bluuebunny/crossref_metadata_2025 huggingface dataset:
Online Method for Characterization of the Homogeneity of Rubber Compounds Filled with Non-Conductive Carbon Black
Authors: Le H. H. , Tiwari M. , Ilisch S. , Radusch H-J.
Published: February 2011

In the present work, the effect of carbon black (CB) type on the electrical conductance of CB filled rubber compounds measured online in the internal mixer and the corresponding CB dispersion were investigated. The CB dispersion is strongly affected by the specific surface area and structure of CB which can be directly monitored by use of the online electrical conductance method. The effect of CB mixture ratio of a high conductive CB and a non-conductive one on the online electrical conductance was investigated for CB filled rubber compounds. By addition of a small amount of a high-conductive CB type into a non-conductive CB filled rubber compound, a characteristic online conductance - time characteristic is observed that is a result of the formation of a joint network of the two CB types. It could be shown, that such a characteristic is suitable to monitor the dispersion process of the non-conductive CB in the rubber compound.
Aging of Black Filled Rubber under Deformation
Authors: Ahagon Asahiro , Kirino Yoshiaki
Published: February 2011

Prolonged dynamic deformation of a rubber is found to significantly accelerate oxidative crosslinking due to mechanochemical oxidative crosslinking. The extent of acceleration is larger at lower temperatures and increases with increasing strain. The activation energy of the rate of oxidative crosslinking decreases with increasing strain toward the highest value among the unit reactions of oxidative chain reaction cycle or the value of diffusion of oxygen, which is much smaller than that of static aging. On the other hand, static deformation is also found to accelerate oxidative crosslinking but to considerably lesser extents. Mechanochemical acceleration can be noticed only in the early stage of prolonged deformation. The degree of acceleration in prolonged deformation increased with increasing strain without change in the activation energy. The acceleration observed in prolonged static deformation is considered to arise from the increased area of exposure to the oxidizing atmosphere. It appears that mechanochemical acceleration is merely spent to compensate the loss in crosslink density upon deformation in this case.
Preparation and Properties of New in-situ Acrylic Copolymer/Terpolymer- Clay Hybrid Nanocomposites
Authors: Patel S. , Bandyopadhyay A. , Vijaybaskar V. , Bhowmick Anil K.
Published: February 2011

Acrylic copolymer- and 5% acrylic acid (AA) modified terpolymer-hybrids with unmodified montomorilonite clay (Cloisite Na) and organo-modified clay (Cloisite 10A) were synthesized by in-situ free radical bulk polymerization. Hybrid nanocomposites were investigated by Atomic Force Microscopy (AFM), X-ray diffraction (XRD) technique, thermogravimetric analysis (TGA), dynamic mechanical and mechanical properties. XRD results suggested polymer intercalation in both unmodified and organo-modified clay in the copolymer and terpolymer hybrids. AFM analysis further confirmed these results. Cloisite 10A hybrids and the terpolymeric nanocomposites demonstrated superior mechanical and dynamic mechanical properties. Terpolymer-clay hybrids with 9 wt% Cloisite 10A also showed higher thermal stability. The possible reasons for improvement of mechanical properties and thermal stability were discussed with reference to the structure and interaction.
Modeling the Equilibrium Compressed Void Volume of Carbon Black
Authors: Joyce George A. , Henry William M.
Published: February 2011

In this study, a broad range of furnace carbon blacks from very low to very high structure and fineness were evaluated for compressed void volume, colloidal and in-rubber properties. Compressed void volume measurements were investigated over applied pressures of approximately 18–159 MPa using a commercially available instrument. The void volume data was statistically modeled using logarithmic pressure curves, exponential energy curves and an inverse variable root curve. Parameters generated from the void volume models were analyzed using advanced non-linear multiple regression resulting in strong relationships to crushed oil absorption numbers and in-rubber properties. A comparison of void volume and oil absorption numbers indicates the void volume method offers a significant improvement in describing carbon black structure. The relationship between void volume and parameters related to rubber reinforcement found in this work is a confirmation that compressed void volume is more specific to primary structure than oil absorption numbers. Compressed void volume should provide the carbon black industry a faster, more meaningful and lower cost structure characterization than oil absorption methods.
Microdispersion of Carbon Blacks in Rubber, Part I: Some Quantitative Aspects by AFM Image Analysis
Authors: Wang C. C. , Wu S. H. , Donnet J. B. , Wang T. K.
Published: February 2011

The microdispersion state of carbon blacks in an emulsion SBR matrix has been observed by atomic force microscopy (AFM) and the images analyzed quantitatively. The fillers were well dispersed in the rubber samples. Different parameters, such as the surface fraction of fillers in images, particle size distance distributions, have been extracted and the main results are presented.
Tire-Cord Adhesion: How the Source of Zinc Can Influence the Structure of the Bonding Interface
Authors: Fulton W. Stephen
Published: February 2011

Many excellent, fundamental studies on tire cord adhesion have described how zinc diffuses through the rubber brass interface to be sulphidized to form zinc sulphide and how zinc combines with oxygen to create zinc oxide during dezincification. The source of zinc is assumed primarily to originate in the brass of the tire cord. However, studies using isotope-depleted zinc oxide in the rubber formulation are presented here which reveal how zinc from different sources is distributed within the bonding interface, before and after aging. To differentiate between two sources of zinc, i.e. brass and compound, zinc oxide made from 64Zn-depleted zinc was mixed in the formulation and Secondary Ion Mass Spectroscopy (SIMS) depth profiling was used to follow the zinc isotope ratios within the interfacial layers. As the relative ratios of the various zinc isotopes changed during depth profiling, the contribution of zinc from each source could be determined. Profiles were obtained for unaged, heat-aged and humidity-aged samples and in each case a relatively large amount of zinc that originated in the rubber compound was shown to be incorporated as zinc sulphide during the thickening of the interfacial layer. Heat-ageing produced a thickened dendritic structure that was visualized in Transmission Electron Microscopy (TEM) using a sample prepared by focussed ion beam (FIB) techniques. This study was complemented by Energy Dispersive X-Ray (EDX) analysis, producing elemental linescans to illustrate more fully the role of zinc during the thickening of the bonding interface.
Effects of Cure Systems of Ground Rubber and Rubber Matrix on their Adhesion and Crosslink Structures
Authors: Kim S. W. , Park H. Y. , Seo K. H.
Published: February 2011

There has been a great deal of research on the effects of ground rubber (GR) on the cure characteristics of GR-filled rubber compounds. It has been known that the cure systems of the rubber matrix and GR also had an effect on the cure characteristics and physical properties of GR-filled compounds. In this study, the variation of the crosslink density and crosslink types of recured vulcanizates and fresh vulcanizates, with respect to the cure systems, were investigated by using a three-layered model. In addition, the adhesion forces between recured vulcanizates and fresh vulcanizates were measured, and the fracture surfaces were examined. Depending on the cure systems, the changes in the crosslink density and crosslink types of recured and fresh vulcanizates varied significantly and the failure modes of adhesion specimens were also different.
Nanoscale Rubber Reinforcement: A Route to Enhanced Intercalation in Rubber-Silicate Nanocomposites
Authors: Al-Yamani Faisal , Goettler Lloyd A.
Published: February 2011

Addition of organo-modified layered silicates (e.g., montmorillonite clay) to polymer matrices can produce effective polymer nanocomposites by intercalation of macromolecules into the interlayer galleries. Flexible rubber nanocomposites represent an untapped application of this technology that is still in an early stage of development. This research focuses on the enhancement of rubber matrices through the incorporation of different types of layered silicates along with a dispersion agent, hexamethoxymethylmelamine (HMMM). Styrene-co-butadiene rubber (SBR) and acrylonitrile-co-butadiene rubber (NBR) nanocomposites were prepared via a straightforward rubber compounding process and investigated through wide angle x-ray diffraction to determine the resulting clay morphology. The mechanical evaluation of the rubber nanocomposites was by tensile and tear testing. The dispersing agent affected both the morphology, registered as an increase in the gallery height, and mechanical properties, which showed significant additional reinforcement with the optimal combination of organoclay and rubber type. This work thus demonstrates the positive benefit of such a dispersion agent.
Reactive Blending, Reinforcement and Curing of NR/BR/EPDM Compounds for Tire Sidewall Applications
Authors: Sahakaro K. , Naskar N. , Datta R. N. , Noordermeer J. W. M.
Published: February 2011

Tire sidewall compounds are generally formulated using NR and BR to achieve the required dynamical properties. The most widely used antiozonant, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), is a staining, toxic and environmentally unfriendly substance. Incorporation of EPDM into NR/BR blends improves ozone resistance, but leads to poor properties because of differences in filler affinity and cure incompatibility of the rubber components. In this work, the cure incompatibility is overcome by utilizing a reactive processing technique, making use of the most commonly used accelerator CBS and sulfur. The entire amount of curatives is first added into the EPDM. After a thermal pretreatment step related to the scorch time of the EPDM, the modified EPDM is mixed with pre-blended NR/BR. The reactive blends show significant improvements of physical properties in comparison with those of conventional straight mixes, due to improvement of the crosslink and carbon black distributions, confirmed by AFM and TEM images. The physical properties of the reactive mixed NR/BR/EPDM blends are equivalent or even superior to regular filled NR/BR blends for tire sidewall applications. The blend with 30 phr of EPDM has excellent ozone resistance while 6PPD can be totally omitted from the formulation.
Environmental Friendly Surface Treatment of SBS Rubber with Acidified Chloramine T Aqueous Solutions
Authors: Navarro-Bañón M. Virtudes , Pastor-Blas M. Mercedes , Martín-Martínez José Miguel
Published: February 2011

As environmental friendly alternative to the halogenation treatment with trichloro isocyanuric acid solutions in organic solvents (TCI/MEK), in this study a water-based surface treatment for rubber materials based in chloramine T aqueous solutions has been proposed. It was found that the effectiveness of chloramine T (CT) (N-chloro-sodium-p-toluenesulphenamide) as chlorinating agent for rubber depends on the pH of the chlorinating solution. The surface modifications and adhesion in one SBS rubber treated with aqueous solutions of CT has been studied. Acidification of CT aqueous solutions produced the formation of dichloramine T (DCT) and hypochlorous acid (HClO), species which reacted with C = C bonds of the butadiene units. A decrease in the pH of the CT aqueous solutions produced more extended surface modifications and improved adhesion properties in the joints produced with chlorinated SBS rubber and waterborne polyurethane adhesive. T-peel strength values obtained were slightly lower than those obtained for the SBS rubber surface treated with the organic solvent chlorinating system (TCI/MEK). The solvent effect leading to local swelling and therefore to deeper modifications in the rubber near surface properties was not present with water based solutions, and then, the modifications were much more superficial. On the other hand, acidification with hydrochloric acid produces deposition of NaCl crystals on the SBS rubber surface. Thus, acidification of the chloramines T solution with sulfuric acid was preferable.
Scanning Transmission X-Ray Microscopy of Curative and Filler Migration of Inner Liner Compounds
Authors: Winesett D. A. , Tsou A. H.
Published: February 2011

Materials of significance in the rubber industry generally consist of a complex blend of elastomers, fillers, curing agents and other additives. Elucidating the complex microstructure-to-property relationship of these materials is essential for optimal product development. This requires characterization techniques that are capable to differentiate, map, and quantify these similar materials with sufficiently high spatial resolution. A technique that can provide such chemical microspeciation is Scanning Transmission X-ray Microscopy (STXM). STXM is a beamline based microscopy that utilizes the chemical specificity of Near Edge X-ray Absorption Fine Structure (NEXAFS) combined with zone plate optics to achieve high spatial resolution (< 50 nm) and low beam damage to allow the successful characterization of multi-component materials that would be difficult or impossible with other techniques. A brief introduction to the technique will be presented along with example applications showing curative and filler distribution mapping in multi-component elastomeric systems.
Influence of some Non-Rubber Components on Aging Behavior of Purified Natural Rubber
Authors: Tuampoemsab Surakit , Sakdapipanich Jitladda , Tanaka Yasuyuki
Published: February 2011

Skim rubber (SR) was obtained by coagulation of the serum phase separated in the course of preparation of concentrated natural rubber (NR) latex. Saponified skim rubber (SSR) was prepared by soaking of SR with aqueous sodium hydroxide. The effect of non-rubber components on the thermal oxidative degradation of SSR was analyzed under mild and heating conditions for SSR and deproteinized natural rubber (DPNR) as a model of purified NR. The effect of gel, ash, ester, nitrogenous and heavy metal on aging properties was analyzed for SSR and DPNR comparing with SR and NR coagulated from high ammoniated latex (HANR), respectively. SSR contained Cu ion of 37 ppm even after purification of SR by saponification, although other transition metal ions were not detected. The accelerated decomposition of SSR was presumed to be due to the activation of residual Cu ions as well as the decrease of nitrogenous substances acting as antioxidants after saponification. The effect of Cu ions was confirmed by heat-aging test at 140 °C for 150 min for DPNR mixed with Cu compounds such as [Cu(NH3)4]2+, CuSO4 and CuO. Butylated hydroxytoluene (BHT) was not effective to prevent the thermal oxidation of SSR samples, although it was effective for SR. This suggested the influence of residual Cu ion activated by treatment of SR with aqueous sodium hydroxide.
Application of NR-Based Latex Reclaim: The Link Between Structure and Properties
Authors: Dierkes W. K. , Rajan V. V. , Noordermeer J. W. M. , Joseph R.
Published: February 2011

Natural rubber based waste latex rubber (WLR) that is reclaimed with diphenyldisulphide by a thermo-mechanical process is blended with virgin rubber in different proportion to study the change in mechanical and viscoelastic properties. Two types of WLR differing mainly in the amount of polysulfidic linkages are reclaimed and blended with a virgin rubber compound with and without adjustment of the curing system, the former in order to compensate for the extra input of sulfur and accelerators due to the addition of reclaim. The cure behavior, final crosslink density and distribution, mechanical properties and dynamic viscoelastic properties of the blends with reclaimed WLR are compared to the property profile of the virgin material. The morphology of the blends as well as sulfur distribution between the matrix and the reclaim particle is analyzed. With increasing concentrations of WLR reclaim, tensile strength, tear strength and elongation at break decrease, whereas modulus at 100% elongation, compression set and hardness show an increase. The storage modulus of the vulcanized rubber blends decreases with increasing WLR reclaim content in the blend. Swelling measurements show that the crosslink density is reduced for the adjusted cure system but increased for a fixed cure system. These influences of reclaimed WLR on the property profile of a virgin compound will be discussed fundamentally in terms of morphology and crosslink distribution.
Fatigue Life Prediction for Elastomeric Structures
Authors: Mars W. V.
Published: February 2011

Elastomeric structures subjected to fluctuating loads can fail due to the nucleation and growth of cracks. To prevent such failures requires understanding of the physics underlying fatigue failure, approaches for characterizing material behavior, and methods for evaluating the effects of a given duty cycle. Duty cycles can be complex, often involving simultaneous loading in multiple directions, and non-periodic variations of the load. By considering how the loads applied to a structure are transformed into the experiences of individual cracks, a rational framework for predicting fatigue life can be developed.
Mechanistic Investigations into the Adhesion between RFL-Treated Cords and Rubber. Part I: The Influence of Rubber Curatives
Authors: Wennekes W. B. , Noordermeer J. W. M. , Datta R. N.
Published: February 2011

The adhesion between virgin textile cords and rubber is always weak, because of significant differences between fiber and rubber in modulus, elongation, polarity as well as reactivity. In order to improve the adhesion, it is customary to use adhesive systems, which act as bridges between elastomer and reinforcement. These are commonly based on Resorcinol/Formaldehyde/Latex (RFL) dips. For polyester and aramid fibers, two dip systems are applied. The first one is an epoxy pre-dip and the second dip is a RFL dip again. Although several mechanisms are proposed to explain the role of RFL, the majority of these explanations are based on assumptions rather than proper scientific investigations. In this paper an attempt is made to understand the role of the rubber vulcanization system on RFL-to-rubber bonding as judged by measuring the H-pullout force, Strap Peel Adhesion Force (SPAF) and the mechanical properties of the compounds. A positive correlation is found between the optimum cure time (t90) of the rubber compounds and the pullout and peel force. In literature this is commonly explained by the lack of curative migration from the rubber into the dip when t90 is low. In the present paper curative migration is monitored by scanning electron microscopy coupled to an energy dispersive X-ray spectrometer (SEM-EDX). A strong enrichment of curatives in the RFL dip near the interface is observed. A high accelerator loading results in a low t90 of the rubber compound as well as a more pronounced enrichment of curatives in the dip near the interface. Therefore the drop in adhesion does not occur because of lack of curative migration from rubber to the RFL layer, but more likely due to overcure of the latex in the dip, causing a brittle layer resulting in low pullout and peel strengths.
Mechanistic Investigations into the Adhesion between RFL-Treated Cords and Rubber. Part II: The Influence of the Vinyl-Pyridine Content of the RFL-Latex
Authors: Wennekes W. B. , Datta R. N. , Noordermeer J. W. M.
Published: February 2011

The adhesion between virgin textile cords and rubber is always weak, because of significant differences between fiber and rubber in modulus, elongation, polarity as well as reactivity. In order to improve the adhesion, it is common to use adhesive systems, which act as bridges between elastomer and reinforcement. These are commonly based on Resorcinol/Formaldehyde/Latex (RFL) dips. Despite the fact that this technique was invented in 1938 and no major improvements have been achieved since then, the mechanism by which the adhesion is obtained is still unclear. This paper contributes more fundamental understanding of RFL to rubber bonding. In previous work an enrichment of curatives at the RFL-rubber interface was observed by use of a Scanning Electron Microscope coupled to an Energy Dispersive X-ray spectrometer. In the present paper, the same method is used to determine the degree of enrichment for several RFL formulations, based on latices with varying vinyl-pyridine (VP) contents. The vinyl-pyridine content is varied by copolymerization of various VP terpolymers. Adhesion decreases with increasing vinyl-pyridine content for most rubber compounds. For aN NR compound with low accelerator content and a NR/SBR blend, an optimum vinyl-pyridine content of 10% is observed.
On Effective Modeling of Laminated Cord-Rubber Composites
Authors: Gurvich Mark R.
Published: February 2011

The major challenge in modeling of laminated cord-rubber composites (CRC) is to achieve desired predictive accuracy as well as maintain computational efficiency of corresponding numerical solutions. Existing modeling methods are primarily based on a) more traditional theories developed for fiber-reinforced polymer-matrix laminates and b) rebar- and shell based FEA approaches. Although mentality of these methods is widely used in rubber and tire engineering, these models often significantly simplify important issues of non-linearity and 3-D nature of interlaminar deformation. The objective of the paper, therefore, is to develop an efficient general modeling approach for typical laminated CRC capturing fundamental mechanisms of their deformation as well as providing relatively simple and cheap solutions. The approach uses advantages of previously developed methods (Gurvich) to quantify deformation of anisotropic elastomers. The present study is focused on 3D extension of the problem to account for crucially important interlaminar behavior of these composites. Several structural examples illustrate simplicity of implementation, demonstrate computational robustness, and show practical importance of obtained results. In particular, limitations of existing rebar-based models of CRC are shown and explained.
Thermal Oxidation Kinetics of Unvulcanized Unstabilized Polyisoprene
Authors: Colin X. , Audouin L. , Verdu J.
Published: February 2011

The thermal oxidation of an unvulcanized, unstabilized polyisoprene rubber (IR) has been studied in the 40–140 °C temperature range. Ageing was monitored by FTIR determination of double bonds and carbonyl groups, mass uptake measurement, and weight average molar mass determination. A mechanistic scheme based on the standard scheme for radical chain oxidation, but taking into account the diversity of initiation processes and the existence of inter and intramolecular radical additions to double bonds, was built. The kinetic model derived from this scheme is composed of seven differential equations to be solved in discretized thickness layers to take into account the kinetic control by oxygen diffusion. This system was numerically solved using a Matlab program dedicated to stiff systems of differential equations. The elementary rate constants and other kinetic parameters were then determined from experimental data, using an inverse approach. A set of physically reasonable parameter values was obtained, allowing thus to envisage lifetime predictions at low temperature (long term). The results lead to observations difficult to make from classical analytical studies, for instance the predominance of bimolecular hydroperoxide decomposition among other initiation modes or the competition between intermolecular hydrogen abstraction and intramolecular addition of peroxy radicals to double bonds.
Effect of Architecture on the Properties of Polyisobutylene-Based TPE Materials
Authors: Puskas Judit E. , Santos Lucas M. Dos , Sen Mustafa Y. , Kaszas Gabor
Published: February 2011

This paper will discuss the design and synthesis of polyisobutylene-based thermoplastic elastomers (TPEs) for biomedical and other specialty applications. The first generation from this class of polymers, linear triblock polystyrene-b-polyisobutylene-b-polystyrene (PSt-b-PIB-b-PSt or SIBS), is FDA-approved and currently used as the polymeric coating on drug-eluting coronary stents. TPEs with arborescent (dendritic) polyisobutylene core (arbPIB-b-PSt) the third generation, display unique combination of properties. Our latest results include the synthesis of surface-modified TPEs. This paper will give a short overview of the effect of architecture (number of branches, molecular weight and size) on select properties of arbPIB-based TPEs. It will be demonstrated that block copolymers with a high molecular weight dendritic (arborescent) polyisobutylene core and poly(para-methylstyrene) end blocks can manifest themselves either as a rubber, or as a plastic, depending on their environment. The behavior is thermally irreversible. We called this material the “chameleon thermoplastic elastomer.” This material represents a new concept in material science: ETPE (entropy-driven thermoplastic elastomer).
Dynamic Mechanical and Dielectric Properties of Nanocomposites of Natural Rubber (NR), Carboxylated Styrene Butadiene Rubber (XSBR) Latices and their Blends
Authors: Stephen Ranimol , Thomas Sabu , Raju K. V. S. N. , Varghese Siby , Joseph Kuruvilla , Oommen Zachariah
Published: February 2011

The viscoelastic and dielectric properties of nano structured layered silicates reinforced natural rubber (NR), carboxylated styrene butadiene rubber (XSBR) and their blends have been analyzed. The viscoelastic properties such as storage modulus, loss modulus, damping behavior and glass transition temperature of nano filled latices have been investigated. Upon the addition of filler, the storage modulus of nanocomposites was found to increase due to the enhancement in stiffness of the material. Due to the restricted mobility of polymer chain segments, the damping values decreased as a function of filler loading. An investigation of the viscoelastic properties revealed that there was a strong interaction between the polymer and the filler. Latex nanocomposites was characterized by X-ray diffraction technique. The enhanced d values indicated the intercalation of polymer chain into the layers of silicates. The dielectric properties of nanocomposites have been investigated as a function of frequency in the range of 50Hz–100KHz. The effect of frequency on dielectric permittivity (Ε′), dielectric loss (Ε″), dissipation factor (tan δ) and volume resistivity (ρv) of latex nanocomposite have been measured under alternating current. The dielectric permittivity of the samples was found to be higher upon the incorporation of nano fillers. The volume resistivity decreased due to the enhanced conductivity of filled samples.
Nanostructure in Traditional Composites of Natural Rubber and Reinforcing Silica
Authors: Kato Atsushi , Kohjiya Shinzo , Ikeda Yuko
Published: February 2011

Usual rubber products are a composite from rubber and nano-filler (e.g. silica, carbon black, etc.), and it is believed that the good dispersion of the nano-filler is the most important issue determining the performance of rubber vulcanizates. So far, transmission electron microscopy (TEM) has been the most useful tool for evaluation of the dispersion. However, it affords images of the sample projected on an x, y-plane, and the information along the thickness (z-axis) direction is missing. Three-dimensional (3D) visualization of nanometer structure of nano-filler dispersion in a rubber matrix is what all rubber technologists have been dreaming of. This dream is at last realized, and described in this paper. Use of TEM combined with computerized tomography (abbreviated as 3D-TEM in this paper, which is sometimes called electron tomography) enabled us to reconstruct 3D images of nano-filler (silica or carbon black) aggregates in rubbery matrix. It is said that nano-filler aggregate is a structure of size from 10 nm to 1000 nm, and agglomerate is an even larger structure. The 3D-TEM results on silica aggregates in natural rubber were presented in this paper. Silica aggregates were characterized by combining the 3D images of the vulcanizates. Furthermore, density of silica loaded natural rubber as an example of physical properties, was measured, and explained by the structure elucidated by 3D-TEM.
Generalized Concept of the Reinforcement of Elastomers. Part 1: Carbon Black Reinforcement of Rubbers
Authors: Fukahori Yoshihide
Published: February 2011

The author had a detailed discussion about the new interface model and the concepts proposed by the author concerning the carbon black reinforcement of rubbers, with additional experiments and calculations, and came to the final conclusion. Fundamentally, the changeable and deformable characters of the SH layer in the bound rubber produce the typical phenomena in the carbon black-filled rubbers. The super-networks are constructed through the process of molecular sliding and orientation in the SH layer under large extension, which generate the stress upturn and the great tensile strength in the filled rubber. Both the large scale of molecular slippage and the very large stress increase take place simultaneously in the SH layer. The former occurs for regulating the molecular length between carbon particles and the latter results from the limited extensibility of molecules between carbon particles. Thus, the stress-strain relation of the carbon-filled rubber is governed by the distance between adjacent carbon particles, whose role is similar to the molecular length between crosslinks in the non-Gaussian theory. The very large hysteresis loop observed in the carbon black-filled rubber results from the buckling of the super-network in unloading, whose contribution becomes 40% when the carbon content is 60 phr. Very recently, the above model and the concepts have been verified gradually by other researchers as well.
Correlation of Laboratory Tire Endurance and Rubber Aging
Authors: Bauer David R. , Baldwin John M. , Ellwood Kevin R.
Published: February 2011

Tire endurance as measured by performance on the National Highway Traffic Safety Administration (NHTSA) Stepped Up Load (SUL) test is shown to be a function of both tire construction and the extent of oxidation in the skim and wedge rubber regions of the tire, as measured by peel strength or elongation to break retention. Tire constructions can be distinguished by speed rating. Tires with higher speed ratings (> S) tend to have relatively high times-to-failure (TTF) in the SUL test and are relatively insensitive to rubber oxidation. SUL TTFs for tires with speed rating of S and lower tend to be much more sensitive to rubber oxidation. For these tires, the SUL TTF decreases linearly with aging time in the field. The rate of loss of SUL performance is proportional to the rate of loss of rubber properties. The large variability observed in the SUL results from field aged tires can be explained by the natural variability in oxidation aging rates observed for these tires. For oven aged tires, the correlation between SUL and rubber oxidation is more complex. Initially, the SUL failure time does not change much with rubber oxidation. At a critical oxidation level, however, the SUL failure time begins to drop rapidly with rubber oxidation approaching the behavior of the field tires at high levels of oxidation. The reason for the difference in behavior between the oven aged and field aged tires is the lack of mechanical damage in the belt edge in the oven aged tires relative to the field aged tires.
Pulsed NMR Studies on Long-Term Crystallization Behavior and Melting Process of Natural Rubber under Elongation
Authors: Komura Motonori , Nakajima Ken , Nishi Toshio , Ikehara Takayuki , Zhaobin Qiu
Published: February 2011

Long-term crystallization and melting process of natural rubber under elongation was investigated by measuring spin-spin relaxation time T2 by pulsed nuclear magnetic resonance (NMR). We examined the dependence of the both processes on extension ratio, crystallization temperature and crosslink density. It was found that the crystallization of natural rubber continued over three months even at 10 °C. According to the two-step melting process found for the first time under elongation, we proposed a model that crystalline part of natural rubber under large elongation is composed of two kinds of crystallites from highly extended and loose chains. The situation is caused by the microscopic distribution of extension ratio of the chains between crosslink points.
Continuous Ultrasonic Devulcanization: Comparison of Carbon Black Filled Synthetic Isoprene and Natural Rubbers
Authors: Sun Ximei , Isayev A. I.
Published: February 2011

Continuous ultrasonic devulcanization of carbon black (CB) filled isoprene rubber (IR) was carried out. Similar to unfilled IR, power consumption during the devulcanization of the filled IR increased with the increase of ultrasonic amplitude indicating a greater extent of devulcanization. This was in contrast with the devulcanization of CB filled natural rubber (NR) where power consumption showed a maximum at an intermediate amplitude suggesting a lesser extent of devulcanization at higher amplitude. Such a behavior evidently resulted from the difference in the amount of stereoregular structures in the IR and NR rubbers. Gel fraction and crosslink density of the virgin vulcanizates, devulcanizates and revulcanizates were characterized. Kinetics of revulcanization, rheological properties of the devulcanizates and mechanical properties of revulcanizates were compared with those of virgin uncured IR and their vulcanizates. The effect of processing oil on the IR vulcanization, devulcanization and revulcanization was examined indicating a slight delay of the vulcanization and lower torque without affecting the degree of reversion. The addition of oil caused more devulcanization as indicated by an increase in the ultrasonic power consumption and a reduction of the gel fraction and crosslink density of devulcanized rubbers. The revulcanization of the IR occurred without the induction period, regardless of the presence of CB and processing oil. The retarder introduced in the recipe was effective in improving the scorch safety and minimizing the reversion in revulcanization. The experimental data on normalized gel fraction versus crosslink density of filled IR and NR at low CB loadings was found to fall into the master curve, which is probably determined by the main chain structure of both rubbers consisting of cis-1,4 isoprene. At high CB loadings, some differences were observed. The simulation results predicted such a behavior.
High Strength - Low Hardness Thermoplastic Elastomers from Ethylene-Butene Copolymers and Low Density Polyethylene
Authors: Tembhekar Sandeep , Maiti Madhuchhanda , George Jinu Jacob , Biswas Anjan , Bhowmick Anil K. , Saroop Madhumita , Biswas Amit
Published: February 2011

A thermoplastic elastomer (TPE) is a rubbery material with final properties and functional performance similar to those of a conventional vulcanized rubber at ambient temperature, yet it can be processed as a thermoplastic at elevated temperature. The main objective of the present investigation was to prepare novel olefinic thermoplastic elastomers based on blends of a thermoplastic i.e. low density polyethylene (PE) and new ethylene-butene copolymers (PEB), which would have higher strength and lower hardness compared to the existing TPEs. The 70:30 PEB: PE blend exhibited the best properties. Ethylene vinyl acetate was found to work as compatibilizer at lower loadings in these blends. The resultant blends were of low hardness (60–80 Shore A) and high strength (26–33 MPa). The interaction parameter and the morphology of the blends were the key parameters, which governed the final properties of blends.
Thermoreversible Crosslinking of Maleated Ethylene/Propylene Rubber Using Ionic Interactions, Hydrogen Bonding and a Combination Thereof
Authors: van der Mee M. A. J. , Goossens J. G. P. , van Duin M.
Published: February 2011

Maleated ethylene/propylene copolymer (MAn-g-EPM) was thermoreversibly crosslinked using different routes, i.e. ionic interactions (ionomers), hydrogen bonding and a combination thereof. Microphase separation into polar MAn-rich aggregates occurs for MAn-g-EPM and all crosslinked materials, which act as physical crosslinks. The crosslink density does not change upon modification, but the strength of the aggregates is significantly increased, resulting in improved mechanical properties. All materials except the potassium ionomer with high degree of neutralization (DN) could be remolded into homogeneous and smooth films without chemical changes, indicating that the crosslinks are truly thermoreversible. A comparison of the mechanical properties, i.e. tensile properties and compression set at room temperature, for the different crosslinking routes showed that the poorest properties are obtained for hydrogen-bonded materials. The potassium ionomer with high DN has the best properties by far, but is difficult to process. Comparable mechanical properties are obtained for zinc ionomers, potassium ionomers with low DN and amide-salts, which combine ionic interactions and hydrogen bonding. The amide-salts have a distinct advantage in processing over the ionomers, since they can be compression molded at much lower temperatures, although high temperatures should be avoided because of irreversible imide formation.
Goodyear Medalist Lecture: Rubber Research in the Service of Mankind
Authors: Kennedy Joseph P.
Published: February 2011

It all started at the EXXON Research and Engineering Co. during the 1960-ies where I became an apprentice/coworker of Robert M. Thomas (by the way, Thomas (Figure 1) was another Goodyear Medalist honored for the invention and early development of butyl rubber).1
Mesoscopic Mechanical Analysis of Filled Elastomer with 3D-Finite Element Analysis and Transmission Electron Microtomography
Authors: Akutagawa Keizo , Yamaguchi Ken , Yamamoto Atsushi , Heguri Hisashi , Jinnai Hiroshi , Shinbori Yuki
Published: February 2011

Analysis of deformation of the filled elastomer in mesoscopic scale was investigated with 3-D FEM (Finite Element Analysis). Combination of 3-D TEMT (Transmission Electron Micro Tomography) and Voxel-FEM enables us to reconstruct mesoscopic scale 3-D image and calculate 3-D strain distribution. To the first approximation, the calculated stress-strain behavior shows a good agreement with the experimental results. The strain concentration over 200% can be seen between carbon black aggregates, even if the overall strain is only 15%. The rubber occluded by carbon black aggregates can also be observed. The virtual rubber model constructed with perfectly dispersed fillers was also calculated. This shows less overall stress than that of the actual filled model reconstructed with 3-D TEMT image. It is found that the occluded rubber can behave as a hard domain and is an important factor of the filler reinforcement effect on rubber.
A Mechanistic Approach to EPDM Devulcanization
Authors: Dijkhuis K. A. J. , Babu I. , Lopulissa J. S. , Noordermeer J. W. M. , Dierkes W. K.
Published: February 2011

The extensive utilization of rubber in a wide variety of products causes a problem in terms of waste. Reclaiming of end-of-life products or production scrap is a potential solution. A high quality reclaim would preferably be obtained by devulcanization, to leave the polymer chains intact. Reclaiming of natural rubber is common practice, although the fundamental knowledge about de- and re-crosslinking is rather limited. EPDM-based rubber is even more unexplored in terms of reclaiming and re-utilization. This paper gives a mechanistic insight into the thermal reclaiming of two differently vulcanized EPDM compounds, using hexadecylamine (HDA) as devulcanization agent. Reclaim from conventionally vulcanized EPDM, mainly polysulfidic of nature, shows the largest decrease in remaining crosslink density with increasing HDA concentration and at lower reclaim temperatures. After reclaiming at the lower limit of the experimental temperature window applied: 225 °C, the concentration of remaining di- and polysulfidic crosslinks is higher than the concentration of monosulfidic bonds, while at the upper temperature level: 275 °C, the concentration of monosulfidic bonds is highest. For efficiently vulcanized EPDM with primarily monosulfidic crosslinks, HDA again has a positive effect on the reclaim efficiency at low applied reclaiming temperatures of max. 225 °C. At higher temperatures, the crosslink density increases with increasing concentrations of HDA. Application of a treatment proposed by Horikx shows, that conventionally vulcanized EPDM devulcanizes to a larger extent by crosslink scission compared to the efficiently vulcanized material, which primarily shows main-chain scission. Both reclaimed materials can be added up to 50 wt% to a virgin masterbatch, with limited decrease in properties. This is a high amount compared to max. 15 wt% of ground powder rubber, commonly known to be the practical limit.
Improvements in the Hydrogenation of Nitrile Rubber Using Wilkinson's Catalyst
Authors: McManus N. T. , Rempel G. L.
Published: February 2011

RhCl(PPh3)3 is an efficient catalyst precursor for the selective hydrogenation of C=C in acrylonitrile butadiene rubber(“nitrile rubber”, NBR). The established technology for the process using RhCl(PPh3)3 is to carry out reaction in the presence of a large excess of triphenylphosphine (PPh3), with monochlorobenzene (MCB) as solvent. In parallel with the hydrogenation of unsaturation in the rubber there is a side reaction involving the MCB, which produces benzene. This likely occurs via oxidative addition of the C-Cl bond in the monochlorobenzene to a Rh intermediate in the catalytic cycle for hydrogenation, followed by reductive elimination of benzene in conjunction with H2 addition to the Rh centre. This leads to formation of less active Rh intermediates which lead to rapid deterioration of catalytic activity in the absence of excess PPh3. It was postulated that some of the PPh3 in solution acts as a base that “mops up” excess HCl formed as a by product of the catalytic cycle. Supporting evidence comes from a novel improvement of the hydrogenation process, where the deactivation of catalyst, can be offset by the presence of bases, such as amines and metal oxides (as an alternative to adding a large excess of PPh3). This modification can improve catalyst activity with respect to levels of Rh used, or could be used to minimize the level of added co-catalysts needed to maintain useful rates of hydrogenation.
Heat Aging Behavior of Novel Poly (Phenylene-Ether) Based Thermoplastic Elastomers
Authors: Gupta Samik , Kamalakaran Radha , Maldikar Avdhut , Menon Ashok , Bhowmick Anil K.
Published: February 2011

The heat aging performance of a series of novel poly (phenylene ether) (PPE) based thermoplastic elastomers (TPEs) from styrene-ethylene-butylene-styrene (SEBS), ethylene vinyl acetate (EVA) and PPE-polystyrene (PS), was studied. This quaternary blend showed superior heat aging performance due to the high Tg thermoplastic component (PPE). At 80 °C, different compositions of the quaternary blends were exposed for 500 hours. Effects of compositions, vinyl acetate (VA) content of EVA and different molecular weights (MW) of SEBS, on the mechanical properties upon heat aging were analyzed in detail. A representative composition (based on the mechanical properties) of the quaternary blend (SEBS/EVA/PPE-PS: 45/30/25) was exposed at different temperatures, i.e. 80 °C, 120 °C, 140 °C and 170 °C, for 2000 hours. Thermal degradation profiles of change in tensile strength and percent elongation at break due to thermal degradation of the blends were monitored and “half-life” temperature was estimated. Using the Arrhenius equation, the “lifetime” of the quaternary blend was predicted (100,000 hours at ∼131 °C). Change in functionalities due to chemical degradation was also monitored using Fourier Transform Infrared Spectroscopy (FTIR). As a consequence of degradation, the shift in Tg was observed by temperature modulated DSC (Differential Scanning Calorimeter). Detailed microstructural studies were done to establish the structure-property correlation, for degraded as well as pristine materials. The degradation mechanism was elucidated on the basis of morphology and structure studies of the blends.
Effect of Plasma Polymerization on the Performance of Silica in NBR, EPDM and NBR/EPDM Blends
Authors: Tiwari M. , Noordermeer J. W. M. , Dierkes W. K. , van Ooij Wim J.
Published: February 2011

The surface modification of precipitated silica powders by plasma-polymerization with acetylene monomer in order to improve their performance in NBR, EPDM and NBR/EPDM rubber blends, by matching the surface energies of the silica fillers of the rubbers, is the subject of this study. Silica, used as reinforcing filler for elastomers, is coated with a polyacetylene (PA) film and characterized by water penetration measurements, Cetyltrimethyl Ammonium Bromide (CTAB) area, Thermo Gravimetric Analysis (TGA), Time of Flight-Secondary Ion Mass Spectroscopy (ToF-SIMS) and Scanning Electron Microscopy with elemental analysis by Energy Dispersive X-ray spectroscopy (SEM/EDX). All techniques show the evidence of a PA-film deposition on the surface of silica. The properties of NBR, EPDM and blends based on NBR and EPDM, filled with untreated, PA- and silane-treated silica, are investigated by measurement of the Payne effect, the bound rubber content and weight loss related to bound rubber, the reinforcement parameter and mechanical properties. The PA-silica filled samples show a lower Payne effect for EPDM and NBR/EPDM compared to the rubbers filled with unmodified silica. However, PA-silica filled NBR shows a higher Payne effect. This indicates an improved filler dispersion in the EPDM and NBR/EPDM, and a poorer dispersion in the NBR. The reduction of the reinforcement parameter as found for NBR, EPDM and NBR/EPDM indicates a lower degree of agglomeration in comparison with untreated and silane-treated silica. The PA-silica filled samples show the highest bound rubber contents and “in-rubber structure” for both rubbers as well as for the blend, compared to both other silica samples. The mechanical properties of untreated silica filled blend of NBR/EPDM are worse compared to the pure rubbers, but acetylene polymerization onto silica results in a significant improvement relative to the unmodified silica. The combined effects all point in the direction of improved compatibility of the PA-silica with the apolar EPDM. This results in better dispersion and stronger interaction with the EPDM, particularly in the blend with NBR, so as to significantly improve the mechanical properties of the blend relative to the use of untreated or silane-treated silica.
Correlation between Physico-Mechanical Properties of NR-BR Blends in Tire Tread Formulation with their Thermal Behaviors
Authors: Taghvaei-Ganjali Saeed , Motiee Fereshteh , Fotoohi Farsa
Published: February 2011

Thermal analysis provides a successful technique for the characterization and identification of rubber compounds. In this study, TGA (thermogravimetric analysis) and DTG (TGA derivative) profiles are used to predict and define the physico-mechanical properties of natural rubber — butadiene rubber (NR / BR) blends, using their thermal behaviors. DTG curves of vulcanizate showed that the initial degradation temperature of NR is lower than BR. According to TGA-DTG profiles we have demonstrated two useful factors, ΔTmax (Tmax BR100−Tmax BRX) and peak height ratio of NR-BR blends which are correlated with physico-mechanical properties of blends.