bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Varying the Polymer Composition of the Cut Growth Characteristics of E/P/1,4 HD Tire Treads
Authors: Stewart Charles W. , Verbanc John J. 
Published: February 2011

Abstract
Experimental ethylene-propylene—1, 4-hexadiene polymers covering a range of compositions which possess satisfactory processing characteristics and economics have been evaluated in passenger car tires with emphasis on groove cracking. The tearing energy criterion was used in a laboratory test to correctly predict the groove cracking behavior of the tires made from these polymers. Road tests indicate that ethylene-propylene-1,4-hexadiene tripolymers containing 36%–42% propylene and 1.8%–2.2% diene exhibit resistance to cut growth and abrasion which is superior to standard SBR-BR in bias tires. Polymers containing more than 42% propylene or 2.2% diene were inferior in wear and resistance to groove cracking, but sufficient data are not available to pinpoint the reason.
Crosslinking, Filler, or Transition Constraint of Polymer Networks. II
Authors: Blanchard A. F. 
Published: February 2011

Abstract
The theory of Part I is developed by application to filler reinforcement of NR and SBR. For unswollen but prestretched networks it quantifies entire stress-strain curves and applies new concepts of extensibility and strain hardening. Constraint of swelling is expressed by a constant Ø, termed linkage reinforcement, and by an effective hard fraction Cm per cm2 of compound. For rubber-filler swelling vc the modified Flory functions F(νc) in Part I need 3% correction.
Intrinsic Linkage Reinforcement ϕ0 from Swelling Measurements of Effective Values ϕ
Authors: Blanchard A. F. 
Published: February 2011

Abstract
The writer has introduced for rubber with particulate reinforcement the concept of linkage reinforcement ϕ derived from the volume fraction v of rubber or νc of rubber-filled compound at equilibrium swelling in a solvent. Basic elastomer theory was modified to allow for the filler volume fraction C by an effective hard fraction Cm per cm3 of compound, the Flory or Flory-Rehner function F(νr) being replaced by F(νc), and the measure νc of swelling being a compound index replacing the usual νr. On this development of the basic theory, and defining linkage reinforcement ϕ as the ratio of the effective crosslinking of reinforced networks to the 1/Fo(νr) fix points of corresponding gum vulcanizates :
Radiotracer Measurements of Sulfur Diffusion in Rubbers
Authors: Mozisek M. 
Published: February 2011

Abstract
The object of measurement was the diffusion of elemental sulfur labeled with the radioisotope S in representative types of rubber. The highest values of diffusion coefficient were found in cis-1,4 polybutadiene. The lowest measured value was found for butyl rubber. The activation energy, expressing the temperature dependence of the diffusion coefficients, ranges from 4 to 10 kcal mol-1. For some rubbers studied, the activation energy is to a certain degree dependent upon temperature. The values of the diffusion coefficients and the characteristic constants for their temperature dependence are related to the mobility of the macromolecular segments.
The Influence of Precure Dilation on the Stress-Strain Properties of Ethylene-Propylene Terpolymer Networks
Authors: Kirkham M. C. 
Published: February 2011

Abstract
A study has been made of the influence of a dilating liquid, present during vulcanization, on the stress-strain behavior of EPDM vulcanizates. Stress-strain measurements performed on the vulcanizates after extraction of the dilating liquid, taken over a range of strain rates, indicate the effective absence of time-dependent behavior and suggest that a close approach to equilibrium has been achieved. From the experimental data, values of the C1 and C2 constants of the empirical Mooney-Rivlin equation were derived. It was found that both C1 and C2 decreased with increased precure dilation, C2 decreasing more rapidly than C1. The observed decrease in C2 is less than would be predicted by simple analogy with the Gaussian modulus; it is suggested that this difference might be explained by changes in network configuration and topology associated with the precure dilation.
Fluorosilicones as High Temperature Elastomers
Authors: Pierce Ogden R. , Kim Yung K. 
Published: February 2011

Abstract
Two types of fluorosilicone polymers are described, the poly(fluoroalkyl)-siloxanes and the hybrid fluorocarbon silicones. The first type, represented by the structure (CF3CH2CH2SiMeO)n exhibits good solvent resistance, thermal and oxidative stability and is commercially available in the form or rubber, sealants and fluids. The second type, is in the research stage and has demonstrated much improved stability especially under confined heating conditions.
Nucleation and Growth of Bubbles in Elastomers
Authors: Stewart Charles W. 
Published: February 2011

Abstract
The theory of homogeneous nucleation of bubbles is combined with an expression, for their rate of growth in elastomers to obtain approximate expressions for calculating the number of bubbles formed under a high degree of supersaturation. Experimental results are given for several elastomers with argon as the dissolved gas under a variety of foaming conditions. The theory adequately describes the manner in which the number of bubbles formed depends on the temperature, surface tension of the polymer, and permeability of the dissolved gas.
Interrelation between Data from Different Physical Tests
Authors: Ninomya Kazuhiko , Furuta Isao 
Published: February 2011

Abstract
Rubber maintains its special mechanical characteristics such as low modulus of elasticity, high elasticity, relatively large shock absorbing power, tensile strength, and others over a wide temperature range. Most products made of rubber are used where those outstanding characteristics are necessary. Thus mechanical properties are generally considered to be some of the most important features in evaluating the quality of rubber products, and consequently are related to the majority of rubber testing standards. Although the present testing standards are fairly well organized, particularly in listing the essential aspects of performance for various rubber products during service, one may conclude after inspection that they are not still satisfactory enough in some respects. There are no general and quantitative rules established for the interrelation between the data from different items in physical tests of the present standards, though everyone knows from experience that they generally depend upon each other to some extent. This may be considerably important in practice when one would try to balance various necessary aspects of performance by changing the compounding and/or curing recipe. For the mechanical behavior of substances, it is a principle that the response consists of two independent factors; namely the excitation and the material factors. The object in the evaluation of the quality is always the response of the product and the judgment is given after comparing the real response with that expected or desired for the purpose. The service and/or the processing conditions provide the details of the excitation factor, whereas the material factor may correspond, in a sense, to fundamental physical properties. Similarly in laboratory physical tests, the testing condition provides the excitation factor and the object in the evaluation is always the response. Then, as can readily be expected, some of the measures defined for separate items in the present standards differ from each other only by their excitation factors. Thus they are interrelated with each other through their mutual material factors. This paper outlines the results obtained so far on this sort of problem by the application of polymer rheology.
Thermodynamic Properties of Natural Rubber and Isoprene
Authors: Warfield R. W. , Petree M. C. 
Published: February 2011

Abstract
Using published specific heat data, the entropy, enthalpy, and Gibbs free energy of natural rubber (NR) have been calculated over the temperature range 0 to 320° K. The thermodynamic function Cp/T as a function of T calculated for NR exhibits a maximum at 50° K and another maximum at 210° K, which is associated with the glass transition. The number of classically vibrating units per repeating unit of NR is 6.61 at 300° K. These functions have also been calculated for isoprene over the temperature range 0 to 300° K. At 298.16° K the entropy of polymerization was found to be 24.00 cal mole−1deg−1 and the free energy of polymerization − 10.7 kcal/mole.
Polymer/Solvent Interaction Parameters
Authors: Sheehan C. J. , Bisio A. L. 
Published: February 2011

Abstract
Solutions in which one of the components is a high polymer and the other component is a small-molecule solvent behave in a markedly different manner than do solutions of low molecular weight components. For example, the latter obey Raoult's law if the heat of mixing is negligible; however, many polymer solutions show pronounced deviation from ideality even at concentrations of one percent or less (Figures 1–7). These deviations are due to enthalpy and entropy effects which arise from large differences in size between solvent and solute molecules. Ability to predict the solubility characteristics of polymer/solvent systems, and to calculate values of the colligative properties of such systems, is important in engineering studies of polymer processes. This paper presents a compilation of data which can be used in conjunction with the Flory-Huggins theory of polymer solutions to predict properties of polymer solutions. A method is given for predicting polymer/solvent interaction parameters (μ) for systems for which experimental data are not available. Also included is a comparison between the proposed method and two other semiempirical methods for predicting μ.
Conformation of Stereoregular Polydienes in the Crystal State
Authors: Corradini Paolo 
Published: February 2011

Abstract
The first synthetic polymer from a diene for which stereoregularity was proved was poly(2-chloro-butadiene). Two stereoregular polymers of isoprene, synthesized by living organisms, were known before: gutta-percha and natural rubber. The crystal structure of all these polymers was established in 1942 by Bunn. After the discovery of Ziegler-Natta catalysts, many stereoregular polymers of dienes were prepared. The first, polybutadiene with 1,1-trans enchainment, was described originally in 1955. Subsequently, between 1955 and 1957, the crystal structures of all the stereoregular isomers of polybutadiene were elucidated. It is now possible to make a sufficiently comprehensive picture of the chain constitution, configuration, and conformation of a great number of stereoregular polymers of dienes.
Progressive Oxidation of Selected Particles of Carbon Black: Further Evidence for a New Microstructural Model
Authors: Heckman F. A. , Harling D. F. 
Published: February 2011

Abstract
A new technique is described for following the effects of successive increments of oxidative attack upon the same particles of carbon black. Oxidation was carried out under controlled conditions outside of the microscope, followed by electron micrography of selected grid areas. Electron micrographs show that normal thermal and furnace blacks generally oxidize from the inside out, forming capsules of unchanged external dimensions. Differences in rate of oxidation of individual particles are observed with thermal blacks; these rates are, however, independent of particle size. In agreement with earlier evidence, graphitized thermal blacks oxidize from the outside in. Strong support is given for a new “concentric crystallite” model of carbon black microstructure. On the basis of this model, slippage of rubber molecules on the surface of carbon black can be readily understood.
Temperature and Rate Effects on Crystalline Transitions in cis-1,4-Polybutadiene as Measured by DTA
Authors: Collins Edward A. , Chandler Lyle A. 
Published: February 2011

Abstract
The crystallization temperature, Tc, and the crystalline melting point, Tm, of cis-polybutadiene are strongly affected by the rate of sample cooling and heating. Cooling at rates of five to several hundred °C/min and subsequent heating at rates less than about 20 °C/min results in two distinct crystalline melting peaks. Outside this range of cooling and heating a single crystalline melting peak is observed. One of the peaks is at —9° C, which is the value generally reported in the literature, while the second peak was found to decrease with increasing cooling rate to a value of —35° C for a cooling rate of about 200 °C/min. When the cooling rates are increased, the crystallization temperature is also observed to decrease. The lowest value of Tc detected was — 61° C, at a cooling rate of 65 °C/min. This is in contrast to the literature value of — 35° C. These data are interpreted in terms of the rate processes of crystallization reported by Wood and Bekkedahl on natural rubber.
A Critical Evaluation of Infrared Methods for Determination of the E/P Ratio of Ethylene Propylene Rubbers
Authors: Corish P. J. , Tunnicliffe M. E. 
Published: February 2011

Abstract
A general method of analyzing ethylene—propylene (EP) copolymers for comonomer content is needed which is applicable to all types of copolymers: random copolymers (I), … EPEEPEPPEPEEE …; alternating copolymers (III), … EPEPEPEP …, block copolymers (II), … PEE … EEPP … PPEE … EEP …; and copolymers containing random (or alternating) segments together with blocks along the chain, i.e., mixed I or III, and II. Random copolymers can contain odd-numbered sequences of CH2 groups if the EP units are head-to-tail; if some head-to-head, tail-to-tail addition occurs, then even-numbered sequences of CH2 groups will also be present (IV; structures I—IV are shown on the next page). Block copolymers sometimes have crystalline polyethylene blocks and may also contain crystalline, isotactic polypropylene blocks. Mixed copolymers are more complex in structure than either random or block copolymers considered individually. In view of the lack of chemical methods for assessment of copolymer type or even for the determination of the propylene content of a copolymer, the most fruitful approach so far has been in the application of infrared spectroscopy. As CH2 groups in the copolymers can appear in many different environments, the method of analysis should be primarily concerned with the assay of CH3 groups. Even if appreciable head-to-head, tail-to-tail addition occurs, these methyl groups are separated by two carbon atoms, and little interaction should occur. Consideration has also been given to the measurement of ethylene content or total thickness in order to complete the basis for the calculation of the E/P ratio.
Application of Pyrolysis and Gas Chromatography to Polymer Characterization
Authors: Groten Barney 
Published: February 2011

Abstract
Pyrolysis and gas chromatography has been applied to several phases of polymer analysis. Qualitative finger-printing conditions have been defined so that a large number (&gt; 150) of polymers can be identified using essentially singular pyrolysis and Chromatograph conditions. Quantitative analytical schemes have been devised for ester types in cellulosics, and for styrene content in SBR vulcanizates. Finally, the technique has been applied to elucidation of polymer microstructure, where it is useful for differentiating blends from true copolymers of ethylene and propylene, and for indicating major differences in stereoregularity in polypropylene.
Mechanical Fatigue Limit for Rubber
Authors: Lake G. J. , Lindley P. B. 
Published: February 2011

Abstract
Investigations of the dynamic cut growth behavior of vulcanized rubbers indicate that there is a minimum tearing energy at which mechanical rupture of chains occurs. The limiting value is characteristic of each vulcanizate, but is in the region of 0.05 kg/cm. The mechanical fatigue limit, below which the number of cycles to failure increases rapidly, is accurately predicted from this critical tearing energy. Characteristics of cut growth at low tearing energies, and effects of polymer, vulcanizing system, oxygen, and fillers on the critical tearing energy and fatigue limit are discussed.
Rheological Analysis of Raw Elastomers with the Multispeed Mooney Shearing Disk Viscometer
Authors: White James L. , Tokita Noboru 
Published: February 2011

Abstract
Mooney's shearing disk viscometer is one of the most important analytical research and process control instruments for elastomers. In this paper a new method is developed for computing the shear stress and shear rate of materials from data obtained on this instrument. In addition, the non-linear viscoelastic behavior of elastomers in the viscometer is analyzed with special emphasis upon normal stress effects. Experimental data for natural rubber, SBR, and polyisobutylene are discussed.
Thermal Degradation and Flammability of Urethan Polymers
Authors: Saunders J. H. , Backus J. K. 
Published: February 2011

Abstract
Polyurethans are well suited to the design of polymers for good ablation and flame-resistance. Best results in flame resistance may be expected when a composite structure is formed from an inorganic component and a self-extinguishing organic binder. The inorganic component should be present in large amounts so that the space between inorganic particles is small. For low overall density the inorganic material preferably should be foamed. The organic binder should be designed to give minimum flame spread, heat of combustion and smoke generation. The authors believe that best practical results will be achieved if the polymer gives a high melt viscosity under decomposition conditions. Those tests which rate a material as self-extinguishing because it melts and flows away from the flame are considered to be of minimum value, and offer a poor guide to the design of really good flame-resistant polymers as far as actual use is concerned. For minimum flame spread a system should be chosen that will have as little combustible gas evolved as possible, and should include a component which will provide a retarder or inhibitor for free radical decomposition mechanisms. The lowest heat of combustion will usually be favored by the incorporation of components having low hydrogen-to-carbon and low (hydrogen + carbon)-to-oxygen ratios (e.g., urethan, aromatic), and which will decompose by reactions which are not highly exothermic. While most decompositions in an oxygen atmosphere are exothermic, the dissociation of urethan groups may be assumed to be endothermic, and to this extent is favorable. The addition of an effective Lewis acid catalyst to promote carbonaceous char and reduce flammable gas formation will reduce the flame spread, and also lower the heat of combustion. Maximum char formation is desirable to serve as an insulating layer, protecting the polymer below. In addition to the Lewis acid catalyst (as may be derived from phosphorus or many of its compounds, antimony oxide, and similar acid or metal compounds) cyclic structures, especially aromatic, are favorable to char formation. These preferably should be polycyclic to minimize their chance for vaporization. Smoke generation is a function of many things, especially of the rate of burning. Hence the ideas discussed above will also be helpful in this respect. Unfortunately, some of the best structures with regard to flame spread and heat of combustion (acetylenic, aromatic) are not good from the standpoint of smoke generation. This may be because of incomplete combustion of the carbon resulting from relatively low heat of combustion. The best approach appears to be to reduce the rate of flame spread, and the heat of combustion, combined with incorporation of inorganic fillers, so that a low rate of smoke generation follows. This was achieved in Einhorn's foam-glass pellet composite of Table V.
Nitroso Rubbers
Authors: Griffis C. B. , Henry M. C. 
Published: February 2011

Abstract
The foundation for the Army's Research and Development Program is based upon the requirements of the tactical and support forces. In meeting hardware requirements and in our attempts to obtain significantly improved weaponry and equipment, we are continually searching for new materials. Many materials needed by the Army must possess special combinations of properties not required in normal commercial use. Military operations are today expected to take place at temperatures down to − 50° F. and much of our equipment is frequently exposed to even lower temperatures. Such low temperatures are found not only in the Arctic, but − 70° F. is a common summer temperature encountered by jets, missiles and their working component parts, only a few miles from the surface of the earth. At the other extreme, ground temperatures of 120° F. are common in various parts of the world and temperatures of 1,000° F. are encountered in many operating components of military equipment. During World War II, in Alaska and the Aleutians, and later in Korea, the hard lesson was learned that commercially available rubbers were not completely satisfactory for use in many military items. Fuel lines and pump diaphragms failed because of embrittlement; rubber covered cables and wires froze and broke on handling or lost electrical insulating properties; chemical warfare protective clothing and gas masks became stiff and unusable; tires developed flat spots; tubes buckled and stiffened; and many gaskets failed to perform their function. Indeed our whole bulk handling system for fuels and petroleum is dependent upon the proper functioning of rubber gaskets in couplings and in rubber fuel lines, containers and liners. In the last ten years, operational requirements for rubber have drastically changed. Nevertheless, rubber is still considered the best fabrication material for containing POL (petroleum, oil and lubricants) chemicals, whether it is a gasket or a 10,000 gallon flexible container. Rubbers are currently needed that, in addition to the already listed requirements, must also be resistant to concentrated acids, propellants and strong oxidizers. Further, it is desirable to have elastomers with high resistance to the effects of flame for use in compounds that may be exposed to short impulses of high intensity heat and radiation. Elastomers with satisfactory properties in one degree normally fail in others. To develop elastomers with the best possible combination of properties has been the goal of our elastomer research program since its inception.
Direct Observations of Polymer Molecules and Determination of their Molecular Weight
Authors: Richardson M. J. 
Published: February 2011

Abstract
An experimental investigation of the conditions necessary for the production of compact, single polymer molecules, in a form suitable for direct observation in the electron microscope, is described. Molecules are isolated by dispersing a dilute solution of the polymer as fine droplets on to a suitable substrate: ideally each droplet should contain either one or no polymer molecules. The solution is a mixture of two solvents, a good one and a poor one. Initially the good solvent predominates so that the probability of polymer aggregation is low. Preferential evaporation of the relatively volatile solvent on the substrate itself gives the poor solvent conditions needed for the formation of well-defined molecular spheres. Factors determining the choice of solvent, precipitant, and the composition of the mixture are discussed. There is little difficulty in obtaining single molecules with glassy amorphous polymers; rubbery polymers collapse and spherical molecules are formed only if the entire preparation is carried out at a temperature below that of the glass transition; crystalline polymers are not amenable to this technique. To obtain sufficient contrast the particles have to be shadowed and it is shown that, although certain dimensions are distorted by the metal coating, the shadow length faithfully represents the true particle diameter. Molecular weights, and their distribution, when of the order of a million and above, can readily be accurately determined. Conventional methods are unreliable in this region of high molecular weight.