Cis-Trans Isomerization of Natural Rubber under the Influence of Hydrogen Chloride or Ethylaluminum Dichloride

1960 ◽  
Vol 33 (4) ◽  
pp. 985-987 ◽  
Author(s):  
I. I. Boldyreva ◽  
B. A. Dolgoplosk ◽  
E. N. Kropacjeva ◽  
K. V. Nel'son
Keyword(s):  
Natural Rubber ◽  
Hydrogen Chloride ◽  
Benzene Solution ◽  
Polymer Chains ◽  
Trans Content ◽  
Aluminum Compounds ◽  
Cis And Trans ◽  
Chloride Activity ◽  
Made In

Abstract We have established earlier that organo-aluminum compounds, and titanium tetrachloride, bring about the isomerization of the cis-isoprene units in natural rubber into the trans. The isomerization process, as influenced by the above materials, proceeds at appreciable velocity even at room temperature. The present communication reports the results of investigating the cis-trans isomerism of natural rubber as influenced by hydrogen chloride and ethylaluminum dichloride. The isomerizing action of hydrogen chloride upon unsaturated acids and stilbene was dislosed earlier in a series of papers. We investigated the action of dry hydrogen chloride and ethylaluminum dichloride on benzene solutions of natural rubber under the conditions described earlier. Hydrogen chloride was introduced in the form of a saturated benzene solution. In investigating the hydrogen chloride activity, each polymer sample was examined for unsaturation, chlorine content of the polymer chains and microstructure. The latter was characterized with the aid of infrared absorption spectra. As in the previous report, quantitative determination of the cis and trans content was made in the 840 cm−1 region, where the intensity and contour are substantially dissimilar for natural rubber and guttapercha. Furthermore, an additional inspection was made qualitatively in other regions of the IR spectrum (1100–1150 cm−1 and 1300–1330 cm−1), the feasibility of utilizing the 1300–1330 cm−1 region having been reported in a recent publication by Golub, who investigated the isomerization of natural rubber and guttapercha under the influence of selenium at temperatures of 180–220°.

The Separation and Characterization of Graft Copolymers from Natural Rubber

1958 ◽  
Vol 31 (4) ◽  
pp. 819-828 ◽  
Author(s):  
F. M. Merret
Keyword(s):  
Natural Rubber ◽  
Intrinsic Viscosity ◽  
Benzene Solution ◽  
Graft Copolymers ◽  
General Pattern ◽  
The Other ◽  
Vinyl Monomers ◽  
Major Increase ◽  
Made In

Abstract The solubility of graft copolymers prepared from rubber and vinyl monomers follows a general pattern whereby one of the constituents can be insolubilized while the other remains soluble, the compound forming a stable sol which is largely unaffected by heat or ionic materials at suitable ratios of solvent to precipitant. The onset and flocculation of the sol are such that the graft copolymer can be completely separated from either free constituent homopolymer. This insolubilization of the rubber trunk chain by addition of methanol to a benzene solution of the coploymer has been followed by the changes in the intrinsic viscosity and turbidity, which show that the collapse of the rubber chain continues to a point beyond where the molecularly equivalent free rubber would be precipitated. This period also marks the major increase in turbidity. Osmotic data show that μ-values for the grafted copolymers of rubber are the same as for rubber itself, thus supporting similar assumptions made in the application of the theory of the equilibirium swelling of crosslinked rubber.

Cis-Trans Isomerization of Natural Rubber under the Influence of Organo-Aluminum Compounds and Titanium Tetrachloride

1959 ◽  
Vol 32 (4) ◽  
pp. 1036-1038 ◽  
Author(s):  
B. A. Dolgoplosk ◽  
E. N. Kropacheva ◽  
K. V. Nelson
Keyword(s):  
Natural Rubber ◽  
Ultraviolet Light ◽  
Titanium Tetrachloride ◽  
Chemical Properties ◽  
Regular Structure ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Aluminum Compounds ◽  
Physical And Chemical ◽  
First Time

Abstract Ziegler catalysts have become of prime importance for synthesis of polymers with regular structure, particularly cis-polyisoprene. The disruption of the structure of the chain by the formation of trans units was, until now, connected only with the influence of the physical and chemical properties of the catalyst on the nature of the addition of the diene monomers during the polymerization process. In the present work it is shown that destruction of regularity of structure can be caused by isomerization of cis units in complete polymer chains into trans units under the influence of the compounds used for initiating the polymerization process. Attempts to isomerize natural rubber by means of ultraviolet light and iodine did not give the expected effect. Ferri established for the first time that under the influence of zinc chloride and titanium tetrachloride natural rubber undergoes changes accompanied by disappearence of crystallization on stretching as shown by x-ray structure analysis. On the basis of these results the authors presumed that under the influence of these agents isomerization of cis units to trans units occurs in the natural rubber chain. The isomerization of cis-1,4 units to trans units in polybutadiene by means of ultraviolet light in the presence of organic bromine or sulfur compounds was first accomplished and proved by Golub. The formation of trans units in natural rubber under similar conditions was not observed. The study of the isomerizing effect of TiCl4 and organo-aluminum compounds was conducted by us on solutions of milled natural rubber (NK) in benzene in sealed glass ampoules. The benzene used was dried and distilled over sodium. All work was conducted in an atmosphere of dry argon. Unsaturation and microstructure of the chain was determined on each sample. The study of microstructure of polyisoprenes was carried out by means of infrared spectra, the relative content of the different configurations of the polymer chain being determined by the absorption in the 800–1000 cm−1 region. The method previously developed by one of us was used for this purpose.

Ozonolytic Degradation of Interpolymers of Natural Rubber with Methyl Methacrylate and Styrene

1958 ◽  
Vol 31 (1) ◽  
pp. 82-85
Author(s):  
D. Barnard
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Natural Rubber ◽  
Accurate Determination ◽  
Synthetic Polymers ◽  
Polymer Chains ◽  
Low Molecular Weight ◽  
Rubber Content ◽  
Tert Butyl Hydroperoxide

Abstract The preparation of graft and block interpolymers of natural rubber and synthetic polymers has made it desirable that the number and size of polymer chains attached to rubber be readily determinate. The degradation of unsaturated polymers with tert-butyl hydroperoxide in the presence of osmium tet oxide has been used for the determination of free polystyrene in SBR and carbon black in several elastomers, and has recently been applied to the present problem. The accurate determination of the rubber content of interpolymers by quantitative ozonolysis essentially according to the method of Boer and Kooyman suggested that this might be made the basis of isolation of the attached polymer, the rubber being degraded into fragments of low molecular weight, from which the polymer could be separated by conventional techniques. The method should be applicable to any interpolymer, or mixture, of a polyunsaturated and a saturated polymer and is illustrated with reference to interpolymers of natural rubber (NR)-polymethyl methacrylate (PMM) and NR-polystyrene (PS).

A thermocouple method of following the non-stationary state of chemical reactions V. The evaluation of velocity coefficients for the propagation and termination reactions for the heterogeneous polymerization of acrylonitrile

1961 ◽  
Vol 260 (1301) ◽  
pp. 205-217 ◽  
Keyword(s):  
Stationary State ◽  
Bulk Polymerization ◽  
Polymer Chains ◽  
Polymerization Reaction ◽  
Kinetic Chain ◽  
A Value ◽  
Thermocouple Method ◽  
The Difference ◽  
Made In

An attempt has been made to evaluate the velocity coefficients for the propagation and termination reactions in the bulk polymerization of acrylonitrile using the thermocouple non-stationary-state method. The reaction has been studied at 25 °C, and 1. 1'-azo-bis- cyclo -hexane carbonitrile has been employed as a photosensitizer. In the very early stages of the reaction (< 0.1 % conversion) when there is very little dead polymer present, the intensity exponent is 0.5, which indicates that the termination reaction proceeds by the interaction of growing polymer chains. The values obtained for the propagation and termination velocity coefficients (namely, 52 and 5.0 × 10 6 1. mole -1 s- 1, respectively) are lower than those reported in the literature for the polymerization of acrylonitrile in dimethylformamide solution. The difference has been attributed to environmental factors. Measurements of rates and lifetimes of the kinetic chain have also been made in the region of 1 to 7% conversion. By means of a suitably designed dilatometer which could be centrifuged, the effects of polyacrylonitrile on the polymerization reaction was studied. It was shown that the presence of polymer produced an enormous increase in the lifetime of the kinetic chain, while the rate decreased a little probably due to the scattering of initiating irradiation by the precipitated polymer. The intensity exponent appeared to increase to a value of 0.7, but this may not have been a true effect, as errors in the determination of the rate may have arisen due to difficulties in maintaining adiabatic conditions throughout the non-stationary state. The results in general are in keeping with the occlusion theory suggested by previous workers to explain some peculiar characteristics of the bulk polymerization of acrylonitrile.

Degradation of Highly Elastic Polymers. VI. The Intermittent Chemo-Stress Relaxation of Crosslinked 1,5-Polyenes

1970 ◽  
Vol 43 (4) ◽  
pp. 788-798
Author(s):  
K.-H. Hillmer ◽  
W. Scheele
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Oxidative Degradation ◽  
Sample Pretreatment ◽  
Relaxation Method ◽  
Relaxation Curve ◽  
Made In

Abstract Measurements of the continuous stress relaxation of thiuram vulcanizates and intermittent stress relaxation of both sulfur and C—C crosslinked vulcanizates of natural rubber were discussed. These measurements were made in the presence of either oxygen or nitrogen at various temperatures both with and without sample pretreatment. The following conclusions were drawn: 1. Determination of the rate of continuous tension loss is not suitable for measuring the oxidative degradation of vulcanizates from 1,5 polyenes according to a stress relaxation method. The reason for this is that rheological processes superimpose themselves on the chemical reactions initiated by oxygen, cause a reduction in tension, and affect both the form of the relaxation curve and also the rate of tension loss. This is particularly noticeable in the case of vulcanizates containing polysulfide bonds. 2. It was possible, using intermittent stress relaxation and by choosing suitable temperatures and frequencies, to eliminate the influence of rheological processes and thus to measure only the rate of tension loss due to oxidative degradation.

The quantitative comparison of experimental and simulated diffraction contrast images

1995 ◽  
Vol 53 ◽  
pp. 102-103
Author(s):  
Stuart McKernan
Keyword(s):  
Image Processing ◽  
Personal Computer ◽  
Close Agreement ◽  
Quantitative Comparison ◽  
Image Simulation ◽  
Computing Power ◽  
Diffraction Contrast ◽  
Simulated Images ◽  
Made In

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.

Science of Ahangyol and Its Importance for Modern Scientific Thought

2019 ◽  
Vol 10 (5) ◽  
pp. 473-478
Author(s):  
Ahmad Gashamoglu ◽  
Keyword(s):  
Modern Science ◽  
Scientific Basis ◽  
New Paradigm ◽  
Islamic Philosophy ◽  
Scientific Thought ◽  
Religious Books ◽  
Strategic Approach ◽  
Scientific Potential ◽  
Made In

The Article briefly discusses the need for generation of the Science of Ahangyol, and this science’s scientific basis, object and subject, category system, scientific research methods and application options. Ahangyol is a universal science and may be useful in any sphere. It may assist in problem solving in peacemaking process and in many areas such as ecology, economics, politics, culture, management and etc. This science stipulates that any activity and any decision made in the life may only and solely be successful when they comply with harmony principles more, which are the principles of existence and activity of the world. A right strategic approach of the Eastern Philosophy and the Middle Age Islamic Philosophy and scientific thought has an important potential. This strategic approach creates opportunities to also consider irrational factors in addition to rational ones comprehensively in scientific researches. The modern scientific thought contributes to implementation of these opportunities. Ahangyol is a science of determination of ways to achieve harmony in any sphere and of creation of special methods to make progress in these ways through assistance of the modern science. Methods of the System Theory, Mathematics, IT, Astronomy, Physics, Biology, Sociology, Statistics and etc. are more extensively applied. Information is given on some of these methods. Moreover, the Science of Ahangyol, which is a new philosophical worldview and a new paradigm contributes to clarification of metaphysic views considerably and discovery of the scientific potential of religious books.

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