bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Elastomers through Control of Network Chain-Length Distributions
Authors: Mark J. E. 
Published: February 2011

Abstract
Methods are described for obtaining elastomers of controlled network chain-length distributions by restricting the reactivity of the polymer chains to their ends, and then end linking these chains with a multi-functional reactant. The networks of this type that have proved to be of greatest interest consist of short chains end linked with long chains to yield a bimodal distribution of network chain lengths. These bimodal elastomers have unusually high extensibility for their values of the modulus and ultimate strength, and thus considerable toughness, even in the unfilled state. Most such elastomers have been prepared from chains of poly(dimethylsiloxane), by carrying out either a condensation reaction between hydroxyl-terminated chains and tetraethoxysilane, or an addition reaction between vinyl-terminated chains and a poly(methylhydrogen siloxane) oligomer. The material presented in this review discusses the preparation of such elastomers, the characterization of some of their properties, and the interpretation of some of these properties in terms of the molecular theories of rubber-like elasticity.
Synthesis and Characterization of Novel Multiarm-Star Polyisobutylene-Polystyrene Thermoplastic Elastomers
Authors: Puskas Judit E. , Pattern Wayne , Wetmore Paula M. , Krukonis Val 
Published: February 2011

Abstract
New multiarm-star block copolymers of polyisobutylene (PIB) and polystyrene (PS) were synthesized by living carbocationic polymerization using a novel hexafunctional initiator in conjunction with TiCl4. The new initiator, hexaepoxy squalane (HES) was prepared by a simple epoxidation (RT, 5 min) of commercial squalene. The homopolymerization of isobutylene (IB) initiated by HES is living, demonstrated by linear ln([M]o/[M]t) vs time and Mn vs conversion plots and relatively narrow molecular weight distributions (MWD=1.2). The branched nature of the PIBs was proven directly by diphenyl ethylene end capping, and indirectly by kinetic analysis and size exclusion chromatography (SEC). Subsequent blocking of PIB with PS was demonstrated by triple detection SEC: refractive index (RI), multiangle laser light scatering (MALLS) and ultraviolet (UV). A new multiarm-star and a conventionally prepared linear triblock copolymer sample were subjected to supercritical fluid (SCF) fractionation and the fractions were analyzed by SEC and 1H NMR. Analysis of the fractions indicated living conditions for the PS blocking in the star-block. Interestingly, the linear triblock showed bimodal distribution in terms of PS content and molecular weight.
Miscibility of Blends of Saturated Hydrocarbon Elastomers
Authors: Lohse David J. , Garner Richard T. , Graessley William W. , Krishnamoorti Ramanan 
Published: February 2011

Abstract
Over the last several years, a great deal of progress has been made in understanding the basic miscibility between saturated hydrocarbon polymers. This has mainly been accomplished through the use of neutron scattering, but has also benefited by the results from light scattering, pressure-volume-temperature (PVT) measurements, and other techniques. This paper concentrates on the results that apply to elastomers such as polyisobutylene (PIB) and ethylene-propylene-diene rubber (EPDM).
Phase Behavior and Properties of Polyurethane-PVC Blends and Fibers
Authors: Petrović Zoran S. , Javni Ivan , Shull Jonathan , Waddon Alan 
Published: February 2011

Abstract
A polyester urethane elastomer is blended with rigid poly(vinyl chloride) (PVC) and the miscibility of the components studied over the entire range of compositions. The polyurethane elastomer was a block copolymer with a low degree of crystallinity, while PVC was practically amorphous. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) methods showed that polyester urethanes were partially miscible with PVC since two distinct glass transitions, which changed with the change of concentration of components, were observed. Although the PVC content was varied from 0–100%, the aim of the work was to examine if PVC at low concentrations would form fibrils in the urethane matrix and act as a reinforcing agent for the polyurethane elastomer. The morphology of the blends was studied by scanning electron microscopy and x-ray scattering. The blends were then spun into fibers to force the dispersed phase to elongate and form fibrils (draw ratio was about 100). A high degree of miscibility is obtained at low concentration of either of the components. The PVC phase in fibers spun from the blends have higher glass-transition temperature (Tg) than in isotropic blends, presumably due to increased orientation. No fibrillation of the rigid phase in the elastomeric matrix could be observed. The fibers displayed higher strengths but lower elongation at break than the isotropic blends of the same composition. Intermeshing morphology (at about 50/50 concentration) gave the lowest strengths.
Mechanical Behavior of Particle Filled Elastomers
Authors: Bergström Jörgen S. , Boyce Mary C. 
Published: February 2011

Abstract
The strong influence of relatively small amounts of filler particles, such as carbon black, on the mechanical properties of elastomers has been well known for decades and has significantly contributed to increased use of elastomeric materials in many commercial applications. Even though the use of fillers is ubiquitous, satisfactory understanding and modeling of the micromechanisms by which fillers alter the mechanical behavior of elastomers has still not been realized. In this work the influence of filler particles on the equilibrium stress-strain response has been investigated. First, an experimental investigation probing the behavior of a chloroprene rubber with varied filler content has been performed. The experimental data allowed for a direct evaluation of both a newly developed constitutive model based on the amplification of the first strain invariant, and a number of other models proposed in the literature. A direct comparison with experimental data suggest that the new model generates superior predictions, particularly for large strain deformations. Then, in an effort to examine some of the assumptions that are common in the constitutive modeling and also to try to determine which of the input parameters are most important, a detailed series of micromechanical models were constructed using two- and three-dimensional finite element simulations. The results indicate that the effect of filler particles on the equilibrium behavior of elastomers can be accurately predicted using stochastic three-dimensional simulations suggesting that successful modeling mainly requires a rigorous treatment of the composite nature of the microstructure and not molecular level concepts such as alteration of mobility or effective crosslinking density in the elastomeric phase of the material.
Tread Groove Void and Developed Tread Width (Aspect Ratio): Their Joint Influence on Wet Traction
Authors: Veith Alan G. 
Published: February 2011

Abstract
Other than treadwear testing, tires are normally evaluated for important performance features in the virgin or new state. One performance feature that changes, as the tire wears in service, is wet traction. For any given tread compound the wet traction performance is jointly influenced by the groove void level (it changes with wear) and a factor that is a function of the aspect ratio, the “developed tread width,” i.e., the actual width that contacts the road surface. Based on a comprehensive testing program, a wet traction performance parameter called the “specific discharge capacity” has been developed. This accounts for the interactive or joint influence of both of these factors and how this influence changes across a range of operating conditions (speed, pavement texture). The specific discharge capacity is especially important at high levels of “criticality”, i.e., deep water, slippery pavement, high speed.
A Model for Rubber Degradation under Ultrasonic Treatment: Part I. Acoustic Cavitation in Viscoelastic Solid
Authors: Yashin V. V. , Isayev A. I. 
Published: February 2011

Abstract
The physics of rupture of a rubber network under the action of powerful ultrasound is considered. It is assumed that rubber degradation occurs mainly around pulsating microcavities (bubbles) usually present in rubbers. The maximal level of strain is attained in the vicinity of these cavities. A Lodge-like model of finite viscoelasticity is utilized to describe the strain profile around the vibrating cavity at a given ultrasonic pressure. Network degradation rate is taken to be proportional to the number of overstressed network chains. Detailed analysis is given for the case of a thin layer of cured rubber placed between an ultrasonic horn and a die and subjected to static pressure. Ultrasonic pressure in the layer is shown to depend on the thickness of the layer with its value found to be higher than that in the bulk. The static pressure is found to increase the ultrasonic power consumption and to enhance the degradation process. This is due to a decrease in compressibility of the bubbly media leading to a reduction in the ultrasonic attenuation. Calculations are carried out using styrene-butadiene rubber as an example.
Effect of Gasoline Contamination on the Permeation of Organic Liquids through Rubber Membranes
Authors: Xiao S. , De Kee D. , Bovenkamp J. 
Published: February 2011

Abstract
The effect of gasoline and oil contamination on the barrier properties of natural rubber, nitrile rubber and bromobutyl rubber have been experimentally studied for the following organic environmental contaminants: dichloromethane, acetone and toluene. Oil contamination has little effect on the subsequent transport of these organic penetrants. However, gasoline contamination alters the subsequent transport behavior of these organic penetrants, depending on the nature of the rubber and the contamination conditions. Nitrile rubber experiences minor effects, while natural rubber is severely affected. Penetrant breakthrough times as well as limiting diffusion coefficients increase with increasing temperature and/or contamination time.
Orientation Texture and Gas Transport in Semicrystalline Block Copolymer Blends
Authors: Kofinas Peter , Drzal Peter L. , Halasa Adel F. 
Published: February 2011

Abstract
The shear-induced morphologies produced by plane strain compression, using a channel die, were investigated in semicrystalline ethylene/ethylene-propylene (E/EP/E and E/EP) block copolymers blended with semicrystalline low density polyethylene and amorphous polyisoprene homopolymers. Two dimensional small-angle x-ray scattering (SAXS) was used to determine the lamellar orientation relative to the specimen boundaries. Using a cooling rate of 0.27 °C/s and a load of 9.2 MPa, a normal to the plane of shear microstructure orientation texture was produced in the blends. The E homopolymer chains co-crystallize within the confinement of the oriented microphase separated E block copolymer domains. The long period spacing of the oriented microphase separated E/EP block microstructure remained unchanged, while the spacing associated with the crystallization of the E chains increased with increasing weight percent of E homopolymer in the blend. Gas permeability coefficients for He and CO2 were measured for isotropic and oriented blends. The separation properties of these polymer systems was altered by changing the mechanism of gas transport. A selective solvent was used to develop a uniform porous structure in the oriented blend morphologies. The semicrystalline block copolymer blend structure oriented perpendicular to the direction and normal to the plane of shear presents the opportunity to create a high flux porous structure, while keeping the pores of nanometer dimensions, thus providing some selectivity and retaining mechanical strength.
Quantification of Tire-Tread Particles Using Extractable Organic Zinc as Tracer
Authors: Fauser Patrik , Tjell Jens Christian , Mosbaek Hans , Pilegaard Kim 
Published: February 2011

Abstract
A method for identifying and quantifying tire-tread particles in the environment has been developed. It is based on the measurement of extractable organic zinc. The high sensitivity of atomic absorption spectrometry (AAS) with a heated graphite atomizer (HGA) permits assessment of submilligram amounts of tire debris in environmental samples. The analysis is performed on aerosol and soil samples. This new method is more accurate and faster than the previously reported IR method.
Structural Characterization of Sulfur-Vulcanized Rubber Networks
Authors: Saville B. , Watson A. A. 
Published: February 2011

Abstract
Studies of the chemistry of vulcanization today occupy a central position in current efforts to achieve better product performance from available natural and synthetic rubbers. They provide technologists with increasingly realistic pictures of the molecular make-up of vulcanizates from which relations between physical properties and chemical structure may be deduced. In addition these studies are aimed at an understanding of vulcanization, sufficiently advanced in chemical mechanistic terms, to permit the effect of changes in curing system on vulcanizate structure to be rationally predicted. Perhaps the most important and fascinating aspect of current activities in vulcanization chemistry is the problem of determining the structure of rubber vulcanizates. Part of this problem forms the subject of this Review. In order to keep this article within reasonable proportions two limits have been observed. First, attention in Section IV has been restricted to “sulfur-vulcanized” rubbers, i.e., where vulcanization is effected using recipes containing elemental sulfur or sulfur donor (e.g., thiuram disulfides or dithiobis-amines). Secondly, we shall distinguish between the in toto vulcanizate and the corresponding network (as defined by Moore) restricting our attention to the latter. Thus, we are concerned with the crosslinked assembly of rubber chains (the network) apart from filler particles, residual curatives and simple molecular products of the vulcanization reactions. These latter constituents are extra to the network and may be examined as a separate analytical exercise. The physical and chemical analyses of rubber networks cannot be undertaken entirely by classical means, and some unique problems are encountered which have required, and still require, imaginative techniques for their solution. An attempt has been made to deal with the important progress which has been made to date, emphasis being given to the most practicable and reliable methods which have been adopted and practiced. It will become evident that there are wide gaps in our knowledge, some of which must be filled even before structural characterization of certain networks can be tackled. It is therefore part of the intention of this review to point out the important outstanding problems and to stimulate activity in these areas while defining as clearly as possible the numerous pitfalls which exist in this demanding type of investigation.
Mechanics of the Pneumatic Tire
Authors: Frank F. , Hofferberth W. 
Published: February 2011

Abstract
We have attempted to describe the mechanical problems of tires, from the point of view of elasticity theory, and have, in this connection, regarded research on the stresses and deformations in the casing as the primary problem of tire mechanics. Less attention was paid to factors which have to do with the behavior of tires with respect to the vehicle, because we believe that the effects of the choice of any design or structural parameters or materials, upon the behavior of tires, are not explainable in a sufficiently general manner, as long as the above problem, designated as the chief one, cannot be handled, at least numerically. How far we still have to go, in spite of many efforts, can be seen from Section III. The striking thing here is that belted tires have scarcely been investigated up to now. This may be due, in part, to the fact that the prerequisites for a theoretical investigation, reported in Section I, have been provided only imperfectly for this type of tire, up to now. Our own contribution, in this respect, was an outline of a generalized theory of the tire cross section, found useful for the belted tire. Measured against the state of knowledge in related fields, the present survey of the literature available to us shows that tire mechanics still represents a rather poorly developed field of research which might arouse the interest of scientists working at academic centers, for example. Section II of this work can also be thought of as stimulating interest in further development, as it mostly presents methods which can be taken over from other fields.
Vacuole Formation and the Mullins Effect in SBR Blends with Polybutadiene
Authors: Smith Ronald W. 
Published: February 2011

Abstract
Electron microscopic examination of stretched thin films of black loaded vulcanizates of SBR and polybutadiene blends shows that vacuole formation is prevalent when the polybutadiene content drops below one-third. The vacuoles that formed on stretching these stocks did so at small coherent carbon black agglomerates rather than at individual carbon black particles. It is felt that the mixing characteristics were such that stocks with more polybutadiene experienced more grinding action, which resulted in destroying the small agglomerates that caused vacuoles in stocks with less polybutadiene. Hysteresis data on the same series indicated that for the vacuole forming stocks the ratio of the areas of the first to the second hysteresis loop reflects the fact that vacuoles are being formed. The overall Mullins' effects displayed by all members of the series was similar, and a mechanism was proposed that slightly modifies the hysteresis criteria of Harwood, Mullins, and Payne. It is suggested that this mechanism can also be used to explain the effects that various particle size carbon blacks have on extensions following the initial one. The effect of vacuole formation on the overall Mullins stress softening was minor and equivalent to disrupture of filler structure.
Elucidation of Polymer Microstructure by High Resolution NMR Spectroscopy
Authors: Ferguson Raymond C. 
Published: February 2011

Abstract
High resolution NMR spectroscopy is proving to be a useful experimental technique for determining the microstructures of high polymers. Its major utility, aside from identifying structural features often not detectable by other methods, lies in quantitative applications. Some examples are the determination of monomer ratios in copolymers, polymer tacticity, sequence isomerism of monomer units, and other types of structural isomerism. The applicability of the method is being enhanced by continuing development of high-field spectrometers, special accessories, and new experimental techniques, and by application of computers to the analysis of spectral data.
Viscoelastic Properties of Multiple Network Polymers. IV. Copolymers of Styrene and Divinylbenzene
Authors: Shibayama Kyoichi , Suzuki Yasukira 
Published: February 2011

Abstract
Copolymerization of vinyl and divinyl monomer is a typical method for preparing a network polymer. A multiple network structure, in which one network entangles with another, is supposed to be produced when a network polymer is swollen in the monomer mixture and then polymerization of absorbed monomer is carried out so as to superpose the second network on the first. Viscoelastic properties and degree of swelling in solvents were investigated for composite polymers prepared from styrene and divinylbenzene. Results were consistent with presumed characteristics of multiple network structures.
Effect of Molecular Weight on Dynamic Mechanical Properties of SKD cis-1,4-Butadiene Rubber
Authors: Marei A. I. , Sidorovich E. A. 
Published: February 2011

Abstract
In the high-elastic temperature range the molecular weight has a considerable effect on the dynamic mechanical properties of linear (uncrosslinked) SKD cis-1, 4-butadiene rubber. In this temperature range an unequivocal correlation exists between the rebound resilience at a given temperature and the viscosity average molecular weight, and the determination of the resilience can therefore be recommended as a rapid method of finding the molecular weight of SKD. A similarity is found in the dynamic mechanical behavior of rubbers of different molecular weights in the high-elastic temperature range. In the low-temperature range an increase in the molecular weight of crystalline polymers of SKD is accompanied by an impairment of their elastic properties.
Resistance to Ozone Cracking in Elastomer Blends
Authors: Andrews E. H. 
Published: February 2011

Abstract
The phenomenon of ozone cracking has been investigated for elastomer blends containing an ozone reactive phase (natural rubber) and an ozone inert phase (ethylene propylene rubber). Electron microscopical studies reveal phase separation in the blend and the locus of ozone attack. Ozone cracks traverse the reactive phase and occasionally jump across inert particles without severing them. This mechanism provides the basis of a theory which correctly predicts the dependence of both the critical stored energy for ozone cracking and the crack density upon the blend composition.
Elastic Properties of Networks Formed from Oriented Chain Molecules II. Composite Network
Authors: Greene A. , Smith K. J. , Ciferri A. 
Published: February 2011

Abstract
Elasticity measurements were carried out for several natural rubber and poly (ethyl acrylate) networks crosslinked in two stages (first in the isotropic state and then in the stretched state). These composite networks were shown to be similar in behavior to networks formed by crosslinking in the fibrous state and differed significantly from the usual network formed by crosslinking in the isotropic state. The anisotropic elasticity exhibited by these composite networks cannot be fully accounted for by finite chain extensibility. It appears that the deviation of the behavior of these networks from theoretical expectation is associated with the same kind of effects responsible for deviations from rubber elasticity theory in conventional networks.
Crystallization of Natural Rubber
Authors: Bekkedahl Norman 
Published: February 2011

Abstract
It is, indeed, a very great honor to have been chosen as the Charles Goodyear Medalist for 1967, and I very much appreciate the opportunity of coming here to tell you about some of the research work in the field of rubber with which I have been associated for a number of years. The bylaws of the Division of Rubber Chemistry, A.C.S., require that the recipient of this award deliver a lecture before the Division on a subject that is related to the elastomer field and presented in accordance with the contribution for which the medal is awarded. It should, therefore, be quite appropriate for me to discuss one of my favorite subjects, the crystallization of natural rubber. My first thought was to talk on a broader subject, transitions in rubber, which would have included the glass transition, but such a paper was found to be much too long. Even the subject of the crystallization and melting transition is so broad that only a very condensed version can be given here today. In fact, the references for a proper review would run into the hundreds, so therefore I decided to restrict the paper to cover only the research work that has taken place in our own laboratories of the National Bureau of Standards. I should like to consider this award as one given not to me alone but rather to the group of us at the National Bureau of Standards who have been conducting scientific research on rubber during the past few decades. The names of most of these investigators who have made contributions in the area of rubber crystallization will appear in the bibliography of the published paper, but I should like at this time to name a few of the senior scientists whose work we shall discuss here.