bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature of Network, Carbon-Black-Rubber Interaction and Heat Aging of Polyethylacrylate Vulcanizates
Authors: Nakajima N. , Miller R. A. 
Published: February 2011

Abstract
Two commercial polyethylacrylate elastomers, having about 50 Mooney Index were selected. They were compounded with 50 parts of N330 carbon black per 100 parts of rubber by weight. One sample having epoxide (EP) crosslinking sites was crosslinked with ammoniumbenzoate. The other having double-bonds by copolymerizing with ethylidene norbornene (ENB) was crosslinked with a sulfur system. The vulcanizates were oven aged at 175°C for 70 h. Tensile stress-strain measurements were performed with the gum rubbers, uncured compounds, unaged vulcanizates, and heat-aged vulcanizates. The data presented as tensile modulus—strain curves revealed the following: at all strain levels, the moduli of ENB gum samples were lower than those of EP gums. After compounding with carbon black, the moduli of two samples became very similar. This indicates that ENB has more affinity with carbon black than EP has. The vulcanizates of two samples has matching moduli at 10% strain but a difference in network structure, since the molecular architecture of the gum rubbers were very different. After heat aging, moduli at small strains increased significantly but not at large strains. The increases were very similar for both samples. The heat-aging characteristics may be very similar for both samples, in spite of the difference in the chemical nature of the crosslinks.
Numerical Simulation of Viscoelastic Flow: A Review
Authors: Crochet Marcel J. 
Published: February 2011

Abstract
It is evident that a major effort has been accomplished over the last ten years toward the development of numerical methods for solving viscoelatic flow. The problem was clearly much harder than expected. Several extensive reviews have been devoted to a detailed account of the difficulties encountered in reaching moderate values of the Weissenberg number. The numerical and analytical work undertaken in parallel by several research groups has led to some important conclusions which paved the way for recent promising development. First, numerical algorithms for solving highly nonlinear advective problems must be used with the greatest carefulness. When spurious solutions or unexpected effects such as limit points arise in numerical simulations, we have learned to question the validity of the numerical method as well as that of the constitutive equation. Typically, successive failures of numerical calculations with the Maxwell model at low values of We have often been attributed to its singular behavior in uniaxial elongational flow but, in the meantime, better adapted algorithms have led to solutions at ever increasing values of We. Secondly, the mathematical analysis of the partial differential equations governing the flow of viscoelastic fluids has revealed the possibility of changes of type of the vorticity equation under some circumstances, i.e., when the velocity of the fluid becomes comparable with the velocity of shear waves. The coexistence of hyperbolic and elliptic regions in a steady flow may be of great importance in explaining a number of experimental observations. Simultaneously, the analysis has led to the identification of artificial changes of type which partly explain some numerical failures, or at least give a pertinent diagnosis of numerical inaccuracy. Thirdly, it has been found that numerical algorithms must take into account the specific features of viscoelastic flow; among these, stress boundary layers, stress singularities, and advective (or memory) terms in the constitutive equations are prominent.
Rubber Mixtures
Authors: Roland C. Michael 
Published: February 2011

Abstract
The thermodynamic and kinetic factors governing the morphology of miscible polymer blends have been much investigated. While conceptually straightforward, modern theories of mixtures are more difficult to implement than the simple lattice theories which consider only molecular volumes. Particularly with regard to rubber mixtures, significant performance advantages associated with miscibility remain to be demonstrated. Phase separated blends are more complex; the factors controlling their structure development are difficult both to elucidate and to control. Nevertheless, extensive applications have been found for such blends. Their utilitization will likely continue to burgeon, particularly as more attention becomes focussed on the details of the spatial distribution of the domains in heterogeneous mixtures.
Design Principles for Vibration Isolation and Damping with Elastomers Including Nonlinearity
Authors: Harris J. A. 
Published: February 2011

Abstract
In this paper, some of the more novel features of the dynamic and static properties of elastomers have been examined in relation to their use in vibration isolation and damping. Exploitation of some of these features in advanced designs could lead to improvements in areas such as the protection of sensitive equipment and could lead to new concepts in systems such as ground-vehicle suspensions for large wheeled or nonwheeled vehicles designed for rough terrain. Elastomers are already used in many critical areas of space technology, however, the problems of temperature extremes and volatility make the space environment a challenging one. New developments in materials technology may yet be required to meet these demands, however, many of the principles discussed will still be applicable. The development of space technology may provide the impetus for new designs in which the potential of elastomeric components may be exploited to the full, with valuable spin-offs to nonspace applications, where cost considerations may currently inhibit the development of advanced devices.
Rheological Determination of Molecular Weight and Molecular-Weight Distribution for Commercial-Type Butyl Elastomers
Authors: Lobos Z. J. , Tang H. 
Published: February 2011

Abstract
1. There exists a linear correlation between rheological parameters (crossover frequency and crossover modulus) and structural parameters (Mw, and MWD) for commercial-type butyl elastomers. 2. There appears to be potential value in utilizing rheological testing for quality control for commercial-type butyl elastomers. 3. Further work is required to resolve testing problems (air entrapment and sample trimming) which affect the precision of the rheological measurements.
Surface Characterization of Rubber by Secondary Ion Mass Spectrometry
Authors: van Ooli W. J. , Nahmias M. 
Published: February 2011

Abstract
It has been demonstrated that static SIMS is potentially a very useful technique for the characterization of rubber surfaces. Its major capability is to provide molecular structural information of the polymer in addition to elemental analysis, which would also be possible with other surface techniques such as XPS or AES. The SIMS spectra are in many cases highly characteristic, and they can be used to identify the type and structure of the hydrocarbon polymer. In addition, structural changes in the rubber surface can be detected, and very useful information on the types and amounts of sulfur crosslinks can be obtained as well, as has been published elsewhere. Therefore, the technique shows great promise as a tool for the study of surface-related rubber phenomena, such as oxidation, wear, tack, antiozonant and antioxidant performance and mechanisms, and also for the study of the adhesion between dissimilar rubbers or between rubbers and other materials, such as metals. Before SIMS can be routinely used in rubber laboratories, a considerable amount of basic and fundamental work will have to be done because the spectra of many materials are not known, and they cannot always be predicted either. Therefore, a rubber-related data base will have to be built up with well-characterized polymers but also using clean films of various rubber additives. Crosslinking studies will have to be confirmed with compounds of known crosslink structures, e.g., by using different polymers, different types of accelerators, and a series of model compounds of organic sulfides.
Anomalous Fatigue Behavior in Polyisoprene
Authors: Roland C. M. , Sobieski J. W. 
Published: February 2011

Abstract
Annealing of a polyisoprene-based elastomer can resuit in significant changes in its failure properties, the nature of which depends on the deformation of the rubber during the annealing. Although a deterioration of properties from low-strain annealing and improved performance from high-strain annealing may be contrary to intuition, the mechanisms which underlie these annealing effects are well known. The behavior described herein simply represents other manifestations of these phenomena. These alterations in performance, moreover, are readily induced at strains within the range of conventional fatigue and crackgrowth experimentation, and thus demonstrate some of the difficulties in relating laboratory characterizations to the performance of materials in other environments.
N-(4-Anilinophenyl)-Methacrylamide, a Polymerizable Amine Antioxidant: Synthesis, Copolymerization, Copolymer Properties, and Performance
Authors: Parker Dane K. , Schulz G. O. 
Published: February 2011

Abstract
In conclusion, we have demonstrated that N(4-anilinophenyl)-methacrylamide (APMA) is a readily polymerizable, nonstaining amine antioxidant molecule that can be incorporated into free-radical emulsion polymerization recipes by a variety of techniques. Furthermore, we have also demonstrated that the polymer-bound APMA's effectiveness can be greatly enhanced in gum or cured rubber when it is used in conjunction with either free or bound sulfur-containing secondary antioxidants (synergists). Superior performance was demonstrated for the polymer-bound antioxidant systems using oxygen absorption, DSC, and aged (extracted) physical property retention techniques.
A Hypothetical Mechanism for Rubber Abrasion
Authors: Gent A. N. 
Published: February 2011

Abstract
A hypothetical mechanism for creating subsurface cracks during frictional sliding has been proposed as part of the process of abrasive wear of rubber. It consists of the unbounded elastic expansion of microscopic precursor voids until they burst open as cracks, under the action of internal pressure or of a triaxial tension in the surrounding rubber. This conjecture accounts for enhanced resistance to abrasion for compounds reinforced with carbon black, in terms of increased stiffness without much loss of extensibility, and for the lack of correlation of abrasion resistance with other measures of strength. It. should be noted that it is specific to soft, extensible materials, and thus it also accounts for marked differences in the nature of the wear process in rubbery materials compared to plastics and metals. Only rubbery materials appear to abrade away by a linking up of microcracks at right angles to the sliding direction to produce characteristic wear ridges known as the Schallamach abrasion pattern. Three mechanisms of generating a sufficiently large inflation pressure or triaxial tension are discussed. The most probable one seems to be thermal decomposition of rubber, generating volatile decomposition products—a microscale blowout process. This would be aggravated by a simultaneous softening of the rubber on heating. Although strictly conjectural, the proposed wear mechanism suggests a number of interesting experiments. For example, it would be helpful to know whether the character of wear changes when abrasion is carried out under a large superimposed hydrostatic pressure. Also, not enough is known about abrasion in vacuo. Is the process altered in kind, as well as in rate? And if thermal decomposition is, indeed, an important mechanism of initating subsurface cracks, what is the effect of changes in thermal conductivity of the abrading material on the rate of wear?
Pull-Out and Push-Out Tests for Rubber-to Metal Adhesion
Authors: Gent A. N. , Kaang S. Y. 
Published: February 2011

Abstract
A study has been carried out of adhesive failure forces for a steel rod embedded in and bonded to a rubber block. Emphasis has been placed on comparing tension (pull-out) and compression (push-out) forces. A fractional contribution to the pull-out force appeared to be significant for rods having a diameter greater than about 0.5 mm in the present experiments. Indeed, it became a large fraction of the total force when the rod diameter was 1 mm or more. On the other hand, it was negligibly small in push-out experiments. They would therefore be preferred on this basis for measuring the strength of adhesion. But experimental difficulties in carrying out compression tests are considerable. Tall blocks become unstable under large compressive loads, and short ones are markedly stiffer than long ones, due to restraints on their lateral expansion, which are difficult to specify and control. Thus, although measurements of push-out force for a wide variety of samples have been shown to be in good accord with a simple theoretical treatment of debonding, ignoring friction, it is recommended that pull-out tests be retained for assessing the strength of adhesive bonds. Caution is necessary to minimize the effect of friction. The theoretical treatment indicates that the product aL of the rod radius a and the embedded length L should be held smaller than the cross-sectional area of the block in which the rod is embedded.
Kinetics of Chain Scission of Natural Rubber
Authors: Sambhi M. S. 
Published: February 2011

Abstract
The first-order and zero-order kinetic models of chain scission, based on random chain scission processes, are critically examined. It is likely that for many practical situations, the first-order chain scission kinetics can be represented by pseudozero-order kinetic types of equations. The kinetic results indicate that chain scission of NR occurs either by a pseudofirst-order or a pseudozero-order process. The pseudozero-order chain scission kinetics of NR are in consonance with the result that chain scission involves the bimolecular reaction of peroxy radicals in the termination step of the oxidation mechanism. However, this does not preclude unambiguously other chain scission reactions. The chain scission activation energy of NR is determined with the use of expressions derived for the oxidative degradation of NR as measured in terms of Wallace plasticities.
Semiempirical Relationships between Properties and Loading in Filled Elastomers
Authors: Pouchelon A. , Vondracek P. 
Published: February 2011

Abstract
The dynamic storage modulus of uncured silica-filled silicone rubber increases sharply when a critical filler loading is reached. A similar behavior has been observed for the conductivity in the same compounds. The experimental data fit a percolation law fairly well, and microscopy confirms the formation of a filler network according to the percolation model. This behavior depends on a polymer-filler interaction level, suggesting a filler network consisting of filler particles bridged together by adsorbed polymer. It has been found that the percolation threshold coincides with the optimum value of elongation at break of the corresponding vulcanizates. The percolation behavior and the relations between properties of filled rubbers described here were observed in various filled rubbers of quite different compositions. This seems to suggest the general validity of the presented relationships in all elastomers reinforced by particulate fillers.
Dynamic Electrical and Electromechanical Properties of Carbon-Black Loaded Rubber
Authors: Burton L. C. , Hwang K. , Zhang T. 
Published: February 2011

Abstract
1. Low-frequency resistance can be dominated by contacts. It was found that silver paint contacts were roughly equivalent to metal contacts bonded during vulcanization. 2. Three electrical regimes are clearly evident, determined by loading: dielectric, percolation, and conducting. 3. Resistance and dielectric constant dispersion for loading above 30 phr agree with Kawamoto's model. 4. Each carbon-black loading results in a distinctive dispersion signature. 5. Dynamic conductivity can be used to delineate persistent and transient carbon-black-structure changes versus composition, DSA, frequency, and potentially other parameters (temperature, stress waveform, etc.). 6. The remaining conductive network during stress is represented by gmin; Δg is determined by network fracture and reformation; gmin−gα is proportional to the amount of remaining transient structure; g0−gα is proportional to the total transient structure; normalized conductivity Z is the remaining-to-total transient-structure ratio. 7. The Δgm=0.525(g0−gα) relation indicates that maximum reformation occurs when approximately half the transient structure is broken down and confirms the correlation between conductivity parameters and transient carbon-black structure.
Solid-State Carbon-13 NMR Studies of Vulcanized Elastomers. VII. Sulfur-Vulcanized Cis-1,4 Polybutadiene at 75.5 Mhz
Authors: Clough R. S. , Koenig J. L. 
Published: February 2011

Abstract
Solid-state C-13 NMR spectroscopy provides a wealth of chemical information concerning sulfur-vulcanized cis-l,4-polybutadiene. New resonances which appear upon curing have chemical shifts which are expected for crosslink and cyclic structures. The DEPT experiment with MAS worked well for the polybutadiene vulcanizate in the solid state. DEPT is very useful as an aid in the assignment of structures to resonances. The new resonances can be assigned to more than one type of structure given only chemical shift and DEPT information. Swelling measurements indicate the majority of the resonances are due to cyclics. Further work involving C-13 NMR characterization of polybutadiene vulcanizates treated with chemical probes and vulcanizates cured with organic accelerators should provide insight into the specific structures responsible for the individual resonances.
Viscoelastic Simulation of Flow of Rubber Compounds
Authors: Sobhanie M. , Isayev A. I. 
Published: February 2011

Abstract
A hybrid scheme has been developed for numerical simulation of a nonisothermal viscoelastic flow in an arbitrary planar geometry of uniform thickness during extrusion and injection molding. This formulation is based on the control-volume finite-element method for solution of the continuity and momentum equations and finite difference method for solution of the energy equation. Application of this numerical technique for simulation of an extrusion and injection molding process was performed in a slit die and a quarter of a circular disk cavity, respectively. Development of pressures, shear and normal stresses, velocities, and temperature fields were calculated during nonisothermal flow of the rubber compound. Furthermore, the relaxation of stresses was calculated after cessation of the flow. The location of the meltfront was predicted during the cavity filling process. The contribution of normal stresses was studied by comparing results following from the viscoelastic and inelastic simulations.
Resistance of Polymers to Permeation by Air Conditioning Refrigerants and Water
Authors: Trexler Harold E. 
Published: February 2011

Abstract
The permeability of several polymers to refrigerants and to water vapor has been determined. The investigation included refrigerant R-12 which is currently used in automotive air conditioning and refrigerants R-22 and R-134A which are considered as future candidates. For the different polymers investigated, the permeability constants for R-22 at 93°C ranged between 0 and cm/11×10−10 cm2 sec cm2  cm Hg for the plastics, 29×10−10 and 124×10−10 for thermoplastic elastomers and 135×10−10 and 276×10−10 for crosslinked elastomers. The permeability decreased with decrease in test temperature and with increase in molecular size of the refrigerants. Hence both R-12 and R-134A exhibited lower permeability constants than R-22 because of their bigger size. Trends in water permeability of the different polymers were mostly opposite to those of the refrigerant permeability. For example, polynorbornene has the lowest water permeability of the polymers tested, but has one of the highest permeability constants for refrigerants. Of the new polymers investigated, the lowest overall permeability to water and refrigerants was exhibited by PET polyester, polypropylene, Hytrel polyester, and plasticized Polyamide 12 (5% plasticizer).
Swelling of Fluoroelastomers in Synthetic Lubricants
Authors: Neppel A. , Kuzenko M. V. , Guttenberger J. 
Published: February 2011

Abstract
Viton A elastomers of variable crosslink density show high swelling in a diester-based lubricant only after heat aging, e.g., at 175°C for three days. Volume increase data in methylethyl ketone and 100% modulus reveal that heat aging induces considerable decrosslinking. Swelling tests in pure diesters and the corresponding Flory-Huggins interaction factors indicate a sharp decrease in the entropy term (of the Hildebrand-Scott equation) of some of the interaction factors upon heat aging. High swelling seems to occur only if the size of the liquid molecules does not exceed a limit since otherwise their diffusion into the elastomer network is hindered. Such a hindrance may be attributed to a large entropy term. Heat aging appears to increase the above limit to molecular size thus diminishing the entropy term and permitting large amounts of swelling even in certain of those liquids whose diffusion into the network was hindered before heat aging.
Elastomer-Gasoline Blends Interactions I. Effects of Methanol-Gasoline Mixtures on Elastomers
Authors: Abu-Isa Ismat A. 
Published: February 2011

Abstract
1. Properties of most fuel resistant elastomers are degraded to a larger extent by mixtures of methanol and gasoline than by the pure components. 2. The data on all elastomers except the fluorocarbon can be explained in terms of the solubility parameter concept. 3. The ultimate tensile strength and ultimate elongation of swelled elastomer networks are quantitatively related to volume swell by simple linear relationships. 4. Ultimate stress and ultimate elongation of swelled elastomer networks obey equilibrium stress-strain relationships.
Elastomer—Gasoline Blends Interactions II. Effects of Ethanol/Gasoline and Methyl-t-Butyl Ether/Gasoline Mixtures on Elastomers
Authors: Abu-Isa Ismat A. 
Published: February 2011

Abstract
The effects of ethanol/gasoline and MTBE/gasoline mixtures on swell and tensile properties of selected automotive elastomers were determined and compared to those of methanol/gasoline mixtures. Two gasolines with aromatic content of 30% and 50% were used in this investigation. Equilibrium swell and tensile measurements were conducted using ASTM standard procedures. Results show that in the case of ethanol/gasoline combinations, the elastomers were more severely affected by the mixtures than by the pure components. The ethanol/gasoline mixtures are less severe than the methanol/gasoline mixtures in their effects on most fuel resistant elastomers. In the case of MTBE, effects of mixtures with gasoline were an average of the effects of the pure components. The presence of a higher aromatic content in the gasoline resulted in increased swell and, hence, increased deterioration of tensile properties of elastomers exposed to the gasoline and its mixtures. Addition of benzene to increase the aromatic content resulted in slightly more detrimental effects on nitrile elastomers than the addition of toluene. The data on all elastomers can be explained in terms of the solubility parameter concept. For most elastomers, the ultimate tensile and elongation values were found to be quantitatively related by simple linear equations to the volume fraction of the rubber swelled in mixtures of gasoline and ethanol or MTBE. They were also found to be related to each other by simple logarithmic relationships.