bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Mechanical Thermal Analysis and Transmission Electron Microscopy of Elastomer Blends
Authors: Mazich K. A. , Samus M. A. , Killgoar P. C. , Plummer H. K. 
Published: February 2011

Abstract
Dynamic mechanical thermal analysis and transmission electron microscopy have been used to elucidate the structure of binary and ternary blends of NR, BIIR, and IM. Dynamic measurements at 10 Hz were able to resolve loss-tangent peaks into a major peak due to NR and a broad shoulder associated with BIIR and IM. Interpretation of these data in conjunction with electron micrographs indicate that the butyl polymers (BIIR and IM) form a second phase in a matrix of NR for compositions containing at least 67% NR. Dynamic mechanical properties and TEM micrographs of binary blends of NR with BIIR or IM show that the structure of these binary blends differ; IM forms larger, more distinct domains in the NR matrix. This difference in structure may result from the different molecular weights of the butyl polymers and the ability of BIIR to crosslink with NR. TEM micrographs of both binary blends indicate that carbon black is dispersed in the matrix material and is excluded from the isobutylene-rich domains, The two-phase structure of these blends and the partitioning of carbon black between the phases may enhance the fatigue lives of these composites. Cure temperatures in the range from 130°C to 170°C affected the properties and structure of only one blend studied in this work. This blend, an 80:20:20 mixture of NR, BIIR, and IM, respectively, was able to alter its morphology when the cure temperature was elevated. Material cured at 130°C contained domains with a wide variety of shapes and sizes; material cured at 170°C contained uniform, well-defined inclusions. This ternary blend was the only material that also exhibited a higher fatigue life when the cure temperature was raised. Achieving a well-defined dispersion in a two-phase elastomer blend apparently maximizes the fatigue life of the composite material.
Stress—Strain Fields in Compressed Elastomeric Seals and Their Extension to Fracture Mechanics
Authors: Medri Gianluca , Strozzi Antonio 
Published: February 2011

Abstract
The modeling of an elastomer in terms of hyperelastic material has been discussed. The peculiarities of the finite element method when applied to nearly incompressible materials have been underlined. The mechanical analysis of various uncracked elastomeric seals has been treated with particular regard to possible crack initiation. The theoretical aspects of fracture mechanics applied to elastomers have been discussed, and the validity of the J-integral approach has been checked against experiments. The J-integral has been computed numerically in cracked O-ring seals for various fractional compressions and crack lengths. The numerical stress field has been compared to the experimental findings. The influence of the crack length on the contact pressure profile has been considered. Various difficulties still exist in modeling efficiently the elastomeric materials and in developing suitable numerical tools. Nevertheless, it is believed that statistical predictions on the debasement in the sealing characteristics due to viscoelastic effects and to crack propagation will become shortly feasible.
Water Permeation through Elastomer Laminates, II. SBR/EPDM
Authors: Cassidy Patrick E. , Aminabhavi Tejraj M. 
Published: February 2011

Abstract
In summary, the measurements described here suggest that the temperature dependence of permeation rate had an Arrhenius behavior. Activation energies fall within the range expected for those membranes that follow activated transport mechanism. For all single elastomers, salt water exhibited higher permeation rates than did distilled water. The laminates show a directional behavior but more distinctly for distilled water than for salt water. Solubility data alone cannot, however, always account for this phenomenon.
J-Integral and Crack Opening Displacement as Crack Initiation Criteria in Rubber
Authors: Lee R. F. , Donovan J. A. 
Published: February 2011

Abstract
1. Evaluation of ∫σdδ where σ is the net section stress and δ is the deformed crack tip diameter requires only one specimen to characterize the initiation of crack growth in unfilled and carbon-black-filled NR. 2. ∫σdδ is equal to one half of the J-integral for crack growth initiation, which is identical to the Thomas tearing energy for a blunt notch. 3. The critical J-integral for crack initiation increases linearly with carbon black content. 4. The critical crack tip radius for crack initiation is independent of carbon black content, and the required crack tip region stress increases linearly with carbon black content.
Effect of Resin Components on the Reversion Process of Sulfur-Vulcanized Guayule Rubber
Authors: Sloan James M. , Maghochetti Michael J. , Zukas Walter X. 
Published: February 2011

Abstract
An effort to characterize the reversion process of guayule rubber when naturally-occurring guayule resin components are present has shown that these components act as a reversion-retarding material. The amount of reversion resistance varies as a function of temperature, concentration, and type of fatty acid. Of the three fatty acids used, linoleic acid, stearic acid, and oleic acid, linoleic acid performed the best for reversion resistance, followed by stearic acid, then oleic acid. When the temperature was increased 10°C, an increase of 15% reversion was observed. This held true for the three temperatures studied. In addition, the amount of reversion improvement upon addition was 20% reversion. In the case of curing at 150°C, this resulted in 0% reversion. The 20% resistance improvment was consistent for the 3 temperatures studied.
Theoretical Equilibrium Moduli and Swelling Extents for Elastomers Crosslinked in Solution
Authors: Queslel J. P. , Mark J. E. 
Published: February 2011

Abstract
Equilibrium elongation moduli and swelling properties have been calculated for amorphous polymer networks prepared in a diluted reference state of polymer volume fraction υ2C. The three molecular elasticity theories employed are based on (i) an idealized affine deformation model (in which the constraints on junction fluctuations are infinite), (ii) an idealized phantom chain model (in which the constraints are absent), and (iii) the more realistic Flory-Erman theory (in which the constraints vary with crosslinking conditions, degree of swelling, and extent of elongation). A discussion of the dependence of the constraint parameter κ on υ2C is given, and is applied to the calculation of stress-strain isotherms in elongation specifically for cis-polyisoprene cured with dicumyl peroxide. The experimental dependence of κ on υ2C investigated by Erman and Mark was found to be similar to the dependence of the plateau modulus on dilution, and this is consistent with the constrained contour model proposed by Erman and Monnerie.
Equilibrium Swelling of Polyurethane Elastomers
Authors: Oberth Adolf E. 
Published: February 2011

Abstract
Equilibrium swelling of randomly crosslinked elastomers is in satisfactory agreement with a model that considers them to be aggregates of equivalent spheres whose diameter is proportional to Mc1/2. Solvation expands these spheres, the extent of expansion being proportional to the diameter and the strength of the solvent-polymer interaction, but is independent of the number of effective chains per volume unit of the elastomer. A potential mechanistic explanation assumes that the solvent molecules form a weak complex with the elements of the polymeric chain, which forces the segments out of their equilibrium position, thus creating a force that opposes further solvation. Both forces have a very short range and are effective only in the individual segment that has formed the polymer-solvent complex. The magnitude of the extension of the whole chain will be proportional to the number of chain segments undergoing solvation, which leads to the mathematical relationship that forms the basis of Equation (6). Since the swollen volume is many times the volume of the network rubber, it is clear that only a (comparatively) small fraction of the solvent molecules will interact directly with the polymer, many of which will just fill the space created by the expanding network. In weak solvents, or at very high levels of crosslinking, where the swelling volumes are small, the extent of swelling is likely to depend on the polymer content, and the presented mechanism does not apply.
A Study of Permeation and Diffusion of Aqueous Salt Solutions through Polyurethane and Polysiloxane and Their Laminates
Authors: Wells Lisa A. , Cassidy P. E. , Aminabhavi T. M. , Perry R. B. 
Published: February 2011

Abstract
Effect of ion size on water permeation through polyurethane, polysiloxane, and their laminates has been studied. The results of these studies for the polyurethane membranes correlated well with the reported values of water permeation through a variety of other polyurethane elastomers. Permeation rates and the Arrhenius relationship of polyurethane and polysiloxane membranes were found to be similar. Solute size showed no observable effect on water permeation through polyurethane, polysiloxane, or their bilayer laminates, within experimental error. A small effect of solute size was observed for diffusion of water into polyurethane. Permeation rates of the bilayer laminates demonstrated a small directional dependence or “valving” effect. In the light of this evidence, it may be suggested that highly permeable systems, such as polyurethane and polysiloxane, are relatively insensitive to permeant composition.
Structure and Dynamic Properties of Solution SBR Coupled with Tin Compounds
Authors: Tsutsumi F. , Sakakibara M. , Oshima N. 
Published: February 2011

Abstract
The relation between the structure of the Solution SBR and the dynamic properties of carbon-black-filled SBR vulcanizates have been studied. The results obtained were as follows: 1. The hysteresis of the Solution-SBR vulcanizates was reduced markedly by the introduction of tin—carbon bonds at the polymer chain end. 2. Among the structures of tin—carbon bonds, tin-butadienyl bonds were much more effective for the reduction of hysteresis than were tin—styryl bonds. 3. Solution SBR coupled with tin compounds with molecular weight of less than 105 was not so effective for the reduction of hysteresis. Furthermore, the mechanism of the improvement of dynamic properties was investigated. It was found that polymer—carbon-black bonds were formed through the reaction of tin—carbon bonds with the functional groups of carbon black. From model reactions, it is suggested that quinone groups on carbon black are involved.
Products and Mechanism of the Thermal Reaction between 2,4-Dichlorobenzoyl Peroxide and n-Pentadecane, an Approximation of the Crosslinking of Silicone Rubbers
Authors: van Drumpt J. D. 
Published: February 2011

Abstract
Unlike most organic rubbers, viscoelastic silicone rubbers can be either very difficult or impossible to crosslink with sulfur cure systems. Although Pt-catalyzed addition reactions and high-energy radiation curing techniques are available, most heat curing of silicone rubbers is done by means of organic peroxides. Of those, 2,4-dichlorobenzoyl peroxide is the most widely used, due to its versatility, its speed, and the low amount of gaseous decomposition products which it produces. The latter fact allows it to be used for pressureless vulcanization. In fact, 2,4-dichlorobenzoyl peroxide is the only peroxide available on the market that is successfully employed for hot air vulcanization (HAV) of extruded profiles and tubing. In addition, it is widely used in injection, compression, and transfer molding of both vinyl and nonvinyl containing gums. In spite of its widespread use, little factual knowledge is available about the reaction mechanism and products of this peroxide. This is mainly due to the analytical inaccessibility of the crosslinked silicone rubber end product and the evaporation losses caused by processing and curing in (partly) open systems. The present study addresses these issues by using a closed model system. Although many low-molecular-weight polydimethylsiloxanes are available, n-pentadecane was preferred as the substrate because it allowed a direct comparison to be made with similar studies done with other crosslinking peroxides (see e.g., References 2 and 3). The C—H bond strengths in this saturated alkane (410 kJ/mol for primary and 385 kJ/mol for secondary H atoms) were felt, to be close enough to that in polydimethylsiloxanes (approximately 412 kJ/mol) to make it an acceptable model substance for the latter. The system also allowed an estimate to be made of the amount of polychlorobiphenyls (PCBs) that might be formed under normal cure conditions.
Phase Behavior of Polymer Blends
Authors: Han Charles C. 
Published: February 2011

Abstract
We have demonstrated in two separate cases that SANS experiments can be used to obtain binary interaction parameters effectively and accurately. With measured χ as a function of composition and temperature, the free energy of mixing can be obtained at least numerically. The phase diagram including spinodal curves and cloud-point curves can be predicted. The second derivative of free energy of mixing w.r.t. composition, ∂2ƒ/∂ϕ2, can be used directly in the kinetics studies of spinodal decomposition. In the polybutadiene/polybutadiene case, individual pair interaction parameters can be separated out. Microstructure effect is the main contribution to the incompatibility of the blends. Nevertheless, with the use of the random copolymer theory, phase behavior can be predicted.
Composition Distribution of Acrylonitrile-Butadiene Copolymers as Analyzed by High-Performance Liquid Chromatography
Authors: Asada N. , Hosozawa H. , Toyoda A. , Sato H. 
Published: February 2011

Abstract
The separation of acrylonitrile-butadiene copolymer (NBR) was investigated by high-performance liquid chromatography (HPLC). The copolymer was most successfully separated on the basis of chemical composition by using crosslinked 2-chloroacrylonitrile gel as the stationary phase and with a gradient elution of chloroform/n-hexane. The separation was found to be carried out by an adsorption mechanism and essentially independent of the molecular weight of the sample. The observed chemical composition distributions (CCD) agreed with those calculated from the copolymerization theory.
Origin of the Self-Reinforcement in PDMS Bimodal Networks
Authors: Smith T. L. , Haidar B. , Hedrick J. L. 
Published: February 2011

Abstract
For three series of bimodal networks, the stress-relaxation rates and the tearing energies were shown to exhibit maxima at about the same concentrations of short chains as those at which the tensile strengths, reported earlier, also exhibit maxima. These findings clearly show that the reinforcement produced by the addition of short chains results because chain mobility is reduced substantially, especially when the concentration of short chains is 30 to 40% by weight (Figures 1 and 5). For each series of bimodal networks prepared in our laboratory, the maximum tensile strength also occurs when the concentration of short chains is about 30% by weight. When a bimodal network is deformed progressively, deformation occurs in the long chains moving through the matrix of short chains. Also, the network junctions and the attached short chains must be dragged along with the deforming long chains. It is probable that the low mobility of the chains (high dissipation of energy), which accounts for the high tensile strengths, especially in networks having 30% or so by weight of short chains, results primarily from the energy dissipation associated with such complex molecular rearrangements. It was also shown that the maximum tensile strength in a series of networks increases with an increase in the difference between the molecular weights of the long and short chains, or as shown in Figure 7, with a decrease in MS/ML.
Biaxial Extension Studies Using Inflation of Sheets of Unimodal Model Networks
Authors: Xu P. , Mark J. E. 
Published: February 2011

Abstract
Measurements of uniaxial extension and compression were made on model poly(dimethylsiloxane) (PDMS) [−Si(CH3)2−O−]x networks to examine the molecular theories of rubber elasticity. The stress-strain isotherms showed that the Flory-Erman theory of rubber elasticity is in good agreement with experimental data from extension to compression (α−1: 0.3–13), while the Mooney-Rivlin relation is useful only in a specific region of extension ratio (α−1: 0.3–0.8). The experimental results strongly support the theory of Flory-Erman, rather than those of phantom and affine networks. It is thus evident that the Flory-Erman theory of rubber elasticity is the more nearly correct.
Tandem Mass Spectrometry (MS/MS) for Analysis of Organic Additives in an Uncured Rubber Compound
Authors: Lattimer R. P. , Muenster H. , Budzikiewicz H. 
Published: February 2011

Abstract
In this study, we examined the feasibility of obtaining MS/MS data for organic additives in an uncured rubber compound using several different ionization methods. EI-MS/MS worked well for those additives that gave intense molecular ions (M+·) via this mode of ionization. CI-MS/MS also worked quite well for most additives; the CI MH+ ion currents were generally quite intense and stable over a long period of time. Although fragmentation patterns for MH+ ions are different from those obtained from M+· ions, the fragments are still good diagnostic tools for identifying the original molecule. On the other hand, the FI- and FD-MS/MS analyses of these rubber samples were generally not very satisfactory. This was due to the fact that FI/FD ion currents were too weak and unstable to give daughter-ion spectra with good S/N. It may be concluded that the best way to detect and identify typical organic additives in a compounded rubber is to use a combination of EI- and CI-MS/MS. In this study, intact accelerators were successfully analyzed by MS/MS. The two accelerators in this particular rubber (OBTS and DPG) could be confirmed quite readily by daughter-ion analysis of their intense MH+ ions (CI-MS/MS). Daughter-ion analyses of M+· obtained by either EI, FI or FD modes were not very successful, however. In EI, the difficulty is that molecular ions are quite weak (or even absent) for typical rubber curatives. In FI and FD, on the other hand, a very large proportion of the ion current for accelerators resides in the molecular ion. The difficulty here is that the total ion current produced by FI or FD is rather low. The MS/MS approach has proven to be very useful for direct analysis of organic additives in rubber compounds. The principal advantage in using MS/MS is that more information is available from mixtures than can be obtained by direct analysis using conventional mass spectral methods. The MS/MS technique is also rapid experimentally compared to other techniques for mixture analysis such as GC/MS, LC/MS, or high resolution (AC-MS). Finally, since MS/MS involves two stages of mass analysis, it leads to a great reduction in the chemical noise associated with single-stage mass spectrometry. This leads to the facile confirmation of the presence (or absence) of specific components in a complex mixture.
Solid-State NMR of Elastomers
Authors: Kinsey Robert A. 
Published: February 2011

Abstract
The versatility of solid state NMR for the characterization of elastomers and elastomer composites has been demonstrated. NMR can be used as an analytical tool for identifying the elastomer(s) present (including the sequence distribution and tacticity), measuring crosslink levels, and monitoring chemical modifications. In addition, with relaxation measurements, NMR provides direct physical insight into the dynamics, and hence the spatial interactions of elastomeric systems. The interfacial regions of heterogeneous systems such as IPNs, filled elastomers, and block copolymers can be probed. A variety of NMR parameters can be correlated with physical properties. Future studies will extend the use of variable temperature and high magnetic field strength measurements, as well as utilize the growing number of two-dimensional experiments. The use of solid state H-l NMR should increase as instrumentation progresses, complementing the heteronuclear work. Solid H-l NMR offers significant sensitivity increases over C-13 NMR, but with decreased resolution. N-15 NMR studies have been recently performed at natural abundance with rigid polymers, and will likely be useful for characterizing elastomers.
A Novel Fluorocarbon Elastomer for High-Temperature Sealing Applications in Aggressive Motor-Oil Environments
Authors: Grootaert W. M. , Kolb R. E. , Worm A. T. 
Published: February 2011

Abstract
The tendency in the automotive industry to use smaller engines has resulted in a situation where lubricating oils are exposed to higher operating temperatures. This is especially the case in countries where there is no restriction on highway speed. Amine-based additives present in the oils (e.g., as dispersants and corrosion inhibitors) tend to slowly attack the conventional fluorocarbon elastomer seals under these conditions. As a result of that attack, the seal becomes brittle and eventually fails. A novel fluorocarbon elastomer of vinylidene fluoride, tetrafluoroethylene, and propylene has shown excellent aging behavior in the laboratory toward many aggressive engine oils at elevated temperature. Its improved resistance as compared to conventional fluorocarbon elastomers is attributed to the replacement of hexafluoropropylene with propylene.
Prediction of Bound-Rubber Modulus by Clausius—Mossotti Approximation
Authors: Scobbo J. J. 
Published: February 2011

Abstract
The Clausius—Mossotti approximation has been used to determine the modulus of bound rubber attached to carbon black in a gum-rubber/carbon-black compound. The effective hydrodynamic concentration of the carbon-black/bound-rubber structure was first determined based on the assumption of spherical filler particles with a uniform layer of bound rubber on the surface. The true carbon-black concentration was then subtracted from this concentration, and a three component modeling scheme was used. The three components were considered to be bound-rubber, carbon black, and gum-rubber matrix. The Clausius—Mossotti approximation was used to determine the bound-rubber modulus that would give the same compound modulus based on equivalent hydrodynamic volume. Results indicate that bound-rubber concentration decreases with increasing strain. At zero strain, the bound-rubber concentration is approximately equal to the carbon-black concentration. Modulus values of bound rubber were found to be 3 to 4 times greater than gum-modulus values at very low strains. The relatively greater magnitude of bound-rubber modulus decreased with increasing strain until the filler effect appears to be almost purely hydrodynamic. The electromagnetic theory-based Clausius—Mossotti model was found to predict bound-rubber moduli that were in agreement with a mechanical model, the Kerner model.