bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Weight and Polydispersivity of Rubber by Diffusion Measurements
Authors: Pasynskii A. G. , Gatovskaya T. V. 
Published: February 2011

Abstract
The study of diffusion in solutions of natural rubber (light crepe) by Lamm's method showed that even with a concentration of 0.1 per cent the normalized experimental diffusion curves diverge from the ideal Gaussian curve (Figure 1), in that they are characterized by a marked asymmetry and an excess of the maximal ordinate. It follows from an analysis of the experimental curves by the method of moments (up to moments of the fourth order) that they belong to Type IV Pearson curves, that is, to asymmetrical distribution curves with asymptotic branches. The determination of the perturbation multiplier enables us to calculate the course of the experimental curves with a fair degree of accuracy. The physical cause of asymmetry of the diffusion curves is the difference in the rate of diffusion to both sides of the interface (of the polymer into the solvent and back) due to a marked intermolecular interaction in the solution of the polymer at a given concentration. With a decrease of the concentration or of the molecular weight of the dissolved substance, the asymmetry of the diffusion curves becomes less pronounced. However, this asymmetry does not preclude the computation of the average diffusion coefficient D from the standard deviation of the curve. It can, indeed, be shown that the probable error does not exceed 1 per cent. The average value found for natural rubber in carbon tetrachloride is D20°=0.71×10−7 sq. cm. per sec.
Preparation and Properties of Rubberlike High Polymers. II. Polymerization of Mixtures in Bulk
Authors: Koningsberger C. , Salomon G. 
Published: February 2011

Abstract
Mixtures of butadiene and dimethylbutadiene with varying quantities of styrene and acrylonitrile were copolymerized under various catalytic conditions at 100° C. The formation of cyclic dimers from dienes and vinyl compounds is, in some cases, much more pronounced than the dimerization of the dienes alone. Since the latter is also a kind of Diels-Alder reaction, a series with increasing dienophilic properties can be established from a comparison of the yields of cyclic dimers. From solubility and swelling experiments it is evident that the polymers prepared from butadiene and the vinyl compounds and those from dimethylbutadiene and acrylonitrile are true copolymers. The mechanical properties of the copolymers from butadiene and increasing amounts of a vinyl compound change gradually from those of a rubber to those of the polyvinyl compound. The copolymers from a mixture containing 30 per cent styrene or acrylonitrile are very similar to Buna-S and Perbunan, respectively. Copolymers of the same composition from dimethylbutadiene and acrylonitrile, on the other hand, form a new class of thermoplastics with a much higher temperature of elasticity.
Preparation and Properties of Rubberlike High Polymers. III. Polymerization of Mixtures in Emulsion
Authors: Salomon G. , Koningsberger C. 
Published: February 2011

Abstract
The copolymerization in emulsion of butadiene with varying proportions of styrene and acrylonitrile and of dimethylbutadiene with the latter vinyl compound was studied on a laboratory scale. An essential difference between polymeric vinyl compounds and polydienes is the olefinic character of the latter, which leads to typical secondary changes in the polymers originally formed during the completion of the reaction. Such changes are of fundamental importance for the ultimate mechanical properties of polymers and copolymers based on dienes. After a brief discussion of the general theoretical line of thought serving as a base for our experiments, the influence of various factors on the rate of polymerization is pointed out and demonstrated by experiments. The changes in the nitrogen content of copolymers from acrylonitrile and the yields as a function of the reaction time also were studied. From an investigation of some physical properties, such as solubility and swelling, the existence of true. Copolymers (of unknown irregularity) is established. Copolymers from dimethylbutadiene and acrylonitrile represent a new class of olefinic thermoplastics resembling gutta-percha.
The State of Polydispersion of Hevea Latex. II.
Authors: Hessels J. H. E. 
Published: February 2011

Abstract
The influence of the degree of dispersion in latex on the composition and properties of the rubber was studied in detail by means of a series of latices, the mean particle size of which ranged from 1.1 to 0.15µ in diameter. These fractions were first obtained by centrifugation of preserved latex, and the degree of distribution was measured by photomicrographic analysis and by sedimentation. This method of fractionation yields latices and rubbers with compositions which differ widely. With decrease in the size of the particles, their surface area per unit of rubber increases, and the percentage of nonrubber components which is adsorbed irreversibly or which is dissolved in the serum increases greatly. On the contrary, the degree of polymerization decreases with decrease in the diameter of the particles. This may be explained by the fact that, in the beginning, the polymerization of the globules is relatively low, and that it progresses under the influence of a catalyst present in the serum. In brief, then, systematic dispersoidal analysis of Hevea latex is of prime importance in the plantation rubber industry.
The Thermoelastic Properties of Rubber
Authors: Meyer Kurt H. , Van der Wyk A. J. A. 
Published: February 2011

Abstract
In an earlier communication, Meyer, von Susich and Valkó showed that within certain limits of extension (100 to 300 per cent) and at constant elongation, the stress in a rubber sample is proportional to the absolute temperature. Within these limits, the stress is therefore analogous to the pressure of an ideal gas, which at constant volume is likewise proportional to the absolute temperature. Such behavior of rubber or of any other rubberlike substances is said to be ideal. However, a sample of rubber which exhibits ideal behavior at elongations of 100 per cent and higher deviates from this ideal behavior at elongations below 100 per cent and greater than 500 per cent. One of the reasons for such deviations at high elongations has already been discussed in an earlier publication. As a result of extension, rubber tends to crystallize. The resulting crystallites do not contribute to the elastic stress, but if the temperature is raised, they fuse and thereby increase the tension, which then increases more rapidly than is the case with an ideal rubber. Deviations from ideal behavior at small deformations have not yet been studied thoroughly, so it is these deviations which are the first subject of discussion in the present paper. First of all the experimental facts will be presented.
The Protection of Rubber against Oxygen by a Deactivating Effect
Authors: le Bras Jean , Hildenbrand René 
Published: February 2011

Abstract
It has already been shown by one of the authors that certain substances protect vulcanized rubber against deterioration by oxidation and yet have practically no retarding effect on its rate of oxidation. The mechanism of the action of these agents is, therefore, different from that of antioxygenic agents, and it has been called a deactivating effect. The first substance which was found to manifest this hitherto unrecognized effect was mercaptobenzimidazole. The attempt has been made to gain a better understanding of the conditions under which mercaptobenzimidazole is active, both alone and in the presence of an antioxygenic substance. It was first found that mercaptobenzimidazole, in contrast to most antioxygenic agents, has no protective action against aging in the case of simple rubber sulfur vulcanizates, i.e., vulcanizates which do not contain any other ingredients which are ordinarily added, notably accelerators, zinc oxide and plasticizers. Systematic experiments with these various types of ingredients show the indispensable part played by zinc oxide, in view of which it may be assumed that a zinc salt is formed during vulcanization by reaction of the zinc oxide with the acid group of the thiol. As a matter of fact, when zinc mercaptobenzimidazolate is added to a rubber-sulfur mixture, it protects the vulcanizate from aging. Furthermore, if the reaction of mercaptobenzimidazole with zinc oxide is rendered impossible by replacing the hydrogen of the SH group by a radical, there is no longer any protective effect. 2-Methylmercaptobenzimidazole, for example, shows no protective action under any conditions.
The Interaction between Rubber and Liquids. VIII. A New Examination of the Thermodynamic Properties of the System Rubber ± Benzene
Authors: Gee Geoffrey , Orr W. J. C. 
Published: February 2011

Abstract
New vapor pressure data are reported for rubber-benzene mixtures, and used to calculate thermodynamic functions for the system. The heat of dilution is comparable with that measured calorimetrically for a polyisoprene of low molecular weight. Comparing the results with the available theoretical calculations it is shown that a significant contribution to the entropy and heat of dilution of polymer solutions at low concentrations results from the occurrence of polymer-polymer contacts within individual molecules due to statistical kinking. Our thanks are due to J. L. Bolland, (Miss) J. Ferry, and H. P. Koch for the experimental assistance acknowledged in the text. The work described in this paper forms part of the program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.
Modifications of Chlorinated Rubber Brought about by Some Organic Bases. Piperidine
Authors: Jarrijon André , Lepetit Francis 
Published: February 2011

Abstract
By virtue of certain characteristics, among others its resistance to chemical reagents, which is one of its most valuable properties, chlorinated rubber has already found a wide field of applications. It is curious, however, that some materials which are only slightly corrosive are capable of affecting it, e.g., water and certain organic bases, the basicities of which are considerably lower than the basicity of potassium hydroxide or of sodium hydroxide.
Role of Carbon in Oxidation of GR-S Vulcanizates
Authors: Winn Hugh , Shelton J. Reid , Turnbull David 
Published: February 2011

Abstract
1. Carbon black is a catalyst for the oxidation of GR-S vulcanizates. The increased rate of oxygen absorption with increased loading is, however, a function of surface area rather than weight. Different types of carbons show different degrees of activity for a given surface area; the furnace carbons studied were, for example, only 55 per cent as active as channel black in promoting oxidation. 2. The rate constant for the initial rapid absorption of oxygen by GR-S tread stocks is independent of carbon loading. The presence of carbon is, however, essential to activate the centers involved in this initial stage, and the number of activated centers increases with carbon loadings, so that the amount of oxygen absorbed in a given time is also increased. 3. The second or linear stage of oxygen absorption involves two types of reaction with the remaining oxidizable centers in the polymer: a reaction with centers not under the catalytic influence of the carbon black, and a reaction catalyzed by carbon. 4. A theoretical equation was presented which permits the calculation of oxygen absorption by stocks containing either furnace- or channel-type carbons with various surface areas and loadings. The validity of the theory on which the derivation was based is supported by the quantitative correlation of calculated and observed rates of oxygen absorption for stocks containing carbons of both types, with surface areas ranging from 3.7 to 15.7 acres per pound and with loadings of 0 to 75 parts per 100 parts of GR-S. 5. The additional oxygen absorbed at higher loadings of carbon was shown to produce a correspondingly greater deterioration of physical properties.
The Permeability of Rubberlike Substances to Gases
Authors: Van Amerongen G. J. 
Published: February 2011

Abstract
The measurements of the permeability of various elastomers to hydrogen which have been described make particularly evident the following points. The permeability values of Perbunan, Neoprene and Oppanol are from one-third to one-eighth those of natural rubber. The higher the percentage of combined sulfur in natural rubber, the lower the permeability. The addition of a plasticizing agent has only a small effect on the permeability. The addition of progressively greater percentages of inorganic or organic fillers brings about a disproportionately great reduction in permeability. Among mixtures of natural rubber with other compounding ingredients, three mixtures in particular are noteworthy for their low permeability: (1) A mixture of equal parts of natural rubber and Oppanol (polyisobutylene). (2) A mixture of rubber with 15–20 per cent by vol. of bentonite, prepared by starting with latex. (3) A combination of these two types of mixtures (1) and (2). Finally it was proved experimentally that stretched rubber has a lower permeability than the corresponding unstretched rubber, probably as a result of crystallization of the stretched rubber.
The Permeability of Different Rubbers to Gases and Its Relation to Diffusivity and Solubility
Authors: van Amerongen G. J. 
Published: February 2011

Abstract
Since the permeability of rubberlike substances to gases is related to the solubility and rate of diffusion of the gases in those materials, these individual values should be known. The permeability of a membrane was measured manometrically and the diffusivity was derived from the time lag of the permeation. The solubility of the gas was computed from the permeability and the diffusivity; the solubility was found by direct measurement. In this way eight different gases were tested with nine elastomers at different temperatures. The permeability of a membrane to a given gas is not affected by the presence of a second gas. The differences in permeability of different elastomers to a given gas are caused mainly by differences in rate of diffusion and only in a very minor degree to differences in solubility. Differences in permeability of the same elastomer to different gases are caused not only by differences in rate of diffusion but also by differences in solubility. A linear relationship was found between the logarithm of the solubilities of different gases in natural rubber and their critical temperatures, so the higher the critical temperature of a gas, the better it dissolves. The presence of polar groups in an elastomer reduces the solubility of nonpolar gases and increases the solubility of polar gases in the elastomer. The various rubbers behave towards gases like organic liquids. The activation energy of the diffusion and the heat of solution were calculated from the temperature function of the diffusivity and the solubility. As the diameter of the molecule of the gas increases, the rate of diffusion decreases, while the activation energy of the diffusion becomes greater. The presence of polar groups and methyl groups in elastomers causes low rate of diffusion, which involves a great activation energy of diffusion. It is presumed that the activation energy of the diffusion is required to separate the rubber molecules for the displacement of the gas molecules. The attempt to elucidate the constant D0 in the equation D=D0 exp (−E/RT)—which proves to be a function of the activation energy of the diffusion E—by reference to one of the formulas published in the literature failed. An empirical formula was derived whereby D0 is directly related to the activation energy E.
Correlation of Tensile Strength with Brittle Points of Vulcanized Diene Polymers
Authors: Borders A. M. , Juve R. D. 
Published: February 2011

Abstract
For several years work has been carried on here to evaluate a large number of diene polymers and copolymers as rubberlike materials. The writers have observed that changes in polymer composition which result in improved tensile strength and crack-growth resistance of the vulcanizate cause an increase in low temperature stiffness and a rise in brittle point. This generalization seems to apply to tensile values measured at elevated temperatures as well as to those at room temperature. For example, a butadiene copolymer of dichlorostyrene can be made which, as a tread type of vulcanizate, exhibits a tensile strength of over 1500 pounds per square inch at 93° C, in comparison with 800 to 1000 pounds per square inch for GR-S in the same test tread formula at the same temperature. The brittle point of the butadiene-dichlorostyrene rubber, however, is −35° C or higher. GR-S treads in the same test have brittle points between − 55° and −60° C. Probably of greater practical importance is the fact that the vulcanizate with the higher brittle point is stiffer at temperatures well above the brittle point. The purpose of this investigation was to determine to what extent the maximum tensile strength of tread stocks of several synthetic rubbers varies with the temperature difference between the brittle point and the tensile testing temperature of each rubber. These data can then be used to judge the validity and extent of the general observation that changes in copolymer composition which increase strength also raise the brittle point.
Properties of Hard Rubber. XIX. Effect of Temperature on Cross-Breaking Strength and Elongation
Authors: Willott W. H. 
Published: February 2011

Abstract
In a series of cross-breaking tests carried out on hard rubber during hot weather, the values of the breaking elongation were higher than was expected, although the cross-breaking strength was of the usual order. It was thought that the high temperature might account for these results by making the hard rubber more plastic. The following experiments were, therefore, performed to investigate the effect of small changes of temperature, such as are encountered at different times of the year, on the cross-breaking strength and elongation. Test-pieces of standard size (75 × 25 × 5 mm.) were cut from a sheet of hard rubber of the composition: 68 per cent rubber, 32 per cent sulfur, which had been vulcanized for 5 hours at 155° C. They were immersed in a beaker of water and kept at the required temperature for about 15 minutes, when they were judged to have attained a steady temperature. The tests were carried out on an Avery fabric-testing machine fitted with special clamps to give a three-point loading test, the distance between the supporting knife-edges being 50.4 mm. (2 in.). These clamps were heated to the temperature of the specimens by means of an electric radiator. The specimens were tested as soon as possible after they had been removed from the water, so that the change of temperature during the test was reduced as far as possible. The standard conditions already laid down, were observed.
State of Cure of Neoprene Vulcanizates. Measurement by the T-50 Test
Authors: Forman D. B. , Radcliff R. R. 
Published: February 2011

Abstract
Generally the physical properties of elastomer vulcanizates are considered to depend on their states of cure. Although many tests for measuring the state of cure have been developed, none are completely satisfactory. Some of them fail to distinguish between the physical or chemical effects of compounding ingredients, others are too laborious to be of practical value. The T-50 test developed by Gibbons, Gerke, and Tingey for natural rubber vulcanizates eliminates some of these difficulties and further reduces the number of tests required for production control. The T-50 test is based on the retraction of a stretched and frozen specimen with an increase in temperature. The temperature at which the sample retracts to 50 per cent of its initial frozen elongation is termed the T-50 value. From a physical standpoint the test is sensitive, precise, and easily performed. From a chemical standpoint the original workers as well as Vila showed that, for any specific natural rubber composition, the T-50 value correlates with the amount of combined sulfur. Since the state of cure of a rubber vulcanizate is frequently discussed in terms of combined sulfur, the T-50 test offers a correlation of the state of cure with combined sulfur without the necessity for involved chemical analyses.
Mechanical Processing of Carbon Blacks. Resultant Effects in GR-S Compounds
Authors: Dobbin R. E. , Rossman R. P. 
Published: February 2011

Abstract
It was suggested that carbon blacks owe some of their characteristic properties to a tendency for individual particles to cluster into chainlike groupings or secondary aggregates. Results of mechanical processing experiments show that application of mechanical work altered or destroyed secondary aggregates. This conclusion was made since resistance to compression had been permanently overcome. Analytical measurements confirmed the supposition that secondary aggregates had been altered or destroyed, since oil absorption and liquid retention values markedly decreased with mechanical work. Finally, properties of compounded GR-S stocks were seriously altered—namely, smoothness of milled stock, high modulus, and enhanced electrical conductivity. It is concluded that these properties were originally caused by the presence of secondary aggregates or structure units. Alternative interpretations of these data are possible—namely, it might be concluded that it was not possible to disperse the densified material to the same extent as the original carbon black. However, this hypothesis contends that a large particle size material is being dispersed. Therefore, a decrease in tensile strength should have been noted. There is also some meager evidence suggesting that the chemical nature or activity of the carbon black surface was altered, so that its contribution to modulus was limited. It is believed, however, that most of the evidence offered by the data presented here preponderantly supports the structure theory of high modulus blacks. The authors consider these results as preliminary in the study of the structure properties of carbon blacks. They appear to be of sufficient interest to be brought to the attention of those studying reinforcement. Data available at present do not permit an interpretation of the contribution of structure to properties of “smooth-out” modulus and electrical conductivity of compounded rubber stocks.
Determination of Polystyrene in GR-S Rubber
Authors: Kolthoff I. M. , Lee T. S. , Carr C. W. 
Published: February 2011

Abstract
A convenient procedure for the determination of polystyrene in GR-S is given. The method depends upon degradation of the GR-S by tert-butyl hydroperoxide in the presence of a trace of osmium tetroxide. Polystyrene is not attacked and is separated by precipitation with ethanol.