bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthetic Rubber
Authors: Whitby G. S. , Katz M.
Published: February 2011

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

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

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

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

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

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

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

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.
The Causes of Discoloration in Preserved Latex
Authors: Rhodes Edgar , Sekar K. C.
Published: February 2011

Discoloration in preserved latex is attributed to contamination with iron and to the presence of hydrogen sulfide or soluble iron-reactant sulfides.
Research on Modified Rubbers. Part III. Adhesive Latex
Authors: Bloomfield G. F. , Farmer E. H.
Published: February 2011

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

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

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

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

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

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

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

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

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

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.
The Chemistry of Soft Rubber Vulcanization. IV Vulcanizing Agents Other than Sulfur
Authors: Garvey B. S.
Published: February 2011

The vulcanizing action of sulfur chloride, m-dinitrobenzene, selenium, tetramethylthiuram disulfide, and benzoyl peroxide has been investigated by the use of a set of tests developed for measuring the degree of vulcanization with sulfur-cured compounds. These tests show that all of these materials are true vulcanizing agents. Comparison of the various vulcanizates with different types of unvulcanized rubber shows that the outstanding characteristic of the vulcanized structure is its resistance to flow under a wide variety of conditions. The vulcanized structure appears to be a composite one which varies with the rate of a reaction catalyzed by the vulcanizing agent, the rate of combination of the vulcanizing agent, the nature of the addition product, and possibly with differences in the nature of the catalyzed reaction.
Alanine in Rubber Latex
Authors: McGavack J. , Rumbold J. S.
Published: February 2011

INDIRECT evidence of the presence of amino acids in ordinary ammonia-preserved latex was obtained from electrometric titration work with the glass electrode, the application of which to latex was described in a previous article (2). A small sample of alanine has now been isolated and identified, and indication of the presence of phenylalanine has also been obtained; however, owing to the small amount of material, its identification could not be established. It is believed that this is the first amino acid to be isolated from latex in the pure state and positively identified; the fact that it has not been detected before may be due to the small amount usually present and to the great solubility of the substance. The only reference found in the literature relating to the presence of an amino acid in rubber is the article by Whitby, Dolid, and Yorston (3). These workers obtained a small amount of d-valine from the acetone extract of pale crepe. Glycine, proline, and leucine are apparently either absent or present in relatively small amounts. If the amino acids are derived from decomposition of proteins, the absence of glycine is rather remarkable since most proteins with a high alanine content—for example, silk fibroin—also contain this amino acid.
Rubber Plasticity Control. Significance and Value of Recovery Measurement of Williams Plastometer
Authors: Dillon J. H.
Published: February 2011

The experiments described in this paper were undertaken in an effort to discover under what conditions the recovery measurement has practical value in plasticity control testing. No conditions were found where the recovery measurement yielded any important practical information which could not be gained by measurement of y value alone. It must be borne in mind that no experiments of this nature can be considered as perfectly general. Certain cases, not specifically included in the experimental conditions employed, may exist where measurement of recovery has definite practical value. Furthermore, great caution should be exercised in applying these results to any types of compression plastometers other than the standard Williams instrument with which the tests were made.
The Perchloric Method for the Determination of Sulfur in Rubber
Authors: Kahane Ernest
Published: February 2011

The problem of the determination of sulfur in rubber has been dealt with extensively in the literature, and it seems as if discussions and descriptions of new technic are nowhere nearly ended yet. The determination is so essential, and its rapid and precise execution is of such importance in industrial technic, that efforts in this direction should not be regarded as wasted. In 1926 and in 1927 Le Caoutchouc et La Gutta-Percha contained two articles in which the present author discussed the conditions of the determination of sulfur in rubber and then proposed the use of a new oxidizing mixture, not mentioned previous to that time, which involved the destruction of organic substances by perchloric acid. This method consisted simply in the attack on a 1-gram sample of rubber by 10 cc. of nitric acid (d. 1.39) and 5 cc. of perchloric acid (d. 1.61). Upon heating, attack by the nitric acid takes place, and this is followed by evaporation of the excess nitric acid, then at a little higher temperature there is an attack by the perchloric acid, which oxidizes the rest of the organic substance completely. This publication was concerned much more, in the determination of sulfur by the perchloric method, with the general idea of the destruction of organic substances than it was with the precise details of carrying it out. The technic had been studied somewhat superficially, as is shown by the text of the article itself.
Alcoholic Potash Extraction of Vulcanized Rubber
Authors: Porritt B. D. , Scott J. R.
Published: February 2011

In the analysis of vulcanized rubber, the estimation of matter extractable by alcoholic potash solution has long been applied, chiefly as a means of detecting and estimating factice. The test was originally made by weighing the rubber before and after boiling with potash solution, the loss in weight being taken as representing the factice content (cf. Weber, The Chemistry of India Rubber, London, 1919, page 245). Though this method has now been generally superseded by that in which the extract is acidified and the resulting fatty acids are extracted with ether and weighed, the older “loss in weight” method is still prescribed in some specifications for rubber goods. It has long been recognized that the loss in weight is not an accurate measure of the factice content for the following reasons: (1) it is difficult to remove all the potash from the extracted rubber before weighing it (cf. Henriques, Chem.-Ztg. 18, 411(1894)), and (2) the potash extracts part of some mineral compounding ingredients, such as zinc oxide, litharge, and antimony sulfide (cf. Ditmar, Die Analyse des Kautschuks, Vienna, 1909, page 205). It has been found that another possible source of serious errors in the “loss in weight” method is the action of the potash on light magnesium carbonate. If magnesium carbonate is boiled with alcoholic potash solution, it loses a considerable amount of its combined carbon dioxide and/or water. Thus in an experiment where 0.3 gram of the carbonate was boiled for 6 hours with 60 cc. of potash solution (KOH 5 g., water 5 cc., absolute alcohol 100 cc.), and then washed with alcohol, dried in vacuo and weighed, it was found to have lost 29.4 per cent of its weight. By igniting the residue to magnesium oxide, it was shown that the potash had not dissolved out any magnesium compounds, so that the loss in weight must be attributed entirely to loss of carbon dioxide and/or water.
Studies in the Vulcanization of Rubber. VI. Thermochemistry
Authors: Blake John T.
Published: February 2011

IN A PREVIOUS paper (2) the heat of vulcanization was studied over the entire sulfur range by heat-of-combustion measurements. Data were also obtained on vulcanization with m-dinitrobenzene and selenium. Although it had been known qualitatively that there was a heat evolution during at least a portion of sulfur vulcanization, definite values were thus obtained for the first time. The results by this heat-of-combustion method are, however, of limited accuracy where small heat changes occur. The method consists in the determining of heat-of-combustion values on a rubber compound before and after vulcanization. Their difference represents the heat content change brought about by vulcanization and involves the subtraction of values of about 10,000 calories per gram. From the data obtained the conclusion was drawn that little or no heat is evolved below 6 per cent sulfur but that there is a steadily increasing heat evolution beyond this to 300 calories per gram of compound at 32 per cent sulfur. The first three points of these data (2, 4, and 6 per cent sulfur) gave an average value of 5 and a mean variation from zero of 18 calories per gram, representing approximately 0.05 and 0.18 per cent of the total heat of combustion—probably the order of the accuracy of the determinations. In the presence of an accelerator (diphenylguanidine) a definite heat evolution was found beyond 4 per cent sulfur, although none appeared at 1 and 2 per cent. Vulcanization of rubber with m-dinitrobenzene and selenium did not seem to give an evolution of heat.
Tear Resistance and Structure of Rubber
Authors: Busse W. F.
Published: February 2011

THE practical importance of tear resistance is so well recognized that numerous tear tests have been proposed (4); all of them are empirical and each gives results which differ, usually in unpredictable ways, from all others. However, with all their imperfections the common tear tests give information about rubber compounds that cannot be obtained by any other means. They have been used extensively to study the effects of pigments on rubber, particularly in trying to determine why gas black greatly improves tear resistance while other pigments, such as clay and whiting, reduce it. Unfortunately, many workers did not even recognize that gas black causes a different kind of tear from that found with other pigments. This is not true of Talaly (5) and Kirchhof (3) who recently published data on the knotty tear of gas black and latex stocks. The theoretical importance of tear tests has been almost totally ignored in spite of the fact that some tests, such as hand tear, are particularly sensitive to the structural changes that occur during cure, and almost all of the tests are sensitive to the effects of pigments on the structure of the rubber. A satisfactory theory of tear testing would not only lead to increased precision in practical tear tests, but there is every reason to believe that it would also yield a better understanding of the structures present in rubber.
A Mathematical Treatment of a Theory of Rubber Structure
Authors: Griffith T. R.
Published: February 2011

A brief consideration of the work that has been done on the structure of rubber convinces, one that the elasticity is wholly or at least mainly explained by a consideration of the kinetics involved. The fact that when a strip of stretched rubber, one end of which is free, contracts when it is warmed, contrary to the behavior of most bodies, and that it becomes warmed on stretching, commonly known as the Gough-Joule effect, pp. 453–461, would lead one to suspect .that there is a connection between the kinetic energy of the rubber molecule and its elasticity. Lundal, Bouasse, Hyde, Somerville and Cope, Partenheimer and Whitby and Katz have reported observations, principally stress-strain curves, which show that vulcanized rubber has a lower modulus of elasticity at higher temperatures, i. e., it becomes easier to stretch as the temperature is raised. On the other hand, Schmulewitsch, Stevens, and Williams found that the elastic modulus increases with the temperature. Williams shows that the softening of vulcanized rubber with rise of temperature is due to an increase of plasticity. In order to get rid of plastic flow, he first stretches the specimen several times to within about 50 per cent of its breaking elongation, and then obtains an autographic stress-strain curve of the rubber stretched very quickly. He finds that in this case the rubber actually becomes stiffer with rise of temperature, increasing temperatures causing the stress-strain curves to lean progressively more and more toward the stress axis. He concludes that rise of temperature has two effects, one a softening due to increase of plasticity, rendering plastic flow more easy, the other an actual stiffening of the rubber due to rise of temperature. It is not easy to explain the latter effect on any theory which does not take kinetics into account.
Forms of Rubber as Indicated by Temperature-Volume Relationship
Authors: Bekkedahl Norman
Published: February 2011

This paper describes measurements of the change of volume of rubber with change of temperature, which have been used as a means for determining the forms in which rubber may exist and ascertaining the conditions under which transition from one form to another may occur. This work is part of a study of the basic thermodynamic properties of rubber which is being conducted at the cryogenic laboratory of the National Bureau of Standards. In this study, an attempt was first made to measure the heat capacity of rubber over a wide range of temperature, but under some circumstances anomalies due to change in phase were encountered which took place so slowly that it was impracticable t0 follow them through by calorimetric methods. These anomalies have been studied by the measurement of the changes in volume or coefficient of expansion associated with them, it being possible to follow changes in volume over as long a period of time as desired. At temperatures at which rubber is relatively stiff and rigid, measurements of length have been used as an adjunct to the volume measurements. Measurements of the temperature-volume relations of rubber have been made by several previous investigators who have recognized the existence of rubber in different forms. The contribution of the present investigation lies in the fact that it reports a somewhat more comprehensive and systematic study than has been made previously. The findings are largely in accord with those of the other workers, as will be brought out in a subsequent section of the paper.
Accelerators in Hard Rubber
Authors: Davies B. L.
Published: February 2011

1. The curve relating the hardness to the time of heating of a high-sulfur stock indicated the presence of two consecutive reactions. The second half of the curve was mainly linear, and its slope might be used as a measure of the second (hard rubber) reaction speed. 2. The straight line when produced downwards passed through or near to the origin. Its position was altered only slightly by normal variations in processing. 3. The straight line may be represented by the equation H=rt+ƒ where H = per cent hardness by Shore's Durometer, t = time of heating in minutes, r = rate of hard rubber formation represented by the tangent of the angle between the curve and the time axis, and ƒ = the intercept along the hardness axis. 4. Influences which are known to increase the speed of chemical reactions increased the slope of the line. Thus, increase of sulfur concentration, rise of vulcanizing temperature, and the presence of catalysts increased the value of r, yielding a “fan” of lines all passing through a point near to or coincident with the origin. 5. The organic accelerators of vulcanization in general were found to act as true accelerators if present in small amounts. With increasing concentration they increased the speed of hardening at 150° C. up to a definite maximum, which appears to be approximately the same for many accelerators. 6. From an investigation of the minimum concentration of accelerator which produced the maximum slope, numbers representing the efficiency of the accelerators have been found. 7. Further addition of accelerator produced no further change in r, but a definite and progressive increase in the value of ƒ. This effect was also produced by the addition of mineral fillers. 8. If the value of H be taken as 100 per cent hardness, the equation H=rt+ƒ may be used for determining the time of cure. r is the rate of cure, dependent upon the nature of the accelerator, and the nature and amount of filler determine the magnitude of ƒ. Values of ƒ referring to some commonly used fillers have been determined. 9. The effect of increasing the temperature of vulcanization on the rate of hardening was examined. It was found that the temperature coefficient of hard rubber formation was not a constant quantity for accelerated hard rubber stocks. In many cases its magnitude increased to a maximum within the temperature range 140–150° C., and then fell at still higher temperatures.
Investigations of Unknown Components of Crude Rubber. I. Copper Content of Different Types of Crude Rubber
Authors: Shimada Keiichi
Published: February 2011

Small amounts of copper have been found to be present normally in all types of crude rubber. Standard smoked sheet and fine pale crepe contained 3.13 mg. and 2.32 mg. of copper, respectively, per kg. of rubber, whereas fine hard Para had a relatively large amount, viz., 5.50 mg. per kg. of rubber. Considering the wide distribution of copper in minute quantities in biological materials, it is most probable that the copper in the crude rubber is introduced from the original latex. The micro-estimation of copper in crude rubber was carried out by the colorimetric method proposed by the present author (J. Soc. Chem. Ind., 36, 263B (1933)), the procedure recommended by Ansbacher, Remington, and Culp (Ind. Eng. Chem., Anal. Ed., 3, 315 (1931)) for destroying the sample and dissolving the rubber ash being applied.
Determination of Free Sulfur in Rubber. I. Iodometric Method of Determination of Free Sulfur
Authors: Bolotnikov V. , Gurova V.
Published: February 2011

Up to the present time the determination of free sulfur has been carried out by extracting the rubber by acetone, followed by oxidation of the sulfur with bromine to sulfuric acid. This method has very substantial drawbacks, such as the fact that each determination of sulfur requires many hours, and the results of the analysis are received in the best cases on the second day. The method developed by the present authors is based on the iodometric method for the determination of sulfides, sulfites, and hyposulfites in the presence of one another. The rubber is treated with a solution of sodium sulfite Na2SO3, which transforms the free sulfur into hyposulfite, thus: Na2SO3 + S → Na2S2O3. The resulting solution. contains Na2SO3and Na2S2O3. The sample, about 2 g. of finely cut rubber, is put into an Erlenmeyer flask of 250–300 cc. capacity, and 100 cc. of 5% solution of sodium sulfite are added. Tests have shown that the best extraction of sulfur takes place in the presence of an excess of Na2SO3 over that required by the reaction. Five grams of dry sodium sulfite enough to extract from 0.05 to 2% S.
The Biofeedback Odyssey: From Neal Miller to Current and Future Models of Regulation
Authors: Binnun Nava Levit , Golland Yulia , Davidovitch Michael , Rolnick Arnon
Published: February 2011

Neal Miller's research on animals and humans launched the field of self-regulation, enabling individuals to take a more active role in their health and well-being. However, his inquiry into whether autonomic operant conditioning occurs remains open to debate. This article contends that present-day biofeedback therapists continue to be confronted by this dilemma. In addition, the authors suggest other models of biofeedback in which the role of the practitioner has been expanded and to which a large repertoire of self-regulation techniques have been added. They propose that, in the future, the regulatory capacity of interpersonal interactions is recognized as in the proffered model of biofeedback, dyadic biofeedback (DBF). DBF allows for real-time training of interpersonal interactions, emphasizing learning through direct observation and active involvement, thus making a return to Miller's model.
Ex Vivo Examination of the Biocompatibility of Biodegradable Magnesium via Microdialysis in the Isolated Perfused Bovine Udder Model
Authors: Schumacher Stephan , Stahl Jessica , Bäumer Wolfgang , Seitz Jan-Marten , Bach Friedrich-Wilhelm , Petersen Lars J. , Kietzmann Manfred
Published: February 2011

Purpose

Being biodegradable, magnesium is considered a promising future implant material but very little is known about the biocompatibility for the tissues in direct contact with it. In this study, the degradation of pure magnesium implants in the skin of an isolated bovine udder was examined over a period of five hours.

Methods

Microdialysis technique was used in order to investigate the reactions at the interface of implant and tissue. Pure titanium implants served as control. Degradation behavior and biocompatibility were evaluated via extracellular magnesium ion concentration and PGE2 and TNF alpha served as indicators of inflammation.

Results

Concentrations of 5.5 mmol/l Mg2+ were detected at the beginning, which decreased to a plateau of about 3.5 mmol/l after approximately two and a half hours. PGE2 and TNF alpha concentrations indicated no major inflammatory tissue response to the degradation.

Conclusions

These results give an idea of the ion burden at the implantation site of degrading magnesium and suggest good biocompatibility even at the tissue-implant interface.
Importance of IL-10 Modulation by Probiotic Microorganisms in Gastrointestinal Inflammatory Diseases
Authors: de Moreno de LeBlanc Alejandra , del Carmen Silvina , Zurita-Turk Meritxell , Santos Rocha Clarissa , van de Guchte Maarten , Azevedo Vasco , Miyoshi Anderson , LeBlanc Jean Guy
Published: February 2011

Lactic acid bacteria (LAB) represent a heterogeneous group of microorganisms that are naturally present in many foods and possess a wide range of therapeutic properties. The aim of this paper is to present an overview of the current expanding knowledge of one of the mechanisms by which LAB and other probiotic microorganisms participate in the prevention and treatment of gastrointestinal inflammatory disease through their immune-modulating properties. A special emphasis will be placed on the critical role of the anti-inflammatory cytokine IL-10, and a brief overview of the uses of genetically engineered LAB that produce this important immune response mediator will also be discussed. Thus, this paper will demonstrate the critical role that IL-10 plays in gastrointestinal inflammatory diseases and how probiotics could be used in their treatment.
Rationale for Industrial Hygiene Practice
Authors: Harris Robert L. , Cralley Lewis J. , Cralley Lester V. , Rose Vernon E.
Published: February 2011

The professional field of industrial hygiene has its roots in the profession of public health, which means the preservation of health and prevention of disease among people engaged in systematic labor for some useful purpose or the creation of something of value. The modern definition of industrial hygiene also includes protection of the health of persons living around a place of work from hazards that may arise from that place of work. This chapter focuses on various factors that are involved in relating environmental stresses to health and the rationale upon which the practice of industrial hygiene is based. A significant progress has been made during the past few decades in characterizing and controlling environmental health hazards in places of work. Various comprehensive industrial hygiene programs are being used effectively and exposures to work hazards are often well controlled. The techniques used in assessing occupational health stresses cover all the relevant components of each stress and ensuring that these are addressed in resulting control program.
Basic Aerosol Science
Authors: Reist Parker C.
Published: February 2011

Aerosol contaminants can be injurious to health, therefore it is essential to understand the behavior and properties of the aerosol. Health effects caused by aerosols depends on particle size and size distribution as well as on the composition of the particles. Other aerosol behavior including light scattering and coagulation can also vary markedly with particle size. This chapter focuses on various properties of the aerosol particle which influence the behavior, such as Stokes law, Reynolds number, Cunningham correction factor, particle motion, electrical properties, and optical properties.
Computed Tomography in Industrial Hygiene
Authors: Todd Lori A.
Published: February 2011

A variety of innovative measurement technologies have been used by industrial hygienists to evaluate human exposures to contaminants, monitor process emissions and leaks, and determine the effectiveness of ventilation systems. Temporal resolution has been reported important for understanding and effectively controlling the generation and transport of contaminants in air, for identifying chemical intermediates produced during a process, and for monitoring chemicals that are acutely toxic. Real‐time instruments are used to provide good temporal resolution of concentration fluctuations. The technique also combines the real‐time chemical detection methods of optical remote sensing. The environmental CT system generates near real‐time spatially and temporally resolved two‐dimensional concentration maps of multiple chemicals at low limits of detection. Besides this, refinement of ORS instrumentation and low cost retroreflector arrays has also been discussed.