Oxidation of GR-S Vulcanizates

1946 ◽  
Vol 19 (3) ◽  
pp. 696-711
Author(s):  
J. Reid Shelton ◽  
Hugh Winn
Keyword(s):  
General Nature ◽  
Oxygen Absorption ◽  
Specimen Thickness ◽  
Absorption Data ◽  
First Order ◽  
Rapid Absorption ◽  
Constant Rate ◽  
Absorption Studies ◽  
Three Stages ◽  
Useful Life

Abstract Oxygen absorption studies on a tread type GR-S vulcanizate show: 1. There are three stages involved in the oxidation: (1) an initial rapid absorption, of apparent first order at constant pressure, which is of short duration and appears to involve a limited number of especially reactive centers in the vulcanizate ; (2) a constant-rate reaction, of apparent zero order at constant oxygen pressure, which would extend over most of the useful life of the vulcanizate in service ; (3) an autocatalytic reaction, beginning after a given stock has absorbed a definite amount of oxygen that is independent of the temperature at which the absorption takes place. 2. The rate of oxygen absorption increases with temperature. The temperature coefficient for the constant rate reaction is 2.6 for a 10° C change in temperature over the range 80° to 120° C. 3. Diffusion is not rate controlling, provided the specimen thickness does not exceed 0.080 inch at 100° C or 0.040 inch at 120° C. 4. The effect of cure on the rate of oxygen absorption by GR-S vulcanizates is slight, and consequently, the technique is particularly useful for studying the effect of changes in compounding upon aging resistance. 5. Oxygen absorption data can be satisfactorily correlated with changes in physical properties during aging. While the fundamental nature of the mechanism of the oxidation of GR-S is still unknown, considerable information has been obtained with respect to some of the factors involved, and the general nature of the reaction has been established. This information, together with the work still in progress, should be of value in pointing the way toward possible methods of improving the resistance of GR-S to aging.

Rubber Oxidation and Aging Studies Safe Limits of Sample Thickness

1951 ◽  
Vol 24 (4) ◽  
pp. 999-1016
Author(s):  
George W. Blum ◽  
J. Reid Shelton ◽  
Hugh Winn
Keyword(s):  
Natural Rubber ◽  
Accelerated Aging ◽  
Sample Thickness ◽  
Oxygen Absorption ◽  
Absorption Data ◽  
Synthetic Rubber ◽  
Constant Rate ◽  
Aging Studies ◽  
Safe Limits ◽  
Natural Rubber Vulcanizates

Abstract Safe limits of sample thickness for rubber oxidation and aging studies, such that the chemical reaction rather than the rate of diffusion will be rate-controlling have been investigated for natural-rubber vulcanizates and for four synthetic-rubber types. For studies involving the entire range of oxidation, including the autocatalytic stage of rapid oxygen absorption, the conventional 0.075-inch thickness is frequently not satisfactory for accelerated aging and oxidation studies if it is desired to avoid limitation by diffusion. Only in the GR-S black stock was this thickness found to be satisfactory up to a temperature of 100° C. The other stocks, including natural rubber, Butaprene-NXM, and Neoprene black and gum stocks all require thinner samples to ensure that the observed rate of oxygen absorption is free of limitation by diffusion. A method of calculating the probable limiting value of sample thickness, above which the rate of oxidation in the autocatalytic stage is limited by diffusion, has been developed on the basis of volumetric oxygen absorption data obtained with GR-S. The method has also been applied to natural-rubber vulcanizates and to other synthetic-rubber types to locate the approximate limiting values at various temperatures for oxidation and aging studies which extend into the autocatalytic stage of rapid reaction. The constant-rate period of oxidation is more important from a practical point of view than the autocatalytic stage, since properties are so seriously degraded as to make the rubber of little value before it reaches the final stage of rapid oxidation. Somewhat thicker samples may be used for studies that are confined to the earlier stages of oxidation. A 0.075-inch sample is free of limitation by diffusion in the constant-rate stage in the following cases: GR-S black and gum stocks at 110° C; Hevea black with added antioxidant at 100° C; and uninhibited Hevea black and gum stocks at 60° C. A 0.040-inch sample is satisfactory in this range for: uninhibited Hevea black at 100° and gum at 80° C; Butaprene-NXM black at 100° and gum at 90° C; and Neoprene black and gum stocks at 100° C.

Oxidation of Compounds Structurally Related to GR-S

1950 ◽  
Vol 23 (4) ◽  
pp. 836-846 ◽  
Author(s):  
J. W. Lawrence ◽  
J. Reid Shelton
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Absorption ◽  
Phenyl Radical ◽  
Rate Data ◽  
Primary Products ◽  
Period 2 ◽  
Constant Rate ◽  
Three Stages ◽  
Oxidized Products ◽  
Short Induction Period

Abstract The rates of oxidation of 1-phenyl-3-pentene, 1-phenyl-4-hexene, and 1-phenyl-3-vinylbutane have been measured at 100° C and 1 atmosphere of oxygen pressure. 1-Phenyl-2-butene has also been included to complete the sequence 1–4, 1–3, and 1–2 with respect to the structural relationship between the phenyl radical and the point of unsaturation. Information concerning the course of the reaction was obtained both from the rate data and from chemical analysis of the oxidized products. Three stages of oxidation were noted: (1) a very short induction period; (2) an autocatalytic stage which is characterized by a rapidly increasing rate and in which the primary products appear to be peroxides; and (3) a period characterized by a constant rate of oxygen absorption with the formation of such products as acids, esters, carbon dioxide, and water.

PENYERAPAN GAS KARBONDIOKSIDA (CO 2 ) DALAM BIOGAS DENGAN LARUTAN Ca(OH)2

EKUILIBIUM ◽  
2015 ◽  
Vol 14 (1) ◽  
Author(s):  
Paryanto Paryanto
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Order Reaction ◽  
First Order Reaction ◽  
Glass Ball ◽  
Carbon Dioxide Content ◽  
First Order ◽  
Constant Rate ◽  
Rate Of Reaction ◽  
Reduce Carbon Dioxide

<p>Abstract: Carbon dioxide content in biogas produced by fermentation is still high. Because of<br />that, biogas need a process purification to reduce carbon dioxide content. In this work, Ca(OH)2<br />solution was contacted with biogas in a column for reducing the CO<br />2<br />content. This research<br />studied the effect of packing type used in absorber column on the rate of CO<br />2<br />reduction. Based<br />on experimental data and modelling, it was found that the reaction between CO<br />2<br />followed first order reaction. The constant of rate reaction was affected by the packing type<br />which using glass ball, plastic pipe, ceramic, wood, and clay roof, the constant rate were 0.781,<br />0.464, 0.916, 0.637, and 0.987 min<br />Keywords: Biogas, CO<br />2<br />, Ca(OH)2<br />-1<br />, respectively.<br />, absorber, rate of reaction</p>

Numerical Simulation of Unsaturated Evaporation and Drying Front Advancing in One-Dimensional Soil Columns

2013 ◽  
Vol 353-356 ◽  
pp. 730-734
Author(s):  
Zhang Hua ◽  
Gao Kang ◽  
Xiong Yi
Keyword(s):  
Great Influence ◽  
Coupled Model ◽  
Dry Density ◽  
Soil Columns ◽  
Total Evaporation ◽  
One Dimensional ◽  
Actual Evaporation ◽  
Constant Rate ◽  
Three Stages ◽  
Simulation Results

A coupled model of heat-moisture flow with Penman-Wilson evaporation boundary condition is used for simulating evaporation processes in three 1D vertical columns with different dry densities. The simulation results show that unsaturated evaporation process has three stages, i.e. constant-rate stage, falling-rate stage and residual stage. The depth of drying front has a great influence on soil actual evaporation. The actual evaporation decreases as the drying front advancing downward. The total evaporation decreased with the increase of soil dry density. The velocity of drying front advancing in the soil of higher dry density is faster than that of lower dry density.

scholarly journals DESORPSI β-KAROTEN MINYAK KELAPA SAWIT (CRUDE PALM OIL) DARI KARBON AKTIF MENGGUNAKAN ISOPROPANOL

2017 ◽  
Vol 5 (4) ◽  
pp. 1-7
Author(s):  
Nurul Aini ◽  
Olyvia Putri Wardhani ◽  
Iriany
Keyword(s):  
Activation Energy ◽  
Activated Carbon ◽  
Isopropyl Alcohol ◽  
Desorption Kinetics ◽  
Crude Palm Oil ◽  
Desorption Process ◽  
First Order ◽  
Constant Rate ◽  
Β Carotene ◽  
Main Material

The aim of the research is to study the ability of isopropyl alcohol in the desorption of β-carotene and to obtain kinetic model and desorption isoterm which is suitable in β-carotene desorption. The main material used were isopropyl alcohol and activated carbon containing β-carotene. The variabels used in this research are desorption temperature,  activated carbon concentration  and parameter observed is concentration of β-carotene in isopropyl alcohol. In the desorption process, activated carbon which adsorp β-carotene was soaked in isopropyl alcohol. To review the desorption kinetics, this research was carried out in various temperature such as 40 oC, 50 oC, and 60 oC. In desorption isoterm process is, various mass of activated carbon was used. Desorption process will be analyzed at spesified time. This research used the first order of desorption kinetics model. The desorption constant rate obtained for 40 oC, 50 oC, and 60 oC are 0,013, 0,014, and 0,036 minute-1 with activation energy is 0,226 kkal/mol. The maximum desorption percentage obtain is 41,94 %. The desorption isoterm model which fit with the β-carotene desorption was Langmuir isoterm model with constanta value 1,2077 L/mg and -0,2218.

Considerations in Modeling Cell Death Processes

2012 ◽  
Author(s):  
John A. Pearce
Keyword(s):  
Cell Death ◽  
Death Rate ◽  
First Order ◽  
Early Stages ◽  
Rate Region ◽  
Time Scaling ◽  
Tumor Hyperthermia ◽  
Constant Rate ◽  
Shoulder Region ◽  
Single Reaction

Traditional single-reaction Arrhenius models have been successfully used for many years in burn studies[1–3] and have been adapted and used to predict quantitative histologic results in laser, RF and microwave heating at high temperatures.[4–6] The single reaction kinetics model also forms the basis for the time scaling ratio as is currently used in calculating the cumulative equivalent minutes (CEM) assessment of tumor hyperthermia treatments.[7] Recently, it has been clearly demonstrated that these models are not acceptably accurate predictors of the early stages of cell death processes in hyperthermic heating — moderate temperature rises (< ∼15 C) for times from several minutes to hours.[8, 9] A typical ensemble of cell survival curves has an initial slowly-developing shoulder region, a constant-rate region and, often, a “foot’, as it were, which has a much slower death rate. Simple first-order Arrhenius predictions are constant-rate models, only, and substantially over-estimate population cell death in the early stages of heating.

scholarly journals Improving the Imazapyr Degradation by Photocatalytic Ozonation: A Comparative Study with Different Oxidative Chemical Processes

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1446
Author(s):  
Salma Bougarrani ◽  
Zakarya Baicha ◽  
Lahbib Latrach ◽  
Mohammed El Mahi ◽  
Francisco José Hernandez Fernandez
Keyword(s):  
Removal Efficiency ◽  
Ozone Concentration ◽  
Organic Contaminants ◽  
Synergistic Effects ◽  
Heterogeneous Photocatalysis ◽  
Operational Conditions ◽  
Oxidation Processes ◽  
First Order ◽  
Photocatalytic Ozonation ◽  
Constant Rate

The degradation of imazapyr (C13H15N3O3), an active element in the aqueous solution of commercial herbicide, was investigated. This study was the first to evaluate in a comprehensive manner the efficiency of advanced oxidation processes for imazapyr degradation. Results showed that Imazapyr degradation is significantly affected by operational conditions such as TiO2 concentration, ozone concentration, initial concentration of imazapyr and pH. The kinetics of Imazapyr consumption was the first order with respect to Imazapyr concentration and zero order with respect to ozone concentration with a constant rate of 0.247 min−1 and 0.128 min−1 for photocatalytic ozonation and heterogeneous photocatalysis, while it was the first order with respect to Imazapyr and the first order with respect to ozone concentrations when only ozone was used with a constant rate of 0.053 mol L−1 min−1 at pH 7. The results revealed that more than 90 percent of the removal efficiency representing the elimination of imazapyr was held up to 7 μM. Further increase in the concentration of imazapyr leads to a drop in the removal efficiency, however the total imazapyr degradation was reached in 20 min utilizing photocatalytic ozonation for 5 μM of Imazapyr in the presence of 100 mg L−1 of TiO2, 10 mg L−1 of ozone at pH 7. Photocatalytic ozonation and heterogeneous photocatalysis utilizing TiO2 as a semiconductor process appeared possible and well suited for the treatment of organic contaminants such as imazapyr herbicides, although at certain dosages of pH and common time for wastewater treatment, imazapyr was not degraded with ozonation on its own. The association of two oxidation processes, ozonation and photocatalysis, has improved oxidation efficiencies for water treatment under optimal conditions, leading to the development of non-selective hydroxyl and more reactive radicals in the oxidation medium, as well as the resulting synergistic effects between photocatalysis and ozonation that react more rapidly with imazapyr herbicide.

LIGHT ABSORPTION STUDIES: PART VI. THE EFFECTIVE INTERFERENCE VALUES OF NON-BONDED ATOMS IN SOLUTION. PART I. SOME PRELIMINARY OBSERVATIONS

1956 ◽  
Vol 34 (11) ◽  
pp. 1542-1552 ◽  
Author(s):  
W. F. Forbes ◽  
W. A. Mueller
Keyword(s):  
Potential Energy ◽  
Light Absorption ◽  
Interatomic Distance ◽  
Neutral Solution ◽  
Absorption Data ◽  
Absorption Studies ◽  
Minimum Interference

The application of light absorption data to determine minimum interference radii of various atoms in solution is examined. Three separate methods are suggested and the relation between potential energy and interatomic distance of two non-bonded atoms is discussed. The values obtained in neutral solution are as follows: H, 0.95 ± 0.1 Å; O (in C=O), 1.0 ± 0.15 Å; and CH3, 1.7 ± 0.2 Å.

LIGHT ABSORPTION STUDIES: PART V. THE RELATION OF MESOMERIC EFFECTS AND ULTRAVIOLET LIGHT ABSORPTION SPECTRA

1956 ◽  
Vol 34 (10) ◽  
pp. 1447-1456 ◽  
Author(s):  
W. F. Forbes ◽  
Audrey S. Ralph
Keyword(s):  
Absorption Spectra ◽  
Ultraviolet Light ◽  
Light Absorption ◽  
Absorption Data ◽  
Absorption Studies

A method for the determination of mesomeric effects from ultraviolet light absorption data is critically discussed. For halogen-substituted compounds, the method gives an order of mesomeric effects different from that which is usually accepted for the halogens.

Oxidation of Two Isomeric Elastomers: Poly(Propylene Oxide) and Poly(Vinyl Methyl Ether)

1966 ◽  
Vol 39 (2) ◽  
pp. 278-286 ◽  
Author(s):  
Parry M. Norling ◽  
Arthur V. Tobolsky
Keyword(s):  
Methyl Ether ◽  
Propylene Oxide ◽  
Solid Phase ◽  
Chain Scission ◽  
Oxygen Absorption ◽  
Vinyl Methyl ◽  
Absorption Data ◽  
Vinyl Methyl Ether ◽  
Poly Propylene ◽  
Reaction Chain

Abstract Rates of oxygen absorption and chain scission have been measured for benzoyl peroxide initiated oxidation of the two isomeric hydrocarbons, poly(propylene oxide) and poly (vinyl methyl ether) in the temperature range 80–100° C and in the solid phase. Oxygen absorption data show that poly(propylene oxide) forms hydroperoxides 3.5 times as fast as poly (vinyl methyl ether). This may be attributed to steric hindrance in the propagation reaction. Chain scission, measured by stress relaxation of crosslinked samples, demonstrates that each initiating radical produces one scission in the poly(propylene oxide). The process appears to be less efficient in the poly(vinyl methyl ether). Two possible reactions are proposed to explain this observation.

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