bluuebunny/crossref_metadata_2025_split huggingface dataset:
GR-S Latexes in Foam Rubber
Authors: Talalay Leon , Talalay Anselm 
Published: February 2011

Abstract
The superiority of cold GR-S high-solids latex over latex polymerized at 120° F has been demonstrated in foam rubber in terms of greater tensile strength, better elongation at break, higher modulus, improved rebound elasticity, and enhanced low temperature properties. The magnitude of the effect observed is far greater than the corresponding improvement reported in tire tread stocks. A number of polymer modifications in low-temperature polymerized latex were investigated. It was shown that, by the proper choice of styrene content (approximately 10 per cent bound), GR-S foam rubber superior to Hevea foam in subzero properties can be made. The modulus of foam rubber improved significantly with rising Mooney viscosity of the contained polymer, while the elongation at break was affected adversely. The degree of conversion was found to have little bearing on the properties of the resultant foam rubber.
Film from Mixtures of Natural and Synthetic Rubber Latex. Physical Properties
Authors: Pierson R. M. , Coleman R. J. , Rogers T. H. , Peabody D. W. , D'Ianni J. D. 
Published: February 2011

Abstract
When tested in a single standardized procedure for cast latex films, the type of synthetic-rubber latex employed in latex blends containing 70 per cent or more natural-rubber latex had little effect on the stress-strain properties of the mixture. Cold-rubber latexes imparted higher stress-strain values to blends with natural rubber than did the corresponding hot-rubber latexes. The improvement was particularly noted on comparison of tensile product values. Low-conversion synthetic polymers produced higher stress-strain properties than high-conversion polymers in blends with natural rubber, even though their tensile strengths in 100 per cent synthetic stocks were approximately equal. Optimum physical properties were obtained by use of blends with synthetic polymers of medium Mooney viscosity. It is believed that the appearance of an optimum Mooney viscosity is tied in with the necessity of having quite high molecular weight on the one hand, and, on the other, the ability of the particles to knit well, the latter in turn requiring a comparative freedom from tight gel. Tensile product values increased with increasing styrene content in the synthetic polymer, but, correspondingly, the low-temperature stiffening increased. The physical properties of a natural rubber stock are far superior to those of any of the synthetic-rubber latexes tested to date. Cold-rubber latexes now in production are an improvement over high-temperature latexes, for example, in wet gel strength but do not approach natural rubber latex in stress-strain properties.
Notes on the Use of Plasticity Tests to Assess Scorching of Rubber Stocks
Authors: Whorlow R. W. 
Published: February 2011

Abstract
It is shown that the main factor influencing the efficiency of compression plastometers in detecting scorching of a pure-gum rubber mix is the period of compression; this should be at least five minutes for the Williams plastometer at 70° C. Recovery measurements appear to have an even higher efficiency than long period compression tests. Other variations of test conditions are not of great importance. The next point examined is the method of producing scorching in compression test-pieces. Immersion of test-pieces, contained in a metal mold, in a liquid bath gives the most rapid heating. Finally, it is shown that for pure-gum mixes, compression and rotation plastometers give equivalent data, provided that allowance is made for any delay in the heating of test-pieces used for compression tests.
Study of the Factors Affecting the Friction of Tread Compounds on Ice
Authors: Wilkinson C. S. 
Published: February 2011

Abstract
The friction of tread compounds on ice is affected to a great extent by the methods and conditions of measurement. As velocity of sliding is increased from zero to about two centimeters per second, there is an increase in friction, after which there is a gradual decrease with further increase of velocity. Static friction depends on the length of time the sample is in stationary contact with the ice, and is of little practical significance. Of the test variables studied, temperature has the greatest influence. At the lowest temperatures used, −30 to −40° C, the coefficient was approximately double that usually observed slightly below the freezing point. Friction was also found to vary with pressure. An empirical equation of the form,k=C1−C2 log P, was found to fit results in many cases. Minor differences were noted, resulting from changes in sample shape and surface treatment. When testing conditions were held constant, it was found that several variables in the samples themselves affected the friction. The type of polymer used had a definite effect. Of about equal importance was hardness. In similar compounds the softer samples had higher coefficients of friction. The unusual frictional characteristics of rubber sliding on ice may be explained by taking into account the water layer formed between the sliding surfaces. The melting of ice to form this water layer takes place because of the heat generated by the work done against friction. The friction itself is believed to be caused by alternate welding and breaking of junctions between surface asperities. Although the process is initiated in part by pressure melting, that phenomenon has only minor importance after the motion is in progress.
Diazo-Initiated Polymers. Preparation, Properties, and Evaluation
Authors: Willis J. M. , Alliger Glen , Johnson B. L. , Otto W. M. 
Published: February 2011

Abstract
Throughout the great majority of the many investigations on rubberlike synthetic polymers, the initiators employed have been peroxides, either water-soluble (potassium persulfate being the chief example) or oil-soluble, such as benzoyl peroxide or diisopropylbenzene monohydroperoxide. The most notable departure from these initiators has been the use of the diazothio ethers, 4-methoxybenzenediazomercapto-2-naphthalene (MDN) and 4-methylbenzenediazomercapto-2-naphthalene (TDN). These materials have proved to be suitable initiators and also to have some activity as modifiers. However, their possibilities have been explored principally at a polymerization temperature of 41° F. Thus, the field of initiators has been subject to less widespread investigation than most of the other variables in a typical synthetic rubber recipe. The purpose of the present investigation was to develop different initiators, if possible, of a type which would lead to improvement of polymer structure at 122° F. It was felt from the outset that diazo-type compounds offered the best possibilities for development along these lines. During a preliminary survey of these materials, the object was to find examples which did not have the two disadvantages of the diazothio ethers—high cost and low stability. The use of diazo-type compounds as polymerization initiators has been known for many years. The work of Buizov on the polymerization of butadiene with diazoaminobenzene is an example of this. A number of patents have been issued relating to the use of diazo compounds in general as polymerization initiators or activators. These patents, however, were directed toward improving the rate of polymerization, and did not indicate any outstanding improvement in polymer properties. After detailed study of the properties and reactions of diazo materials in general, stabilized salts of diazotized aromatic amines were selected as the specific type of compound with the greatest chance of success. The program was begun with the laboratory preparation and evaluation of diazo salts.
Study of the Viscoelastic Behavior and Molecular Weight Distribution of Polyisobutylene
Authors: Van Holde Kensal E. , Williams J. W. 
Published: February 2011

Abstract
The viscoelastic behavior of linear high polymers has commanded considerable attention in recent years. The very thorough studies by Fox and Flory of the melt viscosity of polystyrene and polyisobutylene, the stress relaxation experiments of Tobolsky and coworkers, and dynamic-mechanical studies by Ferry have contributed greatly to our knowledge of the mechanical behavior of these interesting substances. However, there are many facets of this subject which have not received thorough experimental investigation. In particular, there has been no detailed study of the effect of molecular weight and polydispersity on the elastic behavior of viscoelastic materials. It was felt, therefore, that a study of the viscoelastic behavior of a series of very carefully characterized samples of a representative linear high polymer would contribute substantially to the understanding of this subject. The polymer chosen was polyisobutylene, which displays both flow and elastic behavior at room temperatures.
Effect of the Concentration and Nature of the Emulsifying Agent on the State of Dispersion of Latexes
Authors: Yurzhenko A. I. , Gusyakov V. P. 
Published: February 2011

Abstract
Yurzhenko and Mintz were the first to show that, in the process of emulsion polymerization, the size of the polymeric particles in the latex increases regularly. This phenomenon is in complete accord with the theory that, in the particular case of 1,3-butadiene, polymerization proceeds to a major extent in the micelles of the emulsifying agent. A systematic study of the state of dispersion of synthetic latexes in its relation to the experimental conditions and the processes taking place during their formation would appear to be of great potential value in the study of the mechanism of emulsion polymerization. The present authors have studied the degree of dispersion of synthetic latexes prepared in the laboratory, with different concentrations and types of emulsifying agents. Work in this field has not been reported in the scientific literature, although, in studies of emulsion polymerization, data on the state of dispersion of latexes under certain conditions have been reported. In the present work, the effects of other factors, such as the nature of the monomer, initiator, and electrolytes, on the size of the latex particles and the characteristics of these particles also were studied.
Rubber Evaluations with Instron Testing Machine
Authors: Gehman S. D. , Clifford R. P. 
Published: February 2011

Abstract
The principles of operation incorporated in the Instron machine give it wide distinctive fields of usefulness in a rubber testing or rubber research laboratory. Its principal limitations for rubber testing are usually associated with unique conditions which occur in rubber testing as contrasted to the testing of other materials. The results available should encourage improvements in the equipment and procedures in general use for rubber stress-strain evaluations.
Studies of the Vulcanization of Rubber. III. Kinetics of Change of Tensile Strength of Natural Rubber during Vulcanization
Authors: Dogadkin B. , Karmin B. , Golberg I. 
Published: February 2011

Abstract
1. It is shown that the tensile strength of vulcanized butadiene-styrene rubber is a linear function of the plasticity of the original material. 2. Proceeding from concepts of the presence during vulcanization of a number of opposing processes of structure formation and destruction, both of which influence the molecular weight of the rubber, a general equation is derived which expresses the kinetics of the change of tensile strength of a vulcanizate. 3. Experimental material is offered which proves the applicability of the proposed equation to the representation of the kinetics of vulcanization of mixtures of natural rubber containing relatively small sulfur contents, i.e., up to 3 per cent.
Oxidation and Antioxidant Action in Rubber Vulcanizates
Authors: Shelton J. Reid , Cox William L. 
Published: February 2011

Abstract
The variation of rate of oxygen absorption in the constant rate stage with oxygen concentration involves both a square-root and a first-power term for most rubber vulcanizates, although the latter term may be negligible in some cases. A mechanism of oxidation and antioxidant action has been postulated which is consistent with the observed behavior, and which indicates that the antioxidant may function in at least four ways, some beneficial and some harmful. Direct oxygen attack on the antioxidant may produce radicals capable of initiating oxidation chains. Initiation by this mechanism appears to be more important with amine antioxidants than with phenols. The antioxidant may participate in the propagation stage by a chain-transfer mechanism. While this effect alone for a typical antioxidant would probably have only a small effect on the over-all rate of oxidation, it might also affect in a favorable way the secondary reactions which determine changes in physical properties. Amines also appear to be more inclined to chain transfer than are phenols. Termination by a chain-stopping mechanism is one way in which antioxidants retard oxidation. Phenols appear to be more efficient than amines in this connection. Destruction of peroxide by antioxidant-induced decomposition to stable products reduces initiation by peroxide decomposition, and is thus another important mechanism of antioxidant action. The amines are more efficient than the phenols in this regard, and the presence of carbon black is essential for the amines to exhibit their maximum effectiveness. Carbon black is known to promote the decomposition of peroxide to free radicals, but in the presence of amine antioxidants it also promotes the decomposition to stable products. This dual effect of carbon black results in a reversal of effectiveness of amines and phenols in gum and black stocks. The phenols (which function best as chain stoppers) are more effective in the gum stocks; the amines (which function best by reducing peroxide initiation by directing the decomposition to stable products) are more effective in the black stocks.
Oxidation of Unvulcanized Rubber. Effect of Carbon Black
Authors: Lyon F. , Burgess K. A. , Sweitzer C. W. 
Published: February 2011

Abstract
The effect of carbon black on the autocatalytic stage of oxidation of unvulcanized rubber is shown to be specific for the type of carbon, the reaction conditions, and the polymer. Carbon black is an effective antioxidant for cold rubber when the rubber is heated in air or oxygen. The effectiveness of carbon in inhibiting oxidation increases as the volatile content of the carbon increases. The special case of low loadings of highly oxidized carbons, which completely repress gelation during Banbury mixing, is of particular interest. The opposite behavior of carbon black during rubber gelation is observed when benzoyl peroxide is used as catalyst. With cold rubber, carbon black promotes gelation, while with natural rubber increased scission results. Alteration of any one of these variables produces profound changes in the course and extent of the oxidation reactions.
Measuring Wet-Gel Strength of Coagulant-Dipped Films. Paper Dip Method
Authors: Medalia A. I. , Townsend H. B. , Grover H. N. 
Published: February 2011

Abstract
A property of latex which is considered of fundamental importance in the latex industry is the so-called wet gel strength. This term connotes the tensile strength of the freshly set film, but hitherto there has been no adequate method of measurement of this property, since the film is so weak that it cannot readily be removed from the surface on which it is deposited. The present method is based on the use of absorbent paper of low wet strength, impregnated with calcium nitrate, as a base for the deposition of a latex film. The strip of paper, which may be of a dumbbell shape, is dipped for 30 seconds and then removed from the latex, together with the adhering coagulant dipped film. This film is rinsed in water and then mounted on a special tensile testing machine designed for high elongation and low tensile strength. Elongation and tensile strength are measured at a standard rate of jaw separation of 20 inches per minute. These properties have been studied, using natural and various synthetic latexes. The effects of prevulcanization, compounding, and dilution of these latexes have been determined. Tensile properties of the film from a given latex have also been measured as a function of the time and conditions of drying of the film after deposition.
Vulcanization Structures and Their Influence on the Heat Resistance and Fatigue of Rubber
Authors: Dogadkin B. A. , Tarasova Z. N. 
Published: February 2011

Abstract
(1) The phenomenon of stress relaxation in vulcanizates, due to thermal decomposition of the vulcanization structures, is discussed. The process follows the equation: σt=σ0⋅e−kt, where k is the kinetic constant of decomposition of the vulcanization structures, and therefore can serve as a measure of the heat resistance of a vulcanizate. (2) The amounts of polysulfide and disulfide bonds in various vulcanizates were determined. (3) It is established that the heat resistance of vulcanizates depends on the total quantity and also on the proportions of bonds of the type : R1—C—C—R2, R1—C—S—C—R2, R1—C—S—S—C—R3, and R1—C—Sn—R2. (4) It is shown that the relative contents of various vulcanization structures depends on the type of rubber and on the nature of the vulcanizing group. Thus, vulcanizates with tetramethylthiuram disulfide do not contain any polysulfide bonds, whereas vulcanizates with elemental sulfur (without accelerator) contain predominantly polysulfide bonds. (5) It is established that recombination of the radicals formed during thermal decomposition of a vulcanizate leads to the formation of both intramolecular bonds and new stable bridge bonds. (6) It is suggested that thermal decomposition of sulfur bridges is one of the causes of the phenomenon of a vulcanization optimum (reversion). (7) A relation is established between the nature of vulcanization structures and the resistance of vulcanizates to repeated deformation.
The Microstructure of Diene Polymers. III. Polyisoprenes and Polybutadienes Prepared with Cationic Catalysts
Authors: Richardson W. S. 
Published: February 2011

Abstract
It is well known that catalysts of the Friedel-Crafts type cause the polymerization of diene monomers and that this reaction is ionic rather than free radical in nature. It is also known that such catalysts cause diene polymers to isomerize (cyclize), and one may expect that the polymerization and isomerization reactions will occur simultaneously during the preparation of polymers with these catalysts. While considerable information is available describing methods of preparation and the general properties of such polymers, there seem to be few or no data concerning their microstructures. It is the purpose of this paper to present the results of such structural studies (obtained from infrared spectra) on seven polyisoprenes and three polybutadienes, prepared at temperatures between 30° and −78° C, with various cationic catalysts.
Properties of Hard Rubber. XVII. Influence of Rubber-Sulfur Ratio and Vulcanization Time on the Properties of Pure Rubber-Sulfur Compositions. (3) Swelling, Water Absorption, Aging, and a General Discussion of Results
Authors: Church H. F. , Daynes H. A. 
Published: February 2011

Abstract
(a) Method of Test.—The materials selected were A, 5 hours, and C, 3.75 hours. It was not possible to include sufficient samples to show the separate effects of varying vulcanization time and rubber-sulfur ratio, but the samples show the effect of a considerable difference in combined sulfur, having vulcanization coefficients of 49.5 and 38.7, respectively. To show the dependence of swelling on the nature of the liquid, tests were carried out in twenty different liquids selected to represent various chemical types. Each piece of hard rubber, measuring 20 × 19 × 5.5 mm., was placed in a stoppered bottle with about 40 cc. of the liquid under examination. The bottle was kept in a thermostat at 34° C and shielded from light. The test-piece was then weighed after various periods of immersion ranging from 4 to 4000 hours. The absorption of liquid after each period was calculated from the increase in weight and expressed by the volume of liquid absorbed as a percentage of the initial volume of the test-piece. (b) Results.—No sign of solution of the rubber-sulfur compound was observed, but in certain cases, where swelling was rapid, cracking occurred. In three cases this took place before the first weighing could be made. Full-time swelling curves were obtained, but as most of the liquids are not likely to come into regular contact with hard rubber in electrical service, figures are given in Table 19 for one long and one short period only. In this table, swelling less than 1 per cent is shown as zero. Closer readings for certain liquids of very low absorption are shown in Table 20.
Properties of Hard Rubber. XVIII. Action of Hydrocarbon Oils at High Temperatures (Part XV of Swelling of Rubber)
Authors: Scott J. R. 
Published: February 2011

Abstract
It has already been shown that liquids consisting essentially of aliphatic hydrocarbons, e.g., petroleum ether, paraffin, and transformer oil, had practically no swelling action at 34° C on two samples of hard rubber composed of rubber and sulfur only. Hard rubber shows a pronounced change in properties at temperatures above a critical value (“yield temperature”) in the neighborhood of 50° –80° C, the most noticeable effect being that it becomes much softer and more susceptible to plastic flow. It seemed likely, therefore, that the swelling action of liquids such as those mentioned above might be much greater at temperatures above this critical value. This view was strengthened by the statement of Dunton and Muir that hard rubber is “badly attacked” by immersion for 7 days in “hot” transormer oil. As no data appear to have been published on the effect of temperature on the swelling of hard rubber, experiments were made to examine this effect. Details of the hard rubber samples used are as follows.
The Vulcanization of Rubber with Phenol-Formaldehyde Derivatives. Inapplicability of the Chromane Theory
Authors: Van Der Meer S. 
Published: February 2011

Abstract
The chemistry of phenol-formaldehyde resins has developed enormously since 1938. Zinke, von Euler and Hultzsch in particular have enlarged our knowledge about the constitution of resols and resites by their investigations in the complicated field of resol hardening. In addition, reactions between hydroxyphenols and unsaturated compounds have been studied. Hultzsch proved the formation of a chromane ring system by heating an unsaturated hydrocarbon with a hydroxyphenol. Later Greth described the reaction between resols and fat oils as an analogous one, also in these cases supposing the formation of chromane derivatives. According to the latter two main reactions lead to the formation of macromolecular compounds: (1) the formation of chromane rings between the resol and the unsaturated compound; (2) the formation of intermolecular oxygen bonds between the methoxy groups of the hydroxyphenols and resols. It seemed reasonable to explain the vulcanization of rubber with resols and dihydroxyphenols by this chromane theory. However, it is necessary first of all to have a clear idea of the various possibilities which may be involved. Only after this will it be possible to decide whether the chromane theory may be applied to vulcanization with phenol-formaldehyde derivatives as well.