bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Molecular Weights and the Structures of Rubber, Gutta-Percha and Balata. Communication No. 258 on Macromolecular Compounds. Communication No. 49 on Isoprene and Rubber
Authors: Staudinger H. , Fischer Kl 
Published: February 2011

Abstract
The method used to determine the constitutions of rubber, gutta-percha and balata is essentially the same as that used for organic substances of low molecular weights, i.e., the substance is dissolved in a solvent, and the size and character of the particles in solution are determined. For a long time the nature of colloidal solutions of these hydrocarbons was in dispute. Up to twenty years ago, it was commonly assumed that the molecules of these hydrocarbons are relatively small, and that their colloidal particles are formed by the assemblage of small molecules into micelles through the agency of secondary forces. It seemed to Pummerer, Nielsen and Gündel that in certain solvents, such as camphor and menthol, rubber is dissolved in a low-molecular state. Subsequently, however, this observation was proved to be incorrect. According to the opinion of Meyer and Mark, colloidal particles of rubber are composed of relatively long primary-valence chains, which contain from 75–150 isoprene residues. These chains are, in turn, assembled into micelles by “micellar forces.” The authors explain this in the following way: “The high viscosity of rubber solutions, e.g., in benzene, would lead one to conclude that very large, highly solvated micelles are present in these solvents.” At the time, this hypothesis seemed to explain quite satisfactorily the nature of rubber and its solutions, for the great tendency of these solutions to undergo certain changes on standing, which are manifest by an increase or decrease in viscosity, is readily comprehensible on this basis.
The Constitution of Butadiene Polymers. Communication No. 259 on Macromolecular Compounds. Communication No. 5o on Rubber
Authors: Staudinger H. , Fischer Kl 
Published: February 2011

Abstract
When butadiene is polymerized, the resulting polymers are composed of macro-molecules which have branched structures. The actual linking of butadiene molecules to form polymers may proceed in different ways. Not only can linking take place at the 1,4-position (see Formula 1) or at the 1,2-position (see Formula 2), but an addition reaction can take place at the 1,2- and 1,4-positions (see Formulas 3a and 3b). As a result, extensively branched molecules are formed, for the lateral chains unite by means of their double bonds with more butadiene molecules, either in the 1,2-position or in the 1,4-position. Finally it is not impossible that, to at least a small extent, two butadiene molecules unite directly, in accordance with a diene synthesis, to form vinylcyclohexene, which, after activation of its double bonds, reacts with more butadiene molecules in the 1,2-position or in the 1,4-position. Technically, butadiene was at first polymerized with sodium (Bunas with numerical designations), but today it is polymerized chiefly in the emulsified form5, and this process is used also to prepare mixed polymers (Bunas with letter designations). In the investigation to be described, this latter group of Buna rubbers was not studied, because in most cases they are insoluble, or swell only to a limited extent, and therefore it is impossible to determine either the size or the shape of their macromolecules, as can be done with soluble sodium polymers and emulsion polymers.
Permeability in Relation to Viscosity and Structure of Rubber
Authors: Barrer Richard M. 
Published: February 2011

Abstract
Some properties of flow of solutes in and through rubbers are outlined. These properties indicate that, due to fluctuations of thermal energy, activated zones exist in certain polymers, of which viscous flow and diffusion are a consequence. A simple statistics of activated zones has been given, and from it equations are obtained for ΣN, D, Ds, and η, denoting respectively the total number of activated zones in rubber, the diffusion constant of simple solutes in the polymer, the self-diffusion constant of rubber, and its viscosity. Functional relations are predicted between log Do, log ηo, or ΔS* (the entropy of activation) and the Arrhenius energy of activation for diffusion or viscous flow. The available data clearly demonstrate this relationship. They also indicate no discontinuity between rubbers and liquids as diffusion media.
Chemical Reactions during Vulcanization. III
Authors: Hauser E. A. , Sze M. C. 
Published: February 2011

Abstract
From the preceding discussion the following conclusions may be drawn: A. Vulcanization with Sulfur in General 1. Vulcanization with sulfur is fundamentally a chemical change involving activated sulfur and organic double bonds. 2. Sulfur must decompose from S8 (in the form of an eight-membered ring) to smaller molecular units, perhaps to S2 and S1 before it can be activated and react. 3. The ratio of atoms of sulfur combined to the number of double bonds lost is not restricted to one atom of sulfur for each double bond, but may have other values, which depend on the conditions and the reactions involved. B. Factice Formation 1. The rate of reaction of sulfur with tung and linseed oils is greatly influenced by small proportions of such agents as zinc oxide and mercaptobenzothiazole. 2. Combination of sulfur with the conjugated double bonds of the eleostearic acid in tung oil takes place at the terminal carbon atoms of the conjugated system, giving a typical 1,6-addition. 3. The following possible chemical reactions explain adequately the process of factice formation from tung and lineseed oil. Under different conditions different reactions predominate.
Curing Rate of Rubber. Effect of Phosphate Buffer Mixtures on the Rate of Cure of Crepe Rubber
Authors: Newton E. B. 
Published: February 2011

Abstract
The phenomenon of variability in the rate of vulcanization of crude rubber by sulfur and heat has been studied by rubber technologists for more than forty years. Whether early workers recognized differences in any particular commercial grade is difficult to say, as a result both of the lack of discriminating tests and of the secrecy which was formerly maintained in the industry. However, three developments, all coming near the beginning of this century, combined to make workers more aware of any differences which might exist: (1) Weber's work on the chemistry of rubber, which led to the first theory of cure and to the idea of the sulfur coefficient of vulcanization; (2) the wider availability and use of standardized tensile testing machines, although earlier but limited use of such machines was known; and finally, (3) the rise of the plantation industry in the Middle East. The first two of these developments supplied methods of sufficient accuracy to detect differences other than by the empirical comparisons of hand tests. The third gave rise to many investigations designed to ascertain differences between the newer plantation and the standard Para grades.
Physical Properties of Polystyrene as Influenced by Temperature
Authors: Carswell T. S. , Hayes R. F. , Nason H. K. 
Published: February 2011

Abstract
The physical properties of plastics are markedly influenced by the ambient temperature, but comparatively few quantitative data on polystyrene have been published. The variation of flexural strength and deflection at break for compression-moulded polystyrene and for a number of other compression-moulded plastic materials at temperatures from —70° to +200° C was described by Nitsche and Salewski. Jenckel and Lagally determined the tensile strength of extruded polystyrene filaments at 30° to 60° C. The elongation at 20° to 90° C was reported for extruded and racked polystyrene foil by Müller. Since the mechanical properties of plastic materials are profoundly influenced by the methods used in preparing the test specimens, data on such properties are meaningless unless the details of preparation also are known. This paper describes variations in some of the mechanical properties of injection-moulded polystyrene over the range from —75° to +100° C. This method was chosen because injection moulding is by far the most commonly Used commercial process for the fabrication of polystyrene.
Structure of the Butadiene-Methacrylic Nitrile Copolymer
Authors: Alekseeva E. N. 
Published: February 2011

Abstract
In the joint polymerization of butadiene and methacrylonitrile, the bulk of the polymer consists of macromolecules, in which the two unit components correctly alternate, and the butadiene combines in its 1,4-position. Only much fewer macromolecules are encountered in which several molecules of butadiene consecutively intercombine in 1,4-positions.
Rubber, Polyisoprenes, and Allied Compounds. I. The Synthesis of Low-Molecular Polyisoprenes of the Rubber and the Squalene Type
Authors: Farmer Ernest Harold , Sutton Donald A. 
Published: February 2011

Abstract
A synthesis for dihydrofarnesene, H⋅[CH2⋅CMe:CH⋅CH2]3⋅H, has been devised which appears to be capable of utilization in the formation of other low-molecular dihydropolyisoprenes, H⋅[CH2⋅CMe:CH⋅CH2]n⋅H, in which the individual isoprene units are uniformly arranged in head-to-tail fashion. This synthesis, starting from geraniol, gives a triene hydrocarbon which differs in one of its additive properties from a product described as dihydrofarnesene in the literature. The reason for the difference has been investigated. A new synthesis for squalene has been devised which appears to be capable of utilization in the formation of other symmetrical dihydropolyisoprenes, H⋅[CH2⋅CMe:CH⋅CH2]n⋅[CH2⋅CH:CMe⋅CH2]n⋅H, of the squalene type. This starts from geranylacetone and the Grignard derivative from 1,4-dibromobutane.
Physical-Chemical Investigations of Artificial Rubber
Authors: Springer A. 
Published: February 2011

Abstract
Among the physical methods of which use has been made to explain the structure of organic compounds, thermal measurements, particularly measurements of heats of combustion, have played a particularly important part. With the aid of data on heats of combustion, it is possible to draw conclusions on the energy relations within molecules and on the heat tones of chemical transformations. Such measurements have been carried out on highly polymeric substances. In some cases, the object was to study the reactions of formation. e.g., polymerization; in other cases it was to explain the transformations which high polymers themselves undergo. Studies of polymerization reactions by thermal methods have shown that, in distinction to monomers, a decrease in the heat of combustion with increase in the degree of polymerization is to be expected. The polymerization process is accordingly exothermic, and the difference between the heats of combustion represents the heat of polymerization which is liberated. A direct comparison of heats of polymerization found experimentally by different investigators is, however, not possible because, in most cases, no information on the degree of polymerization, branching of the chain molecules, or other significant properties of the polymers are given.
Rubber in Vibration
Authors: Gehman S. D. 
Published: February 2011

Abstract
In most of the uses to which rubber is put, it is subjected to deformations which are relatively small compared to the ultimate deformation of which the rubber is capable. For many products, such as vehicle tires, motor mountings, and belts, the deformations are periodic. There is, therefore, a great deal of interest attached to the physical properties of rubber when measured under vibratory, as contrasted to static, conditions. The use of rubber in mountings for the absorption or isolation of vibration, with which this paper is principally concerned, has led to a number of systematic investigations of its static properties from the standpoint of the engineer who might be interested in employing it for such purposes. As representative of such contributions may be cited the work of Keys, Smith, Brown, Haushalter, Hirshfeld and Piron, and Kimmich. The principal concern was to determine the rules which govern the deformation of rubber pieces of various sizes, shapes and hardnesses. Related questions of permanent set, creep, and the effect of temperature also came into the discussion. The importance of dynamic measurements was realized, but information on this phase of the subject was beyond the scope of the work.
Analytical Methods in Rubber Chemistry. Part V. Estimation of the Oxygen of Highly Autoöxidized Rubber Contained in Carboxyl, Ester, Carbonyl, Epoxide and Hydroxyl Groups
Authors: Hilton F. 
Published: February 2011

Abstract
In the course of a study of the autoöxidation of natural rubber and of low-molecular olefins of allied structure, it has been necessary to ascertain the nature and relative proportions of the functional groups to which the ingoing oxygen may give rise. Up to the present it has been established that the products of autoöxidation reactions are in general highly complex mixtures, and that even such simple olefins as dihydromyrcene and cyclohexene may give rise to molecules which bear a varied assortment of hydroperoxide, alcoholic hydroxyl, epoxide and carbonyl groups. Available evidence further indicates that the primary products of autoöxidation are hydroperoxides, formed by the reaction of oxygen at methylene groups adjacent to double bonds, and that it is the secondary reactions which these hydroperoxides undergo which are responsible, directly or indirectly, for the formation of the other oxygen-containing groups which have been observed. Molecules of rubber hydrocarbon contain, on an average, several thousand methylene groups adjacent to double bonds. Each such methylene group is at least the potential seat of oxidative attack, and it might be anticipated that if the autoöxidation of rubber proceeds in a manner analogous to that of simpler olefins, the products of reaction would be extremely complex and that they might contain any or all of the following functional groups
Aging of GR-S Vulcanizates in Air, Oxygen, and Nitrogen
Authors: Shelton J. Reid , Winn Hugh 
Published: February 2011

Abstract
The results of aging GR-S vulcanizates in air, oxygen, and nitrogen show: 1. The decrease in tensile strength observed in both bomb and oven aging is caused by the action of oxygen. 2. The modulus increase obtained in the oxygen bomb at 80° C is not caused by oxygen in the aging atmosphere. 3. At 100° C in air, more than half of the hardening, measured by the modulus increase obtained after five days, may be attributed to the action of oxygen. It therefore appears that oxygen acts on GR-S vulcanizates in two distinctly different ways: 1. A reaction leading to tensile breakdown, which no doubt involves chain scission. This reaction takes place at both 80° and 100° C, and is effectively retarded by the antioxidant, phenyl-β-naphthylamine. 2. A reaction producing a stiffening of the GR-S, as shown by the modulus increase. This stiffening suggests the formation of polymeric products—for example, by cross-linkage. This reaction was not observed at 80° C, but was a major factor in the aging at 100°, and was little affected by the antioxidant employed.
Pigment Incorporation in GR-S through Latex
Authors: McMahon W. , Kemp A. R. 
Published: February 2011

Abstract
The physical properties of GR-S gum stock are decidedly inferior to those of natural-rubber gum stock, and they have to be greatly enhanced for practical use of the elastomer. At present these physical properties are augmented to the greatest degree by compounding with reinforcing pigments, especially carbon blacks. Furthermore, experience has shown that, for a given pigment, the reinforcement it affords is proportional to the degree to which it is dispersed in the elastomer. A thorough dispersion of pigment on the mill or in the Banbury mixer is not feasible with schedules which can be applied in the factory, particularly with those pigments which are more difficult to disperse. A study of the relation between the characteristics of pigments used as fillers in GR-S and their reinforcing properties indicated that the particle size of the pigment was the predominant characteristic associated with reinforcing ability. The finer carbon blacks yielded the greatest reinforcement, measured by ultimate tensile strength; also, a fine grade of magnesium oxide yielded compounds with tensile strengths approximately equal to stocks made with blacks of the same particle size. Stocks made from a coarser magnesium oxide were considerably lower in tensile strength, and zinc oxides and calcium carbonates fell roughly in the order of their particle sizes. The calcium carbonates, zinc oxides, and magnesium oxides had to be worked on the mill much more than the carbon blacks to develop maximum reinforcement; and, even though well worked, the finest zinc oxide and calcium carbonate did not yield compounds with properties which their particle size indicated they should have. It was felt that this was due to inability to disperse these materials properly on the mill; thus their effective particle size in the compound was much greater than their ultimate size. Accordingly, a better means was sought to disperse fillers in GR-S than that afforded by milling. It was known that excellent dispersions of pigments could be made in water with the aid of dispersing agents. It was also reported that the polymer particles in GR-S latex were very finely divided, less than one-tenth the diameter of particles in natural rubber latex. If, then, a water suspension of well dispersed pigment was mixed with latex, and the filler and polymer were precipitated or coagulated simultaneously, it was thought that the pigment might be more thoroughly dispersed in polymer than it would be through dry milling; the physical properties of compounds made in this manner should then show improvement over those made on the mill.
Incorporation of Carbon Black into GR-S Latex on a Production Scale
Authors: Rongone Ronald L. , Frost Charles B. , Swart Gilbert H. 
Published: February 2011

Abstract
1. A commercially feasible method for adding carbon black to latex has been developed and tested. The black-latex mixture can be handled in essentially the same way as normal GR-S throughout the various steps of coagulation, washing, drying and baling. 2. By incorporating black into GR-S latex, an increase in milling capacity of about 35 per cent is possible. 3. The total power required for mixing this black-rubber is at least 20 per cent less than for tread stock mixed in the conventional way. 4. Mixing temperatures are lower for latex-black stocks. 5. Physical properties and preliminary tire tests show that carbon black incorporated with the latex produces stock equivalent in physical properties to stocks prepared by mixing carbon black into dry rubber. 6. Considerable savings are made possible by the use of this method. 7. The amount of dirt now present in the millrooms of the rubber manufacturing plants should be greatly reduced.
Effect of Moisture on Curing Rate of GR-S
Authors: Braendle H. A. , Wiegand W. B. 
Published: February 2011

Abstract
1. Moisture content of uncured GR-S compounds must be reckoned with because of its effect on curing rate and the serious consequence of overcure. 2. Excessively dry polymer (below about 0.15 per cent water) will, in general, be slow curing (Figure 2). 3. Mixed stock with less than 0.5 per cent water will, in general, be slow curing and erratic in curing rate (Figure 5). 4. The normal moisture range of carbon black does not affect the curing rate of GR-S (Figure 4). 5. The normal moisture content of carbon black is not available to the polymer for stabilizing its curing rate. 6. Mixed stock which is dry and slow curing may be conditioned to stable curing rate by storage under humid conditions. A moisture content of 0.5 to 1.0 per cent is indicated. This moisture content seems also to iron out differences in curing rate between polymers. 7. Since conditioning of mixed stocks is not always feasible on the factory scale, the stabilization of cure by direct water addition during mixing should be given consideration. 8. Laboratory-scale tests on a GR-S tread compound indicate that an addition of about 2.5 to 5 per cent water (on the polymer) during mixing will result in a mixed-stock moisture content giving minimal cure variation for normal-curing and slow-curing (very dry) polymers for periods of stock layover up to about 3 weeks. 9. Any additions of water as suggested above will, on the factory scale, require adjustment, since moisture retention is a function of the compounding ingredients, mixing cycle and temperature, storage time, and humidity conditions actually obtaining.
Effect of Elastomer Crystallization on Tests for Freeze Resistance
Authors: Forman Don B. 
Published: February 2011

Abstract
At subzero temperatures cured elastomers become stiff and may or may not become brittle. As stiffness increases, elasticity decreases and stress at any given elongation increases. Brittleness occurs when the elastomer reaches an inelastic state. Both time and temperature of exposure are important factors which affect these changes in properties. Under any given testing methods, the degree of stiffness and conditions of brittleness are intrinsic properties of the elastomers and their compounds. Summaries of these factors have been given by Liska and Graves and Davis. Crystallization, which explains some of the results to be described, has been known for a long time to occur in rubber. Factors influencing the crystallization of rubber were investigated by Bekkedahl. He concludes that the crystals formed during the freezing or the stretching of rubber are identical. It is believed that this is true for crystallizable elastomers. Carothers and coworkers and later Sebrell and Dinsmore reported that the x-ray pattern of Neoprene (polychlorobutadiene) crystals obtained on stretching resembles those of rubber. Wood showed that Neoprene, like rubber, crystallizes at low temperatures. The most favorable temperature for Neoprene Type GM appears to be 0° C, and Neoprene Type FR shows no crystallization at low temperatures. Some properties of the latter at low temperatures were reported by Yerzley and Fraser.
Morphology of Latex Particles as Shown by Electron Micrographs
Authors: Hendricks S. B. , Wildman S. G. , McMurdie H. F. 
Published: February 2011

Abstract
Morphological features of particles from latices of sixteen plant species were studied by means of electron micrographs, a number of which are reproduced. The smallest particles have about the volume required to contain a very small number of molecules. Evidence is given for both form-retaining and fluid properties of latex particles. Difficulties with the hypothesis that these particles have fluid interiors covered by a surface film of gel rubber are pointed out. A new hypothesis accounting for the observed properties is advanced. According to it, the latex particles contain rubber molecules entwined as if they were odd lengths of string with other latex components held between the meshes.