bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent Developments in Crosslinking of Elastomers
Authors: Aprem Abi Santhosh , Joseph Kuruvilla , Thomas Sabu 
Published: February 2011

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.