bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Determination of Crystallinity in Deformed Rubber
Authors: Nyburg S. C. 
Published: February 2011

Abstract
A vulcanized natural rubber has been deformed in simple extension and in pure shear and the resulting diminution of x-ray intensity of the amorphous halo used as a measure of crystallinity. The effect of mode of deformation and attempts to reach equilibrium states by heat treatment at constant deformation are described. The values obtained for simple extension are in accord with those reported by Goppel and not with those of Field. The degree of crystallinity is greater in pure shear than in simple extension at the same principal extension ratio. Corrected values for the orientation of crystalline regions have been obtained, and a comparison is made between volume changes and x-ray measurements for simple extension.
Dynamic Mechanical Properties of a Number of Elastomers and Related Polymers from 4 to 250° K
Authors: Morgan R. J. , Nielsen L. E. , Buchdahl R. 
Published: February 2011

Abstract
Young's modulus and mechanical damping have been measured down to 4° K for cis- and trans-polybutadienes, cis- and trans-polyisoprenes, butyl rubber, and random SBR copolymers. Trans-polybutadiene has two large damping peaks below Tg, trans-polyisoprene one peak, while the cis-polymers and butyl rubber show either no damping peaks or only very small ones below Tg. The low-temperature damping peaks of the trans-polymers might be explained by a type of crankshaft motion and by a special motion of the trans-monomeric unit which involves a simultaneous vibration and bond angle deformation. The high Young's moduli of the polybutadienes compared to the polyisoprenes and the SBR copolymers are explained by the good molecular packing of the polybutadienes.
Influence of Chemical Structure on the Dynamic Properties of Sulfur-Vulcanized, Carbon Black-Reinforced Natural Rubber
Authors: Doyle G. M. , Humphreys R. E. , Russell R. M. 
Published: February 2011

Abstract
A comparison is made of the composition and properties of the different rubber vulcanizate networks obtained by varying the ratio of sulfur to sulfenamide accelerator and by the thermal aging of vulcanizates containing predominantly polysulfide crosslinks. It is concluded that the changes in network structure which can take place, for example, during the service life of natural rubber tires are not the direct cause of failures of the type associated with rubber fatigue at high temperatures. However, a reduction in the total number of crosslinks can accelerate failure by increasing the amount of heat generated during flexing. More stable networks giving improved resistance to fatigue at high operating temperatures are obtained by the use of higher ratios of accelerator to sulfur than are conventionally employed.
Evaluation of the Thermal Stress Relaxation Method for the Estimation of Polysulfidic Crosslinks in Natural Rubber Vulcanizates
Authors: Farmer J. H. , Stuckey J. E. 
Published: February 2011

Abstract
The variation of the polysulfidic crosslink content of a natural rubber vulcanizate during cure has been determined from thermal stress relaxation data obtained using a Monsanto Rheometer and the results have been compared with those obtained by chemical probe analysis. No correlation could be found. Attempts to isolate the relaxation due solely to polysulfide crosslink interchange gave no better agreement and it is concluded that competing maturing reactions prevent such a resolution. The first order rate constant for the fast relaxation attributed to polysulfide crosslink exchange reactions has been found to vary in a linear manner with the total crosslink density of the vulcanizates.
Influence of Vibrations on the Viscoelastic Behavior of Monodisperse Polybutadienes
Authors: Vinogradov G. V. , Yanovsky Yu G. , Isayev A. I. , Shatalov V. P. , Shalganova V. G. 
Published: February 2011

Abstract
The viscoelastic behavior of monodisperse polybutadienes is studied at different amplitudes of cyclic deformation. The concept of initial relaxation spectrum is introduced, this spectrum corresponding to small amplitudes. Under the action of high amplitudes the relaxation spectrum changed. This changed-effective spectrum can be calculated by means of the linear theory of viscoelasticity. The initial spectra of monodisperse polybutadienes have maxima. Under the action of high amplitudes the long-time parts of the spectra are truncated and the maxima shift into the short-time regions. There is an unambiguous correspondence between the amplitude of the deformation rate on cyclic deformation and the rate of shear on continuous deformation. It is shown that the length of the high-elasticity plateau, estimated on a logarithmic scale of relaxation times, and the maximum relaxation times of polybutadienes, as well as their initial Newtonian viscosities are dependent on molecular weight to a power of 3.6. The apparent viscosity is calculated, making use of the approximate initial relaxation spectrum concept, the law of change of its long-time boundary with the shear rate, and the commonly known relation of the linear theory of viscoelasticity. The results of these calculations were found to agree approximately with the data obtained under conditions of continuous deformation.
On the Linear Constitutive Equations of Transversely Isotropic Incompressible Elastic Materials
Authors: Demiray H. , Levinson M. 
Published: February 2011

Abstract
The linear constitutive equations of a transversely isotropic, incompressible, elastic material are derived in this paper as a limiting case of the constitutive equations for the corresponding compressible materials. These equations should be appropriate for the stress analysis of products fabricated from certain laminated, reinforced rubber composites. Some details of a problem concerned with the stress concentration around a circular hole are also given.
Stimulation of Latex Flow in Hevea Brasiliensis by 4-Amino—3,5,6-Trichloropicolinic Acid and 2-Chloroethanephosphonic Acid
Authors: Abraham P. D. , Wycherley P. R. , Pakianathan S. W. 
Published: February 2011

Abstract
Application of 4-amino—3,5,6-trichloropicolinic acid, alone or in mixtures with 2,4,5-T, gave larger and more persistent yield responses than application of 2,4,5-T alone in one experiment, but this was not confirmed in another. One morphactin was moderately effective but another was ineffective. N-dimethylamino-succinamic acid did not stimulate longer flow or give larger yields. Acetylene, ethylene, halogenoparaffins and 2-chloroethanephosphonic acid (which releases ethylene in plant tissues) were all effective in prolonging flow and increasing yields. All effective non-gaseous stimulants of latex flow seemed to have one common feature, namely, production of ethylene.
Properties of Poly(Alkylene Oxide) Elastomers
Authors: Hsieh H. L. , Wright R. F. 
Published: February 2011

Abstract
The catalyst comprised of triisobutylaluminum, zinc acetylacetonate, and water was used to prepare homopolymer of epichlorohydrin; copolymers of epichlorohydrin with propylene oxide, ethylene oxide, and allyl glycidyl ether; and terpolymers of epichlorohydrin, propylene oxide, and allyl glycidyl ether and of epichlorohydrin, ethylene oxide, and allyl glycidyl ether. The vulcanizates of these rubbers provide variations of stress-strain and dynamic properties, freeze point, hardness, and solvent resistance depending on the type and amount of comonomer. In general, these rubbers have excellent heat, ozone, and oxidation resistance as well as oil and solvent resistance.
Equation-of-State Parameters for Poly(Dimethylsiloxane)
Authors: Shih Hsiang , Flory P. J. 
Published: February 2011

Abstract
The thermal expansivity α=V−1(∂V/∂T)p and thermal pressure coefficient γ=(∂p/∂T)v for poly(dimethylsiloxane) (PDMS), mol wt ≈ 105, have been determined accurately over the temperature ranges 20–207 and 24–161°, respectively. Characteristic parameters ν*, T*, and p* calculated from these results are compared with those for other polymers and for low molecular weight liquids. For PDMS, α is much larger and γ much smaller than for any other polymer. The characteristic pressure p* appears to be a more reliable index of the intermolecular energy than the cohesive energy density for this purpose. It is approximately the same for a polymer as for corresponding low molecular weight liquids. For PDMS and HMDS (hexamethyldisiloxane) p* assumes exceptionally low values of 341 and 358 J cm−3, respectively, which are duplicated only by the fluorocarbons (p* ≈ 360 J cm−3).
Study of Configurational Sequence Structures of Poly(Butadiene)s by Carbon-13 Proton Decoupled Fourier Transform Nuclear Magnetic Resonance Spectroscopy
Authors: Alaki Yasuhide , Yoshimoto Toshio , Imanari Mamoru , Takeuchi Makoto 
Published: February 2011

Abstract
Carbon-13 proton nuclear magnetic resonance (NMR) of poly(butadiene) s consisting of various ratios of cis-1,4-, trans-1,4- and 1,2-structures were measured by the pulsed Fourier transform NMR method. The spectra of poly(butadiene)s with two or three kinds of butadiene configurations show several new signals which were not observed for homopolymers comprising merely one kind of butadiene configuration. All of these peaks are ascribed to the carbons linked by different kinds of configurations. From these results, the configurational sequence structure of butadiene units in polymer chains has been revealed.
Comparisons of the Carbon-13 Nuclear Magnetic Resonance Spectra of Some Solid Cis- and Trans-Poly(Isoprene)S
Authors: Schaefer Jacob 
Published: February 2011

Abstract
Fourier transforms have been obtained of the 1H and 2H simultaneously noise-decoupled, natural-abundance, 22.6-MHz 13C free-induction decays of solid cis- and trans-poly (isoprene), cis-poly(isoprene-з-d1), and carbon-black-filled cis-poly (isoprene). Carbon-13 line widths and Overhauser enhancements have been measured from the phase-corrected normal and selectively saturated absorption spectra, and spin-lattice relaxation times measured from partially relaxed Fourier transform absorption spectra. The spin-lattice relaxation times and Overhauser enhancements of the individual carbons of the amorphous part of trans-poly (isoprene) are all greater than those of the corresponding carbons of cis-poly (isoprene), and, excluding the deuterated carbon, of cis-poly (isoprene-з-d1). These spin-lattice relaxation times are interpreted in terms of a dipolar relaxation mechanism modulated by the segmental motion of the chain. The greater relative segmental flexibility of the trans-poly (isoprene) chain leads to longer spin-lattice relaxation times. The flexibility of the trans chain also permits more of its segmental motions to satisfy the extreme narrowing conditions, and this leads to the larger observed Overhauser enhancement. The various spin-lattice relaxation times of the individual carbons of cis-poly (isoprene) are not noticeably affected by the addition of carbon black. However, the 13C line widths are affected by the filler. The line widths of individual carbons of the carbon-black-filled cis-poly (isoprene) are greater than those of ordinary cis-poly (isoprene) by factors of 5–10. The broadening is different for different carbons. These results are interpreted in terms of the exclusion by the filler of the polymer from some spatial orientations leading to only partial motional narrowing of the NMR lines. Even in the absence of a filler, factors such as chain entanglements can prevent total isotropic motional narrowing of the lines. This effect can be used to explain the absence of any pronounced line narrowing upon selective deuteration of cis-poly (isoprene), even though large differences in spin-lattice relaxation times result. The 13C line widths of all of these solid, rubbery polymers are as much as a factor of 20 less than the 1H NMR line widths of the same polymers. The narrow lines are attributed to the isolation of the 13C spins from dipolar interactions with each other and with most protons.
Rubber Stocks for Improved Performance of Polyester Cord Tires
Authors: Iyengae Y. , Ryder D. F. 
Published: February 2011

Abstract
Carcass stocks were developed with acceptable properties and good adhesion to polyester tire cords after severe heat aging in laboratory tests. These stocks contained vulcanization accelerators that did not liberate amines and were based either on synthetic poly (isoprene) (IR)/butadiene/styrene (SBR) elastomer blends, as recommended in previous work, or natural rubber/SBR compounds containing an additive to inhibit the deleterious effects of amines present as impurities in NR. Standard SBR/poly (butadiene) (BR) tread stocks containing amine-free accelerators were developed to match the exceptionally long scorch time and good physical properties attained with sulfenamide accelerators normally used in such stocks. Large batches (˜400 pounds) of amine-free tread stock were processed without any scorch problems on a commercial Banbury mixer and tread extruder. With these tread stocks, containing amine-free accelerators, it is possible to build completely amine-free polyester cord tires. In a variety of wheel tests designed to assess durability under extreme conditions, 2-ply tires with cords of Dacron polyester containing amine-free tread and carcass stocks showed highly improved durability (180-440 per cent) compared to control tires made with stocks containing amines. In a wheel test simulating the running of a tire underinflated for an extended period (low pressure endurance test), tire durability increased with decreasing amine content of the rubber stocks used. In a special high temperature tire fatigue test to produce break-above-bead failures, tires combining an experimental Dacron polyester with low carboxyl content and in amine-free stocks ran 350 per cent longer than tires of standard T-68 Dacron in amine containing stocks. These tests clearly illustrated the additive benefits of combining an improved polyester with stocks having reduced amine content.
Multidetectors for Analysis of the Composition of Copolymers as a Function of Molecular Size Distribution by Steric Exclusion Chromatography
Authors: Harmon D. J. , Folt V. L. 
Published: February 2011

Abstract
Analysis of molecular size distribution of polymers by steric exclusion liquid chromatography (GPC) is well known. Problems exist, however. These problems involve copolymers and polymer blends. The objectives of the research were to develop methods of analyzing comonomer distribution in copolymers, to study the breakdown of one polymer independent of another in a polymer blend, and to obtain any additional information as might be available. The separations were performed on a Waters Model 200 Gel Permeation Chromatograph. Detectors employed were a Waters R-4 differential refractometer, a Wilks Miran-1 infrared analyzer, and a Beckman Model 144 UV photometer. Examples are given of analysis of average styrene, styrene distribution, and oil content of oil extended SBR. The data is compared with that obtained by other methods. In general the agreement is good. The ability to examine one polymer of a blend independent of the other is also demonstrated. Since elastomers are frequently used as blends, this becomes very important to such studies as milling and extrusion behavior.
Latex Maturation Studies by Low Angle Light Scattering Photometry
Authors: Myers M. E. , Wims A. M. , Lee W. R. 
Published: February 2011

Abstract
Basic information on the relationship between processing variables and the physical chemical changes occurring during the “precure” of latex blends is required for optimum process control. To obtain this type of information, the particle size and particle size distribution of a latex blend undergoing a maturation or precure treatment were monitored by low angle light scattering techniques. The absence of any measurable particle size change during precure indicates that the process is simply an initiation of crosslinking within the individual latex particles which is caused by penetration of molecular sulfur and other activators and accelerators. Volume swelling measurements were performed at intervals to determine the degree of precure attained by the blend.
The Thermal Decomposition of Amine Complexes of Zinc Bis(Dimethyl-Dithiocarbamate)
Authors: Gelling I. R. 
Published: February 2011

Abstract
It has been shown that primary alkylamine complexes of zinc bis(dimethyl-dithiocarbamate) (ZDMC) are thermally unstable. The reaction proceeds via an amine exchange reaction to yield an intermediate zinc alkyldithio-carbamate dimethyldithiocarbamate which then decomposes to give N-alkyl-N′, N′-dimethylthiourea, the dimethylammonium salt of dimethyldithio-carbamic acid, and zinc sulfide as the major products. Secondary amine complexes undergo similar initial amine exchange reactions but the new dithiocarbamates produced are stable. Tertiary amine complexes undergo neither of these reactions. These reactions can occur when zinc dithiocarbamates are used as accelerators for the vulcanization of rubber.
Bond Rupture during Ozone Cracking of Torsional Loaded Styrene-Butadiene Rubber
Authors: Devries K. L. , Moore N. B. , Williams M. L. 
Published: February 2011

Abstract
The molecular bond rupture rate during ozone attack of torsionally loaded rubber was determined from electron paramagnetic resonance (EPR) measurements. The rupture rate was successfully correlated by a Griffith-type energy balance to the strain-energy release rate in the samples. These observations substantiate the results from a similar study on tensile loading previously reported. In both cases there is a one-to-one correspondence between the rate of bond rupture (or crack growth) and the rate of energy release from the strain field and external work. A fracture energy, γn, of approximately 5×10−12 (α20 per cent) ergs per free radical formed during the cracking was experimentally determined.
Performance of Tread Compounds in Various Tire Constructions
Authors: Wilder C. R. , Haws J. R. 
Published: February 2011

Abstract
There are now three major types of construction used in passenger car tires—cross-ply (or bias), belted cross-ply, and radial. The same rubber compounds and tread designs may not always provide optimum performance in these but it was considered of interest and importance to compare the relative performance of several typical tread compounds on each type of tire. Four tread compounds were applied as retreads to four tires of each type. These were road tested over a highway route which included some rapid cornering. Two polymer systems were employed: 1. a low vinyl, 85/15 butadiene/styrene, oil-extended, solution copolymer and 2. a 40/60 blend of high-cis polybutadiene/SBR 1712. These were reinforced with N330 (HAF) and N339 type carbon blacks. Some other tire tests were also available for supporting evidence. The solution copolymer gave 8 to 12% better resistance to abrasion than the polybutadiene/SBR blend. The N339 carbon black was 10 to 15% better in wear resistance than N330 black and the best combination was 23% improved over the poorest. These relationships were affected very little by the type of tire construction and indicate that treadwear data on compounds in one type of tire may be useful to predict performance in another. Results also indicate that treads of equal composition will provide a mileage ratio of approximately 1 to 1.5 to 2 or 2.5 on cross-ply, belted cross-ply, and radial tires, respectively.
Adsorption and Calorimetric Investigations on Carbon Black Surfaces. III. Immersion Heats in Model Elastomers and Isosteric Heats of Adsorption of C-4 Hydrocarbons
Authors: Wade W. H. , Deviney M. L. , Brown W. A. , Hnoosh M. H. , Wallace D. R. 
Published: February 2011

Abstract
The heats of immersion of U-1 channel and SAF, SPF, HAF-HS, and HAF furnace blacks have been measured at 25° C in three isoprenoid olefins and four liquid elastomers of the polybutadiene, polyisoprene, and SBR types. An extensive microcalorimeter redesign was necessary because of the high viscosity of these latter fluids. The immersion heats observed with the liquid elastomers were similar to n-decane immersion heats and there was little evidence for specific interactions between these liquids and any of the blacks. The possibility that the very high structure SPF black gives slightly enhanced immersion heats should be further investigated. Since only integral immersion heats could be measured with the non-volatile liquid elastomers, the possibility is not ruled out that specific, relatively high-energy interactions may occur between the adsorbate and a very small fraction of the black surface. The similarities between the immersion heats with n-decane and the liquid elastomers indicate that almost all of the carbon black surface is accessible to the polymer segments. It appears that the rate of heat evolution may be considered a measure of the rate of attainment of intimate molecular contact between the liquid and carbon substrate. The enhancement in heat of wetting with increasing chain length over the C6 to C16 n-alkane series reported by others with a highly uniform, graphitized black was not observed with HAF. Isosteric heats of adsorption of n-butane and butene-1 at low surface coverages on several carbon blacks were calculated from adsorption isotherms obtained with a precision microgravimetric system. The isosteric heats as a function of coverage curves were typical of those expected for heterogeneous surfaces and reflected the presence of high energy physical adsorption sites at low coverages (θ&lt;0.1).
The Effect of Carbon Black Surface Properties and Structure on Rheometer Cure Behavior
Authors: Cotten G. R. 
Published: February 2011

Abstract
The cure behavior of SBR and NR compounds was examined using the Monsanto Rheometer. The three cure parameters—induction period (td), rate of crosslinking reaction (k2) and maximum increase in torque (ΔL)—were derived from the Rheometer torque curves. The data so obtained were used to calculate Westlinning's αF-values. It was shown that (1) k2 decreases with increasing total acid concentration at the carbon black surface and (2) the value of αF is related to the filler structure and the crosslink density of the rubber matrix. It was also demonstrated that the crosslink density, as measured by ΔL, is influenced by the surface chemistry of carbon black. In SBR stocks the crosslink density increases with increasing total acid concentration, while in NR compounds the reverse is true. These findings were confirmed by examining the tensile properties of regular and oxidized HAF-LS black in SBR and NR compositions. Thus the effect of carbon black surface chemistry on crosslink density can be estimated, for a given recipe, from the value of k2. An empirical relationship between the cure parameters (αF and k2) and filler structure (as measured by extrusion shrinkage) was derived and tested on a wide range of carbon blacks. This relation gives a much better correlation coefficient than the simple relation between extrusion shrinkage and αF alone. Thus by full use of the Rheometer data, the extrusion shrinkage or other structure-related properties of carbon black filled stocks can be predicted.
Electron Impact-Induced Fragmentations of 2-Benzothiazole Sulfenamides and Related Compounds. Correlation with Rubber Vulcanization Activity
Authors: Potts K. T. , Brugel E. G. , D'Amico J. J. , Morita E. 
Published: February 2011

Abstract
A correlation has been made between the activity of commercial rubber accelerators and vulcanizing agents and their mass spectral fragmentation patterns.