bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Quantitative Determination of Zinc in Transparent Rubber Articles
Authors: Casazza Edmondo 
Published: February 2011

Abstract
The method to be described is particularly suitable for the quantitative determination of zinc, present in the form of zinc oxide or of zinc salts, in transparent rubber articles. Rubber articles of this type contain very small quantities of zinc compared with the quantities present in non-transparent rubber articles, in fact the lower limit is only 0.05 per cent, i.e., only about one-hundredth as much as the normal content. The analytic determination of the zinc content when present in such extremely low percentages as this is extremely difficult by ordinary, methods, and even with higher but nevertheless small percentages of zinc, the use of relatively large quantities of material is necessary and the analytical results are often far from precise. The ordinary method of incineration in a porcelain crucible does not lend itself to the isolation of small quantities of zinc because the latter is easily fixed by the silica of the crucible. On the other hand incineration in a platinum crucible is not suitable because of the tendency of this metal to form a carbide in contact with the carbonaceous substances in the rubber. The novel feature of the method of analysis to be described is the procedure for obtaining a solution of the inorganic substances in the rubber. This involves destruction of the rubber by concentrated sulfuric acid and subsequent oxidation of the organic residue by concentrated nitric acid. This gives a solution of the zinc in the form of sulfate. It is then isolated as zinc sulfide and is redissolved and determined volumetrically by the already known method of precipitation with a standard solution of potassium ferrocyanide. The most suitable concentration, acidity and temperature to give precise results by this procedure for low percentages of zinc in rubber were established.
X-Ray Diffraction Patterns of Hevea, Manihot and Other Rubbers
Authors: Clark George L. , Gross Siegfried T. , Smith W. Harold 
Published: February 2011

Abstract
When rubber from Hevea brasiliensis is stretched quickly and exposed to a beam of x-rays, a crystal fiber diffraction pattern is obtained.” During previous work, done jointly by the National Bureau of Standards and the University of Illinois on sol and gel fractions of this rubber, no pattern was produced by the stretched sol fraction. With the stretched gel fraction, however, the pattern was sharp and intense. Rubber from Manihot glaziovii also may be separated into sol and gel fractions, and in recent work they, too, have been stretched and examined by x-rays. With the stretched Manihot sol, a few interferences were obtained, but many more resulted with the stretched gel. When crystallized by “freezing” at low temperatures for 24 hours, the interferences from the gel again outnumbered those from the sol. The x-ray measurements of Manihot rubber agree with those of Hevea rubber and indicate that the same structure exists in each. Rubbers obtained from latices of Funtumia elastica, Cryptostegia grandiflora and Castilla elastica were also examined. Their structures, too, were like that of Hevea rubber, and the similarity confirms earlier observations made when x-ray technique was less highly developed. In crystallized specimens, the crystals melted within the range of temperatures previously observed with Hevea rubber. In earlier work a large spacing was observed in a specimen of unstretched Hevea gel rubber. This spacing has been observed also in a new specimen of stretched Hevea gel rubber, together with a second spacing approximately twice as large.
The Joule Effect
Authors: Wiegand W. B. , Snyder J. W. 
Published: February 2011

Abstract
With reference to a paper by Gleichentheil and Neumann on “The Gough-Joule Effect in Vulcanizates,” we should like to call attention to the similarity between the results reported in their paper and the earlier work reported by Wiegand and Snyder entitled “The Rubber Pendulum, the Joule Effect and the Dynamic Stress-Strain Curve.” The latter authors analyzed from a thermodynamic point of view the rubber stress-strain curve as affected by temperature. As a result of this analysis the stress-strain curve was divided into three groups, Region A, Region B and Region C. Each region was characterized by different trends as regards the Joule effect and internal energy changes. The following description is taken from the original paper: “Region A, The Steel Spring.—This region, extending to approximately 300 per cent elongation for the conditions in the experiments described, is characterized by the comparative absence of heat transfers . … little or no Joule effect.” “Region B, The Gas (and the Crystal).—In region B the region of the Joule effect . … there is the maximum of heat evolution. It should be noted that Region B extends from approximately 300 per cent elongation to 700 per cent elongation. “Region C, The Friction Member.—This region is characterized by the almost entire absence of reversible effects. The Joule effect has disappeared. There is no evolution of heat….“
Vulcanization of Rubber
Authors: Fisher Harry L. 
Published: February 2011

Abstract
Charles Goodyear, a hundred years ago, saved the rubber industry and made available for human needs and satisfaction a material of unique and useful properties. In the 1830's the industry was in bad straits. People wanted its products, but unfortunately the rubber of which they were made became soft and sticky in summer and stiff and inelastic in winter, and also deteriorated rapidly. Through several years of all kinds of difficulties Goodyear persisted in his idea that he could find a method of preserving the good properties of crude rubber and finally discovered not only how to preserve but also how to enhance them. Sulfur and heat gave him his answer. Sulfur and heat also formed the basis of the name “vulcanization” by which the process has been known. It was given by Brockedon, a friend of Thomas Hancock, who was the famous English pioneer in the rubber industry, a contemporary of Goodyear, and rediscoverer of the method of vulcanization. Goodyear's method was the result of much painstaking effort, although as with all important discoveries it really is quite simple. He knew nothing of and was not required to use organic accelerators, accelerator activators, accelerator retarders, antioxidants, antiflex-cracking agents, reinforcing materials, reclaim, plasticizers, stiffeners, odorants, blowing agents, rubber substitutes, etc. However, he had plenty of headaches in getting his process into action, not only from the technical but also from the business angle. People were disgusted with rubber products and the companies which manufactured them, and he had to overcome much prejudice and antagonism. His process has an unusual record since, even now, a century afterwards, it is still the basis of the rubber industry. This statement does not mean that there have been no advances. The very length of the list of different types of materials given above for use with sulfur in rubber indicates the extent of some of the technical advances which have been made. Also, other important advances have been made in the apparatus used in the factory and in the methods of testing the products. Goodyear tacked his sheets of rubber on the outside of his house or hung his products from the rafters of a barn to find out the effect of cold and heat. Later men used their teeth and trained their bite to gage and compare tensile strengths. But these simple and useful methods have long since been displaced by the accurate methods of the modern testing laboratory, which produce results that can be evaluated by anyone skilled in rubber work.
The Lattice of Rubber
Authors: Misch Lore C. , Van Der Wyk A. J. A. 
Published: February 2011

Abstract
The lattice of rubber has already been the subject of a number of investigations. All the unit cells suggested in these papers give an x-ray density which is far higher than the measured one (8–10 per cent). Furthermore, in all Weissenberg pictures published, it is striking that the equator reflection A2 is much longer than A1 and A3. We believe therefore that A2 is not a single reflection and that the angle between A1 and A2 is not 90° or nearly 90°. While we investigated this question experimentally, Morss published a paper, also assuming that A2 is a double reflection and making the assumption of double orientation. He calculated the unit cell for a number of angles and found an agreement with the observations at the angle of 70.5°. The cell contains 8 chains.
The Action of Ozone in the Phenomenon of the Cracking of Rubber Subjected to Repeated Mechanical Stresses
Authors: Eccher Silvio 
Published: February 2011

Abstract
Various rubber articles are subjected in ordinary service to repeated stretching, compression and cutting and to combinations of such forces. Repeated flexing is frequently encountered also. All these forces cause repeated changes, either positive or negative, in the dimensions of the outside surface of the rubber article. Among the important rubber products which undergo such stresses are tires, belts and shoe soles. The stresses to which the tread of a tire is subjected are certainly complex and variable. In this particular case, there are, in addition to the initial static tension, forces of compression, flexing and torsion. A rubber belt offers a simpler problem, for in this case it is possible to distinguish the following cycle of changes on the outside surface: a constant elongation in the taut section of the belt; a sudden increase in elongation on passing over the driving pulley, during which time a constant flexing stress (which depends on the curvature of the pulley) must be added to the tension on the belt; a decreased elongation along the surface of the belt in contact with the pulley; and finally a rapid return to the minimum value existing in the belt when under no tension. An analogous cycle of changes takes place at the driven pulley. Each element of the surface of a belt undergoes, therefore, during each complete revolution, two periods of tension, between which the element is alternately in the taut and in the slack section of the belt.
Studies of Hard Rubber Reactions. VI. Liberation of So-Called Free Sulfur and Changes in the Acetone Extract of Vulcanized Rubber by Repeated Extraction and Heating
Authors: Numaziri Seiiti 
Published: February 2011

Abstract
1. True Free Sulfur.—In the case of the pure rubber-sulfur compound, as shown in the graph, the quantity of true free sulfur liberated from the thermally active hard rubber product by 120 minutes' cure was generally a little greater than that from the thermally nonactive sample with 300 minutes' cure. During the whole course of the extraction and heating, there occurs a lowest point in the true free sulfur curve, which increases again. In view of this fact, liberation of free sulfur can not be attributed to the insufficiency of the acetone extraction but is probably attributable to depolymerization of the vulcanizate or the like. 2. Acetone Extract.—Although purified rubber was used, the corrected acetone extract due to the formation of resinous substances from the depolymerized or aged hard rubber product showed relatively high values at the beginning of extraction and heating. To some extent, the change in acetone followed a course similar to that of the true free sulfur.
Dispersion of Pigments in Aqueous Medium. I. Mechanism and Evaluation of Dispersing Agents
Authors: Daniel F. K. 
Published: February 2011

Abstract
(1) In Part I the difference in the functions of wetting, dispersing and protecting agents is discussed, and explanations of the different mechanisms by which they act are suggested. (2) The known methods for testing dispersion are cited. (3) In Part II the dispersing qualities of four different types of agents are compared by the method of sedimentation volume. From the results of this test a newly discovered dispersing agent appears to be the most efficient of the four agents tested. (4) It is found that this new agent has the peculiar property of making a number of pigments actively dilatant. Dilatancy was previously known only as an inherent property of certain substances, not as a property which can be induced by means of surface active agents. (5) Dilatancy is linked with dispersion. It is shown that flocculation, thixotropy, passive dilatancy and finally active dilatancy can be regarded as different states of dispersion, with no distinct line of demarcation between them. Active dilatancy is obtained only at a most complete degree of dispersion. (6) The dilatancy test is regarded as a quick and convenient method of evaluating dispersions in all cases where dispersions of a relatively high degree are obtained. (7) An inconsistency in the results between the sedimentation volume and dilatancy tests on the one hand and the consistency test on the other hand is discussed. Systems containing agent C show no dilatancy and have a relatively large sedimentation volume; yet they remain fluid at concentrations even higher than those reached by dilatant systems. This discrepancy cannot be fully explained, but it is not believed to invalidate the above deductions on the relation between dilatancy and small volume of sedimentation on the one hand and dispersion on the other hand. (8) The mechanism of dilatancy is discussed. The ζ potential and hydration are assumed to be the most important factors. With the addition of discharging cations, dilatancy is gradually destroyed and the state of dispersion reversed.
Refractometer Studies on Rubber-Pigment Mixtures
Authors: Jones H. C. 
Published: February 2011

Abstract
Several years ago, McPherson and Cummings published data on the refractive index of rubber and of rubber-pigment mixtures. They found no difference in the refractive index of rubber from various sources. The degree of mastication did not appreciably change the refractive index. Sulfur in combination with rubber altered the refractive index relatively more than free sulfur in rubber. With the exception of zinc oxide, the pigments and fillers they examined did not affect the refractive index. In the case of zinc oxide, there was a significant increase in refractive index and the fine particle size oxide (Kadox) developed a higher value than the coarser oxide (XX Red). They suggested that zinc oxide probably reacts with the nonrubber components to form salts which dissolve and change the refractive index. This laboratory found that, for a series of various particle size zinc oxides in rubber, the increase in refractive index was inversely proportional to the particle size of the oxides; that is, a fine particle size zinc oxide increased the refractive index somewhat more than a coarse oxide. It was also observed that the refractive index of zinc oxide-rubber mixtures increased proportionally with each addition of zinc oxide until the opacity of the zinc oxide-rubber mixture became too great (over 6 per cent) to allow measurement by transmitted light.
Rubber as Antivibration Material
Authors: Kosten C. W. 
Published: February 2011

Abstract
The idea of using rubber as a material for the damping and insulation of mechanical vibrations is not new. That this application of rubber has had no great scope up to now can be ascribed to a combination of circumstances: on the one hand there are unlimited varieties of rubber, concerning which rubber manufacturers publish no technical data, which can be relied on for specific projects; on the other hand there is a lack of knowledge of the behavior of rubber by builders themselves. In these circumstances it seemed desirable that the Rubber Foundation should endeavor to assist builders in this respect, and to this end a basic research into the vibration characteristics of rubber has been carried out. We shall report here on several points resulting from this investigation. Moreover we shall also discuss what can be expected of rubber, how it can be most economically used, and what advantages it shows over other materials. Rubber at the present time is unjustly considered an untechnical material, yet of late the rubber industry has made enormous advances. Types of rubber of different hardnesses can be made which for practical purposes are ideally elastic, since they are in no way plastic, and their durability is so great that a piece a few centimeters thick has almost an unlimited length of life, for example, ten to twenty years, without any appreciable change in properties. The generally feared aging symptoms in rubber for technical applications are now of secondary importance. These are actually not more than a surface oxidation which can injure thin rubber articles of poor quality in a comparatively short time, but has no influence on thicker articles. However, this does not mean that adequate attention should not be given to this question. For such a purpose one must use a superior type of rubber, from the best material, vulcanized by an expert.
A Quantitative Method of Expressing Flex-Cracking Results
Authors: Newton R. G. 
Published: February 2011

Abstract
In addition to providing a means of obtaining accurate quantitative results for individual flex-cracking tests, such as the De Mattia or Du Pont tests, the application of discriminant function analysis suggests a basis for standardizing the entire test method, so that objection to the test for specification purposes is thus concerned only with the reproducibility of the results, a problem which can now be investigated with greater confidence and ease. In connection with the accuracy of the method it may be contended that much depends on the subjective attitude of the tester who grades the samples with the photographs. When half-scores were not employed, the accuracy was limited mainly by the coarseness of the scale. This suggests that the grading is objective and, although no comparison, based upon statistical methods, has been made to determine the discrepancies between operators, no circumstance has occurred to suggest that important divergencies of opinion do exist. In addition, the analysis has been repeated on a further series of fifty samples, and the values found for the scoring constants were not substantially different from those obtained in this investigation. There is thus good reason to believe that this method of assessing the results will form a valuable means of investigating the causes of variation in flex-cracking test results and of recording the conclusions from the tests. The author wishes to thank the Board of Management of the Research Association of British Rubber Manufacturers for permission to publish the results given in this paper.
Hevea Latex: Effect of Proteins and Electrolytes on Colloidal Behavior
Authors: Kemp A. R. , Straitiff W. G. 
Published: February 2011

Abstract
1. Three protein fractions have been isolated from fresh and ammoniated latex serum. The usual color and precipitation reactions have been carried out, and they place these proteins in the classification of conjugated glycoproteins. Proteins from fresh latex differ in composition from, and are less sensitive to, coagulating influences than protein from ammonia-preserved latex. 2. Coagulation tests using latex coagulants were performed on the protein hydrosols. It was found that, as the concentration of electrolytes decreased, coagulation of the proteins was inhibited, whereas coagulation readily took place when salts were present in sufficient concentration. 3. Normal ammoniated latex has been subjected to extensive dialytic treatment in specially constructed apparatus. As the ash content of the total solids from the latex approached a value of 0.1 per cent, the mechanical stability decreased and the chemical stability increased. Addition of excess acid or alkali to dialyzed latex yielded stable latices which were highly resistant to spontaneous coagulation. 4. Quantitative coagulation studies, using methyl alcohol and salts of varying types and made on dialyzed latex adjusted to various pH conditions, show that small amounts of a dissolved salt greatly aid coagulation. Considerable variation in the effectiveness of different salts was found. In acid latex of pH 2.5 the charge on the latex particles was reversed from negative to positive, and the salt effect was shown to be different from that experienced in the case where the pH was on the negative side of the isoelectric point. 5. The amount of alcohol required to coagulate dialyzed latex depends on the pH of the latex. It is shown that the amount of alcohol required for coagulation increases on each side of the isoelectric point, which was determined to be at a pH of 4.15. 6. The protective mechanism of proteins has been discussed on the basis of the electrical charges induced on the surface of the latex particles by the presence of the protein layer. The zwitter-ion effect induced by the presence of free amino and carboxyl groups in the rubber proteins is of fundamental importance in determining the colloidal characteristics of latex.
The Proteins of Hevea Brasiliensis. 1. Analysis of a Product Isolated from Dried Latex
Authors: Tristram G. R. 
Published: February 2011

Abstract
A protein has been isolated from dried Hevea latex and analyzed for amido-nitrogen, tyrosine, tryptophan, cystine, methionine, the basic amino-acids and the dicarboxylic acids. The dicarboxylic acids were estimated in 4.0 grams of protein, experiments on casein having shown that, under such conditions, approximately 90% of the glutamic acid and aspartic acid was recovered as crystalline derivatives. It was also found possible to estimate arginine and lysine in the filtrate from the calcium salts of the dicarboxylic acids. The protein is, in many respects, similar to the proteins found in leaves of other plants (Table IV). Further work is in progress to investigate the relationship of the isolated protein to the total protein of latex.
The Dialysis of Latex and the Properties of Dialyzed Latex
Authors: Van Gils G. E. 
Published: February 2011

Abstract
Since the dialysis of latex is becoming more and more important, a brief sketch will be given here of the principle on which the process is based, together with some information on the properties of dialyzed latex. Whereas, in the beginning, dialysis was carried out only in the laboratory, the process has slowly acquired more significance in practice. Moreover, as applied to latex, dialysis has proved useful not only for physicochemical investigation of the product but also, among other uses, as an important aid in preparing special latexes.