bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotopic Exchange of Free Sulfur with Thiurams, Isothiocyanates and Dithiocarbamates
Authors: Kuzina L. S. , Guryanova E. N. 
Published: February 2011

Abstract
1. Studies were made concerning the exchangeability, with elementary radioactive sulfur, of sulfur atoms in 15 compounds including thiurams, dithiocarbamate and isothiocyanates. The number of exchangeable sulfur atoms in each material was established, as well as the optimal conditions for exchange, and for seven of the compounds the activation energy for the process was determined. The exchange rate of thiurams, with elementary sulfur, increases with the number of sulfur atoms in the polysulfide chain. In tetramethyl-thiuram tetrasulfide the two middle sulfur atoms are more readily exchanged, while the outer four sulfurs, bonded to carbon, are exchanged less rapidly but not sufficiently so to allow carrying out a separate exchange. 2. The velocity of exchange is significantly reduced in the thiuram disulfides when aliphatic radicals are replaced by phenyl radicals. A difference in the influence of amino-group radical variations was noted between the thiurams and the dithiocarbamates. The results of the isotopic exchange of sulfur in these materials have been considered from the viewpoint of their effectiveness as accelerators in the vulcanization of rubber.
The Chemistry of Vulcanization. VIII. Role of Zinc Butyrate in the Reaction of Diphenylmethane, Sulfur and 2-Benzothiazolyl Disulfide
Authors: Fukuda Haruko , Tsurugi Jitsuo 
Published: February 2011

Abstract
Diphenylmethane (DPM) which contains α-methylenic hydrogen has been used as a model of rubber hydrocarbon, and reactions involving DPM, sulfur and thiazole type accelerators in the absence of zinc oxide or soap were reported in previous papers. These papers reported that 2-mercaptobenzothiazole (MBT), 2-benzothiazolyl disulfide (MBTS) and zinc salt of 2-mercaptobenzothiazole (ZMBT) generate the same radical, i.e., 2-benzothiazolesulfenyl which has the accelerating effect. This radical opens the ring of elementary sulfur and thus accelerates vulcanization since the spontaneous splitting of the sulfur ring molecule to a biradical was found to be the rate determining step in the reaction of DPM with sulfur alone. Processes by which accelerators generate this radical differ from each other owing to the types of accelerators, that is, mercaptan, disulfide and zinc mercaptide type. The previous paper reported the reaction involving DPM, sulfur and MBT in the presence of zinc butyrate. According to this, MBT first reacts with zinc butyrate to form butyric acid and ZMBT, the latter then generating the effective benzothiazole-sulfenyl radical. Thus, even in the presence of zinc soap, the essential mechanism of acceleration is the same as in the absence of zinc soap, though the process and rate for forming benzothiazolesulfenyl radical are different in the absence of zinc soap. In the present paper the reaction of DPM, sulfur and MBTS in the presence of zinc butyrate are reported. The reaction mechanism will be deduced from the experimental results obtained here and from conclusions obtained in the previous papers. The rate equation for MBTS consumption and equation for the accelerating efficiency for this accelerator are derived from the mechanism. The theoretical equations were examined by experiments.
First and Second Order Transitions in Neoprene
Authors: Murray R. M. , Detenber J. D. 
Published: February 2011

Abstract
Neoprene vulcanizates crystallize most rapidly at —12° C. The temperature at which a vulcanizate is crystallized determines the minimum temperature at which it will thaw, the thaw point being approximately 15° C higher than the crystallization temperature over the range studied. Brittleness temperature is not changed as a result of crystallization. Crystallization resistance of the general purpose dry neoprene types increases in the following order: W, WB, WX, GN, GRT, WRT. Depending on the neoprene type, crystallization is retarded by a factor of 5 to 10 by vulcanization. Variation of filler type does not change crystallization rate appreciably. Crystallization rate is retarded through the use of sulfur, certain resinous type plasticizers, as well as by increased state of cure. Ester plasticizers which depress brittleness tempterature and reduce stiffening at low temperatures increase crystallization rate considerably and permit crystallization to occur at very low temperatures. Brittleness and 10,000 psi stiffness temperatures are not affected appreciably by neoprene type, state of cure, or amount and type of filler. Glass transition is approximately 12° C lower than the 10,000 psi stiffness temperature and 6° C lower than the brittleness temperature.
Thermal Expansion Measurements and Transition Temperatures. II. An Automatic Recording System
Authors: Dannis Mark L. 
Published: February 2011

Abstract
A differential expansion apparatus useful for studying first- and second-order transitions in polymeric materials was described1 in paper I. This apparatus utilizes a tipping mirror arrangement as part of an optical lever to magnify the expansion of the polymer sample with a change in temperature. Readings of light spot position on a scale and of sample temperature had to be taken almost continuously to obtain useful curves. These readings were very tedious and time-consuming, limiting the usefulness of the technique. Hence, an automatic recording system was developed, greatly expanding the potentialities of this kind of analysis.
Peroxide and Radiation Cured Compounds Filled with Reinforcing Fine Particle Silica
Authors: Sellers J. W. , Wagner M. P. , DeWitt B. J. , Stueber C. C. , Bachmann J. B. 
Published: February 2011

Abstract
The potential of fine particle silica to reinforce elastomers to an extent comparable with the most efficient furnace blacks has been indicated by the extent and nature of bound rubber formation. This potential has been confirmed in peroxide and radiation cures by the increase in crosslink density of the filled over the unfilled natural rubber mixtures. Confirmation in these curing systems stimulates further research designed to realize this high potential not fully attained in present sulfur cures.
Simple Rotary Dynamic Testing Machine
Authors: Gent A. N. 
Published: February 2011

Abstract
A test machine is described for determining the dynamic shear properties of rubberlike materials. It imposes a simple shear deformation, the direction of which is continuously rotated. The observations are easily made, and enable the dynamic shear modulus and damping factor to be determined rapidly; moreover, a relatively wide frequency range seems feasible. The instrument therefore appears suitable for general application. Measurements on a soft butyl rubber vulcanizate are described and compared with observations of free torsional oscillations. Good agreement is obtained. The testpiece is subjected to a rotating shear of constant amplitude, and hence the elastically-stored energy is held constant. The observed energy dissipation therefore confirms a hypothesis of Greenwood and Tabor, that dissipation may occur under such conditions, and indicates the limitations of the “hysteresis” concept that the dissipated energy is a constant fraction of the elastically-stored energy.
Acceleration by Thiourea and Related Compounds of the Tetramethylthiuram Disulfide Vulcanization of Natural Rubber
Authors: Moore C. G. , Saville B. , Watson A. A. 
Published: February 2011

Abstract
It has recently been discovered that thiourea and certain of its N-derivatives and chemically related compounds, accelerate the vulcanization of natural rubber (NR) by tetramethylthiuram disulfide (TMTD)-zinc oxide combinations to such an extent that excellent vulcanizates can be produced at 100° C or lower. A reasonable explanation of this acceleration is now offered, based on a theory of vulcanization by TMTI) and related “sulfurless” curing systems currently being developed here. This theory recognizes the importance of polysulfidic intermediates (I, m&gt;2), formed during the vulcanization process, which subsequently react with the polyisoprene to yield further intermediates (II) which finally react to yield sulfurated crosslinks. The process is broadly schematized as follows:
Standard Materials for Rubber Compounding
Authors: Roth Frank L. , Stiehler Robert D. 
Published: February 2011

Abstract
When the synthetic rubber plants began operation in 1943, the Government took steps to establish a system of quality control that would assure that the rubber produced in 16 plants had essentially the same properties and could be used interchangeably by the manufacturers of rubber products. The most important characteristic for quality control was the curing behavior of the rubber. The measurement of this behavior required mixing the rubber with compounding ingredients, vulcanizing the mixed compound for several periods of time, and measuring the tensile properties of the vulcanizates. Early interlaboratory tests led the Government to an extensive standardization program in order to achieve the necessary quality control of production. In this program, it became obvious that the compounding ingredients as well as the methods of mixing, curing, and testing required standardization. Therefore, in 1944, the Rubber Reserve Co. established standard compounding ingredients for testing synthetic rubbers. The first standards were commercial lots set aside and distributed by their suppliers, and consisted of five materials. By 1946 a total of 14 standards had been established. The Office of Rubber Reserve soon recognized that the establishment of suitable standards was a difficult technical problem and called on the National Bureau of Standards for assistance. Finally, in 1948 this Office requested NBS to assume responsibility for these standards. Shortly thereafter, ASTM Committee D-11 appointed a special subcommittee on standard materials, the forerunner of Subcommittee 29 on Compounding Ingredients. This Subcommittee requested the establishment of about 20 standard compounding materials which included the standards required for the synthetic rubber program. The National Bureau of Standards has now available 17 of these materials, including three standard rubbers.
Volatilization of Phenyl-2-Naphthylamine from Rubber
Authors: Angert L. G. , Zenchenko A. I. , Kuzminskiĭ A. S. 
Published: February 2011

Abstract
1. The rate of volatilization of phenyl-2-naphthylamine from a rubber slab depends on the flow rate of gas over the slab, the slab thickness, and the initial concentration of the ingredient. The activation energy of the volatilization process is 14.0 kcal/mole. 2. The rate of volatilization of phenyl-2-naphthylamine diminishes in the following polymer series: polyethylene &gt; fluoroprene rubber &gt; SKB &gt; SKS-30 &gt; SKN-26 &gt; Nairit. 3. The volatilization rate drops sharply with increase of the density of the vulcanization network, and decreases in presence of fillers. 4. The mechanism postulated for volatilization of ingredients from polymers is confirmed by theoretical calculations.
Oxidative Stress Relaxation Studies of Radiation Cured Vulcanizates, with and without Antioxidant
Authors: Dunn J. R. 
Published: February 2011

Abstract
Turner has shown that irradiation of natural rubber results in the formation of carbon to carbon crosslinks by combination of allylic radicals; the same type of crosslinks are formed by heating rubber in presence of organic peroxides2. Since peroxide vulcanizates may be freed from excess vulcanizing ingredients and by products by extraction while radiation crosslinking may be effected without additive, it is expected that the two types of vulcanizate should age in an analogous manner. The present study was undertaken in order to see whether radiation vulcanizates did show the same aging behavior as peroxide vulcanizates according to measurements of oxidative stress relaxation, and, if so, to ascertain whether the efficiency of antioxidants of the dithiocarbamate type was affected by the irradiation and whether such materials had an adverse effect upon cure. It has been stated that radiation vulcanizates are resistant to aging even in the absence of antioxidant and their stability has been attributed to the presence of purely carbon-carbon crosslinks. However, it has recently been demonstrated that a carbon-carbon crosslink is not a sufficient condition for vulcanizate stability in the absence of antioxidant. Previous studies concerning the aging of radiation cures appear to have been made using materials containing carbon black, which is now known to act as an antioxidant; it is necessary, for work of fundamental significance, to use gum stocks based on very pure rubber.
The Degradation of Main Chains and Crosslinks in the Aging of Vulcanizates
Authors: Lyubchanskaya L. I. , Kuzminskiĭ A. S. 
Published: February 2011

Abstract
In sulfur vulcanizates the energy of the bond between the atoms of sulfur in the crosslinks may differ essentially from the energy of the bonds in the main chains of the polymer since, as is known, the thermal decomposition of the polysulfide bonds may be brought about at considerably lower temperatures than the decomposition of the main chains. It was found by one of the present authors2 that the thermal decomposition of the sulfur bonds brings about an inhibition of the oxidation which develops in the chains of the polymer. Consequently we must not regard the destruction of the chains and the decomposition of crosslinks as independent processes. Nevertheless the difference in the rates of destruction and decomposition is so great that these processes may be separated. There are in the literature different views as to which elements in the structure of the vulcanizates the processes of aging extend to. Tobolsky asserts that the chemical relaxation of stress is caused by oxidative destruction of the polymeric chain of the vulcanizate independently of its structure. On the other hand Watson and coworkers consider that the decomposition of the lattice of the vulcanizate is the result of scission of chemical crosslinks. In the present investigation it was established that, depending upon the composition of the vulcanizate and the conditions of the experiment, the process of aging may involve both the chains of polymer and the crosslinks, forming a three-dimensional lattice of the vulcanizates.
Molecular Ordering in Polymers Precipitated from Solution
Authors: Igonin L. A. , Ermolina A. V. , Ovchinnikov Yu V. , Kargin V. A. 
Published: February 2011

Abstract
1. The variation of the ordering in polyvinyl chloride and polymethylmethacrylate precipitated from solutions in the process of heat treatment was studied. 2. The intensity curves calculated from the electronographic (electron diffraction) data show that the heat treatment leads to the formation of a more ordered arrangement of the chain molecules of these amorphous polymers. 3. The variation of the degree of ordering in these polymers in the heat-treatment process causes a change of the mechanical properties of the polymers and of their capacity for reprocessing. 4. From the data obtained we may conclude that the form of the polymer molecules and their mutual arrangement in the solution differ from those in the condensed state.
Dispersion of Carbon Black in Rubber: Revised Calculation Procedure
Authors: Medalia A. I. 
Published: February 2011

Abstract
Carbon black, the most important reinforcing filler for rubber, must be well dispersed if it is to function effectively. The state of dispersion of the carbon black can be studied effectively by microscopic examination of a thin (2µ) section of the rubber compound, using transmitted light, as described by Tidmus and Parkinson. Under the microscope, agglomerates of undispersed carbon black are visible. These agglomerates, which may range in size up to 100µ or even larger, are sectioned more or less cleanly by the glass knife, and appear as black or dark brown islands in a light brown field. While this method was originally proposed for qualitative estimation of the degree of dispersion, a quantitative calculation was subsequently developed by Leigh-Dugmore, by means of which the percentage of carbon black dispersed below a certain size was calculated. This calculation has been helpful in permitting a quantitative comparison of stocks of widely different visual appearance. As experience has accumulated with the Leigh-Dugmore method, some puzzling observations have been made. Frequently, the modulus level of a stock of a given dispersion was found to be higher than the proportionate modulus of a stock of 100% dispersion. Furthermore, stocks have occasionally been prepared with a measured dispersion rating of less than zero (see below). It thus seemed worthwhile to re-examine the Leigh-Dugmore calculation.
Carbon Black Structure Effects in Synthetic Rubbers
Authors: Bolt T. D. , Dannenberg E. M. , Dobbin R. E. , Rossman R. P. 
Published: February 2011

Abstract
Carbon blacks are composed of spherical particles which are to varying degrees arranged in chainlike structures. This type of particle association, which is readily seen in electron photomicrographs of most carbon blacks, can be termed “primary structure”. The use of the term “structure” to describe interparticle association must not be confused with the basic intraparticle structure of an atomic crystallographic nature. There is strong evidence that primary structure units, and possibly individual particles, can further associate or flocculate in fluid or elastomeric systems. This is a secondary type of structure formation which can be readily disrupted under the influence of mechanical strain. Some investigators have used the term “structure” to describe this strain-sensitive flocculation behavior. It is suggested here that carbon blacks possess both primary structure features and the ability to form secondary structures by flocculation in dispersed systems. The tendency to form secondary structures is probably greater with carbon blacks possessing a high degree of primary structure. Unless otherwise specified, the term “structure” in this paper will be used in the sense of primary structure. The structure of carbon blacks is thought to originate in the flame by the agglomeration of growing carbon nuclei and particles. The appearance of electron micrographs of carbon blacks lends some support to the assumption of simultaneous agglomeration and growth processes. Carbon blacks having a broad particle size distribution are characterized by carbon black chains, where each chain is composed of particles of the same size, rather than a randomized distribution of various sized carbon black particles. Thus, these chainlike structures must result from the continued growth of agglomerates formed from neighboring carbon particles at the same stage of their growth history. This process results in a chemical fusing of these particles as layers of new carbon are deposited on the surfaces of actively growing agglomerates.
The Law of Rubber Friction
Authors: Bartenev G. M. , Lavrentev V. V. 
Published: February 2011

Abstract
The investigation of the law of rubber friction on smooth hard surfaces over a wide range of normal pressures from 1 to 200 kg/cm2 has shown that Coulomb's formula applies in the small load region, and Thirion's formula in the region of larger loads. This conforms with the formula proposed earlier by one of the authors; this formula becomes the Coulomb's formula at small loads and Thirion's formula at large loads. Schallamach's formula has a physical meaning but is not confirmed experimentally.
Rubber Models of Yarns and Cords; the “Doubling” of Single Rods
Authors: Wilson N. , Treloar L. R. G. 
Published: February 2011

Abstract
In any theory of the physical properties of yarns and cords certain basic assumptions must be introduced regarding (a) the geometrical disposition of the filaments or other elements of the structure, (b) the physical properties of the filament material, and (c) the specification of the stresses and strains in the structure. On account of the complexity of the problem, the verification of a theory by experiments on actual textile yarns is not easy, firstly because their geometrical structure is fundamentally irregular and secondly because the elastic properties of typical textile fibers are very imperfect, the stresses not being uniquely determined by the strains. In order to examine the basic elements of the theory of the stresses in twisted filament assemblies, it has been thought desirable to examine certain simpler systems in which these difficulties are eliminated. For this purpose experiments have been carried out with model yarns, employing vulcanized rubber filaments. This material has the advantage of possessing almost perfect elastic properties, which can be simply specified. In addition, its low modulus and high extensibility permit the use of large ‘filaments’ which can more easily be disposed in a geometrically definable manner. The present paper is concerned with the measurement of the stresses in a system comprising two cylindrical rubber rods twisted together, as in the formation of a two-ply cord. Two cases are considered: in the first the two rods are initially free from torsion, while in the second the rods contain initial twist (analogous to singles twist in two-ply cord), before being twisted together. For each of these systems the stresses measured are the tension along the ‘cord’ axis and the couple about this axis, for various values of axial extension and ‘cord’ twist. These are compared with corresponding values calculated theoretically, using the measured values of the parameters defining the geometry of the system and of the elastic constants of the rubber.
Elastomeric Adhesion and Adhesives
Authors: Voyutskiĭ S. S. 
Published: February 2011

Abstract
In a review by Weidner and Crocker, published, under this title, in Rubber Reviews for 1960, there is expressed a series of critical remarks about the development by my collaborators and me of the diffusion theory of specific adhesion of polymers. Unfortunately, the authors of the review made use of only four articles, having ignored a series of recent articles and my special monograph which appeared in 1960. This probably was the cause of the one-sided view of Weidner and Crocker. I will try here very briefly to cite some principles of the diffusion theory of adhesion which the review has disregarded and also I will endeavor to reply to some of the comments of the authors.
Elastomeric Adhesion and Adhesives
Authors: Weidner C. L. , Crocker G. J. 
Published: February 2011

Abstract
We would like to point out first of all that the seven recent publications of Voyutskil were not “ignored” by us but were simply unavailable to us at the time our review was written. We have now had the opportunity of reading all but one of his recent contributions but see no reason to change our original viewpoint. In Voyutskii˘'s cited references, and particularly in his own works, he has emphasized the role of diffusion in adhesion. His viewpoint has been conditioned by his notion that adsorption values are inconsistent with high peeling work, and cannot account for peel adhesion rate dependence, and the strong adhesion of nonpolar polymers. We would fully agree that diffusion often plays a role in adhesion, certainly in autohesion and probably in other cases of polymer bonding as well when the polymers are not too dissimilar. The effect of mutual solubility in promoting strong adhesion has been a long accepted principle. The suggestion of it is inherent in the article on tackiness by Josefowitz and Mark and it had grown in acceptance sufficiently by 1947 to be clearly stated in an encyclopedia article on adhesion by one of us. But to regard this mechanism as dominant in such cases as adhesion of NBR to cellophane seems unjustified.