bluuebunny/crossref_metadata_2025_split huggingface dataset:
GPC Calibration for the Molecular Weight Measurement of Butyl Rubbers
Authors: Puskas Judit E. , Hutchinson Rob 
Published: February 2011

Abstract
Size Exclusion Chromatography (SEC) or Gel Permeation Chromatography [GPC] was used to determine the molecular weight and molecular weight distribution of butyl rubbers. Quantitative data were obtained by viscometry, and by the use of narrow distribution polyisobutylene (PIB) standards for calibration. The application of the Universal Calibration Principle, which uses readily available narrow distribution polystyrene (PS) standards, relies on the knowledge of the Mark-Houwink-Sakurada constants, K and α, for PIB or butyl rubber (the copolymer of isobutylene and isoprene containing 1–3 mol% of the latter). Comparison of narrow PIB and narrow PS calibrations led us to the selection of KPIB=2×10−4 dl/g and α=0.67, the constants published by the American Standards Corporation for PIB in tetrahydrofuran (THF) at 30°C, as best fit values. The weight average molecular weight [Mw] of various samples of commercially produced butyl rubber determined by using the Universal Calibration Principle with the selected constants, agreed well with those measured by viscometry. Other published K and α values yielded a poorer agreement.
A Constraint Dynamics Approach to Rubber Elasticity
Authors: Ngai K. L. , Roland C. M. , Yee A. F. 
Published: February 2011

Abstract
The coupling model of relaxation is applied to crosslinked rubber, with a connection drawn between the dynamics of network junctions and statistical mechanics derived rubber elasticity theory. The suggestion that unifying concepts must underlie dynamical models and thermodynamic theories is shown to be supported by analyses of recent 31P NMR spectroscopy measurements by Shi, Dickinson, MacKnight and Chien on polytetrahydrofuran networks and of our mechanical relaxation data on stretched and unstretched polycarbonate.
An Analysis of the “Durometer” Indentation
Authors: Briscoe Brian J. , Sebastian K. Savio 
Published: February 2011

Abstract
The mechanics of the indentation of elastomers by the “Durometer” (Shore A) hardness tester is analysed using the theory of elasticity to derive an interrelation between the Shore hardness number and the Young's modulus. Experimental compliance curves, for different elastomers, are provided to support the theory. The theoretical interrelationships between the International Rubber Hardness and the Shore A Hardness and the corresponding elastic modulus are also compared. The effects of the time dependent deformations are examined. Finally, the error introduced by computing the Young's modulus using an equivalent punch solution is examined and a means of improving the predictions is provided.
Ultrasound Devulcanization of Sulfur Vulcanized SBR: Crosslink Density and Molecular Mobility
Authors: Levin V. Yu , Kim S. H. , Isayev A. I. , Massey J. , von Meerwall E. 
Published: February 2011

Abstract
Sulfur-cured SBR vulcanizates are devulcanized by high power ultrasonic irradiation in a continuous process under various processing conditions. Crosslink density and gel fraction of devulcanized rubber are measured. The unique dependence of crosslink density on gel fraction of devulcanized samples obtained at various processing conditions is established. DSC studies indicate a significant increase in the glass transition temperature of the devulcanized rubber having crosslink density lower than that of the original vulcanizates. Solid state NMR studies confirm that these changes in Tg are due to a decrease of molecular mobility as measured by a decrease in spin-spin relaxation time. Ultrasonic devulcanization is accompanied by a significant increase in xcis-trans isomerization. Chemical changes explaining the observed phenomena are discussed.
Mechanism by Which Precipitated Silica Improves Brass-Coated Wire-To-Natural Rubber Adhesion
Authors: Waddell Walter H. , Evans Larry R. , Goralski Edward G. , Snodgrass Linda J. 
Published: February 2011

Abstract
Quantitative determination of elements in the interfacial growth layer formed on brass-coated wire when reacted in squalene suspensions containing carbon black and curatives, with and without precipitated silica and an organocobalt adhesive, was accomplished by using direct surface characterization techniques: Scanning Electron Microscopy with Energy Dispersive Analysis of X-rays (SEM-EDX), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and Proton Induced X-ray Emission (PIXE) Spectroscopy. The effects on elemental changes in the interfacial growth layer upon addition of silica and/or cobalt neodecanoate to the squalene suspensions were statistically analyzed. Since the mechanism for silica improvement of brass-coated wire-to-rubber adhesion was previously shown not to be a simple effect of improving rubber physical properties, a chemical mechanism is proposed involving silica to reduce the thickness of the interfacial growth layer and to change the relative concentration of compounds formed in the interfacial growth layer.
A Study of the Vulcanization Kinetics of an Accelerated-Sulfur SBR Compound
Authors: Ding R. , Leonov A. I. , Coran A. Y. 
Published: February 2011

Abstract
Vulcanization kinetics for a SBR compound was studied by using both curemeter and DSC methods by a kinetic approach. A simplified but realistic model reaction scheme was used to simulate both induction and curing periods simultaneously. Model parameters were extracted from isothermal curemeter experiments. The model prediction demonstrated a good agreement with isothermal curemeter data over a temperature range of 120°C to 180°C. The variation of equilibrium modulus with temperature, observed from cure curves, can also be predicted. However, DSC experiments showed a different reaction behavior in the curing period as compared to model calculations. This was explained by the assumption that the reaction heat observed in DSC is due to all possible exothermal reactions, and the formation of crosslinks is only a part of these reactions. Hence, the curemeter can provide a good indication of crosslink formation, while DSC displays the entire reaction heat released during the vulcanization process. The kinetic approach allows one to incorporate vulcanization kinetics into the practical simulation of reactive processing operations.
A Simple Methodology for the Modeling of Carbon Black Aggregate Structure
Authors: Li Qi , Manas-Zloczower Ica , Feke Donald L. 
Published: February 2011

Abstract
A procedure for modeling some morphological characteristics of carbon black aggregates is presented. The method uses a standard reaction limited aggregation algorithm to predict the location of the centers of primary particles within an aggregate. The shape of the aggregate is determined by drawing simple linear links between extreme points of primary particles centered on these loci. Analysis of the particle distribution function computed from the simulated structure leads to definitions of the interior and periphery of the aggregate structure. Direct comparisons between simulated aggregates and two commercial carbon blacks are presented to illustrate the usefulness of the approach. The perimeter fractal dimension of simulated aggregates can be made to match the perimeter fractal dimension of the commercial carbon black aggregates through proper choice of the sticking probability in the simulation algorithm. With this proper choice of sticking probability, the relative amounts of voids in the periphery and interior of the simulated aggregate correspond to relative amounts of filled and unfilled voids in actual aggregates that have been soaked for extended periods of time with processing fluids.
Devulcanization of Waste Tire Rubber by Powerful Ultrasound
Authors: Tukachinsky A. , Schworm D. , Isayev A. I. 
Published: February 2011

Abstract
Ground rubber tire (GRT) is devulcanized in a continuous process where the rubber crumb is conveyed by a screw extruder to a thin gap between a stationary die and a vibrating horn. Ultrasound amplitude, gap thickness and the duration of the treatment are varied, and their effect on the rubber properties is studied. The degree of devulcanization is characterized by the crosslink density and gel fraction of the devulcanized rubber. These characteristics are found to correlate uniquely with each other over a wide range of the treatment conditions. The specific energy of ultrasound consumed per unit mass of the rubber is found to be the operating parameter correlating with the properties of the devulcanized rubber. The mechanical properties of the re-vulcanized samples reach a maximum with an increasing degree of devulcanization, and then drop as a result of excessive degradation. Even without optimization of cure recipes, tensile strength and ultimate elongation of re-vulcanized tire rubber as high as 10.5 MPa and 250%, respectively, are achieved.
Novel Sulfur Vulcanization Accelerators Based on Mercapto-Pyridine, -Pyrazine, and -Pyrimidine
Authors: Rostek Charles J. , Lin Horng-Jau , Sikora David J. , Katritzky Alan R. , Kuzmierkiewicz Wojciech , Shobana Navayath 
Published: February 2011

Abstract
Sulfur vulcanization accelerators derived from 2-mercaptobenzothiazole (MBT) have been a staple for the rubber processing industry for over 65 years. Most noteworthy are the sulfenamide derivatives, which provide various combinations of scorch delay and cure rate, depending upon the basicity and steric nature of the sulfenamide N-substituent(s). While the effect of the amine moiety on benzothiazole sulfenamide accelerator performance has been well documented, the effect of the S-linked heterocyclic moiety of the sulfenamide has been investigated to a much lesser extent. Thus, to gain a better understanding of the role of the heterocycle, a variety of novel disulfides and sulfenamides based on pyridine have been synthesized and tested. The performance of the pyridine based accelerators have been compared to each other and to the various benzothiazole analogues. Until recently, the corresponding sulfenimides (compounds containing two divalent thiol moieties attached to an amine nitrogen ) seem to have received little attention in the rubber industry. Sulfenimides based on pyridine, pyrazine and pyrimidine have therefore also been synthesized and tested. The differences in preparation and vulcanization activity for the benzothiazole sulfenimides and sulfenamides are described, as well as some rudimentary differences which have appeared in the early stages of mechanistic work. It has been discovered in the course of this work that other heterocyclic thiols may be substituted for 2-mercaptobenzothiazole in the basic sulfenimide structure to gain advantages both in faster cure rate and extended scorch delay. The behavior of these novel sulfenimides in common rubber cure systems is presented together with representative physical properties of the rubber vulcanizates.
Effect of Porosity on Dynamic Mechanical Properties of Rubber in Compression
Authors: Kasner Alan I. , Meinecke Eberhard A. 
Published: February 2011

Abstract
Cylindrical samples of different levels of porosity were prepared from a model carbon black filled rubber and tested in compression. Dynamic properties were determined with dynamic loads and dynamic displacements superimposed on static loads. Nonlinear stress-strain curves of porous rubber blocks produced a dependence of dynamic properties on the mode of testing. Both storage and loss moduli as well as tan γ were found to depend on the levels of porosity. The loss modulus was found to increase with higher strain levels in porous samples, while the storage modulus changed because of reduced sample stiffness. The dynamic data was in agreement with the results of Goodrich flexometer tests on porous and solid samples. The results suggest that the introduction of porosity reduces service life of rubber parts by providing stress raisers for crack initiation, rather than through changing the dynamic properties.
Reinforcement Mechanisms in Carbon Black and Silica Loaded Rubber Melts at Low Stresses
Authors: Eggers H. , Schummer P. 
Published: February 2011

Abstract
For a range of different fillers, silicas and carbon blacks, added to a rubber melt at various concentrations, dynamic moduli in the linear viscoelastic limit have been determined. It is shown that reinforcement is due to hydrodynamic effects and the formation of a secondary particulate structure within the rubber matrix. Both mechanisms can be distinguished experimentally by a frequency sweep. Hydrodynamic reinforcement depends on the filler volume to which immobilized polymer must be added. Its concentration dependence is well described by the semiempirical exponential Thomas Equation. Nominal and effective filler loadings are related by concentration-independent effectiveness factors which can be modelled for all types of fillers considering an immobilized layer of constant height around an agglomerated cluster of filler particles. This provides an explanation for the well-known dependence of reinforcement ability on surface area at small stresses. The chemical and microscopic structure of the filler surface appears to be less important with respect to immobilization ability in the linear viscoelasic regime. The secondary structure formed by the particles is found to be tied together by the elastomer. Its modulus correlates with the filler's immobilization ability and shows little dependence on the filler nature. Due to formation of a filler-polymer structure with individual relaxation times, a strict separability of hydrodynamic and interparticular-reinforcement mechanisms at very high loadings no longer applies.
The Rolling Resistance, Wear and Traction Properties of Tread Compounds
Authors: Grosch K. A. 
Published: February 2011

Abstract
The paper gives a brief survey of the state of friction and abrasion research with a view of the possibility to use laboratory methods for the development of new compounds with optimal traction and abrasion properties. It shows that viscoelasticity plays a decisive role in friction and in this way measurements of the dynamic properties give a good indication of the possibilities for good traction properties. However, friction is still a good deal more complex than the modulus or loss factor curves. It takes in different frequency ranges and temperatures in the contact area so that a direct laboratory measurement of these properties is still very desirable. If the speed and temperature correspond to the log aTv values experienced in practice and the laboratory track structure and texture is not too far removed from that of road surfaces, the correlation with road tests is high. To simulate the structure and texture of road surfaces with durable laboratory surfaces, a combination of two surfaces may be necessary. Abrasion is not only influenced by the strength properties of the rubber but also by oxidation and thermal degradation. To give these processes the correct weight in the laboratory, the testing conditions have to be mild and a combination of several conditions is necessary in order to demonstrate the complexity of interactions, which can lead to ranking reversals. Energy dissipation, speed, and abrasive surface structure and texture are identified as prime variables to achieve a high correlation with road wear. Since viscoelasticity, encompassing not only polymer but also filler, oil-extension, curing and other compound additives, plays a major role in both friction and wear, the rolling resistance of the compound is always effected and has to be taken into account. Modern polymerization methods and new filler concepts make it possible to change the viscoelastic properties in such detail that high friction and—to the degree to which strength contributes to wear—high wear resistance can be combined with low rolling resistance. This development has certainly not reached its climax yet. Exciting times lie ahead for tire compounders, polymer- and filler chemists alike.
Intrinsic Defects and the Failure Properties of cis-1,4-Polyisoprenes
Authors: Choi I. S. , Roland C. M. 
Published: February 2011

Abstract
Inherent flaw sizes were determined from fatigue lifetimes, and from the crack length dependence of the strain energy to break, for four cis-1,4-polyisoprenes compounded to have the same crosslink density and low strain hysteresis. Both techniques indicated that the flaws intrinsic to guayule rubber (GR), and to a lesser extent conventional natural rubber, are larger than those found in deproteinized NR. This result may not be surprising; however, the failure properties of the elastomers, expected to depend on flaw size, were surprising. The guayule rubber and a natural rubber of relatively low purity (SMR-10) had the highest tensile strengths, tear strengths, breaking energies, and fatigue lifetimes, while DPNR exhibited the worst failure properties. Such an inverse correlation between flaw size and failure performance is due to the dominant effect of strain-induced crystallization. GR and SMR-10 have the highest propensity for strain-induced crystallization, while DPNR is the least strain-crystallizable. Interestingly, all rubbers exhibited the same isotropic crystallization behavior.
Origin of Characteristic Properties of Natural Rubber—Synergistic Effect of Fatty Acids on Crystallization of cis-1,4-Polyisoprene: II, Mixed and Esterified Fatty Acids in Natural Rubber
Authors: Nishiyama Naoyuki , Kawahara Seiichi , Kakubo Takashi , Hwee Eng Aik , Tanaka Yasuyuki 
Published: February 2011

Abstract
Crystallization behavior of deproteinized natural rubber at −25°C was investigated by dilatometry in connection with the effect of long-chain fatty acid groups, esterified to the rubber chain, as well as free fatty acids and their esters. The overall crystallization rate decreased after removal of the acetone-extractable free fatty acids and their esters, while it increased significantly when the fatty acid groups esterified to natural rubber molecule were removed by transesterification with sodium methoxide. Both the acetone-extracted and transesterified rubbers showed a significant increase in the overall crystallization rate after the addition of 1 wt % stearic acid. The crystallization of acetone-extracted rubber was accelerated by the addition of 1 wt % methyl linoleate, a plasticizer of natural rubber, whereas it was suppressed in the case of transesterified rubber in which the esterified fatty acid groups were removed completely. The fatty acid groups esterified to natural rubber molecule gave rise to the accelerated crystallization of the rubber in conjunction with free fatty acids and their esters.
Rheological Behavior of Highly Filled EPDM Compounds with Calcium Carbonate, Carbon Black, Silica and Zinc Oxide
Authors: Li Li Li , White James L. 
Published: February 2011

Abstract
The shear viscosity, creep and constant shear rate transients have been measured for 0.20 volume fraction compounds of an EPDM with calcium carbonate, carbon black, silica and zinc oxide of similar particle size at 100°C. Measurements have been made in a creep sandwich instrument, pressurized rotational rheometer and a capillary rheometer and cover nine decades of shear rate. All of the compounds exhibit enhanced viscosities and yield values; i.e. there are stresses below which there is no flow. The greatest yield values and increased viscosities are with the compounds with calcium carbonate and zinc oxide. More extensive studies were made with the EPDM-calcium carbonate system, where it was shown that, increasing particle size reduces shear viscosity and yield values. Further, surface treating calcium carbonate with stearic acid signifcantly reduces the shear viscosity and yield value of the corresponding EPDM compound.
Analysis of Ice- and Snow Traction of Tread Material
Authors: Futamura Shingo 
Published: February 2011

Abstract
The critical property of tire tread material for ice-skid resistance was analyzed. This skid resistance in the temperature range of 0 to −15°C is related to the compliance, not the hysteresis, of the tread material. Mechanistic analysis of the phenomena is presented in terms of the viscous resistance of a thin liquid-like layer on the surface of ice. The microscopic contact area and the wiping action of the tread material seem to be important factors for ice skid resistance. In a winter tire, the critical tread material property for traction on packed snow follows the same relationship.
Simulation of Flow in an Intermeshing Internal Mixer and Comparison of Rotor Designs
Authors: Kim Pan Soo , White James L. 
Published: February 2011

Abstract
This paper describes a simulation of flow in various intermeshing rotor internal mixer designs. The rotor designs studied were obtained from the patent literature and presentations of the major intermeshing rotor machinery mixer manufactures. The results of the simulation are compared to those for rotors of commercial separated rotor mixers. We seek to compare intermeshing and separated rotor mixers by contrasting estimated rates of mixing per unit total mixing chamber volume. Intermeshing rotors are generally predicted to perform better. This indicates they will mix more material despite smaller available internal mixer volume.
High Frequency Viscoelasticity of Carbon Black Filled Compounds
Authors: Gerspacher M. , O'Farrell C. P. , Nikiel L. , Yang H. H. , Le Méhauté F. 
Published: February 2011

Abstract
A high frequency viscoelasticity spectrometer, using the state-of-the-art ultrasonic technology, was constructed. The longitudinal and shear waves characteristics were measured in rubber compounds to obtain the attenuation coefficient, α, and sound velocity, v Preliminary results were obtained for a number of filled and unfilled polymers. The grade of carbon black used, filler loading, crosslinking density and filler dispersion were varied during the study. Temperature sweepS from −100°C to +60°C were also studied. It was found that the polymer type had a greater influence on α and v than did the grade of carbon black, loading or dispersion. The experimental data show that shear waves do not propagate in the rubbery state. Above the glass transition temperature, Tg, the longitudinal wave measurements could be sufficient to determine the high frequency dynamic properties of filled and unfilled polymers to characterize a tire tread compound. The temperature sweep measurements allowed the determination of the Tg of polymers at high frequency. It is proposed that the described method of measuring α and v be used as a laboratory tool for potential tire traction prediction.
Cut Growth in Vulcanizates of Natural Rubber, cis-Polybutadiene, and a 50/50 Blend during Single and Repeated Extension
Authors: Hamed G. R. , Kim H. J. , Gent A. N. 
Published: February 2011

Abstract
A typical passenger sidewall composition was employed using three elastomer systems NR, BR, and a 50/50 blend of NR and BR. Tensile strips with edge cuts of various depths were strained in two ways continuously increasing extension up to rupture, or repeatedly stretching them to progressively higher strains until failure occurred. For BR, the tensile strength σb decreased steadily with increasing cut depth, c, while NR and NR/BR showed an abrupt decrease in σb at a critical cut size, ccr. This is attributed to crystallization of NR throughout the specimen at high strains, when c&lt;ccr, while crystallization is confined to the crack tip region when c&gt;ccr. Furthermore, in samples of NR and NR/ BR the crack tip split, forming two secondary cracks which grew a considerable distance parallel to the direction of straining, and even turned backwards, before stopping. Rupture of the specimen did not occur until a new (third) crack was initiated from the smooth torn surface of the secondary crack. Under repeated straining NR specimens developed secondary cracks repeatedly in a characteristic alternating pattern. These are instances of severe “knotty” tearing. In contrast, in BR samples the initial cut always grew in a forward direction and secondary, longitudinal cracks did not develop.