bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Structure of Vulcanized Rubber
Authors: Brown J. R. , Hauser E. A.
Published: February 2011

A CENTURY ago, Charles Goodyear in America and Th. Hancock in England found that the properties of crude rubber could be greatly improved by heating it with sulfur. The product resulting was more elastic, more resistant to tear and abrasion, less affected by solvents, and decidedly less thermoplastic. The treatment of rubber to give these desired properties is known generally as vulcanization and must be considered as the basis for the enormous growth of the rubber industry and the extensive use of rubber products in our everyday life. Broadly speaking, vulcanization involves the reaction, in some fashion, of sulfur with rubber. Extensive investigation has revealed other substances, such as benzoyl peroxide or polynitrobenzenes, which can transform rubber into a “vulcanized” condition. Experience has also shown that metallic salts of zinc or lead and especially certain organic compounds called “accelerators” greatly affect the rate of vulcanization, and these are favorably employed in practice. A vast amount of empirical knowledge has been gained which has greatly improved the practical application of vulcanization and the quality of rubber products, but which has failed as yet to reveal a complete picture of the true nature of the process.
The Permeability of Organic Substances to Water
Authors: Badum E.
Published: February 2011

Although organic substances are in the ordinary sense regarded as waterproof, actually they are somewhat permeable to water vapor, and this permeability is sufficient to render them inapplicable as covering or sheathing for cables. In view of this, it was decided to study in a quantitative way the phenomenon of permeability to water of organic substances. The method chosen for making these measurements and the results obtained are described in a brief way in the following paragraphs. The first measurements were made with an apparatus which consisted of a hemispherical bell jar, the open part of which was carefully sealed by a sheet of the substance to be tested. To this bell jar was attached, by a ground-glass connection, a tube which could be closed by a stopcock, and which contained phosphorous pentoxide. In this way the vapor pressure of water within the bell jar was maintained at zero. The small apparatus was suspended in a constant-temperature chamber saturated with water vapor. The increase in weight of the weighing tube containing the phosphorous pentoxide was a measure of the amount of water which diffused through the sheet being tested.
Mastication of Rubber a Study of Some of the Oxidation Rocesses Involved
Authors: Busse W. F. , Cunningham E. N.
Published: February 2011

The rate of breakdown of smoked sheet, pale crepe, and sprayed-latex rubber in a laboratory internal mixer is a minimum at temperatures around 240° F., and the rate may be increased as much as four- or five-fold by either raising or lowering the temperature 80° F. The high-temperature reaction (above 240° F.) probably is similar to the thermal oxidation which occurs when rubber is heated in air, since the rates of both reactions are increased by increasing the oxygen concentration, and they are reduced by adding antioxidants. The low-temperature reaction (below 240° F.) may involve a mechanical acti-vation of the rubber, as in milling. The rate of this reaction first increases and then remains constant or decreases slightly as the oxygen concentration in the temperature during mastication is increased from about 0.5% to 20% to 100%. Some nitroso compounds are powerful stiffeners of rubber, and they change the softness-retentivity relation, making it more like that of reclaim or semi-vulcanized rubber. The effect of most commonly used “softeners” on the plasticity of rubber is small compared with the effect of changing the mastication temperature ±40° F. Exceptions to this are certain vulcanization accelerators (at high temperatures), hydrazine compounds and thiophenols, which appear to be true mastication acelerators or oxidation catalysts.
A Relationship between the Critical Oxidation Potentials and Antioxidant Activities of Rubber Antioxidants
Authors: Doede C. M.
Published: February 2011

1. According to the data presented, all of the compounds tested which exhibit marked antioxidant activity have an Ec value between 0.65 volt and 0.90 volt. Many substances exist which have an Ec value within the optimum range, but do not have much antioxidant activity. The condition that the Ec value for a good antioxidant falls between 0.65 volt and 0.90 volt seems to be necessary but not sufficient. 2. A value of Ec within an optimum range seems to be only one of several possible physico-chemical phenomena which govern the rubber antioxidant activity of a compound. 3. The determination of the Ec value of a compound should not be used as the sole criterion of that compound's antioxidant activity.
Dielectric Measurements in the Study of Carbon Black and Zinc Oxide Dispersion in Rubber
Authors: Kemp A. R. , Herrmann D. B.
Published: February 2011

The dielectric constant, power factor, conductivity and d.c. resistivity of rubber compounds containing various types and quantities of zinc oxide and carbon pigments have been measured. It has been shown that the dielectric properties of rubber compounds having high loadings of zinc oxide depend on the particle size and purity of the zinc oxide used. The French process oxides with the smallest particle size were found superior to other grades. Water-soluble impurities in zinc oxide are shown to have a deleterious effect on dielectric properties, especially in the presence of moisture. The effect on dielectric properties of adding carbon black to a rubber compound has been shown to be dependent on the type and amount of black added, and on the nature of its dispersion in the rubber. The dielectric properties of rubber compounds containing “soft” black made by the thermal decomposition process are shown to be distinctly superior to, and widely different from, those of the same compounds containing equal amounts of channel process black. The general conclusion has been reached that the smaller the particle size and the better the dispersion of carbon pigments in the rubber, the greater will be the increase in the dielectric constant and conductivity, and the greater will be the decrease in resistivity.
The Testing of Rubber at Low Temperatures
Authors: Carrington J. H.
Published: February 2011

Developments in modern compounding have in the last few years undoubtedly improved the general properties of vulcanized rubber. Ever-widening fields of application of rubber goods have extended the range of temperature over which rubber is expected to retain its properties. The search for rubber compounds that shall have greater resistance to oxidation, heat, oil and so forth has certainly been pushed forward with great success, but progress in the other direction, namely, towards rubber compounds resistant to extreme cold, does not appear to have been so rapid. In this country we do not experience the extreme cold which occurs in the upper atmosphere and in regions nearer the poles, but rubber suspension systems, etc., as used in ships in polar latitudes or vessels transporting foodstuffs, railway components of many kinds and the numerous rubber parts used in the construction of aircraft all suffer to some extent from loss of resilience when exposed to cold conditions. It therefore seems just as necessary to compound with a view to resisting changes induced by freezing as we normally do to resist heat. With this end in view it was decided to make a critical review of published data on the effect of low temperatures on rubber to serve as a guide to further practical work. As is to be expected, those countries experiencing great cold have already carried out considerable investigation, but the available information is fairly widely distributed, and no doubt there is much work of a private nature which has never been published. It will be convenient, in the summary which follows, to indicate the most important information under headings relating to the chief properties of rubber. As is so frequently the case, physical results have been obtained on mixings of unstated composition or state of vulcanization, or on mixings that are simple, no doubt, from the theoretical standpoint but almost unusual from the practical point of view.
Some Properties of Two Vulcanized Pure Gum Compounds at Low Temperatures
Authors: Somerville A. A.
Published: February 2011

(1) High and normal sulfur pure gum compounds became board-like and brittle within a few minutes when cooled at −60° C, yet when tested at this temperature they had an elongation of over 500% and tensile strength of over 5,000 lbs. per sq. in. (2) With decreasing temperature the two compounds gave increasing tensile strength and modulus and decreasing elongation. (3) Relatively high combined sulfur, i. e., up to over 8% on the rubber, was accompanied by a marked increase in hardness, even at temperatures no lower than −30° C. (4) A substitution of deproteinized rubber for smoked sheet appeared to give greater resistance to hardening at temperatures down to −40° C. (5) Unvulcanized, unmilled smoked sheet showed greater resistance to hardening on rapid cooling than the vulcanized compounds at all temperatures tested. This phenomenon, however, is not to be confused with that of ordinary frozen rubber, which is commonly observed at temperatures above −30° C.
Static and Dynamic Properties of Rubber under Compression
Authors: Kosten C. W.
Published: February 2011

Rubber undoubtedly possesses a number of unique properties which make it a particularly suitable accessory material for constructional purposes; e. g., in elastic mountings, elastic couplings and dampers against torsional vibration on driving shafts. Its application to such uses, however, requires knowledge of other than the usual properties. Most of these are related to simple physical quantities such as modulus at a given elongation, hysteresis, permanent set and the like. In § 2 will be discussed magnitudes that may be entailed in the cases in question. Relations existing between the various magnitudes will come up for consideration in the course of the discussion. Most of the problems involved have already received some attention. Some of the more important investigations into this subject will be dealt with in § 3. Finally, the results of experimental work on the static and dynamic behavior of rubber under compression will be recorded in § 4.
Dynamic Evaluation of Damping and Durability of Rubber Compounds
Authors: Roelig H.
Published: February 2011

The method described in this paper makes possible the dynamic evaluation of rubber and rubber-like compounds. It allows the measuring of the dynamic damping (hysteresis) loop during the fatigue test, and may be applied not only to small rubber samples but to larger objects such as vibration absorbers and whole tires. The apparatus renders valuable service in developing compounds of natural and synthetic rubber that undergo dynamic stress.
The Use of the Pendulum in Rubber Testing
Authors: Jones F. B. , Pearce W. H.
Published: February 2011

During the past few years considerable interest has been shown in the use of pendulum methods for the study of resilience properties of rubber compounds. We feel therefore that an account of the development and use of the pendulum method in the Dunlop Rubber Co.'s laboratories will prove of general use. In this country the period from 1918 witnessed a rapid extension in road transport, carried at that time almost exclusively on solid tires. With this development the performance of heavy vehicles improved considerably and tires were operated under the increasingly severe conditions, both with respect to speed and load. It is well known, that if a solid tire is operated under sufficiently severe conditions it is no longer able to dissipate the heat developed within it, and its temperature rises until eventually an explosion or the familiar “blow-out” occurs. This phenomenon, of course, results from the fact that rubber is not perfectly elastic. When transmitting energy it does not release all the energy supplied to it. Some of the energy is always absorbed and appears in the rubber in the form of heat; the faster the energy is supplied, the greater is the increase in temperature.
Composition and Colloidal Properties of Balata Latex
Authors: Kemp A. R.
Published: February 2011

This paper reports the composition and colloidal properties of two types of balata latex from Dutch Guiana. The white variety is shown to be superior to the red, owing to its higher content of hydrocarbon. It is shown that balata latex is very stable due to the presence of a highly protective water-soluble substance in its serum. It cannot be coagulated by acids or salts but is readily coagulated by alcohol or acetone. The balata latex particles are spherical and vary in diameter from about 0.1 to 2.5 microns with an average diameter of about 0.5 micron. The balata latex particles are shown to enclose the resins, which appear to be present in a dispersed state in the hydrocarbon. The particles are shown to contain about 18% of water, determined as water of retention in pressed coagulum. The “resins” have been separated from both types of balata latex as water-white viscous liquids, which deposit crystals of β-amyrin acetate on standing. The red balata latex resin is shown to be more viscous than the white and to differ from it as regards its iodine value, refractive index and solubility in cold 95% ethyl alcohol. The serum components have been separated into four main fractions: protein, carbohydrate, gummy substance and ash. Minor components such as tannin and amino acid have also been noted. A complete analysis of balata ash has been made and compared with the analysis of ash from Hevea latex by Bruce. Balata ash was found to contain higher contents of CaO, Na2O, and MgO and lower contents of K2O and P2O6 than Hevea latex ash. New data are presented on the density, refractive index, dielectric constant and heat of combustion of balata hydrocarbon which are believed to be more reliable than similar data previously available in the literature. Data on the effect of temperature on the refractive index of balata and gutta-percha hydrocarbons are presented, showing the crystallization of the gutta hydrocarbon on cooling, which starts at about 37° C. resulting in an abrupt increase in refractive index occurring between 37° and 35° C.
A Time Effect in the Rapid Elongation of Rubber
Authors: Hauk V. , Neumann W.
Published: February 2011

It has already been pointed out elsewhere (Monatshefte für Chemie 72, 32 (1938); Rubber Chem. Tech. 12, 64(1939)) that the difference between the adiabatic and isothermal stress-strain curves of rubber is too great to be explained on a thermodynamic basis alone. It was suggested that the position of the adiabatic curves might be governed by the fact that the rate of stretching itself has a decisive effect on the behavior of the chains of molecules during stretching. To throw light on this phenomenon, stress-strain curves were obtained, by means of the stretching apparatus already described in the paper mentioned, at various rates of elongation which still fell within the range of adiabatic stretching. The operation was carried out in such a way that a chronometer started electrically when the rubber began to elongate, and stopped again when the rubber reached an elongation of 450 per cent. With the aid of this contrivance, stress-strain curves were obtained at rates corresponding to 0.68, 2.5, 5.7 and 9.1 seconds' elapsed time for the stretching. For comparison, an isotherm was obtained by loading rubber strips of the same dimensions with various weights. A vulcanizate containing 2 per cent of combined sulfur was used as experimental material. The temperature was 13° C. The results of these measurements are shown graphically in Fig. 1. It may be seen that the adiabatic curve corresponding to the highest rate of elongation has the least steep ascent, i.e., at the highest rate of elongation the stress is greatest at a given elongation. With increase in the time of stretching, the curves approach nearer and nearer to the isothermal stress-strain curve. This would seem to prove that the rate of elongation plays an important part, wholly independent of any thermodynamic effects. Perhaps during rapid stretching there is actual rupture of chains which are still coiled and which mutually obstruct the smooth course of the stress-strain curve. It can also be seen from the position of the curves that the decisive effect shown by the time factor is of the order of seconds, since the difference between the curves corresponding to 0.68 and 2.5 seconds is very small, whereas the difference between the curves corresponding to 2.5 and 5.7 seconds appears to be considerable.
Some Practical Aspects of the Theory of Diffusion of Water through Rubber
Authors: Daynes H. A.
Published: February 2011

PRACTICAL FIELD OF INTEREST OF THE SUBJECT The rate of passage of moisture through rubber and the amount absorbed by it are of practical importance in the production and applications of the material, as illustrated by the following examples: (1) In the preparation of raw rubber, the rate of drying is one of the important factors in production cost. (2) In electrical signalling cables, the demand for low dielectric constant and power factor, which are adversely affected by absorbed moisture, is becoming more severe with the increase in audio and carrier frequency transmission. The rapid increase in the last few years in the use of Paragutta, which contains deproteinized rubber, in place of gutta-percha in submarine cables is evidence of the value of the purification of rubber for such purposes. (3) The absorption of water by the rubber insulation of lighting and power cables has led to serious trouble under certain conditions which arise in modern buildings. (4) The power factor of ebonite to be used at radio-frequencies is very sensitive to slight traces of moisture. (5) The rapid removal of water is important in most processes for the production of articles directly from rubber latex. (6) The swelling and loss of mechanical strength due to absorbed water are objectionable, for example, in many mechanical goods, steam packings and hot-water bottles. (7) The diffusion of moisture through thin films has received attention recently in connection with packaging materials and other thin films.
Vulcanization of Oxidized Rubbers
Authors: Stevens H. P. , Popham F. J. W.
Published: February 2011

All three fractions of Rubbone, A, B and C, can be vulcanized by heating with sulfur to yield hard rubber-like products containing, respectively, a maximum of 32.8%, 24.5% and 22.6% of sulfur in combination. As the unchanged Rubbone in a Rubbone vulcanizate can be extracted with appropriate solvents, the course of the reaction can be followed in greater detail than the vulcanization of rubber. The theoretical degree of unsaturation of the three fractions, A, B and C, taking rubber = 100, are 75%, 50% and nil. The figures based on combined sulfur are 70%, 52% and 48%, and based on iodine absorption are 90%, 75% and 51%. This work has been carried out on behalf of the Rubber Producers' Research Association, to whom the authors are indebted for permission to publish this paper.
The KOH-Number Test and Its Application to the Compounding of Zinc Oxide in Rubber Latex
Authors: Jordan H. F.
Published: February 2011

1. From measurements of the cataphoretic mobility of latex particles in potassium and calcium buffers, respectively, it has been calculated that in order to obtain high stability in latex compounds, the concentration of divalent ions must be of the order of 0.002 M or less. 2. Measurements of the cataphoretic mobility of latex particles suspended in solutions of constant zinc and ammonia concentrations indicate that in the presence of dissolved zinc oxide the stability of latex is increased with increasing pH above pH 9.6. This is attributed to conversion of divalent zinc ammonia ion (Zn(NH3)4++) into monovalent zinc ammonia hydroxide ion (Zn(NH3)3OH+). 3. A consideration of the mass action equations for zinc hydroxide and zinc ammonia hydroxide shows that the concentration of divalent zinc ion decreases rapidly as the ammonia concentration is reduced or as the pH is increased. 4. The EOH number of latex is defined as the number of grams of KOH per 100 grams of rubber corresponding to the end point (at pH 10.7–11) in the electrometric titration of latex with KOH. Experimental precautions in determining the KOH number are discussed. 5. Data are given which show that the KOH number of a normal latex may be reduced more than tenfold by creaming three times from 33% T.S. to 62% T.S. 6. The KOH numbers of commercially available normal latices have been found to vary between 1.2 and 2.4, and those of creamed or centrifuged latices between 0.55 and 0.95. 7. The amount of KOH for optimum stabilization (i.e., maximum stability, minimum viscosity and minimum change of properties with time) of zinc oxide compounds containing no added buffering ingredients varies with the latex, and is numerically equal to the KOH number. This quantity of KOH produces a pH of 10.7–11.0. 8. If appreciable amounts of protective ingredients such as casein, glue or gum arabic are added in compounding, sufficient additional KOH must be added to maintain a pH of 10.7–11 in the latex compound. The amounts of KOH required may be determined by electrometric titration of the protective ingredients.
The Viscosity of Preserved and Concentrated Latex. Part I. Relationships between Dry Rubber Content and Viscosity
Authors: Rhodes Edgar
Published: February 2011

The viscosity-temperature relationships for normal preserved latex, centrifugal concentrate and aqueous dilutions of such concentrates have been determined on a few samples. The results obtained suggest a basis for the calculation of approximate comparative viscosities for normal preserved latex and centrifugal concentrate at different temperatures. From the viscosity curves for rising and falling temperatures on normal preserved latex and centrifugal concentrate, it appears that normal latex can be heated for several hours at 80° C without seriously affecting the state of dispersion. There are indications, however, that with rich concentrates, heating does affect the state of dispersion slightly.
Ficus Elastica and Castilloa Latices
Authors: Stevens Henry P.
Published: February 2011

Although for all intents and purposes the Hevea Brasiliensis or Para rubber tree is the only rubber-yielding tree at present cultivated, this was not always the case. Today the words rubber and latex are almost synonymous with Para rubber and Para latex, but there was a time when rubber from other sources was available and the quality of commercial raw rubber showed very large variations. HEVEA LATEX AN EXCEPTIONAL TYPE Owing to the present predominance of rubber from Hevea Brasiliensis, almost all chemical investigations have been concentrated on the latex from this tree and the rubber therefrom, and a position has been reached which tends to the assumption that Hevea latex and rubber are the normal types, while others are abnormal. Thus, as is well known, Hevea latex is readily coagulated by a very small addition of an electrolyte and coagulates spontaneously in the country of origin in about 12 or 14 hours unless an antiseptic or preservative be added. It is therefore assumed that a latex which is not readily coagulated by electrolytes or does not coagulate spontaneously is abnormal whereas as a fact, the reverse is the case. If an examination is made of latices of other botanical origin, rich in hydrocarbon, it will be found that the best known of these are not coagulated either spontaneously or with the aid of electrolytes. Consequently it may be concluded that Hevea latex is exceptional and abnormal. Unfortunately much of the data in regard to other latices is scanty and unreliable. Only in a few instances have we the records of trained chemists. Most of the information is based on statements of observers without scientific training or at least without adequate chemical experience. Therefore any contribution to our knowledge of latices other than that of Hevea is very welcome.
Testing and Control of Latex Supplies
Authors: Murphy E. A.
Published: February 2011

In recent years the employment of latex for a wide range of purposes has increased rapidly and the business of producing it in suitable forms on the market has become of considerable importance in the rubber-producing countries. Consumers of latex have for some time realized the necessity of obtaining uniformity in their supplies—in many applications a much higher degree of uniformity is required for economical working than is called for in supplies of pale crepe or smoked sheet. In addition to the control of properties such as uniformity in rate of vulcanization, good aging, and absence of foreign matter, ordinarily required in supplies of the best grade of raw rubber, there are the problems of maintaining uniform concentration, stability, color, freedom from coagulum and absence of offensive odor. In some applications uniformity in the behavior of the latex under given conditions of compounding and coagulation is also required. The general procedure observed in the collection, preservation and concentration of latex, together with a description of the various types of latex available, has already been given in the literature. It is proposed in this paper to review some of the tests that have been employed in evaluating and controlling latex supplies. An attempt will also be made to show the relative values of these tests in determining the suitability of latex supplies for different uses.
Relations between Vulcanization and Reinforcement
Authors: Park C. R.
Published: February 2011

1. It seems unlikely that the effects of vulcanization are due to reinforcement produced by discrete rubber sulfide particles and due to their fineness and state of dispersion. 2. There seems to be some indication that the changes which result from the introduction of finely divided powder are due to oxidation of the rubber hydrocarbon. The final products, both chemically and physically, are analogous to rubber-sulfur compounds. 3. The peculiar behavior of zinc oxide when added to rubber-sulfur mixes indicates that this material reacts during vulcanization and produces reinforcing effects of a magnitude not to be explained by its particle size and not dependent on the presence of added organic accelerator. 4. The latest information regarding effect of powders upon rate of vulcanization indicates that differences among powders in this respect are due to differences in adsorption. These latter differences result from the nature of the powder surface, which affects adsorptive power in such a way as to make its action preferential to certain constituents in the mix.
Notes on the Method of Roberts for the Analysis of Raw Rubber
Authors: Kraay G. M. , Altman R. F. A.
Published: February 2011

1. When using the method of Roberts, it is necessary to work in an atmosphere of nitrogen and with solvents free of peroxides, at least in the first phase of separation. 2. The product isolated by Roberts, which has been named by him “caoutchol”, is an oxidation product of rubber hydrocarbon. 3. The “modified” method of Roberts, i.e., working under nitrogen, must not be used as a quantitative method when there is a great variation in the “caoutchol” content of the rubber. 4. The results depend on the temperature at which the analysis is carried out. 5. When used with exclusion of oxidation, the method of Roberts may prove to be a means of detecting oxidation products in raw rubber.
Neoprene Cements
Authors: Starkweather Howard W. , Wagner Frederick C.
Published: February 2011

Data are presented regarding the viscosity and stability of Neoprene cements in benzene containing up to 30 per cent total solids. Although the more concentrated cements have only limited stability, especially at elevated temperatures, those up to 15 per cent concentration are sufficiently stable for practical purposes. Cements made from Neoprene Type G are slightly less stable than those made from Neoprene Type E, but up to 17 per cent concentration are still usable after 5-month storage at room temperature. Compounding somewhat reduced the stability of concentrated cements. The addition of sodium thiosulfate during compounding improves the stability of Neoprene Type E cements. Diphenylguanidine lowers the viscosity of Neoprene Type G cements but renders them slightly less stable. The viscosity of cements for any given solvent or concentration varies with the plasticity of the Neoprene. The variation of the intrinsic viscosity determined in different solvents makes the calculations of molecular weights from this type of data extremely uncertain.
Report of the Crude Rubber Committee. Presented before the Division of Rubber Chemistry at the Semi-Annual Meeting of the American Chemical Society, April 11, 1940
Authors: Sackett G. A. , McColm E. M. , Nellen A. H. , Oldham E. W. , Parrish R. D. , Schatzel R. D. , Walton J. C.
Published: February 2011

The Crude Rubber Committee presents this report with the hope that all members of the Division of Rubber Chemistry will consider with serious attention all the points covered, and if anyone wishes to offer suggestions, comments or criticisms, he should do so by writing directly to the Chairman or any of the Committee members. The same applies to questions on any of the items. The Committee is particularly anxious to have comments on procedures already offered, including the test for foreign material described above. The task of drawing up tests or procedures for use by all technologists interested in crude rubber is not an easy one, and although every effort is made to draw up these procedures so that they will be of general utility, without the interest and help of many members, the Committee can neither accomplish the best results nor fully achieve its purpose. Much remains to be done, but with the continued coöperation of the officers and members of the Division, the tasks will be accomplished.
New Types of Transformation Products of Rubber
Authors: Mark H. , Posnansky K. W.
Published: February 2011

In the present paper, a few observations are described which were made in the last few months by Philipp and one of the present authors (Posnansky). When a solution of silver nitrate in a mixture of acetone and water, which is a satisfactory solvent for silver nitrate and at the same time has a sufficiently strong swelling action, is allowed to react with crude rubber in the form of films prepared from latex, products are obtained whose properties depend on the concentration of the solution, on the time of reaction and on the temperature, and differ fundamentally from the properties of the original rubber. When highly purified latex is used for preparing the films, the already familiar reducing action of rubber on silver nitrate does not take place, and colorless or white films are obtained, within which considerable quantities of inorganic substances are embedded. Determinations of the silver contents of these products showed values up to 18 per cent of silver, corresponding to approximately 37 per cent of silver nitrate, the actual percentage depending on the time that the reaction was allowed to continue. That a very strong addition reaction takes place becomes evident, for example, by the fact that when a similar latex film is swollen in a silver perchlorate solution of the same concentration, only 2.5 per cent of silver, i. e., less than one-seventh as much as with silver nitrate, was found in the end product, which, moreover, gave no indication that any fundamental changes had taken place, such as are described below for the reaction between rubber and silver nitrate.
Rubberlike Properties of Polybutene
Authors: Sparks W. J. , Lightbown I. E. , Turner L. B. , Frolich P. K. , Klebsattel C. A.
Published: February 2011

Until the last decade the explanation of those properties for which rubber is unique was confined largely to the study of rubber itself. Duplication of these properties involved the synthesis of polymers from isoprene and its immediate homologs. The discovery that chloroprene could be polymerized to a rubberlike substance altered the character of the study and represented a distinct departure in the type of diolefin used. The production of Thiokol, phosphonitrile, and the various vinyl polymers has resulted in the duplication of certain rubberlike physical properties by chemical structures wholly unrelated to rubber. Observation of the behavior of these newer elastics must lead to the conclusion that many physical characteristics of rubber are not inherent in the conformation of the rubber molecule alone. Whitby suggested that any general view of the structure of rubber can be regarded as acceptable only if it is applicable to other elastic colloids. Conversely, those properties of rubber which are not shared by other elastics must be explained by structural features not common to them all. A logical product to consider for the segregation of properties relating to the rubber structure per se and those capable of being shared by other molecules is hydrorubber. This substance has been observed to have certain “rubbery” properties, but unfortunately for comparison it has been prepared only in a degraded or low molecular weight form and therefore (from the standpoint of physical state) is not directly comparable with rubber.
Practical Evaluation of Commercial Rubber Carbon Blacks by X-Ray Diffraction
Authors: Clark George L. , Rhodes Herbert D.
Published: February 2011

Of the dozen or more reinforcing agents used in the commercial compounding of rubber, carbon blacks are outstanding in their excellence. Though no completely satisfactory theory has yet been forthcoming to explain the action of this material, the literature indicates that, among other factors, the size and shape of the ultimate carbon particles profoundly affect the characteristics of the rubber products obtained. Particle sizes of fillers and pigments are commonly determined by microscopic methods. Of those that have been suggested, the method of Gehman and Morris is perhaps most widely accepted as reliable. All microscopic methods, however, are subject to the limitation of resolving power imposed by the relatively narrow range of wave lengths in the visible and near ultraviolet which can be used for viewing and photographic purposes. Further, no distinction can be drawn between ultimate particles and compact secondary aggregates from the microscopic point of view. Thus, there always exista the possibility that microscopic particle sizes represent groups of individual particles rather than the individuals themselves.
The Effect of Silent Electric Discharges on Rubber Solutions
Authors: Hock Lothar , Leber Heinrich
Published: February 2011

The object of the investigation was to synthesize higher molecular compounds from natural rubber and from synthetic rubber by means of a process involving exposure to silent electric discharges. With both natural rubber and synthetic rubber, it was found possible to bring about polymerization by this method and to obtain polymers of various molecular sizes, which could be separated into two principal types: (1) polymers which remained soluble in benzene, and (2) polymers with a highly developed network structure, which were insoluble in benzene and therefore could be separated from the soluble polymers. After purification and drying, the insoluble polymers were obtained as inelastic, nonplastic products, in the form of soft, crumbly flakes. On the contrary, the soluble polymers retained the plasticity and elasticity of the original rubber, and behaved like raw rubber in the technical sense as well. This latter fact was proved by preparing a few mixtures and vulcanizates from these polymers, and it is noteworthy that a vulcanizate prepared from polymerized Buna-85 more nearly resembled a corresponding vulcanizate from untreated natural rubber than it did a vulcanizate prepared from the original, untreated Buna-85. Of course more extensive development work would be necessary to obtain polymers with particularly desirable properties from a technical point of view, and to find out how to compound these new polymers, e. g., what types and percentages of fillers, accelerators, and percentages of sulfur to use. Only in this way can the technical importance of these products be judged, and can any uses to which they may be applied to advantage be determined. But whatever may be their importance, the increased molecular sizes of these polymers of natural rubber and of Buna-85 are accompanied by marked increases in softening temperature without sacrifice of their technically important advantages of plasticity, tackiness and solubility. To this extent a not unimportant goal from the technical point of view may be regarded as having already been attained.
Destructive Hydrogenation of High-Molecular-Weight Polymers. Isobutene Polymer, Butadiene Polymer, and Natural Rubber
Authors: Ipatieff Vladimir N. , Schaad Raymond E.
Published: February 2011

Destructive hydrogenation under pressure in the presence of nickel oxide and molybdenum oxide has been used to show the presence of naphthenic hydrocarbons in high-boiling olefin polymer. It was of interest to apply this tool to other hydrocarbons having large molecules, especially rubber and synthetic rubber like polymers. The destructive hydrogenation of isobutene polymer yielded only paraffinic hydrocarbons, including isobutane in the gases. Butadiene polymer, on the other hand, gave only naphthenic products, chiefly ethylcyclohexane and a dicyclic hydrocarbon. Similarly, natural rubber yielded only naphthenes, with p-methylisopropylcyclohexane as the major component of the lower boiling portion of the product. Isoprene, under the conditions used for the destructive hydrogenation of the rubber, yielded isopentane and an unsaturated naphthene, i. e., a hydropolymer of isoprene, which was converted into p-methylisopropylcyclohexane by further hydrogenation. Discussion of the relation of these results to the structures of the polymeric substances hydrogenated is reserved for a future publication of further work now in progress undertaken to aid in the proper interpretation of the above indicated experiments.
A Study of Polymers. I. Highly Elastic Deformation of Polymers
Authors: Aleksandrov A. P. , Lazurkin Yu S.
Published: February 2011

1. The proposed explanation of relaxation makes it possible to understand the general law of the dependence of deformation of highly elastic substances on temperature and frequency (time of action). 2. The results of measurements of various substances conform in a qualitative way to the scheme proposed. 3. With respect to mechanical losses, it is shown that application of the simple concept of relaxation makes it possible in many cases to explain the physical nature of the processes involved. 4. It is found that the relations characteristic of various relaxation processes, such as electrical and mechanical processes, are marked by a unity in their physical nature.
A Study of Polymers. II. Dynamic Method of Studying Elastic Materials
Authors: Lazurkin Yu S.
Published: February 2011

Most articles made from elastic substances are intended for service under dynamic conditions. Static methods of investigation are clearly insufficient for determining the behavior of elastic substances under dynamic conditions and therefore there has for a long time been a need for dynamic tests. In recent years several dynamic tests have been developed, and a number of investigations of elastic properties under dynamic conditions have been published. The works of Frumkin, Roelig, Kosten, Naunton and Waring and other investigators have established a series of relations in the behavior of elastic substances under dynamic conditions. However, the limited intervals of frequency and temperature in these experiments gave relations of peculiar character and even led to contradictions. Thus Naunton and Waring showed that, under dynamic conditions (at high frequencies), automobile tire casings act as solid hoops and, according to Roelig and Kosten, the relation between modulus and frequency, though still existing, is of relatively little importance. The development of a concept of the mechanism of highly elastic deformation, and in particular the disclosure of relaxation made it possible for Kornfel'd and Poznyak and Mikhai˘lov and Kirilina to demonstrate experimentally the existence of a more general law relating the phenomena. However, in their experiments, the frequency in both cases changed within narrow limits, and consequently these investigations too do not give a general picture of the behavior of elastic materials in relation to the frequency of deformation and temperature. The idea of highly elastic deformation, as well as that of relaxation, comes down to the fact that the magnitudes of the deformations observed depend on the relation between the time of action of the force and the time required for regrouping of the particles in the substance during the deformation.
Rheologic and Elastometric Measurements of Rubber Products
Authors: Höppler F.
Published: February 2011

A number of raw materials, intermediate products and finished products of the rubber industry were examined, and their rheologic and elastic properties measured by a Höppler consistometer. The initial measurements were carried out with concentrated solutions of rubber and artificial rubber, and flow curves were constructed to show their behavior at various temperatures. The results show that the thixotropic properties of these materials are independent of the temperature. Also flow curves of solid raw rubber products of various degrees of mastication and at various temperatures were constructed and the corresponding quasiviscosity and flow point values were determined. It was proved that the ηQ/t function has a logarithmically linear course and, based on this fact, a new material constant is derived. The elastic and plastic deformations of vulcanizates were studied experimentally on the basis of their resistance to deformation, and it is proposed that the hardness of hard-rubber products be measured and characterized by their cone flow points. All measurements are based on the c.g.s. system.
The Standardization of Rubber Flexing Tests
Authors: Stevens W. L.
Published: February 2011

The present paper offers a method for standardizing rubber breakdown tests which is an adaptation of discriminant function analysis recently developed by R. A. Fisher, and hitherto applied only to the treatment of biological data. The data which form the subject of the present study are rather inadequate, but it is worth while to use them to make the method available for more extensive investigations at a later date. It has, at least, revealed a gross lack of control in experimental technique, and shows that great improvements must be made on the practical side to give the new statistical method a chance to show its real sensitivity.
Machine and Methods for Testing Mechanical Stability of Latex
Authors: Novotny Chas K. , Jordan Wilbur F.
Published: February 2011

Methods and machines have been studied for making mechanical stability tests on latices. The results indicate that a constant-speed machine will give reproducible results at widely separated laboratories when test samples of fixed solids content are used.
Control of Gelling in Vulcanizing Cements. Nitroparaffins and Chloronitroparaffins as Inhibitors
Authors: Campbell A. W.
Published: February 2011

The broad application of ultraaccelerators to vulcanizing rubber cements has been handicapped by the formation of irreversible gels, presumably due to partial or complete vulcanization while in solution. The gelling tendency can be overcome by the use of so-called two-part cements, as illustrated in recipe I. Rubber, zinc oxide, and sulfur are mixed on the usual type of mill and then dissolved in a suitable solvent to form one part; rubber and accelerator or accelerators, with or without zinc oxide, and similarly mill-mixed, are dissolved in the same solvent to form the second part. Mixing these two parts in the proper proportions produces a cement containing all the necessary ingredients in the proper proportions for vulcanization. With ultraaccelerators, the mixed cement gels or vulcanizes within a period of hours or days, depending on the accelerator and the accelerator-sulfur ratio. The gel constitutes an economic loss. While two-part cements overcome this gelling, they are not economical of labor and space. It has been found that nitroparaffins and their derivatives will inhibit gelling of vulcanizing cements for long periods. Thus, with many accelerator-sulfur combinations it is possible to make direct mill mixes, followed immediately by churning in the solvent containing the antigel agent. This eliminates half of the mixing and churning usually necessary with ultraaccelerated cements, and permits any unused cement to be stored for use later.
The Molecular Weight and Constitution of Natural Rubber
Authors: Meyer Kurt H. , Wertheim M.
Published: February 2011

As is well known, crepe rubber is prepared from freshly gathered latex by the addition of dilute formic acid, and it contains natural rubber hydrocarbon in unaltered or but slightly altered form. Some years ago Meyer and Mark measured the osmotic pressure of crepe rubber in benzene. At that time the authors based their calculations on an equation derived from the hypothesis that the system was solvated. However, this deduction can no longer be considered valid, for rubber is not solvated in benzene or in toluene, as has been proved recently by Meyer, Wolff and Boissonnas by the fact that solution is accompanied by a slight absorption of heat. In view of this, these earlier results should be evaluated graphically so that the reduced osmotic pressures, p/c, are extrapolated to zero concentration (see Figure 1 and Table I). When evaluated in this way, the limiting value of p/c of 0.5 × 10−3 atmospheres, corresponding to a molecular weight of approximately 500,000, is obtained.