bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Composition and Characteristics of the Rubber in Hevea Latex
Authors: Twiss D. F. , Carpenter A. S. 
Published: February 2011

Abstract
IMPORTANCE OF THE SERUM SUBSTANCES The importance of the non-rubber components of latex, and particularly the protein components, in deciding the behavior towards coagulating agents was recognized at a relatively early date. Indeed, some investigators regarded the coagulating effect as being exerted only by way of the protein, the addition of the coagulants leading initially to its precipitation from solution in the serum, and thereby to the aggregation of the rubber globules. To-day the stability of latex as an aqueous dispersion of rubber globules is still regarded as being dependent on the non-rubber components of the latex. The material actually responsible for its stability, however, is now known to be adsorbed on the surface of the globules, and the physical behavior of the latex globules towards extraneous influences depends on the adsorbed film rather than on the rubber. This is remarkable, as the adsorbed layer, based on the approximation that one gram of protein covers a surface area of 107 cm.2, probably constitutes only 0.6% of the weight of the rubber globules, or thereabouts. The protective layer is not immovably attached, although in fresh latex it is possibly more firmly held than in preserved latex. It should be noted that the adsorbed coating normally represents only a small fraction of the total hydrophilic surface-active substances in the latex, and the stability of latex is less influenced by decrease in the proportion of the non-rubber components than might at first be expected. Latex purified by triply centrifuging shows little, if any, increased tendency to coagulation.
The Chemistry of Natural Rubber. III. The Effect of Ammoniation on the Latex of Hevea Brasiliensis
Authors: Roberts Kenneth C. 
Published: February 2011

Abstract
The bulk of the liquid latex of commerce is protected against putrefaction by addition of 0.7–1.5% of ammonia. It is widely recognized that latex is profoundly affected by this procedure, but little insight has hitherto been obtained into the chemistry of the changes. The problem has now been approached by applying to latex before and after preservation with ammonia the method of analysis described in Part I (Rubber Chem. Tech. 10, 1(1937)). Ammoniated latex which has been kept under representative conditions of storage for periods of 8 weeks to 18 months differs in general in composition from fresh latex in the manner shown in the table. The quantitative findings for ammoniated latex, however, vary appreciably with the time of storage and with the ammonia content. The analysis recorded was made on latex containing 0.7% of ammonia after 18 weeks' storage.
X-Ray Diffraction Patterns of Crystalline Sol Rubber Prepared from Ethereal Solution
Authors: Clark George L. , Gross Siegfried T. , Smith W. Harold 
Published: February 2011

Abstract
In a previous publication there was reproduced an x-ray diffraction pattern of crystals obtained from a solution, cooled to temperatures between −40° and −50° C, of an ether-gel fraction of rubber from Hevea brasiliensis. Measurements of three strong interferences indicated that the crystals were similar to those of stretched gel rubber and of frozen sol, gel and total rubber. Although many attempts were made at that time, unsatisfactory diffraction patterns were obtained with crystalline ether-sol rubber. The interferences were faint and not suitable for accurate measurement and analysis. Since the crystalline material is bulky and some specimens are more compact than others, it seemed possible that the average number of cell diameters was too small to permit sharp definition, and that more material was required for the examination by x-rays. However, it is not certain that lack of definition was caused by insufficient crystalline rubber. The possibility that parts of the long-chain molecules become crystalline and that parts remain amorphous is not excluded, and might be its cause. Additional work with crystalline sol rubber, using a slightly different experimental procedure and more material than in earlier experiments, finally resulted in a satisfactory pattern.
External Influence and the Internal State of Rubber
Authors: Wittstadt W. 
Published: February 2011

Abstract
With continued progress in technology, highly elastic products have come to be of great importance at the present time. Whereas in earlier years rubber was the only product which could be classed in this category, in the last few years many new products with properties resembling those of rubber have been added to the list. This is to a great extent due to the fact that chemical research has given a better insight into the parent substance of rubber and the structural nature of rubber itself. According to these researches, rubber is representative of a group of highly polymeric, organic natural substances, whose long molecules are composed of small structural units in uninterrupted repetition. By reproducing artificially the relations existing in the structure of the rubber molecule, it has been possible by chemical synthesis to prepare highly elastic substances from allied substances or from substances which polymerize in an analogous way. But in spite of this success, chemical investigations have not yet reached a point where it is possible to explain the mechanism of elasticity, for actually elastic phenomena do not depend on chemical changes ; an explanation is rather to be sought in changes which take place in the relative positions and forms of the rubber molecules.
Inhibition of Crystallization of Rubber by High Pressure
Authors: Dow R. B. 
Published: February 2011

Abstract
Bekkedahl has shown that crude rubber at atmospheric pressure freezes in the temperature range from −40° to + 10°C. and melts in the temperature range from 6° to 16° C. The transition is from amorphous rubber to crystalline rubber which is the stable modification between −72° and 6° C. His measurements of the freezing at 0° C. showed that about 280 hours were necessary for completion of the transition, the volume decreasing by 2.2 per cent in such a manner that the volume-time curve was S-shaped. This communication reports the inhibition of crystallization at high pressure. Crude smoked sheets were packed tightly in a pressure chamber and isopropyl alcohol was used to transmit the pressure. The chamber was kept at 0° C. in a well-circulated ice bath. A pressure of 8000 kg. per sq. cm. was applied, and its constancy observed over a period of 14 days. The sensitivity of the manganin gauge used for pressure measurement was such that changes of 5 kg. per sq. cm. were detectable. Outside of slight erratic pressure changes caused by change of temperature around part of the press that was not kept at 0°, “no change of pressure due to crystallization was detected during the 14 days.” Examination of the rubber immediately after pressure was released showed that it was still in the amorphous state.
The Dependence of the Stress on the Temperature of Rubber Elongated to a Constant Degree
Authors: Hauk V. , Neumann W. 
Published: February 2011

Abstract
An instrument for measuring stresses was constructed, whereby changes in tension brought about by changes in temperature in rubber maintained at constant elongation were measured. These measurements were carried out with three types of vulcanizates. After measures were taken in the case of weakly vulcanized samples to eliminate the disturbing factors arising from crystallization, the fact was established that stress is directly proportional to the absolute temperature for all types of vulcanized rubber, as required by theory. It is shown that under some conditions the stress-temperature coefficient depends on the degree of vulcanization, the coefficient decreasing with increase in the degree of vulcanization. The experimental results are discussed, and an explanation is offered to account for the dependence of the stress-temperature coefficient on the degree of vulcanization.
Preparation and Properties of Halogen Derivatives of Rubber from Latex
Authors: Baker H. C. 
Published: February 2011

Abstract
The paper deals with the preparation and properties of chlorine and bromine derivatives of rubber from latex, obtained by the generation of nascent chlorine in situ and by the addition of bromine water. Attention was given to compounds containing small amounts of halogen, which still showed marked elasticity, in addition to the powders containing large proportions of halogen. When stabilized preserved latex was treated with an excess of hydrochloric acid and a suitable amount of oxidizing agent, an exothermic reaction occurred which, if uncontrolled, led to the formation of white powders containing about 50% chlorine which swelled in organic solvents without dissolving. If, however, the temperature was not allowed to rise substantially above atmospheric, at least in the early stages of the reaction, products of similar appearance and chlorine content were obtained, which nevertheless were readily soluble in a wide range of solvents, including vegetable oils, to give thin solutions which formed brittle films adhering strongly to glass and metal. Analysis of a chlorinated rubber containing 55.8% chlorine corresponded approximately to the formula C20H26Cl11O2.
Improvements in Methods for the Rapid Analysis of Rubber
Authors: Marty A. 
Published: February 2011

Abstract
In the course of experiments carried out by the research laboratory of the Compagnie du Gaz of Paris on rubber gaskets for gas lines, we were led to search for a more precise method for the determination of ingredients in vulcanized rubber which would be more rapid than the method involving mild incineration in a crucible. When it is desired to make a rapid determination of the inorganic and organic substances in rubber, it is customary to incinerate the rubber in a closed crucible under moderate conditions. Although this method is rapid, it is not possible to separate with any degree of certainty the rubber from carbon black and mineral substances, for the rubber may carbonize in the crucible and leave a deposit of black, which adds itself to the black originally in the rubber and thus vitiates the results. It was felt that incineration in an inert medium would give results which would approach more closely to the true values. Since in this case a crucible could not be utilized satisfactorily, recourse was had to a Pyrex tube containing a platinum boat. The apparatus finally adopted is described in the following pages.
Color Measurement and Its Application in the Rubber Industry
Authors: Willott W. H. 
Published: February 2011

Abstract
The object of this paper is to bring to the notice of rubber technologists the recent advances which have been made in the science of color measurement and its applications. As the demand for colored articles increases, it becomes necessary to use a more specific way of recording color than to say that an article is “rose pink” or “olive green.” The use of standard samples is cumbersome in regard to storage, and may be misleading in the case of rubber products, as they are liable to color changes. The increasing use of raw rubber in the form of latex has raised the question of the measurement of its “whiteness” as a guide to its quality. It has been suggested also that the transparency of thin dried latex films could be used for this purpose. Both these methods entail the measurement of the color of almost white objects. MacAdam has shown that it is difficult to judge the whiteness of articles by direct vision. He asked 30 observers, half of whom were women, to arrange white objects in order of increasing whiteness. The arrangements showed great divergence, and the observers were unable to repeat their observations. When these samples were classified by means of a suitable colorimeter, consistent and reproducible results were obtained by different observers. Visual observations are subject to the effect of many variables, and are therefore so misleading that it at once becomes apparent that such determinations can only be successfully carried out with a colorimeter used under carefully standardized conditions. Besides the measurement of the whiteness of latex such problems arise as the covering power of pigments, especially of white pigments, the use of dyestuffs in brightly colored articles, the transparency of rubber lacquers and varnishes, all of which require a measurement of color in some form or another.
Variation in the Composition and Properties of Fresh Latex. And Subsequent Changes on Ammoniation
Authors: Rhodes Edgar 
Published: February 2011

Abstract
Systematic examination has been made of 163 samples of latex drawn at the approximate rate of three per week over a period of fourteen months from a single tapper's task on old seedling trees, newly opened after several years' rest on the continuous alternate daily system. The latex samples were all examined, both in the fresh condition and after 10 days and 15 days preservation with 0.7% ammonia; during the last eight months certain tests were also made on the latex immediately after ammoniation on the day of collection. The tests included dry rubber content, total solids, acetone extract and acid number of whole-latex rubber films, surface tension, viscosity, stirring stability and ease of creaming. It has been observed that: (1) The difference between percentage total solids and percentage dry rubber content is greater after 10 days' preservation than in the fresh condition. (2) The acetone extract and its acid number from whole-latex film are less in freshly-ammoniated latex than in fresh latex, and very much greater in ammoniated latex stored for 10 days. The acid number after 10 days preservation is usually about twice that of the fresh latex. These findings and their implications are discussed in the text, in which experimental figures are given. High dry rubber content usually connotes low acetone extract and acid value in the fresh latex. (3) Values for surface tension before and after ammoniation are given. The fall in surface tension as a result of ammoniation has not been proven to be governed by the changes in acetone-soluble material, or the acid number thereof. (4) The viscosity of ammoniated latex is shown to be very significantly correlated with its dry rubber content. In the case of fresh latex the degree of correlation is much less; a possible reason for this is advanced. Experimental results are given. (5) The initial stirring stability is shown to be influenced by the initial dry rubber content of the latex. The data do not provide an adequate explanation of the changes in stability which take place on storage. (6) The creaming ease of new latex appears also to be influenced by its initial dry rubber content, but the present data are not adequate fully to explain the variations which are noted.
The Chromatography of Rubber Solutions
Authors: Cajelli Giampietro 
Published: February 2011

Abstract
In the opinion of Pummerer, there is considerable doubt about the homogeneity of the fractions obtained by fractional precipitation of rubber from dilute benzene solutions, both with respect to the size of the molecules and to the state of aggregation. Based on the results of x-ray measurements of fibrous substances, to which type stretched rubber belongs, Meyer and Mark have advanced the hypothesis of the existence of chains of primary valences and of a micellar structure. PURIFICATION OF RUBBER There are four important and at the same time essentially different ways of carrying out the difficult process of purifying rubber. According to Harries, acetone extraction gives a colored product and leads to profound changes in the elastic properties. Staudinger adopted the method described by Wildmann in 1911, which involves the use of a mixture of acetone and chloroform. On the other hand, Pummerer and Koch used the method of fractional precipitation; the rubber after severe mastication was extracted with acetone, was dissolved in benzene, the liquid was allowed to stand for several weeks, the solution was decanted from the insoluble residue and was fractionally precipitated by alcohol and acetone. More recently this same method has been perfected by Pummerer and Meidel, and by this means a fraction of crystallized rubber was isolated from the mother liquors of the fractional precipitation. Finally Pummerer and Koch have purified rubber by treatment with an alkali, combining the precipitation method with the use of a solution of potassium hydroxide in methanol. Later this method was modified by Pummerer and Pahl. The use of latex in place of crude rubber is the most important development in obtaining a satisfactory product. De Vries and Beumée-Nieuwland have described in detail some results obtained with fresh latex. The total-rubber obtained by the methods just described contains, according to the quality and the age of the sample of latex, from 0.1 to 0.4 per cent of nitrogen which cannot be removed by washing, even when this is exhaustive.
The Properties of Polymers in Solution. X. Ultrafiltrations of Rubber Solutions
Authors: Meyer Kurt H. , Jeannerat Jean 
Published: February 2011

Abstract
It is a recognized fact that ultrafiltration is one of the most valuable methods for the study and treatment of colloidal suspensions formed of compact spherical particles. Not only is it possible to separate this type of particle from a solvent by means of a suitable ultrafilter, but it is also possible to determine the size of the particles by means of calibrated ultrafilters. Up to the present time, however, ultrafiltration has been utilized very little in the study of chain molecules, and no accurate data are available on the behavior of colloidal solutions of chain molecules during ultrafiltration. In the following discussion, the results of some experiments on the ultrafiltration of rubber solutions are described. Dilute solutions of rubber in toluene can be separated completely into rubber and solvent by ultrafiltration under pressure through fine ultrafilters with pores as fine as about 50 ḿ (“Fine” Cellafiltres and Membranfiltres). Solutions of crepe and solutions of masticated rubber give the same results.
Behavior of Rubber Hydrocarbon in a Molecular Still
Authors: Smith W. Harold , Wing Henry J. 
Published: February 2011

Abstract
Some investigators believe that rubber consists of associated molecules, and others accept Staudinger's view that long-chain molecules are formed by polymerization. Pummerer, Andriessen and Gündel have obtained a molecular weight as low as 600. Meyer and Mark believe that it is approximately 5,000, although they calculated on the basis of osmotic pressures values as high as 350,000. They, as well as Pummerer, consider that rubber is an associated colloid and that high molecular weights are caused by aggregates, sometimes called micelles. Staudinger, however, considers that the long-chain rubber molecule itself has a molecular weight of 200,000 or even 350,000, and that products with lower values, which may be formed in rubber, result from degradation. if the molecules are small it might be possible to distil them if their vapor pressure could be sufficiently increased, but none would distil without decomposition if the molecules are very large. Because the vapor pressure of rubber below its decomposition temperature is low, it appeared of interest to attempt to distil the material in a molecular still. Paraffin wax and sugar, both substances of relatively high molecular weight, have been successfully distilled in this type of apparatus. Subsequent to the work described in this paper, the molecular weight of sol rubber prepared at this Bureau was determined by Kraemer and Lansing of E. I. du Pont de Nemours & Co., Inc. They used the Svedberg method of sedimentation equilibrium in an ultracentrifuge with ethereal solutions of sol rubber. The temperature of the solutions during determinations was approximately 10° C, and an average value of 460,000 was obtained. There was evidenced of a mixture of molecular species.
A Contribution to the Characterization of the Plastic-Elastic State
Authors: Rohde E. 
Published: February 2011

Abstract
The manner in which vulcanized rubber can be deformed and yet return almost completely to its original dimensions after the stress is released is a unique and characteristic property. Technically the problem in testing rubber is to evaluate this property and to define it in terms of the factors which are concerned. To define completely this property of rubber whereby it is susceptible to deformation, it is necessary to know the stress, the elongation, the energy expended, the energy lost, the time and the temperature. The stress, elongation and energy expended are closely related and are characterized by the stress-strain curve, which in turn depends on the time and temperature. In addition, it must be borne in mind that rubber can be deformed either by tension or by pressure, but this will not be discussed further here. On the other hand a rather puzzling problem will be considered, the solution of which brings out the fact that the three variables involved in any deformation, viz.: (1) The time or frequency. (2) The temperature. (3) The interrelated factors: stress, elongation and energy expended, must be varied considerably in order to characterize the phenomena of deformation and that when this is done, unexpected results are obtained.
Properties of Hard Rubber. VII. Measurement of Plastic Flow as Affected by Temperature
Authors: Church H. F. , Daynes H. A. 
Published: February 2011

Abstract
The merits of the Martens apparatus as an instrument for measuring plastic flow of solid insulating materials at various temperatures are discussed and the features of a new torsion apparatus which is designed to overcome certain objections to the Martens apparatus are explained. Details of the construction of the new apparatus and of its method of operation are given. Deflection-time and deflection-temperature curves determined with the torsion apparatus for a typical hard rubber are given and the form of these curves is discussed. The “yield temperature” is defined from the characteristic shape of the deflection-temperature curve. It is shown that deflection is proportional to stress, and that the magnitude of the stress used and the dimensions of the test-piece have no influence on the general shape of these curves. An empirical formula connecting deflections, stress and test-piece dimensions is given. The influence of degree of vulcanization on the plastic flow of an unloaded (rubber-sulfur) hard rubber at various temperatures is described. “Yield temperature” increases with time of vulcanization up to some limiting value. Recovery of shape of the test-piece after removal of torsional stress is briefly discussed. Comparative tests on several hard rubbers were made with the Martens apparatus and the torsion apparatus, both used at a series of steady temperatures. The same type of deflection-temperature curve was obtained, but the. “yield temperature” as slightly higher with the Martens apparatus than with the torsion apparatus. The torsion apparatus provides more complete data and is more convenient to operate than the Martens apparatus.