bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological Properties of Rubber-Carbon Black and Carbon Black-Oil Compounds Including Measurements at Very Low Shear Stresses
Authors: Osanaiye Gabriel J. , Leonov Arkadii I. , White James L. 
Published: February 2011

Abstract
The rheological properties of binary rubber-carbon black compounds at compositions 5, 20, 30, 40 and 50 volume percent carbon black have been investigated as well as ternary compounds with rubber/carbon black/oil compositions of 70/20/10, 60/20/20 and 50/20/30, respectively. The compounds were investigated using (1) a constant stress creep instrument at very low rates of deformation, (2) a rotational rheometer at intermediate shear rates and (3) a capillary extrusion instrument at higher shear rates. In experiment (1), it was found that below a critical yield stress, the strain becomes saturated and finite. Above this stress the strain becomes unbounded and the compound maintained a steady shear flow. This observation was made for all compounds investigated. The values of the yield stresses obtained using the creep instrument were found to be significantly lower than those obtained from common extrapolations from rotational and capillary rheometers. In the ternary compounds it was also observed that as the oil content increases, not only the viscosity but the yield stress is reduced significantly. This observation is important because it can throw light on the type of interactions between carbon black and the rubber matrix.
Large Deformation Micropolar Theory for Cord Rubber Composites
Authors: Padovan Joe , Parris Hua , Ma Jin 
Published: February 2011

Abstract
Based on a 2nd Piola Kirchhoff type formulation, a new unipolar cord rubber composite constitutive theory is developed. It has the capability to handle the local/global effects of cord twist under both small and large deformation situations. In this context, the theory handles the coupling between stress and moment stress and associated kinematics. The development also handles several new Poisson effects which involve the coupling of both axial elongation and twist, as well as axial twist and lateral elongation. The theory incorporates both experimentally and analytically based parameters to define the various response characteristics. The analytical results involve the use of several finite element simulations to define local cord rubber response. Several elasticity/strength of materials based limiting arguments were used to define asymptotic behavior, thereby providing for a more physics based curve fit of empirical data.
Fracture of Elastomers by Gas Decompression
Authors: Stevenson Andrew , Morgan Glyn 
Published: February 2011

Abstract
A study has been made of gas decompression failures in elastomeric seals using a fracture mechanics approach and considerations of gas permeation. An equation is proposed for the tearing energy associated with crack growth from internal gas bubbles in a finite thickness elastic media. When applied to a model experiment where an internal flaw of known size was pressurized up to failure, the equation agreed with experimental results. A series of seals were then subjected to high gas pressures (up to 69 MPa or 10,000 psi) for a range of temperatures between 20 and 230°C and the amount of crack growth was measured after decompression. The trends in crack growth were correctly accounted for when values for tearing energy and modulus were used that were appropriate for the temperature of decompression. The effect of mechanical boundary constraint was studied by varying the compression on the seal in specially designed test holders. The effect of decompression rate is also considered. The conditions under which failure will occur are created by a complex balance of the available tearing energy and the gas permeation kinetics. A fundamental problem is the unknown size of the initial flaw from which crack growth and rupture occurs. This is discussed in the light of the experimental results and it is proposed that effective surfaces of weakness form in the elastomer phase of size to provide initiation sites for crack growth.
Effect of Hydrocarbon and Amine Diluents on the Properties of Dicumyl Peroxide Cured Styrene-Butadiene Rubber, Part I: Gum Compositions
Authors: Hamed Gary R. , Hsu Jing-Ming 
Published: February 2011

Abstract
Gum SBR compositions containing dicumyl peroxide and either alkane (nonadecane) or amine (octadecylamine or oleylamine) diluent were prepared. Dilution caused a reduction in rheometer torque upon curing and in the resulting crosslink density based on solvent swelling. Results for each diluent were indistinguishable. However, tensile strengths and especially storage moduli were different for nonadecane- and octadecylamine-diluted vulcanizates. Added octadecylamine mildly reinforced the gum, while nonadecane lowered strength and stiffness. Furthermore, quite strikingly, octadecylamine-diluted samples had a large, low-strain storage modulus, which decreased markedly with strain amplitude (Payne effect), while vulcanizates diluted with nonadecane showed no Payne effect.
Relationship between the Cohesive Strength and Tack of Elastomers: Part IV, Carbon Black Filled Styrene-Butadiene Rubber
Authors: Hamed G. R. , Wu P. S. 
Published: February 2011

Abstract
The autohesion and cohesion of uncrosslinked SBR (gum and black-filled) have been determined over a broad range of test temperatures and rates using a T-peel geometry. Peeling energies can be time-temperature superposed to form mastercurves using shift factors in accord with the WLF form. Universal constants are appropriate for the gum. While experimental constants were obtained for the black composition. Cohesion for the gum and filled SBR increase continuously with increasing test speed or reduced temperature. On the other hand, autohesion for the gum shows an abrupt transition by decreasing at a critical reduced rate, while autohesion of the filled SBR does not exhibit the transition. The transition is associated with a viscous-to-elastic response change with increasing RaT; filled SBR has reduced elasticity relative to the gum and hence the transition is not present. By examining relative autohesion, it is seen that the gum undergoes an interfacial-cohesive-interfacial transition response with increasing RaT. This is quite different than the behavior found when peeling apart elastomer/hard substrate bonds, such as the SBR/polyester bonds of Gent and Petrich; here, there is simply a cohesive-interfacial transition with increasing RaT. For elastomer-elastomer junctions there is interpenetration and chain mobility in the interphase formed. At sufficiently low RaT, interdiffused chains simply slide by one another giving interfacial failure. With increasing RaT entanglement couplings in the interphase become effective in preventing facile flow, and, at this point, failure becomes cohesive; finally, at even higher RaT, with a sufficiently elastic response, stresses apparently become concentrated at the interface and failure proceeds there. When an elastomer is bonded to a hard, immobile material, the mechanism of bonding is restricted to surface site adsorption. This reduces elastomeric chain mobility and produces more “glassy” dispersive interactions which resist separation relative to the chains which are held together by “rubbery” dispersive forces. Again at sufficiently high RaT, with increased elasticity, failure becomes interfacial.
Vulcanization: Conventional and Dynamic
Authors: Coran Aubert Y. 
Published: February 2011

Abstract
Conventional vulcanization, has a history of over 150 years, during which there have been increasing needs for technology to permit more and more rapid processing before the vulcanization of a rubber article in its final shape. But, at the same time, one desired increased rates of crosslinking after the part was in its final shape, e.g., in a mold. These two objectives are opposed to one another. For fast processing, we would like to increase temperatures to reduce the resistance to flow; but we do not want vulcanization to occur before processing flow is complete. On the other hand, after a rubber article is in its final shape or form, we would like for vulcanization to occur as rapidly as possible. The reasons for these objectives, are to increase capital utilization and to reduce the cost of money. The use of the premature vulcanization inhibitor, CTP, can give improved processing safety without loss of vulcanization throughput. In the case of thermoplastic elastomers prepared by dynamic vulcanization, all of the vulcanization is done rapidly during mixing, before the rubber compound flows into its final shape, e.g., during rapid thermoplastic injection molding (in seconds, not minutes). The dynamic vulcanization process does add cost to the material; however, this is more than offset by the gains in capital utilization. I would be remiss if I did not mention some potential disadvantages associated with the thermoplastic elastomers. One of these is that, at temperatures above the temperatures of flow, there is a great reduction in the usefulness of the properties (the materials can melt). A related disadvantage is that resistance to permanent set at high temperatures may be inadequate. However, the elevated-temperature set resistance of thermoplastic elastomers prepared by dynamic vulcanization is generally better than that of those prepared by other means. Both kinds of vulcanization are important and may continue to be so for another 150, or so, years.
Identification of Different Modes of Molecular Motion in Polymers That Cause Thermorheological Complexity
Authors: Ngai K. L. , Plazek D. J. 
Published: February 2011

Abstract
The viscoelastic properties of amorphous polymers are reviewed with emphasis on the glass to rubber dispersion (often referred to as the transition zone). Deviations from thermorheologieal simplicity (where molecular retardation and relaxation mechanisms have the same temperature dependence) are identified. Most theories and models of polymer chain dynamics do not address or acknowledge thermorheological complexities and correlations, such as that between the temperature dependence and the breadth of viscoelastic and dielectric dispersions of the local segmental motion. Without successful theories of these phenomena the understanding of polymer chain dynamics must be considered incomplete. In this review, old and new experimental data are used to identify the different modes of molecular motions and the domains of their contributions to the time and frequency dependence of the mechanical response of amorphous polymers. The different modes are then shown generally to have their own dependence on temperature. Thus the viscoelastic spectrum, including local segmental motions which dominate the onset of glassy behavior and largely determine the glass temperature, Tg, the glass to rubber softening dispersion, the rubbery plateau and the terminal zone, is thermorheologically complex. A coupling theory, with the physics of intermolecular interactions and cooperativity built into it, describes well the many-body dynamics of densely packed molecular systems such as polymers. The many predictions of the coupling theory are applied to the different viscoeleatic modes to explain the observed anomalous experimental facts and established correlations. The theoretical understanding has been improved to the extent that now a connection can be made between the chemical structure of the monomer and the viscoelastic properties of the polymer.
Distribution of Crosslinks in Vulcanized Blends
Authors: Tinker A. J. 
Published: February 2011

Abstract
All of the blend systems studied to date show a tendency to have an uneven distribution of crosslinks between the phases; this must be taken to be the norm, with instances of near-even crosslinking being the exception. When the crosslink distribution has been made to be near even, the properties investigated are generally improved. In blends of polar and nonpolar elastomers, there is a tendency for the polar elastomer to be more highly crosslinked than the less polar elastomer, because both the sulfur and accelerators partition in favor of the former. However, if one elastomer has a very high solubility parameter, the accelerator may partition in favor of the less polar elastomer. Provided this differential partition of the curatives is not extreme, the results can be beneficial. There is one recorded instance of a drastic reduction in overall crosslink density through very low crosslinking of one phase, and this may be ascribed to strong differential partition. Since crosslink distribution in blends of elastomers differing in solubility parameter appears to be controlled largely by partition of curatives and vulcanization intermediates, influence may be exerted by appropriate choice of accelerator(s). The crosslink distribution in blends of low and high unsaturation elastomers is extreme; at normal levels of curatives, the low unsaturation elastomer may be virtually uncrosslinked whilst the high unsaturation elastomer can have a higher crosslink density than is desirable. Modification of EPDM to either form an independent network in the EPDM phase or enforce the formation of sulfur crosslinks during vulcanization is effective. The level of crosslinking required in the EPDM phase in order to provide substantial improvements in properties of blends is modest, much lower than would be required to give acceptable properties in a single polymer vulcanizate. Blends of general purpose elastomers, such as NR and BR, do not differ significantly in either solubility parameter or degree of unsaturation and are generally considered not to be problematic. However, these often show an uneven distribution of crosslinks. Studies of the progress of crosslinking during vulcanization suggest that partition of curatives could play a role even here. The detailed view of crosslink distribution presented here is largely due to the success of a swollen-state NMR spectroscopy technique, and there is considerable scope for further advances in view of the list of combinations of elastomers which may be investigated in this way. The list is reproduced in Table IX, suitably updated to take account of recent developments. Further advances are expected; not just in respect of the investigation of new blend and curative systems, but also in the combination of the swollen-state NMR technique with other established procedures such as the use of chemical probe reagents to provide information on the type of sulfur crosslinks present in each phase of a blend.
Crystallization and Morphology of Rubber
Authors: Magill J. H. 
Published: February 2011

Abstract
Naturally occurring materials like rubber predate the development of science and engineering as we know it today. Historically, rubber and more generally elastomers, known as a class of high polymers, are versatile and useful materials. Rubber is still an elastomer of choice for many engineering applications. After decades of R&D, scientists and engineers realized that technology needs good science. This position is nicely summarized in Figure 1. This scenario brings together four main items that are essential to create and to maintain quality industry(ies). In the case of rubber, particularly natural rubber, it is not only essential to understand these individual properties, but also to comprehend the important interrelationships that contribute to material behavior. In this respect, rubber has been an enabling resource material that has served as a paradigm amongst synthetic polymers in their developmental stages. In this article crystallization of natural rubber especially, is addressed in order to provide some perspective on items that relate to the relevant areas of the pyramid. This overview is far from exhaustive on the crystallization aspects of rubber, but hopefully it strikes a balance between thermodynamics and kinetics, since each discipline has contributed significantly to improve our understanding of polyisoprenes, and in a wider sense to crystallization and morphology that helps determine properties relevant to rubber and to polymers in general.
Dynamic Mechanical Losses in Filled Poly(Dimethylsiloxane) Networks
Authors: Sharaf M. A. , Kloczkowski A. , Mark J. E. 
Published: February 2011

Abstract
This investigation focused on the study of dynamic mechanical losses in silica-filled networks of poly(dimethylsiloxane) (PDMS). Some of the samples were filled using a novel method, specifically the in situ precipitation of particulate silica either after or during network formation. Others were filled using the customary method of mechanically blending already-prepared silica into the elastomer prior to its crosslinking, and some were prepared without any filler at all. The resulting materials exhibited a variety of relaxation behaviors over the temperature range 120–260 K. The glass transition temperatures Tg showed only a slight dependence on the presence of the filler particles and crosslinks, but the filler was found to reduce both the degree and rate of crystallization for the in situ filled networks. The results obtained document how the techniques employed for incorporating particulate fillers change the viscoelastic properties of an elastomeric network, and how dynamic testing can yield a great deal of insight and useful information on the mechanical properties of polymers in general.
The Effect of Abrading Surfaces on the Wear of Rubber Tread Compounds
Authors: Ramakrishnan R. , Donovan J. A. , Medalia A. I. 
Published: February 2011

Abstract
The wear rate, produced by a modified Lambourn abrader, of rubber tread compounds, depends on the normal load, frictional force, the grit size and the number of grits per unit area of the grindstone. A preliminary model for the wear rate incorporating the grindstone characteristics, the normal and frictional force, and the fatigue exponent of the compound has been developed. The model needs further refinement but predicted the wear rate of SBR and EXXPRO™ rubber compounds well enough to be developed further. The current major limitation is accurate characterization of the grindstone.
Diffusion of Antioxidants in Rubber
Authors: Pushpa S. A. , Goonetilleke P. , Billingham N. C. 
Published: February 2011

Abstract
Migration of compounding ingredients such as antioxidants is a problem that has been recognized by rubber compounders. The literature is almost void of quantitative data in this area. Therefore an investigation of the diffusion of some commonly used phenolic antioxidants in three different rubber vulcanizates was carried out. The antioxidants were chosen so that they included a wide range of molecular weights as well as structural differences to enable us to study the effect of size and molecular nature on diffusion in the medium of rubber. The effect of crosslink density on diffusion was studied by using rubber vulcanizates of three different crosslink densities. BHT (butylated hydroxytoluene), the smallest antioxidant in the series, shows the highest diffusion coefficient. As the molecular weight of the diffusant increases the diffusion coefficient decreases. The molecules of polar nature, such as Antioxidant 754 (2,6-di-t-butyl-4-hydroxymethyl phenol), show higher diffusion coefficient compared to the nonpolar molecule of the same size, such as BHT. The crosslink densities of vulcanizates effect the diffusion of antioxidants in that there is an optimum value at which the diffusion coefficient is highest.
The Chemistry of Phenol-Formaldehyde Resin Vulcanization of EPDM: Part I. Evidence for Methylene Crosslinks
Authors: van Duin Martin , Souphanthong Aniko 
Published: February 2011

Abstract
The application of phenol-formaldehyde resins as crosslinking agents is increasing in importance due to the good high temperature properties of the corresponding vulcanizate and the use in thermoplastic vulcanizates. With respect to the chemistry of phenol-formaldehyde cure (reaction mechanism and structure of crosslink) there are still problems that have to be resolved. The reaction products of the phenol-formaldehyde resin curing of EPDM, contain 2-ethylidene norbornene (ENB) as the third monomer, have been studied. Since such an investigation is rather difficult to perform for the polymer system, a low molecular weight model for EPDM was used: 2-ethylidene norbornane (ENBH). Reaction of ENBH and a resole results in scission of the dimethylene ether bridges, i.e. in degradation of the resole into mono-, bis- and terisooctylphenol units. These are consequently converted into products, consisting of two ENBH molecules linked by mono-, bis- and terisooctylphenol units. The solid resole seems to be a technological solution for storing phenol in combination with formaldehyde. These results support the use of 2-hydroxymethylphenol (HMP) as a low molecular weight model for the resole. At low temperatures and/or short reaction times HMP oligomers (= resoles) and HMP oligomers linked to one ENBH molecule are formed, which are converted into ENBH/HMP (1:1) condensation products. The reaction products of ENBH with both the resole and HMP are shown to contain methylene linked structures, as demonstrated by the formation of monisooctylphenol crosslinks and the presence of residual unsaturation and hydroxyl groups, besides chroman linked structures. This is the first experimental evidence that during phenol-formaldehyde resin cure of rubber, formation of methylene bridges occurs.
Uniaxial Deformation of Rubber Cylinders
Authors: Mott P. H. , Roland C. M. 
Published: February 2011

Abstract
Stress, strain and optical birefringence measurements were made on elastomeric cylinders deformed in tension and compression. The birefringence data enables the actual stress to be determined even when the deformation is not homogeneous. In the absence of lubricant, uniaxially loaded rubber cylinders deviate from homogeneous deformation due to bonding of the cylinder ends. The existing analysis to correct the force-deflection curve for the effect of this sticking, strictly valid for infinitesimal strains, is premised on the idea that the deformed cylinder has a parabolic profile. Experimentally, however, it was found that slender rubber cylinders assume a much flatter profile, while maintaining constant volume, when deformed. Nevertheless, the accuracy of the stress-strain curve when the standard correction is applied turns out to be quite good, partially a result of cancellation of two, relatively small, errors. This accuracy was assessed by comparison of force-deflection data from bonded cylinders both to stress-strain data obtained on lubricated cylinders and to the stresses deduced from the measured birefringence.
A New Theoretical Approach to Cavitation in Rubber
Authors: Ganghoffer J. F. , Schultz J. 
Published: February 2011

Abstract
In order to analyse the stability and bifurcation phenomena occurring during expansion of a small void in a rubbery material, the behavior of spherical shells submitted to a combined far-field pressure and uniaxial tension has been investigated, considering a general nonlinear isotropic elastic compressible behavior of the material and without any restrictions on the shell thickness. A radial solution for the deformation gradient with a spherical symmetry has been exhibited, which is valid for any behavior law and consists of a homogeneous deformation. The three-dimensional problem is then linearized around this trivial solution, and we show the existence of a pressure interval containing the zero value, in which the solution is reduced to the trivial solution, which is therefore infenitesimally stable. When the applied pressure lies outside the stability interval, we determine the bifurcation points of the shell around the trivial solution, first when only a pressure is applied and secondly when there is an additional far-field tension, much smaller than the applied pressure. The form of the stress distribution on the boundary of the cavity suggests a possible bifurcation of the spherical solution towards a family of axisymmetric solutions. Within this hypothesis, we get a relation between the geometrical parameter of the shell (its radius and thickness), the mechanical properties of the material and the critical load.