sueo Machi ◽  
Hirondo Kurihara ◽  
Takeshi Wada ◽  
Kouichi Yamaguchi ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Pilot Plant ◽  
Radiation Induced

Studies of radiation-induced reactions of ethylene in aqueous solution II. Reactions in the presence of oxygen as studied by pulse radiolysis and γ -irradiation techniques

1967 ◽  
Vol 300 (1463) ◽  
pp. 443-454 ◽  
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
Major Product ◽  
Peroxy Radicals ◽  
Ferrous Ions ◽  
Constant Composition ◽  
Γ Irradiation ◽  
Radiation Induced

The radiolysis of dilute aqueous solutions containing ethylene and oxygen has been investigated. Pulse radiolysis was used to measure the rate constants for the addition of hydroxyl radicals to ethylene, the binary decomposition of the resulting hydroxyethyl radicals and their addition to ethylene and reaction with oxygen to yield peroxy radicals. The rate constants have also been determined for the mutual interaction of the peroxy radicals and their reaction with ferrous ions. The principal products of γ -irradiation were aldehydes and organic hydroperoxides. Hydrogen peroxide was found in yields close to the molecular yield from water. The polymer produced in the absence of oxygen was not formed, and glycollaldehyde, reported as a major product by previous workers, could not be detected. At constant composition of the gas mixtures, product yields were unaffected by total pressure in the range up to 40 atm, but were strongly dependent on the proportion of oxygen. Aldehyde yields were markedly greater at pH 1.2 than in neutral solution. The influence of ferrous ions an d of added hydrogen peroxide has been determined. The pulse radiolysis and γ -irradiation experiments complement one another and show that the radiation-induced oxidation of ethylene in aqueous solution involves the same primary reactions as occur in the absence of oxygen, followed by the formation and further reactions of peroxy radicals.

Ionizing radiation stimulates muscarinic regulation of rat intestinal mucosal function

1998 ◽  
Vol 275 (6) ◽  
pp. G1333-G1340 ◽  
Author(s):  
F. Lebrun ◽  
A. Francois ◽  
M. Vergnet ◽  
L. Lebaron-Jacobs ◽  
P. Gourmelon ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Enzyme Activities ◽  
Plasma Membranes ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Marker Enzyme ◽  
Γ Irradiation ◽  
Ussing Chambers ◽  
Radiation Induced ◽  
Total Body

The aim of this study was to determine whether ionizing radiation modifies muscarinic regulation of intestinal mucosal function. Rats exposed to total body 8-Gy γ-irradiation or sham irradiated were studied up to 21 days after irradiation. Basal and carbachol-stimulated short-circuit current ( I sc) and transepithelial conductance ( G t) of stripped ileum were determined in Ussing chambers. Muscarinic receptor characteristics using the muscarinic antagonist [3H]quinuclidinyl benzilate and three unlabeled antagonists were measured in small intestinal plasma membranes together with two marker enzyme activities (sucrase, Na+-K+-ATPase). Enzyme activities were decreased 4 days after irradiation ( day 4). Basal electrical parameters were unchanged. Maximal carbachol-induced changes in I sc and G t were increased at day 4 (maximal Δ I sc = 195.8 ± 14.7 μA/cm2, n = 19, vs. 115.4 ± 8.2 μA/cm2, n = 63, for control rats) and unchanged at day 7. Dissociation constant was decreased at day 4 (0.73 ± 0.29 nM, n = 10, vs. 2.14 ± 0.39 nM, n = 13, for control rats) but unchanged at day 7, without change in binding site number. Thus total body irradiation induces a temporary stimulation of cholinergic regulation of mucosal intestinal function that may result in radiation-induced diarrhea.

Influence of polypropylene and nanoclay on thermal and thermo-oxidative degradation of poly(lactide acid): TG-FTIR, TG-DSC studies and kinetic analysis

2020 ◽  
Vol 691 ◽  
pp. 178709
Author(s):  
Navid Karimpour-Motlagh ◽  
Hossein Ali Khonakdar ◽  
Seyed Mohammad Ali Jafari ◽  
Alireza Mahjub ◽  
Mahyar Panahi-Sarmad ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Oxidative Degradation ◽  
Dsc Studies ◽  
Thermo Oxidative Degradation
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