bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Heating and Cooling Rates on the Structure of Carbon Black Particles
Authors: Zerda T. W. , Xu W. , Yang H. , Gerspacher M. 
Published: February 2011

Abstract
The effects of heating and cooling rates on the structure of N660 and N299 carbon black particles have been investigated using Raman spectroscopy, X-ray scattering, and the BET technique. Carbon blacks were kept at 2700 K for various lengths of time and next cooled down at different rates. The size of crystallites and the surface roughness of the particles have been determined for these different treatment schedules. The fractal dimension decreases from 2.2 for untreated samples to 2.0 for samples heat treated to 1300 K. Cooling rates do not affect the surface roughness. However, rapid cooling reduces crystallite sizes. We postulate that the surface of carbon particles is composed of crystallites and amorphous carbon. The amount of amorphous carbon depends on the thermal treatment. The role of amorphous carbon in determining reinforcing properties of carbon blacks in tires is discussed.
Origin of Characteristic Properties of Natural Rubber—Effect of Fatty Acids on Crystallization of cis-1,4-Polyisoprene
Authors: Kakubo Takashi , Matsuura Ai , Kawahara Seiichi , Tanaka Yasuyuki 
Published: February 2011

Abstract
Natural rubber (NR) contains linked fatty acids, composed of mainly saturated fatty acids, in conjunction with a mixture of free saturated and unsaturated fatty acids. The crystallization of synthetic cis-1,4-polyisoprene (IR) is accelerated by the addition of 1 wt % mixture of saturated fatty acid as a nucleating agent and unsaturated fatty acid as a plasticizer. As an NR model, IR was esterified with stearic acid selectively at the 3,4-isoprene units after introduction of hydroxyl group by hydroboration. The linked stearoyl group stimulated the crystallization of IR at −25 °C, while linked fatty acids other than stearoyl group showed no stimulating effect on the crystallization. The addition of methyl linoleate to the stearoyl-esterified IR gave the highest rate of crystallization at −25°C. A rapid crystallization of NR is presumed to originate from the mixed saturated and unsaturated fatty acids composition present and the presence of saturated fatty acids linked to NR.
Crack Growth in Twisted Rubber Disks. Part II: Experimental Results
Authors: De D. K. , Gent A. N. 
Published: February 2011

Abstract
A simple torsion test is described in which a thin bonded rubber disk is subjected to repeated torsional strains by rotating one end-piece with respect to the other through a fixed angle. An initial circumferential cut then grows inwards as a fatigue crack. From measurements of crack depth as a function of number of strain cycles, relations are obtained for the rate of crack growth dc/dn vs. fracture energy G for three representative rubber compounds: unfilled natural rubber, unfilled SBR and a carbon-black-filled SBR. The results are closely similar in all cases to previously-published values, obtained from tensile fatigue experiments. This is an important finding, because the present specimen is subjected to simple shear strains and the agreement obtained validates the use of a fracture energy criterion for crack growth under complex states of strain. Moreover, the test method itself has marked advantages. The strain cycle is well-defined, even for relaxing materials. The crack slows as the test proceeds allowing a considerable range of G values, of the order of 10 to 1, to be examined in a single experiment. The effect of complex strain cycles, passing through zero or reversing, and the effect of superimposed tensile or compressive strains, can also be explored.
NMR of Tissues Exposed to Polysiloxane Gels
Authors: Garrido Leoncio 
Published: February 2011

Abstract
Silicone (polysiloxanes) gel-filled implants have been widely used for biomedical applications, mainly because they were considered to be nonbiodegradable. However, increasing concern about the health implications of polysiloxane exposure for women with silicone gel-filled breast implants has prompted interest to study the biochemistry of implanted polysiloxanes. The purpose of this work is to investigate the migration of polysiloxanes from the implant to local and distant sites and their chemical modification in living systems. Tissues from animals and humans exposed to polysiloxane gel implants are studied in vivo using proton NMR localized spectroscopy, and in vitro with proton and 29Si magic angle spinning (MAS) NMR spectroscopy. This work demonstrates that free polysiloxanes present in the gel-filled implants migrate to surrounding tissues and distant organs, such as the liver. In addition, 29Si NMR spectra of metabolically active tissues (liver) show the presence of chemically unchanged polysiloxanes and other silicon-containing compounds (silica) which suggest that these polymers are biodegradable.
Plasticization of Polyolefin Elastomers, Semicrystalline Plastics and Blends Crosslinked in situ during Melt Mixing
Authors: Ellul Maria D. 
Published: February 2011

Abstract
Semi-crystalline polyolefins, e.g., polypropylene in its isotactic and syndiotactic forms, become brittle at low temperature due to their inherent crystallinity and relatively high Tg. It has been discovered that certain “non-polar” aliphatic esters, in particular monomeric tallates and sebacates can effect a large depression in Tg of the polypropylene amorphous component which is in line with free volume considerations. The melting point of the crystalline fraction was also depressed albeit to a much smaller extent. This successful plasticization of polypropylene was applied to heterophase systems with the elastomer crosslinked in situ during melt blending with polypropylene and in the presence of a plasticizer. The plasticizer was distributed in both polymer components of the blend. Therefore the glass transition temperatures of both the polypropylene and the elastomer phases could be greatly depressed through simultaneous plasticization of both polymer phases resulting in a supertough material at −40°C and below. Since only the amorphous component of polypropylene is plasticized, the crystalline fraction is not much affected and the upper service temperature range is maintained. The resulting TPEs have an excellent balance of engineering properties to −125°C and are much more elastic than unplasticized TPEs due to the suppression of yielding behavior.
Mathematical Model of Diffusion of Solvents in Rubbers
Authors: Fong C. F. Chan Man , Li Y. , De Kee D. , Bovenkamp J. 
Published: February 2011

Abstract
The chemical potential associated with the diffusion through polymeric systems is assumed to be a function of the concentration and the stress induced by the swelling. The flux for such a model is calculated and is found to be in agreement with the experimental data involving acetone, dichloromethane, and toluene through natural rubber, bromobutyl rubber, and nitrile rubber.
Tire Black Sidewall Surface Discoloration and Non-Staining Technology: A Review
Authors: Waddell Walter H. 
Published: February 2011

Abstract
The tire black sidewall is the outer surface that protects the casing against weathering. It is formulated for resistance to weathering, ozone aging, abrasion, tearing and cracking, and for good fatigue life by using blends of natural rubber and cis-butadiene rubber. Protection against ozone aging is of particular interest since reaction with these olefinically unsaturated elastomers results in polymer decomposition via chain scission. Use of N-alkyl, N′-aryl-para-phenylenediamine antiozonants has proved most effective. However, their use also results in a surface discoloration, and thus they can be used in only limited amounts when tire appearance is also an important factor. A review is made of the literature describing this surface discoloration problem and approaches to formulate a black sidewall compound to eliminate this surface discoloration upon exposure to ozone. Methods include use of non-staining antiozonants, and uses of elastomers with saturated backbones such as ethylene-propylene-diene terpolymers, halobutyl rubbers and brominated-isobutylene- co-para-methylstyrene.
The Calculation of the Tear Energy of Elastomers from Their Viscoelastic Behavior
Authors: Plazek Donald J. , Rosner Mark 
Published: February 2011

Abstract
The creep behavior and the rate dependence of the tear energy have been determined on nine elastomers with widely varying structures. When compared at their glass temperatures the short-time creep compliances, J(t), were located at the same positions on the time scale. Therefore, the terminal zones of response were widely spaced depending on the breadth of the viscoelastic spectra. The positions of the tear energy curves were similarly positioned on the reciprocal rate scale. An equation is proposed for the calculation of tear energy curves from the viscoelastic retardation spectrum.
Protection Mechanisms of p-Phenylenediamine-Type Antiozonants
Authors: Qi Chen-Ze , Wang Tian-Min , Zhang Xian-Man 
Published: February 2011

Abstract
The relative ozonation rate constants for p-phenylenediamines have been estimated from the linear correlation of the ozonation rate constants with the ionization potentials (Figure 1). The efficient antiozonants were found to have relatively lower ionization potentials, but not too low to react with the atmospheric molecular oxygen. The bond dissociation enthalpies (BDEs) of the N—H bonds of p-aminodiphenylamine and related derivatives were found to be about 80 kcal/mol, suggesting that the p-aminodiphenylamines are not only efficient antiozonants, but are also efficient antioxidants. Efficient antiozonants should also be efficient antioxidants to quench the reactive radical intermediates formed during the degradation.
Nitrosamine Formation in Rubber: II. Influence of Cure
Authors: Willoughby Bryan G. , Scott Keith W. 
Published: February 2011

Abstract
Part I of this series identified a key difference in behavior with respect to nitrosamine formation in rubber for EPDM vulcanizates compared with those from SBR, NR or NBR. This paper provides further analysis of some twenty-nine different EPDM cures to investigate both ingredient- and process-related effects. Two different levels of TMTD and carbon black were variables in this study, as was the type of carbon black used (N330 and N550). Batch effects with respect to both polymer and black were also studied, as was the presence or absence of MBT. The use of experimental design has shown how reliable data on nitrosamine formation in vulcanizates can be obtained by paying strict attention to process history, and has revealed for these EPDM cures a correlation between cure time (T90) and the level of nitrosamine formed. Moreover the presence or absence of MBT was also shown to be influential; showing the importance of vulcanization by-products in the generation of nitrosamine. The formation of the thermally unstable dimethyldithiocarbamic acid, and how fast it is produced, are seen as important in a process in which the opportunities for nitrosation are limited by the thermal decay of N2O4.
Carbon—Silica Dual Phase Filler: Part IV. Surface Chemistry
Authors: Murphy Lawrence J. , Khmelnitskaia Elena , Wang Meng-Jiao , Mahmud Khaled 
Published: February 2011

Abstract
A method for estimating the amount of functional groups on the carbon—silica dual phase fillers (CSDPF) available to react with organosilane coupling agents is reported. The method employs trimethylchlorosilane (TMCS) as an analytical probe, and involves equilibrating the samples with TMCS in toluene. The amount of TMCS that reacts with the surface functional groups is obtained by monitoring the concentration of reactants and products of the reaction by Gas Chromatography Mass Spectrometry. The amount of TMCS reacted with the fillers' surface functional groups is compared to the pH, and the active hydrogen content as measured by LiAlH4. Comparison of these measures with the CSDPF, carbon blacks and a fumed silica sample is provided. The dual phase fillers have a heterogeneous surface, containing both carbon and silica phases. Multipoint BET nitrogen surface area is used in combination with iodine number to estimate the individual carbon and silica phase surface areas. From this, the packing density of the trimethylsilyl group attached to the silica phase of the CSDPF surface was estimated and compared to silica. Silanols on these dual phase fillers were detected by infrared spectroscopy. The infrared band for silanols is located at 975 cm−1. The absorbance of this band is shown to correlate with TMCS uptake and diminish after reaction with TMCS, suggesting that silanols indeed are participating in the uptake of TMCS.
Study on Powder Utilization of Waste Tires as a Filler in Rubber Compounding
Authors: Kim Jin Kuk , Burford R. P. 
Published: February 2011

Abstract
The recycling of rubber from waste tires and other products has been of commercial and environmental interest for several decades. For recycling, bulk properties are most relevant; whereas, for crumb incorporation both bulk and matrix-crumb interface phenomena are important, which are dealt with in this study. We have taken a crumb rubber of high surface area and a diameter between 100 and 200 µm and incorporated it into uncured natural rubber (NR) or acrylonitrile—butadiene (NBR) containing silica. This non-black reinforcing filler was used to allow a better modulus match between crumb and matrix than would exist for a non-filled system, while allowing visual contrast between the two phases for microscopic examination. The micromechanics of deformation can be investigated using scanning electron microscopy. The crumb rubber was either added as received or used after a surface chlorination step. The matrix was also used unmodified or with a compatibilizer used to facilitate homogenization of polar and nonpolar elastomers. Differences in matrix/crumb polarity and interfaces were therefore able to be investigated. Chlorination of crumb has a beneficial effect in NBR matrix compounds, but causes embrittlement in NR-based compounds. In the former case, some enhanced compatibility is expected, as analogous poly(vinyl chloride) (PVC)/NBR blends are already used. The compatibilizer also imparts improved performance to the NBR/crumb compound, overcoming differences in polarity between the matrix and the nonpolar crumb. However for the NR matrix compound, similar chemical compositions already exist and so the aliphatic-hydrocarbon resin compatibilizer (STRUKTOL) provides no benefit.
Viscoelastic Characterization of High Fiber Content Filament Wound Polyurethane Matrix Composites
Authors: Orlet M. W. , Bakis C. E. 
Published: February 2011

Abstract
Elastomeric matrix composites (EMCs) consisting of a polyurethane matrix unidirectionally reinforced with high volume fractions of high strength fibers have interesting and unique mechanical properties such as high strength and stiffness in the fiber direction and high ductility perpendicular to the fibers. The aim of this investigation is to explore the quasi-static mechanical properties of glass and carbon fiber EMCs in the direction transverse to the fibers and to measure and model the creep of the monolithic matrix material and the transverse creep of the glass EMC. In the quasi-static tests, glass and carbon EMCs followed a monotonic stress—strain curve that was essentially flat from approximately 1–2% to over 10% strain. The maximum stresses obtained in the quasi-static tests were approximately 3.5 and 7 MPa in the carbon and glass EMCs, respectively. The monolithic matrix and the glass EMC loaded transversely to the fibers both showed highly nonlinear creep behaviors. The former creep behavior was modeled successfully with a standard power law expression. The nonlinear creep behavior of the glass EMC cannot be modeled with a standard power law expression, possibly due to creep damage.
Comparative Studies on the Crosslinking Reaction of Bis-Maleimides and Bis-Citraconimides in Squalene and Natural Rubber
Authors: Datta R. N. , Talma A. G. , Schotman A. H. M. 
Published: February 2011

Abstract
A study has been made to differentiate between the crosslinking reaction of bis-maleimides and bis-citraconimides in squalene as well as in natural rubber. Bis-maleimides are found to participate in the crosslinking reaction in the absence of curatives such as accelerators and sulfur. Bis-citraconimides take part in the crosslinking reaction when polysulfidic crosslinks are under the process of degradation. Sulfur and accelerator are required for the formation of polysulfidic crosslinks and hence the presence of sulfur and accelerator are essential for bis-citraconimide crosslinking. The differences in the reactivity and the chemistry of crosslinking are studied and discussed. Some application data are provided in order to elaborate the differences.
Crystallization of cis- and trans-1,4-Polyisoprene Dispersed in SBR
Authors: Gent A. N. , Kawahara S. 
Published: February 2011

Abstract
Crystallization of natural rubber (NR) and trans-1,4-polyisoprene (TPI) in blends with styrene—butadiene rubber (SBR) has been studied dilatometrically. For TPI, the melting temperature and Avrami index of crystallization kinetics were unchanged by blending with SBR. However, the rate of crystallization was decreased significantly when only 1 wt % of SBR was added, and much more so for amounts large enough to constitute the continuous phase. These reductions in rate are attributed to two effects: chemical changes in TPI during mechanical mixing, and restricted nucleation in small TPI particles. Similar effects were noted for NR blended with SBR. When solution-blended as a 30/70 mixture with SBR, crystallization of the NR fraction was about 9 times slower than for NR itself, and the rate was reduced still further when mixing was more thorough. However, when NR and SBR were mixed mechanically, the rate of crystallization of the NR fraction was not reduced much although the Avrami index and final degree of crystallinity were significantly lower. These effects suggest that the NR particles are strained during mechanical mixing and do not recover afterwards.
Fatigue of Cord—Rubber Composites: III. Minimum Stress Effect
Authors: Ku B. H. , Liu D. S. , Lee B. L. 
Published: February 2011

Abstract
The dependence of fatigue lifetime on the minimum cyclic stress was assessed for the rubber matrix composite of bias aircraft tire carcass reinforced by nylon cords as well as two model rubber composites reinforced by steel wire cables. At a given stress range, the use of higher minimum stress up to a certain level led to longer fatigue life of the composite laminate. When the minimum stress exceeded this critical level, an opposite trend of shorter fatigue life occurred with a higher level of minimum stress. The initial trend of longer fatigue life of angle-plied, cord—rubber composite laminates with a higher level of minimum stress stems from a nonlinear stress—strain relationship with a tendency of strain stiffening. Under stress-controlled fatigue loading, a shorter strain range was experienced for the same stress range when the level of minimum stress was raised. However, the increase of minimum stress raises the potential for damage initiation and accumulation. This effect of increased damage potential became dominant above the critical level of minimum stress. When the fatigue life data were plotted against the values of strain range to clarify the role of damage potential, a general trend of shorter fatigue life with a higher level of minimum stress was observed at a given strain range, in striking contrast to the trend of the stress range vs the number of cycles to failure (S-N) curve in a conventional form. The result again confirms that the damage initiation and eventual fatigue failure of angle-plied, cord—rubber composite laminates are “strain-controlled” processes, as demonstrated in our preceding paper. A modified form of the Goodman equation appears to be valid in predicting the relationship between the strain range (instead of stress amplitude) and minimum strain (instead of mean stress) for a given lifetime of a cord—rubber composite laminate.
Poly(Dimethylsiloxane) Elastomers from Aqueous Emulsions: II. Mechanical Properties
Authors: Mark J. E. , McCarthy D. W. 
Published: February 2011

Abstract
Stress—strain measurements in simple uniaxial extension were used to characterize the mechanical properties of the elastomers prepared from poly(dimethylsilxoxane) emulsions as described in the preceding paper. The studies were carried out on the materials in the unswollen state, after they had received different treatments, specifically no aging, aging in the dry state, or aging in the wet (emulsion) state. Increase in silane crosslinker concentration was found to increase nominal stresses and moduli but to decrease extensibility, two changes that parallel the observed decreases in soluble polymer fractions and extents of equilibrium swelling reported earlier. The energy for rupture (“toughness”) frequently stays roughly constant because the decreased extensibility at least partially offsets the increased stresses. The changes in mechanical properties are due both to increased crosslinking and to reinforcing effects from silica generated from the silane, with the latter effect generally being the more important. The mechanical properties are much more affected by aging in the wet state, as opposed to aging in the dry state. For example, wet-aged elastomers generally had values of the nominal stress and modulus that were consistently lower than those for the unaged elastomers. Wet aging appears to be the result of the continual breaking and reforming of siloxane bonds in the aqueous environment of the emulsion, as probably accelerated by the presence of the tin catalyst.