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.

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.

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.

scholarly journals Entangling Lattice-Trapped Bosons with a Free Impurity: Impact on Stationary and Dynamical Properties

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 290
Author(s):  
Maxim Pyzh ◽  
Kevin Keiler ◽  
Simeon I. Mistakidis ◽  
Peter Schmelcher
Keyword(s):  
Structural Changes ◽  
Many Body ◽  
Wide Range ◽  
Entropy Measures ◽  
Particle Level ◽  
The Many ◽  
The One ◽  
Tunneling Dynamics ◽  
The Individual ◽  
Trapped Bosons

We address the interplay of few lattice trapped bosons interacting with an impurity atom in a box potential. For the ground state, a classification is performed based on the fidelity allowing to quantify the susceptibility of the composite system to structural changes due to the intercomponent coupling. We analyze the overall response at the many-body level and contrast it to the single-particle level. By inspecting different entropy measures we capture the degree of entanglement and intraspecies correlations for a wide range of intra- and intercomponent interactions and lattice depths. We also spatially resolve the imprint of the entanglement on the one- and two-body density distributions showcasing that it accelerates the phase separation process or acts against spatial localization for repulsive and attractive intercomponent interactions, respectively. The many-body effects on the tunneling dynamics of the individual components, resulting from their counterflow, are also discussed. The tunneling period of the impurity is very sensitive to the value of the impurity-medium coupling due to its effective dressing by the few-body medium. Our work provides implications for engineering localized structures in correlated impurity settings using species selective optical potentials.

scholarly journals Analysis of the Impact on the Mechanical Properties of Modification of Oligohydroxyethers in Organic Solvent Solution with Rubbers

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 519
Author(s):  
Vitalii Bezgin ◽  
Agata Dudek ◽  
Adam Gnatowski
Keyword(s):  
Mechanical Properties ◽  
Scientific Paper ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Molecular Weights ◽  
Wide Range ◽  
Strength Tests ◽  
Materials Used ◽  
Styrene Butadiene ◽  
The Impact

This paper proposes and presents the chemical modification of linear hydroxyethers (LHE) with different molecular weights (380, 640, and 1830 g/mol) with the addition of three types of rubbers (polysulfide rubber (PSR), polychloroprene rubber (PCR), and styrene-butadiene rubber (SBR)). The main purpose of choosing this type of modification and the materials used was the possibility to use it in industrial settings. The modification process was conducted for a very wide range of modifier additions (rubber) per 100 g LHE. The materials obtained in the study were subjected to strength tests in order to determine the effect of the modification on functional properties. Mechanical properties of the modified materials were improved after the application of the modifier (rubber) to polyhydroxyether (up to certain modifier content). The most favorable changes in the tested materials were registered in the modification of LHE-1830 with PSR. In the case of LHE-380 and LHE-640 modified in cyclohexanol (CH) and chloroform (CF) solutions, an increase in the values of the tested properties was also obtained, but to a lesser extent than for LHE-1830. The largest changes were registered for LHE-1830 with PSR in CH solution: from 12.1 to 15.3 MPa for compressive strength tests, from 0.8 to 1.5 MPa for tensile testing, from 0.8 to 14.7 MPa for shear strength, and from 1% to 6.5% for the maximum elongation. The analysis of the available literature showed that the modification proposed by the authors has not yet been presented in any previous scientific paper.

scholarly journals Ligand-induced structural changes analysis of ribose-binding protein as studied by molecular dynamics simulations

2021 ◽  
pp. 1-12
Author(s):  
Haiyan Li ◽  
Zanxia Cao ◽  
Guodong Hu ◽  
Liling Zhao ◽  
Chunling Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Changes ◽  
Binding Protein ◽  
Network Models ◽  
Md Simulations ◽  
Protein Domain ◽  
Opening Angle ◽  
Conformation Changes ◽  
Wide Range ◽  
Ribose Binding Protein

BACKGROUND: The ribose-binding protein (RBP) from Escherichia coli is one of the representative structures of periplasmic binding proteins. Binding of ribose at the cleft between two domains causes a conformational change corresponding to a closure of two domains around the ligand. The RBP has been crystallized in the open and closed conformations. OBJECTIVE: With the complex trajectory as a control, our goal was to study the conformation changes induced by the detachment of the ligand, and the results have been revealed from two computational tools, MD simulations and elastic network models. METHODS: Molecular dynamics (MD) simulations were performed to study the conformation changes of RBP starting from the open-apo, closed-holo and closed-apo conformations. RESULTS: The evolution of the domain opening angle θ clearly indicates large structural changes. The simulations indicate that the closed states in the absence of ribose are inclined to transition to the open states and that ribose-free RBP exists in a wide range of conformations. The first three dominant principal motions derived from the closed-apo trajectories, consisting of rotating, bending and twisting motions, account for the major rearrangement of the domains from the closed to the open conformation. CONCLUSIONS: The motions showed a strong one-to-one correspondence with the slowest modes from our previous study of RBP with the anisotropic network model (ANM). The results obtained for RBP contribute to the generalization of robustness for protein domain motion studies using either the ANM or PCA for trajectories obtained from MD.

scholarly journals Overview of Popular Techniques of Raman Spectroscopy and Their Potential in the Study of Plant Tissues

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1537
Author(s):  
Aneta Saletnik ◽  
Bogdan Saletnik ◽  
Czesław Puchalski
Keyword(s):  
Raman Spectroscopy ◽  
Cell Walls ◽  
Structural Changes ◽  
Spatial Information ◽  
Technological Development ◽  
Analytical Techniques ◽  
High Sensitivity ◽  
Plant Tissues ◽  
Wide Range ◽  
Identification Technique

Raman spectroscopy is one of the main analytical techniques used in optical metrology. It is a vibration, marker-free technique that provides insight into the structure and composition of tissues and cells at the molecular level. Raman spectroscopy is an outstanding material identification technique. It provides spatial information of vibrations from complex biological samples which renders it a very accurate tool for the analysis of highly complex plant tissues. Raman spectra can be used as a fingerprint tool for a very wide range of compounds. Raman spectroscopy enables all the polymers that build the cell walls of plants to be tracked simultaneously; it facilitates the analysis of both the molecular composition and the molecular structure of cell walls. Due to its high sensitivity to even minute structural changes, this method is used for comparative tests. The introduction of new and improved Raman techniques by scientists as well as the constant technological development of the apparatus has resulted in an increased importance of Raman spectroscopy in the discovery and defining of tissues and the processes taking place in them.

scholarly journals Combining experimental and simulation data of molecular processes via augmented Markov models

2017 ◽  
Vol 114 (31) ◽  
pp. 8265-8270 ◽  
Author(s):  
Simon Olsson ◽  
Hao Wu ◽  
Fabian Paul ◽  
Cecilia Clementi ◽  
Frank Noé
Keyword(s):  
Force Field ◽  
Structural Changes ◽  
Markov Models ◽  
Force Fields ◽  
Divide And Conquer ◽  
Simulation Data ◽  
Wide Range ◽  
Simulation And Experiment ◽  
Kinetics Of

Accurate mechanistic description of structural changes in biomolecules is an increasingly important topic in structural and chemical biology. Markov models have emerged as a powerful way to approximate the molecular kinetics of large biomolecules while keeping full structural resolution in a divide-and-conquer fashion. However, the accuracy of these models is limited by that of the force fields used to generate the underlying molecular dynamics (MD) simulation data. Whereas the quality of classical MD force fields has improved significantly in recent years, remaining errors in the Boltzmann weights are still on the order of a few kT, which may lead to significant discrepancies when comparing to experimentally measured rates or state populations. Here we take the view that simulations using a sufficiently good force-field sample conformations that are valid but have inaccurate weights, yet these weights may be made accurate by incorporating experimental data a posteriori. To do so, we propose augmented Markov models (AMMs), an approach that combines concepts from probability theory and information theory to consistently treat systematic force-field error and statistical errors in simulation and experiment. Our results demonstrate that AMMs can reconcile conflicting results for protein mechanisms obtained by different force fields and correct for a wide range of stationary and dynamical observables even when only equilibrium measurements are incorporated into the estimation process. This approach constitutes a unique avenue to combine experiment and computation into integrative models of biomolecular structure and dynamics.

Study of Properties of Expanded Graphite – Polymer Porous Composite by Acoustic Emission Method

2013 ◽  
Vol 58 (4) ◽  
pp. 1331-1336 ◽  
Author(s):  
J. Berdowski ◽  
S. Berdowska ◽  
F. Aubry
Keyword(s):  
Acoustic Emission ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Physical And Mechanical Properties ◽  
Expanded Graphite ◽  
Composite Membranes ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Graphite Composite ◽  
Wide Range

Abstract The purpose of this paper was to investigate the physical and mechanical properties of compressed expanded graphite (CEG) and their porous derivatives after impregnation, polymerization; and carbonization by the use of acoustic emission method (AE). The mechanical and structural characteristics of compressed expanded graphite and their three groups of porous composites after each technological process are presented and discussed. The measurements of acoustic emission parameters in these materials were carried out at wide range of frequency of the waves (0.1÷2.5 MHz). The changes of two of parameters: - AE pulses counts rate and spectrum distribution of AE waves - are presented in this paper. The analysis of the respective parameters AE also gives possibility to determine the micro- and macro structural changes of materials at different levels of technological processes. Applications of these materials as catalysts with high specific surface make them very interesting subject of study. Also compressed expanded graphite composite membranes prepared from furfuryl alcohol polymers are promising for gas separation.

SHELL DEFORMATION AND SPIN EFFECTS IN NUCLEON SEPARATION ENERGIES

1993 ◽  
Vol 02 (04) ◽  
pp. 789-807
Author(s):  
D. CALEB CHANTHI RAJ ◽  
M. RAJASEKARAN ◽  
R. PREMANAND
Keyword(s):  
Structural Changes ◽  
Shell Correction ◽  
Separation Energy ◽  
Systematic Analysis ◽  
Spin Effects ◽  
Wide Range ◽  
Type Calculation ◽  
Nucleon Separation Energy ◽  
New Formula ◽  
Good Agreement

A new formula to obtain shell correction to separation energy is derived from a Strutinsky type calculation. A systematic analysis of shell and deformation effects on nucleon separation energy is made. Spin induced structural changes are also evident in shape changes along the spin coordinate. Calculations are performed for a wide range of nuclei from Zr to Cm. The results are generally in very good agreement with experimental analysis.

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