bluuebunny/crossref_metadata_2025 huggingface dataset:
The Measurement of the ph Value of Rubber Latex
Authors: Mackay J. G.
Published: February 2011

E. A. Hauser has stated in his Gow Lectures on “The Colloid Chemistry of Rubber” that the most satisfactory method of determining the ph value of latex is by means of the Wulff ph tester. This instrument, which is manufactured by Messrs. F. and M. Lautenschlager, Münich 2, S.W. 6, determines ph value by a colorimetric method. Strips of gelatin which have been impregnated with various indicators to render them suitable for different portions of the ph range are supplied; the range of ph values has thus been subdivided into five zones, and a scale of comparison colors is supplied for each of these zones. The principle of the instrument is that gelatin is permeable only to the serum of a turbid dispersion such as latex; when an impregnated strip, or, as it is usually termed, an indicator foil, is dipped into the turbid liquid some serum liquid passes within and produces a change in the color of the indicator; at the same time the gelatin, by swelling, prevents any considerable diffusion of this colored portion of the serum into the bulk of the turbid dispersion. The foil is left in the turbid liquid for one minute and then dried in blotting paper. Its color is then compared with the series of colors on the comparison scale supplied.
Experiments on the Causes of the Deterioration of Ebonite when Exposed to Light and Air
Authors: Webster D. M. , Porritt B. D.
Published: February 2011

(1) The surface film of a sample of ebonite—containing no “free” sulfur—has been shown to develop distinct traces of sulfurous and sulfuric acid after exposure to light in a moist atmosphere for a period of four weeks. (2) The above acids appear to result from the oxidation of hydrogen sulfide formed through the decomposition of the hydrocarbon-sulfur nucleus of the ebonite. (3) The rate of evolution of hydrogen sulfide from ebonite when heated in an atmosphere of hydrogen has been investigated for temperatures ranging from 180° to 250° C., and for three different samples of ebonite. (4) For a given temperature the rate of evolution is rapid at first, but falls off quickly and finally remains uniform over a long period, the latter portion of the time-H2S curve being linear within the limits of experimental error. (5) The rate of evolution increases with increasing temperature. (6) Under the heat treatment the ebonite changes in color, becoming reddish in appearance. At the same time it becomes unsaturated and more and more soluble in acetone and carbon disulfide. (7) The decomposition which takes place on heating ebonite to temperatures not exceeding 250° C. does not appear to give rise to appreciable amounts of either free sulfur or volatile organic compounds. (8) The bearing of the above results on the problem of the electrical deterioration of ebonite has been discussed.
Studies in the Vulcanization of Rubber. I—Thermochemistry of Vulcanization of Rubber
Authors: Blake John T.
Published: February 2011

WHEN a chemical reaction takes place, it is usually accompanied by an absorption or evolution of heat. The amount of the heat interchange is not a direct measure of the chemical affinity involved in the reaction, nor is it a measure of the free energy of the reaction. The heat of reaction, however, is a measure of the total change in internal energy and is of importance, therefore, in calculating the effect of temperature on a reaction and in elucidating the mechanism of it.
Studies in the Vulcanization of Rubber. IV—A Theory of Vulcanization of Rubber
Authors: Boggs G. R. , Blake J. T.
Published: February 2011

A new theory has been advanced which, it is believed, explains completely the various phenomena connected with the vulcanization of rubber. It is entirely a chemical theory based on the existence of two separate and distinct rubber compounds, soft vulcanized rubber and ebonite. The theory explains satisfactorily the aging of rubber, the variation in combined sulfur at optimum cure caused by acceleration, the kinetics of vulcanization, the characteristics of various vulcanizing agents, the thermochemistry of vulcanization, the electrical properties of rubber, the reclaiming of rubber, and the Joule effect. A brief review and discussion of the phenomena and past theories of vulcanization have also been given.
Autographic Stress-Strain Curves of Rubber at Low Elongations
Authors: Somerville A. A. , Ball J. M. , Edland L. A.
Published: February 2011

(1) Ring or loop test pieces permit autographic records to be drawn at constant speed. (2) A longer, larger test piece permits more accurate results to be obtained. (3) The effect of temperature of the test room is most important; speed of testing machine and direction of mill or calendar grain in sample less so; effect of relative humidity is nil. (4) The 10-inch (2.5-cm.) loop test piece described gives fairly accurate stress-strain data at low elongations, which probably is within the field approaching the action of rubber goods in service.
Carbon Black in Rubber Insulating Compounds
Authors: Wiegand W. B. , Boggs C. R.
Published: February 2011

1—It has been shown that, in conformity with published behavior of other conducting substances (metallic sols, etc.), carbon black may be incorporated in a dielectric such as rubber without detracting from its insulating or dielectric properties. Published results to the contrary were in error, probably because the material was added in excessive amounts. 2—In addition to this effect, it has been shown that the well-known ability of carbon black to adsorb water and dissolved electrolytes endows carbon black???rubber insulating compounds of various types with improved dielectric strength, resistivity, and power factor, the specific inductive capacity remaining substantially unchanged. In some cases this improvement may exceed 50 per cent. 3—The prevailing opinion that carbon black is injurious to rubber insulating compounds which are to be used next to the wire, or which in general are expected to serve as electrical insulation, has been shown to be erroneous, provided the proper proportions are employed. 4—These results would seem to render advisable the rewriting of many specifications dealing with rubber insulating compounds, and thus make it possible to apply the well-known beneficial effects of carbon black compounding—improved toughness, density, wearing resistance, imperviousness to light, tear resistance, etc.—to the electrical insulation field, from which it has hitherto been barred. 5—Although it is strongly recommended that the proper dosage of carbon black (which must be of suitable quality and thoroughly dry) be redetermined in each case, the writers' results would indicate that up to 10 per cent of carbon black on the crude rubber (plus the rubber content of any reclaimed rubber present) will effect the desired improvement in electrical properties.
The Structure of Synthetic Types of Rubber. Polychloroprenes
Authors: Klebanskii A. L. , Vasil'eva V. G.
Published: February 2011

Ozonization is one of the most successful and most exact methods for determining the structure of rubber. It was this method which was first used by Harries and his numerous collaborators for determining the structures of various types of natural and synthetic rubbers. By ozonizing solutions of natural rubber, Harries obtained ozonides, the decomposition of which yielded levulinic acid and levulinic aldehyde. This was proof that the combination of isoprene residues in the rubber molecule is in the 1,4-1,4 position, and it also showed the nature of the base molecules of rubber and the manner in which they are united in chain formation. On the other hand, these investigations did not give any decisive evidence as to whether the rubber molecule is an open chain or has a ring structure. At the beginning of his investigations in this field, Harries assigned to the hydrocarbon which is the fundamental constituent of the rubber molecule the following formula:
The Amphorous and Crystalline Forms of Rubber Hydrocarbon
Authors: Parks George S.
Published: February 2011

The coefficients of thermal expansion and the heat capacities of rubber hydrocarbon, both in an amorphous and in a so-called crystalline form, have been recently reported in two papers by Bekkedahl and Matheson. According to these investigators, the amorphous form undergoes a transition of the second order in the neighborhood of 199° K. Above this temperature they found a rather abrupt increase of approximately 205 per cent in the volume coefficient of thermal expansion, and one of about 38 per cent in the heat capacity. These phenomena are strikingly similar to those found in numerous studies on glasses in this laboratory, and especially in the recent investigation on polyisobutylene by Ferry and Parks. Thus, with the particular sample of polymerized isobutene employed, the transition region centered around 197° K. and the subsequent increases in volume coefficient and heat capacity were 200 and 32 per cent, respectively. Bekkedahl and Matheson found that, by cooling the amorphous rubber hydrocarbon to about 230° K. and then permitting it to warm up slowly over a period of days, their material could be obtained in a “crystalline” form. These “crystals” melted at 284° K. with a heat of fusion of 4.0 calories per gram. They also exhibited the previously mentioned second-order transition at about 199° K., but with somewhat smaller subsequent increases with rising temperature, i. e., about 165 per cent increase in the volume coefficient of thermal expansion and 28 per cent in the heat capacity. Two facts appear surprising and highly significant with these “crystals”: (1) the value of the heat of fusion which is extremely low compared with the figures of 20 to 54 calories per gram hitherto reported for various aliphatic hydrocarbons melting near room temperature, and (2) the duplication of the second-order transition found previously for amorphous rubber hydrocarbon.
Gutta-Percha. Effect of Vulcanization on Its X-Ray Diagram
Authors: Fuller C. S.
Published: February 2011

EARLY x-ray investigations by Clark (2) and Ott (13) on gutta-percha and balata established the fact that these materials were crystalline in nature even in the unstretched condition. In 1927 Hauser and his co-workers (5) pointed out the similarity of the diagrams obtained on gutta-percha and balata, but it remained for Hopff and Susich (7) to establish definitely the identity of the x-ray diagrams of the two substances. In addition they brought out the interesting fact that, on heating above 60° C., a characteristic change took place in the gutta-percha diagram. Hauser and Susich (6) made a detailed study of this change. They showed that gutta-percha (and hence also balata) underwent a change in crystalline structure at about 68° C. The beta modification, obtained above this temperature, did not transform back into the low-temperature or alpha form, but remained unchanged unless the cooling took place very slowly through the transition point. The last-named authors gave much attention to the securing of well-oriented fiber patterns of both crystalline forms in order to calculate their respective identity periods along the fiber axis. Their results, which are probably the most reliable published to date, give the. alpha form of the hydrocarbon an identity period of 8.78 ± 0.12 A˚. and the beta form an identity period of 4.87 ± 0.07 A˚. More recently Bruni and Natta (1) have examined gutta-percha by means of electron rays and have given a solution for the alpha form in which they find the unit cells to be orthorhombic and to have the axes: a=6.53 A., b=7.68 A˚., and c=9.60 or 4.80 A˚. (fiber period). They find the number of isoprene units (C5H8) per cell to be four.
Natural and Synthetic Rubber. XVI. The Structure of Polystyrene
Authors: Midgley Thomas , Henne Albert L. , Leicester Henry M.
Published: February 2011

Styrene treated with sodium and alcohol gives 75% of ethylbenzene and 25% of 1,4-diphenylbutane. This shows that polystyrene should be represented by formula II, in opposition to the heretofore accepted formula I. Only formula II is consistent with Mack's explanation of the rubber-like elastic properties of polystyrene.
The Mode of Action of Disulfide Accelerators of Vulcanization
Authors: Langenbeck W. , Rhiem H. C.
Published: February 2011

The catalytic power of organic compounds in general has up to the present time been studied much less extensively than that of inorganic compounds. For about the last ten years, however, the first author has, in collaboration with a number of his students, attempted to fill this gap, though so far efforts have been confined to explaining the mode of action of natural enzymes by means of comparative experiments with organic catalysts. As a result of this work, a theory based on experimental facts has been developed to explain in a satisfactory way the action of enzymes. The other phase of organic catalysis is, strictly speaking, a technical problem. Why for instance should it not be practicable to utilize organic catalysts more extensively than heretofore in industry? If this problem is to be attacked, it seems reasonable to start with the particular industry which already uses organic catalysts to the greatest extent. This is, of course, the rubber industry. The important accomplishments of the chemical industry with respect to the development of vulcanization accelerators is already common knowledge, and the important task at present is not simply to increase the great number of accelerators already known. A problem of more practical value would seem to be to study the mechanism of the acceleration of vulcanization, about which relatively little has been known heretofore.
Specific Properties of Artificial [Buna] Rubber
Authors: Koch Albert
Published: February 2011

Developments in the Synthesis of Rubber Because of the peculiar properties of natural rubber, its usefulness is somewhat limited, and in many fields of application it is quite unsuitable. In contact with oils and fats it swells rapidly and loses almost completely its good mechanical properties, and besides this natural rubber has poor resistance to heat. Again it is attacked rather easily by oxygen, and on exposure to oxygen and light simultaneously there is a particularly strong tendency to develop cracks within a short time; it is for such reasons that the chemical industries of various countries have been looking for an artificial or synthetic product which is free from the shortcomings of natural rubber or exhibits them to only a relatively small extent. Experimentation on artificial rubber has depended fundamentally on the discovery of Harries that the natural rubber molecule is constructed of isoprene units. Isoprene and its allied hydrocarbons were prepared by Hoffmann and his coworkers at the Elberfeld dye works, and these compounds were in turn polymerized to masses similar to rubber. These experiments were carried out before the World War. Because of a shortage of raw materials during the War, it was necessary to adapt the laboratory results to a factory scale sooner than should logically have been done. At that time the most readily available technical raw material was dimethylbutadiene, a compound which differs from isoprene by the presence of an extra methyl group, as may be seen in Table I.
Nonsolvents in Rubber Cements
Authors: Ford T. Foster
Published: February 2011

ETHANOL has long been used for reducing the apparent viscosity of rubber cements. Other rubber nonsolvents, especially acetone and amyl acetate, are sometimes similarly employed. However, there are few data in the literature from which adequate comparisons among nonsolvents may be deduced, nor has any systematic study of the properties of a cement containing nonsolvents been reported. Whitby (2), studying a long list of chemicals as solvents, records comparative swelling power for rubber and nitrocellulose; Whitby and Jane (3) find the viscosity of dilute rubber solutions to be reduced by a number of these materials; and Kawamura and Tanaka (1) obtain the following order of decreasing precipitant value for a 0.25 per cent solution of rubber in xylene—methanol, ethanol, n-butanol, isobutanol. With the exception of the swelling experiments, these results, as is the case with practically all published cement studies, are for dilute solutions only and therefore are of little technical value. The present experiments were performed with a commercial cement and are the result of a wish to control particularly two properties—the thickness of rubber film deposited upon an article by dipping and the tendency of the wet film to break across small holes in perforated objects. The addition of a suitable nonsolvent to a cement improved the film-breaking property, and by changing the proportion of the nonsolvent, with proper regard for other factors, satisfactory control of both film breaking and film thickness was possible. As here reported, the results afford a basis for comparison among the more common nonsolvents in cements in which the solvents used are benzene, Varnish Makers and Painters' (V. M. & P.) naphtha, or ethylene dichloride; and for a benzene-isopropanol cement they show the nature of the effects upon the properties studied, of simultaneously varying the proportion of nonsolvent, the concentration of nonvolatile ingredients, and the degree of mastication of the rubber stock. Results on temperature and humidity control are included to illustrate the importance of these factors in dipping-room operations.
Rubber Latex for Road Surfacing
Authors: Wren W. G. , Faircloth A. T.
Published: February 2011

(1) Methods of preparing sections for microscopical examination have been developed in order to obtain information as to the structure of latex-cement mixtures. (2) A large range of protective colloids which act as stabilizers of rubber latex have been examined as to their effect on the physical properties of aluminous cement, particularly on the rate of setting and hardening and tensile strength. Important differences in the effects produced by these substances have been found. (3) The possibilities of preparing a rubber cement crumb for consolidation on the highway are under examination. (4) A few experiments on the effects of compounding ingredients on the tensile strength of dried latex (without mastication) have been made. Silica gel improves the tensile strength of the dried film.
Hardness of Vulcanized Rubber at Low Temperatures
Authors: Nagai Hiroshi
Published: February 2011

1. By means of a new apparatus which is described, it is possible to estimate the hardness of vulcanized rubber at low temperatures. 2. The hardness of rubber-sulfur vulcanizates increases hyperbolically with lowering of temperature and they become “frozen” and hard at −50° C. 3. Since ordinary softening agents having high viscosities solidify at −30° to −40° C., these are unsuitable for softening rubber to be exposed to temperatures below this range. 4. Softening agents which do not solidify at −50° C. are among those ordinarily used as solvents, and they have very low viscosities. Though their effect on the hardness of rubber at −50° C. is small when they are used in small percentages, they prevent the freezing of rubber at −50° C. when large proportions are used. They are, however, of no practical value, since they decrease the tensile strength of rubber. 5. Vulcanized rubber containing 30 per cent of reclaimed rubber also froze to a hard product at −50° C. 6. The relation between temperature and hardness of rubber vulcanized with organic accelerators is the same as that in the case of rubber vulcanized with sulfur alone.
The Viscosity Characteristics of Rubber Solutions
Authors: Philippoff W.
Published: February 2011

As is well known, solutions of rubber in organic solvents exhibit a variety of noteworthy properties which are characteristic of solutions of lyophilic colloids, to which rubber belongs. These properties, notably high viscosity even in dilute solution and structure viscosity, distinguish these solutions from those of normal substances of low molecular weights. In the present article, the attempt is made to assemble known facts about viscosity phenomena and at the same time to add certain experimental data, heretofore unpublished, to the available literature on the subject.
Studies on the Joule Effect of Rubber. II. Thermal Effect on Stretched Latex Vulcanizates
Authors: Tanaka Yoshio , Kambara Shû
Published: February 2011

Latex vulcanizates behave with regard to the Joule effect similarly to ordinary vulcanized rubber when heated and cooled in a stretched condition. The observed thermal effect is assumed to represent the Joule effect. This effect is reduced chiefly by depolymerization and disaggregation of the rubber, and is increased by vulcanization, which may be followed by polymerization of vulcanized rubber molecules and an increase of the polar affinity of each molecule and micelle.
Swelling and Solvation of Rubber in Different Solvents
Authors: Williams Ira
Published: February 2011

The large variation of the fractional increase in viscosity of rubber sols and its lack of relation to the viscosity of the solvent indicates that the increase in viscosity is not due to rigid filiform molecules. The ability to interchange solvents and obtain a viscosity characteristic of the solvent shows the existence of a reversible equilibrium between solvent and rubber. The close relation between the maximum swelling and the fractional increase in viscosity of rubber in different solvents suggests that rubber sols contain swollen micelles of rubber. The extent of swelling and the viscosity depend on the equilibrium between solvent and rubber which, in turn, depends on the state of oxidation (or other suitable chemical attack) of the rubber. A rubber sol becomes a gel at the concentration which immobilizes essentially all the solvent. The relative viscosity of rubber sols of equal concentration in the same solvent is probably some function of the degree of solvation of the dispersed particles which is influenced by the degree of oxidation of the rubber. Viscosity is not a measure of the molecular weight.
The Fine Structure of Crystallized Rubber
Authors: Lotmar W. , Meyer K. H.
Published: February 2011

Whereas in the unstretched state rubber gives on examination by x-rays the diagram of a liquid, in the stretched state it gives a well-defined fiber diagram. This was first described by Katz in 1925. Since that time the crystalline interferences of rubber have been studied by several investigators. The first classification of these interferences was undertaken by Hauser and Mark, who arranged them in the form of a rhombic lattice. Later, working with a thin film of highly stretched rubber, Mark and von Susich succeeded in obtaining preparations with a higher degree of orientation. According to whether it was irradiated parallel or perpendicular to the surface of the film, such a preparation showed different intensities of the reflections. In this way Mark and von Susich succeeded in obtaining a different and more reliable indication of the reflections than did Hauser and Mark. Mark and von Susich found a rhombic elementary cell with axes of 8.3 ± 0.1 A. U., 8.1 ± 0.1 A. U. (fiber axis), and 12.3 ± 0.1. A. U. On the basis of their better established elementary cell, Mark and von Susich developed a space model of rubber which agreed fairly well with the largest intensity effects. In constructing this model they relied on the assumption expressed by Meyer and Mark that primary valence chains of the formula:
A Survey of Latex Coagulants Used by Malayan Small-Holders
Authors: Rhodes Edgar
Published: February 2011

A survey was made of the coagulants employed by Malayan small holders. Though in the main these small holders are employing formic and acetic acids, sulfuric acid is employed to a much greater extent than has been supposed. Propaganda against the use of this coagulant was commenced recently through the Small-Holders' Advisory Service, and reports from the districts are encouraging.
Soft Vulcanized Rubber. Effect of Temperature and Oxygen Pressure on Aging Rate
Authors: Ingmanson J. H. , Kemp A. R.
Published: February 2011

IMPORTANT to the manufacturer and consumer of rubber goods are suitable accelerated aging tests for predicting readily the life of rubber articles under the variable storage and service conditions encountered. Since service conditions may involve the exposure of rubber to wide variations of temperature, light, and atmosphere under various types of mechanical strain, there is obviously need for a variety of tests, each designed to emphasize factors which are most important in any given set of service conditions. Since the primary cause of failure of soft vulcanized rubber in service is oxidation, emphasis has been placed on tests which accelerate the oxidation effect. The most widely adopted and generally satisfactory procedure of this type is the Bierer and Davis oxygen bomb method which involves heating the rubber under oxygen pressure. In Bierer and Davis' original publication (2), results were shown on the effect of increasing oxygen pressure in increments of 28.1 kg. up to 112.5 kg. per cm. on the aging of two different rubber compounds at the three temperatures, 50°, 60°, and 70° C. Their results showed that in some cases there was a uniform increase in aging rate with increased pressure and in other cases the rate increased rapidly up to a pressure of 28.7 kg. per sq. cm. but more slowly with further increases in pressure. In a later investigation (3) the same authors employed a pressure of 21.1 kg. per sq. cm. and 60° C. throughout. For the past ten years most laboratories have used an oxygen pressure of 21.1 kg. per sq. cm. and a temperature of 70° C., which may therefore be considered as standard.
Determination of Sulfur in Rubber. Use of Tetrahydroxyquinone as a Titration Indicator
Authors: Sheen Robert T. , Kahler H. Lewis , Cline Delbert C.
Published: February 2011

The determination of sulfur in rubber by the precipitation of oxidized sulfur as sulfate by means of barium chloride and the back-titration of the excess barium has been shown to be as accurate as the gravimetric procedure in solutions of the characteristics described above, for the determination of sulfur, with the use of tetrahydroxyquinone as the indicator. The method is very rapid compared to the gravimetric procedure and after oxidation to the sulfate form in solution, a determination can be made on a single sample in 20 to 30 minutes; with groups of analyses this time can be greatly reduced when compared to the time required for a single analysis.
The Carbon Reinforcement of Rubber
Authors: Wiegand W. B.
Published: February 2011

Evolution Discovered in England in 1910 where, however, insufficient quantities were used, and developed commercially in Akron in 1912, its evolution may be roughly divided into three periods: 1913–1920, during which time the art led the science; 1920–1927, during which time science led the art, and 1927–1934, when the art once more overtook the science, leading to the empirical employment of 50 per cent or more of carbon on the rubber. At the present time there is needed a fresh theoretical approach. The Course The scope of carbon reinforcement may conveniently be defined as the region of positive Delta A values. The shape of the Delta A curve is in itself interesting as to symmetry, the presence of a well-defined maximum, and the extraordinary extent of positive values compared to other reinforcing pigments. Position of Maximum The published data on carbon Delta A functions have been assembled together with fresh data, the latter including both litharge and Captax accelerated mixings. Considerable discrepancies appear. A mean curve has been drawn to include the recent data, and previous work in which fatty acids were employed. This mean Delta A curve for carbon black shows a maximum at 26.3 per cent by volume of carbon on the rubber, corresponding to 51 per cent by weight. This mean curve cuts the base-mixing energy axis at 53.6 volumes of carbon, or approximately 105 per cent by weight.
The Use of Acetylene in the Rubber Industry
Authors: Walter Paul
Published: February 2011

Considering the advantages to be gained as a result of the favorable effect which acetylene has on rubber, it would be of still greater interest to study: (1) the coagulation of latex by acetylene, and (2) the fixation of acetylene by reclaimed rubber and by factice. Such studies should be of great significance, and if successful results were to be obtained, a large market for calcium carbide would be created. The use of calcium carbide in the rubber industry is of interest at present in three ways: (1) Its technical advantages, including the improvement to be gained in the quality of the rubber products, and the simplification of manufacturing operations. (2) Its economic advantages, i. e., the lower costs. (3) Its consumption, which, though impossible to foresee even in an approximate way, is possibly indicated by the following estimates: Balls and balloons 800 tons per year Sponge articles 200 tons per year Latex products 500 tons per year 1500 tons per year This total of 1500 tons per year is not of great significance, because it would be misleading to assume that all the manufacturing plants which make the articles described would use calcium carbide. To offset this, it has just been mentioned that there would be a very large consumption of calcium carbide if latex were to be coagulated by acetylene, or indirectly by calcium carbide, by some economical process, as seems possible. In conclusion, there are always unexpected uses for calcium carbide and acetylene in the rubber industry.
Mastication and Rate of Set-Up. Part I
Authors: Buchan S.
Published: February 2011

Until comparatively recently the importance of rate of set-up measurements in rubber compounding and in factory control testing received very little attention, but within the last few years various methods have been devised and used by different investigators. In many laboratories, the standard method of testing utilizes the change in physical properties which occurs when the rubber is converted from a plastic mass to an elastic solid under the influence of heat, the course of the reaction being traced by means of a plastometer. With a plastometer of the parallel plate type, such as the Williams instrument, a number of cylindrical test samples of known volume are cut from the mixed rubber under examination, and placed in the oven of the plastometer, maintained at a constant temperature. At definite intervals individual samples are tested on the plastometer and a note is made of their plasticities or, it may be, of their recoveries. When either of these sets of readings is plotted against the time of heating, it is usually observed in an accelerated mixing that the point at which vulcanization commences is shown by a steep inclination of the curve away from the time axis.
Secondary Changes during Vulcanization of Ebonite. Part I
Authors: Davies B. L.
Published: February 2011

(1) During the vulcanization in steam or water of sulfur-rubber mixes containing a high proportion of sulfur, there was a change of weight due to (1) loss of sulfur by volatilization, (2) loss of hydrogen sulfide, (3) absorption of moisture, (4) loss of soluble matter, (5) evolution of volatile products. (2) Loss of sulfur from the mix was high when vulcanization was carried out in steam, and low when vulcanized in water. In the former case, it produced an outer layer of appreciable thickness which was deficient in free sulfur. This layer was, however, not visibly different from the remainder. The sulfur was lost during the earliest stages of heating, and ceased when evolution of hydrogen sulfide became appreciable. The surface loss may or may not affect the vulcanization coefficient. (3) The mechanism of sulfur loss has been discussed. It was shown that sulfur reacts with steam or water under vulcanizing conditions, yielding a small quantity of hydrogen sulfide. The other reaction product could not be detected by the use of barium chloride in the case of steam heating, but in water some evidence of the presence of oxides of sulfur was obtained. It was concluded, therefore, that although a part of the sulfur lost probably results from successive oxidation and reduction, most of the sulfur is distilled from the surface of the sample. At the same time it was shown that water and steam, in the presence of iron, yield a reducing substance assumed to be hydrogen. (4) Absorption of water was much larger during vulcanization in water than in steam. In both cases the period necessary to attain a minimum weight on exposure to air was very long, the time depending upon the thickness of the slab. (5) After this period, oxidation proceeded at a velocity which was approximately constant for a given sample. This rate was therefore used to calculate the actual weight lost during vulcanization. (6) After allowing for oxidation and for water-absorption, it was found that the loss of weight sustained during vulcanization was not a pure function of the surface area, but increased with increasing volume. (7) The amount of water absorbed varied similarly.
Contributions to the Analysis of Rubber. I. Determination of the Water-Soluble Components of Rubber
Authors: Dekker P.
Published: February 2011

1. It is shown that the methods which are ordinarily used for determining water-soluble substances in raw rubber give low results, and are quite useless for vulcanized rubber. 2. New analytical procedures are developed for determining the water-soluble substances in raw rubber and in vulcanized rubber. These procedures are carried out in the following manner. (a) Raw Rubber.—Heat 2 grams of rubber in 80 cc. of xylene and 5 cc. of acetic acid on a water bath until the rubber is completely dissolved, add 5 cc. of acetic acid and 10 cc. of water, heat for 3–4 hours on the water bath with frequent agitation, transfer to a distilling flask (rinsing the first flask with 50 cc. of hot water), distill the xylene with steam, filter the residual solution, evaporate the filtrate on a water bath; and dry at 100° C. (b) Vulcanized Rubber and Rubber Mixtures.—First extract the sample with acetone, heat 2 grams of the acetone-extracted sample with 80 cc. of xylene on a water bath, add 5 cc. of acetic acid, reflux the mixture on an oil bath, after complete dissolution add 5 cc. of acetic acid and 10 cc. of water, heat the solution for 2 hours on an oil bath at 110–120° C., distill the xylene, as in the determination with raw rubber, filter the residue, evaporate the filtrate to dryness, take up the residue in 50 cc. of water, pass a current of hydrogen sulfide through the solution for 10 minutes to precipitate zinc as sulfide, filter, evaporate the filtrate, and dry the residue at 100° C. 3. In the presence of calcium compounds, magnesium compounds, glue and textiles, the method gives false results. Modifications of the method are therefore recommended, whereby these substances are eliminated.
Physical Testing of Latex Films
Authors: Flint C. F. , Naunton W. J. S.
Published: February 2011

Determinations of the tensile strength of latex rubber involve difficulties which concern either the preparation of the sheets or the technic used in breaking them. Thick sheets of latex rubber may be cut into dumb-bell or ring test-pieces, which may then be broken on a tensile-testing machine of normal type. The preparation of thick sheets is, however, a matter of difficulty, owing to the fact that the complete drying-off of the water takes such a long time. Thus when ultra-accelerators are under test, vulcanization of the sheets may be advanced, or even complete, before the sheets are dry, so that investigation of the early stages of cure is impossible. Further, during the time that elapses before evaporation has gelled the whole thickness of latex, sedimentation of the compounding ingredients may occur in the mass of the fluid sheet, resulting in vulcanizates which are not uniform in composition or degree of cure. The use of devices such as porous tiles or the expedient of flowing the latex onto the surface of a gelatin jelly is objectionable because they absorb water-soluble components as well as water from the latex mix. Further, although they tend to prevent sedimentation by promoting more rapid gelling, the complete elimination of the water from a thick sheet is still a lengthy process, during which complete self-vulcanization may easily occur. The use of chemical coagulants is open to the same objection, which is of course overshadowed by the much more serious obstacle of their effect on the activity of accelerators and on the physical properties of the latex rubber.
Determination of Free Carbon in Rubber Goods
Authors: Oldham E. W. , Harrison J. G.
Published: February 2011

The carbon black analysis should not be made without a consideration of the nature of the original stock. The size of the sample must be related to the black content. To lessen time consumed in this analysis, preliminary extraction of the sample should be omitted. The correction factor for clay must be applied. By the revised method greater accuracy is obtained, although there is still a tendency for the results to be higher than calculated. Precision in this method seems to depend mainly upon accuracy of weighing and avoiding the loss of small particles of black.
The Preparation of Thin Films
Authors: Sager T. P.
Published: February 2011

VARIOUS means which have been suggested for the preparation of thin films of rubber and similar materials include their deposition on glass, porcelain, sheet metal, and mercury. The use of rigid surfaces is open to the objection that in the case of some materials the adhesion of the film may be troublesome. The removal from such surfaces, of films of materials which are subject to permanent deformation on stretching, tends to lessen the uniformity of their thickness. In connection with the study of the permeability to gases of thin films unsupported by fabric, a satisfactory and simple method was found for their preparation.
Colloidal Structure of Rubber in Solution
Authors: Gehman S. D. , Field J. E.
Published: February 2011

Analysis of the light scattered transversely by rubber solutions indicates that the units of structure responsible for the scattering are large compared to the wave length of light and possess a high degree of anisotropy. The scattering in many respects resembles that from a pure liquid more than that from a colloidal suspension. This is especially true for solvents of refractive index nearly the same as that of rubber and for high concentrations. In view of these facts the most probable view in regard to the structure appears to be that it is a loose structure of anisotropic groups with hindered rotation analogous to the cybotactic groups in a liquid.
The Absorption and Diffusion of Water in Rubber
Authors: Daynes H. A.
Published: February 2011

A new differential equation of diffusion is put forward to represent the movements of water vapor through rubber in accordance with the osmotic theory of absorption. Experiments are described which, together with the evidence quoted from existing knowledge, confirm a number of predictions as to differences between the absorption of a gas and of water vapor by rubber. These predictions deal with the shapes of the absorption- and desorption-time curves between narrow and wide limits of humidity, the relative times required for absorption and desorption, and the variation of absorption and desorption periods with thickness of the rubber sheet. The results are definitely inconsistent with the simple gas-diffusion theory, which is often assumed to apply to water in rubber. It is established that the shape of the humidity-absorption curve is a dominant factor in determining time-water content relations. Except for changes over very restricted ranges of humidity, the absorption- and desorption-time curves are of different shape, and desorption is much more rapid than absorption. The periods required for absorption and desorption are greater, the higher the humidity and the higher the hygroscopicity of the rubber. The law that the time required to reach a given stage of saturation varies as the square of the linear dimensions of the sample (the shape being constant) is equally true for diffusion, according to the old and new equations.
Nature of the Diffusion Process in Rubber
Authors: Barrer Richard M.
Published: February 2011

It is known that silica-gas diffusion systems exemplify a type of non-specific activated diffusion process, as opposed to the specific type of diffusion system, such as hydrogen-palladium. It seemed that the diffusion of gases through other “glass-like” materials such as some organic membranes, for example rubber, might offer further examples of non-specific activated diffusion. The data needed to test this hypothesis were available in papers by Edwards and Pickering, and by Dewar. Graham first noted the large temperature coefficient of the diffusion process through rubber, and that the diffusion velocities had no connection with the molecular weights.
The Oil Resistance of Rubber
Authors: Tanaka Yoshio , Kambara Shû , Hirakawa Kenji
Published: February 2011

The thermal effects of benzene on various rubber films are correlated with the polar and oil-resisting properties of rubber. By means of quantitative experiments on these effects, natural crude rubber was proved to be a non-polar material; purification, vulcanization, mastication, irradiation by ultra-violet rays, and chlorination increase the polarity of rubber. Synthetic films show small thermal effects because of the high polar properties and the compactness of structure of the films.
The Evolution of Heat during Vulcanization
Authors: Oberto S.
Published: February 2011

An experimental apparatus has been developed by means of which it is possible to measure with a high degree of precision the heats of vulcanization of rubber mixtures containing even very low percentages of sulfur, at temperatures as low as 110° C. Studies of vulcanization on a strictly thermochemical basis now appear both practicable and promising. An evolution of heat of vulcanization is accompanied by an improvement in the mechanical properties of a rubber mixture. The quantity of heat evolved does not seem to be a linear function of the percentage of combined sulfur, at least for low percentages.
The Brittleness of Ebonite
Authors: Ariano R.
Published: February 2011

The results of tests of the brittleness of ebonite are described. Resilience is influenced chiefly by the moment of inertia of the cross section of the test-specimen, but it seems also to be affected by the form of the specimen. The state of vulcanization has considerable influence on these mechanical properties within the undercured range, but with thorough vulcanization the state of cure plays no appreciable part. Notching of test-specimens is not of great importance. It diminishes the resilience, but when the tests are compared on a basis of equal moments of inertia of the resistant cross sections, this diminution becomes inappreciable in the case of brittle ebonites. On the other hand, the shape of the notch in ebonites containing no loading ingredients does influence the resilience. With V-shaped notches, the depth of the notch and its angle of aperture influence considerably the resilience of this latter type of ebonite, and notches of minimum depth are sufficient to have an appreciable effect.
Studies of Hard Rubber Reactions. III. Changes in Acetone-Extractable Substances during Vulcanization
Authors: Numajiri Seiiti
Published: February 2011

1. To explain chemically the fundamental hard rubber reactions which take place during the vulcanization, changes in the acetone-extractable substances, as well as in tensile strength, elongation, and hardness, during vulcanization were studied. 2. Preliminary experiments on acetone extraction with the author's apparatus indicated that a 20-hour extraction was ideal for the purposes of the investigation, and extractions extending to extremely long periods were unsuitable in the present experiments. 3. The corrected acetone extract or organic acetone-soluble substances do not either increase or diminish steadily throughout vulcanization, but show a maximum value at a definite period of vulcanization. The appearance of this maximum value, which also corresponds to characteristic changes in tensile strength, elongation, and hardness (cf. the preceding Communication) is a turning point where the hard rubber reaction diminishes rapidly. 4. To explain chemically the appearance of a maximum value and consequent increase and decrease in the percentage of acetone-soluble substances (corrected) it may be considered that the rubber or rubber compounds with different degrees of vulcanization are polymerized at a certain period of vulcanization, depending on the action of heat, accelerators and agencies, and that the amount of acetone-soluble substances is governed by these factors.
Studies of Hard Rubber Reactions
Authors: Numajiri Seiiti
Published: February 2011

As shown in Fig. 1, all the compounds containing 5 to 150 per cent of sulfur (based on the rubber) indicated a gradual loss of total sulfur, with a relatively rapid loss after about 90 minutes, which corresponds to the period of the hard rubber reaction. Some investigators hold the view that the loss of total sulfur is the result of liberation of hydrogen sulfide by the interaction of sulfur with rubber, resins, and proteins, and sublimation of sulfur. In the present experiments, the cause of the comparatively marked loss of total sulfur seems to be related to the hardening or polymerization reaction in hard rubber. No good mixture could be obtained from which the maximum loss of total sulfur was reached, with reference to the content of rubber, i. e., rubber resins, proteins, and that of sulfur. The loss of sulfur by sublimation was restricted as far as possible by enveloping the samples with cellophane. It appears from these facts that the depolymerization phenomena of soft or semi-hard rubber products may occur during the initial stage of vulcanization and those of the hard rubber after 90 minutes. Considering again the vulcanization curves in the previous report (Part IV), there is no loss of sulfur in the initial stage of vulcanization but considerable losses of sulfur are seen in the present curves of total sulfur; in other words, during the whole course of vulcanization the combined sulfur increases to a certain extent, accompanying the loss of sulfur on one side. In Fig. 2, the relationship between the loss of total sulfur and the tensile strength of the hard rubber product is shown. Of all the hard rubber compounds, the samples containing 70–80 per cent of sulfur showed the maximum loss of sulfur, coinciding with the maximum tensile strength after vulcanization for 90 minutes. It may be assumed that the polymerization and the depolymerization reactions occur simultaneously and are closely related.
Expanded Chlorinated Rubber
Authors: Schidrowitz P. , Redfarn C. A.
Published: February 2011

In a previous publication (J. Soc. Chem. Ind., 54, 263T–267T (1935); Rubber Chem. and Tech., 8, 613 (1935)) some particulars were given regarding the production and development of a hard spongy material from chlorinated rubber (British Patent No. 424,561). Thermal and Electrical Properties Some preliminary tests on the thermal and electrical properties of the material have now been carried out, and these serve to confirm the view that expanded chlorinated rubber should prove to be a very good insulating material. Thermal Conductivity.—The details given herewith are taken from a report by the Research Association of British Rubber Manufacturers. The thermal conductivity was determined by comparison with cork, a good insulating material of which the thermal properties are fairly well known. The method used consisted in placing slabs of cellular rubber and of cork each between a pair of aluminum plates, and then interposing between the two sets of plates an electric heating plate made of wire enclosed between sheets of mica. The plates, heater, and sheets of expanded chlorinated rubber material and cork were all of the same size, namely, 20.3 by 10.25 cm. The aluminum plates were 0.625 cm. thick.