bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Reptating Species on the Tear Strength of Elastomeric Networks
Authors: Hamed G. R. , Ogbimi F. 
Published: February 2011

Abstract
The “snake-like” motion which an unattached polymeric chain undergoes as it diffuses through a molecular network has been termed “reptation”. Several studies of the low-strain dynamic properties of networks containing reptating chains have been carried out. At relatively high temperatures or low rates of deformation, reptating species may contribute greatly to the mechanical loss of elastomeric networks because the reptating chains are sufficiently mobile to adjust their conformations greatly, and this motion causes the dissipation of mechanical energy into heat. On the other hand, at sufficiently low temperatures or high rates of testing, entanglement couplings of the reptating chains with the network (or with themselves) behave essentially as crosslink points. In this case, the dynamic mechanical properties of networks containing reptating chains are virtually the same as those without reptating chains. Although the low-strain viscoelastic properties of networks containing reptating chains have been studied, there has been no systematic investigation of the tear strength of such systems. It is the purpose of this paper to report such a study. Mixtures of butyl rubber (IIR) with polyisobutylene (PIB) were crosslinked with sulfur, leaving the PIB molecules free to reptate in the butyl rubber networks. The trouser tear strengths of these materials were then determined as a function of the molecular weight and concentration of the reptating species, the crosslink density of the host IIR network, and the test temperature. In addition, the tear strengths of networks in which the IIR was mixed with inert low molecular weight diluents (of varying solvent power) before vulcanization were also measured.
Quinoid Curing of Butyl and Natural Rubbers
Authors: Gan L. M. , Chew C. H. 
Published: February 2011

Abstract
The vulcanization of butyl and natural rubbers by p-dinitrosobenzene (DNB), p-quinone dioxime (GMF) and p-quinone dioxime dibenzoate (dibenzo GMF) oxidized by various oxidants was investigated. Good curing efficiency (E=1.2) was achieved for a butyl system containing GMF or dibenzo GMF oxidized by red lead (Pb3O4). It was estimated that about 85% of the combined quinoid agent was in the form of crosslinks and the remaining 15% might be present as pendant groups. In contrast to butyl rubber, NR could also be cured slowly by GMF or dibenzo GMF alone. Simple ZnO or PbO was effective in activating dibenzo GMF to produce quinoid-NR vulcanizates with good scorch safety. But the highest crosslink density was obtained from equimolar dibenzo GMF/Pb3O4. Low crosslinking efficiency (E=3–6) was generally observed in the quinoid-NR systems. Quinoid vulcanization mechanisms are discussed. The crosslinks consist mainly of the anil structure in the butyl system, while azoxy crosslinks might also be present in the NR system.
Emulsion Polymerized Polydimethylsiloxane
Authors: Graivek Daniel , Huebner David J. , Saam John C. 
Published: February 2011

Abstract
The observations are consistent with the formation of grafts of hydrophilic silicates to the silanol chain ends at the surface of the PDMS emulsion particles prior to removal of the water. The silicates may be introduced into the system directly or through the alkaline colloidal silica, which contains appreciable amounts of dissolved silicates. Monomeric, or possibly dimeric, silicate grafted to more than one chain end could migrate to the interior of the PDMS emulsion particle to form further crosslinks. Grafts to higher molecular weight silicates and silicate grafts bearing anionic change would be solvated with water and tend to remain at the oil-water interface. These grafts can provide additional stabilization to the cured particles. The dialkyltin carboxylate is pictured as playing a role in the grafting and crosslinking process. Evaporation of the water would eventually cause collapse of the stabilizing elements surrounding the PDMS particles to allow contact between particles of silica and the silicate grafts coating the particles of PDMS. The ensuing formation of interparticle hydrogen bonds and siloxane bonds, which can occur readily at room temperature under alkaline conditions, completes the formation of the elastomer network. This is represented in Figure 8. The resulting elastomeric network thus consists of the original emulsion particles, now crosslinked, which are surrounded by a hydrophilic hard phase of silicates and silica. In some aspects, this resembles the morphology proposed for films from dried natural latex.
Vulcanization Studies of Elastomers Using Solid-State Carbon-13 NMR
Authors: Patterson Dwight J. , Koenig Jack L. , Shelton J. Reid 
Published: February 2011

Abstract
With the use of solid state carbon-13 NMR, changes in the structure of natural rubber and cis-polybutadiene were observed spectroscopically. Cis-trans conversion has been shown to occur in the naturaal rubber by the rearrangement of the allylic free radical. At least four structurally different methyl groups have been detected in the crosslinking of natural rubber by dicumyl peroxide, which indicates that the simple combination of allyic free radical is an oversimplification of the curing process. Quaternary aliphatic carbons have been detected which results from double bond migration. Polybutadiene showed only methine and methylene carbons present in the crosslinked network with a small amount of methyl end-groups. The increase in the line width of the highly crosslinked elastomers was shown to be dominated by the carbon-hydrogen static dipolar interaction. Fourier-transform infrared analysis observed the formation of a molecular complex between dicumyl peroxide and polybutadiene. The formation of trans double bonds was observed in the infrared spectra of polybutadiene. Weak broad bands around 1320 cm−1 were observed in the difference spectrum of cured rubbers and were assigned to carbon-carbon crosslinks. From the structural interpretation of spectra obtained from solid state carbon-13 NMR and Fourier-transform infrared, models are proposed for the crosslinked networks of natural rubber and polybutadiene, obtained from peroxide vulcaniation.
Effect of Cure Systems and Reinforcing Fillers on Dynamic Mechanical Properties of Chlorobutyl Elastomers for Potential Vibration-Control Applications
Authors: Capps Rodger N. 
Published: February 2011

Abstract
The effects of four different types of cure systems upon the physical and viscoelastic properties of chlorobutyl elastomers have been investigated. Five different types of carbon black fillers have also been evaluated. Effects of carbon black loading were also studied. The basic conclusions that may be drawn from the experimental determination of the viscoelastic properties of these elastomers and the subsequent use of these to evaluate their potential in various vibration-control applications are as follows: (1) Both the red lead-thiourea cure system, and the resin-cure system give vulcanizates with very similar physical and dynamic mechanical properties. Use of a resin cure is preferable to a red lead-thiourea cure due to the much shorter cure time and lower cure temperature. (2) Chlorobutyl elastomers possess suitable viscoelastic properties for vibration-control applications, due to the diffuse nature of the glass-rubber transition in this class of polymer. Use of other types of fillers, such as silane-treated mica, may be useful in further broadening the temperature-frequency damping range of these materials by introducing additional damping mechanisms. (3) Increased loading of a moderately reinforcing carbon black improves the transmissibility and extensional damping characteristics of CIIRs. An intermediate loading of approximately 35 phr appears to work best for the constrained-layer configuration considered here. (4) An experimental determination of the temperature and frequency dependence of the viscoelastic properties of polymeric materials, coupled with the type of modeling described here, provides a convenient means of assessing the relative merits of various types of polymeric materials in the design of vibration-control systems.
Effects of Storage on the Molecular Weight of Rubber Contained in Guayule
Authors: Black L. T. , Swanson C. L. , Hamerstrand G. E. 
Published: February 2011

Abstract
Although this was a limited study based on only two guayule varieties, the trends relating to rubber degradation with storage time and temperature condition are clear. Whole guayule plants, and especially chopped guayule awaiting processing, cannot be stored for long periods at elevated temperatures without at least partial degradation of the molecular weight of the rubber in the plant. These studies are now being expanded to determine if the observed differences in stability are, in fact, attributable to variety or are the result of postharvest treatment or agronomic practices.
On the Origin of Strain-Induced Crystallization
Authors: Göritz D. , Kiss M. 
Published: February 2011

Abstract
DSC measurements on stretched polybutadiene held at fixed length show two melting regions. The first is shifted a small amount to higher temperatures relative to the isotropic endotherms. The occurrence of two melting regions is considered to be evidence for an inhomogeneous deformation of the rubber. The melting point increases on stretching are taken to be due to entropy effects.
Effect of Butyl Rubber Coating on Accelerated Aging of Natural Rubber
Authors: Stenberg Bengt , Peterson Lars-Olof , Flink Per , Björk Folke 
Published: February 2011

Abstract
From these results it is possible to draw the following conclusions: The primary protection against thermo-oxidative degradation comes from the butyl coating. The butyl coating works mainly by stopping diffusion of oxygen from the surrounding air, which is more important than stopping the antioxidant from diffusing out of the rubber, since the antioxidant effect is small.
Compression of Rubber Layers Bonded between Two Parallel Rigid Cylinders or between Two Rigid Spheres
Authors: Gent A. N. , Park Byoungkyeu 
Published: February 2011

Abstract
An approximate theoretical treatment is presented for small compressions of a rubber layer bonded between two opposed curved rigid surfaces, cylindrical or spherical in shape. The deformation is treated in two parts: a simple compression; and shearing deformations necessary to maintain zero slip at the bonded surfaces. Forces and hydrostatic pressures due to the second deformation are found to be the major terms for thin layers. Predicted compression stiffnesses are compared with measured values for various initial separations of the two rigid surfaces (and hence various thicknesses of the rubber layers).
Extensibility of Black Filled Elastomers
Authors: Ahagon Asahiro 
Published: February 2011

Abstract
Unique empirical relations are found to exist between the extension ratio at break λb and the crosslink density ν λb ∝ ν−0.75 in the absence of gross strain induced crystallization, and λb ∝ ν−0.2 in the presence of gross strain-induced crystallization. With black-filled elastomers, the modulus at 100% strain, M100, is proportional to the crosslink density over a wide temperature range. Thus, unique empirical relations exist between λb and M100 of black-filled elastomers; λb ∝ M100−0.75 in the absence of gross strain-induced crystallization, and λb ∝ M100−0.2 in the presence of gross strain-induced crystallization. The proportionality constants can be used as convenient measures of the extensibility in material evaluation on a constant modulus basis.
Fatigue Crack Growth in High Load Capacity Rubber Laminates
Authors: Stevenson A. 
Published: February 2011

Abstract
The main conclusion from the work reported here is that the rate of fatigue crack growth in high load capacity and high shape factor rubber/steel laminates loaded in compression can be predicted from a tearing energy (i.e., fracture mechanics) theory of fracture. This conclusion is not just a point of scientific interest but is potentially of practical value in the design of many rubber engineering components. There is now a growing body of evidence that by adopting suitable simplifying assumptions, the fracture mechanics approach can successfully describe the fracture behaviour of rubber composites even when the detailed stress distributions are complex. A very similar approach has been successful in the study of fracture in 2-ply rubber-cord laminates—a situation that would at first sight seem intractable. These results encourage confidence that fracture mechanics could become much more widely used as a basis for the design of rubber engineering components than it is at present.
Measurement of Dynamic Bulk Modulus and Phase Angle Using ESPI
Authors: Holownia B. P. , Rowland A. C. 
Published: February 2011

Abstract
The measurement of the dynamic bulk modulus of elastomers by the direct method using ESPI has been achieved within the frequency range of 50–1000 Hz. The two types of Nitrile rubbers tested show that the dynamic bulk modulus increases with frequency, but the rate of increase depends on the type of rubber used. A novel method of measuring the phase angle using ESPI was successful in principle, although the resolution error on the oscilloscope prevented definite conclusions being reached regarding its variation with frequency.
Test of Strain-Time Correspondence Principle with Gel-Containing Elastomers
Authors: Nakajima N. , Harrell E. R. 
Published: February 2011

Abstract
With four NBR samples and one EPR, oscillatory measurements and stress-growth measurements were performed, the former being at very small deformation and the latter leading to large deformation. The Rheometrics mechanical spectrometer was used with a cone-plate fixture. The temperature was 100°C. The stress-growth data of NBR's, converted to complex viscosity-frequency data through the application of stress-time correspondence principle, were in good agreement with those observed in the oscillatory measurement. Thus, the stress-growth data including the large deformation were “linearized” to form a master curve. With the EPR sample, such a linearization was not necessary. The stress-growth data were adequately treated with the linear viscoelastic theory up to shear stresses approaching the steady state. The difference in behavior between the NBR's and EPR is caused by differences in type and extent of long branching and gel present in the samples.
Butyl Networks Containing Unattached Polyisobutylene Chains: Part II, Correlation of Tear, Tensile, and Hysteretic Properties
Authors: Hamed G. R. , Ogbimi F. 
Published: February 2011

Abstract
Butyl networks containing either unattached polyisobutylene chains or a low-molecular-weight plasticizer have been made by crosslinking butyl rubber in the presence of one of these diluents. With dodecane as a plasticizer, tear strength is reduced both because of a decrease in the density of load-bearing chains and diminished hysteresis. On the other hand, when the diluent is a high-molecular-weight polyisobutylene, tear strength is enhanced if the test rate is sufficiently high. In this case, the polyisobutylene chains are load bearing (at least initially) before slipping at higher strains to relieve local crack-tip stresses and blunt the propagating tear. This hysteretic mechanism delays the onset of crack propagation, thereby enhancing the fracture energy. However, at low tear rates, in which there is adequate time for the unattached chains to relax such that they bear little load and hysteresis is minimized, tear strength decreases with increasing free-chain content—much the same as occurs with a low-molecular-weight diluent. Finally, under conditions in which the average propagating tearing energy is enhanced for the butyl-polyisobutylene system, the initiation tearing energy is increased only moderately. This suggests that crack-tip blunting during steady-state tearing is at least partially responsible for increases in strength in the presence of free chains.
The Mechanics of Short Fiber-Reinforced Composites: A Review
Authors: Abrate S. 
Published: February 2011

Abstract
Proper constitutive equations and transformation laws to describe short-fiber-reinforced composites have been reviewed. The mechanisms of load transfer between matrix and fibers have been presented. Micromechanics analyses were discussed in order to predict mechanical properties of the composite given those of the constituents. Such approaches have been used successfully for cord-rubber and particulate-filled elastomeric composites. The use of such methods for short-fiber reinforcement has been limited so far. The problem is more complex in this case, but the need for a reliable method is even stronger in order to evaluate the influence of a parameter change on the various mechanical properties. Elastomeric composites pose a greater change due to the large ratio of fiber-to-matrix moduli, and predictions may not always be accurate. However, the interest of micromechanics approaches is that they allow determination of the effect of a perturbation in the parameters about a given level. Areas for future work include the development of micromechanics methods to determine viscoelastic constants and strength under various loading conditions. The development of a multiaxial strength criterion is needed, and basic fatigue failure mechanisms have to be studied.
Bound Rubber and Carbon Black Reinforcement
Authors: Dannenberg E. M. 
Published: February 2011

Abstract
The first description of the bound rubber phenomenon was by Twiss in 1925, who made the observation that the resistance of carbon black-natural rubber mixes to solvents was related to improved mechanical properties. Boiry studied many of the factors influencing the insolubilization of NR by fillers including type and amount of fillers, and mixing and testing variables. In 1937 J. H. Fielding of Goodyear developed a so-called “bound rubber” test because of his interest in the possibility of chemical bond formation between fillers and rubber. During the start of the U.S. synthetic rubber program, Baker and Walker reported in 1945 an insolubilization of SBR when mixed with carbon black significantly greater than the amount of normal gel in the unfilled elastomer. They were also the first to report that the amount of gel increased with increasing molecular weight and that a selective adsorption of high molecular weight material occurred. Since that time, many investigations have confirmed these findings with other elastomers, and theories of “bound rubber” formation have been based on these observations. The early concept that “bound rubber” is a gel of carbon black particles held together in a three-dimensional lattice by longer interparticle polymer molecules is still valid. The nature of the segmental attachments of the polymer molecules to the filler surfaces now appears to be both physical and chemical, depending upon filler surface activity and chemical functionality, and the chemical composition and functionality of the elastomer. Regardless of the type of interaction, the bonding is essentially permanent and can only be disrupted by extraction with good solvents at high temperatures.
Chemical Stress Relaxation of NR Networks Prepared in the Swollen State
Authors: Suh Kyung-Do , Oikawa Hidetoshi , Murakami Kenkichi 
Published: February 2011

Abstract
From the experimental results of the present investigation, it is apparent that two kinds of networks which have a different three-dimensional network structure give quite different behavior of chemical stress relaxation, even if both networks have the same network chain density. The difference in three-dimensional network structure for the two kinds of rubber arises from the degree of entanglement, which changes with the concentration of the polymer chains prior to the crosslinking process. The direct cause of chemical relaxation is due to the scission of network chains by degradation, whereas the total relaxation is caused by the change of geometrical conformation of network chains. This then casts doubt on the basic concept of chemorheology which is represented by Equation 2.
New Extensional Rheometer for Elongational Viscosity and Birefringence Measurements: Experimental Results and Interpretation
Authors: Froelich D. , Muller R. , Zang Y. H. 
Published: February 2011

Abstract
This study shows that by using the recoverable strain, one can represent the elongational viscosity ηe=σe/˙ε as a linear function of the quantity λr2−λr−1, characteristic of a neo-Hookian material. The elongational viscosity is then the sum of two contributions: One is related to the entropic elasticity of the chains through the recoverable deformation of the sample. The other is related to the shear viscosity at a shear rate equivalent to the extensional strain rate. In absence of a simple theoretical justification for such an equation, more experiments are being undertaken with different polymers and rubbers in order to understand how the recoverable strain is related to the chemical structure of the chain and to check the generality of the equation.
Visualization of Textile Reinforcing Materials in Cord-Rubber Composites after Dissolution of the Rubber with Peracids
Authors: van Blokland P. H. G. M. 
Published: February 2011

Abstract
The examples illustrate that the dissolution method is a helpful tool for making damage to cords visible both in laboratory tests and in reinforced rubber goods that have been used in practice. However, from these examples, the conclusion may not be drawn that the damage shown is characteristic of the test or type of reinforcing material. After laboratory testing, a considerable amount of damage can be found, and the examples only serve to show the suitability of peracids for the removal of vulcanized rubber from the cords. To understand the fatigue mechanisms, a lot of work is still required.
Temperature Dependence of Viscoelastic Properties of Carbon-Black-Filled Rubbers in Small Shearing Deformations
Authors: Arai Koichi , Ferry John D. 
Published: February 2011

Abstract
Measurements of dynamic storage and loss shear moduli G′ and G″ (0.12 to 2 Hz) and shear relaxation modulus G(t) (up to 104 s) have been made on six vulcanized and one unvulcanized carbon-black-filled rubber compounds over a temperature range from −22.5° to 63°C. The maximum shear strain in the oscillatory deformations was less than 0.005 and in the stress relaxation measurements, 0.015. The temperature dependence of viscoelastic properties could not be fully described in terms of horizontal shifts (αT) of logarithmic time or frequency scales. It could, however, be largely described by vertical shifts (ST) corresponding to uniform temperature dependence of the magnitudes of contributions to modulus from a spectrum of relaxation mechanisms. There were some departures from this behavior, especially in a blend containing two rubber species and in the unvulcanized compound at long times. The temperature dependence of the ST shift factors followed the van't Hoff equation with values of ΔH from 5.9 to 14.7 kJ/mole, attributable to a heat of dissociation of contacts between particle aggregates. The slow relaxation over many logarithmic decades of time scale in the rubbery zone of viscoelastic behavior is attributed to adjustments of such contacts by Brownian motion, which leave the density of the structure unchanged as shown by constancy of the differential dynamic modulus measured by superposed small oscillating deformations.
The Effect of Cure Variables on Cis/Trans Isomerization in Carbon-Black-Reinforced Cis-1,4-Polybutadiene
Authors: Devlin Edward F. 
Published: February 2011

Abstract
This work confirms the results that Corish has published on gum vulcanizates. While the carbon-black-reinforced stock apparently cures at a faster rate at this temperature than the gum vulcanizates did at 273°F (134°C), the observed trends and the extent of isomerization (7%) are in agreement.