Effect of Oxygen Concentration on Aging of Rubber Vulcanizates - Effect of Partial Pressure of Oxygen on Rate of Oxygen Absorption

Abstract The over-all rate of deterioration of physical properties increases with the oxygen concentration, as would be expected from the increased rate of oxygen absorption: The nature of the deterioration resulting from a given amount of oxygen absorbed is influenced also by changes in the partial pressure of oxygen in the aging atmosphere. It appears that chain scission is favored at higher oxygen concentrations, while cross-linking becomes of greater relative importance at lower oxygen concentrations. These data suggest that R⋅ radicals are more effective than RO2⋅ radicals in reacting with double bonds to form crosslinks. Heat aging in the absence of oxygen, as observed by heating a vulcanizate in lamp-grade nitrogen, results in considerable stiffening, particularly in the case of a GR-S black stock. This effect is observed primarily in the first few hours of heating, and may account for some of the erratic behavior observed in the early stages of aging when changes in physical properties are compared on the basis of amount of oxygen absorbed. Higher oxygen concentration brings about a more rapid oxidation, and also results in a higher proportion of chain scission compared to cross-linking for a given amount of oxygen absorbed. As tensile decay is the most evident sign of deterioration of Hevea stocks, it follows that the aging behavior of natural rubber in air at normal storage temperatures will be better than that predicted by high temperature testing in oxygen. In the case of GR-S stocks, on the other hand, oxidative hardening is the most serious result of aging, and consequently, the aging behavior of GR-S stocks in air at normal storage temperatures is poorer than would be expected on the basis of comparative tests in oxygen at higher temperatures.

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Effect of Oxygen Potential on Crack Growth in Alloys for Advanced Energy Systems

Fourth International Topical Meeting on High Temperature Reactor Technology, Volume 2 ◽

10.1115/htr2008-58269 ◽

2008 ◽

Author(s):

Julian K. Benz ◽

J. H. Kim ◽

Ronald G. Ballinger

Keyword(s):

Growth Rate ◽

Oxygen Partial Pressure ◽

Partial Pressure ◽

Crack Growth ◽

Oxygen Concentration ◽

Crack Path ◽

Fatigue Loading ◽

Effect Of Oxygen ◽

Static Conditions

The effect of oxygen partial pressure on fatigue and SCC growth rates in alloy 617 has been studied using both static and fatigue loading @ 650°C over the oxygen partial pressure range 10−19–10−2 atm. Tests were conducted at either constant stress intensity factor, K, for static conditions or constant ΔK in fatigue. Oxygen concentration was measured on both the inlet and outlet as well as in-situ with a probe located directly at the specimen surface. For fatigue loading the crack path was observed to be transgranular but crystallographic with a decreasing growth rate as the oxygen concentration decreased. However, for static loading the crack path shifted to intergranular and exhibited an increasing crack growth rate with decreasing oxygen concentration.

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Effect of Oxygen Potential on Crack Growth in Alloys for Advanced Energy Systems

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3155793 ◽

2010 ◽

Vol 132 (10) ◽

Cited By ~ 4

Author(s):

Julian K. Benz ◽

Ji Hyun Kim ◽

Ronald G. Ballinger

Keyword(s):

Growth Rate ◽

Oxygen Partial Pressure ◽

Partial Pressure ◽

Crack Growth ◽

Oxygen Concentration ◽

Crack Path ◽

Fatigue Loading ◽

Effect Of Oxygen ◽

Static Conditions

The effect of oxygen partial pressure on crack growth rates in Alloy 617 has been studied using both static and fatigue loadings at 650°C over the oxygen partial pressure range 10−19−10−3 atm. Tests were conducted at either the constant stress intensity factor K for static conditions or the constant ΔK in fatigue. Oxygen concentration was measured on both the inlet and outlet of the test retort as well as in situ with a probe located directly at the specimen surface. For fatigue loading the crack path was observed to be transgranular but crystallographic with a decreasing growth rate as the oxygen concentration decreased. However, for static loading the crack path shifted to intergranular at the same Kmax (fatigue) and exhibited what appears to be an increasing crack growth rate with decreasing oxygen concentration.

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A high temperature, pressure study of the comparative rates of enolization and oxidation of acetone in aqueous solution

Canadian Journal of Chemistry ◽

10.1139/v86-369 ◽

1986 ◽

Vol 64 (11) ◽

pp. 2235-2237 ◽

Cited By ~ 2

Author(s):

John W. Thomas ◽

Jay E. Taylor

Keyword(s):

Aqueous Solution ◽

High Temperature ◽

Partial Pressure ◽

Oxygen Concentration ◽

Total Pressure ◽

Room Temperature ◽

Isotopic Exchange ◽

Partial Pressure Of Oxygen

The rate of enolization and acetone has been determined as 6.6 × 10−4 s−1 at 193.5 °C under nitrogen at 136 atm total pressure via isotopic exchange. The rate of oxidation was determined to be 8.8 × 10−6 s−1 at 193.5 °C in 123 atm partial pressure of oxygen (136 atm total pressure). In a previous study it was shown that the rates of oxidation of several ketones correlated with the extents of enolization at room temperature. This prompted the suggestion that the enol is an intermediate in the oxidation. Since the rate of enolization exceeded the rate of oxidation by a factor of 75, this suggestion is further supported. A dependence of the rate of oxidation of acetone on oxygen concentration was also demonstrated.

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ARTIFICIAL HYPOBIOSIS AS A METHOD TO MITIGATE THE NEGATIVE EFFECT OF OXYGEN AT AN ELEVATED PARTIAL PRESSURE

Aerospace and Environmental Medicine ◽

10.21687/0233-528x-2021-55-5-64-68 ◽

2021 ◽

Vol 55 (5) ◽

pp. 64-68

Author(s):

A.F. Makarov ◽

◽

M.A. Kotsky ◽

А.А. Ton'shin ◽

I.V. Bukhtiyarov ◽

...

Keyword(s):

Partial Pressure ◽

Gas Pressure ◽

Pressure Reduction ◽

Partial Pressure Of Oxygen ◽

High Partial Pressure ◽

Artificial Hypobiosis ◽

Negative Effect ◽

Effect Of Oxygen

To assess how hypobiosis modifies the negative effect of a high partial pressure of oxygen, goldhamsters were put into artificial hypobiosis followed by a simulated O2 poisoning at absolute gas pressure of 7 kgf/cm2. The experiment showed an increase in 1.4 times (p = 0.0579) of the period preceding convulsions; reduction in 3.7 times (p = 0.0009) of the period of stabilization on return to normal O2 pressure, reduction of the total convulsions period in 2.3 times (p = 0.0003).

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Interaction of H2O, O2 and H2 with Proton Conducting Oxides Based on Lanthanum Scandates

Alternative Energy and Ecology (ISJAEE) ◽

10.15518/isjaee.2019.13-15.88-100 ◽

2019 ◽

pp. 88-100

Author(s):

A. S. Farlenkov ◽

N. A. Zhuravlev ◽

Т. A. Denisova ◽

М. V. Ananyev

Keyword(s):

Water Vapor ◽

Partial Pressure ◽

Gas Phase ◽

Molecular Hydrogen ◽

Proton Magnetic Resonance ◽

Partial Pressure Of Oxygen ◽

Proton Conducting ◽

Conducting Oxides ◽

Temperature Range ◽

Apparent Level

The research uses the method of high-temperature thermogravimetric analysis to study the processes of interaction of the gas phase in the temperature range 300–950 °C in the partial pressure ranges of oxygen 8.1–50.7 kPa, water 6.1–24.3 kPa and hydrogen 4.1 kPa with La1–xSrxScO3–α oxides (x = 0; 0.04; 0.09). In the case of an increase in the partial pressure of water vapor at a constant partial pressure of oxygen (or hydrogen) in the gas phase, the apparent level of saturation of protons is shown to increase. An increase in the apparent level of saturation of protons of the sample also occurs with an increase in the partial pressure of oxygen at a constant partial pressure of water vapor in the gas phase. The paper discusses the causes of the observed processes. The research uses the hydrogen isotope exchange method with the equilibration of the isotope composition of the gas phase to study the incorporation of hydrogen into the structure of proton-conducting oxides based on strontium-doped lanthanum scandates. The concentrations of protons and deuterons were determined in the temperature range of 300–800 °C and a hydrogen pressure of 0.2 kPa for La0.91Sr0.09ScO3–α oxide. The paper discusses the role of oxygen vacancies in the process of incorporation of protons and deuterons from the atmosphere of molecular hydrogen into the structure of the proton conducting oxides La1–xSrxScO3–α (x = 0; 0.04; 0.09). The proton magnetic resonance method was used to study the local structure in the temperature range 23–110 °C at a rotation speed of 10 kHz (MAS) for La0.96Sr0.04ScO3–α oxide after thermogravimetric measurements in an atmosphere containing water vapor, and after exposures in molecular hydrogen atmosphere. The existence of proton defects incorporated into the volume of the investigated proton oxide from both the atmosphere containing water and the atmosphere containing molecular hydrogen is unambiguously shown. The paper considers the effect of the contributions of the volume and surface of La0.96Sr0.04ScO3–α oxide on the shape of the proton magnetic resonance spectra.

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