Combined Action Of Oxygen Research Articles

STUDIES OF ANTICORROSIVE PROPERTIES MOTOR OILS AND WAYS TO IMPROVE

The purpose of this work is to study how to improve the anticorrosive properties of lubricants. With an increase in temperature, the combined action of oxygen, air and water present in the lubricating oil causes rusting of the crankshaft, the walls of the sleeves, the cylinders of the internal combustion engine. We have studied anticorrosive additives as an additive to improve the anticorrosive properties of oils. dialkylphenyldithiophosphoric acid additive was used as such additives. The anticorrosive activity of these substances is associated with their ability to orient themselves on the oil–water surface so that hydrophilic groups bind firmly to water, and the hydrocarbon radical remains in the oil.

Near-neutral pH corrosion and stress corrosion crack initiation of a mill-scaled pipeline steel under the combined effect of oxygen and paint primer

This investigation was initiated to study near-neutral pH stress corrosion crack initiation of a mill-scaled X65 pipeline steel under cyclic loading and the combined effect of oxygen and paint primer. It was found that the combined action of oxygen and primer layer under cyclic loading increases the corrosion severity but reduces the aspect ratio of the localized corrosion areas because of the vast coalescence of the localized corrosion areas, leading to less tendency towards pit-to-crack transition as compared to the primer-coated specimen in the absence of oxygen. Various factors that affect the corrosion and crack initiation have been studied.

Ways to improve the anticorrosive properties of motor oils used in vehicles

In recent years, increased requirements for protective properties have been imposed on petroleum oils for various purposes. One of the functions of the oil is to protect the surface of parts from corrosion. Corrosion becomes especially intense when the engine is operated in hot, humid climates. In this case, oil plays a double role: on the one hand, it protects the surfaces of parts from the aggressive influence of the external environment; on the other hand, the oil itself is corrosive due to the presence of corrosive substances in it. Corrosion is especially intensified after the engine is stopped. When it cools, moisture condenses on the parts, the lubricating oil, flowing down from the lubricated surface, cannot protect the metal from corrosion. The reason for the corrosive properties of oils is that they contain organic and inorganic acid peroxides and other oxidation products and sulfur compounds, alkalis, and water. The purpose of this work is to study and improve the anti-corrosion properties of lubricants. With an increase in temperature, the combined action of oxygen in the air and water present in the lubricating oil causes rusting of the crankshaft, liner walls, cylinders of the internal combustion engine. We have studied anticorrosive additives as an additive to improve the anti-corrosion properties of oils. Dialkylphenyl orthophosphoric acid additive was used as such additives. The anticorrosive activity of these substances is related to their ability to orient themselves on the oil-water surface so that hydrophilic groups are firmly bound to water while the hydrocarbon radical remains in the oil.

Thermal decomposition of flame retarded formulations PA6/aluminum phosphinate/melamine polyphosphate/organomodified clay: Interactions between the constituents?

The aim of this article is to investigate the thermal decomposition in pyrolytic and oxidative conditions of a phosphorous flame retardant (combination of melamine polyphosphate and aluminum phosphinate: AlPi-MPP) alone as well as in combination with an organo-modified clay (o-MMT) and of polyamide 6 formulations containing these additives. The gases evolved during the decomposition have been analyzed using TGA-FTIR. A detailed condensed phase study has been carried out combining X-ray diffraction (XRD) analyses and 27Al, 31P and 13C solid-state nuclear magnetic resonance (NMR) measurements on samples heat treated at different characteristic temperatures. It is demonstrated that no reaction leading to the formation of new species between the additives or the additives and the matrix occurs. However, Lewis acid/base interactions are highlighted resulting in the catalytic decomposition of the components particularly under nitrogen. Under air, the combined action of oxygen and Lewis interactions leads to an even more catalyzed decomposition process. Mechanisms of thermal decomposition are proposed.

Polymeric coatings for photostability enhancement of poly(p‐phenylene vinylene) derivative films

AbstractPoly(p‐phenylene vinylene) (PPV) derivatives are an important class of conjugated polymers, known for their applications as electroluminescent materials for light‐emitting devices and sensors. These derivatives are highly susceptible to photodegradation by the combined action of oxygen and light. Here, the use of various commercial polymers as protective coatings against the photodegradation of PPV derivatives was explored. Cast films of two similar PPV derivatives, poly[(2‐methoxy‐5‐n‐hexyloxy)‐p‐phenylene vinylene] and poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐p‐phenylene vinylene], were submitted to photodegradation by exposure to white light under atmospheric conditions in order to verify if the type of side chain (linear or branched) had an effect on the photodegradation. No significant differences in the photodegradation behaviour between the two polymers were noticed. The following commercial polymers were tested as protective coatings for the PPV derivative cast films: 99 and 80% hydrolysed poly(vinyl alcohol) (PVA) and starch. The best results were achieved using coatings of 99% hydrolysed PVA, which increased about 700 times the time necessary for complete degradation of the PPV derivative films. The results show the effectiveness of this coating in minimizing and, possibly, controlling the effects of the photodegradation of PPV derivative films, which can be useful in many applications, e.g. oxygen sensors. Copyright © 2009 Society of Chemical Industry

Contribution of Oxidative-Reductive Reactions to High-Molecular-Weight Hyaluronan Catabolism

Since the content of hyaluronan (HA)-degrading enzymes in synovial fluid (SF), if any, is extremely low, the high rate of HA turnover in SF is to result from a cause different from enzymatic catabolism. An alternative and plausible mechanism is that of oxidative-reductive degradation of HA chains by a combined action of oxygen and transition metal cations maintained in a reduced oxidation state by ascorbate.

Copper (sub)oxide formation: a surface sensitive characterization of model catalysts

Model studies on the catalytic methanol oxidation over single and polycrystalline copper have been performed. The catalytic activity was investigated by means of temperature-programmed techniques (thermal desorption and temperature-programmed reaction spectroscopy, TDS and TPRS, respectively). The TPRS experiments call for the existence of chemically inequivalent species of atomic oxygen accessibly for catalytic processes on the copper surface. The surface morphological changes after the combined action of oxygen and methanol were observed by using atomic force (AFM) and scanning electron miscroscopy (SEM) and indicate the participation of not only the surface but to a great extend also the bulk. Furthermore, ex situ X-ray absorption spectroscopy (XAS) at the O K-edge shows that a copper suboxide phase of Cu(x2.5)O is formed at the surface/near-surface region up to a depth of about 100 Å. Core-level (XPS) and valence band (UPS) photoemission suggests that the suboxide phase can be viewed as an oxygen-deficient copper(I) oxide phase exhibiting an increased density-of-states at the Fermi level pointing to an electrically conducting phase. The depth-selective recording of X-ray absorption spectra gives clear evidence of the formation of a protective copper(I) oxide film underneath the suboxide layer covering the bulk metal phase.

Photodestruction of Propionibacterium acnes porphyrins.

The fluorescence spectra of colonies of Propionibacterium acnes were studied under various experimental conditions. The spectra contained peaks at 580 nm and 620 nm. These bands were due to two different components; the 580 nm component was likely to be a metalloporphyrin, and there are indications that the 620 nm component could be a coproporphyrin. The 580 nm fluorescence was destroyed by the combined action of light and oxygen (no destruction under strict anaerobic conditions). A dark period interrupting the bleaching light stopped the destruction of this component for the time of the dark period. The initial production of the 620 nm component was due to the oxygen exposure. Upon light irradiation this component was later destroyed by the combined action of oxygen and light.

Photochemistry of aromatic amino acids in solution. I. DL-phenylalanine, DL-tyrosine and L-dopa

Abstract— The action of ultraviolet radiation on dl‐phenyldanine, dl‐tyrosine and l‐dopa has been studied in dilute aqueous solutions (10‐2M–5 × 10‐3M). Irradiation was performed in nitrogen or in air, at a wavelength of 254nm. The photoproducts of low molecular weight (amino acids, carboxylic acids, amines) were isolated either by chromatography on an ion exchange column or by thin‐layer chromatography and identified mainly by ultraviolet absorption and staining with ninhydrin. The isolation of photopolymers was carried out by chromatography on a Biogel column; identification of these photoproducts was mainly achieved by ultraviolet and infrared spectroscopy.With phenylalanine, which is the most photosensitive amino acid, the principal reaction results in splitting of the side chain, giving alanine, glycine, and four other amine compounds whose structure has not been determined. In air, additional minor products resulting from photooxydation are obtained: ortho, meta and paratyrosine. Traces of phenylethylamine were isolated after irradiation in an inert atmosphere. The polymers produced under air and nitrogen are similar. They probably result from rearrangement of aromatic radicals formed by splitting of the side chain.Tyrosine and dopa, irradiated in air, yield mainly melanin; before polymerization, tyrosine is first converted into dopa. In a inert atmosphere, these aromatic aminoacids also polymerize, giving monophenolic and biphenolic compounds with structure close to that of melanin. The biphenolic polymer (thus obtained from dopa) shows the properties of a leuco derivative of melanin. The monophenolic polymer can be converted into melanin by the combined action of oxygen and ultraviolet radiation. Other reactions give only minor products: parahydroxy‐phenyllactic acid and 3,4‐dihydroxyphenyllactic acid by deamination‐hydroxylation of tyrosine and dopa (in air): meta and paratyrosine by dehydroxylation of dopa, either in air or in nitrogen.