bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preliminary Studies of the Conductivity of Latex
Authors: van Gils G. E. 
Published: February 2011

Abstract
Most of the measurements were made with the philoscope, which is a new instrument made by Philips Gloeilampenfabriek. With this instrument the conductivity of latex can be measured easily and with sufficient accuracy. Obviously conductivity measurements are highly important for latex research. It is shown in Tables 1 and 2 that the conductivity of latex continually increases on standing. If enough ammonia has been added, this increase becomes smaller after two days ; if not, it continues unabated, and in time the latex coagulates. The dry rubber content has a great influence on conductivity, which may be explained by assuming that the serum is the only electrically conducting medium. However, the conductivity decrease is somewhat greater than can be explained on this assumption alone. Ammonia has a great influence on conductivity in dialyzed latex (Figure 4). But since the conductivity of ammoniated latex is less than the sum of the individual (latex and aqueous ammonia) conductivities, a great deal of ammonia must be adsorbed on the latex particles. When ammonia is added to fresh latex or to serum prepared by freezing latex, the conductivity curve shows a remarkable bend, caused by precipitation of magnesium ammonium phosphate (Curve III, Figure 3; Figure 4). Conductivity measurements in dialyzed latex after adding salts show that the salts are partially adsorbed by the rubber globules. Divalent calcium ion especially is strongly adsorbed. It was found that acid coagulation of latex yields rubber with a much lower ash content than when latex is coagulated without acid, as by heat or by alcohol. This may be explained by the fact that, in acid medium, the charge on the latex particles is small and, consequently, adsorption of electrolytes is also small.
The Use of Synthetic Rubber in the Automotive Industry from the Viewpoint of the Rubber Technologist
Authors: Street J. N. , Ebert H. L. 
Published: February 2011

Abstract
The primary interest of the automotive and of the rubber industry in so-called synthetic rubbers is to obtain products which will stand up under service conditions in which present rubber compounds either do not perform satisfactorily over their entire expected life, or are approaching their limit; or because of these factors, are limiting automotive engineering development. In addition, the last few months have seen a trend of thinking toward a nationalistic program of at least partial self-sufficiency, in case of emergency, or a possibility of the limitation of the poundages of crude rubber available to us at an economic price. The subject “The Use of Synthetic Rubber in the Automotive Industry” is consequently being considered in the light of both viewpoints. Activity in the field of synthetic rubbers as far as laboratories in this country are concerned has increased considerably over the last three years, and it is quite likely that the data and viewpoints herein presented on present polymers may very well be obsolete within a matter of months, and certainly within a year or two, with the appearance of new polymers and modifications of present ones. The object of this paper is consequently to summarize the present state of affairs regarding materials now available. The literature on synthetic rubbers is abundant as to the preparation of the various kinds and varieties, their compounding, and the characteristics of fabricated products. A very excellent and interesting summary is that by Wood. From a general viewpoint, the article entitled “Synthetic Rubber” in the August issue of Fortune is very much to the point. The characteristics of Neoprene are well known. Those of the butadiene types have been described in several articles by Stöcklin and by Koch. Similarly other products have been described. Anderson and Garner and Westhead have given some comparative data on Neoprene and Buna types. In view of these articles, the present paper appears superfluous. It has been pointed out by Wood, however, that it would be desirable to have additional confirming data on a comparable basis on the materials now available. It has been with the hope of supplying such data, at least in part, and particularly as applied to usage of synthetic rubbers in the automotive field, that the authors continued with the preparation of this paper.
Cotton Fibers. Constitution, Structure, and Mechanical Properties
Authors: Nickerson R. F. 
Published: February 2011

Abstract
The study by chemical methods of the constitution, derivatives, and properties of cellulose has yielded a voluminous literature and a wealth of useful information. Microscopic and x-ray investigations have produced much new and valuable knowledge of cellulose and its structure. But relatively little attention is given to the mechanical properties of cellulosic fibers, although such properties reflect fiber structure and frequently determine suitability to specific applications. An exhaustive review of the relevant literature on cotton has not been undertaken in this paper; rather, the object is to summarize the available data on constitution and properties and, wherever possible, to indicate their relations to the most probable fiber structure. In this way the material as a whole is integrated into a working concept of the cotton fiber.
Hysteresis in Crystallization of Stretched Vulcanized Rubber from X-Ray Data. Correlation with Stress-Strain Behavior and Resilience
Authors: Clark George L. , Kabler Marian , Blaker Ernest , Ball John M. 
Published: February 2011

Abstract
1. For sample H, with high modulus and high resilience, there is a greater crystallizing tendency above 350 per cent for the first cycle and above 400 per cent after previous flexing. 2. Both H and L have narrow loops, which indicate an approach to reversibility in the formation and deformation of crystalline regions above 400 per cent for the first and later cycles. 3. The crystallization of H is greatly enhanced above 400 per cent after the first cycle of stretching and retraction; L remains essentially unchanged by previous history over this range; this is analogous to the much greater change in the stress-strain loop from the first to third cycles for H, as compared with L. 4. At elongations below 400 per cent for the first cycle and 350 per cent for subsequent cycles, L has a far greater hysteresis or tendency to retain the crystalline arrangement, and this greatly increases after the first cycle, so that the fiber interferences persist on retraction to elongations 150 per cent below the elongation required for institution of organization on extension of the sample. Sample H is considerably more consistent in its behavior over the lower elongations, and between the first and later cycles. In other words, the tendency of H to return to the normal state on release of a deforming force is clearly evident, whereas L shows a marked tendency to retain a structure once set up. If resilience is the property of an elastic body related to the percentage of the potential energy introduced by applied stresses which is returned as work when the body returns to its original shape and size upon release of the stresses, then these x-ray data would seem to be consistent with the higher resilience of H; for ordinary measurements of resilience are evidently related to the lower ranges of deformation over which H returns to its normal state (disorder of macromolecules as in a liquid) so much more easily than L.
X-Ray Structure of Rubber-Carbon Black Mixtures
Authors: Gehman S. D. , Field J. E. 
Published: February 2011

Abstract
The position of carbon black as an indispensable compounding ingredient for present-day rubber technology has led to many experimental and theoretical inquiries regarding the manner in which it functions to improve the properties of rubber into which it is incorporated. The general term “reinforcement” is used to express improvements in physical properties brought about by the mixing of powders into rubber. Shepard, Street, and Park reviewed the concepts which have been employed in efforts to define reinforcement. Reinforcing effects are made evident in measurements of plasticity, viscosity of solutions, stress-strain relations, tear, and abrasion resistance. By all criteria which have been proposed, channel black heads the list of reinforcing powders, although there is some indication that even more pronounced reinforcing effects can be obtained with finer carbon blacks. Available explanations of reinforcement constitute an involved maze of contradictory evidence, speculations, and controversies in strong contrast to the practical importance of having a clear understanding of what occurs. The literature on the subject has been ably reviewed by Shepard, Street, and Park. Characteristics of a powder which have been held responsible for reinforcement are:
Analysis of Proteins Occurring in Hevea Latex. II. Properties and Identification of the Isolated Products
Authors: Altman R. F. A. 
Published: February 2011

Abstract
In a previous paper the separation and analysis of proteins remaining in rubber serum, after coagulating the rubber with formic acid, were described. The present paper is concerned with the properties and identification of the products thus isolated. As for nonamino acids, it may be recalled that these are composed mainly of the unsaponifiable thick brownish red oil A4. Of the other byproducts remaining to be identified, which were designated as BII, BIII, BV and BVI, only small amounts were obtained. Of the amino acids, alanine, arginine, asparagic acid, glutamic acid, histidine, leucine, ornithine, hydroxyproline, proline, tyrosine and valine were isolated in weighable amounts. In addition to these, it was possible to identify dihydroxyphenylalanine. In this connection the results obtained by Midgley, Henne and Renoll are of interest. These investigators found, as the principal components of proteins occurring in crepe rubber, the following amino acids: arginine, asparagic acid, glycine, histidine, leucine, lysine and proline. They considered it highly probable that alanine, phenylalanine, hydroxyproline and serine were also present in these proteins. On the other hand, it was definitely established that cystine, glutamic acid and tyrosine were not present. Table I summarizes the results of Midgley and his coworkers in comparison with ours. From this table it is evident that certain proteins, viz., those containing, among other compounds, tyrosine, glutamic acid and valine, do not coagulate with the rubber, but remain in the serum. The absence of sulfur-containing amino acids can probably be attributed to certain shortcomings in the analytical method. At any rate, the presence of sulfur in proteins precipitated from latex was established when the test was repeated.
Crystallization of Vulcanized Rubber
Authors: Bekkedahl Norman , Wood Lawrence A. 
Published: February 2011

Abstract
The formation of crystals at room temperature by stretching rubber, vulcanized or unvulcanized, has been the subject of considerable study. The crystallization of unstretched rubber at low temperatures is also well known, but with a single exception to be discussed later, the effect has commonly been considered to be limited to the unvulcanized material. In the present investigation, however, the crystallization of unstretched specimens of vulcanized rubber of low sulfur content has been accomplished. In commercial vulcanized rubber products, crystallization has not hitherto been recognized as a factor of practical importance. It is probably significant in cold climates, where some rubber products slowly undergo a great increase in rigidity and permanent set. Automobile traffic counters, for example, have been rendered inoperative by the hardening of the rubber tubing used with them. Laboratory tubing and other products made of a number of different commercial rubber compounds have become rigid after storage for some weeks in a refrigerator at about 0° C. Previous work on unvulcanized rubber showed that it can be crystallized at temperatures between + 10° and −40° C, the crystals melting in a range from about 6° to 16° C. Crystallization and fusion are accompanied by changes in volume, heat capacity, light absorption, birefringence, x-ray diffraction, and mechanical properties such as hardness. x-Ray diffraction and birefringence, of course, give the most direct evidence of crystalline structure, but in the present work change of volume, measured in a mercury-filled dilatometer, was chosen as the criterion of crystallization or fusion. Quantitative results are more easily obtained in this manner, and the experimental observations are simple. Furthermore, the method is well adapted to continuous observations over long periods of time, such as were found necessary in the present work.
Effect of Various Sulfur-Accelerator Ratios in Vulcanized Rubber
Authors: Conover F. S. 
Published: February 2011

Abstract
The use of very low sulfur-high accelerator combinations in certain types of rubber products has been highly successful in many cases in which extraordinary resistance to heat aging has been necessary. The tendency toward the use of compounds of this type has increased during the past few years, sometimes apparently with little or no attention to the service characteristics of the final product other than the aging properties already mentioned. The behavior of low-sulfur stocks in respects other than aging has been the subject of some work, notably an investigation by Somerville and Russell. This paper, however, left a number of questions unanswered, and was limited to a discussion of two sulfur-accelerator variations. The work reported in the present article has been designed to broaden the scope of the former investigators, both in compounding variations and in types of test. The program is intended as an aid in answering two specific questions: (1) What advantages, other than aging, are obtained by the use of low sulfur-high accelerator ratios? (2) What disadvantages in test or service are to be expected from low sulfur-high accelerator ratios?
Distillation Products from Waste Rubber
Authors: Pickett F. N. 
Published: February 2011

Abstract
About 1930, during some experiments on new systems of reclaiming waste rubber, it was discovered that certain fractions of the products resulting from the destructive distillation of old tires possessed solvent and softening properties hitherto unsuspected. A complete system of reclaiming based on this discovery was worked out, and many tons of reclaimed rubber were manufactured by utilizing such distillation products. Investigation of the products of distillation was carried out with interesting results. Retort distillation was the method adopted as being the most economical, and experiments were carried out with the aid of the chemists of the Gas, Light & Coke Co., Ltd., at Fulham Research Station. A pilot plant was erected which consisted of seven retorts of the ordinary gas-works type. It had previously been found that a temperature variation of only a few-degrees had considerable effect not only on the percentage yield but also on the components of the distillate. For maximum yield, the most suitable distillation temperature was about 560° C.
Pliolite-Rubber Mixtures
Authors: Thies H. R. 
Published: February 2011

Abstract
Cyclized rubbers have attracted the attention of chemists for a long time. When pure, all of these derivatives of rubber consist of a hydrocarbon or a mixture of hydrocarbons (C5H8)x, and all have less unsaturation than does the parent substance. Their physical properties, however, vary from rubbery to hard shellaclike types, and their formation is attributed to internal cyclic formation, since there is a change in the unsaturation but no change in the composition when compared to the original rubber. Several different methods have been utilized for the preparation of a cyclized rubber. Harries obtained a white inelastic solid by treating a rubber hydrogen halide with an organic base. When rubber is heated under conditions which preclude complete breakdown, a diminution in the number of double bonds is effected, together with increase in density. Cyclization by pyrogenic decomposition was accomplished as early as 1838 by Himly The heat-cyclized rubber obtained by Staudinger and Geiger was a white powder, the solutions of which were of low viscosity. The effect of heat on rubber in solution as investigated by Staudinger and Bondy showed that, up to 150° C, the number of double bonds remained the same, but at higher temperatures cyclization occurred. As early as 1781 Leonhardi referred to a tough elastic product obtained by treating rubber with sulfuric acid. In 1851 Macintosh obtained a patent for a process in which the extruded or moulded articles of gutta-percha were subjected to superficial hardening by immersion in concentrated sulfuric acid. However, the sulfuric- or sulfonic-acid-cyclized rubber of today is based upon the investigations of Fisher and coworkers. These materials, known as Thermoprenes, were shown to be cyclic isomers of rubber hydrocarbon, in agreement with the observations of Kirchhof and Staudinger. Rubber isomers from halides of amphoteric metals, such as stannic and stannous chlorides, aluminum chloride, boron fluoride, and chlorostannic acid, embrace some of the most valuable chemical derivatives of rubber. A comprehensive study of these reactions was made by Bruson, Sebrell, and Calvert. The properties of amphoteric metal halide derivatives of rubber which render them specially valuable as moulding materials were described by Thies and Clifford and by Jones and Winkelmann. Numerous other methods for isomerizing rubber include the silent electric discharge, heating in the presence of surface-active substances, phosphorus oxychloride, and hydrogen fluoride.
Rubber in Compression
Authors: Kimmich E. G. 
Published: February 2011

Abstract
The effects of shape and surface conditions of rubber used in compression have remained somewhat of a mystery because of the apparently conflicting results often obtained. It is to be hoped that the work herein described will: (1) explain some of the difficulties encountered; (2) establish a simple and reasonably accurate procedure for predetermining the compression stress-strain performance of many of the commonly used shapes, and (3) encourage an extension of this work to include more complicated shapes, and to provide further refinement of the results. Compression uses of rubber doubtless far exceed in number the shear and tension uses for industrial applications, and warrant much work in determining the relationships involved, at least to the extent of establishing empirical rules of sufficient scope and accuracy for practical use. The erratic nature of compression-test results has made it difficult to correlate data reported in the technical articles on this subject. It is herein indicated that much of this difficulty may be explained by the condition of the surfaces, the manner of applying the load, discrepancies in hardness measurements, variations in the actual stiffness of the rubber used, and the fact that the stress-strain graph is not a straight line.
Hysteresis Tests on Tire Compounds
Authors: Mackay J. G. , Anderson J. G. , Gardner E. R. 
Published: February 2011

Abstract
(1) The reasons for the selection of the Goodrich flexometer for hysteresis measurements are given. (2) The machine is capable of producing results within ± 1 per cent. (3) For a given cure, the temperature rise of a stock may be increased by increasing the length of stroke, the applied load or the frequency of flexing. (4) For a given set of flexing conditions, there is an optimum cure at which the lowest temperature rise is obtained. Cures shorter and longer than this optimum give increased temperature rise. (5) The differences due to cure may be cut down by reducing the stroke or load, the former having the greater effect. The role of the frequency in this respect is not simple. Reduction of the frequency from 1450 to 830 cycles increases the relative differences due to cure, but a further reduction to 685 has the reverse effect. (6) A set of conditions suitable for testing tread stocks is as follows: load, 150 lbs. per sq. in.; stroke, 0.3 in.; frequency of flexing, 1450 cycles per min. (7) Three examples are given which show that results obtained on the flexometer can be correlated with those obtained on actual tires on the road and on an inside test wheel. (8) Overmilling of a tread stock increases its tendency to heat. (9) Heat-treatment of carbon black-rubber master batches before compounding in tread stocks reduces the tendency of the latter to heat. (10) Tread stocks with low sulfur and high accelerator content give less temperature rise on the flexometer than those with normal sulfur and accelerator. (11) So-called high-resilience accelerators give lower temperature rises than mercaptobenzothiazole in gum stocks, but are no better than mercaptobenzothiazole in tread stocks. (12) Antiflex-cracking antioxidants do not cause a reduction in the tendency to heat compared with normal antioxidants.
The Creep of Natural and Snythetic Rubber Compounds in Shear
Authors: Hahn Stuart H. , Gazdik Ivan 
Published: February 2011

Abstract
Creep tests, extending in some cases as long as 900 days, indicate that both natural and synthetic rubbers such as Neoprene and butadiene copolymer can be compounded to give satisfactory service in shear mountings. At 140° F, creep is from two to nine times greater than at 80° F, depending on the compound. Tests at room temperature do not indicate either the amount of creep or the life to be expected at higher temperatures. Actual creep (measured in inches) increases with stress, but when expressed at percentage of initial deflection, it may be independent of stress. Creep curves are linear over a considerable range of time when plotted on log-log scales. However, extrapolation of such curves to predict results after very long times is not justified, because the curves may not continue to be linear, or failure of the mountings may occur, particularly at high temperatures. Short time tests of any sort are not necessarily indicative of the relative creep or life of compounds in long-time service. The tests reported here are a small portion of a large number which is being continued and augmented. It is hoped that these and other investigations now under way may contribute to clearing the picture of the complex interrelations between the many physical properties of compounds of rubberlike materials. The rubber technologist uses his specialized knowledge to develop a wide variety of compounds, making use of several types of basic rubberlike materials. He chooses whichever fits service requirements best from performance and economic viewpoints. Modern materials and recent developments in processing technique have made possible compounds suitable for a wide range of service conditions.
Permeability of Elastic Polymers to Hydrogen
Authors: Sager Theron P. 
Published: February 2011

Abstract
The permeabilities to hydrogen of natural rubber, Perbunan, Neoprene G, Vistanex, Thiokol DX, and Pliofilm diminished in the order mentioned. The increase in rate of permeation with increasing temperature was exponential in all cases. Values for the activation energies or permeability for hydrogen were found to be 6,800 calories per mole for natural rubber and 8,400 to 9,500 calories per mole for the synthetic materials. The greater magnitude of the energy requirements of the latter indicates that their lower permeability may be attributed to differences in their molecular structure.