bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Compatibility as a Factor in the Dispersion of Fillers in Rubber
Authors: Carlton C. A. 
Published: February 2011

Abstract
Poor dispersion of fillers in rubber compounds has been a troublesome problem since the beginning of the rubber industry. An example of this kind of difficulty is the presence of white pigment lumps in black or dark-colored compounds that are surface buffed, such as some types of shoe soling. Chemical analyses of filler agglomerates removed from a large number of unvulcanized and vulcanized rubber compounds revealed the fact that in practically every instance a substantial amount of zinc oxide was present. This is of major importance since good dispersion of zinc oxide is necessary for the proper vulcanization of a rubber compound. It is quite difficult to identify positively the specific variable or variables in any one given formulation which may cause filler agglomerates. They may be due to the composition of one or more of the ingredients present in the mix, the order in which the ingredients are added, or to the mixing procedure. However, a series of tests indicated one major cause, the addition of acidic materials such as fatty acids, organic acid vulcanization retarders, or acidic accelerators to natural rubber or some synthetic rubbers simultaneously with basic activators such as lime, litharge, magnesia, and zinc oxide, or with some basic fillers such as finely divided calcium and magnesium carbonates. High-temperature mixing (about 325° F) gave better dispersion than low-temperature mixing (about 220° F) when acidic or basic materials were added simultaneously, but in some instances poor dispersion resulted even at temperatures up to 325° F. This was particularly true of litharge and magnesia. It was also found that when zinc oxide and stearic acid were added to synthetic rubber at the same time, dispersion was better in some types of rubber than in others. The stiffer mixes of NBR (nitrile) and cold, unfilled SBR gave better dispersions than those of the softer IIR (butyl) and oil-extended SBR. Regardless of the type of rubber being used, the safest procedure to insure satisfactory dispersion of inorganic oxides is to add any acidic materials separately during the mixing procedure. This approach is particularly necessary if the mix contains resin acids and/or organic acid vulcanization retarders such as benzoic or salicylic acids. If it is not feasible to add the acidic and basic compounding materials separately to the rubber, then the inorganic oxides should be added to the mix in the form of masterbatches.
The Strain Dependence of Rubber Viscoelasticity. III. Natural and Butyl Rubber at High Extensions
Authors: Mason P. 
Published: February 2011

Abstract
In previous papers in this series the linear viscoelastic behavior of gum and filled rubbers has been studied at mean extensions up to 100%. Linearity was assured by allowing each specimen to relax at the required extension to its equilibrium state and then measuring the complex Young's modulus for very small strains superimposed upon this equilibrium extension. Analysis of the data was made either in terms of a Mooney strain-energy function or, more generally, by relation to the experimentally determined equilibrium stress-strain curve of the material. At much higher strains, however, the use of a strain-energy function is invalidated by the hysteretic behavior of the rubber, and the determination of a stress-strain curve at anything resembling equilibrium becomes increasingly difficult. Consequently, in the region of high strain it is preferable to examine the strain dependence of the viscoelasticity without involving a direct comparison with the equilibrium behavior. In principle, the most significant analysis would be obtained from a study of the strain dependence of the relaxation or retardation spectrum. The long-time end of the spectrum could perhaps be measured using a refined creep or stress relaxation technique, although considerable care would be required to separate the effects from the residual behavior resulting from the initial large elongation. In the rubber-glass transition region, with which this work is primarily concerned, the difficulty lies in making measurements over a sufficiently wide frequency range. Normally the Williams—Landel—Ferry (WLF) equation would be used to transform constant-frequency data from a wide temperature range to the equivalent isothermal spectrum over a wide frequency range; however, the validity of this equation has been confirmed only for amorphous polymers, and its application to highly stretched, anisotropic rubber involves several untested assumptions as discussed further below. The main object of the present paper is to describe the observed variations in the viscoelasticity of natural and butyl rubber over a wide range of extension and temperature, although, of necessity, over a limited range of frequency. In addition, a tentative indication of the influence of strain upon the relaxation spectra is given, and the implications of this are examined.
An Interpretation of the Mechanical Properties of Covered-Rubber Yarns
Authors: Treloar L. R. G. 
Published: February 2011

Abstract
The extensibility and other mechanical properties of covered-rubber yarns are considered on the basis of a simple theoretical model in which the covering thread is assumed to be inextensible. It is shown that certain characteristic properties of these yarns are essentially determined by the helix angle during the covering process. The tension in the covering thread and the stresses on the rubber at any state of strain are calculated. The theory is tested by experiments on a series of yarns whose geometrical parameters are systematically varied. The retraction subsequent to the covering process is found to be related to the helix angle of the covering in the manner predicted. The principal features of the force-extension curves are interpreted quantitatively on the same basis. Measurements of the couple about the axis, for singly-covered yarns, provide an indirect check on the theoretical analysis of the tension in the covering thread. It is shown that over a considerable range of extension the coverings are slack, the stress on the yarn being simply the stress on the rubber core. As the breaking point is approached, the fraction of the stress carried by the coverings becomes increasingly important, ultimately reaching a value exceeding 90 per cent of the total tensile force on the yarn in a typical yarn construction. It follows that the rubber core makes no significant contribution to the strength of the yarn, which is determined almost entirely by the strength of the coverings.
Tire Wear at Controlled Slip
Authors: Grosch K. A. , Schallamach A. 
Published: February 2011

Abstract
Tire wear at controlled slip, as realized by setting the wheels of a trailer at a slip angle, obeys the theoretically predicted square law dependence on the slip angle if allowance is made for the effect of temperature and abrasion patterns on the abrasion resistance of the tread compound. The temperature of the tire surface and the intensity of the abrasion patterns increase with increasing slip angle; the severity dependence of the relative wear rating of any two types of tire is largely due to differences in temperature and abrasion pattern coefficients. This applies also to wear on wet roads. The order of magnitude of the absolute wear rates agrees well with the values calculated from the abrasion resistance of tread compounds and the mechanical properties of the tire.
2-Mercaptothiazole and Derivatives as Vulcanization Accelerators
Authors: Trivette C. D. , Morita E. , Young E. J. 
Published: February 2011

Abstract
In this paper the subject of rubber vulcanization accelerated by 2-mercapto-benzothiazole and its derivatives has been reviewed. The technical literature from 1945 through 1960 and patents from 1932 through 1960 have been covered. Topics include: methods of synthesis and manufacture of these accelerators; application and compounding data on their use in rubber processing; and studies of the modes of action and mechanisms for the chemical reactions involved during accelerated vulcanization. Much disagreement exists concerning the mechanism of accelerated vulcanization and the action of thiazole accelerators. However, most of the conflict lies not in the experimental data collected, but in the interpretation of the meaning of the data. It is well documented that MBT and activators (zinc stearate, or zinc oxide and stearic acid) undergo an initial reaction; that these reaction products then react with sulfur and/or rubber hydrocarbon to form intermediate compounds; and that these intermediates then react in some manner to form sulfur crosslinks. Not known, for the most part, are the precise reaction steps involved; the sequence in which these reactions occur; the individual mechanisms, whether ionic, free radical, or neither, by which these reactions proceed; and the side reactions involved, if any (except in natural rubber, in which the non-crosslink forming cyclization reaction is well documented) which might lead to erroneous conclusions from the experimental data, particularly from kinetic studies. These same conclusions apply in general to thiazole sulfenamide accelerated sulfur vulcanization, with the exception that, in contrast to MBT, which has a free thiol group available for immediate reaction, the sulfenamide must first decompose or react in some manner before acceleration occurs. Sulfur and divalent sulfur compounds readily undergo both radical and ionic reactions, depending only on co-reactants and reaction conditions. At present, the reactions of sulfur with hydrocarbons and accelerators are not sufficiently well understood to draw concrete conclusions about the mechanism of acceleration. Further progress on elucidation of the mechanism will come with a better knowledge of the chemistry and mechanisms of sulfur reactions.
Approximate Analysis of the Stressed State of Rubber Specimens, Tear Tested by Various Methods
Authors: Lukomskaya A. I. 
Published: February 2011

Abstract
This paper describes analyses made of the stress and strain changes in the 3 standard ASTM tear specimens and a GOST 270-53 specimen up to the time of tearing. Using the nonlinear theory of elasticity the stresses are calculated and show reasonable agreement with ultimate tensile strength figures. The results refer to natural, sodium-butadiene and styrene-butadiene rubbers.
Dien Rubber: Compounding and Testing
Authors: Smith Ward A. , Willis James M. 
Published: February 2011

Abstract
Over 2,000,000 miles of testing on tires containing Diene rubber in blends with natural rubber or SBR show conclusively the advantages of using these stocks. Important improvements in abrasion and cracking resistance, operating temperature, rolling resistance and gasoline consumption, and traction on snow should be mentioned. At the present time, all of the Diene rubber being manufactured in a pilot plant is being utilized in production of tire stocks. It is certain that this usage will be greatly expanded in the near future when the full scale plant goes on stream.
Structure of the Spongy Polymer of Isoprene
Authors: Spasskova A. I. , Rabinovitch D. I. 
Published: February 2011

Abstract
1. The spongy polymer of isoprene was subjected to ozonolysis and 63.7% of the carbon chain was shown to be linked —1,4—1,4—. 2. Acetic and succinic acids were observed as secondary breakdown products of these —1,4—1,4— chains and they amounted to about 14.5% of the carbon skeleton of the spongy polyisoprene.
Mechanochemical Transformation and Synthesis of Polymers
Authors: Berlin A. A. 
Published: February 2011

Abstract
The mechanical grinding, milling, mixing, homogenization, freezing and other processes of the physico-mechanical processing of high polymers are widely used in the industries of plastics, rubbers, synthetic fibers, food products, silicates and many other branches of technology. Some of these processes have a great significance in biochemistry, medicine and biology. An analysis of the available experimental data permits one to reach the conclusion that in the intensive grinding of natural polymers (cellulose, starch, proteins or synthetics (polystyrene, rubber, polyisobutylene, etc.) a mechanical scission (cracking) of the macromolecules is observed. The possibility of macromoleeular scission under the grinding of high molecular weight substances is due to the high probability of a localization of mechanical energy at different sections of the polymer chain, which under certain conditions causes internal stresses exceeding the strength of covalent or ionic bonds. Mechanical breakdown of macromolecules is possible not only with dry or wet grinding, but also by mechanical action on polymer solutions. Thus, for instance, Staudinger has shown that the high speeds and forces of friction developed in forcing a 0.005 molar tetralin solution of polystyrene, average molecular weight = Mave=6⋅106, through a platinum capillary bring about a scission of the macromolecules which is revealed in a decrease of about 30% in the specific viscosity of the solution. Forcing a solution of polyisobutylene (Mave=3.9×104–23×104) in dichlorobenzene through a capillary with a diameter of 0.2 mm causes a decrease in the intrinsic viscosity and an increase in the constant of the Huggins equation. An increase in the Mave of the polymer structure formation (cross-linking) and a repeated forcing through is conducive to the mechanical breakdown of the macromolecules. It has been established that in mixing together solutions of polymeric substances (starch, gelatine, polyvinyl alcohol, etc.) with high-speed mixers having a rotation speed of over 4000 rpm, a sharp decrease in the intrinsic viscosity [ν] is observed, while the degree of scission increases, with an increase in the rotation speed of the mixer, and also with a decrease in the concentration of the solution.
Determination of Degree of Crosslinking in Natural Rubber Vulcanizates. Part III
Authors: Mullins L. 
Published: February 2011

Abstract
The two previous parts of this series described an attempt to relate the physical properties of natural rubber vulcanizates to their network structure. The first established an empirical relationship between the stress-strain behavior of highly swollen natural rubbers in simple extension, and their equilibrium volume swelling in n-decane. It also examined the effect of changes in initial molecular weight of the unvulcanized masticated rubber on these properties, and an empirical correction making allowance for network flaws due to chain-segments terminated by a crosslink at only one end was obtained. The second part gave measurements of the equilibrium volume swelling and the intrinsic viscosity before vulcanization for each of a range of natural rubber vulcanizates which had been prepared by a method which enabled the number of crosslinks to be determined by chemical analysis. These measurements permitted a comparison to be made between (i) the chemical estimate of the actual number of crosslinks introduced and (ii) the number derived from the data on equilibrium volume swelling, by means of the empirical relations derived in Part I. For this purpose, an assumption was made that the stress-strain behavior of highly swollen rubbers was in accord with the predictions of the statistical theory. Recent studies of both the stress-strain properties of highly swollen rubbers and the method of determining number-averaged molecular weight from intrinsic viscosity measurements have provided an improved basis for the quantitative determination of the degree of crosslinking from measurements of physical properties. The results described in Parts I and II of this series are reinterpreted here to take account of both of these developments ; in addition, the effect of the introduction of a correction for a network defect equivalent to chain entanglements is examined.
Electron Spin Resonance Study of the Interaction of Tetramethylthiuram Disulphide (TMTD) with Rubber and Related Compounds
Authors: Bresler S. E. , Dogadkin B. A. , Kazbekov E. N. , Saminskii˘ E. M. , Shershnev V. A. 
Published: February 2011

Abstract
In the article by Dogadkin and Shershnev electron paramagnetic resonance spectra produced in the laboratory of Prof. S. E. Bresler are put forward to confirm the radical mechanism of the interaction of TMTD with raw rubber in the process of vulcanization. After this paper had been printed we learned of the work of B. R. McGarvey and H. M. McConnel, in which analogous spectra were observed in solutions containing bivalent copper ions. As a result it is suggested that the electron paramagnetic resonance spectra of stocks of natural rubber with TMTD are affected by admixtures of copper compounds. The amount of copper calculated from the magnitude of the resonance spectrum amounts to 0.1% by weight in relation to the TMTD. The same spectrum is observed on heating a benzene solution of copper acetate and TMTD. Its intensity increases sharply and irreversibly on heating the solution to 100°. corresponding to 10% of the copper contained in the solution.
Some Aspects of High Temperature Vulcanization
Authors: Bielstein G. 
Published: February 2011

Abstract
When a thin rubber sample is heated to a high curing temperature, the initial kinetics of cure as derived from Newton's rule can be represented by a well-defined time delay at the final curing temperature. This facilitates quantitative studies for which it is also shown that first order changes in crosslink density can be assessed by modulus measurements. The vulcanization rate constants thus determined in the case of a polychloroprene compound indicate the apparently different action of the vulcanization accelerator at conventional and at high temperatures, which allows a fundamental interpretation to be advanced. Partial reversion at high temperature is shown for both the ACS1 and a thiuram-cured natural rubber compound, and using an appropriate graphical method, vulcanization and reversion can be evaluated as first order processes. Two simple overall reaction schemes are developed to fit the experimental data with only three calculated rate constants. Quinoid and peroxide curing systems are also examined.
Features of the Reinforcing Action of Carbon Blacks Deduced from the Tear Propagation of Filled Vulcanizates
Authors: Lukomskaya A. I. 
Published: February 2011

Abstract
1. The reinforcing action of carbon blacks is most clearly apparent in the knotty tearing of carbon black rubbers. 2. Knotty tearing is characteristic of rubbers filled with carbon black in definite ranges of deformation and temperature, the position of which depends upon the type of rubber and carbon black. 3. With high contents of contact gas black in vulcanizates of sodium butadiene (SKB) and butadiene sytrene (SKS-30) rubbers two ranges of knotty tearing occur. The first is situated at relatively high temperatures and low rates and the second at relatively low temperatures and higher rates. Reduction in the content of black in these vulcanizates leads to the disappearance of the high temperature range of knotty tearing and the displacement of the low-temperature range towards higher temperatures and low rates. This position of the ranges (at medium rates and temperatures) is characteristic also of the said synthetic rubbers containing thermal black. 4. The first range of knotty tearing of filled SKB and SKS-30 vulcanizates with contact black is linked with the presence in them of carbon black chains, while the second range, existing also with vulcanizates with thermal black, is connected with the presence of carbon black particles. 5. Within the ranges ofr ates from 40 to 1000 mm/min and of temperatures from 40 to +100° C filled vulcanizates of natural rubber have one range of knotty tearing situated at lower rates. In the case of the presence in them of contact gas black the range is shifted towards higher rates than in the case of thermal black. 6. Increasing the length of the nick in testpieces being tested for tear propagation leads to a shift in the range of knotty tearing towards higher rates and widens it with respect to temperatures. This same effect is noted on altering the shape of the testpiece, starting with the Delft testpieces and proceeding to types A, B, and C, i.e. increasing the nonuniformity of stress distribution in the deformed testpieces.
The Chemistry of Natural Rubber Production
Authors: Wren W. G. 
Published: February 2011

Abstract
Many advances in the world of science have taken place quietly in field and laboratory, with few to applaud the discoverer or to appreciate his worth. The man we honor today was such a pioneer, whose work received full recognition only many years after its completion. It is, I think you will agree, a very fitting tribute to Ridley to discuss recent advances in the science of natural rubber and to applaud at least some of the contributions made by the many different workers. The field is a large one, and I can hope only to give a brief survey of a few selected items, so I propose paying more attention to research which is concerned with the production of natural rubber rather than with its utilization.
The Structure of Various Natural Rubbers
Authors: Stavely F. W. , Biddison P. H. , Forster M. J. , Dawson H. G. , Binder John L. 
Published: February 2011

Abstract
Although Columbus, on his second journey to America, found the natives playing with balls which bounced and were elastic, it was almost 300 years later before use was made in Europe of the gum used in these balls. Priestley found that it could be used for erasing lead pencil marks. However, when further applications of this material were attempted, it became recognized that rubbers from different parts of the country differed. These differences arose partly from the botanical origin of the plants from which the gum, or rubber, was collected and partly from the methods of collecting and preparing it. With the passage of time, fine Para rubber came to be recognized and used as the best rubber and it held this position until it was supplanted by plantation rubber from Hevea brasiliensis trees. These differences in rubbers from different sources made it necessary for the user to know more about the material. Even the distinguished physicist Faraday became involved in the problem and in 1826 he published an analysis of the latex and also the dry rubber. His results were as follows :