bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Temperature on Rate of Oxidation of Rubber. Nature of Resultant Deterioration
Authors: Shelton J. Reid , Wherley Fred J. , Cox William L. 
Published: February 2011

Abstract
The same reaction appears to be rate-controlling in the oxidation of natural rubber and GR-S stocks at all temperatures in the range studied, 50° to 110° C. This is apparent from the linear relationship established between rate of oxygen absorption and the reciprocal of the absolute temperature. Presumably this would also be true for a reasonable extrapolation to lower or higher temperatures. Thus it is possible to determine the probable rate of oxygen absorption at room temperature on the basis of data obtained in short-term tests at higher temperatures, provided data are available at several temperatures. The effect on properties which accompanies the absorption of a given amount of oxygen varies with the temperature. For example, aging at higher temperatures produces a softer stock with lower modulus and higher elongation than is obtained by the absorption of the same amount of oxygen at a lower temperature. Thus chain scission predominates at higher temperatures, while cross-linking becomes of greater relative importance at lower temperatures. These facts, together with the observation that the same reaction is rate-controlling at all temperatures studied, indicate that the degradation reactions must be secondary reactions which are not rate-controlling. One cannot predict the aging characteristics of a stock by the use of an accelerated test at only one temperature. It is possible, however, to establish a quantitative measure of the rate of change in a given property (per unit amount of oxygen absorbed) as a function of temperature by means of tests at more than one temperature. Thus it is now possible to utilize short-term oxygen-absorption measurements at, say, three temperatures to establish the relationships, and then to extrapolate the data to lower temperatures and predict the time required to absorb a given amount of oxygen and the degradation of properties to be expected under comparable conditions at the lower temperature. If a change from oxygen to air is also involved, the effect of the changes in oxygen concentration must also be taken into account.
Acceleration and Aging
Authors: Haehl Adrien 
Published: February 2011

Abstract
In a study of the protection of vulcanized rubber against aging by combinations of the zinc salt of mercaptobenzimidazole and “true” antioxygenic agents, it has been found that such combinations have a synergetic effect of considerable magnitude in the protection of vulcanizates which are accelerated by mercaptobenzothiazole. On the other hand, in the case of vulcanizates accelerated by diphenylguanidine, the effect is slight or even negligible. On the assumption, therefore, that the nature of the accelerator has a great influence on the effectiveness of the protective agents, the latter were classified with respect to the accelerators used. In this way it was established that bis-(2-hydroxy-3-tert-butyl-5-methylphenyl) methane, when employed alone is by far the best protective agent against the aging of vulcanized rubber accelerated by diphenylguanidine. In addition by combining this “true” antioxygenic agent with the zinc salt of mercaptobenzimidazole it was found that only slightly greater protection can be attained than is possible by the antioxygenic agent alone. Consequently in this case one should not speak of a synergetic effect. The experiments lead quite definitely to the conclusion that the mechanism of protection against aging when a deactivating agent is present depends upon whether the accelerator employed is mercaptobenzothiazole or diphenylguanidine.
Plasticity and Filler Structure in Carbon Black Stocks
Authors: Whorlow R. W. 
Published: February 2011

Abstract
Continuing previous studies on the changes in stiffness of a carbon black masterbatch when stored at normal or elevated temperatures or when subjected to shear deformation, the changes during room temperature storage have been studied in more detail. From the results obtained, a modified hypothesis as to the behavior of carbon black structures in unvulcanized rubber is put forward, which accounts for all the features of the behavior of rubber/black stocks so far observed in this work.
Calculable Properties of Technical Rubber Mixtures
Authors: Schreuer E. 
Published: February 2011

Abstract
As a very enlightening example of nonideal material mixtures, technical rubber compounds show deviations from the additivity of thermodynamic and elastomechanical measured quantities which are to be expected according to the rule of mixed components. The deviations have an intrinsic relationship, and bear a relation to the concentration of the so-called active additives.
Nonlinearity in the Dynamic Properties of Vulcanized Rubber Compounds
Authors: Fletcher W. P. , Gent A. N. 
Published: February 2011

Abstract
Measurements are described of the dynamic properties of rubber, loaded with various amounts and types of filler, when subjected to mechanical vibration in simple shear at amplitudes from 0 to 3 per cent shear in the frequency range 20 to 120 c.p.s. The decrease of dynamic modulus with increasing amplitude is shown, for a wide range of filler types and concentrations, to be determined by the amount of stiffening produced by the filler. This relationship is not influenced by variations in the vulcanizing ingredients, reasonable variations in state of vulcanization, addition of softener, or imposition of static shear strain. Rubber compounds stiffened by mixture with, or chemical combination of, other polymers exhibit a smaller order of nonlinearity than that described above and also exhibit much lower hysteresis values within the amplitude range 0 to 3 per cent shear.
Factors Affecting the Measurement of Strain
Authors: Best L. L. 
Published: February 2011

Abstract
1. Although alteration of the mixing, vulcanizing, and testing cycle for the measurement of strain does affect the physical properties of the final vulcanizate, a high degree of correlation can be obtained between the results of the rapid test and the normal test. The rapid test, which will not consume any more man-hours than the normal test, can be fitted in to the normal daily procedure with little loss of testing capacity, and provides satisfactory data in a period of three hours for thirty-two test-specimens, whereas more than two days are needed by the normal standard procedure. 2. The mixing, curing, and testing error associated with the measurement by the rapid method is less than that obtained with the normal test method. 3. The rapid method can be used for predicting the results which would be obtained by many physical tests carried out by standard procedures and would, therefore, be generally useful for control measurements in industrial concerns. 4. Isothermal conditioning of the compounded stock after mixing does not appear to reduce the error associated with the rapid test, but does alter the relation between the rapid and normal tests. 5. Immersion of test-specimens in cold water after vulcanization does not improve reproducibility or alter the value of the strain measurement. 6. Molded strain specimens are liable to vary in respect of cross-sectional area. Such variations can produce considerable errors in strain measurements, particularly with rubbers of high strain or low modulus characteristics. A simple method for the correction of these errors is advanced which increases the reproducibility of the strain test.
The Velocity and Temperature Dependence of Rubber Friction
Authors: Schallamach A. 
Published: February 2011

Abstract
It is shown experimentally that the velocity of frictional gliding under constant tangential stress of rubber on glass and on silicon carbide cloth is, in the first approximation, an exponential function of the reciprocal absolute temperature and of the tangential stress. It is suggested that frictional gliding of rubber is a rate process.
Plasticization of Rubber in the Form of Latex
Authors: Conté Marc 
Published: February 2011

Abstract
When in the form of latex, rubber can be oxidized by thiols under hot conditions. The reaction apparently proceeds by the same mechanism as that characteristic in the action of peptizing agents on rubber during mastication. The results obtained confirm the hypothesis that the thiol is transformed quantitatively into the corresponding disulfide, with resultant oxidation of the rubbert. This transformation is a function of the pH value, and the best results are obtained when the pH value is around 4 and in the absence of NH4 ions (which have an inhibitory effect). Latex preparations of this type can be utilized for studying the chemical reactions of rubber in emulsion and for the preparation of rubber derivatives which are more soluble than those prepared from rubber latex which has not been degraded. In addition, such latex preparations are excellent adhesives which, in contrast to already known products (latex treated with hydrogen peroxide or other peroxides), give a sticky film by simple drying at room temperature. In this way heating can be avoided in cases where it has harmful effects and where the use of an oven is inconvenient. Finally, this type of latex is more adaptable to certain direct applications, both because of the superior adhesive properties of the rubber and because, with a relatively plastic coagulum, mastication is easier.
Zinc Soap Formation and the Gelling of Latex
Authors: Newnham J. L. M. 
Published: February 2011

Abstract
The gelling effect of zinc oxide on ammoniated latex is known to be due to the formation of zinc soaps. The object of the present work was to investigate the formation of zinc soaps under varying conditions in order to elucidate the gelling mechanism more clearly. The main variables affecting the zinc ammine ion formation in an ammonia solution containing given amounts of ammonium salts and soluble zinc are pH and temperature. Falling pH or rising temperature favor formation of the more chemically reactive lower zinc ammine ions, and give rise to the formation of zinc soaps if soaps are present. It is suggested that zinc soap formation in the serum of ammoniated latex and the consequent gelling of the latex depend on the presence of specific zinc ammine ions.
Fractions from Hevea Brasiliensis Latex Centrifuged at 59,000 g
Authors: Cook A. S. , Sekhar B. C. 
Published: February 2011

Abstract
Homans and van Gils have separated fresh latex, by centrifuging at 2,000 r.p.m. (ca. 1,000 g.) into two fractions, white and yellow, both consisting mainly of rubber particles and serum. They also reported the discovery of another discrete phase in fresh latex, which they called lutoids, and which were found mainly in the yellow fraction. Huret has described the separation of ammoniated latex at 400,000 g. into a white fraction, a yellow layer, and clear serum. We have obtained four distinct fractions on centrifuging fresh latex at 20,000 r.p.m. (59,000 g.), and these have not previously been described, although McColm has reported on the sludge obtained at 40,000 r.p.m. Latex was collected from a field of mixed clonal seedlings at the Rubber Research Institute of Malaya Experiment Station and cooled in an ice-water mixture within an hour of tapping the first tree. Part of the latex was weighed into Lustroid (celluloid) tubes fitted with air tight caps and spun at 59,000 g. in a refrigerated vacuum centrifuge at 5° C for three-quarters of an hour. Another portion of the latex was ammoniated to 0.5 per cent NH3 by weight, using a 20 per cent solution. Part of this latex was centrifuged with the fresh latex and part after 24 hours. Figure 1 represents diagrammatically the separations obtained.
Relaxation Time Spectrum, Elasticity, and Viscosity of Rubber. I
Authors: Kuhn W. , Künzle O. , Preissmann A. 
Published: February 2011

Abstract
By rapid deformation of a medium in which linear molecules are present, various changes are produced simultaneously in the latter. These changes are more or less independent of one another, and can release independently and totally or partially by rearrangement of valence distances and valence angles in the chain molecules. By virtue of such relaxation processes, a portion of the stress originating in the rapid deformation disappears, with a changing time requirement for the various portions. A relaxation time spectrum is thus formed. The relaxation time spectrum consists of a finite number of restoring force mechanisms with proper relaxation times or of a continuous spectrum. Both the creep curves (the dependence of the length of a body on time at constant load), and stress relaxation (decay of the stress observed in test sample kept at constant length after rapid deformation), as well as the total visco-elastic behavior, especially the behavior at constant periodic deformation of the test sample, are determined by the relaxation time spectrum. The appropriate Quantitative relationships were derived.
Hydrogenated Synthetic Elastomers
Authors: Jones R. Vernon , Moberly C. Wayne , Reynolds W. B. 
Published: February 2011

Abstract
Several years ago the Phillips Petroleum Company initiated a study of the properties of hydrogenated synthetic elastomers. The result of this investigation has been the development of a series of thermoplastic hydrogenated polymers, Hydropols, which have certain unusual properties not found in other available plastics. Prior to this investigation, little was known about hydrogenated synthetic elastomers. The hydrogenation of natural rubber had been fairly well investigated since Berthelot heated rubber with concentrated hydriodic acid in a bomb tube and obtained a mixture of high boiling paraffins. Harries stimulated the work of Staudinger and Fritschi and Pummerer and Burkard by his statement, “It would be of great importance to be able to carry out the reduction of rubber, because hydrorubber probably distills unchanged in a high vacuum, and therefore its constitution could be determined for certain.” This hydrogenation of rubber was simultaneously accomplished in 1922 by Staudinger and Fritschi using a platinum catalyst dispersed in purified rubber at 270° C and 93 atmospheres of hydrogen pressure for 10 hours, and by Pummerer and Burkard using dilute solutions of depolymerized rubber in methylcyclohexane with a platinum catalyst at ordinary temperatures and atmospheric pressures.
Copolymerization Reactions of Cinnamic Acid, Its Derivatives, and Some Related Compounds
Authors: Marvel C. S. , McCain G. H. , Passer Moses , Taft W. K. , Labbe B. G. 
Published: February 2011

Abstract
A study of the copolymerization of butadiene with cinnamaldehyde, cinnamic acid, methyl cinnamate, ethyl cinnamate, and trans-cinnamonitrile showed that all these monomers yield rubbery copolymers with butadiene and certain of these have been evaluated and compared to current synthetic rubbers of the GR-S type. In general, these monomers to the extent of 10 to 90 parts of butadiene yield copolymers roughly equivalent to the standard GR-S which contains approximately 25 parts of styrene. The cinnamic acid-butadiene copolymer has excellent tensile strength. The trans-cinnamonitrile copolymer shows no improvement in oil resistance over GR-S. These cinnamic acid derivatives all enter the growing butadiene copolymer chain somewhat more slowly than does butadiene, so that the copolymers contain a lower percentage of the comonomer than does the charging stock used. Some experiments were conducted on the copolymerization of these cinnamic acid derivatives with other monomers than butadiene, the copolymerization of the furan analogs of the cinnamic acid derivatives, and the copolymerization of α-cyano-β-phenylacrylic acid derivatives.
Infrared Examination of Various Polyisoprenes
Authors: Richardson W. S. , Sacher A. 
Published: February 2011

Abstract
It is well known that, in general, the laboratory polymerization of diene monomers leads to materials which are intramolecular mixtures of various types of addition products. Thus, synthetic polyisoprene has been shown to contain chemical groupings arising from 1,2, 3,4, and 1,4 addition of the isoprene units. This is in contrast to the naturally occurring high polymers of isoprene, the rubbers and guttas, which appear to be exclusively cis-1,4 and trans-1,4 adducts, respectively. An exception to this last statement is the polyisoprene derived from chicle, which is a mixture of cis-1,4 and trans-1,4 addition. In this case, however, the mixture is an intermolecular one, and fractionation of the material leads to components which are all cis-1,4 and all trans-1,4. The general problem of diene polymerization is, of course, of great importance, and the synthetic polyisoprenes are of particular interest because of their relationship to natural rubber. The following attempt to obtain a quantitative analysis for the various types of addition occurring in synthetic polyisoprenes may lead to a better understanding of the nature of these materials and may be of help in elucidating the effect of microstructure on rheological properties.
Mechanism of the Crystallization of High Polymers
Authors: Schuur G. 
Published: February 2011

Abstract
The crystallization of higher polymers is a phenomenon which is not yet fully understood, one of the main difficulties being to explain how the spherulites arise. An attempt will be made in this paper to draw a clearer picture of the mechanism of crystallization and thus to account for the origin of spherulites. It will then be seen how several other phenomena involved in the crystallization of natural rubber can be shown to be logically interrelated. The current view is that a crystalline polymer consists of a continuous amorphous phase containing small crystalline regions, the crystallites. The evidence as to the size of these crystallites, however, is at present inconclusive, because only the lower limit of their size can be measured by means of x-ray examination. The reason is that, owing to the absence of reflections of a higher order, the effect of irregularities in the crystallites and of the heat motion of the molecules cannot be measured separately. Another doubtful question is whether the small angle interference maxima are to be interpreted as a measure of mean distances between the crystallites. To do this, Wallner has to resort to the assumption that the crystallites are unstable, whereas it is presumed, on the evidence of the mechanical properties of the high polymers, that a crystallite is stable and permanent. Hoffmann found 82 ± 7 per cent of crystalline material in polychlorotrifluoroethylene and Buckley, Cross, and Ray found as much as 95 per cent in polymethylene. Such high percentages make it doubtful whether the crystalline phase can be discontinuous at all. In this article any volume of material in which the molecules lie parallel is called a crystallite. The direction in which the molecules are oriented is termed the longitudinal direction of the crystallite. It is immaterial to the argument whether a crystallite consists of several crystallites, aligned in parallel separated by a small amount of amorphous material, or of a single crystallite containing large irregularities.
Mechanical Investigations of Elastomers in a Wide Range of Frequencies
Authors: Philippoff Wladimir 
Published: February 2011

Abstract
Many experimental investigations have shown that plastics in general, as well as elastomers and their solutions, do not behave like Newtonian liquids. They both have viscosity and elasticity, the combination of which, according to the Maxwell postulate, causes their properties to be dependent on time, and leads us to call them viscoelastic bodies. This dependence does not exist, either for the Newtonian liquid whose mechanical properties are determined by its viscosity, or for the elastic body whose properties are determined by its elasticity. The time element introduces a peculiar difficulty in measuring the mechanical properties of these substances. Whereas the well-known Maxwell body describes this time dependence in simple mathematical expressions, it does not apply to the experimental results. The properties of viscoelastic bodies are not described by a Maxwellian body, but rather by a distribution of an infinite number of Maxwellian bodies, each having a so-called relaxation time. The existence of this infinite distribution calls imperatively for an investigation of the properties of these viscoelastic bodies in as wide a range of frequencies or times as possible in order to define them. Most investigators have used one method in a range of frequencies no wider than about 1 to 100. This range can be extended by using the observation of Ferry that the properties of viscoelastic bodies investigated at different temperatures, in the case of dynamic investigations with sinusoidal vibrations, seem to be described by shifting one standard curve on the frequency axis. One can superimpose measurements at different temperatures and extend the range of frequencies to about 1 to 1,000,000. But using Ferry's method of reduced variables necessitates some assumptions that, though very probable, have as yet not been proven exactly by experiments. It therefore seemed important to have a method for investigating the mechanical properties of viscoelastic bodies in a frequency range of about 1 to 1,000,000 under isothermal conditions. This paper describes a basic method and the results obtained for several elastomers.
The Vulcanization of Rubber. XI. Influence of the Degree of Vulcanization on the Internal Friction of Unloaded Butadiene-Styrene Vulcanizates
Authors: Reznikovskii˘ M. M. , Yurovskaya V. S. , Dogadkin B. A. 
Published: February 2011

Abstract
1. The relation between the internal friction, which is responsible for heat formation during the dynamic deformation of unloaded vulcanizates of butadiene-styrene rubber, and the content of combined sulfur, which was changed within the limits of 0.5 to 26 per cent in the rubber, was studied. 2. It is shown that internal friction and the related relaxation properties do not depend on the percentage of combined sulfur up to 9.0 per cent. Further increase of the combined sulfur content causes a sharp increase of the internal friction of the rubber. 3. For the same vulcanizates of butadiene-styrene rubber, the equilibrium stress, as well as its energy and entropy components, were measured. It is shown that in vulcanizates which contain combined sulfur in proportions not greater than 8.0 per cent, the nature of the stress is predominantly entropic. Further increase of the combined sulfur content causes an increase of the energy component of the stress. 4. Proceeding from the values of the entropy component of the equilibrium stress, on the basis of the approximate theory of Wall, the values of the molecular weights of a chain segment between the cross-links of the spatial network M* were calculated for vulcanizates containing varying percentages of combined sulfur. 5. It is shown that the value of M* is 7000 for the polymer studied and is critical in the sense that further densening of the network causes a sharp increase of both internal friction and the energy component of the equilibrium stress. The hypothesis is advanced that the value of M*crit. can be regarded as a criterion of the flexibility of the molecular chains of the polymer studied.
Migration Effects in Oven Aging
Authors: Juve A. E. , Shearer R. 
Published: February 2011

Abstract
Aging of materials individually in ovens contaminated from previous usage does not assure freedom from contamination. These contaminants cause an increase in the rate of deterioration. Materials migrating from unlike stocks aged together may have varying effects, adverse, beneficial, or no effect, depending on the compositions being employed. The test-tube method of aging is an excellent method for studying these migration effects as well as for conducting routine aging tests in their complete absence.