bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composition and Colloidal Properties of Balata Latex
Authors: Kemp A. R. 
Published: February 2011

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.