bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Elastomeric Properties of Copolymers of Butadiene and 1,3-Pentadiene
Authors: Carbonaro A. , Zamboni V. , Novajra G. , Dall'Asta G. 
Published: February 2011

Abstract
Random copolymers of all trans structure have been prepared from butadiene and 1,3-pentadiene, in the presence of vanadium compounds and alkyl aluminum halides composed catalyst systems. Copolymers of butadiene and pentadiene, in the composition range of 30-45 weight per cent of pentadiene, are amorphous at room temperature at rest but crystallize upon stretching. Cured tread stocks show improved technological properties with respect to other synthetic diene-based elastomers. Very good processing and extrusion behavior, high tack, tear strength, and abrasion resistance are outstanding properties of the BP copolymers in the field of general purpose rubbers.
Heterogeneity of Vulcanization Networks in Rubbers
Authors: Dontsov A. A. , Anfimov B. N. , Dogadkin B. A. 
Published: February 2011

Abstract
We suppose that origination of network heterogeneity in the process of crosslinking takes place not only in the investigated cases, but with other methods of vulcanization (among them, sulfur) as a result of the polar character of the curing agents. Network heterogeneity of this type may be examined as a combination of weak and strong crosslinks, which in accord with the literature, appears as a necessary condition of the attainment of optimal physical mechanical characteristics of the vulcanizates.
A Compression Relaxometer for Rubber Materials
Authors: Stenberg B. , Jansson J. F. 
Published: February 2011

Abstract
A relaxometer which permits measurements of stress relaxation for compressed rubber samples is presented. Measurements in the temperature range 316.5 to 412.7° K show the good function of the relaxometer. The relaxometer has also been used in a study of deviations from linear viscoelastic behavior.
Long-Time Creep in a Pure-Gum Rubber Vulcanizate: Influence of Humidity and Atmospheric Oxygen
Authors: Wood L. A. , Bullman G. W. , Roth F. L. 
Published: February 2011

Abstract
The long-time creep of natural rubber cured with a conventional sulfur-accelerator recipe containing no filler can be conveniently shown near room temperature by a plot of ΔE/E1 with a double-abscissa scale, one marked in units of log t and the other in units of t. When experimental data from the present work and from previous studies reported in the literature are plotted in this manner it is noted that invariably the first scale yields a linear relation at short times and the second a linear relation at long times. The limiting linear relations just mentioned suggest the two-constant Equation (2), already proposed as a general creep equation for many materials. In the case of rubber the range of values of t investigated is from about 10 ms as studied by previous investigators to about 70 days in our work and other studies. Any significant deviations from the equation can be noted by inspection of the double-abscissa plot. We found that the equation furnished an excellent representation of almost all our experimental data up to the longest times. In one instance in our work and in a few other cases there was a prerupture increase of ΔE/E1 above the values given by the equation. This behavior can reduce somewhat the upper limit of validity of the general equation. The constants A and B can be evaluated from experimental observations of ΔE/E1 by solving two simultaneous equations obtained from the values at the longest time, at one minute, and at an intermediate time. In the present work, the constant A was essentially the same (about 2.4%/ (unit log t)) when the atmosphere surrounding the specimen was a vacuum, dry nitrogen, or dry air. The value was raised when the atmosphere was room air at 35% relative humidity and became about 4%/ (unit long t) when the air was saturated with water. The constant B was raised tenfold when the atmosphere was dry air instead of dry nitrogen. It was further increased by a factor of about 2, when the air was saturated. The value of B for the specimen in an atmosphere of stagnant room air was still greater than this by another factor of more than 2. It is possible that this atmosphere contained autocatalytic degradation products or other constituents which were removed when the air was bubbled through water or passed over CaCl2. The approximate boundaries of three different regions of time are determinable from the ratios A/B. In the first region, where t is less than 0.1(A/B), ΔE/E1 is approximately linear with log t. In the second region, where t is between 0.1(A/B) and 4.343 (A/B), ΔE/E1 is not linear with either log t or t. In the third region, where t is greater than 4.343 (A/B), ΔE/E1 is approximately linear with t. A fourth region of anomalous increase preceding rupture is sometimes found, especially when B is large.
Network Formation and Reinforcement Studies with Terminally Brominated Polybutadiene
Authors: Edwards D. C. 
Published: February 2011

Abstract
1. It is possible to form essentially complete elastomeric network structures by the reaction of terminally functional polymers with multifunctional curative agents. The process occurs in two distinct rate steps: rapid reaction up to the region of the gel point, followed by much slower reaction of the remaining sites. 2. Reinforcement of such systems with carbon black, to provide strength properties similar to analogous conventional elastomers, is possible. Such reinforcement occurs in the absence of heat and of free-radical processes normally associated with the mastication and vulcanization of rubber. 3. Chemically inert particles (esterified silica) produce reinforcement effects similar to carbon black. When chemical interaction with the elastomer network is deliberately introduced, modulus increases and tensile strength declines. A slight degree of chemical interaction is not disadvantageous, but high levels of interaction result in severe loss of extensibility and strength.
Ground Rice-Hull Ash as a Filler for Rubber
Authors: Haxo H. E. , Mehta P. K. 
Published: February 2011

Abstract
A ground rice hull ash prepared by a new burning process has been found to be a moderately reinforcing filler for rubber. This filler, 85-90% amorphous silica and 10-15% carbon, is made by a controlled incineration process in which the bulk of the organic components of the rice hulls is removed, leaving the skeletal silica structure of the hull intact and in the amorphous state. The resultant ash is easily ground to produce fine particles, generally in the range of 0.1-2.0 μm. This filler does not adversely affect either the vulcanization characteristics or the aging of SBR, natural rubber, nitrile rubber, butyl rubber, neoprene, EPDM, and propylene oxide rubber compounds. As it is predominantly silica, it responds effectively to silane coupling agents in improving properties of the rubber compounds. It is concluded that RHA filler is a satisfactory substitute for MT black and that, in blends with blacks, it can be effectively used as a partial replacement for finer and more reinforcing blacks.
Thin-Layer Chromatographic Separations of Butadiene-Styrene Copolymers on the Basis of Composition and Molecular Weight
Authors: Kotaka T. , White J. L. 
Published: February 2011

Abstract
Experimental methods have been developed for thin-layer Chromatographic separation of butadiene-styrene copolymers according to (i) composition and (ii) molecular weight. The technique of separation according to composition is based upon exploiting the adsorption of polymers from their solutions with less polar solvents through the greater adsorptivity of the relatively polar styrene units. The specific method involved is an elution gradient procedure based upon addition of a good, relatively polar solvent for both polymers (CHCls) to the nonpolar solvent CCl4. Adsorption onto silica gel during the development increases with styrene content so that high Rf values are associated with low styrene contents. The separation method for determining molecular weight distributions is based upon using solvents of marginal solubility and involves adding a highly polar nonsolvent to an initial polar solvent which precipitates the polymer during the development. Specifically, CH3OH is used as the nonsolvent, and a CH3OH-tetrahydrofuran mixture is the initial solvent. Methods of quantitatively interpreting the tlc smears to obtain compositional heterogeneity and molecular weight distribution are described. Detailed calculations for several copolymers are included.
Quantitative Measurement of Isomer Composition in Polypentenamer Using Carbon-13 Nuclear Magnetic Resonance
Authors: Carman C. J. , Wilkes C. E. 
Published: February 2011

Abstract
Polypentenamer ((−CH2CH2CH=CHCH2−)n, is produced by the ring-opening polymerization of cyclopentene. In the past, the determination of the relative concentrations of cis and trans structure was based upon an infrared method developed for analyzing polybutadiene. However, inexact absorption coefficients and problems with band overlap left the resultant analyses open to question. Carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) seemed ideally suited for determining the isomer composition in polypentenamers. We have used 13C NMR as the primary analytical method to precisely determine the isomer composition of a series of eight polypentenamers. These results and samples will provide standards to determine infrared absorption coefficients, and thus provide a new infrared analysis. Two recently published books clearly show that the flurry of research over the past few years has firmly established 13C NMR as a valuable spectroscopic tool for the organic chemist. Its potential for establishing polymer molecular structure has equally been exciting and encouraging. The advantage of carbon-13 over proton NMR has been the dispersion of chemical shifts over a much wider range. This has meant that unique, separate NMR peaks have been obtained which describe molecules with subtle differences in molecular structure. The analytical use of 13C NMR has been suggested and used to a limited extent to quantitatively measure stereoconfiguration and monomer sequence distribution. However, no detailed investigation has been reported on precision or accuracy if 13C NMR is used as the primary analytical method for measuring polymer microstructure. As with proton NMR, measurements of peak areas are necessary to obtain quantitative analyses. Allerhand has predicted that 13C integrated intensity should be valid as a carbon count in spectra of complex molecules. Schaefer subsequently has shown that within a polymer system the carbons undergo equal nuclear Overhauser enhancement (NOE), even though the total NOE of different polymers may not be equal or maximum. Hence one can compare relative areas within a 13C NMR spectrum without fear of inadequately accounting for all of the area of a given structural feature.
Anionic Polymerization of Vinyl Monomers
Authors: Morton Maurice , Fetters Lewis J. 
Published: February 2011

Abstract
Addition polymerizations involving soluble organometallic species have received intensive attention in recent years with special reference to the type of counterion and solvent. An anionic mechanism is proposed for those systems where there is good reason to assume that the metal is strongly electropositive relative to the carbon (or other) atom at the tip of the growing chain. Hence, the metal, e.g. lithium, becomes a cation either in the free state or coupled with the growing carbanion. Under the appropriate experimental conditions, spontaneous termination is avoidable in many of those systems when one of the metals of Group I is used as the counterion. The alkali metals sodium and potassium were revealed to be polymerization initiators of isoprene in the disclosures of Matthews and Strange in 1910 and Harries in 1911. The first unambiguous report of the use of lithium in reactions with diolefins appears to be that of Ziegler and coworkers in 1934. Their work consisted of an investigation of the reaction between the alkali metals (lithium, sodium) or alkyllithium species and butadiene, isoprene, 2,3-dimethylbutadiene, or piperylene.
The Effects of Surface Chemical Interactions on the Properties of Filler-Reinforced Rubbers
Authors: Dannenberg E. M. 
Published: February 2011

Abstract
1. Heat treatment of carbon black-rubber mixtures is a method of “in process” polymer grafting which gives a definite improvement in the dynamic properties of vulcanizates. 2. The heat treatment process can be more effective if chemical promoters are used. These chemical promoters function as coupling agents between filler surface and rubber. 3. With very unreactive butyl rubber an effective interaction is produced both by the addition of chemical promoters and by the use of specially active surface-modified carbon black. 4. In normal unsaturated rubbers, surface modifications of carbon black with a wide variety of groups has shown only minimal effects on rubber-reinforcing ability. Halogenated blacks have a pronounced effect on vulcanization kinetics, giving cured vulcanizates of high crosslink density. 5. Carbon black surfaces can be deactivated by calcining at high temperatures. The loss of surface-bound hydrogen may not account for this loss in surface activity. 6. Grafting of polymers to the surface of carbon black is a new method for surface deactivation. 7. Activation of carbon black surfaces by polymer grafting or other types of surface modification has not as yet been demonstrated for normal hydrocarbon rubbers.
The Constants 2C1 and 2C2 in Phenomeno-Logical Elasticity Theory and Their Dependence on Experimental Variables
Authors: Mark J. E. 
Published: February 2011

Abstract
There has been a very large number of experimental studies of the elastic properties of amorphous polymer networks in uniaxial deformation, particularly elongation, over the past few decades. In spite of these efforts, and related theoretical investigations, major questions remain unanswered with regard to stress-strain isotherms over the range of moderate deformations. The major question in this area is the molecular basis or interpretation of the phenomenological constants 2C1 and 2C2 used to represent the experimentally observed isotherms. It is hoped that the present survey of the results of the most important of these experimental studies, particularly in regard to the effect of experimental variables on 2C1 and 2C2 will encourage additional work, leading to an unambiguous solution to this important unsolved problem in the area of rubberlike elasticity.
The Odyssey of an Invention Charles Goodyear Medal Address—1975
Authors: Bayer Otto 
Published: February 2011

Abstract
It is a special honor for me to receive the internationally acclaimed Charles Goodyear Medal for my work in the field of polyurethane chemistry. The least I can do is to express my gratitude with an acceptance speech about this subject, but this is not so easy for me as I have not mastered the English language well enough to formulate and translate my thoughts at the same time. Therefore, I must ask for your understanding while I read my English manuscript. The selection of a subject caused me a few headaches because, for many in the audience, a survey of polyurethane chemistry would just mean a repetition of well-known facts. Also, many monographs have been published in the meantime—by experts and by those who like to think they are. Furthermore, having retired seven years ago from active research, I do not want to report on the latest research developments of my former colleagues. Today, the refinement of formulations for various end uses and the development of new applications are of primary interest. For example, I am thinking of the integral-skin foam technology which makes it possible to produce parts with a completely smooth or textured surface using temperature-controlled metal molds. Such foams exhibit a density gradient across the foam which shows a transition from the noncellular skin to a low-density core. Today I would like to tell you how the discovery of polyurethane came about, a most dramatic story. You will find that here—as with many important discoveries—a new idea was not sufficient in itself. What was also needed was an enterprising and optimistic spirit, tempered by controlled self-criticism, in order to succeed in a venture which in the beginning seemed hopeless, both technically and economically. In the early years of my career I was entrusted with the management of organic research in the Leverkusen plant of the former I. G. Farben. My main fields were dyestuffs, organic intermediates, and the pertinent basic research. Although dyestuff chemistry is still my first love, I always knew that an unusual increase in demand could not be expected. New dyestuffs and dye processes could only succeed at the expense of the olders ones. I tried, therefore, to place the research emphasis in my laboratory on two subjects, namely, plant-protection chemistry and macromolecular chemistry. We succeeded in both fields. In 1935 we discovered the phosphorus insecticides (G. Schrader), which are today among the most important insecticides in the world.
Optimal Curing of Rubber Compounds with Reversion Type Cure Behavior
Authors: Han In-Su , Chung Chang-Bock , Lee Jae-Woo 
Published: February 2011

Abstract
A systematic procedure is presented for the optimal curing of rubber compounds showing reversion type cure behavior. First, a cure kinetic model is proposed that can explain the reversion and the induction period commonly found in the vulcanization of rubber compounds. The state of cure behavior is analyzed as a function of cure temperature and time on the basis of the derived kinetic model. Then, the problem of determining optimal cure temperature profile for a rubber slab in a simple cure press is addressed and formulated into a constrained dynamic optimization problem. Finally, numerical algorithms and simulation results are presented to demonstrate the proposed cure optimization procedure.
Surface Modification of Textile Tire Cords by Plasma Polymerization for Improvement of Rubber Adhesion
Authors: Luo Shijian , van Ooij Wim J. , Mäder Edith , Mai Karsten 
Published: February 2011

Abstract
Aramid cords and fibers and polyester tire cords were treated by means of plasma polymerization techniques. Coatings of plasma-polymerized pyrrole or acetylene were deposited on the surface of cords and fibers in a custom-built semi-continuous reactor operated on a pulsed DC glow discharge. The deposition conditions of the plasma-polymer coatings were varied within wide limits. The cords were tested for adhesion in rubber in a industrial pull-out test. It was found that the plasma polymer coating can significantly increase pull-out forces. Coatings deposited under low power and high pressure conditions performed better than the coatings prepared under high power and low pressure conditions. The plasma-polymerized coatings were characterized by a range of analytical techniques and the performance results are explained in a tentative model based on the molecular structure of the films. The structure was found to be strongly dependent on the deposition conditions.
Multiaxial Cyclic Response of Filled Rubber
Authors: Li C. G. , Steif P. S. 
Published: February 2011

Abstract
Cyclic response of filled rubber to simultaneous combinations of shear and extension is studied experimentally. Both in-phase (elastic) and out-of-phase (dissipative) portions of the response are measured for simple shear, uniaxial tension, and combinations of the two. As noted by other researchers, the response is nonlinear, with a strong dependence on strain amplitude. However, it is shown that the response to tension and to combinations of strains can be approximately related to the response to simple shear. Such correlations are useful in predicting the response of rubber-based components subjected to complex strain cycles when only experimental data on shear is available.
Sliding Resistance on a Constrained Rubber Layer Due to Rubber Hysteresis
Authors: Li C. G. , Steif P. S. 
Published: February 2011

Abstract
Sliding resistance of a rigid cylinder over a thin rubber layer due to rubber hysteresis is investigated. This problem underlies a model being developed for quantitatively accurate predictions of the performance of a new class of damping devices. As a full multiaxial constitutive law reflecting the amplitude-dependent behavior of filled rubbers is not available, this paper sets forth an approximate method of analysis which indirectly accounts for the material nonlinearity. Results of extensive finite element calculations are then reduced to compact material-independent forms which can be used as a universal design tool. Measurements of rolling resistance are also compared with theoretical predictions.
Methods for Predicting More Confident Lifetimes of Seals in Air Environments
Authors: Gillen Kenneth T. , Celina Mathias , Keenan Michael R. 
Published: February 2011

Abstract
We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress—relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (Ea) from 125 to 70 °C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23 °C to show that the CSR Ea likely remains unchanged when extrapolated below 70 °C, allowing more confident room temperature lifetime predictions for the butyl seal.
History of Rubber Research
Authors: Morawetz Herbert 
Published: February 2011

Abstract
After the discovery of the tapping of Hevea rubber trees in the middle of the eighteenth century and early technological applications of Hevea rubber, efforts to discover the chemical nature of rubber started with the determination of its elemental composition in 1826. Later it was shown that rubber pyrolysis yields low molecular weight chemicals with the identical elemental composition. It was long believed that these add to each other by “secondary valence bonds.” However Staudinger's work starting in 1920 proved that Hevea (H.) rubber consists of chains linked by covalent bonds. The utility of rubber increased dramatically with the discovery of vulcanization by Goodyear in 1844. However the nature of this process remained for many years controversial due to the influence of the “colloid school” of chemistry. The first observations on the nature of rubber elasticity date back to 1805, but more than a century passed before it was shown that the retractive force of stretched rubber is entropic. X-ray crystallographic studies not only provided the ultimate proof that natural rubber consists of covalently bonded chain molecules, but also gave evidence for its chemical structure. A century ago it was found that polymeric products other than H. rubber exhibited similar elastic properties. The race to produce synthetic rubbers was largely stimulated by the two World Wars. The availability of 14C labeled precursors led to the detailed description of the biosynthetic pathway by which rubber is produced in the Hevea plant.