bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Weight and Chain-Length of Natural and Synthetic Rubber
Authors: Wildschut A. J. 
Published: February 2011

Abstract
The determination of the chain-length of high molecular substances, as, e.g., rubber and gutta-percha, has lately been the subject of many investigations, though as yet the problem has not been definitely solved. The ordinary methods—measurements of the raising of the boiling point and of the depression of the freezing point—can be used only for molecular weights of some thousands, and there always remains a large gap between these compounds and the far greater natural ones. To bridge over this gap Staudinger has developed a supposition according to which it is possible to determine very high molecular weights by means of a viscosimetric method. This method depends on the known fact that for dilute solutions, in which the molecules do not hinder each other (so-called sol-solutions), the specific viscosity is proportional to the length of the molecule. For homologs we have:
Synthetic Rubber
Authors: Whitby G. S. , Katz M. 
Published: February 2011

Abstract
In the early period isoprene was recognized as the mother substance of caoutchouc, and its ability to undergo polymerization to a rubber-like product was demonstrated. During the pre-war period serious efforts were begun to devise processes for the synthesis of rubber which would be commercially feasible. Attention was concentrated on the preparation of the necessary monomeric dienes from cheap raw materials available in substantially unlimited quantity. The rubber-like polymers prepared were markedly inferior to natural rubber. During the war the actual manufacture of synthetic rubber from dimethylbutadiene and its utilization in the production of certain lines of rubber goods was, owing to the exigencies of the time, undertaken in Germany. After a lull, synthetic rubber in 1925 again became an active subject for research. In so far as butadiene and its homologs are concerned, attention during this post-war period has been concentrated on methods of polymerizing the dienes rather than on methods of preparing them, and marked progress has been made. Recently a novel form of synthetic rubber has been prepared by polymerizing 2-chlorobutadiene. Chloroprene rubber resembles vulcanized natural rubber in elastic properties more closely than any previous synthetic rubber preparation and, moreover, has advantages over natural rubber in certain respects. Experiments on the swelling of chloroprene rubber and its tensile properties are reported.
The Vulcanization of Rubber
Authors: Behre J. 
Published: February 2011

Abstract
In the present work the problem of vulcanization has been studied from the physico-chemical point of view. It is proved in this way that the rate of vulcanization depends not only upon the nerve of the rubber, but also upon its content of natural accelerators and of fatty acids. The influence of the month of harvesting on the results is shown, and finally a new theory on time action of accelerators is developed, which is based on studies of diphenylguanidine, mercaptobenzothiazole, and hexamethylenetetramine. If this theory is essentially correct, the problem of vulcanization can be approached from an entirely new point of view and with colloid-chemical means. This in turn certainly offers great possibilities in the development of new accelerators.
The Plastic Properties of Several Types of Unvulcanized Rubber Stocks at High Rates of Shear
Authors: Dillon J. H. , Johnston N. 
Published: February 2011

Abstract
Marzetti, Griffiths, and others have employed the extrusion method for studying the plastic properties of unvulcanized rubber. Some of the results, particularly those of Marzetti, have been very interesting from an academic standpoint. However, none of these experimenters has employed rates of shear differing greatly from those of the compression-type plastometers, which operate at rates much lower than those existing in factory tubing machines. It seemed, then, that this fact might explain why no great discrepancies between extrusion plasticity results and those of the parallel-plate compression-type plastometer were found, at least in so far as could be discovered in the literature. Hence, it was thought desirable, from both an academic and a practical standpoint, to make a study of the flow of rubber through an orifice over a wide range of rates of shear.
The Physical Structure of Elastic Colloids
Authors: Busse W. F. 
Published: February 2011

Abstract
1. Some of the concepts included in the term “molecule” are briefly discussed and it is pointed out that the mechanical molecule is often the most important one in colloid systems. 2. The elastic properties of colloid systems require, and are produced by a group of four factors: (a) Long fibrous molecules. (b) Weak or uniform cohesive forces around the fibers. (c) An interlocking of the fibers. (d) A means of storing up free energy when the fibers are distorted. 3. Evidence for the existence of these factors in elastic colloids is discussed and is applied to account for and correlate some of their physical properties. 4. The theory of the structure of elastic colloids presented here has suggested means of preparing fibrous and parchment-like rubbers having rather unusual properties.
The Resistance of Anisotropic Rubber Sheets to Cutting and to Tearing
Authors: Kirchhof F. 
Published: February 2011

Abstract
The interesting experiments of Talalay on the resistance of rubber mixtures to cutting suggested to the present author that it might be fitting to describe certain observations of his own, made at the same time, on the behavior of rubber mixtures prepared from latex. Since in the preparation of such mixtures all mastication of the rubber is avoided, the relations are simpler than in the case of masticated rubber mixtures, and a better insight into the nature of the physical properties of the former is certain to be obtained. In addition to these experiments, the measurement of the resistance to tearing of calendered, vulcanized rubber sheets is discussed.
The Action of Hypochlorous Acid on Rubber
Authors: Bloomfield G. F. , Farmer E. H. 
Published: February 2011

Abstract
It has been previously observed that when rubber latex is treated with cold aqueous hypochlorous acid, the simple additive attachment of the hypochlorous acid molecule at the ethylenic center of each C5H8 unit of the rubber molecule may be accompanied by a considerable amount of substitutional chlorination (cf. preceding article). An analogous behavior has now been found to characterize the interaction of dissolved rubber (rubber solutions) with hypochlorous acid, but in this case marked differences in the properties of the reaction products become manifest. In the treatment of dissolved rubber some evidence of substitutional chlorination is directly apparent, even where the amount of hypochlorous acid does not exceed one molecular proportion per C5H8 unit, and considerable replacement of hydrogen by chlorine occurs when the reagent is present in excess of this amount; indeed, by using a suitable excess of the latter, it is possible to obtain chlorinated materials with a maximum chlorine content of 66 per cent. Now it is of practical importance to note that, whereas the chlorinated materials obtained from latex are characterized by a high degree of insolubility, the analogous materials from dissolved rubber are relatively soluble, and in the case of some of the more highly chlorinated materials are readily soluble in the ordinary solvents for rubber.
Effect of Oils and Chemicals on DuPrene Compounds
Authors: Hayden O. M. , Krismann E. H. 
Published: February 2011

Abstract
Since the days of Charles Goodyear there has been among rubber chemists a growing appreciation of the fact that almost every condition of service to which rubber may be subjected requires a different type of compound, if the best possible results are to be obtained. The most valuable lesson to be learned from the investigations reported here is that this is true of DuPrene to an even greater extent than of rubber. It would be easy for one, who had happened to immerse in sulfuric acid a DuPrene compound containing clay, to draw the conclusion that sulfuric acid causes DuPrene to swell and lose all of its strength and rubber-like characteristics; but, when we have all the facts before us, we see that it is the clay, not the DuPrene, that causes the trouble. Likewise, that very common and generally inoffensive rubber-compounding ingredient, barytes, is one of the worst materials that can be used in a DuPrene stock which is subjected in service to acetic acid, but the mere substitution of clay for the barytes produces a stock that is many times more resistant. The art of DuPrene compounding is still young. In the short time that has elapsed since the invention of DuPrene it has been discovered that DuPrene can be compounded so as to make it more resistant than rubber to practically all chemicals. There is every reason to believe that further experience will teach how to impart even greater oil, solvent, and chemical resistance to this unique synthetic rubber.
Delayed-Action Accelerators
Authors: Naunton W. J. S. , Baird W. , Bunbury H. M. 
Published: February 2011

Abstract
There is little doubt that the discovery of organic accelerators of vulcanization was made more or lees simultaneously in two parts of the world and as the result of two entirely different investigations, neither of which had as its target the discovery of accelerators. In the United States it is recorded by Oenslager, who was awarded the Perkin Medal in 1932 for this work, that he was looking for a compounding ingredient which would impart to rubber goods made from the cheaper grades of rubber the superior wearing qualities then obtained only from fine Para. To his astonishment these organic substances not only improved low-grade rubbers, but brought about a considerable improvement in the goods made from the best grades of rubber, and further made possible a considerable reduction in the time of cure. In Germany chemists were searching for the active principle which rendered rubber comparatively stable to oxidation. Synthetic rubber and natural rubber from which the nitrogenous substances had been extracted were unstable. From these facts it was a simple step to try organic bases as stabilizers of both synthetic and raw rubber, and it was then found that they not only protected the rubber against oxidation, but also accelerated the vulcanization of the rubber to which they had been added.
Research on Modified Rubbers. Part III. Adhesive Latex
Authors: Bloomfield G. F. , Farmer E. H. 
Published: February 2011

Abstract
In the course of an investigation on the oxidation products of dry rubber and of latex, the reaction of latex with hydrogen peroxide was studied. One result of this work was that a latex possessing distinctive adhesive or sticky qualities was prepared, and it is believed that the so modified latex may prove to be of commercial interest. It is proposed, for the sake of brevity, to refer to this product as “sticky” latex. By allowing hydrogen peroxide to react with latex, a series of more or less oxidized preparations was obtained, on which a more detailed report may be issued later. We may, however, refer to a series of plasticity tests made by M. W. Philpott, as a result of which the following figures, which apply to the dry rubber derived from the latex, were obtained:
The Heat of Swelling of Rubber and Its Relation to the Previous History of the Rubber and to the Nature of the Swelling Agent
Authors: Hock Lothar , Schmidt Hans 
Published: February 2011

Abstract
The swelling method developed by Hock and Bostroem for determining calorimetrically changes in the state of energy of raw rubber (the Joule heat effect on stretching, the fiber structure of Hock, and the filler effect of Wiegand) has been developed further, especially by Hock and Hartner, with the object of obtaining information about the boundary surface energy between rubber and these fillers by means of the heat of swelling first of all of unvulcanized rubber mixtures containing active fillers such as carbon black and zinc oxide. The “activity” of fillers of this kind evidently depends upon the effect of boundary surface forces, which increase the mechanical work of rupture of rubber, A=∫p.dl, after their admixture in the rubber. To ascertain to what extent and in what quantitative way this mechanical “reënforcement” of rubber is related to the boundary surface energy, where there is mutual wetting, is a problem which is attractive both from a theoretical and technological point of view, and to the solution of which the works mentioned offer the first contributions. In continuing the experiments along the same general direction, on the one hand from the point of view of a critical examination of methods and on the other hand with the object of increasing the precision of the measurements, it was soon realized that it would be necessary to carry out special preliminary experiments. In fact, when it was once decided to replace benzine, which had been particularly suitable in experiments on the swelling of rubber mixtures because of certain unique properties, by benzene and other liquids, it became necessary to determine the heat of rubber as an objective in itself, whereas in the earlier experiments this had been only a means to an end.
X-Ray Diffraction Studies of the Bureau of Standards Rubber Fractions
Authors: Clark George L. , Warren W. J. , Smith W. H. 
Published: February 2011

Abstract
At the request of Dr. Washburn, a careful preliminary x-ray diffraction study has been completed on various samples of rubber fractions prepared at the Bureau of Standards by the methods already described. The results are so interesting, especially in structural differentiation between the ether-soluble (sol-rubber) and the ether-insoluble (gel-rubber) hydrocarbons, and in producing new data bearing upon the several theories of the structure of whole rubber, that it has seemed desirable to record very briefly some of the more important observations. It will be recalled that native rubber, raw, purified, or vulcanized, gives a typical liquid halo or “amorphous” type of diffraction pattern in the unstretched condition, which changes to the characteristic crystal fiber pattern when the rubber specimen is stretched. Upon the basis of these facts, several theories of the structure of the rubber hydrocarbon have been proposed: the folded or spiral molecules model; the fringe model (bundles of molecular chains with frayed ends); the flexible chain model; and the very familiar two-phase model.
Natural and Synthetic Rubber. XIII. The Molecular Weight of Sol Rubber
Authors: Midgley Thomas , Henne Albert L. , Shepard Alvin F. , Renoll Mary W. 
Published: February 2011

Abstract
Partially vulcanized rubber has been fractionated into components in which rubber is combined with increasing amounts of sulfur. The analyses of these fractions concur to indicate a molecular weight of about 54,000 for the particular sample of rubber used. Specimens of varied origin can thus have their molecular weight measured by strictly orthodox chemical means.
The Chemistry of Soft Rubber Vulcanization. III. Comparison of Vulcanized Rubber with Unmilled Crude Rubber Reclaims, and Unvulcanized Stocks Containing Stiffeners or Gas Black
Authors: Garvey B. S. 
Published: February 2011

Abstract
IN PART I (1) of this series it was pointed out that the measurement of vulcanization is complicated by the use of unmilled rubber (e. g., latex stocks), stiffeners, gas black, and reclaims. Therefore limitations in compounding were accepted and a standard method of processing was adopted. These limitations were accepted in recognition of the fact that compounds containing these materials show some properties akin to those of vulcanized rubber. For example, some crude rubbers have stress-strain characteristics almost identical with those of certain types of vulcanizate. Uncured gas black stocks likewise show some of the characteristics of vulcanized rubber, and the reënforcing action of gas black is sometimes spoken of as a sort of vulcanization (2). Such limitations are desirable only if it can be shown that the phenomena excluded are different from those being studied. The experiments reported in this paper show how the tough, hard, crude rubbers can be differentiated from vulcanized rubber and how the effect of gas black and stiffeners can be differentiated from that of vulcanization. The generally accepted view that reclaims are distinct in character from either vulcanized or unvulcanized rubber is supported by this investigation. The. experiments also show why it is desirable, for the present, to exclude these materials from the compounds used to study vulcanization.
An Apparatus for the Extraction of Samples of Rubber and Other Materials with Solvents
Authors: Stern H. J. , Pufett W. 
Published: February 2011

Abstract
The following is a brief description of a simple, cheap and efficient apparatus for the extraction of small samples of rubber and other materials with solvents, as is required in analytical work. It may also be used for any reactions which involve refluxing. The apparatus is shown in diagram in Figs. 1, 2 and 3. The base is made from a piece of a suitable quality of heat-resisting ebonite such as Silvernite. On the base is mounted a series of carbon filament lamps, six being a convenient number for one unit. Each lamp has its own switch. Around the lamp is a cylinder of sheet iron or zinc, perforated as shown. These cylinders serve to support the flasks, which are in effect heated by warm air from the lamp. In the diagram the cylinders are shown with a plain top, but it is sometimes of advantage to have this serrated, so as to avoid any tendency for extracts to become “baked” above the level of the solvent.
Influence of Vulcanization on the Index of Refraction of Rubber
Authors: Kirchhof F. 
Published: February 2011

Abstract
Only recently McPherson has measured various physical properties of highly purified raw rubber, among them its index of refraction. In this work McPherson obtained essentially the same values as did the present writer. In the work of the latter it was pointed out that the sulfur of vulcanization has an influence on the index of refraction, because the high index of refraction of sulfur has a noticeable effect even at low degrees of vulcanization. As a result of other investigations, the present author has not until the present time carried on any further the work planned at that time. It was therefore a pleasure to find that McPherson had carried out these investigations with rubber purified by the process developed in his earlier experiments. In the present work, the determinations of the index of refraction were made at 25° with an Abbé refractometer, and the method of total reflection was used. The rubber used for preparing the samples was free of protein and so-called rubber resins, and contained 99.5 per cent of pure rubber hydrocarbon. The samples were vulcanized to a stage where practically all of the sulfur added had combined with the rubber.
Characteristic Properties of Rubber at Low Temperatures. A Discussion of the Stress-Strain Curves of Vulcanized Rubber at Low Temperatures
Authors: Fujiwara Takeo , Tanaka Toramatsu 
Published: February 2011

Abstract
The hardening of rubber at low temperatures is one of the well-known physical characteristics of rubber. The loss of elasticity of raw rubber by hardening at 0° to 10° C., its turning to the consistency of glass, and its fragility at −19° C. when cooled with liquid air, and its fibering when stretched to 60–70 per cent previous to breaking, give an experimental proof of the theory of the structure of rubber molecules. Vulcanization makes raw rubber physically less sensitive to heat and to low temperatures, and is of great significance, because it enables vulcanized rubber to be used around −30° C. without losing its elasticity. The effect of external heat on the physical properties, especially on the stress-strain relations, of vulcanized rubber has been discussed mainly for temperatures from −10° to +100° C., and only two papers deal with temperatures from −30° to −60° or −70° C. (cf. Le Blanc and Kröger, Kolloid Z., 37, 205 (1925); Tener, Kingsbury and Holt, Bureau of Standards Technologic Papers Vol. 22, No. 364). Of special importance are a means of recognizing changes m the physical properties (phenomenon of freezing-hard ness) of vulcanized rubber at −30° to −60° or −70° C., and the practical value of such information. Though there is a contradiction in the fundamental meaning of the “cold resistant theory” of rubber, investigations of the two phases of the subject may throw some light on practical problems and widen the scientific point of view.
The Action of Copper Salts on Raw Rubber
Authors: Buizov B. V. , Molodenskii V. S. , Mikhailov N. I. 
Published: February 2011

Abstract
1. An examination of the literature makes open to doubt the view of many investigators that copper salts exert a destructive action on rubber by functioning as catalysts which start the autoöxidation of rubber and then promote this autooxidation. The literature available indicates with just as good reason that there is another explanation of the effect of copper salts, viz., that the destructive action of these salts is characterized in its initial stage by a disaggregation of the. rubber. As a result of this disaggregation there is an increased surface of rubber micelles with an accumulation of double bonds. The rubber is then more readily susceptible to oxidation by atmospheric oxygen. 2. The detailed study in the present work of the action of copper salts on rubber solutions has shown that the complicated process as a whole can be divided into separate partial processes, i. e., into a desolvation, a micellar disaggregation, and a molecular disaggregation. 3. Observations of changes in weight and of the properties of rubber films proved conclusively that copper salts first bring about a desolvation of the rubber micelles and then a disaggregation. The latter proceeds without any accompanying oxidation of the rubber. Following this there is an oxidation of the irreversibly degenerated rubber. 4. The influence of oxygen on the appearance of stickiness is very slight, in fact tackiness appears both in the presence and the absence of oxygen. 5. The stickiness of rubber samples to which a copper salt has been added is always to be found in the interior of the samples, while a brittleness appears on the surfaces. 6. These facts lead to the conclusion that the stickiness of raw rubber appears as a result of disaggregation, whereas brittleness is the result of oxidation. 7. The destructive effect of copper salts depends to a large extent upon the state of dispersion of the copper salt in the rubber; the more finely dispersed is the salt in the rubber, the greater is its effect. 8. Copper salts accelerate vulcanization, without however increasing the proportion of combined sulfur. Upon standing a long time, rubber containing a copper salt loses completely its power of vulcanization. This latter phenomenon can be explained by the fact that copper compounds bring about in a relatively short time the disaggregation which is necessary to vulcanization, whereas after a longer time they destroy the rubber completely.
Studies on the Combined Use of Some Different Organic Accelerators. IV. Diphenylguanidine and Dibenzothiazole Disulfide
Authors: Aoe Itiro , Yokosima Hirosi 
Published: February 2011

Abstract
1. Diphenylguanidine and dibenzothiazole disulfide do not form a molecular compound or eutectic mixture, as judged by their melting and softening point curve. 2. The effects of scorching were studied by the use of various proportions of diphenylguanidine and dibenzothiazole disulfide; the maximum scorching was found with the mixture which had the lowest melting point in the curve. 3. These proportions were also studied for their vulcanizing power. 4. Diphenylguanidine and dibenzothiazole disulfide form a molecular compound through the medium of hydrogen sulfide. 5. This molecular compound was prepared and tested for its vulcanizing properties.