The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Franco Cataldo - One of the best experts on this subject based on the ideXlab platform.
-
On the Ozone degradation of polypyrrole
Polymer Degradation and Stability, 2020Co-Authors: Franco Cataldo, Mária OmastováAbstract:Abstract Polypyrrole, a conducting polymer, has been treated with Ozone in a fixed bed reactor. Two different samples of polypyrrole (PPy) have been studied. PPy-Cl prepared by chemical oxidation of pyrrole with FeCl 3 and PPy-Cl-DBSNa prepared using the same oxidant and an anionic surfactant sodium dodecylbenzenesulfonate (DBSNa). It has been shown by weight increase as function of time, by FT-IR spectroscopy of the samples, and by electronic spectroscopy that the sample PPy-Cl is one order of magnitude more stable toward Ozone Attack in comparison to the sample PPy-Cl-DBSNa containing the surfactant. The reactivity of polypyrrole with Ozone is easily detectable by different techniques. The ozonized polypyrrole samples show a significantly worse thermal stability as measured by TGA-DTA in comparison with the pristine samples demonstrating the profound degradation caused by the exposure to O 3 . PPy-Cl has been ozonized also in liquid phase in suspension or solution/suspension in different solvents. The electronic spectroscopy showed that the early stages of the ozonation reaction involve the interaction of Ozone with the bipolaron and polaron defects of polypyrrole.
-
protection mechanism of rubbers from Ozone Attack
Ozone-science & Engineering, 2019Co-Authors: Franco CataldoAbstract:ABSTRACTOzone is a pollutant at the ground level derived from the anthropogenic activities such as combustion and volatile organic compounds release in the environment. The Ozone concentration at t...
-
Surface Reaction of Ozone at High Concentration with Isotactic And Syndiotactic Polypropylene
Journal of Macromolecular Science Part A, 2011Co-Authors: Franco Cataldo, Laura Lilla, Ornella UrsiniAbstract:The surface reaction of isotactic and syndiotactic polypropylene (I-PP and S-PP) films with Ozone was studied with FT-IR spectroscopy with differential scanning calorimetry (DSC) and making use of 2,2,4-trimethylpentane as a model compound of PP chain segment. I-PP and S-PP were found reactive toward Ozone, and it was found that I-PP being more crystalline than S-PP, reacts more slowly with O3. In fact, the pseudo first rate constant of I-PP with Ozone was k’I-PP = 8.0 × 10−6 s−1 while that of S-PP with Ozone k’S-PP = 1.3 × 10−5 s−1. However, the DSC study has shown that the Ozone Attack on I-PP or S-PP films is not selective and simultaneously destroys the amorphous and the crystalline phases. The Ozone treated I-PP and S-PP films are much less resistant to the combined thermal and oxidative degradation reaction than the unexposed films. Thus, Ozone is a naturally occurring pollutant at the soil level which accelerates the ageing of I-PP and S-PP materials.
-
Ozone Degradation of Biological Macromolecules: Proteins, Hemoglobin, RNA, and DNA
Ozone-science & Engineering, 2006Co-Authors: Franco CataldoAbstract:The reactions of Ozone with a series of biological macromolecules are reviewed. With proteins, Ozone causes the oxidation or the ozonolysis of certain amino acid residues, for instance, tryptophan, tyrosine and cysteine. As a result of this Attack the protein molecules undergo changes in their usual folding and binding ability and are denaturated as shown by polarimetric or chirooptical measurements and by the inhibition of their biological activity. In any case viscosimetric measurements show that the amide bond of proteins is resistant to the Ozone Attack and no chain scission phenomena occur as in the case of radiolysis of proteins. A special protein is hemoglobin which is characterized by a complex tetrameric structure where each of the 4 polypeptide chains binds a prosthetic haeme group having a porphyn structure. It is shown by a series of systematic studies on model molecules, on the isolated prosthetic groups, on isolated hemoglobin (methemoglobin) and on whole blood that the action of Ozone is sp...
-
On the Action of Ozone on Polyynes and Monocyanopolyynes: Selective Ozonolysis of Polyynes
Fullerenes Nanotubes and Carbon Nanostructures, 2006Co-Authors: Franco CataldoAbstract:Abstract Ozone reacts selectively with hydrogen‐terminated polyynes when they are present in a mixture with monocyanopolyynes. The latter class of molecules reacts more slowly with Ozone. Since the Ozone Attack to double or triple bonds is essentially electrophilic in its nature, the lower reactivity with Ozone of monocyanopolyynes has been interpreted in terms of lower π‐electron charge concentration at the conjugated triple bonds because of the electron‐withdrawing effect exerted by the nitrile group at one end of the monocyanopolyynes molecules. This experimental result demonstrates the presence of conjugation among adjacent triple bonds in the polyynes molecules: the electron‐withdrawing effect of the –CN group propagates along the entire polyyne chains.
W. R. Rutgers - One of the best experts on this subject based on the ideXlab platform.
-
Corona Above Water Reactor for Systematic Study of Aqueous Phenol Degradation
Plasma Chemistry and Plasma Processing, 2006Co-Authors: L. R. Grabowski, E. M. Veldhuizen, A. J. M. Pemen, W. R. RutgersAbstract:A small batch reactor is developed to study the removal of phenol from a thin layer of water by creating pulsed corona discharges above the water. Pulses of up to 40 kV are applied with a duration of ~50 ns and an energy of ~60 mJ. In this CAW (Corona Above Water) reactor an Ozone yield of upto 90 g/kWh is obtained in ambient air. The phenol degradation is 48 g/kWh, using a 1 mM initial concentration in demineralized water. The degradation yield increases to almost 100 g/kWh by adding to the water either H_2O_2 or Fe_2SO_4 or NaOH. The first two additions are considered to increase to amount of OH radicals. In the case of NaOH addition it is observed that much more Ozone dissolves in the water. The addition of the OH scavenger t-butanol shows that in most cases the main oxidation route of phenol in the CAW reactor is direct Ozone Attack.
Andreas Wahner - One of the best experts on this subject based on the ideXlab platform.
-
gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air
Atmospheric Chemistry and Physics, 2012Co-Authors: E Kleist, Heikki Junninen, Tuukka Petaja, Gustaf Lonn, Siegfried Schobesberger, Dal M Maso, A Trimborn, Markku Kulmala, D R Worsnop, Andreas WahnerAbstract:Abstract. High molecular weight (300–650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiala, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night between spring and autumn in Hyytiala. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Julich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3−) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7–1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4− (Hyytiala) and C3F5O2− (JPAC). The most abundant products in the ion spectra were identified as C10H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely Ozone Attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiala, where β-pinene on average is 4–5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1–1 ppt (~106–107 molec cm−3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiala during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and growth may be important and needs to be explored in more detail in the future.
V. Ruiz Santa Quiteria - One of the best experts on this subject based on the ideXlab platform.
-
Influence of Ozone on styrene-ethylene-butylene-styrene (SEBS) copolymer
Polymer Degradation and Stability, 2003Co-Authors: Norman S. Allen, Despina Mourelatou, Arthur Wilkinson, M. Dolores Parellada, Michele Edge, Christopher M. Liauw, Juan A. Barrio, V. Ruiz Santa QuiteriaAbstract:Non-commercial and commercial SEBS copolymer materials have been subjected to severe Ozone treatment for different periods of time and concentrations in an Ozone cabinet in order to obtain a deeper understanding on the mechanism of Ozone Attack in this type of material. The polymer materials were subsequently analysed by FTIR (ATR method), fluorescence and phosphorescence spectroscopy. Hydroperoxide analysis and determination of gel content was also carried out. Original functionalities in the SEBS based on aliphatic vinyl and aromatic (styrene) structures were observed to decrease in intensity and these were consistent with the concurrent formation of ozonide groups. Immediate exposure of SEBS to Ozone resulted in the rapid and consistent formation of a variety of carbonyl and unsaturated carbonyl products based on aliphatic esters, ketones, and lactones as well as aromatic carbonyl associated with the styrene phase. These were followed by a more gradual formation of ether, hydroxyl and terminal vinyl groups with time and concentration. Also, of interest was the evident formation of a strong enol tautomer of a β-diketone functionality. These functional group changes were specific and concentrated on the very surface layer of the SEBS only. Whist there was strong evidence for hydroxyl group formation hydroperoxide analysis showed minimal evidence for active peroxides although growth was consistent with Ozone dosage for the less Ozone resistant materials. No crosslinking was also found in this material. Early decreases in in-chain vinyl groups by FTIR analysis were also consistent with an observed decrease in fluorescence functionalities in the SEBS associated with primarily trans-stilbene groups whereas longer periods of exposure showed new fluorescence functionalities. Phosphorescence analysis showed the formation of acetophenone end groups on the styrene chains associated with chain scission within the aliphatic rubber-styrene interphase region. Commercially Ozone resistant SEBS materials were found to contain lower levels of fluorescent trans-stilbenic chromophores indicating this to be the weak link at the interphase in non-commercial Ozone susceptible samples. Mechanistic routes for these processes are proposed and discussed. © 2002 Elsevier Science Ltd. All rights reserved.
L. R. Grabowski - One of the best experts on this subject based on the ideXlab platform.
-
Corona Above Water Reactor for Systematic Study of Aqueous Phenol Degradation
Plasma Chemistry and Plasma Processing, 2006Co-Authors: L. R. Grabowski, E. M. Veldhuizen, A. J. M. Pemen, W. R. RutgersAbstract:A small batch reactor is developed to study the removal of phenol from a thin layer of water by creating pulsed corona discharges above the water. Pulses of up to 40 kV are applied with a duration of ~50 ns and an energy of ~60 mJ. In this CAW (Corona Above Water) reactor an Ozone yield of upto 90 g/kWh is obtained in ambient air. The phenol degradation is 48 g/kWh, using a 1 mM initial concentration in demineralized water. The degradation yield increases to almost 100 g/kWh by adding to the water either H_2O_2 or Fe_2SO_4 or NaOH. The first two additions are considered to increase to amount of OH radicals. In the case of NaOH addition it is observed that much more Ozone dissolves in the water. The addition of the OH scavenger t-butanol shows that in most cases the main oxidation route of phenol in the CAW reactor is direct Ozone Attack.
