bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Survey of Resilience and the Development of Resilient Compounds
Authors: Shaw Robert F. 
Published: February 2011

Abstract
A study was made of the methods and machines used in measuring resilience and classified as of the impact, free oscillation, forced oscillation, or other type: A search of the literature revealed that resilience is affected by numerous factors, such as temperature, duration of loading, magnitude of stress, method of applying stress, amplitude, frequency, and energy losses during measurement ; by shape and thickness of the sample, and by the state of cure, amount and type of plasticizer, amount and type of fillers, and the type of elastomer used. A series of Neoprene compounds was compounded, cured, and tested to determine the effect of various classes of carbon black on the resilience of the Neoprene elastomer, which is the most resilient commercially made rubber material. The resilience was found to decrease as the carbon black particle size decreased. A second series of compounds utilizing 15, 25, 35, 45, and 55 parts of medium thermal carbon black based on the Neoprene were tested, and the results show that resilience decreases with increase in loading. A comparison of the physical properties of these compounds with those of the currently used natural-rubber packing shows that the former are superior for replacing the natural rubber in mechanisms. The Neoprene compounds possess better tensile strength, elongation, resilience, aging, and oil resistant properties than the rubber compound, but are slightly inferior in low-temperature flexibility.
Energy of Resilience and Abrasion Resistance. A Comparison of Reclaimed and Crude Natural Rubber
Authors: Upham F. N. 
Published: February 2011

Abstract
When laboratory-machine tests on rubber were first introduced as a routine procedure, the only tests made were the elongation and tensile at break. Later, the tests were extended to the measurement of the amount of work done in stretching and breaking the test-specimen, and the computation was based on the area under the stress-strain curve.
Vulcanization at High Pressures
Authors: Wilkinson C. S. , Gehman S. D. 
Published: February 2011

Abstract
A technique was developed for vulcanizing cylinders of rubber 0.5 inch in diameter and up to 1 inch long at pressures as high as 150,000 pounds per square inch, using a small laboratory press (8-inch square platens). The specially designed mold was made of alloy steel according to general principles from the high pressure work of Bridgman. It was prestressed at 200,000 pounds per square inch. The temperature in the mold cavity was carefully calibrated with thermocouples to determine the equivalent length of cure of the test-specimens. Cylinders of GR-S tread stock were vulcanized for a range of cures at 1000, 20,000, 50,000, and 100,000 pounds per square inch. GR-S gum stock and Hevea gum and tread stocks were vulcanized for a range of cures at 100,000 pounds per square inch. Control specimens were cured in a regular type of mold, for which the pressure was not determined. All the volume compression during vulcanization is recovered when the pressure is released. This was determined by precise density measurements of the test-specimens. The electrical resistivity, dynamic modulus, internal friction, and resilience of the test-specimens were determined and the results are discussed.
A Method of Measuring “Heat Embrittlement” of GR-S and Hevea Rubber Compounds
Authors: Scholl Allen W. , Liska J. W. 
Published: February 2011

Abstract
This paper is a description of some studies of the phenomenon variously described in the literature as heat embrittlement, heat tenderness, heat shortening, etc. For purposes of discussion the term heat embrittlement will be employed in a general sense to denote the change in breaking elongation resulting from a change in test conditions, i.e., test temperature, cure, or aging. Inasmuch as the expression heat embrittlement is purely qualitative, no definite experimental procedure for its determination is implied, such as is implied, for instance, in the term ultimate tensile strength. Such lack of definiteness in terminology often leads to considerable confusion and the development of widely different test techniques for measuring the same phenomenon. Illustrative of the latter point are two heat embrittlement tests, one introduced by W. B. Wiegand and the other by R. B. Hobson. The first method is based on a measurement of the length of time which a stretched T-50 strip will withstand contact with an iron heated to 400° F without breaking. In the second method, samples of raw polymers are air-aged for specified periods of time, following which benzene solubilities are determined. The amount of residue remaining after extraction is employed as a measure of the heat embrittlement of the material. With the exception of Hobson's method, there appeared to be general acceptance of the idea that heat embrittlement was correlated in some manner with breaking elongation. It was accordingly decided in this study to measure breaking elongations directly, under various test conditions, and then to express the results in terms of heat embrittlement indices, each of which is defined mathematically. Although these definitions were originally derived on purely empirical bases, they appear to yield results capable of unique and useful interpretations, as will be pointed out later.
Properties of Ebonite. XXXVII. Electrical Properties of Synthetic Rubber Ebonites
Authors: Fisher D. G. , Mullins L. , Scott J. R. 
Published: February 2011

Abstract
Experiments were carried out to explore the possibility of making good electrical ebonites from various types of synthetic rubber. The ebonites produced were tested for permittivity and power factor over wide ranges of temperature and frequency. Thioplasts (Thiokols AZ and FA) apparently do not produce hard ebonitelike vulcanizates by the normal procedure. Neoprenes (GN and I) give ebonites, but with such high dielectric power loss as to be unsuitable for use as high-frequency dielectrics; moreover, if the mix contains zinc oxide, the ebonite has a very hygroscopic and therefore electrically unsatisfactory surface. Butadiene copolymers containing polar groups (butadiene-acrylonitrile types and Thiokol RD) give ebonites with high power loss, hence are not suitable for making high-grade electrical ebonites. Polybutadiene (Buna-85) and butadiene-styrene copolymers (GR-S, Hycar-EP, Buna-S) are much nearer to natural rubber as far as the radio-frequency (100 to 2,500 kc. per sec.) power loss of their ebonites is concerned. The GR-S ebonite examined was not so good as natural rubber at room temperature, but was superior above about 50° C. Buna-85 and Hycar-EP were superior to natural rubber over the whole temperature range; indeed, the high-styrene copolymers, as represented by Hycar-EP and Buna-SS, appear to be the best type of synthetic rubber for making ebonite with low power loss, especially at high frequencies and temperatures. The effects of changing temperature and frequency on permittivity and power factor are discussed. Attention is drawn to the big effect of temperature on power factor; this was less with polybutadiene and butadiene-styrene ebonites than with natural rubber ebonite, in keeping with the greater heat resistance of the former as judged by plastic yield tests. Comparison of the effects of rising temperature and decreasing frequency shows that these produce broadly similar effects on power factor, as would be expected on theoretical grounds, but that rising temperature superposes a second effect (an increase), presumably due to increased ionic conduction.
Photoelastic Applications in Rubber Technology
Authors: Hurry James A. , Chalmers Douglas 
Published: February 2011

Abstract
Photoelastic analysis has been shown to be a feasible and reliable method for anticipating design problems in rubber products. It lends itself qualitatively and quantitatively to the selection of materials, designs, and profiles for products, test-specimens, and certain processing equipment. The apparatus, method, and calculations are relatively simple and inexpensive, as our description and examples have shown. It is hoped that other rubber laboratories will explore its possibilities further. More widespread use and publications dealing with this method will, we believe, contribute to a better understanding of rubber product performance and to more effective and economical use of materials.
Determination of Tensile Strength of Natural Rubber and GR-S. Effect of Specimen Size
Authors: Higuchi Takeru , Leeper H. M. , Davis D. S. 
Published: February 2011

Abstract
Peirce's equation, which relates observed tensile strength of textile fibers with their length, was found to be applicable to rubberlike material if specimen volume is used in place of specimen length. Experiments in which the tensile strengths of GR-S and natural rubber compositions were determined for a range of specimen volumes yielded results in close accord with theory. A tenfold increase in the volume of the material resulted in a decrease of 308 and 339 and of 204 pounds per square inch in the observed tensile strength of GR-S and comparable natural rubber stocks, respectively. The numerical magnitudes of the slopes of the straight lines obtained when tensile strengths were plotted against the logarithms of the relative specimen volumes are shown to bear direct relationships to the homogeneity of the stocks under test. The use of a dumbbell sample with a constricted center should result in a relatively simple means of measuring quantitatively the degree of homogeneity of rubber compositions.
The Determination of Nitrogen in Crude Rubber
Authors: Van Der Bie G. J. 
Published: February 2011

Abstract
It was proved that various modifications of the Kjeldahl method for determining the nitrogen content of raw rubber (with phosphoric-sulfuric acid, sulfate-sulfuric acid, mercury, copper, selenium) do not yield greatly differing values. The use of selenium as catalyst is to be preferred, since the time of destruction is shortened considerably. A standard procedure was established. The hydrogenation method of Ter Meulen was applied to a sample of rubber powder (Pulvatex). Since this determination gave the same results as the various modifications of the Kjeldahl method, it is concluded that all these methods are reliable.
Rubber Metabolism in Plant Life. Development of a New Theory
Authors: Altman R. F. A. 
Published: February 2011

Abstract
Systematic analysis of the latex of Hevea brasiliensis yielded results which induced the author to study the metabolism of rubber more closely. As it was realized that the latex picture alone would not lead to sound conclusions about the formation and breakdown of rubber, analysis of the whole Hevea tree, from the highest leaflets down to the very root tips, seemed desirable. For practical reasons, however, such a profound investigation had to be reduced to the analysis of only the most important parts of the tree. The various analytical results obtained have forced the author to make a radical revision of some of the current concepts. For several reasons the synthesis of rubber probably takes place mainly in the green parts of the plant, and principally directly from carbon dioxide. The possibility of the formation of rubber from precursors (secondary formation) is still uncertain. Such formation, for example, must proceed in etiolated germinating plants. Freshly synthesized rubber is present in the plant in the liquid state. This liquid rubber is translocated through the plant in the form of a highly dispersed oil-in-water emulsion, in which the rubber droplets are surrounded by a layer of a phospholipoid complex. As an instructive illustration of this hypothesis the formation of latex is discussed. The process of polymerization results in the transformation of the liquid rubber into the solid phase'; this solid rubber is deposited everywhere in the plant. It appears most probable that, in Hevea brasiliensis, polymerization takes place mainly in the latex vessels. The breakdown of rubber, finally, is proved to be an oxidation process. For several reasons there is cause for believing that oxidation of rubber in the plant leads to the formation of those incrusting substances which are built up by C5-groups, i.e., pentosans, hemicelluloses, lignins, etc.
The Heat Sensitivity of Hevea Latex. III. The Process of Heat Sensitization of Latex Which Has Been Degraded Biochemically
Authors: Lepetit Francis 
Published: February 2011

Abstract
The present investigation shows that the heat sensitizing effect of powdered hog pancreas on degraded latex depends on a different principle from that of other methods, since it involves the mutual effect of two actions, a decrease in stability of the rubber-phase and an increase in ionic strength of the serum. For a given small increase in ionic strength, the greater the degradation of the stabilizing substances, the greater is the tendency toward coagulation. This makes it possible in practice to dispense with washing the coagulum. Since, in addition, it is possible to preserve heat sensitized mixtures for several weeks, it is obvious that this process meets most of the requirements for the manufacture of molded goods directly from latex.
Natural, Thermal, and Biochemical Degradation of Ammoniated Hevea Latex to Give Heat Sensitivity
Authors: Lepetit Francis 
Published: February 2011

Abstract
In most heat sensitizing processes ammonium salts are added to the latex, with consequent complications in manufacturing operations. A method is described which eliminates the use of ammonium salts and in which heat sensitivity of ammoniated latex in the presence of zinc oxide is obtained by natural aging, by heat treatment, or by biochemical methods. With natural aging or heat treatment, the sensitized mixture is stable at ordinary temperature provided the zinc oxide (or carbonate) is free from ionizable impurities. Biochemical degradation of the latex is readily obtained by adding trypsin. It produces sensitized mixtures which gel quickly and satisfactorily at ordinary temperature, and which are suitable for the manufacture of articles, even of great thickness in cold molds, the resulting coagulum needing no washing on removal from the mold.
Microgel, a New Macromolecule. Relation to Sol and Gel as Structural Elements of Synthetic Rubber
Authors: Baker W. O. 
Published: February 2011

Abstract
In connection with the rubber crisis of the war, useful fundamental controls and improvements of quality of synthetic rubber which would fit in with current engineering were urgently needed. Variations in the solubility of butadiene polymers and copolymers had been noted by many rubber researchers seemingly to reflect important and controllable variables in the polymerization process, such as “modification” and degree of conversion. Solubility also was thought by some workers to bear on processability. Agreement was neither definite nor general on these phenomena. Solubility behavior and gel fraction had been casually observed for thirty years in natural and synthetic rubbers studied in Europe. No record of engineering application was found. After the organization of the polymer research program in the Office of the Rubber Director, more intensive examination of the significance of sol-gel in controlling the uniformity of GR-S was begun. A proposal new to polymer technology was made, viz., that the gel fraction of synthetic rubber comprised a characteristic structure in the raw polymer which affected the physical properties and quality (as in tire performance) of the final vulcanizate.
Preparation and Properties of Rubberlike High Polymers. VI. Polymerization and Dimerization of Isoprene
Authors: Salomon G. , Boonstra B. B. S. T. , van der Meer S. , Ultée A. J. 
Published: February 2011

Abstract
The inhibitor and initiator action of thirty-three compounds on the bulk polymerization of pure isoprene has been studied. Picric acid was found to be the most powerful inhibitor at 100° C. The conclusion reached in Part I that the initiator activity of diazoaminobenzene is superior to all other compounds has been found to be valid also between 100–150° C. The heat polymerization of isoprene between 100–150° C in the presence of picric acid leads only to the formation of dimers. Three of the four possible isomers have been separated. The solid complex compound of diprene (I) with silver nitrate has been used to separate it from dipentene (II) and the hydrocarbon of Lebedev (III, IV) has been identified as a monochloride. The relative yields (I) : (II) : (III = IV) of 16:1:2 are in agreement with the relative availability and localization of π-electrons in isoprene. Observations on the properties of polyisoprene are in agreement with the more extensive work by d'Ianni. Some remarks on polymers from bulk polymerization are added. Isoprene acts as a powerful inhibitor on the polymerization of vinylidene chloride. This effect is independent of the method of polymerization.
Preparation and Vulcanization of Unsaturated Acrylic Elastomers
Authors: Mast W. C. , Fisher C. H. 
Published: February 2011

Abstract
Ethyl acrylate was copolymerized with small proportions of eleven dienes, eleven polyolefinic esters, and six polyolefinic ethers in an attempt to prepare olefin-containing acrylic elastomers that would vulcanize readily, yielding products having improved rubbery characteristics. In general, the resulting copolymers were insoluble in organic solvents, presumably because of cross-linkage. Acrylonitrile and dodecanethiol appeared beneficial in the copolymerization of ethyl acrylate with polyolefinic esters, but of questionable value in the diene polymerizations. The best vulcanizates from the standpoint of tensile strength and elongation were obtained from an ethyl acrylate-acrylonitrile-vinyl ether copolymer. Some preparations of this copolymer, however, had a tendency to pit and bubble during vulcanization. Isoprene, piperylene, and 2,3-dimethylbutadiene were more suitable for preparing vulcanizable ethyl acrylate copolymers than the other dienes studied; their vulcanizates had moderately high tensile strengths and elongations. Some of the dimethylbutadiene-ethyl acrylate copolymers were soluble. Crotyl acrylate and geranyl acrylate, when copolymerized with ethyl acrylate, yielded copolymers that gave vulcanizates having moderately high tensile strengths and elongations ranging from 300 to 400 per cent. The physical properties of the vulcanizates prepared from unsaturated acrylic copolymers were not superior to those of the chloropropyl acrylate and chloroethyl vinyl ether products described previously.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. VI. Factors Influencing Cyclic Sulfide Formation in the Reaction of Sulfur with Polyisoprenes
Authors: Bloomfield George F. 
Published: February 2011

Abstract
Cyclic sulfides are to a large extent secondary products of the reaction of primarily formed intermolecular polysulfides with polyisoprene hydrocarbon, and undue prolongation of the time of reaction of sulfur with polyisoprenes favors cyclic sulfide formation and so reduces the cross-linking efficiency of the sulfur. Various accelerating substances markedly increase the cross-linking efficiency, either by permitting shorter reaction times, or by promoting a cross-linking rather than a cyclizing reaction of the sulfur. Thiuram disulfide accelerators in the absence of sulfur bring about cross-linking, the linkages being of —C—S—C type rather than C—C.
Behavior of Different Fractions of Purified Hevea Rubber during Vulcanization
Authors: Verghese G. T. 
Published: February 2011

Abstract
Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :
Theory on the Crystallization and Melting of Unvulcanized Rubber I. Crystallization
Authors: Kikuchi Ryoichi 
Published: February 2011

Abstract
Recently Wood and Bekkedahl have reported new experimental results on the crystallization and melting of unvulcanized rubber in the unstretched state at different temperatures. Their results are summarized as follows: (1). When a specimen of vulcanized amorphous rubber is kept at a constant temperature between about +15° and −50° C, it begins to crystallize and its volume gradually decreases, as seen in Figure 1. We shall denote the ordinate, “Decrease in volume (in per cent)” of Figure 1 by w (t), which is a function of time t for a constant temperature. (2). The arrows in Figure 1 indicate the estimated values for half the total decrease of volume at each temperature. Wood and Bekkedahl considered the reciprocal of this time to be a measure of the average rate of crystallization during the first half of the volume decrease, and it is plotted against temperature in Figure 2. We should like to call this time briefly the half-time, and denote it by th. (3). As the temperature of crystallized rubber is gradually raised, its volume increases suddenly in some region of temperature, and eventually reaches the value corresponding to amorphous state as shown in Figure 3. This phenomenon seems to be the melting of the crystal, but peculiarly the location and the width of this melting-region varies according to the previous crystallization temperature. (4). The range of melting does not depend on the extent of crystallization and is definitely determined by the temperature at which crystallization occurs. Figure 4 is derived from Figure 3 and shows the relation between the melting range and the temperature of crystallization. In the present paper the author tries to explain these results theoretically and consistently, with certain reasonable assumptions.
Equivalent Effects of Time and Temperature in the Shear Creep and Recovery of Elastomers
Authors: Conant F. S. , Hall G. L. , Lyons W. James 
Published: February 2011

Abstract
An explicit relationship is set forth for the time-temperature dependence of the viscoelastic phenomena in superelastic polymers. An empirical equation that was found to represent adequately the above-mentioned relationship over the entire multiple-temperature curve is of the form: logtc=[Cα/(T−b)]+Cβ. Experimental verification is given for the equivalent influence of time and temperature on the creep and recovery of compounds based on Hevea, GR-S, Neoprene-GN, Butaprene, and Butyl rubber. A comparison of the empirical equation with that of a theoretical reaction-rate equation of Tobolsky and Eyring indicates a temperature dependence of the energy of activation.