bluuebunny/crossref_metadata_2025 huggingface dataset:
An Appropriate Model Compound for the Accelerated Sulfur Vulcanization of Polyisoprene: I. The Mechanism of Bisbenzothiazole-2,2′-Disulfide Accelerated Vulcanization of Squalene in the Absence of ZnO
Authors: Boretti L. G. , Woolard C. D.
Published: February 2011

Model compound vulcanization is a useful technique for studying the mechanism of accelerated sulfur vulcanization. A technique based on gel permeation chromatography is presented which allows for the use of squalene as model compound. Squalene is shown to be a more realistic model compound for polyisoprene vulcanization in that the release of 2-mercaptobenzothiazole accompanies the formation of crosslinks. This situation accurately mirrors the situation in polyisoprene, unlike simpler model compounds such as 2-methyl-2-pentene. It is likely that a realistic model compound requires the presence of at least 2 isoprene units to allow for reactions at adjacent methylenic carbons. A mechanism for bisbenzothiazole-2,2′-disulfide vulcanization is proposed where the reaction of bisbenzothiazole-2,2′-polysulfides with squalene occurs in a concerted fashion to produce pendent groups and no 2-mercaptobenzothiazole. These pendent groups then react slowly with methylenic hydrogens on squalene to produce initial crosslinks and 2-mercaptobenzothiazole. The latter then reacts, in the presence of sulfur, with squalene to produce polysulfidic thiols which in turn react rapidly with benzothiazole groups to form further crosslinks and more 2-mercaptobenzothiazole. The whole process is autocatalytic.
Chemistry of Various Accelerators in an E-SBR Model Compound
Authors: Pierre C. C. , Datta S. , Datta R. N. , Talma A. G.
Published: February 2011

Sulfur vulcanization was carried out with 5-phenyl hex-2-ene serving as a model of e-SBR. Various accelerators have been used to study and compare the reactivity in a system containing sulfur and activators. Both HPLC and GC-MS analytical tools were used to identify the reaction products. It has been observed that the vulcanization in the presence of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) generates a large amount of 2-marcaptobenzothiazole (MBT), which continuously increases and finally decreases suggesting further participation in vulcanization generating new crosslinks. The sulfenamide, N-cyclohexyl-4,6 dimethyl-2-pyrimidine sulfenamide (CDMPS) behaves different. Although it generates considerable amount of corresponding thiol, (4,6-dimethyl pyrimidine-2-thiol, DMMP) at the beginning of the reaction, no decrease has been observed during the course of further reaction suggesting that the accelerator, DMMP, somehow remains deactivated and therefore no changes in network is feasible. Identical differences exist between bis(2,2′benzothiazyl) disulfide (MBTS) and corresponding bis (4-methyl-2,2′benzothiazyl)disulfide (M-MBTS) in the reaction kinetics.
Influence of Nanosilica Particles on Hysteresis and Strain Induced Crystallization of Natural Rubber as Investigated by a Real Time True Stress-True Strain Birefringence System
Authors: Fiorentini F. , Cakmak M. , Mowdood S. K.
Published: February 2011

In this paper, the influence of nanosilica particles on hysteresis and stress induced crystallization of natural rubber compounds is described. For this purpose a newly developed uniaxial stretching system that monitors birefringence, true stress and true strain was used in real time while stretching and retraction is applied to the nanocomposite sheets. This allowed us to link the continuous structural measurements - as represented by birefringence - and the true mechanical properties during the actual stretching and retraction stages as influenced by the presence of nanosilica particles. The birefringence measurement system was also shown to be quite robust in detecting very low levels of retardation prevalent in rubbers. The stress optical behavior of unfilled NR compounds was compared with those filled with 5 phr and 10 phr nanosilica particles. This study allowed the determination of a critical birefringence value above which strain - induced crystallization occurs in the NR compounds. The results indicate that the addition of nanosilica reduces the stress optical constant of natural rubber compounds. In addition, the critical birefringence, above which the strain - induced crystallization occurs, decreases in the presence of 5 phr nanosilica thus indicating the enhancement of the crystallization process at this loading. However, the nanosilica loading beyond 5phr was not found to be a further benefit to strain - induced crystallization mostly because of the introduction of large surface area nanosilica agglomerates that act as a physical barrier between the chains that also most likely suppresses the crosslinking reaction during the preparation.
The Theory of the Rubber Elasticity of Ideal Networks With Entanglements; Application of the Theory to the Calculation of Stresses in Real Networks
Authors: Scherbakov Yu M. , Grishin B. S.
Published: February 2011

Based on the model of a freely hinged chain, the theoretical analysis of the configuration statistics of the ensemble of two freely hinged chains with entanglements is carried out. It is found that the laws of the chain ensemble deforming (at the micro level) and the deforming of the continuum element (at the macro level) can be described by similar relationships. The variation of constraints due to entanglements for the chain ensemble and the element surface area due to deformations λ1 and λ2 is similar. Based on that law, a method to describe constraints caused by entanglements for the chain ensemble is proposed. The theoretical derivation of an equation for the free energy of networks with entanglements in the absence of physical crosslinks is rendered, the obtained equation coincides with the empirical potential of Mooney-Rivlin in its form. The description of stresses in real networks with consideration for constraints due to entanglements and physical crosslinks is suggested. For the description of constraints due to physical crosslinks, the Flory-Erman theory of constrained junctions (CJ) is employed. A real network description is provided by modifying the CJ theory based on the results of the theoretical analysis of ideal networks with entanglements (the MCJ theory). The verification of the stress [f] dependence description was carried out proceeding from the reciprocal of the extension ratio λ−1 using the experimental data of H. Pak and P. J. Flory by simple extension-compression of polydimethylsiloxane (PDMS) networks with a different density of chemical crosslinks. The adequacy of the MCJ theory equation system for the calculation of the polymer stress-strain states is demonstrated.
Stiffness of Annular Bonded Rubber Flanged Bushes
Authors: Horton J. M. , Tupholme G. E.
Published: February 2011

Closed-form expressions are derived for the torsional stiffness, radial stiffness and tilting stiffness of annular rubber flanged bushes of finite length in three principal modes of deformation, based upon the classical theory of elasticity. Illustrative numerical results are deduced with realistic physical data of typical flanged bushes.
Numerical Simulation of Thermal Oxidation in Automotive Tires
Authors: Ellwood Kevin R. J. , Baldwin John , Bauer David R.
Published: February 2011

A finite element kinetic model has been developed to interpret issues related to accelerated aging of tires. The model is based on the Basic Autoxidation Scheme and incorporates mass transport limitations related to diffusion of oxygen into the layered elastomer system. The extent of oxidation is calculated at different locations within the tire as a function of time and temperature. Results for aging rates due to thermal oxidation predicted by the model are compared to experimentally derived data such as crosslink density, elongation-to-break and modulus variation. Comparative results for aging rates in different regions of the tire suggest that a reasonable accelerated oven testing temperature range is 60 °C to 70 °C. Additionally, initial results for predicted aging rates for a rolling tire are presenting indicating the thermal oxidation plays a large role in tire aging.
Recovery of Shear-Modified Polybutadiene Solutions
Authors: Roland C. M. , Robertson C. G.
Published: February 2011

We have investigated the recovery of the overshoot in the transient viscosity, the first normal stress coefficient, and the dynamic modulus for entangled polybutadiene solutions subjected to nonlinear shear flow. The molecular-weight dependences of the various time scales (linear viscoelastic relaxation time, entanglement recovery time, and timescale for decay of stress following cessation of shearing) are all consistent with the usual 3.4 power law. Nevertheless, the time for recovery of the stress overshoot and plateau value of the dynamic modulus were substantially longer (by as much as two orders of magnitude) than the linear viscoelastic relaxation time calculated from the Newtonian viscosity and the equilibrium recoverable compliance. These results indicate that complete entanglement recovery requires cooperative chain motions over a length scale exceeding that associated with linear relaxation. This persistence of a disentangled state means that a state of low viscosity and reduced elasticity is retained for an extended time, suggesting that shear modification can be used to facilitate the processing of polymers.
Viscoelastic Indentation and Resistance to Motion of Conveyor Belts Using a Generalized Maxwell Model of the Backing Material
Authors: Rudolphi Thomas J. , Reicks Allen V.
Published: February 2011

A one-dimensional Winkler foundation and a generalized viscoelastic Maxwell solid model of the belt backing material are used to determine the resistance to motion of a conveyor belt over idlers. The viscoelastic material model is a generalization of the three-parameter Maxwell model that has previously been used to predict the effective frictional coefficient of the rolling motion. Frequency, or loading rate, and temperature dependence of the material properties are incorporated with the time/temperature correspondence principle of linear viscoelastic materials. As a consequence of the Winkler foundation model, a normalized indentation resistance is independent of the primary belt system parameters - carrying weight per unit width, idler diameter and backing thickness - as is the case for a three-parameter viscoelastic model. Example results are provided for a typical rubber compound backing material and belt system parameters.
Some Geometric Considerations for Rubber—Metal Bond Test Specimens
Authors: Yeoh O. H.
Published: February 2011

Most methods for predicting fatigue lives of rubber components rely heavily on experimental studies that involve specimens subjected to essentially uniform states of deformation. But, in service, rubber components often fail at or near rubber-metal bonds where the state of deformation is far from uniform. Before experimental studies of fatigue failure in the vicinity of rubber-metal bonds, it is prudent to perform an analysis of the specimen geometry to make sure it has been optimized. This paper reports on finite element analyses of cylindrical rubber-metal bond test specimens recommended in ASTM D 429. The results suggest that taller specimens (height/radius ratio ≥ 2) have some advantages. Interpretation in terms of the strain energy release rate is recommended. A new asymmetric test specimen is proposed.
Structural Characterization of Terminal Groups in Natural Rubber: Origin of Nitrogenous Groups
Authors: Mekkriengkrai Dararat , Sakdapipanich Jitladda T. , Tanaka Yasuyuki
Published: February 2011

The nitrogenous groups in natural rubber (NR) from Hevea brasiliensis have been regarded as an important factor governing cured rubber properties, although there is no structural evidence. The nitrogenous compounds in highly purified NR were characterized to disclose the origin of nitrogenous groups. The rubber particles in fresh latex were purified by washing, i.e., successive dilution of the cream fraction and concentration by centrifugation in the presence of surfactant. The nitrogen content of natural rubber from the washed rubber particles decreased from 0.281% to 0.015% level after washing 3–5 times, the level of which was similar to that of deproteinized natural rubber with a proteolytic enzyme. The presence of 1–2 nitrogen atoms per rubber chain was presumed based on the nitrogen content and Mn value. The nitrogen content of fractionated rubber fractions from rubber particles washed 5 times increased with increasing molecular weight. The nitrogenous group in the rubber chain is postulated to originate from mostly phospholipids associating with branch-points and from functional groups formed by oxidation and successive reactions in latex.
A Two-Part Tale: The WLF Equation and Beyond Linear Viscoelasticity
Authors: Landel Robert F.
Published: February 2011

In this description of my work, I will first share some behind-the-scenes events in the discovery of the WLF. Then, I'll indicate why and how going to the Caltech/Jet Propulsion Laboratory led to our investigations of, and some results for, both large deformation uniaxial and biaxial responses in rubbers.
Synchrotron X-Ray Studies of Vulcanized Rubbers and Thermoplastic Elastomers
Authors: Toki Shigeyuki , Hsiao Benjamin S. , Kohjiya Shinzo , Tosaka Masatoshi , Tsou Andy H. , Datta Sudhin
Published: February 2011

Synchrotron X-ray diffraction technique has revealed strain-induced crystallization and molecular orientation in vulcanized rubbers and thermoplastic elastomers (TPE) during deformation in real time. The stress-strain curves and wide angle X-ray diffraction (WAXD) patterns in vulcanized rubbers and TPE were measured simultaneously. In-situ WAXD patterns were taken not only at different strains during uniaxial deformation but also at different temperatures at a constant strain. Results lead to several new insights. (i) Strain-induced crystallization is a common phenomenon in vulcanized rubbers, except SBR (styrene-butadiene rubber), and in TPE (with crystalline hard segments). (ii) Strain-induced crystallization decreases the stress and increases the elongation in the strained rubber. (iii) The hybrid structure of chemical networks and strain-induced crystallites is responsible to the tensile strength and elongation at break for both systems. (iiii) Some original crystal fraction (hard segment domain) in TPE is destroyed. During deformation, strain-induced crystallization increases with strain. Upon retraction even to stress zero, the majority of oriented strain-induced crystallites remains in tack with preferred orientation.
Review and the Latest Update of N-Nitrosamines in the Rubber Industry; the Regulated, the Potentially Regulated, and Compounding to Eliminate Nitrosamine Formation
Authors: Goss L. C. , Monthey S. , Issel H-M.
Published: February 2011

For several years, Germany has led the effort to eliminate the use of common nitrosamines in the rubber industry. Their TRGS 522(Nov 95) allows no more than 2.5 µg/m3 emission of nitrosamines between vulcanization and warehousing. Additionally, major U.S. Automobile manufacturers have issued stringent requirements with regards to the use of nitrosamines. One company has issued a restricted substances standard that prohibits the use of nitrosamines in excess of the 0.1 % threshold value of the part's total weight. With over 300 nitrosamines listed as either known or suspected carcinogens, safety continues to drive the elimination of nitrosamines in the rubber industry. Therefore, this is a review of nitrosamine regulations, identification of nitrosamines, how they are formed, and the latest in compounding essentials to produce non-nitrosamine generating compound.
Analysis of Fatigue Life under Complex Loading: Revisiting Cadwell, Merrill, Sloman, and Yost
Authors: Mars W. V. , Fatemi A.
Published: February 2011

An early study by Cadwell, Merrill, Sloman, and Yost reports fatigue lives under several combinations of static axial load and cyclic simple shear. The results have practical importance because similar loading situations commonly arise in many rubber components. This paper presents an analysis of these experiments. The objective of the analysis is to compare two approaches for rationalizing the reported fatigue lives. The first approach is based on a scalar parameterization of the loading history (strain energy density). The second approach is based on a parameterization of the loading history that is specific to particular material planes (cracking energy density). The analyses illustrate that a plane-specific approach provides a more successful framework for addressing several commonly encountered features of complex loading histories: multiaxiality of loading, non-relaxing loading cycles (R ratio effects), and crack closure during part of a loading cycle.
Carbon Black Distribution in the Components of Rubber Blends Monitored by Online Measured Electrical Conductance
Authors: Le H. H. , Qamer Z. , Ilisch S. , Radusch H-J.
Published: February 2011

The kinetics of carbon black (CB) dispersion in SBR/NR and EPDM/NR blends has been investigated using the electrical conductance measured online in the internal mixer. It is interesting to note that the infiltration and dispersion processes take place sequentially in the blend phases, which can be well characterized by analyzing the online conductance-time characteristics. A method for the estimation of the phase specific CB distribution in the blend was proposed by taking into consideration the online conductance values measured at the black incorporation time (BIT) of the blend components.
Small Indentations of Rubber Blocks: Effect of Size and Shape of Block and of Lateral Compression
Authors: Gent A. N. , Yeoh O. H.
Published: February 2011

Many gaskets and seals consist of a long rubber strip or thin-walled ring, placed on a flat rigid surface and indented by a flat-ended rigid indenter. We have examined their resistance to small indentations by FEA. They are treated as infinitely-long elastic blocks of rectangular cross-section, resting on a rigid frictionless base. The indentation stiffness is calculated for various ratios of indenter tip width to block width and to block thickness, using two restraint conditions on the outer surfaces: frictionless walls (zero outwards displacement), as for a gasket placed in a recess; or stress-free, as for a gasket with no lateral restraint. For an infinitely-wide and infinitely-thick block, the theoretical resistance to indentation is zero. For comparison, the indentation stiffness is calculated for cylindrical rubber blocks of varied radius and thickness, indented by a flat-ended cylindrical indenter. In this case the result for an infinitely-large block is finite. A second study treats indentation of a rubber block, pre-compressed in the surface plane. Biot showed that the indentation stiffness of a half-space becomes zero at a critical compression, about 33% for equi-biaxial compression and 44 % for plane strain compression, for both a neo-Hookean and a Mooney-Rivlin elastic solid. FEA calculations were made of the indentation stiffness of neo-Hookean blocks of various sizes, pre-compressed to various degrees. The results are compared with Biot's result. In an Appendix, the critical degree of compression is calculated for a more realistic strain energy function than either the neo-Hookean or the Mooney-Rivlin approximation.
Experimental Determination of Fatigue Crack Growth Behavior and Surface Strain Distribution of ‘Faint-Waist Pure Shear’ Specimens with Different Crack Tip Radii
Authors: Feichter Christian , Major Zoltan , Lang Reinhold W.
Published: February 2011

The influence of the initial crack-tip radius on the fatigue behavior and the strain distribution in the vicinity of the blunted crack tip was determined experimentally using a servo-hydraulic testing machine and an optical full-field strain analysis method. Two different elastomer grades (SBR, EPDM) were selected for the experimental work. The strain analysis method used, based on the image correlation technique, was found to be an effective tool to determine strains, strain distributions and gradients near the crack tip for elastomeric materials. Different material behavior was observed in the two rubber types investigated. While the crack tip was regularly blunted (half circle shape) for EPDM and the strain gradient was low (less steep), the crack tip was sharp (less blunted) with a higher strain gradient for SBR. Furthermore the crack tip radius was found to be an important influencing factor on the initiation of crack growth, but not on the crack growth behavior after initiation. Based on the experimental results a phenomenological, first-order, crack-growth initiation law was proposed, dependent on the crack tip radius, the tearing energy at crack growth initiation for a sharp crack and a parameter representing the influence of the crack tip radius.
Thermal Characterization of the Interaction of Silanes with a Dihydroxy Vulcanized Fluoroelastomer
Authors: Sands Michael Benjamin , Subramanian Vijay , Mao Guangzhao
Published: February 2011

The reactivity of aminosilane and vinylsilane with a dihydroxy (Bisphenol AF) crosslinkable fluoroelastomer containing only vinylidene fluoride (VF2) and hexafluoropropylene (HFP) was monitored using Differential Scanning Calorimetry (DSC) and X-ray Photoelectron Spectroscopy (XPS). The DSC results showed that the introduction of an aminosilane, or a combination of aminosilane and vinylsilane solutions, to the cure system of the fluoroelastomer resulted in a peak shift. This shift indicates that crosslinking in fluoroelastomer-silane system occurs at a lower temperature when aminosilane is present. Results also confirm that the organofunctional group on the silane reacts with the elastomer. XPS analysis of the silane-coated fluoroelastomer heated at 120 °C, 160 °C and 200 °C reveals that dehydrofluorination of the polymer is one of the steps in the reaction. It is our hypothesis that the amine group on the aminosilane is a contributor to the dehydrofluorination of the fluoroelastomer.
Comparison of Hyperelastic Models for Rubber-Like Materials
Authors: Marckmann G. , Verron E.
Published: February 2011

The present paper proposes a thorough comparison of twenty hyperelastic models for rubber-like materials. The ability of these models to reproduce different types of loading conditions is analyzed thanks to two classical sets of experimental data. Both material parameters and the stretch range of validity of each model are determined by an efficient fitting procedure. Then, a ranking of these twenty models is established, highlighting new efficient constitutive equations that could advantageously replace well-known models, which are widely used by engineers for finite element simulation of rubber parts.
The Correlation of Fatigue Crack Growth Rates in Rubber Subjected to Multiaxial Loading Using Continuum Mechanical Parameters
Authors: Mars W. V. , Fatemi A.
Published: February 2011

Although both the crack nucleation and growth stages of the fatigue failure process in rubber are manifestations of the same characteristic material behavior, the nucleation stage deserves special attention. In this case, continuum mechanical parameters may be used to characterize the driving forces of small cracks, without reference to the geometry of the test piece. The ability to estimate crack driving forces from continuum mechanical parameters during the growth process of small cracks has been investigated by correlating three different parameters (maximum principal strain, strain energy density, and cracking energy density) to rates of crack growth observed photographically during fatigue tests on initially uncracked specimens. Significant scatter in crack growth rates was observed resulting from high crack density and crack interactions. These results are also compared to crack growth measurements made on a pure shear (planar tension) test piece. The difference between continuum parameters that refer to a specific material plane, and those that do not is emphasized. Generally, the maximum principal strain and cracking energy density parameters provided similar levels of correlation. The strain energy density parameter consistently gave the poorest correlation. An advantage of the cracking energy density is that it considers the experiences of specific planes embedded in the material (i.e. it is a plane-specific parameter).
Recycled Rubber: The Rubber Granulate - Virgin Rubber Interface
Authors: Kumar P. , Fukahori Y. , Thomas A. G. , Busfield J. J. C.
Published: February 2011

Reusing granulates derived from old tire stock and other sources in high tech engineering applications is still considered a high risk option. In addition to ensuring that the granulates are correctly identified, it is important to know how the incorporation of these materials alters the intrinsic flaw size of a finished product and to see how much the strength of the interface between these materials and the virgin materials compares to the basic strength of the virgin stock and the granulates. This paper explores possible techniques that can examine both properties so that an informed evaluation of the effect of reincorporating granulates can be established in practice.
Goodyear Medalist Lecture. Rubber Friction and its Relation to Tire Traction
Authors: Grosch K. A.
Published: February 2011

Rubber friction differs from that of hard solid materials in that it is not linearly related to the normal load and it depends strongly on sliding speed and temperature. There exists an interrelation between these two variables on their effect on the friction coefficient, first observed for the viscosity of liquids and generally described by the universal WLF transformation equation. The friction coefficient at a constant load is then described by a so-called master curve. Such master curves have been obtained on different types of surface and for gum rubbers as well as filled rubbers on wet and dry surfaces and it is shown that they may also be obtained on ice. The shape of the curve and position on the log(aTv) axis depends on the polymer and the track surface structure indicating that two distinct processes determine the friction: adhesion friction akin to a molecular relaxation process and a deformation process in which energy is lost due to the cyclic deformation of the rubber by the surface asperity. To obtain such a master curve it is necessary to keep the experimental speeds so low that the temperature rise in the contact area can be neglected. In practical tire tests, sliding speeds are high and hence the temperature rises with speed. Since the WLF equation is a negative function of temperature, the range of log(aTv) is limited. If thermocouples are used as sliders on rubber, it is shown that the experimental curves as function of speed can be transformed into a part of a master curve. For compound development friction tests, a limited range of track temperatures and speeds are sufficient to ensure a high correlation with road test data. A single point laboratory measurement may correlate with road tests if carefully chosen. More usually, it leads to misleading conclusions. Side force measurements at a reasonably large slip angle also reflect the friction coefficient and are a useful laboratory tool to evaluate the traction properties of tread compounds.
Thermoplastic Elastomers Based on PP/EPDM Blends by Dynamic Vulcanization
Authors: Naskar Kinsuk
Published: February 2011

This review article introduces various aspects of dynamic vulcanization as applied to thermoplastic elastomers (TPEs). The classification of polymer blends and TPEs, the development of thermoplastic vulcanizates (TPVs), and the application of different types of crosslinking systems with special emphasis on peroxides/co-agents, and phenolic resins as crosslinking agents for polypropylene / ethylene propylene diene rubber (PP/EPDM) blends are primarily reviewed. The morphology and rheology of these TPVs are also touched upon.
Elastomers - An Engineering Material
Authors: Hertz Daniel L.
Published: February 2011

Elastomers are engineering materials. Defined as nonlinear viscoelastic solids; applications are normally deformations under twenty five (25) percent. Conventional engineering values of shear modulus G and Young's modulus E can be determined in this relatively linear section of the stress-strain relationships. The viscoelastic description indicates a time/temperature relation response. Treloar notes that G is both the shear modulus value and the elastic constant. The high bulk modulus allows us to assume E=3G thus we have several approaches to develop G and utilize the equation G=NκT=ρRT/Mc, (hereby ρ is density, R gas constant, Mc average chain molecular weight, T temperature Kelvin). This allows us to monitor aging by changes in Mc that occur due to network aging. The aging process will be monitored by strain energy density changes, compressive stress-relaxation (CSR) and dynamic mechanical rheologic testing (DMRT)
Development and Properties of Novel Thermoplastic Elastomer Based on Poly (Phenylene Ether)
Authors: Gupta Samik , Krishnamurthy Raja , Preschilla Nisha , Biswas Amit , Bhowmick Anil K.
Published: February 2011

A series of novel thermoplastic elastomers (TPEs) based on poly (phenylene ether)(PPE), which is an engineering thermoplastic with a glass transition temperature >200 °C, has been developed. The resulting blend based on PPE, Polystyrene (PS), Ethylene Vinyl Acetate (EVA) and a tri-block copolymer, Styrene-Ethylene-Butylene-Styrene (SEBS), met all the key performance criteria for thermoplastic elastomers in terms of melt processability, tensile elongation, tension set and recyclability. Depending on Flory's interaction parameter and critical surface tension value, the elastomeric components of the blends were selected. Morphological analysis of the blend using Transmission Electron Microscopy indicated a unique microstructure, wherein EVA domains were dispersed in a mainly co-continuous matrix comprising of the blend of PPE-PS/SEBS. Differential Scanning Calorimeter and Dynamic Mechanical Analysis were done to evaluate the thermal transitions of the blend and to throw light on the interactions between the various components of the blend. Thermogravimetric analysis indicated that PPE played a critical role by increasing the temperature of the onset of degradation of the blend. A comprehensive study of the structure-property correlations of this unique blend has been undertaken.
Highly-Purified Natural Rubber by Saponification of Latex: Analysis of Residual Proteins in Saponified Natural Rubber
Authors: Yunyongwattanakorn Jintana , Tanaka Yasuyuki , Sakdapipanich Jitladda , Wongsasutthikul Voratep
Published: February 2011

Highly purified natural rubber (NR) was prepared by saponification of fresh latex (FL-latex) and preserved high-ammonia latex (HA-latex) in the presence of surfactant to reduce the residual proteins in resulting solid NR. Saponification of latex diluted to 30% DRC was carried out with 1–7% (w/v) sodium hydroxide at room temperature for 1–7 hr at 70 °C and coagulated with formic acid. The nitrogen content of NR obtained by coagulation of the saponified latex markedly decreased to less than 0.014% by centrifugation of the saponified latex or soaking the coagulum in aqueous sodium hydroxide solution. The nitrogenous compounds from saponified NR (SAP-NR) were extracted with sodium dodecyl sulphate (SDS) aqueous solution and subjected to SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis to check the molecular weight of extracts. The extract from SAP-NR and deproteinized NR by protease (DPNR) for comparison was subjected to the analysis of allergic protein by FIT Kit method, based on Enzyme-Linked Immunosorbent Assay (ELISA) method. No extractable protein was observed in SAP-NR, whereas DPNR contained 1.5 μg/ml proteins. The results from SDS-PAGE analysis and FIT Kit test demonstrated that NR free from allergic proteins is obtainable by saponification of FL-latex with 1.5% NaOH at 70 °C for 1 hr or at room temperature for 24 hr.
Manufacture of Thermoplastic Elastomer Tubes by Water Assisted Injection Molding Technology
Authors: Liu Shih-Jung , Lin Kun-Yeh , Liu Che-Chi
Published: February 2011

The objective of this study was to manufacture thermoplastic elastomer tubes by a novel water assisted injection molding technology and to experimentally investigate the effects of various processing parameters on the molded parts quality. Styrene-ethylene/butylene-styrene (SEBS) compounds based thermoplastic elastomers were used for all the experiments. Experiments were carried out on a lab-developed water assisted injection-molding system, which included a water pump, a water injection pin, a water tank equipped with a temperature regulator, a pressure accumulator, and a control circuit. A porous type water injection pin was designed and made to mold the parts. After molding, the lengths of water penetration as well as the hollowed core ratios in molded tubes were measured. The effects of different processing parameters on the hollowed core ratios were determined. It was found that the melt temperature and water injection delay time were the principal factors influencing the water penetration behaviors. In addition, a comparison has been made between the parts molded by water assisted injection molding and gas assisted injection molding. The results suggest that water assisted injection molded parts mold parts with less residual wall thickness distributions along the channel. However, thermoplastic elastomers molded by water exhibited higher wall thickness difference at curve sections than those molded by gas.
Anionic Synthesis of Trialkoxysilyl-Functionalized Polymers
Authors: Quirk Roderic P. , Ocampo Manuela , King Rebecca L. , Polce Michael J. , Wesdemiotis Chrys
Published: February 2011

A new general functionalization methodology (GFM) is applied to the synthesis of trimethoxysilyl-functionalized polymers. This GFM involves (a) the preparation of a well-defined polymeric organolithium compound (PLi) using alkyllithium-initiated anionic polymerization; (b) quantitative silyl hydride-functionalization of PLi with chlorodimethylsilane to form PSi(CH3)2H; (c) hydrosilation of PSi(CH3)2H with vinyltrimethoxysilane in the presence of Karstedt's catalyst. The desired PSi(OCH3)3 was obtained in > 80% yield. The product was characterized by SEC, 1H and 13C NMR and MALDI-TOF mass spectrometry.
A Comparative Investigation of Surface Modification of Carbon Black and Silica by Plasma Polymerization
Authors: Mathew T. , Datta R. N. , Dierkes W. K. , Noordermeer J. W. M. , van Ooij W. J.
Published: February 2011

Carbon black and silica are widely used active fillers in the rubber industry to improve the physical and dynamic properties of rubbers. The surface energy difference between rubbers and these active fillers is large, which has a negative influence on the stability of their dispersion in the rubber matrix and on the distribution in blends of different rubbers. Reduction of the surface energy of carbon black and silica is aimed for by modifying their surfaces. Plasma polymerization is utilized to modify the surface of carbon black and silica by depositing a thin film over its surface. The modified fillers are characterized using thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToF-SIMS). The studies show that carbon black and silica behave differently towards surface modification by plasma polymerization. The difference in behavior of carbon black and silica is related to the availability of active sites on their surface during exposure to the plasma atmosphere. In this paper the mechanistic aspects of surface modification by plasma polymerization are also discussed.
The Application of High Resolution Chemical Imaging Techniques for Butyl Rubber Blends
Authors: Winesett Donald A. , Tsou Andy H.
Published: February 2011

Atomic Force Microscopy (AFM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging, and Scanning Transmission X-ray Microscopy (STXM) are applied to identical series of elastomeric blends to evaluate the relative strengths and weaknesses of each imaging technique. AFM is a high resolution, high contrast technique with straight forward sample preparation that derives contrast through elastic modulus variations, but, when used in a conventional mode, has limited chemical specificity. ToF-SIMS imaging can map phases, detect trace levels (ppm) of additives and other chemical species based on relatively straight forward sample preparation, but has poorer spatial resolution and the instrumentation is expensive. STXM has excellent chemical specificity and good spatial resolution but is only available at a beamline and requires more advanced sample preparation. Each technique will be overviewed briefly and relative merits of each will be compared based on evaluations of some commercially relevant rubber blend materials.
Analysis of Stress-Strain Data for Dry and Swollen Rubbers by a New Tube Model of Rubber Elasticity Based on Finite Chain Extensibility
Authors: Hoei Yoshio
Published: February 2011

New stress-strain equations have been extensively tested for both unswollen and swollen rubbers, which were very recently derived from a new non-Gaussian tube model of rubber elasticity that incorporates the effect of finite chain extensibility. Particularly, as core parameters, they involve the junction-fluctuation suppression parameter (h) of Dossin and Grassley and the tube deformation index (γ) of Gaylord. The best-fits of the equations to experimental literature data for unswollen and swollen networks have been done. The results are very good with sufficiently small departures of theory from experiment and the two fitting parameters can consistently well explain the molecular situations of the networks.
Rubber Oxidation and Tire Aging - A Review
Authors: Baldwin John M. , Bauer David R.
Published: February 2011

While a new tire may have excellent resistance to crack initiation and propagation between the steel belts, an aged tire of the exact same construction can exhibit dramatically reduced crack growth resistance, which in some cases may contribute to tire failure. This article will review the research that has gone into quantifying the rate of oxidation the steel belt rubber oxidizes in different climates from tire samples retrieved from consumers' vehicles. The information obtained from the field is then compared to data collected from various resources attempting to develop accelerated tire aging protocols. Finally, methods for potentially improving tire aging are reviewed.
Atomic Force Microscopy (AFM) for Rubber
Authors: Johnson Lili L.
Published: February 2011

In this review, first, the development of atomic force microscopy as an imaging technique, as a surface force apparatus, and as a nanoindenter was illustrated using experimental studies. The experimental analysis of atomic force microscopy emphasizes the empirical methods of achieving high resolution imaging through controlled forces between tip and sample interactions. Second, mapping mechanical properties on nanometer scale by atomic force microscopy is presented with both experimental investigations and selection of elastic models. Elastomer crosslink density was mapped using atomic force microscopy combined with elastic theories. The force — penetration depth investigation of crosslink density for elastomer by AFM shows linear correction with both experimental studies using Dynamic Mechanical Thermal Analysis (DMTA) and classic swelling method and calculation using statistical rubber elasticity theory. Last, the focus is on the understanding of atomic force microscopy for practical applications. Filler dispersion and blends structure are demonstrated for automotive applications. Micro phase separation was intensely studied for film industries. Morphology of composites is investigated for the applications of tire, automotive and foaming industries.
Rubber Abrasion and Tire Wear
Authors: Grosch K. A.
Published: February 2011

Rubber abrasion is essentially a mechanical tearing process and has been linked with the rate of a cut growth process as function of the tearing energy dissipated in the contact area between rubber and track which leads inevitably to considerable temperature rises at the points of highest stress concentration i.e. at the points at which a mechanical detachment of abraded particles is most likely. This leads to thermal degradation and oxidation as important secondary mechanisms which may well decide whether a compound performs better or worse than a reference outweighing the mechanical properties. A laboratory method has been developed, using the LAT 100 test equipment, which uses the energy dissipation and slip speeds in the contact area of a rubber sample wheel, rotating under slip, to evaluate the abrasion performance of a compound over a wide range of these variables. The resulting equations can be used either to test directly the correlation between laboratory and road test results which is usually good over a limited range, or they are used in a road test simulation program with well defined road test conditions. The latter gives a set of single compound ratings and tire lives. These depend however strongly on the chosen test conditions and in that they reflect reality
Effect of Fillers on Wet Skid Resistance of Tires. Part II: Experimental Observations on Effect of Filler-Elastomer Interactions on Water Lubrication
Authors: Wang Meng-Jiao , Kutsovsky Yakov
Published: February 2011

It was demonstrated previously that on the worn surface of vulcanizates during wet skid tests, carbon black is covered by rubber whereas silica particles are at least partly exposed. In this report, the experimental results of the effects of carbon black and silica on wet skid resistance measured by various test methods and under different conditions are explained based on the “Three Zone Concept” of the contact area of tread compounds with the track surface during sliding or rolling. The three zones are water film squeezing, transition and traction zones. In the first two zones, where hydro-dynamic and micro-elastohydrodynamic lubrication mechanisms are dominant, silica is beneficial for wet friction. In the traction zone, where friction is governed by boundary lubrication, carbon black is preferred. Under test conditions where the water squeezing and transition zones are more developed, such as at high speed, lower temperature, smoother track surface, lower load, higher slip angle, and ABS brake, the silica shows better performance, but otherwise where the traction zone is larger, carbon black gives higher wet skid resistance. Accordingly, a new carbon-silica dual phase filler CSDPF 4210 that is characterized by high surface coverage with silica has been developed. With this material, the wet skid resistance of a passenger tire on a car with ABS at high speed and smooth road surface is significantly improved.
Alkylphenol Disulfide Polymer Accelerators and the Vulcanization of Isobutylene Based Elastomers
Authors: Rodgers Brendan , Solis Scott , Tambe Nitin , Sharma Bharat B.
Published: February 2011

Vulcanization of isobutylene/isoprene copolymer (butyl rubber) using sulfur and organic accelerators is facilitated by the presence of the carbon-carbon double bond in the copolymer isoprenyl unit. The low number of unsaturated monomer units, usually in the order of 2%, has traditionally necessitated use of ultra-fast accelerators such as tetramethyl thiuram disulfide (TMTD) or zinc dimethyldithiocarbamate (ZMDC). Use of such accelerators can result in formation of nitrosamines which may be undesirable. There are a number of alternatives to thiuram and dithiocarbamate cure systems such as use of xanthates and phosphate based accelerators. Alkylphenol disulfide based accelerators also enable attainment of favorable properties when used in butyl and halobutyl compounds. Use of alkylphenol disulfide accelerators in butyl rubber compounds can allow improvement in reversion resistance, adhesion to natural rubber tire casing compounds, and aged property retention. In bromobutyl compounds containing alkylphenol disulfide accelerators in binary (two accelerators) or tertiary (three accelerators) cure systems, adjustment in cure rate to meet specific requirements and aged property retention is possible. This, fifth in a series of studies on the vulcanization of isobutylene elastomers, explores the use of alkylphenol disulfide cure systems for vulcanization of both butyl and bromobutyl rubbers and is intended to provide a starting point for further development work.
Biodegradable Elastomeric Vulcanizates
Authors: Przepiórkowska A. , Chrońska K. , Prochoń M.
Published: February 2011

This article contains the review of biodegradable elastomeric vulcanizates.
Strain-Induced Crystallization of Natural Rubber: Effect of Proteins and Phospholipids
Authors: Amnuaypornsri Sureerut , Sakdapipanich Jitladda , Toki Shigeyuki , Hsiao Benjamin S. , Ichikawa Naoya , Tanaka Yasuyuki
Published: February 2011

The effects of proteins and phospholipids in natural rubber (NR) on the strain-induced crystallization behavior during uniaxial deformation were studied by in-situ synchrotron wide-angle X-ray diffraction (WAXD) technique and simultaneous measurements of stress-strain relation. The influences of proteins and phospholipids in NR were evaluated separately by decomposition methods using deproteinization and lipase treatment, respectively. It was found that both components form a naturally occurring network, which is responsible for the strain-induced crystallizability of unvulcanized NR and the corresponding high mechanical property. This network also plays a significant role in strain-induced crystallization of vulcanized natural rubber.
Influence of Different Nanofillers and their Dispersion Methods on the Properties of Natural Rubber Nanocomposites
Authors: Bhattacharya Mithun , Maiti Madhuchhanda , Bhowmick Anil K.
Published: February 2011

The effects of varying morphological and chemical constitution of nanofillers and various dispersion methods on natural rubber nanocomposites prepared by conventional processing techniques were determined by incorporating various nanofillers like montmorillonite, sepiolite (SP), hectorite, carbon nanofiber (F) and expanded graphite. When compared with the gum, SP filled (4 phr) nanocomposite exhibited an increment of 26% in the modulus and F (6phr) increased the tear strength by 18%, over the gum. Nanofiller dispersion was enhanced by various compatibilization and dispersion techniques which helped SP introduce 56 and F 113% increment in the modulus of the nanocomposites, over the gum rubber vulcanizate. It also rendered 28% improvement in the tear strength of F filled system. Deeper insights into the material properties were obtained through dynamic mechanical and swelling studies. Property-morphology correlation of the hybrids was performed through X-ray Diffraction, Atomic Force Microscopy and Transmission Electron Microscopy. Surface energy (SE) studies exhibited that the higher surface energy of SP (38 mJ/m2) and F (44 mJ/m2) than the rubber (35 mJ/m2) ensured necessary wetting and hence was responsible for improvement of the properties. Using SE, cleavage energy and work of adhesion data, a new mechanism based on adsorption followed by shear of polymer-bound nanofillers was suggested.