bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Infrared Absorption Spectra to Studies of the Oxidation of Sodium-Butadiene Rubber
Authors: Dogadkin B. , Kasatochkin B. , Klauzen N. , Smirnova A. 
Published: February 2011

Abstract
The reaction of rubber with molecular oxygen explains well the structural changes which take place in rubber during aging and during a number of important technological processes, such as plasticization and vulcanization. Furthermore, during vulcanization, in addition to its reaction with the vulcanizing agent, rubber also reacts with oxygen contained in the mixture. This may be one of the reasons for an optimum point of vulcanization. However, it is difficult to explain the changes of physical properties of rubber by simple union of oxygen, with formation of oxygen-bearing groups. To account for the changes observed, addition of a large quantity of oxygen would be necessary, whereas actually notable changes are brought about by the absorption of only 2–3 per cent of oxygen. To explain this, it must be assumed that oxygen causes structural changes in rubber and that these changes become evident when the percentage of oxygen in the reaction products is still negligible. In the case of sodium-butadiene rubber, as was shown by one of the authors, this reaction at any particular temperature causes an increase of strength and of elasticity, and a loss of solubility. The object of the present investigation was a qualitative and limited quantitative analysis of those groups which originate during oxidation and also an examination of the structures which determine the changes of the physical and chemical properties in the reaction of rubber with molecular oxygen.
Interaction between Carbon Black and Polymer in Cured Elastomers
Authors: Stearns R. S. , Johnson B. L. 
Published: February 2011

Abstract
This research was initiated to determine whether the interaction at the interface between the surface of finely divided solids, such as carbon black, and cured elastomers is primarily physical or chemical in nature. Further, it was desired to correlate some physical property of the reinforced stock with the surface properties of the solid pigment. Through an examination of the thermodynamic changes accompanying the deformation of loaded stocks it is shown that physical adsorption of the van der Waals type occurring at the interface between pigment and polymer is inadequate to account for the experimental observations. However, if chemical bonding occurs at the interface between polymer and pigment, then the entropy of deformation of the stock may be correlated with the extent of this bonding. By a calorimetric method it was demonstrated that the surface of a carbon black particle contains sites that react with bromine to liberate the same amount of heat as low molecular-weight olefins. It is, therefore, proposed that a carbon black particle be considered as a disordered agglomerate of polymeric benzenoid type molecules which contain around their perimeters various functional groups. The existence of olefinic-type unsaturation on the surface of carbon blacks suggests strongly that, in the case of carbon blacks, the polymer and pigment are combined chemically through pigment-sulfur-polymer bonds into a continuous three-dimensional cross-linked matrix.
Permanganate Oxidation of Polybutadiene Rubbers
Authors: Naples F. J. , D'Ianni J. D. 
Published: February 2011

Abstract
In view of the failure to obtain quantitative yields of the expected carboxylic acids by permanganate oxidation of the several butadiene polymers studied, definite conclusions about their structures cannot be made. The results have a qualitative significance, however, in that the −10° emulsion polymer was found to produce a larger amount of succinic acid than the 50° emulsion polymer and less tricarballylic acid, and thus they correlate with general thinking that lowered temperature of polymerization results in a polymer of more regular structure and less branching. The Alfin polymer, although prepared in a system entirely different from the emulsion system, gave results which indicated a microstructure similar to that of 50° emulsion polybutadiene. Sodium polybutadiene was less completely characterized than the others, but the large amounts of carbon dioxide and β-carboxyadipic acid isolated correlated well with the high percentage of external double bonds known to be present from other methods of analysis.
Direct Reinforcement of Natural Rubber Latex Mixes
Authors: Le Bras Jean , Piccini Ivan 
Published: February 2011

Abstract
The direct utilization of latex has up to the present time been limited to a relatively small number of applications because of lack of knowledge of how to communicate to articles sufficient hardness, modulus, resistance to tearing, and resistance to abrasion. It is possible to obtain such properties by combining the molding of latex (thermosensitized by the action of trypsin) with the addition of partially condensed resins. Numerous types of resins can be utilized, but the best results have been obtained by resorcinol-formaldehyde resins. The mechanical properties of vulcanizates thus prepared are extremely high—for example, the tensile strength may reach 7500 pounds per square inch (with an elongation of 700 per cent), and the resistance to tearing 900 pounds per inch. Operating conditions that must be observed for the formation of the resin are described in detail, as well as the influence on the properties of vulcanizates of different factors: length of condensation of the resin, conditions of vulcanization, proportion of catalyst, molecular ratio of constituents, conditions of drying, etc. A new way is opened for obtaining vulcanizates of natural rubber of outstanding mechanical propoerties.
Retraction Test for Serviceability of Elastomers at Low Temperatures
Authors: Smith O. H. , Hermonat W. A. , Haxo H. E. , Meyer A. W. 
Published: February 2011

Abstract
Elastomer vulcanizates progressively stiffen as the temperature is lowered. Additional stiffening, due to crystallization, may occur as exposure to low temperatures is prolonged. The available methods of testing the low temperature flexibility of rubber and rubberlike materials do not reveal the losses in flexibility caused by crystallization except by using prolonged storage at low temperatures. A retraction test employing large deformations, which greatly increases the rate of crystallization, has been developed. This test rapidly gives a temperature index correlating with the stiffness of elastomer vulcanizates after storage at low temperatures, and can be used to measure the merit for low temperature applications of both crystallizable and noncrystallizable elastomers. This test in conjunction with conventional (room temperature) tests has been used successfully to study the low temperature performance of Hevea, GR-S, Paracril, and polybutadiene vulcanizates along with vulcanizates of many experimental elastomers. Correlation of results with cold compression set and hardness after low temperature storage has been excellent and substantiates the usefulness of the test.
Heats of Solution and Swelling of Some Synthetic High-Molecular Compounds
Authors: Tager A. , Sanatina V. 
Published: February 2011

Abstract
1. The heat of solution of a high polymer depends on the nature of the solvent as well as on the nature of the polymer. 2. The value and sign of the heat of solution of a polymer are related to the structure of the polymer and its mechanical behavior. For polymers which have relatively flexible chains, the heats of solution are negative ; for polymers which have relatively rigid chains, the heats of solution are positive. 3. The value and sign of the heat of solution indicate to a certain degree the change of the barrier potential of the polymer chain in any given solvent.
Relaxation Processes in the Deformation of Unloaded Rubbers and the Influence of the Degree of Vulcanization
Authors: Dogadkin B. A. , Reznikovskii˘ M. M. 
Published: February 2011

Abstract
1. It is shown that the process of stress relaxation at different initial elongations as well as the process of deformation at constant rate for unloaded rubbers at different temperatures (20–70° C) can be represented quantitatively by equations suggested in earlier works. Likewise the possibility of expanding the theories proposed for the kinetics of high-elastic deformation of spatial polymers is substantiated. 2. It is shown that the relaxation properties of soft unloaded vulcanizates of natural rubber and many synthetic rubbers do not undergo essential changes during vulcanization. 3. The conjecture is expressed that the invariability of the relaxation properties during vulcanization continues until the bonds of the spatial network are distributed sufficiently widely not to influence the activity or heat movement of the chain segments between them.
Dynamic Properties of Raw and Vulcanized Polymers
Authors: Enabnit R. S. , Gehman S. D. 
Published: February 2011

Abstract
Theoretical considerations made it probable that the usefulness of measurements of vibrational properties of vulcanizates to evaluate rubberlike qualities and heat generation under flexing might be extended to raw polymers if a suitable technique of measurement could be found. Such a technique was developed and correlations between dynamic properties of raw polymers and vulcanizates were studied. The test conditions, using low amplitude shear vibrations at 60 cycles per second, were such that effects due to plastic flow in raw polymers were suppressed and values of dynamic modulus and resilience were independent of plasticity. The data obtained showed a definite correlation between the dynamic properties of a series of raw polymers and those of vulcanized gum and tread stocks prepared from them. The effect of cure was measured throughout a range from the raw state to overcure for Hevea, polybutadiene, and butadiene- styrene copolymers. The ease of measurement, small quantity of material required, and the nature of the correlations observed indicate the usefulness of dynamic evaluations for raw polymers. Furthermore, it appears possible, with suitable background, to anticipate fairly well from raw polymer measurements the dynamic properties that can be achieved in a vulcanized compound.
Chlorination of Natural and Synthetic Polyisoprenes
Authors: Kraus Gerard , Reynolds W. B. 
Published: February 2011

Abstract
The extent of additive and substitutive chlorination was determined for emulsion polyisoprene, Hevea and gutta-percha chlorinated to different chlorine contents in darkness and in a nitrogen atmosphere. The maximum amount of additive chlorine that can be introduced into the polymer is 1.21 atoms of chlorine per isoprene unit for synthetic emulsion polyisoprene, 1.14 for Hevea. The chlorination involves a cyclization reaction by pairs, leading to isolation of reactive units. The loss in unsaturation due to cyclization has been calculated statistically by the method of Flory and Wall, and has been shown to be consistent with the total amount of additive chlorine in the fully chlorinated product. Cyclization takes place in the early stages of the chlorination simultaneously with the initial substitution. The theoretical limit of cyclization calculated statistically is 86.5 per cent of all isoprene units cyclized for natural rubber and 72 per cent for polyisoprene containing 10 per cent vinyl side chains. Iodine chloride titration gives fair results for samples of low chlorine content, but is not applicable to polymers containing much more than 35 per cent of chlorine. Knowing the degree of cyclization, the unsaturation can, however, be calculated for any polymer from the extent of additive reaction. Substitutive chlorination is catalyzed by oxygen and peroxide, additive chlorination by ultraviolet light. Cyclization is partially prevented by the increase in additive reaction. Under the combined effect of peroxides and ultraviolet radiation, chlorination can be carried to very high degrees.
Volumetric Oxygen-Absorption Test for Rubber Aging
Authors: Shelton J. Reid , Cox William L. 
Published: February 2011

Abstract
A volumetric oxygen-absorption test for aging of rubber has been investigated from the point of view of the effect of cure and the effect of mercapto-benzimidazole on the aging behavior. The test has also been evaluated by comparison with conventional air oven and oxygen bomb aging. A compounded but uncured Hevea black stock is more resistant to oxidation than the vulcanized material, but after a reasonable cure is obtained, further heating produces only a small change in the rate of oxygen absorption. The change in physical properties corresponding to a given amount of oxygen absorbed varies somewhat with time of cure in the initial stages, but after the absorption of 4 or 5 cc. of oxygen per gram of rubber, the changes in most physical properties are a direct function of the amount of oxygen absorbed. Neither time of cure nor the presence or absence of inhibitor has any significant effect on the subsequent rate of change in such properties as tensile strength and ultimate elongation for a given amount of oxygen absorbed. Oven aging data on identical time cures confirm the reported superiority of a combination of mercaptobenzimidazole with a conventional type of anti-oxidant. Oxygen absorption data reveal, however, that mercaptobenzimidazole causes a significant decrease in the rate of oxidation of a Hevea black stock, and thus it clearly functions at least in part as an antioxidant in the usually accepted sense. The deterioration of properties is, in general, proportional to the oxygen absorbed, except in the early stages of oxidation where the mercaptobenzimidazole stocks change somewhat less than the controls for a given amount of oxygen absorbed. When the cures are selected to give comparable initial properties, however, the change in tensile strength of the mercaptobenzimidazole stocks with amount of oxygen absorbed is essentially the same as for the controls, even in the initial stages. These data suggest that the observed protection imparted by mercaptobenzimidazole results from a combination of two factors: (1) the normal antioxidant activity of mercaptobenzimidazole, which reduces the amount of oxygen absorbed; and (2) an effect on the nature of the cure attained when mercaptobenzimidazole is present, such that the absorption of a given amount of oxygen in the early stages is not accompanied by as great a change in properties. Thus, it appears that the deactivating effect may be the result of the effect of this material on the vulcanization process rather than a direct effect on the oxidation process. A comparison of the effect of oxygen absorption, air oven, and oxygen bomb aging methods on changes in physical properties of Hevea black stocks shows that the results obtained by oxygen absorption and air oven methods (both at 100° C) are similar, but that the higher oxygen concentration of the oxygen bomb test (70° C and 300 pounds per square inch) apparently results in a higher proportion of chain scission when compared to cross-linking of the polymer chains.
Contribution to the Physical Chemistry of Hevea Latex. I. Metal Cations in Latex
Authors: Belmas Robert 
Published: February 2011

Abstract
Our knowledge of Hevea latex is still incomplete, and some problems, such, for example, as a study of its natural inorganic ingredients, have not been attacked. Some work of value has been done on the analysis of the ash from latex and on the influence of metals in solution on the colloidal stability of latex, but few facts are available concerning the physico-chemical state of these metals in the natural emulsion and their partition between the serum and rubber particles. The investigation which is described in the present paper is devoted to metal components which are capable of influencing, when in soluble form, the colloidal behavior of latex. These include potassium sodium, calcium, and magnesium and, under some conditions, iron. Copper and manganese were not studied in this work for they have been the object of numerous investigations, and these metals play in effect the part of powerful prooxygenic agents in the oxidation of rubber.
Application of Drop Analysis to the Detection of Compounding Ingredients in Rubber Mlxtures. II
Authors: Kulberg L. M. , Bloch G. A. , Golybkova E. A. 
Published: February 2011

Abstract
1. The method of drop analysis is of wide use in the testing of crude rubber mixtures. 2. Methods of detection of mercaptobenzothiazole, tetramethylthiuram disulfide, diphenylguanidine, sulfur, zinc oxide, and magnesium oxide were developed.
Qualitative Analysis of Rubber Mixtures. II
Authors: Burmistrov S. I. 
Published: February 2011

Abstract
In Part I, reactions by which it is possible to identify Neozone, aldol-α-naphthylamine, tetramethylthiuram disulfide, and diphenylguanidine, when present alone or in the form of simple mixtures with inorganic ingredients, were described. These reactions can serve for the determination of these ingredients in complex mixtures as well, provided that the mixtures are first separated in the pure state. Chromatographic separation on a strip of filter paper is especially suitable for this process. It should be remembered that it is always difficult to determine the various ingredients in finished rubber products when they have undergone chemical changes or decomposition under the influence of high temperatures. In many cases the decomposition products have not been examined, and this naturally has hindered qualitative analysis of the mixtures. For this reason a study of the behavior of various ingredients under actual conditions of vulcanization and from this the development of methods of qualitative analysis became necessary. The author has shown that diphenylguanidine decomposes with formation of aniline under these conditions; it is also well known that diazoaminobenzene forms aniline and aminoazobenzene forms diphenylamine. In certain cases a specific ingredient can be detected by means of its decomposition products. Thus the presence of diphenylguanidine in the original mixture can be established if aniline is detected in the rubber and there are no other ingredients in the mixture which give off aniline during decomposition. In this work methods of detecting Neozone in raw rubber, rubber mixtures, and finished rubber products and also methods of determining mercaptobenzothiazole, diphenylguanidine, diazoaminobenzene, and products of their decomposition are described.
Investigations of the Reversion of Vulcanized Rubber under Heat
Authors: Shankar Uma 
Published: February 2011

Abstract
(1) During reversion of a vulcanizate, the breakdown of cross-linkages, including those of polysulfides, predominates over any simultaneous reformation of cross-linkages. (2) The reverting modulus falls exponentially with time. (3) The calculated molar free energy of activation is 33.3 ± 1.7 kcal., irrespective of the temperature or the atmosphere of cure or the composition of the mix, and is sufficient to rupture an —S—S— bond. (4) The degree of cross-linking, estimated from the equilibrium swelling measurements in benzene, falls during reversion. (5) The exclusion of oxygen during curing does not prevent reversion if the temperature is high enough to supply the energy needed to break up the cross-linkages. (6) During reversion in nitrogen, hydrogen sulfide is freely evolved, and the C/H ratio rises above the value for C5H8. (7) Evidence for the formation and breakdown of polysulfides during reversion is provided by an increase in free sulfur and a decrease in combined sulfur during a given cure, and the methyl iodide reaction of the reverted vulcanizates.
The Action of Unsaturated Compounds on Natural Rubber in Solution. II. The Reaction Induced by Heat Alone
Authors: Delalande André 
Published: February 2011

Abstract
The addition reaction at an elevated temperature (170° C) of maleic N-methylimide with natural rubber in solution was studied. Attempts were made to apply the principles of kinetics to this thermal reaction with a view to understanding the nature of the reaction, but the complexity of the system made impossible any chance of attaining the results hoped for. A comparison of the fixation of acrylonitrile and that of maleic N-methylimide in the temperature range of 160°–200° C showed that the rates of these two reactions are in the ratio of 1 to 25–30. A determination of the unsaturation of the addition products showed that fixation is on the α-methylenic carbon atoms of the rubber hydrocarbon. Finally a mechanism of the reaction is proposed, in which free radicals play a part.
Effects of Antioxidants on Rate of Breakdown of Rubber during Mastication
Authors: Cotton F. H. , Lee K. O. 
Published: February 2011

Abstract
Piper and Scott milled rubber with and without the addition of 2 per cent of hydroquinone on a cold mill. They could not detect any difference between the rates of breakdown. Wren made similar observations, but undefined experimental errors might vitiate his interpretation that phenols do not retard mastication. Phenyl-β-naphthylamine, however, has been reported to retard the breakdown of rubber during mastication in an internal mixer at 160° C. It was, therefore, decided to make an independent investigation.
The Heat Sensitivity of Hevea Latex. I. The Action of Zinc-Ammonium Complexes
Authors: Cassagne Paul 
Published: February 2011

Abstract
Among the different processes for heat-sensitizing latex by the more or less direct action of zinc-ammonium complexes, one has the choice of inorganic and organic complexes. Among the inorganic complexes, zinc-ammonium nitrate seems to be the most effective. Prepared from a 5 N solution of zinc nitrate and 5 N ammonia, it gives good heat sensitization when a volume of 2 per cent, based on the volume of the latex, is used. Among the organic complexes, the formate and acetate are particularly to be recommended because of their great heat-coagulating power. Dicarboxylic amino acids give active compounds, but they are more troublesome. Fat acids containing double bonds, of the type zinc-ammonium undecylenate or the oleate, have the advantage of being applicable to the manufacture of sponge rubber, for the complex, because of its surface-active properties, acts both as a foaming agent and a heat-coagulating agent, and can be added at the moment of use or several hours earlier without difficulty. Thus, the range of heat sensitizing agents of the zinc-ammonium complex type is, in fact, reduced to two or three practical effective agents, namely, the formate and the acetate in the manufacture of solid objects, and the oleate in the manufacture of molded sponge objects. The stearate often used is much less effective.
The Heat Sensitivity of Hevea Latex II. The Process of Heat Sensitization of Degraded Latex
Authors: Cassagne Paul 
Published: February 2011

Abstract
The heat sensitivity of a naturally or biochemically degraded latex is due in large part to the presence of amino diacids liberated by the degradation of proteins. These acids alone are capable of forming zinc ammonium complexes; however, in the case of a highly degraded latex, the monoacids with zinc oxide form soluble salts which are capable of heat coagulating this latex, the chemical stability of which has been much weakened by the desorption of the proteins. The nature of the amino acids governs the solubility of zinc oxide and, consequently, the heat sensitivity of the latex under consideration. In order to complete this work, we would have to determine the behavior of zinc-ammonium complexes in the phenomenon of coagulation, and study their dissociation in the latex. Does coagulation take place by simple neutralization of the negative particles of rubber by the Zn(NH3)4 cation, or rather, as is believed by certain Dutch chemists, does the zinc hydroxide formed by dilution of the complex act in a particular colloidal state? The problem remains unsolved.