bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crack Growth in GR-S Tread Stocks. Relation to State of Cure and Composition
Authors: Juve A. E. 
Published: February 2011

Abstract
A quantitative relation has been established between rate of crack growth and temperature rise, as determined in the Goodrich flexometer test, for GR-S tread stocks compounded with normal quantities of EPC or MPC blacks. This is shown in Equation 1. The relation is valid for all variations which affect the state of cure—that is, time of cure, sulfur or accelerator variation, retarding or activating softeners, etc. For other variations in the tread composition, such as an increase or decrease in the loading of the EPC or MPC black, Equation 2 holds. This relation is valid for all other known recipe modifications which do not involve carbon blacks other than EPC or MPC. Improvements in the balance between flex-cracking and rise in temperature, obtained by compounding or by an improvement in the polymers, may be expressed as the ratio of the observed flexing life to the calculated flexing life using the equation appropriate to the case. This ratio is termed the quality index. Coarser blacks substituted for the EPC or MPC blacks give an improvement in the balance between temperature rise and crack growth. The slope of the curve relating crack growth to heat rise is the same for a variety of flexing machines and for various testing temperatures. Knowledge of this relation has made it possible to evaluate, with some confidence, compounding changes intended to improve the resistance to crack growth without a sacrifice in temperature build-up, and also to evaluate small quantities of experimental polymers without the necessity for precise adjustments in either the proportions of curing agents or curing time.
Measurement of the Scorch and Cure Rate of Vulcanizable Mixtures, Using the Mooney Plastometer
Authors: Shearer R. , Juve A. E. , Musch J. H. 
Published: February 2011

Abstract
The Mooney plastometer may be used to measure the scorching rate and the curing rate of vulcanizable mixtures through a range of temperatures, including the usual processing and curing temperatures. From the data obtained the temperature coefficients of the two processes can be readily calculated. The values for the latter, for the particular mixtures tested, were as follows: The combined cure-rate coefficients should correspond to those determined from stress-strain data. These were found to be: This agreement confirms the accuracy of the corrections applied to the Mooney data as well as the Mooney method for these measurements. When the scorch and cure-rate coefficients are known, both rates may be measured at one temperature, and the results obtained extrapolated with some confidence to higher or lower temperatures.
The Coefficients of Adhesion of Rubber
Authors: Thirion Pierre 
Published: February 2011

Abstract
What conclusions can be drawn from all these experiments? Attempts to find a possible relation between the adhesion characteristics and other mechanical properties of rubber have been unsuccessful. Nevertheless, from a purely qualitative point of view alone, the coefficients of adhesion become progressively less sensitive to pressure as the rubber approaches more and more to the solid state. This seems to be a general rule to which there is no exception. The theoretical interpretation of this peculiar property of rubber cannot be discussed within the scope of the present paper; in fact it offers a complicated problem, for scientific data on the behavior of rigid solids in contact are extremely scarce. Theories advanced to explain the external friction of solids are numerous, but none gives a truly complete explanation of the phenomenon. However, it seems probable at least that the peculiar behavior is attributable to the characteristic state of materials with rubberlike properties, i.e., a state intermediate between that of liquids and of solids. There are numerous applications where advantage is taken of the high resistance to sliding of rubber on the surfaces of dry solid bodies. There would be no point in calculating a priori their coefficients of adhesion under service conditions from the results obtained in the present work, for conditions in service are generally of a very complex nature and, also are extremely variable. Pneumatic tires on automobiles are a very good example of such conditions. On the other hand, in applications such as transmission belts and autorail pneumatic tires, which operate under much more uniform conditions, there is reason for believing that systematic tests of this kind might be of some use.
Precision of Tests for Tear Resistance
Authors: Morris Ross E. , Bonnar Robert U. 
Published: February 2011

Abstract
The Winkelmann tear test with the crescent specimen has been widely used in the rubber industry. The American Society for Testing Materials has adopted this test, using two forms of the crescent specimen, with a single nick in each as recommended by Poules. Recently Buist demonstrated that the result obtained with the A.S.T.M. type B crescent specimen is very sensitive to the depth of the nick. He found that the same blade-setting did not make the same depth of nick in all stocks. To overcome this difficulty he developed a cutting machine in which the blade setting could be changed to secure, by cut and try, a nick depth of exactly 0.02 inch, as specified by the American Society for Testing Materials. Just previous to the publication of Buist's work, a paper by Graves described tests on an angle-tear specimen, and gave data and observations to show that this specimen had the following advantages over the crescent specimen: 1. No nick is required. 2. Test results are more reproducible. 3. Pulling stress is more concentrated at the point of rupture.
Correlation of Laboratory and Service Abrasion Tests of Rubber Tire Treads
Authors: Juve A. E. , Fielding J. H. , Graves F. L. 
Published: February 2011

Abstract
There appears to have been no substantial improvement in the degree of correlation between laboratory abrasion tests and service tests on rubber tires since the 1931 Symposium on Abrasion Testing of Rubber. The limitations with respect to compounding variations are essentially the same today as then. The data on rubber products other than tires are too few to permit any conclusion to be drawn. The reasons for the failure of laboratory tests to correlate with road results are many and varied. Some of these are listed in this report. They represent not only weaknesses in the laboratory procedures but also difficulties in standardizing service tests. A better laboratory test method should incorporate the following features: 1. Cushion the test-specimen to minimize the modulus effect. 2. Provide means to prevent gumming of the abrasive. 3. Provide means to conduct the test over a range of temperatures. 4. Slow the rate of wear, partly by abrading intermittently and partly by use of less load and duller abrasive. 5. Use a test-specimen of a size which can be cut from a tire tread if desirable.
The Brabender Plastograph in the Rubber Laboratory
Authors: Juve A. E. , Hay D. C. 
Published: February 2011

Abstract
With suitable modifications the Brabender plastograph can be used to advantage in studying, on a small scale, the factors which influence the changes in consistency of rubbers during their mastication. Typical results reported herein show that the temperature coefficient of the rate of breakdown for natural rubber is 1.47 and for GR-S, 1.36. The rate of softening of butadiene-styrene copolymers is shown to depend, among other factors, on the original consistency of the rubber and the type of modifier used in polymerization. The influence of commercial peptizing agents on the rate of softening of natural rubber, GR-S, and GR-I at 150° C is shown. The reproducibility of the mastication test was found to be good.
Spontaneous Coagulation of Hevea Latex
Authors: Van Gils G. E. 
Published: February 2011

Abstract
Fresh Hevea latex can only be kept fluid for a few hours. After tapping in the morning, one observes a thickening of the latex in the afternoon, and in the evening the whole mass is coagulated. This coagulation may begin sooner or later, depending on circumstances. Contamination with rain water running along the bark of the tree may cause the latex to spoil during collection. Several investigators have tackled the problem, but no theory has been able to account fully for the facts observed. The most obvious explanation that coagulation occurs as a result of acidification cannot hold, as the acidity does not drop below pH 6.0–6.3, an observation which has been made by several authors. Even if the pH is held constantly at 7.0 by adding continuously small amounts of sodium hydroxide, spontaneous coagulation is not prevented or retarded. It is obvious that in the hours after tapping several changes take place in the latex. Spoon showed that the potential acidity, i.e., the amount of alkali needed to neutralize the latex, increases. Ultee and van Dillen proved the formation of carbon dioxide. Schrieke made extensive experiments on this subject, and reached the conclusion that carbon dioxide leads to an increase of the potential acidity but that the spontaneous coagulation is not affected by it.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. V. Rubber Vulcanization
Authors: Bloomfield G. F. 
Published: February 2011

Abstract
Data presented for a range of vulcanized rubbers prepared under different conditions show that, while olefinic unsaturation becomes reduced by vulcanization in the proportion of one double bond for each sulfur atom combined with a C5H8 unit, the original H/C ratio of 8/5 is not altered. The loss of unsaturation is somewhat modified when zinc oxide or certain accelerators also are present. Oxygen has a slight inhibiting effect on vulcanization; hydrogen sulfide and thiols markedly catalyse the vulcanization reaction without, apparently, affecting the efficiency of the sulfur cross-linking reaction. In confirmation of the results of Hull, Olsen, and France, a small proportion of zinc oxide or a soluble zinc soap promotes a reaction between sulfur and mercapto groups whereby di- and polysulfides are formed with liberation of hydrogen sulfide. The same type of activity is shown by some of the nitrogenous accelerators commonly used in rubber vulcanization. Substantial conversion of mercapto groups into polysulfide linkages is, therefore, to be expected when vulcanization is conducted in the presence of these auxiliary substances.
Sulfur Bond in Vulcanizates. Vulcanization by Dithiols
Authors: Hull C. M. , Weinland Louis A. , Olsen S. R. , France Wesley G. 
Published: February 2011

Abstract
The expected vulcanizing activity of dithiols has been demonstrated. It seems likely that mill scorching results from peroxide-catalyzed thiol addition; milling at higher temperatures would tend to inhibit reaction by destroying peroxides. The development of considerable tensile strength in stocks containing dithiols and the gelling of cements by dithiols give strong support to the thiol addition reaction as a feasible step in sulfur vulcanization, as proposed in the first two papers of this series.
Some Thermodynamic Properties of High Polymers, and Their Molecular Interpretation
Authors: Gee Geoffrey 
Published: February 2011

Abstract
The past decade has witnessed a rapid growth in the understanding of the thermodynamic properties of polymers and their solutions. This has been achieved largely by the development of statistical theories of rubberlike elasticity and of the free energy of mixing of polymers with liquids. A number of reviews are available dealing with portions of this field of work, but for the most part they are addressed to specialist workers. The object of this review is to survey in broad outline a number of related topics, without entering into detailed discussion of statistical theories. The emphasis is, therefore, laid on the experimental thermodynamic data which form the basis for these theories, and on their physical significance. An attempt is made to develop the argument as far as possible in physical terms, although it must be realized that this is essentially a field in which we are concerned with quantitative measurements and their mathematical interrelations. One fundamental experimental difficulty which is common to nearly all the problems to be discussed below is that of ensuring that the system under investigation has reached a state of equilibrium. The significance of the concept of equilibrium in measurements on polymers has recently been very clearly discussed by Ubbelohde. The difficulty arises from the fact that many processes in a polymer take place so slowly that they may to a good approximation be said not to occur at all during the time involved in an experiment. When this is the case, it is clear that the system cannot be assumed to reach a state of equilibrium with respect to this particular process. It is, indeed, common to find that certain properties of a polymer depend greatly on the previous history of the specimen; examples will be given later. Even when this is the case, the system may still be in equilibrium with respect to other possible changes, and it is, therefore, permissible to apply the thermodynamic criteria of equilibrium. Care is needed in relating the experimental results to theories to make sure that the theory is not based on the assumption of equilibrium with respect to changes which are so slow as to be virtually negligible. The usefulness of considering partial equilibria in this way depends on the possibility of choosing a time scale for the experimental work long enough for the rapid processes to be complete, and at the same time short enough to exclude other slower processes.
Structure of Chloroprene Polymers as Determined by Ozonolysis. XI
Authors: Klebanskiĭ A. , Chevychalova K. 
Published: February 2011

Abstract
1. Chloroprene polymers obtained by various methods of polymerization (with a regulator, in emulsion, thermally at 80° C) and a liquid chloroprene polymer were subjected to ozonolysis. 2. Succinic acid was formed in all the experiments, as the main decomposition product of the ozonide, in quantities from 82 to 96 per cent of the carbon skeleton, 3. Decomposition of the ozonides was effected with absolute alcohol containing hydrogen chloride gas, with and without the addition of orthoformic ester, with the aim of establishing the relative arrangement of the units. The diethyl ester and the acetal of succinic acid, as well as the ethyl ester of the dimer or a mixture of the monomer and the trimer of β-formylpropionic acid, were obtained. The structure of this product requires further investigation. 4. In spite of the many different methods used, the presence of succinaldehyde could not be detected either in the α-polymer obtained with the aid of a regulator or in the other polymers. 5. Control of the ozonolysis was accomplished by quantitative change of the bromine numbers during ozonolvsis : the consumption of bromine appeared to be constant up to a critical point corresponding to the end of the ozonolysis; at this point the bromine numbers fell off sharply. 6. It was found that the consumption of bromine occurred chiefly at the expense of the substitution reaction, which was indicated by the evolution of hydrogen bromide. 7. Based on the data, it is believed that the chloroprene polymers obtained by different methods possess a substantially normal structure of a macro-molecule with units arranged in the 1,4-1,4 position. 8. The low yield of succinic acid (85 per cent from chloroprene polymerized in emulsion) and the incomplete balance (89.3 per cent instead of 97.78 and 99.58 per cent) when polymerized in a mass were caused by the insufficient purification of the insoluble μ-polymer from the emulsifier and other admixtures constituting the ingredients of the emulsion. 9. In a similar way, the low yield of succinic acid (82.16 per cent) and the incomplete balance of the experiment (87.66 per cent) when the liquid batch of the polymer obtained in the presence of a regulator was ozonized depend, probably on the presence of the reaction products of the polymers with the regulator which were not accounted for or investigated in detail. The latter polymers will be investigated at a later date.
X-Ray Investigation of the Crystallization of Vulcanized Rubber on Stretching
Authors: Lukin B. V. , Kasatochkin V. I. 
Published: February 2011

Abstract
1. x-Ray methods have been used to investigate the amount of crystalline phase in stretched samples as a function of the vulcanization time. 2. Curves relating the percentage of crystalline phase to the vulcanization time have sharply defined maxima. 3. A comparison of the curves relating tensile strength to vulcanization time with the curves of crystal formation shows their analogous character, the position of the maxima approximately corresponding to one and the same vulcanization time. 4. The position of the maxima on the curves of crystal formation is not related to the degree of stretching. 5. The effect of accelerators is to shift the maximum on the curve of crystal formation to the region of short vulcanization times and to increase the percentage of crystalline phase. 6. The curves of crystal formation and of tensile strength, and thus the behavior of the stress-strain curves for various vulcanization times, is interpreted from the point of view of the existence of two processes—the process of forming a network of cross-links by the interaction of rubber with sulfur, and the process of oxidative degradation of the rubber.
X-Ray Diffraction Study of Some Synthetic Rubbers at Low Temperatures
Authors: Hanson E. E. , Halverson G. 
Published: February 2011

Abstract
A certain amount of ordering has been found in “noncrystalline” synthetic rubbers, which were studied by the use of the technique of cooling the raw polymer before it is elongated and freezing it immediately after stretching to prevent relaxation. Polybutadiene and polydimethylbutadiene, whose monomer units were structurally symmetrical, displayed the greatest degree of ordering. The presence of a high percentage of 1,2-units in sodium-polymerized butadiene destroyed almost all of the ordering observed in the emulsion polymer. GR-S and emulsion polybutadiene showed the presence of small amounts of crystallites, presumably of 1,4-addition polybutadiene, probably the trans-form. Polydimethylbutadiene showed the presence of crystallites presumably of 1,4-addition in the cis-form. The intermolecular distance between the extended chains increased with increasing amounts of side groups. The departure of the Bragg angle spacing of the amorphous halo from the corresponding quantity for the liquid monomer increased with increasing amounts of side groups.
The Quantum Yield of Oxidation of Hevea Rubber and GR-S
Authors: Hart E. J. , Matheson M. S. 
Published: February 2011

Abstract
The initial quantum yields of photoöxidation for purified Hevea rubber have been measured for various mercury arc lines in the wave length region 2537– 17,400 A˚. All experiments were carried out at room temperature and at an oxygen pressure of one atmosphere. At the outset of irradiation all quantum yields of combined oxygen are less than unity, although the quantum efficiency rises above 1.0 at 2537 and 3130 A˚. as photoöxidation proceeds. The low quantum yield suggests that in its initial stages (less than 0.1 per cent oxygen combined on the rubber) photoöxidation is not a chain reaction. It is postulated as the first step in rubber photoöxidation that the light activated rubber group reacts with oxygen to give a relatively stable intermediate which does not immediately dissociate to give a free radical reaction chain. The quantum yields of photoöxidation of purified GR-S were also measured under the same conditions as used for rubber. At each wave length the quantum yield was lower than for rubber, indicating formation of a stable intermediate in the initial reaction also.
The Mechanism of Reënforcement of Elastomers by Pigments
Authors: Cohan Leonard H. 
Published: February 2011

Abstract
Modulus appears to be independent of average particle diameter. With respect to the dependence of modulus on loading, calcium carbonate pigments which are symmetrical follow the equation derived by Guth and Gold for the relation between modulus and volume concentration of symmetrical inelastic particles. Up to about 80 parts by weight loading, HMF black follows a similar equation derived for rod-shaped particles, assuming a value of six for the ratio of the length to the diameter of the particles. The agreement with these theoretical equations is surprisingly good, and holds out the eventual possibility of calculating modulus over a wide loading range from tests at a single loading. Hardness and plasticity increase with loading in qualitative agreement with the equations. The behavior of modulus as a function of loading and average particle diameter of pigments indicates that vulcanized natural or synthetic rubber is not adsorbed in appreciable quantities or with sufficient force to be rendered inelastic at the surface of either calcium carbonate or carbon black pigments. Qualitative predictions based on the hypothesis that tensile strength is a measure of the force required to separate rubber chains from each other rather than to break rubber chains, and that pigment particles act as cross-linking agents holding the chains together, are in agreement with the behavior of calcium carbonate and carbon black pigments of widely different surface area over a considerable loading range.
Chromatographic Fractionation of Some Synthetic Elastomers
Authors: Landler Ivan 
Published: February 2011

Abstract
Mark and Saito were the first to fractionate a high polymer (cellulose acetate) by chromatographic adsorption on blood carbon. They found that molecules of low molecular weight were adsorbed first, and that the mean molecular weight of the product which remained unadsorbed was higher than the original molecular weight. Levi and Giera confirmed this result, but did not succeed in fractionating Buna-S or polyisoprene, for these polymers were eluted by the solvent during the washing operation in the column. The present authors have carried out further experiments in this field with a study of three commercial synthetic elastomers, viz., GR-S (butadienestyrene copolymer), Perbunan-N (butadiene-acrylonitrile copolymer), and Visitanex (polyisobutylene). The polymer was adsorbed by starting with a poor solvent composed of a mixture of toluene and methanol ; the quantity of alcohol added was just below the threshold of precipitation. The adsorbent used was a mixture of 75 per cent of lamp black (80 square meters per gram) and 25 per cent of coarse active carbon. The latter served to prevent agglomeration of the lamp black. The adsorbent was divided into three layers, of 10 grams each. At the end of the tube was a filter of fritted glass. Filtration was carried out under pressure, the rate of flow thereby being maintained constant, The polymers were characterized by their intrinsic viscosities. The molecular weights which were estimated by means of the relation, found experimentally between the molecular weight and viscosity, are only approximate, for this relation holds true only for narrow fractions.
Vulcanization of Synthetic Rubbers by the Peachey Process
Authors: Bekkedahl Norman , Quinn Fred A. , Zimmerman Elmer W. 
Published: February 2011

Abstract
The Peachey process, which vulcanizes natural rubber by subjecting it alternately to sulfur dioxide and hydrogen sulfide gases, has been found to vulcanize the more common synthetic rubbers. The polymer studies were natural rubber, GR-S; GR-M, GR-I, GR-A, Hycar OR-15, Hycar OR-25, Hycar OS-10, Hycar OS-20, and Hycar OS-30. Good cures were obtained with all of the polymers except GR-M. None of the synthetic rubbers cured any faster than natural rubber. The nitrile and the styrene copolymers of butadiene cured at about the same rate or somewhat slower. GR-I required roughly 50 times as long as natural rubber for an equivalent cure, and GR-M required even longer.