bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in the Electrical Properties of Natural Rubber/Carbon Black Compounds during Vulcanization
Authors: Desanges H. , Chasset R. , Thirion P. 
Published: February 2011

Abstract
To conclude, let us sum up the advantages of direct current or low frequency measurement of the electrical properties of natural rubber compounds, when operating inside the mold in which vulcanization is occurring. In this way, it is possible to follow the changes in properties during heating or vulcanization more closely and accurately than when operating with samples outside the mold. An orientation of the colloidal structure of compounds above 10% by volume of MPC black is thus easily demonstrated. The dielectric properties of the compounds depend, in this case, on the size of the samples, since this orientation is a function of the dimensions, especially of the thickness of the molded compound. On the other hand, from the behavior of vulcanizable and nonvulcanizable compounds, a distinction may be made between the respective effects of both the vulcanization and the special state of agglomeration of the black colloidal particles in the compounds. This ‘structure’ of the black affects apparently both the losses and the dielectric constant through an electronic polarization phenomenon which can, in principle, be analyzed through the Maxwell-Wagner general theory of heterogeneous dielectrics. The effect of ‘structure’ on low-frequency losses depends essentially upon the nature and ratio of the black and varies like direct current conductivity. This ‘structure’ seems to be influenced also—although to a much smaller extent—by vulcanization, since the level of losses during heating is lower than with a nonvulcanizable compound containing the same ratio of black. When this ratio does not exceed 10% by volume, vulcanization governs the dielectric properties more directly, both by a fixation of polar sulfur to molecular chains, and by an ionic dissociation of vulcanizing ingredients. In the range of this study the only effect of molecular polarization is a rather limited increase of the dielectric constant; the losses are not affected. The sudden decrease of losses noted during the vulcanization of a gum compound is explained by a disappearance of the ions formed by the vulcanization reactions. This ionic polarization of the Maxwell-Wagner type plays no marked part in Compounds containing large amounts of black, no doubt because the ions are adsorbed by the black. By extending this study, as it is hoped, into the field of radio frequencies, it should be possible to improve the theory of the evolution of dielectric properties during vulcanization. From the practical point of view, such work would provide useful experimental data for a rational application of radio-vulcanization.
Filler-Rubber Interaction in Latex
Authors: Dogadkin B. A. , Senatorskaya L. G. , Guseva V. I. , Suslyakov A. V. , Zakharchenko P. I. 
Published: February 2011

Abstract
Conditions for the production of strong vulcanizates by direct addition of channel black to SKS-30 butadiene-styrene latex have been determined. Rubber reinforcement by carbon black in latex mixes occurs on addition of such substances as casein, gelatin, and alginic acid to the mixture. Experimental data are cited to show that the rubber reinforcement effect in the presence of the above substances is due to : a) their destabilizing action and the formation of structures in which the carbon black and rubber particles are in direct contact ; b) conditions in which the latex components are precipitated simultaneously (coprecipitation effect). Electrolytic coagulation of carbon black—latex mixtures results in increased vulcanizate strength. Vulcanization of filled latex compounds proceeds at a lower rate than that of ordinary rubber compounds of the same composition.
Modification of Rubber by Reaction with Maleic Anhydride
Authors: LeBras Jean , Pinazzi Christian , Milbert Gérard 
Published: February 2011

Abstract
The reaction between maleic anhydride and rubber has been studied in solution, by milling and by heating in the solid phase. However, as is most often the case with chemical derivatives of the rubber hydrocarbon, the operating conditions that were employed only yielded products exhibiting considerable impairment to the physical properties characteristic of rubber (especially its high elasticity) as a result of secondary reactions of scission, cyclization and crosslinking. It has subsequently been shown that it is possible, under certain conditions, to minimize these injurious effects, both in the case of the reaction in solution between natural rubber and maleic N-methylimide and in that of the reaction by milling between synthetic olefinic elastomers and maleic anhydride. Inspired by these studies, we have undertaken to re-examine, on more precise chemical bases, the reaction between the rubber hydrocarbon and maleic anhydride.
A Simple Extensometer for Tensile Testing of Polymers
Authors: Eagles A. E. , Payne A. R. 
Published: February 2011

Abstract
The prototype extensometer, which has now been in constant use for over a year, gives satisfactory results which compare favorably with those of the conventional method. The use of this extensometer, which is a simple mechanical device, robust and reliable in operation, removes the last obstacle from autographic recording of tests using dumbbell specimens, thus permitting a considerable increase in speed of tensile testing.
Evaluation of Rubber-Solvent Interaction
Authors: Shvarts A. G. 
Published: February 2011

Abstract
1. The influence of differences in the nature of the intermolecular forces in different solvents on their solvent powers has been examined. 2. A graphical method is proposed for evaluation of the influence of the nature of the intermolecular forces of the solvent on the maximum swelling of vulcanizates. 3. For a given rubber and a given chemical class of solvents, the relationship between δs and (μ−μs)òVs is linear. Lines for different classes of solvents intersect at one point which represents δr, the solubility parameter for the rubber.
Branching in Macromolecules of Different Synthetic Rubbers
Authors: Poddubnyĭ I. Ya , Ehrenburg E. G. 
Published: February 2011

Abstract
Branching in macromolecules of synthetic rubbers is one of their most important structural properties, exerting a pronounced influence on the physical behavior of these materials. The degree of branching evidently depends on the chemical nature of the free radicals or organometallic catalyst initiating the polymerization reaction. It also depends on the conditions of the reactions, particularly on the polymerization temperature, as the latter determines the relative rates of the propagation and branching reactions. The problem of developing a general quantitative method for the determination of branching in the molecules of high polymeric substances cannot yet be considered as solved. This problem appears to be very complicated and only a few experimental data are available. Therefore the development and application of methods with a sound physical background for the qualitative evaluation of branching have not lost their value. Most methods used for the determination of branching are based on the relations existing between the dimensions of molecular coils in solution and the degree of branching. Certain limitations of the methods commonly used for the determination of branching by values of Huggins' constant K′, the thermodynamic parameter μ, or the second virial coefficient arise from the fact that by such methods the above relation cannot be precisely accounted for. Therefore, in the present investigation, the degree of branching has been studied by viscosity measurements and also by determining the dynamo-optical properties of a polymer-fraction solution. The parameters found by this method, namely the dynamo-optical constant [Δn], obtained from the magnitude of the flow birefringence, the rotational friction coefficient, W, calculated from the orientation angles, as well as the intrinsic viscosity [η], all are determined by the dimensions of the molecular coils. By these methods, the investigation of the influence of the polymerization temperature on the branching for a number of synthetic rubbers obtained in the presence of different catalysts was carried out. Moreover, the intrinsic viscosity determinations made it possible, by the use of modern theories of polymer solutions, to estimate quantitatively branching in molecules of some synthetic rubbers.
Adhesion of High Polymers. 3. Effects of the Size, Shape, and Polarity on Adhesion to Cellophane
Authors: Voyutskiĭ S. S. , Shapovalova A. I. , Pisarenko A. P. 
Published: February 2011

Abstract
1. The method developed by the authors has been used to study the influence of size, form, and polarity of macromolecules on the adhesion of high polymers to cellophane. 2. Adhesion of high polymers to cellophane increases with decreasing molecular weight. However, for maximum bond strength, the cohesive properties of the polymer must also be taken into account. 3. Increase of the number of short side chains in the polymer molecule lowers its adhesion. 4. The adhesion of a polymer to cellophane decreases with increasing contents of polar groups in its macromolecules. 5. The results are explained on the basis of the diffusion theory of high polymer adhesion developed by the authors.
Radiation Crosslinking of Rubber—Effect of Additives
Authors: Turner D. T. 
Published: February 2011

Abstract
Rubber is one of the linear polymers which may be crosslinked by high energy radiation. In this paper the effect of a range of additives on the cross-linking of rubber by pile and gamma radiation is reported. Many were found to retard crosslinking and this is of interest mechanistically and as an example of protection against high energy radiation. A major problem in radiation chemistry is the relative importance of ions, excited molecules, and free radicals. An ionic mechanism has been suggested for the crosslinking of polyethylene and both excitation transfer and free radical hypotheses of protection have been suggested in the radiolysis of polymethyl methacrylate. The adequacy of a free radical mechanism may be assessed by comparison of protective power and radical acceptance and in this work most of the additives were chosen because of their known, or reasonably inferred, reactivity towards free radicals and, in particular, of polyisoprenyl radicals.
The Mechanism of Vulcanization in the Presence of 2-Mercaptobenzothiazole
Authors: Dogadkin B. A. , Tutorskiĭ I. A. , Pevzner D. M. 
Published: February 2011

Abstract
The mechanism of the action of one of the most widely used vulcanization accelerators, 2-mercaptobenzothiazole (MBT), has not been sufficiently investigated. It was demonstrated by Wistinghausen, and also Dogadkin and Pevzner (1951) that MBT is consumed during vulcanization, but the quantitative relationships involved in this reaction could not be established due to the lack of a method for determining the disappearance of the MBT. For the present study we made use of MBT labeled with the radioisotope S35 in the thiazole ring. The synthesis of MBT was carried out in the following manner. First, MBT labeled in both sulfur atoms, was prepared from phenly isothiocyanate and elementary S35. The MBT thus obtained was then heated in sealed ampules with excess ordinary sulfur at 140° for 6 hours. Under these conditions, the interchange reaction between the elementary sulfur and the sulfhydryl sulfur leads to an equilibrium. There was a twofold drop in the activity of the synthesized MBT. That is the way in which the labeling of the benzothiazole radical alone was accomplished, so that the radioisotope S35 introduced into the MBT molecule was not exchanged with elementary sulfur under the vulcanization conditions that obtained. This now made possible simultaneous measurements of the rate of sulfur addition and the rate with which the accelerator is added to the rubber.
The Chemistry of Vulcanization. II. Kinetics of Hydrgen Sulfide Evolution during the Reaction of Diphenylmethane and Sulfur
Authors: Tsurugi Jitsuo 
Published: February 2011

Abstract
In Part I, the products and mechanism of reaction between diphenylmethane and sulfur were reported. The reaction products at 180° C were hydrogen sulfide, benzhydryl polysulfide (PS) and thiobenzophenone (TBP). On the basis of this mechanism the theoretical rate equation is now derived and compared with experimental results.
Reaction between Diphenylmethane and 2,2′-Dibenzothiazolyl Disulfide
Authors: Tsurugi Jitsuo , Fukuda Haruko 
Published: February 2011

Abstract
At a lower temperature where no decomposition of the primary product occurred, the reaction mechanism is a radical chain reaction indicated by Equations (1) to (4). At 160° C one of the primary products, MSCHPh2, was decomposed to various secondary products by the radicals which were present in the reaction system. The decomposition mechanism is indicated by Equations (7) and (7′) and from (8) to (11).
The Separation and Characterization of Graft Copolymers from Natural Rubber
Authors: Merret F. M. 
Published: February 2011

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.
The Mechanism of Protection by the Deactivating Effect
Authors: le Bras Jean , Danjard Jean-Claude , Boucher Madeleine 
Published: February 2011

Abstract
In order to better understand the complex phenomena related to aging, the two following propositions should be considered : (a) Each type of vulcanizate has a particular type of network structure, with characteristics dependent on the number and nature of the crosslinks between the macromolecules. Thermo-oxidative degradation may have varying effects according to the network points which are preferentially attacked. (b) The protection at present employed against the consequences of this degradation is based upon two different mechanisms, i.e., through the antioxidant effect, which retards the scission reaction, or through the deactivating effect, which helps to maintain the network by forming additional crosslinks. If we also take into account the fact that each accelerator is able, as is the deactivator, to create specific new bonds by after-cure, we may suggest an explanation for some unexplained aspects of the related phenomena. From our results and the derived deductions ideas emerge, from which it should be possible to establish, by logic (instead of empirically) and by adaptation to each type of vulcanizate, some rules for the best protection with the present-known protective agents. It should be noted that all preceding observations refer exclusively to the most widely used industrial practice, sulfur curing. However, the knowledge we now have of the deactivating effect mechanism has led us to think that it should also be possible, for vulcanizates produced with other vulcanizing agents, to find substances which will play the same part as our present deactivators, although of a totally different chemical composition. As a matter of fact, the so-called deactivators are but slow-acting crosslinking agents, the new crosslinks resulting from either a mobilization of the unused vulcanizing agent in the vulcanizate or from a direct intervention of the deactivator. We therefore doubt whether their name, derived from the first, and inexact, explanation given for their action, is still justified. However, to change it we should have to evoke an after-crosslinking, a source of confusion with other current terms ; moreover, a number of other wrong terms have been confirmed by use, for instance, the English “antioxidant”. As these deactivators make degradation less active, their original name is perhaps not so inappropriate after all.
The Protection of Rubber against Atmospheric Ozone—Cracking
Authors: Biggs B. S. 
Published: February 2011

Abstract
The cracking of rubber by atmospheric ozone is now a well-known phenomenon and for a number of years rubber scientists and technologists have devoted considerable effort to combating it. While the differences of opinion and the confusion of data in this work are sometimes more conspicuous than the successes, nevertheless, there has been considerable success. In spite of the existence of large areas of uncertainty, much progress has been made. A new word, “antiozonant”, has been added to the vocabulary of the rubber man. The substances so designated, together with waxes already well known, enable the compounder to protect natural and synthetic rubbers against both static and dynamic exposure to a fair degree, and this in spite of the fact, now recognized, that certain urban atmospheres may contain much higher concentrations of ozone than were formerly considered normal. In addition, the synthetic polymer chemist has made available a number of commercial rubbers which, because they are saturated, are not at all vulnerable to ozone attack, and serve in many special applications in which extreme resistance to ozone is necessary. The purpose of this paper is to review the present status of the antiozone work.
The Determination of Free Sulfur in Accelerators
Authors: Hively R. A. , Wadelin C. W. 
Published: February 2011

Abstract
Since the amount of sulfur and accelerator added to a rubber stock affects the properties of the vulcanized stock, it is obviously desirable to know the amount of free sulfur in the accelerator. An isotopic dilution method by Ikeda and Kambara seems to be the only reference to work on this problem. The essential steps in their procedure are as follows: A known amount of radioactive sulfur of specific activity must be added to a weighed sample. Then a sufficient amount of free sulfur must be separated from the mixture in a very pure state so that it can be weighed and its activity measured. The method requires radio chemical equipment that might not be available. The modification of the polarographic procedure of Proske by Poulton and Tarrant is both sensitive and accurate for the determination of sulfur. Unfortunately, some of the sulfenamide accelerators interfere in the procedure. Other methods for the determination of sulfur include the reaction with sodium hydroxide, sodium sulfite mercury, potassium cyanide, silver, and triphenylphosphine. Schöberl et al., have shown that alkali hydroxides, sulfites and cyanides react with disulfide linkages. Triphenylphosphine disrupts some disulfide and sulfenamide linkages. Hydrogen sulfide and mercaptans combine with the metals. Adsorption chromatography of a benzene solution on alumina separates free sulfur (weakly adsorbed) from accelerators (more strongly retained). The polarograph offers a sensitive means for determination with some additional specificity of the separated components.
Vulcanization of Elastomers. 19. The Function of Oxides in Thiuram Vulcanization
Authors: Scheele Walter , Grasemann Horst , Mau Günter , Stange Peter 
Published: February 2011

Abstract
This article is a continuation of our discussion of the role of oxides in thiuram vulcanization. The following additional results were obtained: The reaction of TETD and ZnO gives off gaseous products and is pressure dependent. By taking this into account, both the conductometric and the spectrophotometric methods of analysis furnish identical results for the DEDC yields as a function of reaction times. The reaction of TETD with Bi2O3 produces in the presence or absence of NR (independent of the temperature) approximately 82 mole per cent BiDEDC based on the initial amount of TETD. However, no vulcanization takes place. The reaction between TETD and TeO2 produces in the presence or absenee of NR (independent of the temperature) a maximum yield of Te-II-DEDC of 60 to 70 mole per cent based on the initial amount of TETD. Such a yield of DEDC is also observed during a TETD vulcanization with ZnO. Nevertheless, no normal thiuram vulcanization takes place when TETD, TeO2 and NR are heated together. When Te-IV-DEDC is dissolved in various organic solvents, it undergoes disproportionation and equimolar amounts of Te-II-DEDC and TETD are formed. The limiting value of the Te-II-DEDC formation of 60 to 70 mole per cent during the reaction of TETD with TeO5 in the presence or absence of NR can be explained by a primary formation of Te-IV-DEDC in a maximum yield of 80 mole per cent followed by a disproportionation of the Te-IV-DEDC (the same as with a corresponding reaction in the presence of Bi2O3). Of course, it is assumed that the metal oxides during their reaction with TETD give maximum yields of 80 to 90 mole per cent DEDC based on the initial amount of TETD. Furthermore, the experiments showed that thiuram vulcanization obviously is due to the reaction of TETD with ZnO in which NR participates with formation of crosslinks. This concept is supported by the identical activation energies of the TETD decrease and DEDC increase during the reaction of ZnO with TETD in the presence and absence of NR.
Metal Oxides as Vulcanization Activators for Sodium Butadiene Rubber
Authors: Feldshteĭn M. , Orlovsky P. , Dogadkin B. 
Published: February 2011

Abstract
1. Differences have been found in the action of metallic oxides as vulcanization activators for sodium butadiene rubbers polymerized by the rod and rodless methods. 2. It was found that unloaded mixes based on rodless sodium butadiene rubber, containing accelerators of the thiazole and sulfenamide types, do not require the addition of metallic oxides as vulcanization activators. 3. It was shown that addition of zinc oxide to mixes based on rodless rubber with high alkali contents retards the vulcanization process.