bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apparatus for the Continuous Measurement of Stress Relaxation in Vulcanized Rubber
Authors: Danjard J. C. 
Published: February 2011

Abstract
The measurement of stress relaxation in vulcanized rubber is based on the principle that, when kept at constant elongation, a stretched sample of rubber shows a progressive decrease of stress with time and that this decrease depends both on the nature of the compound and on the temperature of testing. The resultant curve is a decreasing potential, which is expressed approximately by the equation: σt=σ0⋅e−kt, where σt is the instantaneous stress at time t, σ0 is the initial stress, and k is a reaction rate constant which depends on the free activation energy of the rubber chain molecules. Tobolsky was the first to apply the relaxation theory to the study of the oxidation behavior of compounds and to the approximate determination of the nature of vulcanization structures. Certain types of apparatus are available for the discontinuous measurement of this stress relaxation, but we have designed, with the aid of the French Rubber Institute technical service, a relaxometer for the continuous recording of this phenomenon.
A New Method for Determining the Dynamic Mechanical Properties of Rubber
Authors: Morris R. E. , James R. R. , Guyton C. W. 
Published: February 2011

Abstract
In submarines, machinery with reciprocating rotating parts is placed on rubber mountings to isolate noise and vibration from the hull of the vessel. Otherwise the hull would radiate the noise to the sea and facilitate detection of the submarine by the enemy. The dynamic mechanical properties of the rubber in the mountings determine to a large extent their effectiveness in isolating noise and vibration. Only within the last ten years has reliable information become available on the dynamic mechanical properties of rubber at high frequencies of vibration. Most of this advance has been due to Nolle. Other workers in this field have been Witte, Mrowca and Guth, Hillier, Cramer and Silver, and Morris, James and Snyder. Nolle gave an excellent description and analysis of techniques for measuring the dynamic mechanical properties of rubber in the frequency range of 0.1 to 120,000 cycles per second (cps). The methods which he described were identified as rocking-beam oscillator, vibrating reed, strip transmission, strip resonance, and magnetostriction. Guth and associates, Hillier, and Cramer and Silver used the strip transmission method in their respective investigations. Morris, James, and Snyder used a bar transmission method which had not been previously described. This paper deals with a modification of the bar transmission method, whereby the resonant frequency and dispersion of the vibrational energy above and below the resonant frequency are measured. From this information the velocity of sound, Young's modulus, and loss factor of the rubber are calculated.
Studies of the Vulcanization of Elastic High Polymers. VI. The Vulcanization of Natural Rubber with Benzoyl Peroxide. Part 1
Authors: Lorenz Otto , Scheele Walter 
Published: February 2011

Abstract
The vulcanization of natural rubber by benzoyl peroxide between 110° and 50° C has been investigated. The analysis of the kinetics has led to the following results: 1. The benzoyl peroxide concentration decreases at all temperatures according to a reaction of the first order. The velocity constants have been given. 2. Benzoic acid is formed in a slower reaction, but also according to a first order rate. The limiting value of benzoic acid formation depends on the temperature. It decreases with increasing temperature. The velocity constants for benzoic acid formation have been calculated. 3. With larger additions of peroxide to the rubber, both reactions are of the zero order as long as the solubility limit of the peroxide is exceeded. 4. The temperature dependence of the velocity constants of both reactions has been discussed, and it has been shown that at lower temperatures the formation of benzoic acid and the decrease of peroxide become equally rapid. 5. The analogy between thiuram vulcanization and peroxide vulcanization with respect to their kinetics has been pointed out. 6. It has been made apparent that, in both peroxide vulcanization and thiuram vulcanization, one is obliged to assume the formation of an intermediate compound. But, at the same time, it is not possible to make this consistent with the reaction mechanism which Farmer has developed for peroxide vulcanization, nor to apply to peroxide vulcanization the relationships found by Bartlett for the polymerization of allyl acetate by benzoyl peroxide.
The Vulcanization of Butadiene-Styrene Rubber in the Presence of Sulfenamide Accelerators
Authors: Dogadkin B. , Fel'dshteĭn M. , Pevzner D. 
Published: February 2011

Abstract
1. It is established that N,N-diethyl-2-benzothiazolesulfenamide has a structure-forming effect in stocks of butadiene-styrene rubber when these are heated at vulcanization temperatures, even in the absence of the usual vulcanizing agent, sulfur. These stocks, after extraction with acetone, still contain chemically combined sulfur and nitrogen, and the contents of these increase with a longer heating period. 2. The change of the modulus of the above stocks is a linear function of the amount of N,N-diethyl-2-benzothiazolesulfenamide which has reacted. 3. The structure-forming action of N,N-diethyl-2-benzothiazolesulfenamide can be regarded as a polymerization reaction, brought about by the free radicals formed in the thermal decomposition of this compound. 4. It is possible to vulcanize ordinary sulfur-containing butadiene-styrene rubber stocks in the presence of sulfenamide accelerators without the use of the accelerator activator, zinc oxide. 5. The kinetic curves of combination of sulfur and of the change of the equilibrium modulus, for ordinary sulfur stocks containing the sulfenamide accelerators (N,N-diethyl-2-benzothiazolesulfenamide and N-cyclohexyl-2-benzothiazolesulfenamide), is S-shaped, and shows an initial “induction” period in the vulcanization. This latter is especially distinct in stocks containing N,N-diethyl-2-benzothiazolesulfenamide. 6. Multilayer rubber articles made from plied stocks containing sulfenamide accelerators have stronger adhesive bonds. There are two reasons for this increased bond strength : (1) the retardation of the vulcanization kinetics in the initial stage of the vulcanization process, which is characteristic of the accelerators in question, and which has the effect of prolonging the length of time that the plied stocks remain in a semiviscous condition; and (2) the formation of the stronger —C—C— bonds as a result of polymerization reactions, which are stimulated by sulfenamide accelerators. 7. Vulcanizates prepared with sulfenamide accelerators are different from those with a combination of benzothiazolyl disulfide and diphenylguanidine in that the former have a lower heat build-up and a somewhat greater dynamic deformation resistance.
A Study, by Means of Radioactive Sulfur, of the Mechanism of Vulcanization of Rubber. I
Authors: Bresler S. E. , Pryadilova V. I. , Khainman V. Ya 
Published: February 2011

Abstract
1. In the present work a method was developed for the measurement of the diffusion and the solubility of sulfur in rubber. Values of the diffusion coefficient and the solubility were obtained for a broad range of temperatures. It is shown that the free sulfur in rubber dissolves and diffuses in the form of S8 molecules. 2. The kinetics of sulfur combination with rubber in the presence of an accelerator was investigated. It is shown that at low sulfur concentrations the kinetics is of the first order. The rate constants of sulfur combination were determined, as well as the activation energy (U=23,000 cal./mole) of the process. 3. A study was made of the kinetics of the isotope exchange reaction between elemental sulfur and tetramethylthiuram disulfide in an inert solvent. The experiment showed that the rate constant of the isotope exchange and the rate constant of the combination of sulfur with rubber are equal to one another at all the temperatures investigated (120°–150° C). 4. The conclusion is drawn that the first stage of vulcanization, which governs the overall rate, and likewise the first stage of the isotope exchange reaction, consist in the decomposition of thiuram into radicals, with the diatomic biradical S2 being split off. 5. It is shown that, with an increase in the sulfur concentration, the kinetics of the sulfur combination with rubber ceases to conform to a linear equation. A secondary sulfur combination reaction, taking place at the point where the primary bonding of sulfur to rubber occurred, was discovered. A hypothesis is put forward as to the radical character of the primary sulfur combination, and regarding the union of polysulfide chains with the radicals in polymer chains, radicals which were formed by means of the primary action of sulfur upon the hydrocarbon.
Mastication. Part III. Chemical Verification of the Mechanical Degradation Mechanism of Cold Mastication
Authors: Ayhey G. , Moore C. G. , Watson W. F. 
Published: February 2011

Abstract
The plasticization of natural and synthetic rubbers by cold mastication results from the degradation of the macromolecules. In Part I experimental evidence was presented that such degradation is caused by mechanical rupture of primary carbon-carbon bonds in the polymer (R—R) to give polymer radicals (R · ) which are stabilized by oxygen to give degraded polymer molecules. Such a mechanism, invoking mechanical shear, had been advocated previously, e.g., by Staudinger, most explicitly by Kauzmann and Eyring, but required systematic mastications under nitrogen with a large variety of compounds (radical acceptors) to demonstrate more critically its consistency with experimental observations. However, Part I provided no direct chemical evidence supporting the mechanism by demonstrating reaction between the rubber radical and radical-acceptor molecule. Considering that only of the order of 0.1 per cent of radical acceptor is required for radical termination to give marked degradation, especially favorable reactions and sensitive analytical techniques are required for detecting the basic chemical reactions. The incorporation of radical acceptors into two types of elastomer on mastication has been demonstrated by the use of two radical-acceptor molecules and two distinct analytical techniques: (1) the incorporation of 1,1-diphenyl-2- picryl hydrazyl into natural rubber, using a spectrometric method, and (2) the incorporation of 1,1′-dinaphthyl [S35]-disulfide into GR-S, using a radiochemical method. The incorporation of the radical acceptors should be correlated with extent of degradation measured by decrease in molecular weight. Quantitative correlations have been obtained for both the above radical acceptors.
Adiabatic Stretching as a Method of Investigation of the Elastic Properties of Rubberlike Materials
Authors: Votinov M. P. , Kuvshinskiĭ E. V. 
Published: February 2011

Abstract
1. A direct method has been proposed for the study of the elastic characteristics of rubber stocks under nonequilibrium deformation conditions. 2. This method has been successfully applied in the study of the elastic characteristics of “crystallizing” and “noncrystallizing” unloaded rubber compounds.
Transformation by the Action of Heat and Oxygen of the Sulfur Bonds Which Compose a Vulcanization Network
Authors: Degteva T. G. , Kuzminskiĭ A. S. 
Published: February 2011

Abstract
1. A study of the effect of combined sulfur on the oxidation of swollen and unswollen polybutadiene vulcanizates shows that stocks vulcanized with different types of accelerators (tetramethylthiuram disulfide, diphenylguanidine, and zinc ethylphenyldithiocarbamate) form sulfur bonds which differ in their content of long polysulfide groups. 2. It is shown that sulfur liberated by the polysulfide bonds in vulcanizates reduces the speed of the oxidation reaction and the equilibrium concentration of stable peroxides. The sulfur content also governs the structure-forming process which develops when a raw polymer containing sulfur is oxidized at 90° C. The decomposition products of the polysulfide groups likewise lower the speed of oxidation in swollen vulcanizates at 150°. 3. When swollen vulcanizates are heated in the absence of oxygen at 150°, only the polysulfide bonds decompose. Heating unswollen vulcanizates under the same conditions, however, brings about the reverse effect, viz., structure formation. 4. Sodium sulfite and alcoholic alkali do not remove completely the polysulfide sulfur from vulcanizates. 5. In the process of vulcanization a rearrangement of the sulfur bonds takes place, and this is accompanied by a reduction of the polysulfide content.
Role of Particle Diameter and Linkage Formation in Rubber Reinforcement
Authors: Blanchard A. F. 
Published: February 2011

Abstract
Fillers with little effect on abrasion resistance differ further from carbon blacks in having little or no tendency to introduce some form of strong-type linkage which could sitffen and strengthen the rubber at high extensions. Such linkages are here termed primary to distinguish them from secondary (weak-type) linkages, which have a range of lower strengths as revealed by breakage with applied stress, and contribute little to reinforcement. The abrasion resistance for a given filler concentration is much improved even by remarkably small numbers of primary linkages if the particles are sufficiently small; and it is comparatively insensitive to the number of primary linkages in the quantities normally obtained with carbon blacks. For instance, a considerable degree of reinforcement is obtained with the partially graphitized black known as Graphon, although this black shows drastically reduced capacity to form linkages and little change in particle diameter. The large differences in the wear resistance of vulcanizates containing different grades of carbon black must therefore be attributed mainly to the particle diameter itself rather than to the linkages formed. Moreover, primary linkages as reflected by stress-strain measurements could not explain the effect of particle diameter on reinforcement because they are unrelated to particle diameter. For good wear resistance the particles probably need to have macro-molecular dimensions, though small. To regard the effect of particle diameter in terms of the interfacial area for linkage formation is inconsistent with the above conclusions. For a given dispersion and concentration of filler it is suggested that reinforcement is most likely to find proper expression in terms of the number of linkages per particle and the number of particles. This is expressed mathematically in a tentative, empirical form of equation designed to fit general conceptions, and to correlate roughly the abrasion resistance with filler particle diameter and with primary linkages as reflected by stress-strain measurements. The equation implies that reinforcement increases with diminishing particle diameter until an optimum is reached, and thereafter decreases to become negligible for particles of molecular dimensions.
The Sorption of Water by Rubber
Authors: Tester D. A. 
Published: February 2011

Abstract
In the absence of air the absorption of water by a vulcanized crepe rubber tends to an equilibrium value in accordance with an osmotic mechanism of absorption. An equation for absorption as a function of time, derived by consideration of such a mechanism, represents the experimental data adequately. A relationship may be derived from the basic rate equation, correlating equilibrium absorption with ambient vapor pressure. This equation also gives good agreement with the experimental data. The divergence from the theoretical relationship found for absorption in the presence of air may be attributed to oxidative aging of the rubber. This effect is most marked at elevated temperatures, where the results of absorption under nitrogen are very much lower than those for absorption in the presence of air.
The Quantitative Analysis of Rubber Chemicals. I.
Authors: Scheele Walter , Gensch Christa 
Published: February 2011

Abstract
Studies of the reactions occurring during mastication and vulcanization of rubber must be regarded as still far from completed despite the many valuable experimental contributions. Although many theories have been developed on the mechanism of the processes to be discussed here, either based on the results of direct studies of the chemical processes or on the results of indirect physico-technological methods, one still has the impression that a thorough interpretation of all the relationships is not possible at present. Mastication and vulcanization are undoubtedly very difficult problems which are chosen by the experimenter mainly because of their importance. It is convenient to distinguish between those studies that deal with the elucidation of the reactions of the molecular chains of rubber during mastication, cyclization, and vulcanization, and those that deal with the performance of all the compounds which influence the course of these processes. At present we are interested in the second of these studies. In order to undertake the experimental work, it seemed to be desirable to have analytical methods by which we would be able to determine quantitatively the smallest amounts of accelerators, age resistors and, as well, the decomposition products of various of the rubber chemicals in question. We feel that the development of these methods is absolutely necessary for scientific studies of the kind mentioned and also desirable for the industrial laboratory. Many procedures for the analysis of rubber compounding ingredients, especially of vulcanization accelerators and age resistors, have been published; most of these, however, are for qualitative identification only. Besides precipitation and color reactions, physico-chemical methods are of considerable importance. Spectroscopic investigations of all kinds, and especially the characterization of substances by their ultrared, ultraviolet, and infrared spectra have been widely applied. Work on the application of polarography has become known. Chromatographic analysis has been put to use with marked success to separate compounds of interest and then to identify them by characteristic reactions.
Urethan Rubber from a Polyether Glycol. Properties of Raw Polymer and Vulcanizates
Authors: Hill F. B. , Young C. A. , Nelson J. A. , Arnold R. G. 
Published: February 2011

Abstract
In recent years, the synthesis of polymers by reacting organic diisocyanates with compounds containing two or more active hydrogens has been studied extensively. Much of the pioneering work on the chemistry of organic polyisocyanates and their reaction products was carried out by Du Pont chemists. The products were fibers, elastomers, and plastomeric solids. In Great Britain, research of the Imperial Chemical Industries, Ltd., was directed toward the reaction of polyesteramides with organic diisocyanates to produce vulcanizable polymeric plasticizers, designated Vulcaprenes. In Germany, Bayer and co-workers developed the elastomer known as Vulcollan through their study of the reaction of polyester glycols with organic diisocyanates. Recently, interest in isocyanate-based addition polymers has been stimulated by the commercial availability of a number of polyisocyanates. An elastomer, Chemigum-SL polyester-urethan, was announced by the Goodyear Tire & Rubber Company in 1953. Both Vulcollan and Chemigum-SL are addition polymers of polyester glycols and organic diisocyanates, and both exhibit outstanding toughness and abrasion resistance relative to GR-S or natural rubber. Adiprene-B urethan rubber is a new addition polymer. It differs from other diisocyanate elastomers in that its polymeric segments are aliphatic polyethers rather than polyesters. Adiprene-B is a distinctive elastomer which combines in a single product high strength, abrasion resistance, solvent and ozone resistance, and excellent low-temperature properties.
Studies on Abrasion and Wear of Rubber. I. The Chemistry of Carbon Black and Its Effect on Abrasion as Determined by the National Bureau of Standards Method
Authors: Garten V. A. , Eppinger K. , Weiss D. E. 
Published: February 2011

Abstract
A series of carbon blacks of approximately constant surface area were prepared by heating a strongly acidic carbon black in N2 in the range of 200–1000° C. Their adsorption capacity for alkali and acid, catalytic behavior in H2O2 decomposition, and magnetic susceptibility have been studied and related to their effect on abrasion resistance when incorporated into a standard tire tread stock in the absence of antioxidants. It is suggested that there are, at least, two distinct chemical mechanisms by which carbon blacks can produce reinforcement, that is, by their (irreversible) action as polyphenol type antioxidants (acidic = low-temperature blacks), or in a catalytic (reversible) fashion through temporary stabilization of broken rubber chains on their surface (neutral = medium-temperature blacks).
The Structure of Crystalline 1,2-Polybutadiene and of Other Syndyotactic Polymers
Authors: Natta G. , Corradini P. 
Published: February 2011

Abstract
Systematic x-ray and electron diffraction studies of polymers of 1,3-butadiene prepared by different anionic catalysts have made it possible for us to identify two types of highly crystalline materials. One of us (G. N.) has already reported that our synthesis was carried out with the aid of different highly selective catalysts. The description of the preparation of these catalysts, which have made it possible for the first time to prepare these new polymers, will be separately published by one of us (G. N.) with L. Porri. Infrared analysis carried out by E. Mantica and D. Morero in our Institute has established that one type of these crystalline polymers obtained with heterogeneous catalysts represents a continuous l,4-trans arrangement of the monomer units. X-ray diffraction has shown that this material is dimorphous, having one crystalline modification that is stable at room temperature and another stable above 60° C. The x-ray melting point of a polymer having a molecular weight of the order of 100,000 is around 130° C. The low-temperature modification has an identity period of 4.9 A along the chain axis and a hexagonal packing with a period of a=4.54 A perpendicular thereto, but the symmetry of the crystals, as a whole, is lower. The high temperature modification seems to have the chains in helicoid form. The other crystalline polymer consists essentially of 1,2-monomer units; infrared studies have shown that more than 90 per cent of its double bonds are of the vinyl type and the residual 10 per cent represents a mixture of cis and trans. The higher the proportion of 1,2-units, the more crystalline is the material. Figure 1 shows the infrared absorption curves of two different typical samples of the product. In this article, we limit ourselves to describing the structure of the latter polymer, which, in our opinion, is the more interesting material and which we shall simply call 1,2-polybutadiene. We shall report on the structure of the two modifications of the l,4-trans-polybutadiene in another paper together with the study of the structure of other crystalline polydienes.