bluuebunny/crossref_metadata_2025_split huggingface dataset:
Storage Stability of Unvulcanized Natural, Nitrile, and GR-S Rubber Compounds
Authors: Schroeder Charles H. 
Published: February 2011

Abstract
Loss of plasticity due to interaction of polymer and loading pigment and aging can be overcome by remilling, and therefore is not serious in formulating compounds which can be remilled before use. Compounds which are sold in the unvulcanized state and cannot be remilled after aging and before use must be formulated so as to avoid loss of plasticity due to polymer and pigment interaction or from other cause shown in this paper. The factors influencing the storage stability of unvulcanized compounds both with and without curing agents have been discussed, and it has been shown that by proper formulation it is possible to produce stocks with adequate uncured storage stability.
Some Factors Influencing the Road Wear of Tires
Authors: Stiehler R. D. , Steel M. N. , Mandel J. 
Published: February 2011

Abstract
Three road tests of tires for tread wear were statistically designed. The design of test equalized the treatment of tires, and included a study of some of the factors influencing the road wear of tires in addition to the primary object of the test. Among these factors were the effects of vehicle, wheel position, day of test, climatic conditions, and length of storage. A study was made also of two methods of measurement-depth of tread grooves and weight loss. The information on these factors was obtained at no increase in cost of test. It was found that atire loses weight at essentially a constant rate, whereas, the depth of the tread grooves decreases at a declining rate, which results in a bias in the tread wear ratings. The weight method was also found to be more sensitive than the depth method. The study of the effects of vehicle and wheel positions led to the conclusion that differences in the rate of wear on different wheels do not affect the tread wear comparisons, since the rate in slow wearing positions is proportional to that in fast wearing positions, and the coefficient of variation is about the same. These results led to the conclusion that geometric rather than arithmetic averages be used in evaluating tread wear. The study of the effect of day of testing and of climatic conditions indicated that the surface temperature of the road and tire has a pronounced effect on rate of wear. Natural rubber treads containing channel black wore faster as the temperature increased, whereas, synthetic rubber tread containing furnace blacks wore faster as the temperature decreased. Other treads wore at about the same rate as the temperature changed. The effect of temperature on tread wear was greater in many instances than the effect of a lower coefficient of friction on wet roadways. Storage of tires generally increased the rate of wear; however, some treads did not wear faster after one year of storage. The object of one test was to determine the effect of type of rubber and black on tread wear. It was found that the rubber and black are mutually independent in their effects. The behavior of natural and synthetic rubbers or of channel and furnace blacks with a change in temperature made it impossible to compare them without stating the conditions of test.
Measurement of Refractive Index of Elastomers
Authors: Arnold Aurelia , Madorsky Irving , Wood Lawrence A. 
Published: February 2011

Abstract
The measurement of the refractive index of elastomers is discussed, with particular reference to GR-S rubber and the use of an Abbé type of refractometer. Detailed descriptions of the apparatus used and the procedure for GR-S rubber are given. Common sources of error are discussed and methods of minimizing these errors are given. A detailed stady has been made of the precision obtainable with GR-S polymers using the Abbé type of refractometer with an incandescent light source. It was found that the standard deviation corresponding to variability of a single random determination was 0.00007. The method has been used for several years as the basis for the determination of bound styrene in copolymers of butadiene and styrene, and is currently employed for control purposes in the government-owned synthetic rubber plants. It has also been used for determining the percentage of rubber hydrocarbon in natural rubber and for locating second-order transition temperatures.
Atmospheric Ozone—A Simple Approximate Method of Measurement
Authors: Crabtree J. , Erickson R. H. 
Published: February 2011

Abstract
In recent years the rubber industry has awakened to the significance of the minute amounts of ozone in the atmosphere as a destructive agent by virtue of its unique property of splitting stretched rubber and perhaps also of the possibility of its function as an oxidation catalyst for organic materials in general. Progress in the past has been hampered by lack of a satisfactory method of measurement at the extreme dilution encountered (0–10 parts per hundred million). Particularly does this apply because measurements must be made on the spot. The fugitive nature and high dilution of the ozone obviate any possibility of transporting samples for later measurement in the laboratory. Of the methods available, the fundamentally ideal one is by light absorption at one of the ozone absorption bands. Measurements made by European observers in this way have given values of from one to three parts ozone per 108 parts of air. An air path of three to four miles is necessary, however, and this, apart from other experimental difficulties, renders the procedure hopeless for practical application. Numerous colorimetric and fluorescence methods have been described, but none begins to approach the necessary sensitivity. Resort, therefore, has inevitably been to the classical reaction with potassium iodide, with measurement of the iodine liberated. Here the problems lie in the difficulty of presenting efficiently a very large volume of air to a small volume of reagent, and in the possible presence in the atmosphere of other oxidizing agents, e.g., peroxides—nitrogen, hydrogen, or organic. The volume problem has been solved by presenting the air to the reagent in the form of a fine spray, and apparatus has been described to accomplish this action. The hazard of other oxidizing agents is not usually present, but these can usually be frozen out in cooled traps above the boiling point of ozone. It has been claimed possible to separate the ozone by absorption on silica gel cooled in liquid oxygen and to recover it quantitatively on warming. The present authors, however, have never been able to recover more than 50 per cent of the original ozone in this way. A Russian observer could recover none.
An Improved Apparatus for Determining Moisture in Rubber by Distillation with Toluene
Authors: Tryon Max 
Published: February 2011

Abstract
An improved apparatus has been developed for the determination of water in rubber by distillation with toluene. The volume of the water collected is measured in a graduated capillary tube, which allows more precise measurement than the tapered tube formerly used. The interior of the trap and condenser is coated with a water-repellent silicone polymer to prevent water droplets from adhering to the walls and to improve the accuracy. This paper describes the construction of the apparatus and a procedure for coating its interior with the silicone polymer. A method of calibration of the trap is included in a general procedure for use of the equipment.
Water Vapor Permeability and Sorption of Hevea Latex Films
Authors: Bowler William W. 
Published: February 2011

Abstract
A considerable structural difference exists between Hevea latex films vulcanized after drying and those vulcanized in the latex state. Since these two types of films differ considerably in water vapor permeability and sorption, a careful study has been made of these phenomena. The weight of water permeating an uncompounded film was inversely proportional to the thickness of the film over a wide range of thicknesses, and directly proportional to Δp, the vapor pressure difference across the film, except at very high values of Δp. However, films cast from vulcanized latex were much more permeable to water vapor, sorbed considerably less water, and had a greater negative temperature dependence of permeability than uncompounded or dry vulcanized films. These experiments indicate that diffusion takes place in prevulcanized films by an activated diffusion through capillary holes and in dry vulcanized films by an activated diffusion through the polymer itself or the adsorption layer.
Vibration Characteristics of Tread Stocks
Authors: Gui K. E. , Wilkinson C. S. , Gehman S. D. 
Published: February 2011

Abstract
Nonlinear vibration characteristics of tread compounds, as evidenced by a dependence of modulus and internal friction on amplitude, were studied in order to reach an understanding of these unexplained phenomena in terms of plausible structural alterations which may occur in the tread compounds because of vibration. This information is interesting both for a more exact description of the deformation processes in tread compounds, and because of the necessity of dealing with the effects in any dynamic testing procedure. Nonlinear vibration characteristics are readily observed for tread stocks of both Hevea and synthetic rubbers in the mechanical range of frequencies. Experiments were undertaken to study the extent to which these effects depend on temperature, compounding variables, and type of vibration. It may be shown that the nonlinearity is not due to temperature rise from vibration, although precise measurements are complicated by the temperature rise. The effects occur for stocks reinforced with fine silica pigment, Pliolite resin, and higher loadings of pigments generally considered to be nonreinforcing, as well as for those compounded with reinforcing blacks. The pigment loading necessary for the same degree of nonlinearity increases with the pigment size. The effects are observed in unvulcanized tread stocks and occur for vibrations in both shear, compression, and tension. Measurements of the nonlinearity for tread stocks over a range of temperatures suggest that the vibration elicits structural changes in the rubber analogous to those observed in the rheology of rubber solutions and raw rubber. The nature of these changes can be interpreted by the rheological criteria of structure developed for non-Newtonian systems. Such recognized mechanisms for structural viscosity as orientation, deformation, and breaking and reforming of bonds of the flow units are useful in explaining the phenomena observed. The effects appear to be of such magnitude that they should be taken into account in any exact study of the effect of modulus on tread wear and performance.
Temperature Dependence of Dynamic Properties of Elastomers. Relaxation Distributions
Authors: Ferry John D. , Fitzgerald Edwin R. , Grandine Lester D. , Williams Malcolm L. 
Published: February 2011

Abstract
By the use of reduced variables, the temperature dependence and frequency dependence of dynamic mechanical properties of rubberlike materials can be interrelated without any arbitrary assumptions about the functional form of either The definitions of the reduced variables are based on some simple assumptions regarding the nature of relaxation processes. The real part of the reduced dynamic rigidity, plotted against the reduced frequency, gives a single composite curve for data over wide ranges of frequency and temperature; this is true also for the imaginary part of the rigidity or the dynamic viscosity. The real and imaginary parts of the rigidity, although independent measurements, are interrelated through the distribution function of relaxation times, and this relation provides a check on experimental results. First and second approximation methods of calculating the distribution function from dynamic data are given. The use of the distribution function to predict various types of time-dependent mechanical behavior is illustrated.
Correlation of Dynamic and Static Measurements on Rubberlike Materials
Authors: Andrews R. D. 
Published: February 2011

Abstract
Dynamic and static measurements of rubberlike materials can be related in terms of a generalized Maxwell model which is assumed to represent the mechanical behavior of the system, the individual characteristics of the system being expressed by the nature of the relaxation time distribution of the model. Such properties as dynamic modulus and dynamic viscosity measured in experiments involving sinusoidal vibrations and static modulus measured in experiments of relaxation of stress at constant strain can be expressed by integrals involving the distribution of relaxation times. The distribution of relaxation times can, therefore, be calculated from experimental data of this sort by suitable mathematical methods. Because of the complexity of such calculations when carried out rigorously, the use of approximate methods is often desirable. A number of useful approximate relations can be derived by investigation of the mathematical structure of the integrals relating the distribution of relaxation times to the observed properties and by examination of the behavior of certain particular relaxation time distributions. Attempts to correlate dynamic and static data on the basis of this general theory by use of the approximate relations discussed have been reasonably successful.
Nuclear Magnetic Resonance Study of Transitions in Polymers
Authors: Holroyd L. V. , Codrington R. S. , Mrowca B. A. , Guth E. 
Published: February 2011

Abstract
Nuclear magnetic resonance absorption line widths have been studied for several high polymers. The proton line widths were studied in a field of 7000 gauss and at a frequency of about 30 mc. Line widths obtained for Hevea rubber and GR-S were very narrow, indicating a large degree of “quasi-free rotation” in these materials. Vulcanization, carbon loading, copolymerization, and crystallization produced a broadening of the lines, as expected from the hindrance to internal motion introduced by these factors. Line width transitions as a function of temperature were observed for several polymers. Linear thermal expansion coefficients and specific heat vs. temperature curves have breaks in the region of line transitions for the polymers studied. Swelling of polymers with benzene produced a narrowing of the absorption line throughout the line transition and lowered the transition temperature. Vulcanization broadened the transition range and shifted it to higher temperatures. Of two closely cut fractions of polystyrene, the larger molecular-weight sample exhibited a line transition range at a higher temperature. The styrene monomer as well as the two fractions exhibited the same low-temperature line width of about 8 gauss. The line-width transitions were also studied for three butadiene-styrene copolymers at temperatures where anomalous behavior was found in dynamic measurements. The theoretical implications of these experimental results, together with a survey of other pertinent work, indicate the possibilities of the nuclear resonance method as applied to the study of high polymers in conjunction with other methods.
Breakage of Carbon-Rubber Networks by Applied Stress
Authors: Blanchard A. F. , Parkinson D. 
Published: February 2011

Abstract
The results of this investigation strongly support previous conclusions by the authors that the softening of reinforced rubber when it is stressed to moderate extensions owes little to breakdown of filler chain structure and is due primarily to rupture of attachments between the filler and the rubber molecules. This means that the stiffness of reinforced rubber is influenced greatly by the mode of attachment of filler to rubber, and the conclusion reached is that such stiffening by finely divided fillers is largely a consequence of linkages between rubber molecules formed through the filler particles by rubber-filler bonds and assisted by the presence of coherent chain structure of the filler particles themselves. The work further suggests that the linkages formed through carbon particles are of two kinds : one a relatively weak type linkage due to physical (van der Waals) attachments, the other a strong type linkage due to chemisorptive attachments which remain unbroken by stressing. The strong linkages are relatively few and have not been found with fillers other than carbon black, but the strength distribution of the weaker type does not depend on the chemical nature or type of filler, although differences are found in the total number of such relatively weak attachments. The weak linkages are substantially all broken in the course of stressing to high elongations and the stiffening at the highest elongations is a consequence of the relatively small number of strong linkages. It is to be expected that among the fully reinforcing carbon blacks, where the particle sizes of the different types are roughly equivalent, those providing the greatest number of strong linkages will have the greatest reinforcing ability, and it may be significant in this connection that HAF black vulcanizates are recognized to have better abrasion resistance than MPC vulcanizates, in keeping with a larger number of strong linkages.
Carbon Black Dispersion and Reinforcement
Authors: Dannenberg E. M. 
Published: February 2011

Abstract
Different mixing conditions were employed to obtain vulcanizates, varying only in degree of carbon black dispersion, with natural and synthetic rubbers, using a single sample of a commercial grade HAF black. Light transmittance measurements on dilute solutions of dissolved unvulcanized stocks prepared by an improved technique were used to evaluate the size of carbon black aggregates in cold GR-S and natural rubber stocks. Electron micrographs of films show the high degree of carbon black aggregation, even after prolonged mixing. A limiting degree of dispersion or a minimum aggregate size is obtained very rapidly as mixing is increased. Black incorporation and dispersion appear to take place simultaneously; a high degree of abrasion reinforcement was noted in most rubbers with mixing (less than 75 seconds) barely sufficient to incorporate the black. Carbon blacks in general respond rapidly to mixing, and the chainlike aggregates characteristic of reinforcing carbon blacks observed under the electron microscope are practically unchanged after mixing with rubber. Dispersion of carbon blacks during mixing depends on the packing and coherence of their agglomerates resulting from such factors as surface oxidation and extent of mechanical bulk densification. There is some evidence that oil-type furnace blacks disperse more easily than channel blacks. A major cause of the disappointing abrasion reinforcement with most noncarbon pigments possessing extreme fineness may be the tendency for excessively strong aggregate binding and resulting large aggregates in rubber. A striking rise in electrical resistivity was observed as the amount of mixing was increased. As the size of the aggregates did not change, the higher electrical resistivity cannot be explained by assuming better dispersion and breakdown of conductive carbon paths. Increased mixing might provide better distribution of the carbon aggregates in in the rubber matrix without change in size of aggregates.
Some Properties of Butyl Rubber-Carbon Black Systems
Authors: Ford F. P. , Gessler A. M. 
Published: February 2011

Abstract
Previous studies have shown that differences in milling conditions cause significant variations in the dispersion of SRF black in Butyl rubber. Recent work has placed such differences on a more quantitative basis. This was achieved by the interrelation of photometric, rheological, and electrical measurements. These observations revealed new phenomena involving changes in the pigment-polymer habit of sueh systems. Analysis of these phenomena has led to the conclusion that they may be interpreted as evidences of pigment-polymer association.
Cracking of Rubber and GR-S in Ozone. Effects of Temperature and Elongation
Authors: Cuthbertson G. R. , Dunnom D. D. 
Published: February 2011

Abstract
Determinations of the effects of elongation on the character of cracking in samples of rubber exposed to ozone have been reported by some of the early workers in the field. Data on some of the effects of temperature on the rate and character of cracking have not clearly shown the effects of the interaction of temperature and elongation on the character of ozone cracking. In the present study, samples of rubber, standard GR-S, and low-temperature GR-S compounds were exposed to a constant concentration of ozone for 4 hours at several elongations and temperatures. Prints were made from the exposed samples by inking the sample surface and taking an impression on paper. The rubber compound cracked at lower temperatures and elongations than either the standard or low-temperature GR-S compounds, and for each temperature there existed an elongation below which no sample cracked; this elongation is termed the cracking threshold for this temperature. The cracking threshold was found to be a function of the temperature, decreasing with increasing temperature. Although this relation is particularly difficult to treat exactly, it is possible to explain this effect on the basis of changes in ozonide film strength and ozonide stability with temperature. Studies of the effects of compounding on the cracking threshold may be of great value in designing compounds to fit the climatic conditions where they are to be used.
Static Exposure Testing of Automotive Compounds
Authors: Winkelmann H. A. 
Published: February 2011

Abstract
Deterioration of rubber products on outdoor exposure is due to the action of sunlight and ozone. Ozone cracking results when rubber is exposed under strain. The type of cracking produced by ozone is not produced by other elements or materials normally present in the atmosphere. Light-energized oxidation produces a crazed condition on the surface of the rubber, which is quite different from the effects produced by ozone. This study was undertaken to determine the factors which influence the resistance of rubber products to ozone. It was found that rubber cured under strain cracks faster than when cured at rest. Manufacturing defects, such as blisters, air traps, foreign matter, and pigment agglomerates, resulted in premature cracking. Certain manganese, copper, and iron salts had an adverse effect on ozone resistance in outdoor and accelerated exposure tests. Some dispersing agents used to make carbon black slurries for GR-S carbon black masterbatches, showed an adverse effect on weather aging. The selection of a polymer, such as natural rubber, GR-S, Neoprene, or Butyl rubber, has a marked influence on the ozone resistance of automotive rubber products. Unless a polymer is handled and compounded properly, good ozone resistance is not obtained. In outdoor exposure the effect of sunlight, ozone, heat, and water varies seasonally in Florida, California, Michigan, and Illinois. Many tests and much good judgment must be exercised in correlating accelerated and outdoor exposure tests.