bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the Non-Linear Viscoelastic Behavior of Filled Rubber Compounds Through Fourier Transform Rheometry
Authors: Leblanc Jean L.
Published: February 2011

Fourier transform (FT) rheometry was used to investigate the non-linear viscoelastic behavior of a series of carbon black filled rubber compounds with various filler levels. Using a purposely modified commercial dynamic rheometer, i.e. the Rubber Process Analyzer RPA 2000® (Alpha Technologies), special strain sweep tests protocols were designed and performed in order to capture the actual strain and torque signals up to 500% deformation at constant frequency and temperature. FT yielded the main component and harmonics of strain and torque signals. Results show that the quality of the applied strain signal somewhat deteriorates with increasing stiffness of filled compounds, but remains excellent in the high strain region, where the non-linear viscoelastic response of the materials is investigated. Above a filler volume fraction of around 12–13%, tested materials no longer exhibit a linear viscoelastic response, at least in the strain window investigated, and the FT rheometry results are more complex than what was observed with pure gum samples. This means that most practical rubber compounds are intrinsically non-linear. By essence, FT rheometry is a valid technique for both the linear and the non-linear domains and, as shown, provides original information about complex polymer systems such as filled rubber compounds.
Effect of Compound Ingredients on Adhesion between Rubber and Brass-Plated Steel Cord
Authors: Hotaka Takeshi , Ishikawa Yasuhiro , Mori Kunio
Published: February 2011

Effect of several ingredients in the rubber on adhesion characteristics between brass-plated steel cord and rubber was thoroughly investigated. Amine component is generated by N,N'-dicyclohexylbenzothiazole-sulphenamide- (DCBS) accelerated sulfur vulcanization, and it is known to promote stress-induced corrosion crack in the brass layer at the brass plated steel cord. Hexamethoxymethylmelamine (HMMM), which is formulated for the condensation reaction of RF resin, has a function to trap amines, which was found to effectively improve the adhesive strength in water-aged degradation. It was clarified that the physical properties of the vulcanized rubber such as crosslink density and strain modulus are also improved by trapping the residual amine accompanying improved adhesive strength for the formulation with HMMM. Influence of carbon black on concentration of the residual amine and adhesive strength was also studied. Amount of the amine was inversely proportional to the carbon gel content, while adhesive strength linearly increased with the level of carbon gel. It was assumed that the carbon black dose enhances the adhesive strength due to a preferential entrapment of the amine at the stage of carbon gel formation.
Rubber/Fiber Interactions During the Tearing of Rubber Coated Polyester Fabrics
Authors: Tao Z. , Chen J. , Stacer R. G. , Mead J. L.
Published: February 2011

Results on the characterization of the tearing behavior of a series of uncoated and butyl rubber coated polyester plain weave fabrics are reported. Polyester fabrics were obtained from commercial source to cover a broad range of fill yarn properties. Dip coating was used to obtain coated fabrics. Data indicates that the tear behavior of this composite system can be analyzed in terms of initiation and arrest loads, stiffness, and number of yarns per peak. Results show that yarn mobility and subsequent del zone structure play a critical role in each of these characteristics.
A Contribution to the Understanding of Elementary Wear Mechanisms of Rubber Filled Compounds
Authors: Petitet G. , Loubet J-L. , Zahouani H. , Mazuyer D.
Published: February 2011

Tire rubber treads wear patterns that are described as craters can appear in mild conditions. This article demonstrates that craters can be recreated on a laboratory tribometer, which has been developed especially for rubber filled compounds testing. A local analysis of the worn surfaces has shown that the dimension, density and location of craters are closely related to carbon black agglomerates found within compounds. The viscoelastic properties of the agglomerates have been found by carrying out nanoindentation tests: these give a Young's modulus of around 300 MPa and a elasto-plastic limit between 7% and 14%. Finally, an original system is proposed to explain the crater formation on the release of internal stresses due to an agglomerate mechanical plasticizing of the rubber surface. Electronic microscope observations and a finite element analysis show that the agglomerates are flattened by the indentor contact and tilted, to create craters on the worn surface.
Modeling the Stress-Strain Behavior of Rubber
Authors: Muhr A. H.
Published: February 2011

This review focuses on models for rubber that have been used to solve practical problems, either analytically or through the use of finite element analysis (FEA). The emphasis is on the mathematical structure of fully three dimensional models and the scope of behavior that they describe. The mechanisms that are responsible for the behavior are referred to in passing, and prominence is given to models with firm mechanistic foundations. The review starts with definitions of stress and of measures of deformation, and shows how even the simplest model, classical elasticity theory with appropriate values of shear and bulk moduli, gives useful analytical expressions for many products. Viscoelasticity and hyperelasticity are briefly discussed, as well as the more recently introduced models for inelastic effects, notably the Mullins and Payne (or Fletcher-Gent) effects. Some phenomena not yet addressed by models implemented in commercial FEA packages, such as set, cyclic creep and cyclic stress relaxation, are mentioned, and indications of emerging approaches to modeling them are given.
Recent Developments in Crosslinking of Elastomers
Authors: Aprem Abi Santhosh , Joseph Kuruvilla , Thomas Sabu
Published: February 2011

The recent developments in the vulcanization of elastomers, major types of crosslinking, and mechanism of crosslinking have been reviewed. Attention has been made to sum up the accelerated vulcanization. Possible mechanisms by which the reaction is taking place are discussed. The role of accelerators, activators, and fillers has been described. The different types of crosslinks and importance of each type on the specific properties of the resulting vulcanizates, etc., are discussed. Various aspects of vulcanization like model compound vulcanization, nitrosamine generation, etc., are discussed. The importance of binary accelerators and possible mechanism of their action have been mentioned. The method of double network formation, which is useful for the improvement in properties, is also described. The different methods for characterization of networks and different methods for estimating crosslink densities are also explained.
Heat Resistant Elastomers
Authors: Tao Zhenghong , Viriyabanthorn Nantiya , Ghumman Bhavjit , Barry Carol , Mead Joey
Published: February 2011

This paper reviews the different types of heat resistant elastomers and the effects of compounding on the high temperature performance of these materials. Degradation mechanisms and testing procedures are discussed briefly. New developments in improving high temperature resistance are presented.
Elastomers: A Literature Review with Emphasis on Oil Resistance
Authors: Patil Abhimanyu O. , Coolbaugh Thomas S.
Published: February 2011

There has been a long-standing commercial desire for elastomers with a high degree of oil-resistance. For example, oil-resistant materials are very important to the automotive industry since a variety of components may come into contact with a number of fluids (hydrocarbon and otherwise). In the specific case of engine seals, it is important that they be able to withstand the fluids they are sealing without losing their ability to maintain the seal either by becoming too soft or too brittle. This review summarizes some of the advantages and limitations of commercial elastomers with special emphasis on their oil-resistant character (or lack thereof). It also discusses the synthesis and the key molecular features (e.g., glass transition temperature, solubility parameter, effect of structures on oil-swell and percent swelling of elastomers vs various solvents) required for oil-resistant applications.
Finite Element Method for the Study of Belt Edge Delaminations in Truck Tires
Authors: Özüpek Şebnem , Becker Eric B.
Published: February 2011

In this study, we develop a computational procedure to predict the initiation and growth of belt layer separations in pneumatic tires. The procedure consists of finite element modeling and analysis of a tire subject to steady state rolling conditions. First, a global analysis that uses a full tire model is performed. Then, critical regions for crack initiation are determined through local analysis around the belt edges. This is followed by the placement of an initial crack in a local model. A sequence of crack configurations is analyzed and tearing energies at various crack sizes are calculated as part of the fatigue crack growth simulation. The final desired result is the prediction of fatigue life of the tire.
Model Compound Studies on the Devulcanization of Natural Rubber Using 2,3-Dimethyl-2-Butene
Authors: Rajan V. V. , Dierkes W. K. , Noordermeer J. W. M. , Joseph R.
Published: February 2011

The mechanism of devulcanization of sulfur-vulcanized natural rubber with aromatic disulfides and aliphatic amines has been studied using 2,3-dimethyl-2-butene (C6H12) as a low-molecular weight model compound. First C6H12 was vulcanized with a mixture of sulfur, zinc stearate and N-cyclohexyl-2-benzothiazylsulfenamide (CBS) as accelerator at 140 °C, resulting in a mixture of addition products (C6H11−Sx−C6H11). The compounds were isolated and identified by High Performance Liquid Chromatography (HPLC) with respect to their various sulfur ranks. In a second stage, the vulcanized products were devulcanized using the agents mentioned above at 200 °C. The kinetics and chemistry of the breakdown of the sulfur-bridges were monitored. Both devulcanization agents decompose sulfidic vulcanization products with sulfur ranks equal or higher than 3 quite effectively and with comparable speed. Diphenyldisulfide as devulcanization agent gives rise to a high amount of mono- and disulfidic compounds formed during the devulcanization, hexadecylamine, as devulcanization agent, prevents these lower sulfur ranks from being formed.
Grafting of Norbornene Diacid Anhydride Onto Fluoroelastomer
Authors: Xiong Chuanxi , Chen Chunming , Niu Yongsheng , Tian Demei
Published: February 2011

Grafting of norbornene diacid anhydride (NA) onto fluoroelastomer (FPM) has been studied using a Brabender Plasticorder in the presence of dicumyl peroxide (DCP). The concentrations of NA and DCP were varied from 0 to 10.0 wt% and from 0.1 to 1.0 wt% respectively. The grafting quantities and crosslinking degree (gel content) of the grafting FPM (FPM-g-NA) were determined by acetone extraction and a back-titration procedure. The results showed that maximum NA grafting can be reached 5.5 wt% by using a relatively low peroxide concentration (0.4 wt%) and NA content (10 wt%). The characteristic groups of norbornene diacid anhydride in the grafted products were measured by Fourier transform infrared spectroscopy (FTIR), and thermal property of the FPM-g-NA was studied. The results showed that norbornene diacid anhydride had grafted onto fluoroelastomer.
Reactions of Radicals in Filled Rubber Compounds: I. Detection of Free Radicals in Rubbers by ESR
Authors: Kawakubo Makoto , Tsunoda Katsunori , Yajima Hirofumi , Ishii Tadahiro , Kaidou Hiroyuki , Ahagon Asahiro
Published: February 2011

ESR measurements were made with vulcanized rubbers of a gum, three carbon black filled and a silica filled compounds. The radicals in the filled rubbers were found to have long lives unlike the gum rubber. Carbon black was found to reduce the sensitivity of ESR due to shielding effect in the magnetic field. The degree of sensitivity reduction appeared to depend on the inter-aggregate distance. Upon exposure to toluene vapor, the ESR intensity of black filled rubbers increased for a short period as swelling widened the inter-aggregate distance and then decayed steadily with further exposure. Such a variation was not found with the gum and silica filled vulcanizates. The decay was faster with higher oxygen content of the environment. In a given environment, however, the decay could be dealt by simple kinetics. Diffusion of oxygen did not seem to play any part. It was inferred that ESR observes radicals only in a thin surface layer of the black filled rubber. The kinetic zero-time radical concentration, obtained by toluene vapor exposure in a nitrogen environment, was considered to be the surface radical concentration in the absence of the shielding effect. Among the rubbers of different black loadings, it showed an exponential relation with the value obtained by direct observation due to the difference in the shielding effect arising from difference in loadings. With the rubber of the same formulation, however, the radical concentration obtained by direct observation showed a linear relation with the kinetic zero-time value, suggesting possibility of quantitative comparison by ESR among the rubbers with the same carbon black content.
Release of Dithiocarbamates into Sweat from Natural Rubber Latex Surgical Gloves
Authors: Abraham Elizabeth K. , Ramesh P. , Joseph R. , Mohanan P. V. , Remakumari V. M.
Published: February 2011

The release of zinc dialkyldithiocarbamates from a batch of surgical gloves into the sweat of human subjects was studied. Healthy volunteers from both sexes were asked to don the gloves on both hands for 1 h. The identification and estimation of dithiocarbamate residues released into the sweat were carried out using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). The thin layer chromatogram showed that zinc diethyldithiocarbamate (ZDEC) accelerator residues were released into the sweat of volunteers. The estimation by high performance liquid chromatography revealed that the amount of ZDEC released varied among the human subjects despite using the same brand of glove. The effect of sweat rate and pH on the amount of ZDEC released into hand sweat was investigated. The results indicated that it may not be possible to derive a relationship between the sweat-extractable ZDEC and sweat rate or pH of hand sweat. The dithiocarbamate release was studied in the laboratory using a physiologically simulated medium, namely, artificial sweat at different pH levels. The glove was filled with artificial sweat and extracted for 1 h at 37 °C. It was found that amount of artificial sweat-extractable ZDEC varied with changes in pH of artificial sweat. Lack of a clear relationship between the sweat-extractable ZDEC and sweat rate or pH of hand sweat indicated that factors such as hand exercise, glove-fit, etc., may also be considered when simulating actual use conditions in vitro.
Comparative Polymerization Activity of EPM and EPDM Using VCI4 Homogenous Ziegler-Natta Catalyst and Characterization of EPDM Obtained
Authors: Zohuri G. H. , Vakili M. , Jamjah R. , Ahmadjo S. , Nekomanesh M.
Published: February 2011

Copolymerization of ethylene/propylene (EPM) and terpolymerization of ethylene/propylene/5-ethylidene-2-nor-bornene (ENB) were carried out using VCl4 based Ziegler-Natta catalyst. Triisobutylaluminum (TIBA) was used as a cocatalyst while CHCl3 and CCl4 were used as promoters. Effects of [Al]/[V] ratio, temperature, promoters and ENB concentration, relative pressure of P/E, H2 concentration and polymerization time on polymerization behavior were studied. The highest productivity of the catalyst was obtained at [Al]/[V] ratio of 8–10. Increasing the [Al]/[V] ratio increased Et% and Tg and decreased ENB% of the EPDM (ethylene / propylene / diene) obtained. Activity of the catalyst system was higher for EPM than EPDM. ENB concentration affected polymer yield. Increasing ENB from 5 ml/Lit solvent to 10 ml /Lit solvent increased productivity of the catalyst; however, higher concentration decreased the EPDM polymer yield. Addition of ENB increased Et% of the EPDM. Polymerization of EPDM was carried out at temperatures of 25 °C to 75 °C. The highest productivity was obtained at ∼ 50 °C. At reaction temperature of ∼ 55 °C, Et% and ENB% were 65.5% and 9%, respectively. Rp/time profiles were decay types for both EPM and EPDM production. Et% of EPDM increased with polymerization time, while an inverse result was obtained for ENB%. Addition of CHCl3 to 3 ml /lit solvent increased productivity of the catalyst. However, addition of CCl4 did not have such effect on the yield of the polymer obtained. Effect of relative pressure of P/E=1.25:1 to 0.89:1 on EPDM polymerization was studied. Addition of ethylene relative pressure increased Et% and increased Tg of the EPDM obtained. The lowest Tg of the EPDM obtained was −39 °C. A compound made with the EPDM showed good thermal stability.
Relationship between Particle Size and Molecular Weight of Rubber from Hevea Brasiliensis
Authors: Tarachiwin Lucksanaporn , Sakdapipanich Jitladda T. , Tanaka Yasuyuki
Published: February 2011

Rubber particles with different mean diameters obtained from fresh natural rubber latex (FL-latex) were separated by high-speed centrifugation. The small rubber particles (SRP), having mean diameter less than 250 nm, were found to be composed of both low and high number-average molecular-weight (Mn) rubber molecules; while larger rubber particles (LRP), with mean diameter larger than 250 nm, mainly consisted of low Mn rubber molecules. The content of longchain fatty acid ester are mainly due to functional groups such as phospholipids were less in SRP than that of LRP. This indicates clearly that LRP contains mainly rubber molecules which were terminated to form a functional terminal group containing fatty acid ester groups. The high molecular-weight rubber in SRP, containing lower amounts of ester groups, is presumed to be mainly linear molecules having no chain-end group to form branch-points. On the other hand, the low molecular-weight rubber molecules with high ester content in the LRP are presumably terminated with the functional group containing fatty acid esters to form long-chain branching. The molecular-weight of rubber in LRP increased with increasing particle sizes. This suggests that the LRP was derived from the aggregation and/or association of functional groups at ω- and α-terminal end groups.
The Effect of Cure Conditions on the Strength of Ebonite Rubber Network
Authors: Pattamaprom Cattaleeya , Dechojarassri Duangkamol , Kanok-Nukulchai Worsak
Published: February 2011

Although ebonite has been discovered for a long time, its applications were still limited to some household products. Recently, ebonite rubber has become of interest, especially for structural applications due to its high and adjustable strength and rigidity. The rigidity can be enhanced by several folds by utilizing appropriate curing conditions. In this study, we investigate the effect of curing conditions on the mechanical properties of ebonite at various cure time. Here, the crosslink densities were determined qualitatively both before and after compression cycles to investigate the change in crosslink networks. After the pre-molding stage, the curing process was either continued in the compression mold, in the air-oven, or under nitrogen atmosphere. For the compression-mold and nitrogen-atmosphere curing, crosslink densities and the compressive moduli increased significantly with cure time, whereas, for air-oven curing, only slight increases in the afro-mentioned properties were observed. After completing four compression cycles, the crosslink density and mechanical properties remain high only when curing was done in the compression mold. Therefore, curing under pressure as in the compression mold for a prolonged time could be a mean in boosting the mechanical properties of ebonite.
Structure — Property Behavior of New Segmented Polyurethanes and Polyureas Without Use of Chain Extenders
Authors: Klinedinst Derek B. , Yilgör Emel , Yilgör Iskender , Beyer Frederick L. , Sheth Jignesh P. , Wilkes Garth L.
Published: February 2011

New novel segmented polyurethane and polyurea copolymers have been synthesized without chain extenders and the structure-property behavior of these systems has been investigated. It is shown that by the proper choice of diisocyanate and its symmetry, one can obtain highly microphase separated systems without chain extenders and that the materials also display useful mechanical behavior. In particular, it is shown that due to the bidentate hydrogen bonding achieved in the segmented ureas, a significant modulus “service temperature window” is also obtained. It is also verified that not only can strong microphase separation be obtained with low weight fraction hard segment content (14%) but that the hard phase, which is comprised of monodisperse “single molecule” units, also displays a percolated thread-like structure throughout the dominant soft segment material — the latter being based on ca. 1000g/mol polytetramethylene oxide.
Accelerated Aging of Tires, Part III
Authors: Baldwin John M. , Bauer David R. , Ellwood Kevin R.
Published: February 2011

The purpose of this research is to determine the conditions whereby a new tire can be artificially aged in an accelerated manner, in order to duplicate the actual mechanism of chemical aging observed in field-aged tires. The ultimate goal of the study is to age tires to a desired level, say equivalent to 4 years old, and then test the tires in durability, high speed, and performance tests. The previous paper described various oven aging methodologies and the data analysis techniques used. This paper will build on the previously described data analysis techniques developed for elongation at break measurements and apply them to swelling ratio data and peel strength data. By utilizing the method initially developed by Gillen and modified by this laboratory for use with tires, it has been shown that the skim rubber of tires oxidatively ages at oven temperatures between 40 °C and 70 °C when mounted and inflated with either air or a blend of 50/50 N2/O2. The methodology has been successfully extended from elongation at break data to peel strength and swelling ratio data. The calculation of the Arrhenius activation energy for diffusion of oxygen through new and aged rubber was also determined. The effect of aging on permeability is to reduce the permeability of oxygen and increase the activation energy. These results have important implications when attempting to model the diffusional aging characteristics of inflated tires. The effect of changing the partial pressure of oxygen and its concomitant effect on the acceleration of aging was also investigated. The results indicate that by doubling the partial pressure of oxygen, the rate of oxidation is increased by approximately 1.5 times. This result is entirely consistent with the theory of diffusion limited oxidation.
Correlation of Rubber Properties between Field Aged Tires and Laboratory Aged Tires
Authors: Bauer David R. , Baldwin John M. , Ellwood Kevin R.
Published: February 2011

The kinetics of aging of key tire properties both in the field and in oven exposures at different temperatures has been interpreted by using a combination of empirical models and accelerated shift factors. Crosslink density and rubber modulus increase with aging while peel strength and elongation-to-break decrease. In the case of oven aging, the rate of property change increases from 40 °C to 70 °C and then decreases. In the case of field aging, the rate of property change is greatest in hotter climates such as Phoenix and is slower in cooler climates such as Detroit. Spare tires age at a rate that is ∼70% as fast as on-road tires. Below 70 °C, the rate data for all of the aging changes can be fit to an Arrenhius relationship with an activation energy of ∼69 kJ/mole, a value that is consistent with the aging process resulting from diffusion limited oxidation. The measured acceleration factor of oven aging at 70 °C relative to on-road aging in Phoenix is independent of the property change measured confirming that it is possible to chemically age tires in ovens. It takes 6–7 weeks of oven aging at 70 °C to produce a tire that is aged 4 years in Phoenix. Field results show that the rate of tire aging varies by over a factor of 5 for the different tire types and brands studied in this work. The implications for tire durability testing are discussed.
Reinforcement of Natural Rubber with Silanized Precipitated Silica Nanofiller
Authors: Ansarifar A. , Ibrahim N. , Bennett M.
Published: February 2011

The effect of a large amount of precipitated amorphous white silica nanofiller, pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT), on the mechanical properties of a sulfur-cured natural rubber (NR) was studied. TESPT chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur-cure. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulfur in TESPT, or, by adding a small amount of elemental sulfur to the cure system. The cure was also optimized by incorporating sulphenamide accelerator and zinc oxide into the rubber. The hardness, tear strength, tensile strength, and stored energy density at break of the vulcanizate were substantially improved when the filler was added. Interestingly, these properties were also enhanced when the rubber was cured primarily by using sulfur in TESPT.
Rheological Behavior of Hybrid Rubber Nanocomposites
Authors: Bandyopadhyay Abhijit , De Sarkar Mousumi , Bhowmick Anil K.
Published: February 2011

Melt rheological behavior of acrylic rubber (ACM)/ silica and epoxidized natural rubber (ENR)/ silica hybrid nanocomposites prepared by using sol-gel technique at room temperature was studied for the first time in a Monsanto Processability Tester (capillary rheometer) at nine different shear rates and three different temperatures (100 °C, 110 °C and 120 °C). Tetraethoxysilane (TEOS) was used as the precursor for silica, and water to TEOS mole ratio was maintained at 2:1 throughout the experiments. The loading of TEOS was 10, 30 and 50 wt% with respect to the rubber and the pH of the medium was maintained in the range of 1.0–2.0 by the addition of appropriate amount of concentrated HCl. The shear viscosity showed marginal increment even at higher nanosilica loading for the rubber/ silica nanocomposites. All the compositions displayed pseudoplastic behavior and obeyed Power Law model within the experimental conditions. The reinforcement factor (RF) calculated from the ratio of the viscosities of the filled and the unfilled systems was found to increase with nanosilica content at a particular shear rate. ENR/ silica nanocomposites displayed higher increment of RF compared to ACM/ silica system, which may be due to better polymer-filler interaction in the former. The RF remained almost constant for both the systems with the variation of temperature. The die swell of the nanocomposites was always lower than that of the gum rubber sample, though the nature of variation of die swell with shear rates was different for ACM and ENR nanocomposites. In both the cases, the die swell was found to decease with increase in temperature. The variation in activation energy with the experimental shear rates was also calculated, where the hybrids displayed a decreasing trend in activation energy with the increase in shear rate.
Analysis of Melting Point Depression of Benzene in Crosslinked Natural Rubber by a Frozen Tube Network Model
Authors: Hoei Y.
Published: February 2011

Literature reports from studies by Jackson and McKenna show a large difference in melting point depression between highly and lightly crosslinked (concentrated) natural rubber/benzene samples. Here, an equation for a tube model is developed to describe particularly the highly crosslinked mixtures at both swelling-and-melting equilibrium. On the basis of Flory-Huggins and Gibbs-Thomson equations, the model involves a swelling-and-melting thermodynamics that includes an elastic contribution to a free energy for a “real chain” network swollen in a good solvent. The freezing of the good solvent, then, occurs within the network chains which act as a confining (frozen) hard tube (having an unfrozen good solvent within). Consequently, the model can explain reasonably well the melting point depression of the highly crosslinked samples in the comparison of their estimates for crystallite (frozen tube) dimensions with certain corresponding literature values.
Biodegradable Protein-Containing Elastomeric Vulcanizates
Authors: Przepiórkowska A. , Prochoń M. , Zaborski M. , Żakowska Z. , Piotrowska M.
Published: February 2011

The effects of leather powders, chrome tanned leather powders and keratin were studied on properties of the synthetic isoprene rubber IR and the microbiological decomposition of the resulting proteinous-elastomeric composites. The proteins were obtained from the waste of the leather industry. The incorporation of proteins into the mixes of synthetic 1,4-cis-polyisoprene provides increased recaptivities to microbiological decomposition.
A Novel Planar Tension Test of Rubber for Evaluating the Prediction Ability of the Modified Eight-Chain Model under Moderate Finite Deformation
Authors: Xia Yong , Dong Yi , Xia Yuanming , Li Wei
Published: February 2011

In this paper, a novel planar tension test is applied to evaluate the prediction ability of the rubber constitutive models under moderate finite deformation. Based on the automated grid method, it is found that in planar test, deformation in the center region of the specimen is homogeneous but that of the whole specimen is heterogeneous. With three dimensional (3D) finite element (FE) modeling, both the load-stretch relationship and the deformation fields predicted by various constitutive models are obtained under heterogeneous deformation state of the planar tension. By comparing FEA results to the test results, the prediction abilities of these constitutive models are evaluated. According to the results of this heterogeneous planar tension test, the modified eight-chain model is found to be more successful than the eight-chain model and the Van del Waals model in predicting the observed hyperelastic behaviors of rubber material under different deformation states.
Novel Styrenic Thermoplastic Elastomers from Blends with Special Reference to Compatibilization and Dynamic Vulcanization
Authors: Patel J. D. , Maiti M. , Naskar K. , Bhowmick Anil K.
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 in a molten condition as a thermoplastic polymer at elevated temperature. The main objectives of the present investigation are: to prepare novel styrenic-based thermoplastic elastomers based on blends of a thermoplastic (polystyrene or styrene acrylonitrile) with a rubber (styrene butadiene or ethylene vinylacetate) and to investigate the interaction between various polymers with special reference to compatibilization via oxazoline-modified polystyrene or oxazoline-modified styrene acrylonitrile and dynamic vulcanization. Styrene acrylonitrile/ethylene vinylacetate blends are found to exhibit better overall properties, especially tensile strength, elongation at break and tension set. The solubility or interaction parameter and the morphology of the blends are the key parameters, which basically govern the final properties of blends. Physical properties of these blends have been correlated with the interaction parameter and final morphology.
Phenomenological Hyperelastic Strain-Stiffening Constitutive Models for Rubber
Authors: Horgan Cornelius O. , Saccomandi Giuseppe
Published: February 2011

Many rubber-like materials and soft biological tissues exhibit a significant stiffening or hardening in their stress-strain curves at large strains. The accurate modeling of this phenomenon is a key issue for a better understanding of the thermomechanics of rubber and the biomechanics of soft tissues. In this paper, we provide a review of some phenomenological hyperelastic constitutive models that have been proposed to model this strain stiffening effect and summarize recent advances in the solution of boundary-value problems that illustrate the utility of such models. The emphasis is on constitutive models that reflect limiting chain extensibility at the molecular level. A remarkably simple phenomenological model of this type has been proposed by Gent. The Gent model has a molecular basis related to the inverse Langevin function compact support non-Gaussian statistics for the end-to-end distance function. The mathematical simplicity of the Gent model, which contains just two constitutive parameters, has facilitated the analytic solution of a variety of specific boundary-value problems that are relevant to the rubber industry and we summarize the main results here. These problems include those of torsion, axial, azimuthal and helical shear, anti-plane shear, mode III crack problems, rotation induced deformation of circular cylinders and fracture problems. It is shown that the results are radically different from those obtained in the literature for classical models such as the neo-Hookean and Mooney-Rivlin models for incompressible rubber. Extensions to include thermoelasticity, material compressibility, anisotropy and stress softening are also briefly described.
The Hysteresis Temperature and Strain Dependences in Filled Rubbers
Authors: Scurati Alberto , Lin Chenchy J.
Published: February 2011

The strong hysteresis (tan δ) temperature dependence observed in filled compounds containing functional polymers was investigated by studying the individual effect of filler-filler (F-F) and polymer-filler interactions (P-F). Silica filled compounds were prepared by adding n-octyl-triethoxyl or mercatopropyl-trimethoxyl silane. Both silanes are capable of retarding filler flocculation upon heating and give compounds with less developed filler networks either by reducing F-F interactions or by screening filler networks through P-F attachments. The filler network is shown to mediate the low-temperature hysteresis due to the polymer glass transition (Tg) by changing the temperature dependence of the compound dynamic storage modulus (G′). At temperatures far above the Tg, the compound tan δ is governed by mechanisms that control the degree of filler networking. Compounds with less developed networks show weaker strain dependence on G′ and tan δ. Both reduced F-F and increased P-F interactions will give a compound with a less developed network. However, significant reduced tan δ is only found in a system that shows strong P-F interaction due to less energy loss upon deformation by fewer network breakage and increased P-F crosslinks. This is exemplified by comparing the compound loss moduli (G″) of various stocks with corresponding G′ in G-plot (G″ vs. G′).
Reduced Hysteresis in Truck Tread Compounds by Using Aramid Short Fibers
Authors: Datta R. N.
Published: February 2011

The preparation of an intricate engineering component can be accomplished by using aramid short fibers as the reinforcing medium of an elastomer, especially tread compounds with a target to improve hysteresis without sacrificing other performance properties. For many years short fibers have been used to reinforce all sorts of rubbers. Particularly compounds with relatively low fiber content have been successful in improving hose and belt performance. The use of aramid short fibers, for example, poly-paraphenylene terephthalamide, PPTA (Twaron), poly-(metaphyneleneisophthalamide, MPIA (Conex) and co-poly-(paraphenylene/3,4′-oxydiphenylene terephthalamide, PP/ODPTA (Technora) have been explored in typical truck tread compounds with an objective to improve hysteresis, thereby reducing rolling resistance. This paper presents the results on our latest research in this area focusing on improvement in rolling resistance, heat build up, flex, and dynamic properties. Compounds have been engineered to improve the hysteresis characteristics with a positive effect on wear and tear resistance. Furthermore, the levels of fibers and their sizes have been varied to obtain best performance advantage. This paper will provide a snapshot of all advantages that can be obtained by addition of small amount of fibers, often in a way which is impossible with conventional particulate fillers or with other fibers.
Physical Property Changes in Commercial Natural Rubbers during Long Term Storage
Authors: Yunyongwattanakorn Jintana , Sakdapipanich Jitladda T.
Published: February 2011

The physical properties during long term storage of selected commercial Standard Thai Rubbers (STR), i.e. STR XL, STR 5L and STR CV60 as high-graded natural rubber (NR), were investigated. Sections of commercial NR were subjected to examination after storage-hardening. STR 5L showed clearly an increase in Mooney viscosity (VR), Mooney relaxtion (MR30), gel content and initial plasticity (P0), higher than that of STR XL. This result suggests that STR 5L exhibits the highest inconsistency in physical properties. The increasing viscosity and gel content of STR 5L and STR XL samples suggest the occurrence of a crosslink structure during storage. STR CV60, known as a viscosity-stabilized NR sample, also showed an increase in VR, gel content, P0, and high PRI value during long storage. These findings indicate that storage-hardening occurred in the rubber samples even after carefully controlled production procedures. As for the different sections of samples, there was no clear relation with gel content with respect to storage time, indicating that depth or positions of specimens in a certain rubber bale did not affect the storage-hardening phenomenon.
Mechanistic Study of the Effect of Adhesion-Promoter Resins on the Crystal Structure of the Copper Sulfide Adhesion Layer at the Rubber-Brass Interface
Authors: Patil Pankaj Y. , van Ooij William J.
Published: February 2011

We have previously presented the effect of adhesion-promoter resins, used in the belt compound of tires, on the mechanical properties of the rubber compounds. We have also proposed that the presence of certain adhesion-promoting resins could lead to the formation of a copper sulfide adhesion layer that might protect the residual brass from corrosion during humidity-aging conditions. Highly polished brass coupons were cured against the natural rubber compounds and the cured rubber was later removed using o-DCB (ortho-dichlorobenzene) solvent. To test our proposed theory, we studied the crystal structure of the copper sulfide adhesion layer using synchrotron source Grazing Incidence angle X-ray Diffraction (GIXRD). In this paper, we confirm our previously proposed theory that the presence of adhesion-promoting resins alters the crystal structure of the adhesion layer resulting in a durable rubber-to-brass bonding during aging conditions.
On Multi-Scale Modeling of Elastomeric Laminated Composites for Structural Analysis
Authors: Gurvich Mark R.
Published: February 2011

Analysis of complex structures is often based on multi-scale modeling, where effective properties of certain substructures are used instead of actual properties of smaller components. Laminated composites are usually considered as such sub-structures in components with laminated design. In case of elastomeric composites, well-known classical laminate theories could hardly be used due to significant non-linearity and incompressibility of material deformation. A convenient engineering variant of laminated model is proposed in this study for composites where neither physical nor geometrical non-linearity may be ignored. Possible material incompressibility is also taken into account. The model is primarily based on a previously developed constitutive approach to describe effective properties of anisotropic hyperelastic materials. Analytical and computational implementation of the model is considered in detail. Numerical examples illustrate accuracy and convenience of the model for representative cord/rubber composites.
Dispersion of Layered Organosilicates in Isobutylene-Based Elastomers
Authors: Tsou Andy H. , Measmer Matthew B.
Published: February 2011

Dispersion morphologies of polymer-layered silicate nanocomposites based on either brominated poly(isobutylene-co-para-methylstyrene), BIMSM, or brominated poly(isobutylene-co-isoprene), BIIR, and an organosilicate, dimethylditallow ammonium-exchanged montmorillonite, Cloisite™ 6A, with and without N660 carbon black fillers were examined using SAXS, WAXS, AFM, and TEM. These compounds were prepared using an internal mixer and cured for property measurements. Due to the observed partial orientation of organosilicates and their possible heterogeneous intercalation, degrees of exfoliation and dispersion of organosilicates in BIMSM and BIIR were unable to be characterized and quantified simply by TEM, AFM, or SAXS alone. Instead, using the projected aspect ratio of organosilicates in BIMSM or BIIR, extracted from Gusev-Lusti equation based on measured permeability ratios, was found to provide a relative measure of their dispersion state. Since better dispersion, higher planar orientation, and/or increasing extent of exfoliation lead to higher aspect ratio, this calculated aspect ratio was used as a measure of organosilicate dispersion in BIMSM and BIIR compounds. According to experimentally extracted projected aspect ratios, it was found that BIMSM disperses organosilicates better than BIIR and that carbon black filler does not affect the organosilicate dispersion in BIMSM. Addition of tertiary amines in BIMSM enhances the dispersion of organosilicates, possibly through favorable interactions between organosilicates and quaternary ammonium functionalized BIMSM, resulting in further reduction in permeability.
Electron Beam Curing of Elastomers
Authors: Bhowmick Anil K. , Vijayabaskar V.
Published: February 2011

Modification of thermoplastic and rubbery materials by electron beam (EB) radiation is a potential method for development of new polymers and composites. Irradiation of polymeric materials results in grafting and subsequently formation of a three dimensional network through the union of generated macro radicals. In the Green drive, i.e. to make the world pollution free, this technology takes an important position. Curing of a number of both non-polar and polar elastomers using an electron beam was carried out in our laboratory. The effects of irradiation dose in presence and absence of radiation sensitizer on the crosslinking and structure of ethylene propylene rubber, ethylene octene copolymer, nitrile, acrylic and fluorocarbon rubbers were investigated. An analysis of crosslink to scission ratio on the basis of Charlesby-Pinner Equation was done. Mechanical and dynamic mechanical properties showed that these improved with radiation dose and sensitizer level up to certain values, beyond which the properties deteriorated due to chain scission reactions. The properties of the vulcanizates were correlated with the structure. EB cured samples were compared with the samples having conventional crosslinks. Some applications of the electron beam curing are highlighted.
Mechanical Behavior of Rubber at High Strain Rates
Authors: Roland C. M.
Published: February 2011

Methods to obtain the mechanical response of rubber at high rates of strain are reviewed. These techniques include the extrapolation of low strain, low strain rate data, the limitations of which are discussed, extrapolations to elevated hydrostatic pressure, and direct determinations using split Hopkinson bar and drop weight testers, as well as miscellaneous methods. Some applications involving rubber at strain rates sufficient to induce a transition to the glassy state are described.
Staining Polymers for Microscopical Examination
Authors: Smith Ronald W. , Bryg Victoria
Published: February 2011

Polymers find widespread use in blends, graft copolymers, polymer alloys, and composites. Staining is an important tool for microscopically visualizing polymer phases and morphologies in these multi-component systems. Three stains have been used in most investigations. These stains (and the functional groups they are aimed at) are: osmium tetroxide for chemical unsaturation; ruthenium tetroxide for styrenics; and phosphotungstic acid for polyamides. Beyond these three basic stains there are a significant number of additional ones that have been developed for special cases. Aside from reacting chemically with functional groups, stains have been used as: negative (outline) stains; stains to delineate amorphous-crystalline regions; stains for microvoids, and stains for phase boundaries. Stains are most commonly transported to the target functional groups in tow ways — dissolved in liquid media or by direct contact with stain vapors. Improvisations have been developed to meet special staining problems. These improvisations most often involve: 1) chemical alteration of a polymer backbone to introduce a stainable functionality; 2) tailoring of staining media to provide adequate diffusion into the matrix; 3) preferential swelling of a blend component in order to accept a stainable moiety; 4) tactical use of a staining temperature to take advantage of differences in glass transition temperatures of blend components; and 5) optimization of chemical equilibria to expedite staining time or extent. Examples of these modifications are presented along with some cautionary notes regarding some artifact that may arise. A plea is made for more adequate descriptions of staining protocols in published articles. In too many cases there is inadequate description of staining methods and experimental duplication is put in jeopardy.
HXNBR Coating for Improving Aging Resistance of Natural Rubber Products
Authors: Joseph Rani
Published: February 2011

HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.
Multifunctional Additives as Zinc-Free Curatives for Sulfur Vulcanization
Authors: Heideman Geert , Noordermeer Jacques W. M. , Datta Rabin N. , van Baarle Ben
Published: February 2011

Concern about the release of eco-toxic zinc species from rubbers into the environment leads to an increasing interest in potential substitutes. This investigation reports on the application of Multifunctional Additives, amines complexed with fatty acids, for sulfur vulcanization of rubbers. Good physical properties can be obtained in s-SBR compounds using the MFA/S cure system, albeit at the cost of a shortened scorch time as compared to a ZnO/stearic acid system. Inclusion of ZnO lengthens the scorch time, though it reduces the state of cure and ultimate properties. The amount of ZnO used in the MFA-formulations is considerably lower than in the conventional systems. The introduction of CaO and MgO leads to an improvement in the state of cure and physical properties. Amines play a vital role in the vulcanization process, hence various amine-complexes have been synthesized and investigated as zinc-free curatives in s-SBR compounds. It is observed that the scorch time is related to the basicity of the amines. The results of Model Compound Vulcanization studies with MFAs reveal a fast decomposition of the accelerator and some differences in the distribution of the crosslinked products. The conclusion must be drawn, that the chemistry involved in the MFA-systems is fundamentally different from the conventional vulcanization systems.