Structural Changes in Rubber Caused by the Action of Molecular Oxygen. V. Destructive Solution of Vulcanized Synthetic Rubbers

1953 ◽  
Vol 26 (4) ◽  
pp. 787-797
Author(s):  
Z. Tarasova ◽  
B. Dogadkin
Keyword(s):  
Natural Rubber ◽  
Molecular Oxygen ◽  
Structural Changes ◽  
Axial Ratio ◽  
Colloid Solution ◽  
Butadiene Rubber ◽  
Rate Of Absorption ◽  
The Mean ◽  
Kinetics Of ◽  
Butadiene Styrene

Abstract 1. Vulcanized synthetic rubbers, when heated in a hydrocarbon medium containing molecular oxygen, dissolve completely. The kinetics of destructive solution of vulcanized synthetic rubbers follows the pattern established for the destructive solution of vulcanized natural rubber. 2. The rate of destructive solution of a vulcanizate depends on the molecular structure of the rubber. Rubbers are classified in the following order according to the increase of rate of solution of their vulcanizates : Butyl rubber < sodium-butadiene rubber < butadiene-styrene rubber < polychloroprene < natural rubber. The apparent energy of activation of natural rubber is 19 kcal. per mole, for sodium-butadiene rubber 31.2 kcal. per mole, and for butadiene-styrene rubber 27.1 kcal. per mole. 3. The rate of destructive solution of vulcanized butadiene rubbers depends linearly on the extent of 1,4-structure in the rubber molecule. 4. The mechanical properties of vulcanizates do not appreciably influence the rate of their destructive solution. The type of accelerator used, however, is of essential importance; in fact, its influence corresponds to its influence on the rate of absorption of oxygen. 5. The presence of water slows down the dissolution of vulcanizates of natural and sodium-butadiene rubbers, since it retards their absorption of oxygen. 6. The rate of destructive solution of a vulcanizate in various solvents depends linearly on the coefficient of absorption of oxygen in the solvents. 7. The viscosity of a solution of decomposed vulcanized sodium-butadiene rubber depends linearly on the concentration up to 50 per cent. 8. The mean specific molecular weight, measured cryoscopically, of sodium-butadiene rubber was 2400– 3600, and the osmotic weight, 16,000. The axial ratio of the particles was 1:15. 9. The hypothesis is advanced that solutions of decomposed vulcanizates constitute a special type of colloid solution.

Studies of the Vulcanization of Rubber. III. Kinetics of Change of Tensile Strength of Natural Rubber during Vulcanization

1954 ◽  
Vol 27 (3) ◽  
pp. 615-621 ◽  
Author(s):  
B. Dogadkin ◽  
B. Karmin ◽  
I. Golberg
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Structure Formation ◽  
Linear Function ◽  
General Equation ◽  
Original Material ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Butadiene Styrene

Abstract 1. It is shown that the tensile strength of vulcanized butadiene-styrene rubber is a linear function of the plasticity of the original material. 2. Proceeding from concepts of the presence during vulcanization of a number of opposing processes of structure formation and destruction, both of which influence the molecular weight of the rubber, a general equation is derived which expresses the kinetics of the change of tensile strength of a vulcanizate. 3. Experimental material is offered which proves the applicability of the proposed equation to the representation of the kinetics of vulcanization of mixtures of natural rubber containing relatively small sulfur contents, i.e., up to 3 per cent.

Structural Changes in Rubbers Brought about by Molecular Oxygen

1948 ◽  
Vol 21 (1) ◽  
pp. 48-59
Author(s):  
B. Dogadkin
Keyword(s):  
Molecular Oxygen ◽  
Structural Changes ◽  
Secondary Process ◽  
Initial Structure ◽  
Butadiene Rubber ◽  
Linear Polymers ◽  
Spatial Structures ◽  
Double Bonds ◽  
Solvent Medium ◽  
Wide Range

Abstract The nature of the changes of physical properties of rubber resulting from oxidation processes is determined by its initial structure and also by the conditions of the process (temperature, concentration of reagents, extent of their interaction, type of reaction, etc.). In the interaction of molecular oxygen with linear polymers containing double bonds in the main chains, e.g., with natural rubber, a disintegration of the chains takes place in the initial stages, as a result of which an increase of solubility, a decrease of strength, an increase of plasticity and a decrease in the viscosity of solutions of the rubber are observed. The decrease in solubility and the increase of strength and elasticity set in at that stage of oxidation at which local links of ether type are formed between individual chains, or at which the accumulation of polar groups containing oxygen increases to a noticeable extent the intensity of intermolecular attractive forces. In the interaction of molecular oxygen with spatial (network) polymers, e.g., with the insoluble fraction of butadiene and butadiene-styrene polymers, with a solvent medium, there occurs a disintegration of structure and passage (dispersion) into the solvent medium. The solutions obtained contain massive particles of spherical form and display over a wide range of concentrations a Rayleigh type of light scattering and obedience to the law of Einstein and Poiseuille. The chemical nature of the dissolution of spatial polymers is confirmed by the magnitude of the activation energy of the process (27,000 calories per mole). A similar breakdown of spatial structures occurs in the milling of rubbers of this type, in which, in contrast to cases of mastication of linear polymers, the viscosity of solutions of spatial polymers does not change during the time of mastication. In the interaction of molecular oxygen with linear polymers containing double bonds in side chains, e.g., with sodium-butadiene rubber, the principal effect which takes place is the secondary process of combination of chains to spatial structures, resulting in the observation of a decrease of solubility, and an increase of strength and elastic properties of the polymer. This formation of spatial structures in the second stage of oxidation is facilitated by the polyfunctionality of the products of the initial stage of oxidation of the original polymer. The structural changes described, proceeding under the action of oxygen, constitute one of the causes of the appearance of the vulcanization optimum.

scholarly journals Disposition kinetics and dosage regimen of vitamin E administered intramuscularly to sheep

1991 ◽  
Vol 65 (3) ◽  
pp. 465-473 ◽  
Author(s):  
M. Hidiroglou ◽  
K. Karpinski
Keyword(s):  
Vitamin E ◽  
Elimination Rate ◽  
Live Weight ◽  
Tocopheryl Acetate ◽  
Lag Phase ◽  
Simple Relationship ◽  
Elimination Phase ◽  
Rate Of Absorption ◽  
The Mean ◽  
Kinetics Of

Three experiments were conducted to estimate the effects of single intramuscular (IM) administrations of vitamin E on blood plasma and tissue concentrations of α-tocopherol in sheep. In Expt 1, plasma kinetics of α-tocopherol in sheep (n 30) were investigated following IM administration of three doses (ten sheep/dose) of DL-α-tocopheryl acetate, (20, 40 and 60 mg/kg live weight). Plasma profiles of α-tocopherol consisted of a lag phase followed by an apparent first-order absorption and elimination phase. The rate of absorption and elimination, as well as the lag phase, were independent of the dose, but the extent of absorption was directly proportional to dose. In Expt 2 (eighteen experimental and five control sheep), the animals were injected as in Expt 1 and were killed at 0, 80 and 176 h. Increases in α-tocopherol levels in organs were much higher than in plasma. Some tissues such as liver, spleen, lung and adrenal appeared to exhibit rapid absorption and elimination phases. The amount absorbed was proportional to the dose administered. Other organs such as heart, kidney and pancreas had a slow elimination rate. In Expt 3, D-α-tocopherol was injected IM into ten sheep at either 604 mg or 1208 mg. The mean hepatic α-tocopherol concentrations in both groups rose rapidly and after 4 weeks of dosing its concentrations were higher than the predosing levels. The increase in hepatic tocopherol concentrations were higher following 1208 mg dosing than 604 mg D-α-tocopherol. No simple relationship existed between plasma and hepatic α-tocopherol concentrations. This suggests a difference in body mechanisms controlling vitamin E in blood and liver.

Application of Infrared Absorption Spectra to Studies of the Oxidation of Sodium-Butadiene Rubber

1951 ◽  
Vol 24 (3) ◽  
pp. 591-596
Author(s):  
B. Dogadkin ◽  
B. Kasatochkin ◽  
N. Klauzen ◽  
A. Smirnova
Keyword(s):  
Quantitative Analysis ◽  
Molecular Oxygen ◽  
Structural Changes ◽  
Chemical Properties ◽  
Butadiene Rubber ◽  
Physical And Chemical Properties ◽  
Reaction Products ◽  
Infrared Absorption Spectra ◽  
Physical And Chemical ◽  
And Chemical Properties

Abstract The reaction of rubber with molecular oxygen explains well the structural changes which take place in rubber during aging and during a number of important technological processes, such as plasticization and vulcanization. Furthermore, during vulcanization, in addition to its reaction with the vulcanizing agent, rubber also reacts with oxygen contained in the mixture. This may be one of the reasons for an optimum point of vulcanization. However, it is difficult to explain the changes of physical properties of rubber by simple union of oxygen, with formation of oxygen-bearing groups. To account for the changes observed, addition of a large quantity of oxygen would be necessary, whereas actually notable changes are brought about by the absorption of only 2–3 per cent of oxygen. To explain this, it must be assumed that oxygen causes structural changes in rubber and that these changes become evident when the percentage of oxygen in the reaction products is still negligible. In the case of sodium-butadiene rubber, as was shown by one of the authors, this reaction at any particular temperature causes an increase of strength and of elasticity, and a loss of solubility. The object of the present investigation was a qualitative and limited quantitative analysis of those groups which originate during oxidation and also an examination of the structures which determine the changes of the physical and chemical properties in the reaction of rubber with molecular oxygen.

Pengaruh penambahan natural rubber (NR), epoxidation natural rubber (ENR-46) dan chlorprene rubber (CR) pada sifat kompon termoplastik

2020 ◽  
Vol 26 (2) ◽  
pp. 62-69
Author(s):  
Farida Ali ◽  
Tuti I. Sari ◽  
Andi A. Siahaan ◽  
Al-Kautsar D. Arya ◽  
Tri Susanto
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Vinyl Chloride ◽  
Butadiene Rubber ◽  
Elongation At Break ◽  
Nitrile Butadiene Rubber ◽  
Poly Vinyl Chloride

Penelitian ini untuk mengetahui pengaruh penambahan Natural Rubber (NR) dan Epoxidation Natural Rubber (ENR-46) dengan kompatibiliser Chlorprene Rubber (CR) pada aplikasi kompon termoplastik Poly Vinyl Chloride (PVC) dan Nitrile Butadiene Rubber (NBR), variabel penelitian meliputi ENR-46/PVC/NBR/CR, NR/PVC/NBR/CR dan CR-NR/PVC/NBR, CR-ENR-46/PVC/NBR. Parameter pengujian sifat fisik-mekanik : Hardness (Shore A), Tensile Strength (Mpa), Elongation at Break (%) dan ketahanan terhadap pelarut minyak (n-Pentane, Toluene, Hexane dan Pertalite). Hasil penelitian didapatkan untuk sifat fisik-mekanik, semakin banyak penambahan NR Kekerasan kompon termoplastik akan menurun, Tensile Strength dan Elongation at Break kompon akan meningkat begitu juga dengan CR-NR. Tetapi berbanding terbalik hasilnya untuk ENR-46 dan CR-ENR-46. Pengujian Ketahanan terhadap pelarut minyak semakin banyak penambahan ENR-46 Ketahanan kompon termoplastik terhadap pelarut akan meningkat, hasil yang sama juga pada CR-ENR-46. Tetapi berbanding terbalik hasilnya dengan penambahan NR dan CR-NR pada kompon termoplastik.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Biofilm Structure – An Important and Neglected Parameter in Waste Water Treatment

1989 ◽  
Vol 21 (8-9) ◽  
pp. 805-814 ◽  
Author(s):  
F. R. Christensen ◽  
G. Holm Kristensen ◽  
J. la Cour Jansen
Keyword(s):  
Wastewater Treatment ◽  
Structural Changes ◽  
Waste Water Treatment ◽  
Experimental Investigations ◽  
Biofilm Reactors ◽  
Substrate Removal ◽  
Treatment Processes ◽  
Laboratory Reactor ◽  
Biofilm Structure ◽  
Kinetics Of

Experimental investigations on the kinetics of wastewater treatment processes in biofilms were performed in a laboratory reactor. Parallel with the kinetic experiments, the influence of the biofilm kinetics on the biofilm structure was studied at macroscopic and microscopic levels. The close interrelationship between biofilm kinetics and structural changes caused by the kinetics is illustrated by several examples. From the study, it is evident that the traditional modelling of wastewater treatment processes in biofilm reactors based on substrate removal kinetics alone will fail in many cases, due to the inevitable changes in the biofilm structure not taken into consideration. Therefore design rules for substrate removal in biofilms used for wastewater treatment must include correlations between the removal kinetics and the structure and development of the biological film.

scholarly journals Kinetics of 1- and 2-methylallyl + O2 reaction, investigated by photoionisation using synchrotron radiation

2021 ◽  
Author(s):  
Domenik Schleier ◽  
Engelbert Reusch ◽  
Marius Gerlach ◽  
Tobias Preitschopf ◽  
Deb Pratim Mukhopadhyay ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Reaction Kinetics ◽  
Molecular Oxygen ◽  
Light Source ◽  
Storage Ring ◽  
Vacuum Ultraviolet ◽  
Flow Tube ◽  
Tube Reactor ◽  
Swiss Light Source ◽  
Kinetics Of

The reaction kinetics of the isomers of the methylallyl radical with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring.

scholarly journals POS1018 IMPORTANCE OF LATERAL SPINE VIEW IN DXA BONE DENSITOMETRY IN PATIENTS WITH SPONDYLOARTHRITIS

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 776.3-777
Author(s):  
S. Miri ◽  
H. Ferjani ◽  
K. Maatallah ◽  
A. Kasraoui ◽  
D. Kaffel ◽  
...  
Keyword(s):  
Femoral Neck ◽  
Structural Changes ◽  
Age Of Onset ◽  
Posterior Part ◽  
Lateral View ◽  
Mineral Density ◽  
Lateral Spine ◽  
Male Predominance ◽  
T Score ◽  
The Mean

Background:Osteoporosis is an increasingly important health problem among patients with spondyloarthritis (SPA). The Measure of Bone Mineral Density BMD is routinely carried out in an anteroposterior (AP) view of the spine. However, the syndesmophytes, ligaments calcifications, and the posterior part of vertebrae affect AP scanning. A lateral spine view is a more sensitive tool in assessing bone loss in trabecular bone.Objectives:We aimed to evaluate the association between lateral lumbar DXA and syndesmophyte grading in patients with SPA.Methods:We conducted a retrospective study including 75 patients with SPA. Bone density of the hip and lumbar spine was measured with a GE Lunar Prodigy Advance Bone Densitometer equipment. All patients had lumbar lateral, AP, and proximal femur DXA scans. The T-score, which measures the difference between a patient’s BMD and young-normal subjects, was computed and age-matched.Results:The mean age of the patients was 36±11 years. Male predominance was noted with a sex ratio of 4.76. The mean BMI was 25±5 kg/m2. Eight percent were obese. Fifty-two percent had Vitamin D deficiency.Forty-eight percent of the patients had axial SPA, while 52% had axial and peripheral symptoms.The mean age of onset was 27±7 years. Fifty-two percent of the patients had high inflammatory biomarkers. The BASDAI, ASDAS-VS, and ASDAS-CRP mean levels were respectively: 3.5±2.4, 3.1±0.9, and 3±0.8. The mean BASRI and mass were respectively 8 + 4.8 and 16.4 + 19.4. Analyses of T-score values obtained over the femoral neck revealed osteoporosis in 18.7% of the cases and osteopenia in 32% of the cases. On the other hand, analyses of AP, spine views revealed osteoporosis in 25.3% and osteopenia in 45.3% of patients (p=0.028, r=0.254). We detected the highest percentage of osteoporosis in lateral lumbar view and T-scores matched more closely with femoral neck values; osteoporosis in 29.3%, and osteopenia in 22.7% of the patients (p<10-3, r=0.562). BMD measured in AP, and lateral views were in good agreement (p<10-3, p=0.592). Age was inversely but not significantly associated with BMD in lateral (p=0.442, r=-0.09), AP (p=0.319, r=-0.117) and femoral neck projections (p=0.179, r=-0.157). Femoral neck BMD was associated with the activity of SPA (ASDAS vs (p=0.027, r= -0.295), and the mobility limitation BASMI (p=0.032, r= -0.247). Coxitis, BASRI, or mSASS were independent of BMD.Conclusion:We conclude that spine lateral view in DXA accurately measures BMD exceeding the AP spine views and femoral neck values. Therefore, structural changes do not affect this measurementDisclosure of Interests:None declared.

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