bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Light on the Color of White Rubber
Authors: Naunton W. J. S.
Published: February 2011

Defries and the writer published a note on the effect of sunlight on the color of cured and uncured mixings (Trans. Inst. Rubber Industry, 4, 248 (1928)) in which they ascribed the darkening produced by preliminary exposure to light as being due to a surface over-cure. Some time later Rimpel and Herrmann published a criticism (Gummi-Zeitung 43, 2270 (1929); see also (India Rubber J., 78, 943 (1929)) of this work, and contended that the discoloration of a rubber mix on curing after exposure to sunlight was a reduction phenomenon, and independent of state of cure. Rimpel and Herrmann made the following experiment: Four mixes were prepared, each consisting of rubber, lithopone, and zinc oxide. To the first of these sulfur only, to the second an accelerator, and to the third sulfur and accelerator were added; the fourth received no addition. After exposure to sunlight all the mixings were cured. It was found that the first and fourth mixings were unaffected, but the second and third mixings were discolored to the same extent. The inference was that the discoloration was due to the accelerator as such which behaved like the other reducing agents described in Rimpel and Herrmann's paper.
Studies in the Vulcanization of Rubber. II—Vulcanization of Rubber with Nitro Compounds
Authors: Blake John T.
Published: February 2011

The Kjeldahl method for nitrogen analysis can be adapted to the determination of combined nitrogen in rubber vulcanized with nitro compounds. The combination of nitro compounds with rubber has been followed in several cases. Strong evidence is given that the vulcanization is a chemical reaction. The density of rubber has been shown to change during vulcanization with dinitrobenzene. The change approximates the progress of the combination of the vulcanizing agent with rubber. The vulcanization of rubber with dinitrobenzene and trinitrobenzene is monomolecular. A theory of the mechanism of the vulcanization is advanced. The value of the stoichiometric method in estimating the molecular weight of rubber is discussed. Values of this constant are suggested by the data. Nitro compounds appear to be incapable of producing hard rubber. The amount of combined reagent is only a small fraction of that required for ebonite formation.
Solubility of Oxygen in Rubber and Its Effect on Rate of Oxidation
Authors: Williams Ira , Neal Arthur M.
Published: February 2011

It is apparent that an artificial aging test must consider the concentration of oxygen existing in the rubber. The concentration of oxygen in rubber suspended in air at 70° C. will be less than that required for normal oxidation at the maximum rate. This should limit the use of an air atmosphere to the highest quality of rubber in which the rate of oxidation is extremely small in comparison with the rate of diffusion of oxygen, and in this case tests should be confined to thin slabs. The solubility of oxygen in rubber suspended in oxygen at 70° C. and atmospheric pressure appears to be slightly greater than that required for uniform oxidation. Under these conditions thin slabs of good or medium-quality rubber should oxidize in a satisfactory manner. The fact that strips 4 mm. square of a rubber extremely sensitive to oxidation, when tested in an oxygen atmosphere at 26° C., produce deviation from a straight line would make doubtful the accuracy of tests conducted on easily oxidized rubber under these conditions. This type of rubber would require 2 or 3 atmospheres pressure in order to maintain the required oxygen concentration. The type of deterioration appearing at higher temperatures should have little influence unless high oxygen pressure is used. The use of both high temperature and high pressure may emphasize types of oxidation which are suppressed at ordinary temperature. Since little is known about this type of oxidation, it is believed that the simultaneous use of high temperature and high pressure should be avoided.
Structural Changes during the Processing of Rubber
Authors: Grenquist Ernst A.
Published: February 2011

The effect of mastication, heating in air, oxygen, steam, and carbon dioxide gas, and the influence of light upon the plasticity of crude rubber have been investigated. Cold milling causes a permanent change in the consistency of crude rubber, whereas heating in air or steam produces a temporary effect. In absence of air the rubber exhibits a maximum amount of disaggregation at each given temperature. At low temperatures the increase in plasticity proceeds at practically the same rate whether the rubber is heated in oxygen or in carbon dioxide. Ultra-violet light affects concurrently both the plastic and elastic properties of the rubber. The correlation between elasticity and double refraction of crude rubber has been shown. The anisotropic properties of rubber parallel the recovery values. In this investigation no agency has been found which causes such far-reaching and profound destruction of the elastic properties of the rubber as prolonged physical mastication. The interrelation between plasticity and structure of crude rubber has been studied and the fundamental difference between actual mastication and heat breakdown has been emphasized. Prolonged milling, heating in air, or in oxygen destroy the protein framework of the rubber. Heating in steam or in an inert gas leaves it more or less intact.
Behavior of Various Clays with Crude and Reclaimed Rubber
Authors: Winkelmann H. A. , Croakman E. G.
Published: February 2011

1—The chemical analysis of clays gives but little information regarding their behavior in crude or reclaimed rubber. Acidity or alkalinity should be determined for effect on rate of cure. Color of the clay is no criterion of its purity. 2—Clays show wide variations in plasticity, retentivity, and softness in crude and reclaimed rubber. 3—Commercial clays vary widely in their effect on the physical properties of crude and reclaimed rubber. In general, the effect of the clays is the same in reclaimed as in crude rubber. There is not quite the percentage variation in tensile strength in reclaimed rubber that there is in crude rubber. The alkalinity of the reclaim may have decreased the variation. 4—Bomb aging is an important test for differentiating between various clays. 5—The uncured as well as cured properties of a compound should be noted in compounding and processing various samples. 6—Microscopic examination of clays makes it possible to predict their effect on the uncured and cured properties in both crude and reclaimed rubber.
Method of Making Micro-Sections of Rubber Stocks
Authors: Allen Raymond P.
Published: February 2011

THE possibility of seeing pigment particles in a rubber stock has always been a desire of rubber chemists. There has been a natural belief that if the particles in rubber could actually be observed with a microscope more could be learned about their action and properties. The main difficulty in attaining this end lies in the preparation of sufficiently thin sections. For clear observation of highly loaded gas-black stocks the sections must be less than 1 micron thick. For bright-field work with light-colored or colorless pigments, such as litharge and zinc oxide, the sections may be somewhat thicker. However, if the examination is to be made with dark-field illumination the sections for even the colorless pigments must again be very thin. Several methods have been proposed and utilized for making thin sections, and the names of Dannenberg (2), Depew (3), Green (4), Grenquist (5), Hauser (7), Moore (11), Pohle (9), Ruby (3), Spear (11), and Walton (12) are identified with the skilful manipulation which is necessary for achieving the desired result. There have been many other workers in this field, including Weber (13), Breuil (1), Loewen (8), Regnaud (10), and Hardman (6). The method to be described was developed in this laboratory in 1926. It has been used continually since that time and has proved valuable in the study of rubber compounds and pigments. While it bears a slight similarity to some of the other methods, it has certain unique and distinct advantages of its own.
The Infrared Absorption of Rubber and Related Hydrodcarbons
Authors: Williams Dudley
Published: February 2011

The infrared absorption spectra of rubber and certain related hydrocarbons have been studied by using extremely thin films of the samples as absorbing layers. In the spectra of styrene, isoprene, and cymene intense absorption bands appear at 3.4µ, 6.2µ, and 7.0µ and also weaker bands between 7µ and 9µ. These bands were common to most of the hydrocarbons studied. The principal variations in the spectra of the compounds mentioned above are found in bands whose positions vary between 5.5µ and 5.7µ in the different compounds. In the case of “pure gum” rubber a band was found at 5.8µ and in a vulcanized rubber of low sulfur content corresponding absorption occurs at 6.0µ. At all other wave-lengths between 2.5µ and 9.0µ the absorption spectrum of rubber has a striking resemblance to that of isoprene, a result which is in agreement with the chemist's model of the rubber molecule as a long chain of isoprene units. The absorption in the 5.8µ region probably arises from a mechanism which is intimately connected with the process of polymerization. The spectrum of polymerized butadiene contains strong bands at 5.5µ and 6.0µ and also less intense bands beyond 7.0µ, whose positions are not the same as those in the spectrum of natural rubber. Rubber hydrochloride has a very intense band at 8.4µ which is not characteristic of the other hydrocarbons studied.
Studies of Hard Rubber Reactions III. Changes in the Acetone Extract during Vulcanization
Authors: Numaziri Seiiti
Published: February 2011

In the former communications (Part I and Part II) the author dealt with the characteristic changes in some physical properties with time of cure of hard rubber compounds. The work has now been extended by chemical observations. In the first place, the author studied the acetone extract of the same compounds of the previous reports with a view to ascertaining the nature of the hard rubber reactions. Preliminary Examination of the Acetone Extract Samples were prepared for acetone extraction in two ways. In the case of soft rubber products, the material was sheeted out to thin crepe by passing between the tightly closed rolls of a laboratory mill and was then cut with scissors into fine strips. Hard rubber samples were prepared by buffing with an alundum grinder and sifting through a 100-mesh screen. In each case the sample taken for the extraction was 0.5–1.0 gram. The extraction apparatus was a new design, as illustrated in Fig. 1, which has the advantage of extracting the sample in the vapor of boiling acetone, and in many other respects is more efficient and convenient than the Cottle type of extractor. There has been considerable discussion as to a standard time of extraction for hard rubber. According to the specification of the Society of Rubber Industry of Japan, for example, extraction of at least 48 hours is recommended, while it is specified in the British Standard Specification No. 234 (1933) that only 8 hours of continuous extraction are necessary for ebonite for electrical purposes. Besides these, extraction periods of 72 hours, 20 hours, etc., have been advocated by various authors.
Studies on the Artificial Aging of Vulcanized Rubber. I. Depolymerization during the Heat-Aging
Authors: Nagai Hiroshi
Published: February 2011

1. Aging in nitrogen results in very little deterioration below about 80° C., whereas deterioration is rapid above this temperature. 2. There is no metamorphic point in the curve representing aging in nitrogen. 3. During aging in air below 80° C., disaggregation is brought about by oxygen, aside from an independent effect of sulfur; above this temperature depolymerization takes place through the agency of heat. Depolymerization and disaggregation are most rapid at the metamorphic point.
The Errors in Tensile Strength Testing
Authors: Davies O. L. , Horrobin S.
Published: February 2011

The conclusions drawn from the data of Wiegand and Braendle and of Fric that the breaking of rubber during tensile strength testing is essentially an event governed by the laws of chance, and that therefore some form of average is the only appropriate method of estimating the “correct” result from a number of tests is supported by the nature of the data obtained in routine testing in the rubber service laboratories. The presence of an excess of abnormally low values and of a few high values is also confirmed. After calculating the standard error of a test, a rule has been devised for eliminating abnormal results before averaging the remainder. This rule is to be preferred to any of the various arbitrary rules hitherto in use. The authors wish to acknowledge the help given by the staff of the rubber service laboratories in collecting data for this investigation, and to Imperial Chemical Industries, Ltd., for permission to publish the results.
Hot vs. Cold Breakdown of Rubber
Authors: Comes D. A.
Published: February 2011

The value of, and methods for, breaking down crude rubber have been the subjects of much opinionated discussion among rubber men of many generations. The questions normally center about such points as the kind of equipment and its best adjustment; time, temperature, and sequence of conducting operations; methods of measuring the degree of softness obtained; and the quality of the crude rubber and finished product, both unaged and aged. Time has brought a reasonable unanimity of opinion on some points, for example, the efficacy of a series of short breakdown periods on an open mill, with intermittent intervals of cooling, compared with a single long period of continuous mastication. Among other points not in common agreement, hot vs. cold breakdown takes a prominent position. Here differing viewpoints not only exist between various plants, but between different persons of the same plant and even of the same laboratory. If an attempt is made to compare results in different plants, one will find it difficult to draw any definite conclusions, owing to differing conditions of physical manipulation and measurements, not the least of which are the various types of plastometers used. Because of this set of conditions the present author was prompted to conduct a series of experiments with the object of obtaining data with which the relative plasticizing effects of different methods of breaking down rubber over the, greatest practicable temperature range on both open mills and in internal mixers could be evaluated.
The Components of Hevea Latex. Part I. The Isolation and Quantitative Determination of the Components
Authors: Roberts K. C.
Published: February 2011

(i) A method is described for the quantitative isolation of the chief components of Hevea latex in the form in which they occur in nature. (ii) Several hitherto unknown components have been observed, and receive a preliminary description. They include a sulfur-containing plastic material which is of major importance. (iii) The known major components—sugar, quebrachitol, phosphates, protein, fat acids—are shown to exist in fresh latex, chiefly as components of stable chemical complexes. (iv) It is hoped in the near future to report the results (a) of more detailed investigations, and (b) of applications of the method in the study of some fundamental problems.
Properties of Hard Rubber. I. Plastic Deformation
Authors: Church H. F. , Daynes H. A.
Published: February 2011

Tests have been made at temperatures from about 15° to 100° C. on (a) subpermanent set due to torsion; and (b) rate of plastic flow under torsion, of a number of commercial and specially made hard rubbers, the latter consisting of rubber and sulfur with or without high grade hard rubber dust. Temperature-set curves showed marked maxima at temperatures, depending mainly on the vulcanization of the sample and comparatively little on arbitrary conditions of test. The peak temperature rose with advancing vulcanization, but reached a limit when combination of sulfur had practically ceased. Hard rubber dust depressed the peak temperature and introduced a second peak at a higher temperature, both peak temperatures rising with advancing vulcanization. Vulcanization-set curves also showed sharp maxima except at the highest temperatures, but became flat when combination of sulfur had practically ceased. Rate of flow under a torsional stress sufficient to give a fixed initial twist showed substantially the same characteristics as the set after torsion. It is concluded that at an early stage in vulcanization hard rubber acquires an elastic structure which becomes the dominant control at high temperatures, the plastic structure being dominant at low temperatures. Some practical consequences of these results are discussed, relating to testing of materials for plastic deformation, methods of manufacture to avoid after-shrinkage, detection of hard rubber dust, and investigation of changes of structure during vulcanization.
Softening and Freezing of Crepe
Authors: Messenger T. H. , Scott J. R.
Published: February 2011

The outstanding results may be summarized as follows: (i) Heating gristly crepe to 60° C. or above causes softening, a change characterized by a large fall in tensile strength and rigidity and by increase in breaking elongation and permanent set. With some crepes there is a transient initial rise in tensile strength. Subsequent storage at 0° C. produces changes in the reverse direction, which, however, are rapidly eliminated by heating at 34° C. or above. It appears, therefore, that heating above 60° C. produces: (a) a permanent change not reversible by freezing; and (b) a temporary change reversible by freezing. (ii) Heating gristly crepe below 50° C. only moderately increases the extensibility and flexibility, true softening being absent. These changes are reversible by freezing, the recovery being quicker than with softened crepe. (iii) Prolonged storage at 0° C. (beyond 20–30 days) causes a gradual decrease in strength and stiffness in both gristly and softened crepes. With gristly crepe these effects are more than counteracted by thawing at 25° C., giving a tougher, stronger product than the original. (iv) The statement that golden crepe does not harden is incorrect; as, however, this is a softened crepe the hardening is only temporary and does not restore the original gristly qualities. (v) Uniform temperature and rate of elongation are essential in tensile tests on raw rubber. The permanent set of broken rings becomes sensibly constant in 2 hours.
Chemical Aspects of Vulcanization
Authors: Rossem Avan
Published: February 2011

C. O. Weber was the first to give an elaborate theory of vulcanization. It is well known that he considered the hot vulcanization process as an addition of sulfur to polyprene (C10H16)n on account of the fact that no large amounts of hydrogen sulfide were evolved during the process. Wo. Ostwald, starting from quite the opposite point of view to Weber, put forward in 1910 the adsorption theory of vulcanization, considering it from an entirely colloidal standpoint, the sulfur being adsorbed by the rubber. It soon became clear that vulcanization was much more complex, and that neither of the two theories was able to explain the facts. Since then many investigations have been carried out, and many views, hypotheses, and theories on vulcanization put forward. If one tries to classify these, it becomes apparent that at the present time there is still a chemical theory and a colloidal theory of vulcanization. The chemical theory of vulcanization may be divided in two opposing hypotheses, viz.: (a) Polymerization of the rubber molecule, combination with sulfur being incidental. (b) Chemical combination of sulfur with rubber as the principal factor. To support this statement a few references and quotations from various investigators are given below.
Concerning the Alleged Absorption of Gaseous Nitrogen by Benzene Solutions of Rubber and Gutta-Percha Hydrocarbons
Authors: Howard Louis B. , Hilbert Guido E.
Published: February 2011

Experiments described by de Jong have been interpreted as indicating that dilute benzene solutions of rubber or gutta-percha hydrocarbon from sheet balata, when exposed to sunlight for a few days in either quartz or ordinary glass vessels, absorb gaseous nitrogen in appreciable amounts. If such a photochemical combination of rubber and nitrogen actually occurs, one might reasonably expect other unsaturated hydrocarbons containing isoprene units such as carotene and xanthophyll to behave similarly. These substances which always are found closely associated with chlorophyll in green plants possess physiological functions which, as yet, remain quite obscure. It therefore seemed of very great importance from both a theoretical and a practical standpoint to attempt to confirm these results of de Jong. In the present study the experimental procedure of the original investigation was followed as closely as the description of the work allowed. Several variable factors, such as temperature, barometric pressure, vapor pressure of the benzene solutions, and the heating effect of sealing the tubes, were controlled. In one experiment Pyrex tubes of 150-cc, capacity were filled with 100 cc. of nitrogen gas and 50 cc. of benzene solutions containing about 0.5% of either pale crepe rubber or balata. After sealing, these tubes and a benzene control were exposed to direct sunlight during the summer for various lengths of time up to five weeks. At the end of the tests the changes in volume of the nitrogen in the tubes containing the rubber solutions differed from that of the benzene control by a maximum of 0.5 cc. which was found to be about the limit of experimental error.
The Stability of Abiarana Gutta-Percha Latex
Authors: Daniel F. K. , Freundlich H. , Söllner K.
Published: February 2011

1. The latex of Abiarana gutta-percha is more stable than that of Hevea. In the absence of preservatives Abiarana latex is stable for many months, while Hevea coagulates readily in a few hours. On addition of electrolytes, Abiarana only creams up and is readily and reversibly redispersed; Hevea is coagulated jrreversibly. Under the influence of the electric current Abiarana does not form a coherent skin on the anode; Hevea does so easily. 2. The stability of Abiarana latex is due to a protecting substance reversibly adsorbed on the particles. This substance may be removed by allowing the particles to cream-up repeatedly and by separating the serum from the particles. The serum of Abiarana (or the whole latex) added to Hevea latex strongly protects the latter and causes it to behave like Abiarana latex. 3. A similar protecting action in small concentrations cannot be produced by substances such as gelatin, peptones, lysalbinic acid, starch, etc. The chemical nature of the protecting substance could not be identified. It must have a large molecular weight, since it does not diffuse through membranes. 4. The reversible creaming-up of Abiarana latex is influenced by the cations of the electrolytes added according to their valency, in agreement with the fact that the particles are negatively charged. H+-ion and ter- and tetravalent cations are able to reverse the electrical charge of the particles. 5. The difference in creaming velocity due to different electrolyte concentrations (i. e., to different degree of discharge) seems to depend on time average size and number of aggregates of particles which are formed.
A Study of Deproteinized Rubber
Authors: Okita Tadao
Published: February 2011

In Part I we assumed that deproteinized rubber would deteriorate more rapidly than washed smoked sheet. But the present experiments indicate that our supposition was not correct, because the former was more resistant than the latter to mechanical deterioration. The same result was true of the specially treated rubber. It can be assumed that this depends on differences in the aging of the rubber hydrocarbon itself. But for several reasons, it is more likely that the major causes are differences in impurities and uniformity of cure. From several reports concerning protein in crude rubber by Stevens and others (Stevens, Kolloid Z., 14, 91 (1914); Park and Sebrell, India-Rubber J., 73, 265 (1927); Pickles, Trans. Inst. Rubber Ind., 3, 60 (1927)), water-soluble protein would have an immense effect on deterioration. Depolymerization and disaggregation would be the cause of deterioration by the aging of vulcanized rubber. This depolymerization, especially in artificial aging, cannot be explained merely by oxidation of the unsaturated part of the molecules, but must be attributed also to oxidation of combined sulfur, the formation of hydrogen sulfide, oxidation or other change in the free sulfur, metallic salts, proteins, and abietic acid. It has already been shown that oxidizability increases with increase in the time of cure, and that there is no relation between oxidizability and optimum cure. It has also been found that addition of acid to rubber decreases the heat deterioration (unreported experiments). Moreover, it has been found that resistivity to deterioration is increased by smoking and that the most easily oxidizable mixes contain in the neighborhood of 7 per cent of combined sulfur (cf. Kohman, J. Phys. Chem., 31, 23 (1927)), lower percentages of combined sulfur resulting in greater resistance to deterioration (cf. Boggs, Ind. Eng. Chem., 22, 748 (1930)).
Deproteinized Rubber
Authors: Boggs C. R. , Blake J. T.
Published: February 2011

FOR some years deproteinized rubber has been used by this company in the manufacture of rubber insulation, and the rate of consumption is increasing rapidly. This new and unique raw material is now also being manufactured for the Simplex Wire and Cable Company by The Goodyear Tire and Rubber Company on plantations in the Far East. The special virtue of deproteinized rubber is its low water absorption and the electrical stability which it imparts to vulcanized rubber compounds immersed in water. Electrical engineers are specifying such compounds for submarine, underground, and duct cables and all other insulation that may be exposed to water. The electrical properties of ordinary rubber insulation are impaired by increasing water absorption; the dielectric strength decreases, and the capacitance and leakance (or dielectric loss) increase. Power cables become useless when decreasing dielectric strength is insufficient to withstand operating voltage. Communication cables deteriorate rapidly by water absorption because their increasing capacitance and leakance prevent the practical transmission of signals long before dielectric strength is low enough to cause failure at the extremely low operating voltage of such cables.
Transparency of Rubber Compounds Containing Magnesium Carbonate
Authors: Bixby W. F. , Hauser E. A.
Published: February 2011

1. Basic magnesium carbonates of the type 5MgO·4CO2·xH2O will produce transparent vulcanized rubber. 2. Neutral carbonates of the magnesite type result in stocks of poor light transmission, even at low loading. 3. The basic carbonates, although of extremely fine particle size, are definitely crystalline in structure, as revealed by x-ray analysis. 4. The sample of magnesium carbonate producing the best transparency was a Japanese variety. When 25 per cent by weight was compounded in rubber, an over-all transmission of 45 per cent was produced. None of the domestic varieties gave higher than 36 per cent, and only two samples out of the eighteen examined produced this value. 5. The best Japanese carbonate (sample 3) and the best domestic carbonate (sample 9) possessed the same structure— that of a basic magnesium carbonate of the general form type 5MgO·4CO2·xH2O. 6. The Japanese carbonate, corresponding to the formula type 5MgO·4CO2·6H2O, gave higher total light transmissions at low filler concentrations than the best domestic carbonate, corresponding to the formula 5MgO·4CO2·9H2O. 7. Mixes containing between 25 and 40 per cent by weight of basic magnesium carbonate passed the greatest amount of undeviated light. 8. The amount of undeviated light passed by samples compounded with good Japanese magnesium carbonate and good domestic carbonate was essentially the same between 25 and 40 per cent filler—about 22 per cent. 9. The tensile strength of compounds containing domestic carbonate was higher in the 25 per cent filler range than that of mixtures containing Japanese carbonate.
The Oil Resistance of Rubber. IV. Mechanism of the Oil Resistance of Neoprene
Authors: Kambara Shĭ
Published: February 2011

To study the mechanism of the oil resistance of Neoprene, the following points were investigated. 1. The dielectric properties of Neoprene and its comparison with the crude and purified natural rubber. 2. The viscosity of benzene solutions of Neoprene and natural rubber of various concentrations. From data on the relation between polarization, the chain-length of solute and the concentration, the state of solutes in solution was discussed, and the oil resistance of Neoprene is explained on the basis of its high polarization and its complex structure. In conclusion, the author wishes to express his thanks to Professor Yoshio Tanaka for valuable suggestions and criticisms.
Impact Machine for Rubber Testing. Determining the Stress-Strain Diagram at High Speed
Authors: Albertoni Geo J.
Published: February 2011

IN CONTRAST to the ordinary standard procedure at low speed, various methods have been devised to carry out tensile tests of rubber under rapid application of load, with the purpose of securing more definite indications, at a speed in agreement with actual performance. The application of those methods to the study of the tensile properties of rubber stocks goes as far back as 1910, when Beadle and Stevens (1) made use of the pendulum to investigate these properties. Their work applied to rubber compounds of different compositions and different loadings. More recently, Van Rossem and Beverdam (2) presented a set of results tending to prove an optimum in the tensile properties, coinciding with the best cure as determined by practical observation. However, all experiments, previous to those here reported, are limited to the determination of the tensile strength of rubber, and no attempt was made to extend the investigations to the determination of the resistance of rubber at different elongations. The machine here illustrated is designed to measure not only the energy absorbed at break, under conditions of high speed, by impact, but also the stress-strain relation.
Vulcanization Characteristics of Mercaptobenzothiazole Derivatives
Authors: Harman M. W.
Published: February 2011

WITHIN the past few years much progress has been made in the development of rubber vulcanization accelerators of the semi-ultra type which exhibit no prevulcanization or scorch during the preliminary processing. Most of the commercially important members of this class are derivatives of mercaptobenzothiazole in which the hydrogen atom of the mercapto group is replaced by an organic substituent. The increasing use of these products can be attributed to their favorable curing characteristics and to the valuable physical properties which they impart to the cured stock. Naunton and his co-workers (4), Twiss and Jones (8), and Shepard (6) discussed a number of these compounds in recent papers. Numerous references to their preparation and use also appear in the patent literature (1,2,3,5,7,10).
Latex Battery Separators. Preparation and Properties
Authors: Greenup H. W. , Olcott L. E.
Published: February 2011

THE commonly used electrical storage battery consists of alternate negative plates of sponge lead and positive plates of lead peroxide immersed in an electrolyte, sulfuric acid; the whole is enclosed in a hard rubber or bituminous composition case. These plates are ordinarily separated from one another by ribbed sheets of wood called “separators.” The separators prevent short circuiting of the plates caused by actual contact of the plates with each other or by “treeing” (formation of lead crystals between the plates). The separators must be thin, in order to make the battery as compact as possible, and yet must be durable. It is necessary that they be highly porous so that their electrical resistance will be low, but the pores must be sufficiently fine so that “treeing” does not take place. Wood separators are ordinarily made of Port Orford cedar. They are usually given a preliminary treatment in warm, dilute sodium hydroxide solution to swell them, thus increasing their porosity, and to remove injurious substances which cause self-discharge and corrosion of the plates. Wood separators have the advantage of being inexpensive and of having fairly low electrical resistance, but they are not so resistant to the action of sulfuric acid and the oxidizing action in the cell as is desirable. They are, in many cases, the first part of the storage battery to fail and must then be replaced if the battery is to give further service.
Kaysam. A Casting Process for the Manufacture of Rubber Products from Latex
Authors: Cutler David Roy
Published: February 2011

Various practicable methods of applying the solids of latex and latex mixtures in the manufacture of various types of products have been employed in this country during the past years. While meritorious within their respective fields, these processes, except that for the production of sponge rubber, all have the common limitation of being applicable only to comparatively thin articles of relatively uniform thickness. The recent introduction into this country of an important English invention, Kaysam, supplies the positive three-dimensional shrinkage control and accelerated drying method, which now opens new fields to all types of products with superior strength, stretch, tear-resistance, aging, and advantages characteristic of articles made directly of latex. The Kaysam Development Confronted with the conflicting problems of distressing competition and the necessarily wasteful and uneconomic methods of producing crepe rubber soles, Walter Kay, of Sam Kay & Co., Bury, England, despaired, of meeting the problem except by some workable substitution of latex for crepe rubber. The result of his experimental effort was a workable process of casting liquid latex into rubber articles without limitation of size or shape. This process became known as “Kaysam,” a contracted inversion of his company's name. This process has been applied in England during the past several years, and in various continental European countries to the volume production of many types of soles, metal-inserted heels, cloth-inserted boots, and various kinds of molded articles, including those of solid and hollow construction. More recently still, Kaysam, supplemented by other important inventions of prominent American technologists relating to the fundamentals of latex compounding and use, has been made available to manufacturers in this country by the Kaysam Corporation of America.
Physical Testing Procedure for Latex Stocks
Authors: Wohler L. A.
Published: February 2011

Adjustment of stabilizers may be necessary in order to produce a smooth surface on an air-dried latex test slab. A combination of 1 per cent of casein and 1 per cent of Aquarex D on the rubber gave a satisfactory dried slab. Reproducible results cannot be obtained unless the test strips are conditioned at controlled relative humidity conditions. Zero per cent humidity gave highest tensile and modulus figures. Batch-to-batch accuracy of latex stocks using methods described herein was comparable to that of mill-mixed pure gum stock.
Examination of Rubber Latex and Latex Compounds. Part II. Chemical Testing Methods
Authors: Fowler D. E.
Published: February 2011

LATEX compounds are purchased either on the basis of total solids content or the so-called dry rubber content. The total solids probably furnish a more reliable basis of evaluation, as the determination can be made with a high degree of accuracy. The dry rubber content is not a precise determination, as the proteins, fatty acids, and other non-rubber constituents are included, and in the case of compounded latices some of the compounding materials are included in the value and some are not. Hauser (8) and Noble (9) include in their books useful chapters on testing latex. Total Solids The total solids are determined by weighing about 2 grams of the sample in a low covered weighing dish about 6.25 cm. (2.5 inches) in diameter on an analytical balance. A metal weighing dish is preferred for more rapid drying. Tinned 60-ml. (2-ounce) ointment cans are satisfactory and so inexpensive that they may be thrown away if they are at all difficult to clean. The sample is dried, preferably in a vacuum oven. The temperature may be increased to 120° C. in a vacuum without any apparent oxidation or deterioration of the rubber. A sample of normal latex may be completely dried in about 10 minutes if the drying arrangement is right. Results are accurate to better than 0.1 per cent. Methods involving the use of specific gravity are worse than useless when applied to preserved latex as a concentration control. Even in the case of unpreserved, unwatered normal latex on the plantations, the hydrometers must be calibrated especially for the latex from the estate on which they are to be used.
An Air-Bomb Aging Test for Tread Compounds
Authors: Booth E. W. , Beaver D. J.
Published: February 2011

Data here presented demonstrate that study of tread compounds by the air-bomb aging method must include modifications of the conditions followed in the comparison of inner-tube compounds. Data are presented which show the effect of air pressure, temperature, elongation, oxygen concentration, time, and pigment variation on the aging of rubber compounds. The air-bomb aging conditions suggested for the study of tread compounds, consisting in testing at 0 elongation, 50 pounds air pressure per square inch (3.5 kg. per sq. cm.), and 220° F, (104.4° C.) temperature, have provided a shorter laboratory teat which parallels the Geer-oven aging test in its effect on carbon black compounds.
Determination of Diarylamines in Rubber Compositions
Authors: Craig David
Published: February 2011

THIS paper deals with semi-quantitative methods for the determination of certain typical diarylamine age resisters—namely, diphenylamine, phenyl-α-naphthylamine, and N,N′-diphenyl-p-phenylenediamine. It serves as an essential feature of a study of the general behavior of these materials in rubber to be discussed in a subsequent communication. Previous methods for the detection and estimation of rubber age resisters have been of limited though of useful application. Thus Endo^ (3) described the colors produced by the action of sulfuric acid on a large number of commercial age resisters unmixed with rubber. Later Endo^ (4) published papers dealing with the action of concentrated nitric acid and Erdman reagent (solution of 0.5 ml. of concentrated nitric acid in 100 ml. of concentrated sulfuric acid) as well as of Mandelin reagent (solution of 1 gram of ammonium vansdate in 200 grams of concentrated sulfuric acid) and of concentrated sulfuric acid containing 1 per cent of arsenic acid.
Change of Volume of Rubber on Stretching: Effects of Time, Elongation, and Temperature
Authors: Holt William L. , McPherson Archibald T.
Published: February 2011

1. Two dilatometers have been described which are suitable for measuring the change of volume of rubber on stretching. 2. The volume of pure gum rubber remains constant up to a critical elongation, above which it decreases. Coarse fillers and other inhomogeneities tend to increase the volume because of the formation of vacuoles on stretching. Carbon-black compounds, however, decrease in volume above a critical elongation, which is lower than for pure gum. 3. The decrease in volume of rubber on stretching is greater the higher the elongation, the lower the temperature, or the longer the time the rubber is kept stretched. 4. After the first few minutes the volume of stretched rubber decreases at an approximately uniform rate with the logarithm of the time. No final or equilibrium state was attained in periods up to 3 or 4 weeks. 5. Stretched rubber shows a greater coefficient of expansion than unstretched rubber. 6. Poisson's ratio for rubber in the absence of coarse fillers is 0.5 or greater, the numerical value being a function of the composition, the elongation, the temperature, and the time after stretching.
Isoprene and Rubber. Part 46. Viscosity Measurements of Gel Solutions of Rubber and Hydrorubber
Authors: Staudinger H. , Mojen H. P.
Published: February 2011

I. RELATIONS BETWEEN VISCOSITY AND CONCENTRATION WITHIN THE RANGE OF SOL AND GEL SOLUTIONS Rubber and hydrorubber belong to that group of colloids known as lyophylic colloids. They are characterized by the fact that their solutions are extraordinarily viscous, even at low concentrations, and follow neither the Einstein nor the Hagen-Poiseuille law. It was pointed out in previous works that this abnormal behavior of rubber solutions, as well as of many other natural and synthetic high molecular substances, depends on the long, thread-like form of their macromolecules. All these compounds belong to that class known as linear colloids. With these solutions the relationships between viscosity, particle size, and number of particles are far different from those of solutions containing spherical particles (spherocolloids), for which the Einstein law is valid. Of the many attempts which have been made to derive some law relating the viscosity and concentration of rubber solutions, the formulas of Arrhenius, Bingham, and Fikentscher and Mark may be mentioned. It is difficult to derive any general relation, because the state of rubber solutions may vary considerably with the size of the molecules and the concentration. This point has not been sufficiently taken into account in deducing previous formulas. The following three states of solution are to be distinguished, but it is self-evident that there are intermediate states between these.
Isoprene and Rubber. Part 47. The Decomposition of Rubber by Acids
Authors: Mojen H. P.
Published: February 2011

The phenomena observed in the experiments which have been described can be explained in the following way. As already mentioned, raw rubber contains certain antioxygens which protect the rubber molecules from attack by oxygen. Very little is known about the nature of these antioxygens, but it is probably correct to assume that these substances are of a basic nature, like commercial antioxygens, which for the most part are complex organic bases. The activity of these anti-catalysts is stopped by the addition of organic or inorganic acids. As a result there is no longer any obstacle to an attack by oxygen, and decomposition can proceed under these conditions much more rapidly and much more extensively. The antioxygens are destroyed by the acids, even when oxygen is excluded during the experiments, but demolition of the fiber molecules does not then take place. The intense destructive effect of oxygen on rubber does not therefore depend on the action of acids on the fiber molecules of rubber, but is to be attributed solely to the fact that antioxygens which inhibit decomposition by oxygen are destroyed; destruction of the rubber itself is caused only by oxygen. It is not impossible that these phenomena bear a close relationship to the stickiness acquired by rubber. Rubber which has become sticky is composed of extensively decomposed rubber molecules. This phenomenon is noticeable at times in rubber goods which have been stored for a long time, and may be explained by the fact that atmospheric carbon dioxide destroys the natural antioxygens in the rubber. With their destruction, atmospheric oxygen then has free play to attack the rubber molecules. The acidic substances which are formed in this oxidation then destroy any remaining antioxygens, so that oxygen can destroy all of the rubber. Grateful acknowledgment is due Professor Staudinger, at whose instigation this work was carried out, who offered advice in various ways, and who took an active part in the investigation.
Some Physical Properties of Isoprene
Authors: Bekkedahl Norman , Wood Lawrence A. , Wojciechowski Mieczyslaw
Published: February 2011

Isoprene (2-methyl-1,3-butadiene) has been for many years a substance of very considerable interest in the study of rubber, since it has been shown to be the fundamental unit in the constitution of the rubber hydrocarbon. Isoprene polymerizes to form a product which is chemically more closely related to natural rubber than any other synthetic product. Furthermore, the destructive distillation of natural rubber yields as its two major products isoprene and dipentene (dl-1-methyl-4-isopropenyl-1-cyclohexene) in amounts far exceeding those of any other constituents. Aside from its relation to rubber, isoprene is of interest, because it is thought to be the basic substance in the natural synthesis of terpenes and to play an important role in the formation of plant cells. An investigation of the chemical thermodynamics of rubber now in progress at the Cryogenic Laboratory of this Bureau includes a study of isoprene and its relationship to rubber. Measurements of heat capacity and heat of combustion are at present being made on isoprene for the purpose of calculating its entropy. A report covering these results is now being prepared. Similar measurements for rubber have already been reported. Since samples of high purity were desired for this work, care was taken in the preparation and purification of the isoprene, and the resulting product is thought to represent an improvement in purity compared with isoprene prepared by previous investigators. Furthermore, not all workers realized the importance of working with freshly purified samples. Also it is now possible to take advantage of recent important improvements in the technic of measuring physical properties, especially boiling point and related properties. In view of the wide divergence of values for many of the commonly measured physical properties, as reported in the literature, it seems worth while to report the values here obtained with samples of high purity.
Note on the Diffraction of X-Rays by Old Specimens of “Frozen” Rubber
Authors: Barnes William H.
Published: February 2011

The object of the present note is to make available in the literature a detailed comparison of the x-ray diffraction effects from old specimens of “frozen” rubber with available data for stretched fresh rubber. Several x-ray diagrams of “frozen” rubber have been published, and Ott has recorded measurements made on a photograph of apparently “frozen” crepe. Although Ott's values have been confirmed in Clark's laboratory, they appear to be the only values readily available in the literature, and are rather meagre.
Chlorination of Polymers of Chloroprene Rubber
Authors: Klebanskiĭ A. , Rakhlina M.
Published: February 2011

Products of the chlorination of α- and m-polymers of chloroprene were obtained. The chlorine content of the chlorinated polychloroprene depended on the conditions of chlorination, but corresponded to products formed by the addition of chlorine. A large excess and high concentration of chlorine resulted in the addition of chlorine to the double bonds, together with partial substitution of hydrogen by chlorine. Of the three basic types of chloroprene polymers, the α-polymer added chlorine most easily; m-polymer was chlorinated with more difficulty, giving a chlorination product of the composition, corresponding by analysis to the addition of chlorine at the double bond. All polymers of chloroprene chlorinated under these conditions contained saponifiable chlorine. Films of chlorinated polymers of chloroprene are characterized by a considerable stability to the action of various acids (nitric and sulfuric acids and aqua regia) in the cold and at moderately high temperatures. γ-Polymer of chloroprene is not chlorinated under the same conditions.