bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact Resilience in Testing Channel Black
Authors: Fielding J. H.
Published: February 2011

THE precise grading of carbon black has been a problem to rubber manufacturers for years. Empirical specification tests inherited from the paint and ink industries have been used extensively; although they may have great merit in predicting the behavior of a black in paint or ink, they generally tell very little of its value in rubber. Since neither these tests nor the usual stress-strain data showed any great differences that could be associated with type of carbon black, chemists have been inclined to believe in the past that the rubber grade of channel black was quite a uniform material, at least when used in mercaptobenzothiazole stocks. Among the tests which have been used recently in the grading of black is resilience of the cured stock as determined by an impact pendulum. Although superficially it seems to measure no fundamental property of the black, it is a very practical test from a laboratory standpoint and appears to be capable of at least rough correlation with more fundamental properties. It is not a new property; the fact that it is influenced by carbon black is not new; but its application to the separation of blacks within the range of rubber channel black is new, and this phase will be discussed here.
The Evaluation of Rubber and Rubberlike Compositions as Vibration Absorbers. Apparatus for Automatic Recording
Authors: Yerzley Felix L.
Published: February 2011

The equipment is simple and foolproof. It provides an autographic record in a few seconds, from which can be evaluated dynamic hardness, dynamic modulus, internal friction, static hardness, and drift. It can be used to test rubber and rubberlike compositions over a very wide range of temperatures—for example, from −40° to 150° C. —for testing compositions which have been exposed to solvents or gases, and in conjunction with a fatigue machine for evaluation at various stages in a life flexing test.
Scorch Retarders and Scorch-Retarding Materials
Authors: Thies H. R.
Published: February 2011

Softeners, such as pine tar, rosin oil, and mineral oil, are useful when scorching trouble is encountered, owing to their scorch-retarding properties as well as to the fact that they soften the rubber batch. Stearic acid functions as a scorch-retarding material as well as an activating material when used with mercaptobenzothiazole. A decided gain in scorching time is demonstrated by use of scorch-retarding material without alteration to a great extent of the physical properties of the compound used. There is a definite change in the temperature coefficient of scorching encountered between 82° and 130° C., this coefficient being greater when rated per 10° C. for the temperature change between 82° and 99.5° C. than it is either between 99.5° and 113.5° C., or between 113.5° and 130° C. There is a tendency on the part of the stocks containing some retarders to give a greater percentage decrease in temperature coefficient of scorching over the range studied than does the control stock. With other retarding materials this does not hold. A scorch-retarding material is best measured by its effect upon index numbers of a control stock rather than by its effect upon the temperature coefficient of scorching.
Behavior of Rubber under Repeated Stresses
Authors: Holt W. L.
Published: February 2011

The stress-strain relations of a sample of rubber are very markedly affected by the previous strain history. Rubber will recover to some extent from the effects of a strain, but not completely. In a rubber compound, such as tread stock, a series of increasing strains has a pronounced progressive action, each increase in strain producing added effects. The conventional stress-strain curve does not represent the permanent characteristics of a rubber compound.
Acetylene Polymers and Their Derivatives. II. A New Synthetic Rubber: Chloroprene and Its Polymers
Authors: Carothers Wallace H. , Williams Ira , Collins Arnold M. , Kirby James E.
Published: February 2011

Chloro-2-butadiene-1,3 (chloroprene) is described and its structure established through reactions leading to its conversion into butane-α, β,γ,δ-tetracarboxylic acid, and into β-chloroanthraquinone. Within ten days under ordinary conditions in a closed vessel containing a little air, chloroprene spontaneously changes into a transparent, resilient, strong, non-plastic, elastic mass resembling vulcanized rubber. This product is called μ-polychloroprene. By interrupting the polymerization before it has proceeded to completion one obtains a soft, plastic product (α-polymer) that resembles unvulcanized rubber. Under the action of heat the α-polymer rapidly changes to the μ-polymer. Other polymers of chloroprene described are volatile (β-) polymer, granular (ω-) polymer, and balata-like polymer. The structures of the polymers are discussed as well as the effect of conditions on the formation of each type. Unlike any previously described synthetic rubbers, μ-polychloroprene resembles natural rubber in the fact that when it is stretched its x-ray diffraction pattern shows a point diagram. The transformation of chloroprene into μ-polychloroprene occurs very rapidly in aqueous emulsion. The resulting product constitutes a synthetic (vulcanized) latex. It has a much smaller particle size than natural latex and it penetrates porous materials more readily. Chloroprene can also be polymerized in the pores of porous or bibulous materials. The materials thus become intimately impregnated with synthetic rubber. Compared with natural rubber the new synthetic rubber is more dense, more resistant to absorption or penetration by water, less strongly swelled by petroleum hydrocarbons and less permeable to many gases. It is much more resistant to attack by oxygen, ozone, hydrogen chloride, hydrogen fluoride and many other chemicals.
Some Factors Affecting the Resistance to Flexing
Authors: Neal Arthur M. , Northam Alfred J.
Published: February 2011

Failure on flexing has been shown to be due to oxidation rather than mechanical fatigue or the action of ozone. The action of secondary aromatic amines of the type of phenyl-β-naphthylamine in retarding the failure of rubber on flexing lies in their antioxidant properties. WITHIN the last few years the deterioration of vulcanized rubber under dynamic strain has received considerable attention from the rubber industry. The cracking of tire treads, carcass, and belting separation, the cracking of boot uppers and shoe soles are types of failure which come in this class. In order to study this type of deterioration it is necessary to have a quick method of laboratory evaluation. To meet this need, a large number of the rubber manufacturers have developed flexing machines, many of which are designed to make only specific tests. In addition, there are several general-duty flexing machines, for example, the De Mattia, the Torrence-Peterson, the du Pont, and the United States Rubber Company machines. All of these are designed to duplicate in the laboratory in a short period of time the same conditions which the article must withstand in service.
The Degradation of Rubber Solutions of Different Concentrations
Authors: Bary P. , Fleurent E.
Published: February 2011

Xylene solutions of rubber of the smoked plantation crepe type were placed in an atmosphere of nitrogen and maintained at a nearly constant temperature of 95° C. Solutions of five different concentrations were employed, namely, 5.12, 3.94, 2.88, 1.98, and 0.99 per cent, and measurements of the viscosity were made as before by the flow through a tube with an inside diameter of about 1 mm. In curves of the relative viscosity as a function of the time, the hyperbolic law already described (Comptes rendus 192, 946 (1931); Rubber Chemistry & Technology, 4, 505 (1931)) was again found to be true, but only for concentrations of 1.98 and 0.99%. With more concentrated solutions the curve presents a characteristic point, and can be separated into two distinct periods: (a) A period of disaggregation of the rubber swollen to the state of jelly in suspension in the xylene. The greater the concentration the more prolonged is this period (e. g., 320 hours for the 5.12 per cent solution and 110 hours for the 2.88 per cent solution). (b) A period of molecular degradation following that just described, during which the viscosity approaches more and more that of the solvent, while following the hyperbolic law observed previously.
The Plastic State
Authors: Antonoff G.
Published: February 2011

In the preceding article, Bary has shown a curve of the changes with time in rubber solutions of various concentrations, the interesting feature of which is the angular break which separates the curve into two sections. In a discussion of this paper, attention was called by de Meeus to the fact that it would be interesting to study the physical properties of rubber solutions as a function of the concentration without the complicating effect of aging. This brings up the question whether this curve would also have a similar break. Though data are not available on rubber solutions, it is considered that this is rendered probable by the following facts. Rubber solutions are true solutions or pseudo-solutions at great dilutions, while they become plastic at high concentrations. Experiments with certain plastic systems have shown a phenomenon which is characterized by the accompanying curve. A study of the physical properties of systems formed of various pigmente in suspension in unoxidizable oils, as a function of the concentration, showed that, in general, the properties change uniformly and continuously with increase in concentration of the pigment until a point is suddenly reached where a very pronounced break in the curve occurs.
Isoprene and Rubber. Part 28. The Fractionation and Cracking of Hydrorubber
Authors: Staudinger H. , Schaal W.
Published: February 2011

The Fractionation of Hydrorubber According to the investigations of Geiger, treatment of rubber with hydrogen in the presence of nickel at 270° brings about a reduction with simultaneous cracking of the macromolecules of the rubber. The hemi-colloidal hydrorubber thus formed ought not to consist of uniform long molecules, but of a mixture of homologous polymers; because in other similar cases mixtures of homologous polymers were obtained when macromolecular substances are decomposed, e. g., in the acetolytic decomposition of polyoxymethylenes and of cellulose. According to the views of Pummerer, on the other hand, if rubber consists of relatively small molecules, there would be no decomposition by cracking during its reduction, but only a saturation of individual primary valence chains with breaking up of the micellar structure, with formation of a hydrorubber whose molecules are uniformly long. Pummerer and Koch believed that they had obtained such a substance. To prove whether hydrorubber consists of a mixture of homologous polymers, it was split up into five fractions by fractional precipitation with alcohol from its ethereal solution, and the viscosities of the individual fractions were determined in 0.5 molar carbon tetrachloride solution (Table I).
An Investigation of the Effect of Gas Black on Rubber
Authors: Stamberger P.
Published: February 2011

1. It is shown that changes in the solubility of mixtures of rubber and gas black do not parallel changes in plasticity. 2. Rubber-gas black mixtures become insoluble only upon standing after milling, which makes it improbable that the insolubility of these mixtures depends upon a flocculation of the gas black in the mixture. 3. An adsorption of rubber from its solutions by gas black could not be established. 4. The heat of wetting of gas black with toluene and of a five per cent rubber solution in toluene were the same, as was the quantity of gas set free by the wetting. The dispersing action of rubber solutions does not depend upon a better wetting.
Mastication of Rubber. An Oxidation Process
Authors: Busse W. F.
Published: February 2011

The effects of milling and of exposure to light are similar in altering smoked sheet, pale crepe, and balata so that they affect a photographic plate in the dark. This effect is due to the formation of a volatile peroxide, probably hydrogen peroxide. No image is formed by sprayed latex, fine Para, anode rubber, or guayule after being milled or exposed to the light. The order of the intensity of the images formed by smoked sheets, pale crepe, and sprayed latex is the same as the order of their rate of change of plasticity on milling. Cold-milling is more effective than hot-milling, both in the formation of the peroxide and the breakdown of the rubber. Milling on a cold mill produces a luminous discharge from the blanket to the bank, but this disappears when the rolls are heated. Sprayed latex and fine Para contain some material which decomposes hydrogen peroxide. This accounts for the fact that peroxides could not be detected in these rubbers, either after exposure to light or after milling, even with the addition of hydrogen peroxide. Both copper and cobalt soaps decompose the peroxide in some instances, though under other conditions the cobalt soaps greatly increase the amount of peroxide in the rubber.
Crystallized Rubber
Authors: Pummerer R. , von Susich G.
Published: February 2011

In recent years various attempts have been made to crystallize natural rubber by some means other than by stretching. In the present paper the results of these experiments are described, together with some new observations, in order to settle the present status of the problem. The processes of crystallization are divided into three groups and discussed individually. 1. Spontaneous crystallization under conditions which vary but little from the normal conditions. 2. Crystallization from solution after purification. 3. Crystallization of a solution of purified rubber by cooling to a low temperature. It is a generally known fact that after storage for a year, plantation rubber becomes stiff, inelastic, and opaque. A rubber altered in this way is known as “frozen” rubber, because this change has been observed most frequently after storage in a cold place. The x-ray investigations of Katz and Bing have rendered it certain that during “freezing” there is crystallization of the rubber, because when subjected to x-rays frozen rubber shows crystalline interferences from which the same crystal lattice is calculated as that which is formed on stretching, except that the degree of orientation in frozen rubber differs from that of stretched rubber. This is seen in x-ray diagrams, where the nearly point interferences of the stretched samples lie on the same Debye-Scherrer circles as those of frozen rubber. There have been rather exhaustive investigations on those changes in frozen rubber which appear on warming, viz., during transformation of the crystalline to the amorphous state (the “fusion process”), and which are characterized by disappearance of the crystal interferences and by a discontinuous change in the heat content, specific gravity, hardness, and light absorption.
Isoprene and Rubber. Part 35. Soluble and Insoluble Rubber and the Fractionation of Rubber
Authors: Staudinger H. , Bondy H. F.
Published: February 2011

According to the views of earlier authors, the transformation of insoluble rubber to soluble rubber is reversible. Bary and Hauser speak of an equilibrium between the α and β forms which takes place rapidly. The reversion of insoluble rubber to soluble rubber is brought about by mastication, by chloroacetic acid and other acids, and finally also by standing in air. The fact was completely overlooked that the soluble rubber thus obtained has quite different properties from the original rubber. Its solutions have a low viscosity. Accordingly it is not a question of a reversion from insoluble to soluble rubber, but of a degradation. The conversion of insoluble to soluble rubber is a result of a cleavage of the molecules of insoluble rubber by reagents such as chloroacetic acid and oxygen, and finally during mastication. The 3-dimensional molecules of the insoluble rubber, which are composed of long fiber molecules of soluble rubber, are broken up in this degradation into short fragments which are also fiber molecules and therefore dissolve. The soluble rubber obtained by decomposition is of a hemi-colloidal character, and is not the original high molecular soluble rubber. A similar decomposition also takes place with further autoöxidation; the insoluble rubber passes rather quickly to degraded soluble rubber when it is heated in the strongly swollen state at 60° in the presence of air. Insoluble rubber is also rendered soluble by strong mastication. Here, too, there is a degradation by oxidation. Naturally it is also possible that a direct mechanical rupture of the chains takes place. A deeper insight into the process of mastication will be had only if rubber is masticated with the most careful exclusion of air.
Modifications of the Gutta-Percha Hydrocarbon
Authors: de Jong A. W. K. , Katz J. R.
Published: February 2011

The spongy product from gutta-percha hydrocarbon, which is obtained from a concentrated petroleum ether solution, consists of microcrystals of the α-modification. The difference in its solubility and that of the compressed product prepared from the spongy product is perhaps attributable to the presence of an impurity. By treatment of the fused hydrocarbon with benzene below 19° C. both the β-form and the amorphous form dissolve, and one of these forms is converted, or perhaps both of the forms are converted, into the α-form. It is possible that petroleum ether dissolves not only the amorphous form but also a part of the β-form. It does not, however, transform the β-form into the α-form. Compression in the cold of previously fused strips, as well as of strips elongated while cold, decreases the solubility of these strips in benzene below 19° C. Cold-drawing of threads, which have been prepared from fused products, has only a slight influence on the stability of the threads in benzene below 19° C.
Remarks on the Formation of Jellies in Rubber Solutions Containing Ultra-accelerators. Influence of the Solvent
Authors: Thiollet R.
Published: February 2011

Rubber solutions are used for coating fabrics, for cementing pieces of rubber, and for manufacturing certain objects like nipples. These various articles can be vulcanized in the cold with sulfur chloride, but it is becoming more and more popular to vulcanize them by the hot method, which necessitates the use of ultra-accelerators. Rubber solutions containing ultra-accelerators are often transformed, in some cases rapidly, into jellies which are absolutely useless. In connection with the formation of these jellies, we have made certain observations, which it is believed will be useful in the preparation of solutions containing these rapid accelerators. These observations deal with: (1) the influence of the accelerator, and (2) the influence of the solvent, on the rapidity of the formation of jellies. We studied first of all tetramethylthiouram mono- and disulfide, which are the accelerators most often used for vulcanizing in hot air. We have studied them alone and in combination with other accelerators, such as mercaptobenzothiazole, ethylidene-aniline, and anhydroformaldehyde-aniline. The solutions were made under the following conditions. A series of mixtures containing different accelerators was prepared from the same base mix by mixing on a roll mill. These mixtures were prepared with a constant distance between the rolls, and by passing the mixtures through the same number of times.
The Influence of Certain Accelerators on the Aging of Rubber
Authors: Martin G. , Thiollet R.
Published: February 2011

Among the accelerators which are at present on the market two are very much used, viz., diphenylguanidine as an accelerator of medium activity, and tetramethylthiouram disulfide as a rapid accelerator. Diphenylguanidine is used most of the time in proportions between 0.5 to 1 per cent, based on the rubber, and with about 3 per cent of sulfur. Tetramethylthiouram disulfide is used in proportions of between 0.2 and 0.5 per cent, based on the rubber, with about 1.8 per cent of sulfur. In this way “nervy” mixtures are obtained which have excellent physical properties; but it must be recognized that these two accelerators are, each in its class, the ones which impart to mixtures the poorest aging qualities. For example, the mixture: Pale crepe 100 Zinc oxide 5 Sulfur 3 Palm oil 1 Stearic acid 0.5 Diphenylguanidine 0.7 vulcanized 1 hour at 3 kilograms pressure, i. e., under conditions which lead to the best physical properties for the proportions used, was investigated.
The Effect of Pigments in Rubber
Authors: Boiry F.
Published: February 2011

1. Gas black, light calcined magnesia, litharge, hydrated lime, and, to a lesser degree, lamp black give mixtures which do not disintegrate in benzene hydrocarbons. These mixtures disaggregate only after prolonged immersion in an excess of solvent, and the less pigment they contain and the less disaggregated the rubber, as a result of the mechanical working, the longer is this time. The other pigments with rubber form mixtures which disaggregate very rapidly, and from which the rubber dissolves very rapidly. 2. This effect of pigments of the first group is a result of adsorption of the rubber by the pigment particles. 3. In the case of gas black and lamp black, this adsorption phenomenon depends chiefly upon the very great specific surface of these pigments. With magnesia and magnesium carbonate, with hydrated lime, and with litharge it depends chiefly upon a difference in electric potential between the particles of pigment and the rubber. 4. There is a relation between the influence of the pigments on the solubility of raw rubber and their reënforcing effect on rubber after vulcanization. Gas black, magnesium carbonate, and calcined magnesium are the most active in both these respects. The relation is clearly defined in the case of lamp black, less so with litharge, and much less so with zinc oxide and with hydrated lime. The differences in the behavior of these last pigments are apparently due to chemical reactions which take place during vulcanization. 5. Tests carried out to modify the properties of these pigments have not up to the present time given definite results.
Hysteresis and Reinforcement
Authors: Barron H. , Cotton F. H.
Published: February 2011

1. The relationships between work of extension, work of retraction, and hysteresis loss in vulcanized rubbers loaded with fillers have been examined. 2. The hysteresis loss in vulcanized rubber during a cycle of extension and retraction increases with amplitude to an extent comparable with the increase in work of extension. 3. If the work required to extend a vulcanized rubber to a given elongation be increased by compounding with fillers, the energy lost through hysteresis on slow retraction increases to a comparable extent. Hence reinforcement does not appreciably increase the ability of rubber to store energy. 4. With any rubber vulcanized to optimum tensile properties, hysteresis loss and work of retraction from any elongation are proportional to the work required to extend to that elongation. Therefore if the hysteresis loss during a given cycle be known, the work of retraction from the breaking point can be calculated. 5. The work of retraction from the ultimate breaking point of a vulcanized rubber increases slightly with reinforcement, and becomes greatest when reinforcement is at a maximum. This is thought to be a function of the rubber-filler interface. 6. No filler was found to lessen the work of retraction from the breaking point until the rubber was highly compounded. 7. It is suggested that the increased work required to rupture rubber that has been reinforced with fillers is mainly dissipated in overcoming consequent increased internal friction; a small quantity being converted to potential energy through strain of the filler-rubber interface.
A Short Note on the Tensile Testing of Rubber
Authors: Jones M.
Published: February 2011

The evaluation of rubber has centered largely around stress-strain phenomena, and the property of tensile strength is probably the one which has the most general application throughout the industry. Rubber exhibits stress-strain properties quite different from the majority of substances, and peculiar difficulties are introduced during the determination of tensile strength. Although tentative standards have recently been issued by the American Chemical Society, there is no evidence that these are being strictly adhered to, and there is still need for a more rigid standardization of tensile-testing methods. There are essentially two methods of tensile-testing: (1) Using dumb-bell test-pieces with a Bureau of Standards machine, or a Scott type of machine; and (2) Using ring test-pieces with a Schopper type of machine. It is generally supposed that higher tensile results are obtained by the former method. Recently, occasion has occurred to make a comparison between both types and to study the effect of certain factors upon each method.
An Investigation of the Causes of Spots Which Appeared Spontaneously on Rubberized Fabrics
Authors: Martin G. , Sisley J.
Published: February 2011

The opportunity was offered to examine a white rubberized fabric on which rosecolored spots had developed spontaneously. This fabric was to be used in the manufacture of white footwear, and was constructed of two plies of fabric, a white cloth and an unbleached cretonne cemented together by a rubber solution. On certain pieces of the plied fabric and on certain lots of the finished footwear, there gradually appeared patches of a rose color, which were especially prevalent on the unbleached fabric and on the white edge of the footwear. Since both unblemished cloth and cloth in various stages of spotting were available for examination, an investigation was made of the differences between the good and the bad fabrics, and of the causes of the rose-colored spots. An unbleached sample of cloth on which the rose-colored blemishes were intense was first examined. In this case extraction with boiling water gave a liquid with a slight acid reaction. Another portion of the same cloth, treated with 20 per cent acetic acid, yielded a dye, the reactions of which indicated that it belonged to the triphenylmethane group of dyes, since it resembled fuchsin and rosaniline. The presence of an aromatic amine in the aqueous extract could not be established.
Studies in the Vulcanization of Rubber. V. Dielectric Constant and Power Factor of Vulcanized Rubber
Authors: Kitchin Donald W.
Published: February 2011

1. Power factor and dielectric constant data have been given for vulcanized rubber samples tested over a wide range of composition, temperature, and frequency. 2. The real identity of the agents responsible for the peculiar dielectric behavior is not known. It seems probable that these agents are the rubber-sulfur molecules themselves. because the effects increase, under proper conditions, directly with per cent combined sulfur. 3. The effect of increasing sulfur content on the dielectric behavior is complex; it modifies not only these supposed agents themselves, but also the stiffness of their environment. Moreover, at a given sulfur content the agents are not identical but differ widely in relaxation time, and therefore in ability to respond; and with progressive addition of sulfur, the rubber does not increase continuously in stiffness, but, at a composition which depends on the temperature, passes rather abruptly from a soft to a hard state. 4. The temperature at which the transition from one state to the other occurs increases almost linearly with the sulfur content from −90° to +90° C. 5. In the soft state the behavior of vulcanized rubber with respect to compressibility, thermal expansion, dielectric constant, and power factor, and probably other properties, resembles that of a viscous liquid; in the hard state, that of a solid. 6. Rubber with less than 2 per cent combined sulfur shows low dielectric constant and power factor over the whole temperature and frequency range investigated; hard rubber, only at room temperature, where its rigidity restricts the response to the field. 7. Hard rubber, although not an electret, can hold an electric charge for 24 hours or more. The low dielectric constants of high-sulfur rubber samples found in measurements with a ballistic galvanometer were due to the disparity between its period of about one second and the long discharge periods of the samples. This led to the idea of dipole compensation shown to be incorrect by the high temperature results. 8. At temperatures sufficiently high to permit free response, the dielectric constant increases with sulfur content over the whole range. 9. If a dipole mechanism is involved, addition of sulfur to more than half the double bonds does not cause the dipole moment of the molecules to vanish owing to compensation. 10. The power factor of vulcanized rubber sheets decreases on stretch. 11. The data neither prove nor disprove a dipole mechanism. A critical experiment to settle this question is still wanting.
Heat-Resisting Inner Tube Stocks
Authors: Booth E. W.
Published: February 2011

A large number of laboratory tests were carried out which showed that to resist deterioration due to heat in an inner tube stock successfully, the following points should be observed: 1. Sulfur ratios should be very low. One per cent on the rubber content is sufficient for most stocks; some will require 1.2 per cent. This is true provided no sulfur-producing material is present. 2. When P33 Black or a similar soft black is used, 20 to 25 volumes are necessary. In the case of zinc oxide, blanc fixe, barytes, and the like, lower volumes will be necessary to obtain satisfactory resistance to tear. 3. The stocks should not be markedly overcured, especially if the cure is carried out at 50 pounds steam pressure (298° F.) or above. This is the opposite of former practice with stocks of higher sulfur ratio. 4. The accelerator chosen must be strong enough to combine practically all of the sulfur present, and yet should not be too scorchy to handle safely in the plant. 5. Tests showed that the use of 2 per cent of a good anti-oxidant was justified. One per cent gave good results, but especially when agings longer than 18 hours were carried out the stocks containing 2 per cent were markedly superior. 6. Zinc oxide, blanc fixe, barytes, or precipitated whiting can be successfully employed in stocks of this type. The modulus and tensile figures are lower than when P33 Black is used, but the losses in tensile strength due to air-bomb aging are comparable to P33 Black, and these fillers would permit the manufacture of colored tubes such as red, green, and yellow. 7. Heat-resisting inner tube stocks of this type compared to the ordinary tread, carcass, and tube stocks will necessarily be more scorchy, and care must be taken to cool the stocks properly in processing through the factory. The possibility of the migration of sulfur from the carcass stocks to the inner tube, or the migration of accelerator from the inner tube stock to the carcass stock must be taken into account. Today tire manufacturers are using as low as 2 per cent sulfur in the carcass stocks of bus and truck tires. These low sulfur ratios in the carcass stock tend to prevent the migration of sulfur. The usual Geer oven migration tests were carried out on stocks containing Ureka C as accelerator. The Geer oven was maintained at 93.3° C. (200° F.) for 14-day periods, and in no case did these tests show appreciable migration of sulfur or accelerator. Controls were run during the migration tests and alone.
Solubility of Organic Compounds in Rubber
Authors: Morris T. C.
Published: February 2011

While a few methods for solubility determination in rubber have been available, they are somewhat difficult and susceptible to large errors. A new method has been developed which has the advantage of being simple, rapid, and accurate, and applicable to all solids soluble in rubber. The apparatus developed can be used for any problem where microscopic observation at elevated temperature will yield information. The results thus far obtained are of use in explaining the peculiarities of certain organic compounds when used with rubber. It is hoped that sufficient data may be obtained to establish accurately the solubility properties of entire classes of compounds as well as mixtures of several components. In addition to molecular weight determination, the method may yield further results of theoretical interest.
Effect of Curing Temperature on Quality of Vulcanized Rubber
Authors: Shepard Norman A. , Street John N.
Published: February 2011

A review of the literature permits no definite conclusion concerning the influence of temperature of vulcanization on the ultimate quality of a rubber product. Some investigators claim equal properties at different curing temperatures, others superior properties at low temperatures, while still others believe superior qualities are obtainable at higher temperatures. Concerning the influence of temperature on aging, no conclusive data are available. The temperature of cure has no influence on the tensile properties at maximum, in the case of the di-o-tolylguanidine stock. In the case of the mercaptobenzothiazole stock, there is a trend toward slightly higher tensile strength as the temperature is decreased. Natural, as well as artificial, aging of the di-o-tolylguanidine slock shows that the lower the temperature of cure, the better the aging will be. The results are clean-cut, probably owing to the fact that this is a stock which ages rapidly and hence shows differences in comparatively short periods of aging. The data on the mercaptobenzothiazole stock containing an antioxidant are far from conclusive, though they show a trend toward belter aging with lower temperatures of curing.
Grit in Carbon Black. Effect on Flexing Resistance of Vulcanized Rubber
Authors: Street John N.
Published: February 2011

Rubber channel black has been found to contain amounts of grit retainable on a 325-mesh screen varying from 0.05 to 1.7 per cent. This residue is shown to be objectionable from the standpoint of the flexing resistance of the resulting rubber compounds, higher concentrations being correspondingly more harmful than lower concentrations. The coarser fractions appear to give rise to larger cracks and earlier appearance of cracking than the finer material. Even that which passes a 200-mesh screen but is retained on a 325-mesh is objectionable.
A Method for the Purification of Rubber and Properties of the Purified Rubber
Authors: McPherson A. T.
Published: February 2011

Purified rubber was prepared by the digestion of crude rubber or latex with water at about 190° C., followed by extraction with water and with alcohol, and drying in an atmosphere of inert gas. The digestion hydrolyzed the proteins, and the extraction removed the hydrolysis products, resins, and other impurities. The purified rubber contained about 99.5 per cent of rubber hydrocarbon. Properties of the rubber hydrocarbon at 25° C. were: density, 0.9060; refractive index, 1.5184; dielectric constant at 1000 cycles per second, 2.37; power factor at 1000 cycles per second, 0.0015; conductivity at the end of 1 minute, 2.2×10−7 mho. The electrical properties measured on 14 samples were apparently independent of the botanical source or the kind of crude rubber.
Natural and Synthetic Rubber. IX. The Products of Destructive Distillation of Ebonite
Authors: Midgley Thomas , Henne Albert L. , Shepard Alvin F.
Published: February 2011

The following compounds have been identified in the products obtained from ebonite by destructive distillation: 2-methylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-methylethylthiophene and m-xylene. These results will be used to derive the structural formula of ebonite.
Natural and Synthetic Rubber. XI. Constituents of the Milled Rubber Hydrocarbon
Authors: Midgley Thomas , Henne Albert L. , Renoll Mary W.
Published: February 2011

The composition of milled rubber has been investigated by a method based on fractional precipitation from a benzene—alcohol mixture. This has shown that milled rubber is made of a continuous series of undefined components, without a single predominating individual. The same method had previously shown that one single individual constituted more than one-half of unmilled rubber.
Studies of Polymers and of Polymerization. VI. The Vulcanization of Methyl Rubber
Authors: Whitby George Stafford , Katz Morris
Published: February 2011

Samples of synthetic rubber prepared by the polymerization of dimethylbutadiene at room temperature and at 45° C., respectively, were subjected to vulcanization tests in comparison with natural rubber. In an accelerated gum stock containing 3% sulfur the cold polymer gave at best vulcanized products less than one-third as strong and only about one-third as extensible as natural rubber; the heat polymer gave products as extensible but only one-tenth as strong as natural rubber. The incorporation of carbon black greatly increased the strength of the synthetic rubbers, rendering both about one-half as strong as natural rubber in a similar stock. The vulcanized synthetic rubbers were less “snappy” than natural rubber at room temperature. Increase of temperature improved their speed of retraction, but seriously reduced their breaking strength. Products from the cold polymer showed a greatly increased stiffness and strength at 5° C. as compared with room temperature, and at about 1° C. were non-retractible. In general the synthetic rubbers were much more sensitive than natural rubber to change of temperature. A 50:50 mixture of the heat and cold polymers was also subjected to tests.
The Oxidation of Rubber Gutta-Percha and Balata with Hydrogen Peroxide
Authors: Mair John A. , Todd John
Published: February 2011

The behavior of rubber toward hydrogen peroxide was studied first by Boswell, McLaughlin, and Parker (Trans. Roy. Soc. Can., 16, 27 (1922)) and more recently by Robertson and Mair (J. Soc. Chem. Ind., 46, 41t (1927)). The earlier workers, using a solution of rubber in carbon tetrachloride, isolated a compound, C30H48O, which they found to absorb atmospheric oxygen and yield another compound, C25H40O2. The later workers adopted a modification of the usual method of hydrogen peroxide oxidation of terpene hydrocarbons and employed a chloroform solution of rubber, to which glacial acetic acid was added. They obtained a product, alcoholic in character, of the empirical formula C59H102O16. The present work was commenced with the object of extending the latter work to include gutta-percha and balata. Certain changes were introduced and new avenues of investigation opened up, and it was thought desirable to extend the scope of the work to include rubber so that each of the three substances, rubber, gutta-percha, and balata, and corresponding derivatives of them, might be submitted to as nearly as possible identical reaction conditions.
The Law of Absorption of Carbon Dioxide by Rubber as a Function of the Time
Authors: Cheneveau C.
Published: February 2011

1. As the form of the curves shows, factice does not appear to obey the law for rubber. Calculations give values which, in relation to the observed values, show deviations of 8.5 per cent for brown factice and 13.7 per cent for white factice, whereas Table I gives smaller deviations for the different rubbers. 2. Crude rubber absorbs more than the same rubber cut into pieces, which indicates that the latter has become less porous. The absorption measurements can therefore give an idea of the porosity. It is a curious fact that if crude or cut-up rubber is boiled with alcohol the same value for the coefficient of absorption is obtained. 3. Vulcanized rubber or rubber mixed with mineral or organic fillers absorbs carbon dioxide in the same way. 4. Although Reychler has assumed that carbon dioxide dissolves in rubber, it should be noted that the law of the phenomenon of absorption is identical to that of monomolecular chemical combination. Might there not be formed therefore a compound with one of the components of the rubber? In any case, it is extremely difficult to remove the carbon dioxide from rubber, even after subjecting it to a vacuum for a long time. Moreover, if successive experiments are repeated on a single sample, it is found that the coefficients of absorption become smaller and smaller. This indicates that more and more carbon dioxide remains in the rubber. The coefficient of absorption for plantation rubber at the end of four tests changed from 0.165 to 0.141 and did not regain its value at the end of 50 days' standing. Upon washing the rubber at this stage, traces of carbon dioxide were detected in the wash water by means of lime water. 5. The study of the k coefficients, which may be called diffusion coefficients, likewise gives information about a rubber. 6. A sample left for one whole day in carbon dioxide did not appear to have altered, as judged by its elongation and tensile strength. 7. Without desiring to draw any definite conclusions from this work, it is believed that more complete tests such as those described would doubtless be of value in obtaining information about the constitution or the quality of different rubbers.
Studies on Rubber in Solution. I. Studies on the Aging of Rubber Solutions
Authors: Fujihara Takeo
Published: February 2011

It is well known that raw rubber in colloidal solutions with different dispersion mediums shows the general characteristics of aging such as a decrease in its viscosity, whether aged by natural or artificial methods, and especially when exposed to ultra-violet light. Whitby and Jane (Colloid Symposium Monograph, Vol. 2, page 16) pointed out this phenomenon, and Asano (Mem. Coll. Eng. Kyoto Imp. Univ., Vol. 3, page 267) noticed that dispersed rubber sols decreased in viscosity and the rubber depolymerized and became insoluble by exposure to ultra-violet light. This effect was particularly noticeable with light of 2250 A. U.; however, light of longer wave lengths caused oxidation of the rubber and formed a transparent insoluble substance. Recently Hada (Rubber Ind., 1931, 147) demonstrated the curves of decrease in viscosity of rubber sols by exposure to ultra-violet light, and pointed out that the sols reached a definite viscosity after long exposure. The theory generally accepted to explain the mechanism of the lowering of the viscosity of rubber sols on aging is that depolymerization results from the oxidation of rubber molecules, and thereby increases the degree of dispersion. The process as a whole involves the formation of a dispersed phase from the absorption of the dispersion medium, and after passing the stages of solvation the viscosity of sols thus formed decreases on aging. The principal cause of these phenomena is considered to be due to a change in the structure of the dispersed particles by a chemical change of the dispersed phase itself. Whether or not it is possible to obtain, in the laboratory, a stable rubber sol by the process of long aging is not certain. It is, however, no exaggeration to say that the oxidation of the dispersed phase causes a decrease in its affinity for the dispersed medium, i. e., the oxidation changes the emulsoid to a supersoid or, in other words, there is a decrease in the size of the particles in the dispersed phase if the theory of the aging of rubber sols is that there is an increase in the dispersity by depolymerization. The author subjected rubber sols to long exposure to ultra-violet light and measured the lowering of their viscosity. The results show that (1) rubber sols in benzene reached a constant viscosity, and (2) the use of different solvents causes marked differences in rubber sols. The Brownian movement of the particles in aged rubber sols was observed with a cardioid ultra-microscope. These experiments were made as a preliminary test to explain the mechanism of dispersion of raw rubber in solvents.
Investigations of Colloidal Solutions of Rubber. Part I. The Influence of the Precipitating Agent on Rubber Solutions
Authors: Kawamura Jiro , Tanaka Kunikiti
Published: February 2011

The nature of colloidal solutions of rubber is not yet fully explained in spite of the numerous investigations on the subject which have been carried out. It is well known that the viscosity of these solutions is diminished greatly by heating, by standing, by the action of oxygen and light, and by acids. In the present paper the influence of precipitating agents such as acetone and ethyl alcohol on the change in viscosity of rubber solutions at various temperatures was studied. Smoked sheet was used as the raw material. It was purified from its filtered benzene solution by precipitation once with alcohol and twice with acetone. An Ostwald viscosimeter of brown colored glass with a capillary diameter of 0.7 millimeter and 14.5 centimeters long was used.
The Nature of Vulcanization. Part V
Authors: Stevens H. P. , Stevens W. H.
Published: February 2011

(1) Diphenylguanidine, p-nitrosodimethylaniline, zinc isopropylxanthate, and benzoyl peroxide do not effect polymerization (vulcanization) of sulfur-free rubber in the presence of a small proportion of rubber sulfide. (2) In the presence of rubber sulfide, zinc diethyldithiocarbamate has a definite vulcanizing effect on rubber containing 1 per cent of combined sulfur. This effect is equivalent in magnitude to that produced by the presence of at least 0.5 per cent of free sulfur in the mixing, a much larger amount than could possibly have remained after exhaustive acetone extraction. The accelerator piperidine 1-carbothionolate has a similar but weaker effect. (3) The fact that a similar but lesser polymerization is induced by purified vulcanized oil, analogous to the “activation” of the accelerators by rubber sulfide and that the activities of the accelerators are in the same order in both cases, would indicate that vulcanization promoted by accelerators is partly a polymerization activated by the vulcanizing agent and its reaction product with the rubber medium. (4) It has been found that the smallest proportion of free sulfur to give a measurable vulcanizing effect in the presence of zinc diethyldithiocarbamate is of the order of 0.1 per cent.
Studies on the Combined Use of Two Different Accelerators. I. Diphenylguanidine and Mercaptobenzothiazole
Authors: Minatoya Shukusaburo , Kojima Kitaro , Nagai Izumi
Published: February 2011

1. The study of the effect of the combined use of mercaptobenzothiazole and methylene-aniline is based on its eutectic curve. 2. These two accelerators do not form a molecular compound on mixing, and they have only one eutectic point. The eutectic mixture gave a stronger accelerating action than did either of the ingredients alone, vulcanization proceeded smoothly, and the products were superior. 3. The scorching effect increased with increase in the proportion of mercaptobenzothiazole, but there was no evidence that the eutectic mixture gave any increased scorching. In general, the scorching effect was less when these two accelerators were used in combined form.