Peroxide Decomposition Products Research Articles

Aqueous decomposition behavior of solid peroxides: Effect of pH and buffer composition on oxygen and hydrogen peroxide formation

The ability of solid peroxides to provide sustained release of both oxygen and hydrogen peroxide makes them potentially suitable for oxygen release or antibacterial applications. Most recent reports using solid peroxides to augment oxygen levels do so by compounding solid peroxide powders in polymers to retard the aqueous decomposition. Compounds with peroxidase activity may be added to reduce hydrogen peroxide toxicity. Peroxides are rarely pure and are mixed with oxide and themselves decompose to form hydroxides in water. Therefore, even if buffering strategies are used, locally the pH at the surface of aqueously immersed peroxide particles is inevitably alkaline. Since pH affects the decomposition of peroxides and hydrogen peroxide stability, this study compared for the first-time the aqueous decomposition products of hydrogen and inorganic peroxides that are in use or have been used for medical applications of have been evaluated preclinically; calcium peroxide (CaO2), magnesium peroxide (MgO2), zinc peroxide (ZnO2), sodium percarbonate (Na2CO3.1.5H2O2) and hydrogen peroxide (H2O2). Since plasma can be approximated to be carbonate buffered phosphate solution, we maintained pH using carbonate and phosphate buffers and compared results with citrate buffers. For a given peroxide compound, we identified not only a strong effect of pH but also of buffer composition on the extent to which oxygen and hydrogen peroxide formation occurred. The influence of buffer composition was not previously appreciated, thereby establishing in vitro parameters for better design of intentional release of specific decomposition species. Statement of significanceThis paper compares for the first time the aqueous decomposition products oxygen and hydrogen peroxide of solid peroxy compounds of metal cations, (calcium, magnesium, sodium and zinc) across a pH range that could feasibly be found in the body, (pH 5,7, 9) either physiologically or pathologically. We find that in addition to pH, buffer composition is also a critically important factor, making translation from in vitro models challenging. Cytotoxicity was related to hydrogen peroxide release, alkalinity and in the case of zinc peroxide to the cation itself. In vitro and preclinical studies generally report release data from polymer-peroxide composites and rarely compare peroxides with one another. Together our data provide guidance for oxygen and ROS delivery from these inorganic materials.

Approach to solution of tank with hydrogen peroxide pressurization by its decomposition products

Aim. To find and confirm the possibility of hydrogen peroxide tank pressurization using high-temperature pressurization gas (~1100К) with a high percentage of steam (up to 70%) without its losses. Research methods. Mathematical modeling of pressurization system parameters with the theory of mass transfer and thermodynamic of variable mass bodies have been used. Results. The conducted research allowed us to find and confirm the possibility of using a new pressurization method with additional sources of heat and elaborate recommendations for its appliance during pressurization time. Scientific novelty. The main processes have been determined, which prevent implementation of the efficient high-temperature pressurization system of the tank with the hydrogen peroxide using peroxide decomposition products. The main obstacle is the volume condensation of vapor in the free volume of the tank when heat exchange processes with boundary surfaces take place. For the first time, by means of theoretical calculations, the expediency and rationality of using the additional sources of heat such as high-temperature combustion product of solid-fuel gas generator based on sodium azide have been proved. Using of this additional source for the first 30 seconds of engine operation has been proved. Practical value. Methodology of pressurization system parameters’ calculation was supplemented with discovered thermodynamic relation, which allowed us to calculate the amount of vapor and take some measures to eliminate the condensation. Results of the research allowed the designation of the pressurization system for the highly concentrated hydrogen peroxide tank with a high value of length to diameter relation with its high-temperature decomposition products.

Aqueous Decomposition Behavior of Solid Peroxides: Effect of pH and Buffer Composition on Oxygen and Hydrogen Peroxide Formation

The ability of solid peroxides to provide sustained release of both oxygen and hydrogen peroxide makes them potentially suitable for oxygen release or antibacterial applications. Most recent reports using solid peroxides to augment oxygen levels do so by compounding solid peroxide powders in polymers to retard the aqueous decomposition. Compounds with peroxidase activity may be added to reduce hydrogen peroxide toxicity. Peroxides are rarely pure and are mixed with oxide and themselves decompose to form hydroxides in water. Therefore, even if buffering strategies are used, locally the pH at the surface of aqueously immersed peroxide particles is inevitably alkaline. Since pH affects the decomposition of peroxides and hydrogen peroxide stability, this study compared for the first-time the aqueous decomposition products of hydrogen and inorganic peroxides that are in use or have been used for medical applications of have been evaluated preclinically; calcium peroxide (CaO2), magnesium peroxide (MgO2), zinc peroxide (ZnO2), sodium percarbonate (Na2CO3.1.5H2O2) and hydrogen peroxide (H2O2). Since plasma can be approximated to be carbonate buffered phosphate solution, we maintained pH using carbonate and phosphate buffers and compared results with citrate buffers. For a given peroxide compound, we identified not only a strong effect of pH but also of buffer composition on the extent to which oxygen and hydrogen peroxide formation occurred. The influence of buffer composition was not previously appreciated, thereby establishing in vitro parameters for better design of intentional release of specific decomposition species.

Study of the unusable liquid propellant residues evaporation processes parameters in the tanks of the launch vehicle expended stage in microgravity

A method is proposed for studying the evaporation process of unusable rocket propellant (RP) residues in an expended stage (ES) under weightless conditions. Two options were considered as boundary conditions for liquid RP residues: a) liquid drop distribution in N identical drops, whose surface decreases during evaporation and b) the liquid distribution in the lower tank bottom and the mirror presence, whose area decreases during evaporation. A high-temperature stream of hydrogen peroxide decomposition products is used as a heat carrier (HC) fed to the fuel tank. The physical and mathematical model of the liquid evaporation process is based on the first thermodynamics law. Based on the analysis of the Frud and Grashof criteria, the assumption that there is no convection movement inside the drop (Rayleigh number is less than critical) for both boundary conditions variants, the heat transfer coefficient of the gas-vapor mixture (GVM) produced in the tank is determined due to the regression dependence obtained under ground conditions as a function of the Nusselt, Reynolds and Prandtl numbers. GVM parameters for the considered boundary conditions variants and the proposed physical mathematical model are compared with the results obtained earlier for the boundary conditions variant of uniform fluid distribution over the inner tank wall (third boundary conditions variant) and the boundary layer theory usage based on integral impulses, energy and diffusion ratios. The thermophysical GVM parameters and the GVM exhaust velocity for oxygen and kerosene are provided for two boundary conditions types, using the example of Soyuz-2.1.v type fuel tanks. The total mass of the RP residues evaporation system structure is less than 1.3% of the total “dry” ES design mass.

Long-term conductivity decrease of polyethylene and polypropylene insulation materials

This work summarizes the results of a number of DC conductivity measurement studies on polypropylene (PP), low density polyethylene (LDPE), and cross linked polyethylene (XLPE). The main observation is that under apparently time-constant external conditions (voltage, temperature, etc.) no steady-state direct current (DC) was established even after very long measurement times. Nevertheless, this behavior seems to exhibit some common systematic features, and since the experiments were performed with different equipment at different R&D labs in different years by different teams, simple measurement artefacts can be excluded. One observation is that there are two electric field regimes with slightly different behavior, separated by crossover field of about 10–15 kV/mm. In this work we focus on the high-field region, where the main observation is that the conductance slowly decays sub-linearly with time, I∼ t−n, with 0.3 < n < 1, n mostly around 0.5. We provide experimental indications that this behavior is rather independent of the presence of 1) the voltage and 2) the peroxide decomposition products (in PE). The observations are in favor of an underlying thermally driven relaxation process related to structural changes (morphology, free volume) of the polymer. A main implication of the results is that the use of steady-state conductivity values for the characterization of certain polymer insulation is not appropriate and instead the decaying behavior of the conduction current must be considered.

Effect of heat-treatment and sample preparation on physical properties of XLPE DC cable insulation material

Power cables with extruded crosslinked polyethylene (XLPE) insulation are used in HVAC and HVDC applications. These cables usually go through a degassing process to remove the methane formed in XLPE during the cross-linking reactions. In case of HVDC cables, the general belief is that the polar peroxide decomposition products (PDP) content significantly influences the conduction and space charge behavior of XLPE. This belief is mainly based on the results of experiments made on thin XLPE samples with different heat-treatments; but since heat-treatment also influences the morphology of the polymer, it is necessary to consider this effect as well. It is common to use polyethylene terephthalate (PET) film as a protective layer during sample press molding. Studies on the influence of the pressing film on the electrical properties of the sample are rare. In this work, the results of a series of experiments performed on 0.5 mm thick XLPE plaque samples in reference to additive free LDPE samples with different heat-treatment times are presented. Beside the PDP content, the morphology, DC conductivity and polarization properties are studied and analyzed. It was found that the pressing film used during sample preparation has a significant effect on the results and if not corrected, it may lead to wrong conclusions about the influence of the PDP content. Eliminating the effect of the pressing film, no clear correlation between the DC conductivity, dielectric loss and the PDP content was observed. The relation between the PDP content and DC conductivity is not found to be obvious, hence this correlation may need to be further evaluated.

Peroxide vulcanization of natural rubber. Part I: effect of temperature and peroxide concentration

Abstract Four different peroxides as curing agents were used to prepare vulcanizates based on natural rubber (NR). The effects of temperature and peroxide concentration on the vulcanization characteristics of rubber compounds, cross-link density (ν) and physical-mechanical properties of equivalent vulcanizates were investigated. The results revealed that the vulcanization temperature and also the relative amount of peroxide decomposition products are of significant importance in the properties of vulcanizates. Lower vulcanization temperature and lower concentration of peroxides were found to be better factors, showing a proper balance between the degree of cross-linking of the rubber and degradation of the macromolecular chains by side reactions in relation to the crystallization of NR, which imparts vulcanizates based on NR outstanding properties.

Inhibition of Endothelial Cell Mediated Low-Density Lipoprotein Oxidation by Green Tea Extracts

Plant phenolics present in fruits and vegetables and that are particularly rich in tea and wine have received considerable attention because of their potential antioxidant activity. Two types of commercial green tea from Japan and two active components of green tea, catechin and epicatechin, were assessed for their relative abilities to inhibit the oxidation of low-density lipoprotein (LDL) mediated by human aortic endothelial cells (HAEC). The tea extracts, catechin and epicatechin, were incubated with HAEC and LDL for 12 h. After incubation, conjugated dienes were measured by spectrophotometry at 234 nm as an index of hydroperoxide formation, and hexanal was measured by static headspace gas chromatography as an index of hydroperoxide decomposition. On the basis of conjugated dienes and hexanal, inhibition of LDL oxidation was dose dependent for all compounds tested. LDL oxidation was inhibited 3.9−98% at concentrations ranging from 0.08 to 5 ppm of the green tea extracts. Both catechin and epicatechin inhibited oxidation by 0.5−97% at concentrations ranging from 0.08 to 5.00 μM. The pure compounds and the two tea extracts tested inhibited the formation of early lipid peroxidation products as well as the end stage lipid peroxide decomposition products. The polyphenolic components of green tea may have nutritional benefits as inhibitors of LDL oxidation. Keywords: Antioxidants; green tea; catechin; epicatechin; plant phenolics; human aortic endothelial cells; low-density lipoprotein (LDL) oxidation

NG-nitro- l-arginine methyl ester protects against lipid peroxidation in the gerbil following cerebral ischaemia

The aim of this study was to assess the role of nitric oxide (NO) in lipid peroxidation following 5 min of bilateral carotid occlusion in the Mongolian gerbil. The study consisted of 4 experimental groups ( n = 10). Animals were either sham operated, subjected to bilateral carotid occlusion or administered the NO synthase inhibitor N G-nitro- l-arginine methyl ester (L-NAME) (10 mg/kg i.p.) 30 min, 6, 24 and 48 h following sham operation or 5 min bilateral carotid occlusion. Animals were killed 96 h post surgery and changes in the concentrations of malonaldehyde and 4 hydroxyalkenals (the main decomposition products of peroxides derived from polyunsaturated fatty acids and related esters) were measured in the hippocampus and cortex using the LPO-586 colorimetric method. The results showed a significant increase in the concentrations of both decomposition products following 5 min of bilateral carotid occlusion. L-NAME administered to sham operated controls had no effect, but in those animals subjected to 5 min of bilateral carotid occlusion L-NAME significantly decreased the levels of both decomposition products. These results suggest that inhibition of NO synthase activity decreases lipid peroxidation in the gerbil model of cerebral ischaemia.

Substituent Effects in the Decomposition of t-Alkyl t-Butyl Peroxides

Abstract The decomposition rates and products of various t-alkyl t-butyl peroxides were examined in cumene at several temperatures. The decomposition of these peroxides took place homolytically, depending on the structure of the t-alkoxyl moieties (RC(CH3)2–O), and was retarded in the order: R=(CH3)3CCH2&amp;gt;(CH3)2CH&amp;gt;CH3CH2CH2&amp;gt;PhCH2&amp;gt;CH3CH2&amp;gt;ClCH2&amp;gt;CH3. The rate constants for the electron-donating alkyl substitutents at 150 °C are correlated very well to a Taft equation (logkd=−10.93 Σσ*−6.61 (correlation coefficient of 0.9501)), which is fairly different from the equation logkd=−10.131 Σσ*−3.422 for electorn-withdrawing polar substituents. From this correlation and a product analysis, the nature of the polar character at the transition state of the decomposition is discussed.

Radical‐catalyzed homopolymerization of maleic anhydride in presence of polar organic compounds

AbstractPolar organic compounds either (1) inhibit the peroxide‐catalyzed bulk homopolymerizations of both MAH and MMA at 80°C, (2) do not inhibit the polymerization of either MAH or MMA, or (3) inhibit the polymerization of MAH but not that of MMA. Compounds generally used as polymerization inhibitors or antioxidants inhibit the polymerizations of both MAH and MMA, presumably by interaction with peroxide decomposition products. Ketones, ethers, acids, esters, nitriles, imides, sulfones, sulfonates, sulfonamides, and acyl disulfides do not inhibit either MAH or MMA polymerization. However, amides, lactams, carbamates, amine oxides, phosphites, phosphates, phosphonates, phosphoramides, phosphine oxides, monosulfides, sulfoxides, aryl disulfides, and thiazyl disulfides inhibit the polymerization of MAH but not that of MMA. Inhibition presumably occurs as a result of electron transfer from the nitrogen‐, phosphorous‐ or sulfur‐containing electron donor compound to the MAH carbocation which is an intermediate in the polymerization of MAH.

Chemorheological Studies of a γ‐Irradiated Dimethylsiloxane Elastomer

The degradation of a peroxide‐cured polydimethylsiloxane (PDMS) elastomer subjected to γ‐irradiation at various temperatures has been studied by chemorheological techniques. Preliminary investigations of the thermal degradation of mechanisms operative in the elastomer utilising continuous and intermittent stress relaxation measurements revealed that degradation took place by a chain interchange reaction. The cleavage reaction occurred randomly along the main chain and was a hydrolytic scission reaction catalyzed by the presence of peroxide decomposition products in the material—namely, 2, 4‐dichlorobenzoic acid. Subsequent chain reformation took place by the condensation of silanol chain end groups. The reaction was found to have an activation energy of 15±4 kJ mol−1. Intermittent stress relaxation techniques revealed that the net crosslink density of the elastomer increased as thermal degradation proceeded. This phenomenon has not been reported in any previous studies of the thermal degradation of PDMS elastomers. The effect has been attributed to the reformation of network chains cleaved during the post‐cure operation prior to the commencement of the thermal degradation studies. This reaction which is also believed to take place by the condensation of silanol groups, occurs simultaneously with the conventional interchange reaction. Continuous stress relaxation studies during γ‐irradiation indicated that the rate of the radiation induced scission reaction increased with increasing temperature. The temperature dependence of this rate did not obey the Arrhenius relationship suggesting a possible change in the scission kinetics at higher temperatures. For the particular sample geometry in the investigations, it was discovered that there was no significant difference between the response of elastomers tested in air and in an inert atmosphere.

Oxidation of human low density lipoprotein results in derivatization of lysine residues of apolipoprotein B by lipid peroxide decomposition products.

Modification of low density lipoproteins (LDL) by oxidation has been shown to permit recognition by the acetyl-LDL receptor of macrophages. The extensive oxidation of LDL that is required before interaction occurs with this receptor produces major alterations in both the lipid and protein components of LDL. Several chemical modifications of LDL also lead to recognition by this receptor; all of these involve derivatization of lysine residues of apolipoprotein B by adducts that neutralize the positively charged epsilon-amino group. The present studies show that oxidation also results in derivatization of LDL lysine residues. Analysis of amino acid composition indicated that 32% of lysine residues were modified after oxidation of LDL by exposure to 5 microM CuSO4 for 20 h. About one-half of the derivatized lysines were labile under the conditions of acid hydrolysis. Fluorescence of LDL protein was greatly increased by oxidation, with excitation maximum at 350 nm and emission maximum at 433 nm. When LDL containing phosphatidylcholine with isotopically labeled arachidonic acid in the sn-2 position was oxidized, there was a 5-fold increase in radioactivity bound to protein compared to nonoxidized LDL or oxidized LDL labeled with 2-[1-14C]palmitoyl phosphatidylcholine. Prior methylation of LDL prevented the rapid uptake and degradation by macrophages that normally accompanies oxidation. These findings suggest that oxidation of LDL is accompanied by derivatization of lysine epsilon-amino groups by lipid products and that these adducts may be important in the interaction of oxidized LDL with the acetyl-LDL receptor.

Photosensitization of membrane components

The chemical mechanisms of the photosensitized peroxidation of unsaturated fatty acids and cholesterol are reviewed and the subsequent reactions of peroxide decomposition products with biological targets such as DNA and amino acids are analyzed. The importance of protein photooxidation and cross-linking in membrane function impairment is discussed.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry: VIII. Volatile thermal decomposition products of hydroperoxy cyclic peroxides

AbstractSecondary oxidation products are important sources of volatiles because of their susceptibility to further decomposition. Volatiles from the thermal decomposition of hydroperoxy cyclic peroxides have been identified by capillary gas chromatography followed by mass spectrometry (GC‐MS). By using a saturated hydroperoxy cyclic peroxide as a synthetic model, the thermal decomposition pathways have been elucidated. Main cleavage occurs between the peroxide ring and the carbon‐bearing hydroperoxide group. Volatiles produced were generally similar to those from corresponding monohydroperoxides. New volatiles identified included methyl furan octanoate, methyl ketones, and conjugated diunsaturated aldehyde esters. The general fragmentation observed between the peroxide ring and the hydroperoxide‐bearing carbons is sufficiently predictable that it can be used as a tool for the structural characterization of hydroperoxy cyclic peroxides. Hydroperoxy cyclic peroxides from autoxidized and photosensitized oxidized methyl linolenate are suggested as important precursors of volatiles that may affect flavor quality of lipid‐containing foods.

Influence of ferrous ions on CCl4-induced lipid peroxidation.

Many toxic chemicals, including CC14, induce the formation of lipid peroxides in the liver (Plaa and Witschi, 1976; Tappel, 1980). Lipid peroxidation, therefore, might be one of the mechanisms involved in their toxicity. However, the direct measurement of lipid peroxides, the primary candidates for toxic reactions, cannot be quantitatively determined either in vitro or in vivo. Only decomposition products of lipid peroxides are measurable, such as malondialdehyde or alkanes (for review see Tappel, 1980). Furthermore, it has been assumed that the decomposition products of lipid peroxides induced by CC14 are the toxic intermediates, rather than the lipid peroxide itself (Mead, 1976; Miguel, 1977; Recknagel et al., 1977; Gardner, 1979). Dialyzable and extractable cytotoxic products occurring during lipid peroxidation have been described recently by several authors (Roders et al., 1978; Willis et al., 1979; Benedetti et al., 1979a,b,1980; Schulze and Kappus, 1980).

HPLC and DSC Analysis of Crosslinked PE from HV Cables

High performance liquid chromatography (HPLC) has beenused to simultaneously determine the amounts of antioxidant(Santonox(R) R), peroxide, acetophenone and ?-methylstyrenepresent in crosslinked-polyethylene cable samples andmolded specimens, as well as to detect some other peroxidedecomposition products.It was found that the antioxidant is grafted to thepolymer chains after curing (even after partial curing).Results also seem to suggest that a reduction of the phenoliccharacter and perhaps of the effectiveness of thentiantioxidant might result from this grafting process. Peroxidedecomposition products were found to depend on the curingconditions used and to affect the dielectric behavior insome cases.Various XLPE and EPR materials have also been examined bydifferential scanning calorimetry (DSC), and experimentalprocedures were developed for evaluating the degree ofcrosslinking by DSC.This work was part of a program supported by the Electric Power Research Institute.

Calculation of the influence of various radical pairs on the CIDNP of the decomposition products of asymmetric diacyl peroxides

Calculation of the influence of various radical pairs on the CIDNP of the decomposition products of asymmetric diacyl peroxides

About the Significance of Peroxide Decomposition Products in Xlpe Cable Insulations

This investigation is concerned with voltage stabilizing effects of peroxide decomposition products, measured by electrical treeing resistance. Trees are filled with a liquid, consisting of decomposition products. These details and the relationship to the treeing phenomenon are described and explained. The treeing resistance efficiency of individual substances and their reliability over a prolonged period of time in EHV insulation is pointed out.

Measuring flavor deterioration of fats, oils, dried emulsions and foods

Abstract and SummaryIn fats, oils, and simple systems such as model dried emulsions, conventional measurements such as peroxide values and oxygen absorption measurements usually give a valid measure of sample flavor. In real food systems, this is often not the case. Measures of volatile (CO2, pentane) and nonvolatile (anisidine reactive compounds) peroxide decomposition products often give a better picture of the organoleptic status of a sample. Unusually large amounts of CO2 are liberated when fats and oils oxidize in the presence of proteins. The implications of this phenomenon are discussed.