bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aging of Elastomers. Comparison of Creep with Some Conventional Aging Methods
Authors: Throdahl M. C. 
Published: February 2011

Abstract
Subjection of elastomers to mechanical stresses results in unusually complicated behavior. Recent theoretical researches have shown that this behavior cannot be described satisfactorily by either of the classical theories of elasticity or viscosity. The general molecular theories which describe the behavior of elastomers have experimental verification manifested by three regions of temperature-stress relationship: (1) a low temperature region in which stiffening is observed, due to the stability of secondary bonds between network chains, (2) an intermediate temperature region in which the secondary bonds are so unstable that complete relaxation occurs before measurements can be obtained; the scission of primary valence bonds is occurring at such a slow rate that no measurable effects are obtained during the course of the usual laboratory experiment; and (3) a high temperature region in which the relaxation of stress with time is associated with a chemical reaction which, through breaking of primary-valence bonds in the network, severs the chains rapidly enough to be measured during the course of usual laboratory experiments. The high temperature region is that in which elastomers soften and (or) harden and finally lose their rubbery characteristics. Oxygen has been shown to be necessary for the chain-scission reaction. Several papers have described this fundamental experimental technique for the stress-relaxation and creep of different elastomers. Well known laboratory methods for artificially aging elastomers in oxygen and air bombs and in circulating air atmosphere have selected conditions somewhat arbitrarily. In exploratory searches for promising compounds to be used as antioxidants in elastomers and in the evaluation of well known antioxidants, it has often been found that the conventional methods of aging do not differentiate among several antioxidants. It is the purpose of this paper to describe an application of the previously described creep technique as a convenient and precise means of studying the relative performance of antioxidants and accelerators in Hevea and GR-S rubbers.
Chemorheology of Polysulfide Rubbers
Authors: Mochulsky Marcos , Tobolsky Arthur V. 
Published: February 2011

Abstract
Experimental results indicate that the socalled “cold flow” of polysulfide rubbers is almost certainly chemical rather than physical in nature. The term chemorheology has been adopted to describe this chemical type of plasticity. The experimental method employed in this investigation was the measurement of relaxation of stress in stretched rubber samples held at a constant elongation. The changes in relaxation rate produced by changing the molecular structure of the rubber (by cross-linking), by incorporating carbon black, by illuminating with ultraviolet light, and by treating the rubber with various chemical agents, such as sulfur, a thiol, and agents that destroy thiol groups, were studied by this method. From the results of the above experiments and from additional considerations, it is concluded that the chemical reaction responsible for cold flow is an intermolecular exchange reaction, and that this exchange reaction is probably an exchange between a terminal thiol group of one chain and a disulfide linkage of an adjacent chain.
Preparation of Highly Purified Hevea Rubber
Authors: Verghese G. T. 
Published: February 2011

Abstract
A new method is described by which rubber hydrocarbon of a high degree of purity can be obtained without resorting to any drastic chemical or mechanical treatment of the rubber. Rubber latex is treated with ammonium oleate, which displaces the proteins from the surface of the rubber particles. The displaced proteins, along with other nonrubber substances present in the serum, are removed by repeated creaming of the latex. Finally, the creamed latex is “solubilized” in n-hexane, and the rubber precipitated by adding acetone.
Elastomer-Resin Blends. Acrylonitrile Type Synthetic Rubber and Polyvinyl Chloride Resins
Authors: Young D. W. , Buckley D. J. , Newberg R. G. , Turner L. B. 
Published: February 2011

Abstract
1. 1,3-Butadiene-acrylonitrile copolymers were mill-mixed with benzothiazoyl disulfide, sulfur, litharge, and vinyl resins, such as Vinylite (VYNW), and Saran and cured to compounds with good tensile strength, modulus, hardness, solvent resistance, and blocking temperature. 2. Results show that higher acrylonitrile type of copolymers give cured Vinylite-rubber blends with higher tensile strength, higher 100 per cent modulus, and greater ultimate elongation to break than low acrylonitrile copolymers. 3. The low temperature properties of the cured blends improve as the acrylonitrile content of the synthetic rubber is reduced. 4. An effective cure at 287° F is obtained in 15 to 30 minutes by using 2 parts of accelerator and 2 parts of sulfur per hundred parts of 1,3-butadieneacrylonitrile type copolymer-Vinylite blends. Added amounts of sulfur, and accelerator did not improve the properties or decrease the cure time at 287° F. 5. Some of the cured blends studied are free of tackiness at temperatures as high as 230° F. 6. Some stabilizers for vinyls tested as well as sodium acetate can be used to activate sulfur cures in 1,3-butadiene-acrylonitrile copolymer-Vinylite blends to formulate light-colored transparent products.
Action of Organic Accelerators in Vulcanization of Rubber. Effect of Basicity
Authors: Kratz G. D. , Young H. H. , Katz Isadore 
Published: February 2011

Abstract
When organic compounds were first found to function as accelerators for the vulcanization of rubber, Peachey and others attributed their activity, at least in part, to the basicity of the substances employed. Patents, to mention but one, were issued stating that there was a specific order of basic strength beneath which accelerating activity would not occur. We have already shown that this is not necessarily true, since acceleration was observed with a weaker base than the patent would have permitted. However, the whole subject has been dormant for many years. The results reported here indicate that there is a real correlation between accelerating power and basic strength: In a closely related series of compounds e.g., aniline, methylaniline, dimethylaniline, the accelerating power, as measured by combined sulfur, is a linear function of the logarithm of the basic dissociation constant, Kb. This relationship has been observed most strikingly with o-, m-, and p-phenylenediamines, and with o-, m-, and p-toluidines. It has been observed also with aniline, diphenylamine, and triphenylamine, and with mono-, di-, and triphenylguanidines. Guanidine itself does not fall into line, but exhibits a behavior comparable with that of sodium hydroxide, which it approaches in basicity (approximately 103 to 104 times the phenyl-substituted compounds).
Effect of Moisture Variations on Curing Rate of GR-S
Authors: Rush Ian C. , Kilbank S. C. 
Published: February 2011

Abstract
Variations which are beyond experimental error have occurred in the rate of curing of GR-S control and production lot samples tested in this laboratory. It is believed that other laboratories in the synthetic rubber industry have encountered similar variations. Changes in the moisture content of the compounded stock at the time of curing have been suspected of causing the fluctuations in the rate of curing. Several papers on the effect of moisture on the rate of curing of GR-S have dealt largely with relatively high moisture contents. However, this investigation was undertaken to correlate the 300 per cent modulus with the moisture contained in the stock at the time of cure. Rupert and Gage observed that, in testing a large master batch of GR-S at intervals, variations in the rate of curing and modulus values beyond experimental error occurred without any apparent relation to time of standing. The same authors have shown that both GR-S raw polymer and compounded stock absorbs or adsorbs moisture from the air, the amount depending on the humidity of the air. Braendle and Wiegand have shown that the moisture content of rubber-grade carbon black during storage can vary from 0 to 4 per cent. Samples of black taken in this laboratory between December 1946 and March 1947 varied from 0.2 to 2.5 per cent moisture. Under the same conditions at which the black contained 1.0 per cent moisture, the other pigments (sulfur, zinc oxide and mercaptobenzothiazole) each contained roughly 0.7 per cent moisture. Two previous papers have shown that the moisture retained in a mixed batch varies in proportion to, but is less than, the moisture added to dry pigments. Both authors, however, used relatively inaccurate means to determine the water retained, and were interested in higher moisture contents than mixed batches would normally contain.
Carbon Black Dispersion in Rubber. Effect of Fat Acids
Authors: Morris Ross E. , Hollister Joseph W. 
Published: February 2011

Abstract
Whether or not stearic acid assists in dispersing carbon black in rubber has not been settled. Blake was the first to claim that fat acids are dispersing agents for carbon black. He postulated a mechanism, based on Langmuir's work, with monomolecular films of fat acids on water and calculated that the fat acids naturally present in Hevea rubber, which he stated to be present to the extent of 2 per cent, are just sufficient to form a monomolecular film on each particle of 30 volumes of channel black in 100 volumes of rubber. He assumed that this monomolecular film serves to facilitate wetting the individual particles with rubber and prevents agglomeration or flocculation of the particles. Later developments, however, have invalidated Blake's calculations. Blake assumed that the diameter of the average channel-black particle is 200µ, whereas electron photomicrographs have shown that the actual average particle diameter is 28µ. Therefore, 30 volumes of channel black have about seven times the surface area calculated by Blake. The fat acids in Hevea rubber, even if present to the extent of 2 per cent and entirely concentrated on the surface of the particles, are insufficient to cover completely the surface of this quantity of channel black.
Carbon Black-Loaded GR-S Stocks. Relationship between Reinforcement and Swelling Properties
Authors: Dannenberg E. M. 
Published: February 2011

Abstract
The fact that equilibrium swelling measurements do not show any strong interaction of a primary-valence type between filler and rubber does not exclude the possibility of weaker attractive forces, or such low concentrations of primary valence cross-linkages that they cannot be detected by the methods used. The results of this work indicate that carbon black—rubber systems should be considered as simple physical mixtures. It is hoped that this concept will clarify some of the confusion regarding the reinforcing effect of finely divided powders.
Effect of Carbon Blacks on Swelling of Neoprene GRM-10 Vulcanizates
Authors: Catton N. L. , Thompson D. C. 
Published: February 2011

Abstract
Reinforcement of elastomers with fillers has generally been measured by physical properties, such as tension stress-strain, tear resistance, hardness, and compression modulus. To a more limited extent, swelling in solvents has been recognized as associated with reinforcement. In natural-rubber vulcanizates it has been demonstrated that reinforcing fillers impart greater resistance to solvents and oils than do nonreinforcing types. Addition of the latter gives only the reduction in swelling attributable to elastomer dilution. In the case of Neoprene vulcanizates, Catton and Fraser reported that fillers function only as elastomer diluents and that those fillers commonly considered as of the reinforcing type impart no greater resistance to solvents than the nonreinforcing type. More recently, however, Buist and Mottram, in describing the effects of carbon blacks on the physical properties of natural rubber and Neoprene, reported that with both of these elastomers compounds containing thermal type carbon black gave slightly greater swelling in benzene than compounds containing equal loadings of other types of carbon black. With Neoprene, they reported good correlation between moduli and swelling characteristics.
An Improved Low-Temperature Brittleness Test
Authors: Smith E. F. , Dienes G. J. 
Published: February 2011

Abstract
An improved low-temperature brittleness tester, capable of testing five specimens simultaneously, is described. All machine specifications conform to A.S.T.M. Method D 746-44T. Data are presented which show that many elastomers do not possess a sharp brittle point but are characterized by a distribution of failures over a temperature interval. The improved brittleness tester makes it possible to carry out the necessary statistical study of the distribution of per cent failures versus temperature with a reasonable amount of work. A simple analysis of the resulting distribution curve is presented.
Relationship between Laboratory Abrasion Tests and Service Performance
Authors: Griffith T. R. , Storey E. B. , Barkley J. W. D. , McGilvray F. M. 
Published: February 2011

Abstract
In development work on GR-S commercial recapping compounds originated in 1943 by the Directorate of Mechanical Engineering, Department of National Defence, Ottawa, Canada, in which an attempt was made to correlate road performance with physical properties as determined in the laboratory, it was found that no relationship whatever existed between the results of road tests carried out under the supervision of that directorate and standard laboratory abrasion resistance tests carried out in the Canadian National Research Council Rubber Laboratory at Ottawa. In the laboratory test the sandpaper in the abrasion machine became coated with a smear of tacky viscous material which the air jet was unable to remove. Under these conditions the rubber tends to slide over the sandpaper surface, with relatively little actual abrasion of the rubber. The effect remains even after a considerable overcure of the sample. It was felt that the removal of the tacky viscous material from vulcanized GR-S by extraction might give more reliable abrasion resistance results, inasmuch as, on the road, rubber is constantly coming in contact with a new surface and such viscous material is thus being continually removed as it migrates to the surface of the rubber. From this point of view, then, the tread surface while being abraded on the road may be looked upon as extracted rubber and may be considered as conforming closely to the extracted laboratory specimen.
Flex Life of Passenger Tires. Relationship of Rayon Tire Cord Dip Pickup and Cord Adhesion
Authors: Murphy R. T. , Baker L. M. , Reinhardt R. 
Published: February 2011

Abstract
The tests described herein show that in woven rayon passenger tires, tire performance is improved when the quantity of dip pickup is reduced, even though there is a sacrifice in adhesion values.
Drying of Latex Rubber Deposits
Authors: Partridge E. G. , Hansen M. E. 
Published: February 2011

Abstract
In conclusion, it may be stated that the general principles of drying latex rubber deposits are much the same as for drying any other article, but there are conditions present that make drying more difficult. The porosity of the deposits decreases as drying proceeds; consequently the diffusion of the water through the deposits is progressively slower. Blisters can be formed between the deposits and the forms, but the formation of blisters can be controlled. During drying, flowable films such as those created by straight dipping can become wetter after being put into a drying oven. All these difficulties can be overcome by the proper design of ovens and the proper applications of fundamental drying principles.
The Hysteresis of Vulcanized Rubber
Authors: Clouaire Jacques 
Published: February 2011

Abstract
The present paper is based on an extensive investigation of the tensile properties of vulcanized natural rubber, carried out at the French Rubber Institute from April 1944 to December 1946. The purpose of this paper is to show how, in problems such as hysteresis, the correlation of certain experimental facts which apparently bear no relation to one another may lead to an explanation of the phenomenon involved. The hysteresis effect shown by both natural rubber and synthetic rubbers after stretching has been recognized for a long time, and it can be defined as the nonsuperposition of the strain and recovery curves of one complete cycle of deformation. It should be noted that this definition makes no reference to the causes of the phenomenon nor to the idea of loss of energy, which is not so clearly defined as generally believed. As a matter of fact, although the literature on the elasticity of rubber is remarkably extensive, little information is to be found on the underlying causes of hysteresis. The only real experimental work on the subject was carried out by Bouasse, who succeeded in throwing light on some of the complexities of the phenomenon. However, it appears that since that time little attention has been paid to his work. This may account for the fact that the idea of hysteresis being due solely to internal friction is still so widely accepted, although actually so completely incorrect.
Hysteresis and Heating in Vulcanized Rubber
Authors: Oberto S. , Palandri G. 
Published: February 2011

Abstract
Laboratory tests for evaluating energy losses due to hysteresis are analyzed. The importance of taking into consideration the thermal conductivity and cooling conditions of the rubber sample for the evaluation of heating due to hysteresis losses at temperature equilibrium is discussed. Two new test methods, based on forced resonance oscillations, are described, in which the rubber samples are deformed respectively in shear and in tension at frequencies of 20 to 200 cycles per second, with dynamic shear strain of 0.02 to 0.4 and dynamic tension strain of 1 to 5 per cent, and at a temperature of 20 to 110° C. Experimental results obtained with natural rubber and GR-S gum and tread stocks are presented. The hysteresis losses in gum stocks are found to follow the quadratic law versus dynamic shear strain, and the dynamic modulus G is found to be independent of shear strain. With tread stock the hysteresis losses are lower than would be the case with the quadratic law versus dynamic shear deformation, and the dynamic modulus G decreases with increasing dynamic shear strain. Neither the hysteresis losses nor the modulus depend on the shape or size of the specimen. The modulus is found to be independent of frequency, while the hysteresis losses are found to increase proportionally with frequency. As an application of the test method, results are presented of the effect of the quality and quantity of various types of carbon black on hysteresis heating of GR-S stocks.
A Study of the Increase in Tensile Strength of Vulcanized Rubber when it Begins to Age
Authors: Judeinstein Robert 
Published: February 2011

Abstract
In conclusion, the present study confirms the phenomenon of an increase in tensile strength at the beginning of aging. The magnitude of this increase depends on the nature of the acceleration and the state of cure; the tensile strength of an undercured sample increases much more than that of a sample vulcanized to its optimum state of cure, and the maximum tensile strength reached by the former is definitely higher than the maximum tensile strength reached by the latter. The phenomenon is therefore not simply postvulcanization. This increase in tensile strength takes place in the presence of oxygen and also in a vacuum as high as 10−3 mm. In the latter case, measurements of the T-50 value and combined sulfur give indications of an increase in network structure for a given percentage of combined sulfur. Oxygen is a contributing factor in increasing the network structure, but, in its presence, combination of sulfur is not so great and the maximum tensile strength attained is lower.
Permanent Set in Vulcanized Rubber
Authors: Mullins L. 
Published: February 2011

Abstract
The residual extension which remains after a sample of rubber has been stretched for some period, then released and allowed to recover, is popularly called permanent set. This set, however, is far from being permanent since it continuously decreases with the period of recovery; furthermore, after the rate of recovery has become exceedingly slow and is no longer readily observable, an increase in temperature will usually result in a sharp increase in the rate of recovery. It has been usual to identify this set with irreversible plastic flow, but it will be immediately evident that this can rarely be justified for, owing to incomplete high-elastic recovery, the measured value of set is a combination of both plastic flow and high-elastic deformation which has not completely recovered. Thus before any attempt is made to discuss the interpretation of the results of set tests, a study must be made of the significance of set. Treloar has investigated this phenomenon in raw natural rubber and has shown that entanglements or cohesional linkages may form while the rubber is stretched, and these oppose recovery; further, although van der Waals forces between the long-chain molecules largely control the rate and the amount of recovery, the crystallization of rubber produced by stretching may profoundly influence the set. On the other hand Tobolsky has studied the set which results from stretching rubber vulcanizates at high temperatures ; in such cases the amount of set is controlled by two processes which take place while the rubber is stretched; one of these involves the oxidative breaking of network chains, the other the oxidative cross-linking of network chains. Although these ideas are well founded, they do not provide a completely satisfactory basis for the understanding of set, and the purpose of this work is to extend these ideas and to explain the significance of the results of normal set tests ; in these tests rubber samples were extended at room temperatures to moderate elongations for relatively short periods of time. Most of the tests performed in this investigation were made on dumbbell shaped samples, which were extended by 200 per cent of their initial length for fifteen minutes at room temperature and then allowed to recover for one hour at room temperature; the residual extension was then noted and expressed as a percentage of the initial length. These tests will be referred to as normal set tests. In some tests various periods and temperatures of extension and recovery were used.