bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on Parameters Affecting the Morphology Development of Dynamically Vulcanized Thermoplastic Elastomers Based on EPDM/PP in a Co-Rotating Twin Screw Extruder
Authors: Sararoudi S. Shafiei , Nazockdast H. , Katbab A. A. 
Published: February 2011

Abstract
The morphology development of dynamically vulcanized thermoplastic elastomers (TPVs) based on EPDM/PP in a modular intermeshing co-rotating twin screw extruder was studied. Effects of the blend composition and screw speed were considered. The morphological studies were carried out on the cryogenically fractured surface of the samples using Scanning Electron Microscopy (SEM) technique. The flow behavior and melt viscoelastic properties of the samples were also investigated by using Rheometric Mechanical Spectrometer (RMS). The SEM results from TPV samples produced in the twin screw extruder showed a matrix-disperse type morphology similar to those reported for the TPV samples prepared in an internal mixer. The dynamic vulcanization process imposed on the molten blends resulted in a remarkable increase in the steady state torque of the extruder whose extent was found to be dependent upon the EPDM content and screw speed. These results were explained in terms of an agglomerate structure formed between the cured rubber particles. The TPV samples, in particular the samples containing 60% of EPDM, showed a pronounced viscosity upturn and strong elastic modulus (G′) at low frequency range. It was demonstrated that these results in conjunction with the results of relaxation time distribution H(λ) of the samples can provide a great insight into understanding the role of the blend composition and the processing variables on morphology development in the TPV samples in the co-rotating twin screw extruder.
Experimental Study and Simulation of Interface Development and Penetration in Two-Component Transfer Molding of Rubber Compounds
Authors: Li C. T. , Isayev A. I. , Warley R. L. 
Published: February 2011

Abstract
Simulation and experimental studies of pressure-controlled sequential transfer molding of two SBR rubber compounds under isothermal condition have been carried out to obtain a two-layered sandwich structure. One SBR compound, intended for the skin, is first laid up in the cavity; and another SBR compound, intended for the core, is used for transfer. The SBR is subjected to pressure in order to penetrate into the skin and push the layup to fully fill the cavity. The obtained moldings have an encapsulated skin/core sandwich structure. Two material combinations with different viscosity ratios have been studied. The rheological interaction of skin/core components and its effect on the penetration behavior and interface shape have been investigated. The influence of processing conditions, such as the volume fraction transferred and pressure, is elucidated. From the experiment and simulation it is found that the penetration and the interface development are significantly affected by the rheological properties of the compounds and the volume fraction transferred. At the same time, the pressure imposed during transfer molding is found to have little effect on the interface development at a constant volume fraction transferred.
Natural Rubber-g-Glycidyl Methacrylate/Styrene as a Compatibilizer in Natural Rubber/PMMA Blends
Authors: Suriyachi P. , Kiatkamjornwong S. , Prasassarakich P. 
Published: February 2011

Abstract
Graft copolymer of glycidyl methacrylate and styrene onto natural rubber latex was synthesized by emulsion polymerization using cumene hydroperoxide and tetraethylene pentamine as a redox initiator. The effects of initiator and monomer concentration, reaction temperature and time on grafting efficiency and monomer conversion were investigated. The dynamic mechanical properties and morphology of grafted natural rubber were studied. The grafted natural rubber product could be used as a compatibilizer for natural rubber/PMMA blends. The mechanical properties such as tensile strength, elongation at break, tear strength, hardness, and impact energy were evaluated as a function of grafted natural rubber content. A good compatibility of natural rubber/PMMA blends was obtained at 5–10 phr of grafted natural rubber content. The fracture surface examined by scanning electron microscopy showed that the grafted natural rubber acted as an interfacial agent and gave a good adhesion between the two phases of the blend.
Improved Differential Scanning Calorimetric Measurement Method for the Small Reaction Heat Capacities
Authors: Danes Florin , Garnier Bertrand 
Published: February 2011

Abstract
Heat capacities of the different rubber states are important features for the engineering calculation of rubber manufacturing. The heat capacity change Δcp due to the vulcanization process has been measured with a differential scanning calorimeter (DSC) only after reducing the standard error of a Δcp measurement under 5 J kg−1 K−1. For this purpose, we used sealed (up to 150 bar) DSC sample pans which avoid mass losses. Heat capacities before and after vulcanization were measured on the same samples using special DSC procedure and reversible thermal effects due to rubber components were corrected. For natural rubber vulcanized with sulfur at t=40…110 °C we found, in J/(kg S)−1 K−1: Δcp=76+11 t, whatever the temperature vulcanization between 100 and 160 °C.
AFM Study of Rubber Compounds
Authors: Wang C. C. , Donnet J. B. , Wang T. K. , Pontier-Johnson M. , Welsh F. 
Published: February 2011

Abstract
A series of rubber compounds filled with carbon blacks and silica has been studied by atomic force microscopy (AFM). The microdispersion of carbon black aggregates in rubber compounds can be clearly observed. The surface morphology of worn treads after road testing studied by AFM is also reported.
The Payne Effect in Double Network Elastomers
Authors: Wang J. , Hamed G. R. , Umetsu K. , Roland C. M. 
Published: February 2011

Abstract
Double network elastomers were prepared by curing under strain previously-crosslinked natural rubber or styrene-butadiene copolymer. The rubbers were reinforced with carbon black, so that the conventional (singly-cured) materials exhibited a substantial Payne effect, reflecting agglomeration of the filler particles. This effect was much reduced in the double networks - the storage modulus varied more weakly with strain amplitude, and the mechanical hysteresis was substantially smaller. Comparable results were obtained for dynamic mechanical measurements employing different test geometries; that is, the effect is independent of the direction of the strain relative to the orientation of the double network. These results indicate that deformation during the imposition of a second network disrupts the carbon black agglomerates, and this deflocculated structure is stabilized by the second crosslinking. Thus, double network processing is a general means to lower the hysteresis of filled rubbers.
Response of Elastomeric Blocks During Large Compression Strains
Authors: Patenaude K. J. , Tao Z. , Mead J. L. , Stacer R. G. , Rodriguez G. 
Published: February 2011

Abstract
An experimental investigation has been conducted to evaluate the response of rubber blocks under large compressive loadings. Quantitative measurements of the nonlinear behavior of two rubber compounds were tested over compressive strains ranging from 17 to 74 percent. Three distinct phenomena were observed in the deformation behavior of both materials. The first was a dramatic increase in contact area (over 130 percent) between the rubber and the platens, beginning at strains above approximately 33 percent. This increased surface area is used to provide stress corrections in several quantitative models, and appears to physically represent a rolling flow phenomenon, similar to fountain flow in observed in polymer melts. The second and third phenomena are associated with a nonlinear normal stress distribution across the sample's surface. These two phenomena are stress maxima and minima associated with stress singularities predicted by nonlinear elastic models. Deviations in stresses across the specimen surface of up to a factor of four are reported. It is concluded that appropriate constitutive equations describing these phenomena are required before meaningful predictive models can be developed.
New Technique for Measurement of Rubber-to-Metal Bond Failure
Authors: Lawrence C. C. , Lake G. J. , Thomas A. G. 
Published: February 2011

Abstract
A new test, involving combined pure and simple shear, that can produce failure very close to the interface between the rubber and the bonding agent in a rubber-to-metal joint, is described. The test allows changes in the position of the tip of the de-bonded region to be followed with time, enabling the failure rate to be determined. The latter can be related to the strain energy release rate so that a fracture mechanics based analysis can be applied. Failure characteristics can be correlated with features of the de-bond surface. The results suggest that even when failure is very close to the interface, the measured strength is similar to that of the rubber.
Dynamic Mechanical Properties of High Density Polyethylene and Nitrile Rubber Blends: Effect of Blend Ratio, Compatibilization and Filler Incorporation
Authors: George Josephine , Neelakantan N. R. , Varughese K. T. , Thomas Sabu 
Published: February 2011

Abstract
Blends of high density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. Dynamic mechanical analysis revealed that elastic modulus has a strong dependence on blend ratio. Loss factor peaks increase with increase in rubber content. Pure components exhibit single Tg whereas two Tgs can be observed in the blends indicating incompatibility between the constituents. Loss modulus data also give similar information. The addition of compatibilizer has only a marginal effect on tan δ peak corresponding to the transitions in NBR. The elastic modulus values of the compatibilized blends are slightly higher than that of incompatible blends. In dynamically vulcanized blends the Tg due to α-relaxation of NBR is increased in blends containing a high concentration of rubber phase. In filled blends the elastic modulus showed significant increase over unfilled system. Also, the damping factor is enhanced by filler incorporation indicating that such materials could find application in vibration dampers. The suitability of various theoretical models in predicting the blend moduli is examined. The Takayanagi model fits well with the experimental data in unfilled blends.
Accelerated Aging of Tires, Part II
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 various durability, high speed and performance tests. The first step was to determine the aging characteristics of field-aged tires, which has been the subject of another paper. For this work, tires were statically aged in ovens. Tires were mounted, inflated, then oven aged continuously at temperatures ranging from 40 °C to 100 °C for various periods of times (from 2 weeks to 12 weeks). Both air and a 50/50 blend of N2/O2 were used as the inflation media. The tires were then dissected and analyzed for tensile and elongation properties of the rubber at the end of the steel belts. The results show that as the temperature was increased from 40 °C to 70 °C, the property degradation of the steel belt rubber accelerated. Shift factors were determined based on time-temperature superposition and the results analyzed by using the Arrhenius methodology. The oven results were similar to the field data, meaning the chemical aging mechanism was the same for both. As the oven temperature increased above 70 °C, degradation reactions began to dominate and the apparent aging mechanism changed.
A Review of Rubber Oxidation
Authors: Li Gui-Yang , Koenig J. L. 
Published: February 2011

Abstract
The aging of rubber caused by oxidative degradation leads to the deterioration in the physical and mechanical properties of vulcanized rubbers. In an effort to improve the oxidative stability of rubbers and elastomers, considerable amount of work has been carried out over the past 50 years (especially in the most recent 5 years) in order to understand degradation modes and effects in rubber due to the action of oxygen and ozone in the air. Different mechanisms have been proposed to interpret the experimental data relative to the oxidation of rubber. The diffusion limited theory has been widely used in the literature and verified by many experiments. Various instrumental techniques have been utilized to characterize the oxidation and degradation and their mechanisms in rubber compounds. Recently, FTIR imaging has demonstrated a unique combination of spectral and spatial resolution which allows not only the identification of the oxidation products but also their spatial distribution from the oxygen penetrating surfaces. This critical review will cover the major developments in our understanding of the oxidation of rubbers.
Steel Tire Cord-Rubber Adhesion, Including the Contribution of Cobalt
Authors: Fulton W. Stephen 
Published: February 2011

Abstract
This review will discuss the mechanisms that are responsible for the adhesion between brass-coated steel tire cord and rubber. In particular, the role of cobalt as an adhesion promoter and how it influences the stability of the bond between the steel tire cord and rubber are examined. Some of the techniques by which the morphology of the interfacial layers has been investigated will be discussed, along with a brief review of the latest bonding mechanisms.
Role of Compatibilization in Recycling Rubber Waste by Blending with Plastics
Authors: Mangaraj D. 
Published: February 2011

Abstract
Blending ground rubber with thermoplastic and thermoset polymers is a very cost effective and efficient method for recycling rubber waste. However it is important for vulcanized rubber particles and the thermoplastic matrix to adhere to each other to form co-continuous type morphology to provide necessary strength properties. The paper discusses the principles underlying compatibilization and discusses the three types, namely mechanical, non-reactive and reactive compatibilization. Past work in compatibilizing ground rubber from tire waste (GRT) with thermoplastics has been reviewed and the use of compatibilized GRT/ plastic products in the preparation of a variety of value-added products, including thermoplastic elastomers has been discussed.
Continuous Ultrasonic Treatment of Uncured and Sulfur Cured SBR: Effect of Styrene Content
Authors: Isayev A. I. , Kim S. H. , Feng Wenlai 
Published: February 2011

Abstract
Unvulcanized and vulcanized SBR samples with styrene content of 18 and 23.5% were used to investigate the effect of ultrasound treatment on their structural characteristics. Gel fraction and crosslink density of gel are measured. Molecular weight and molecular weight distribution of sol are studied to determine the level of degradation of the macromolecular chain in ultrasonically treated unvulcanized and vulcanized rubbers. It is shown that the weight and number average molecular weight of sol in devulcanized SBR is, respectively, lower and higher in the samples having higher styrene content. Ultrasonic treatment of virgin unvulcanized SBR causes generation of gel along with its main chain modification due to the competition between chain scission and crosslinking. The competitive reactions taking place during this treatment are discussed. It was found that the intermolecular bonds in SBR vulcanizates containing higher styrene content are easier to break. The structural characteristics of devulcanized SBR rubber were simulated using the Dobson-Gordon theory of rubber network statistics. A fairly good agreement between experimental data and theoretical prediction on normalized gel fraction vs. normalized crosslink density was achieved. The simulation of devulcanized SBR rubber indicated that the rate of crosslink rupture is much higher than that of main chain. The styrene content in SBR rubber does not affect kp/kα substantially.
Asphalt Modified by Partially Hydrogenated SBS Tri-Block Copolymers
Authors: Vargas M. A. , Chávez A. E. , Herrera R. , Manero O. 
Published: February 2011

Abstract
This work examines the modification of asphalt with hydrogenated poly (styrene-butadiene-styrene) copolymer containing different amounts of butadiene and ethylene-co-butylene. The polymer composition can be described generically as poly (styrene−[(butadiene)1−x−(ethylene−co−butylene)x]−styrene), where x is the hydrogenated fraction of the molecule. These hydrogenated (SBEBS) copolymers were produced by in-situ hydrogenation following a Ziegler-Natta catalytic reaction of poly (styrene-butadiene-styrene) tri-block copolymers (SBS), which were previously synthesized by anionic polymerization. Control over the hydrogenation time produces SBEBS polymers with various degrees of saturation of the polybutadiene block, as characterized by FTIR, HNMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Polymer-modified asphalts (PMA) were obtained by a high-temperature mixing process with AC-20 asphalt (Salamanca, Mexico) and SBS or SBEBS copolymers. PMA samples were characterized before and after high-temperature storage tests by fluorescence microscopy, rheometry, and mechanical tests. Results indicate that PMA obtained from SBEBS contain a polymer matrix with well-dispersed asphalt rich phase, with improved mechanical and thermal stability over those PMA produced with SBS. Compatibility between SBEBS and the aromatic fraction of maltenes can explain the dispersion of the polymer in asphalt and the enhanced properties.
Reactions of Radicals in Filled Rubber Compounds: II. Generation and Subsequent Reactions of Radicals Upon Deformation
Authors: Kawakubo Makoto , Tsunoda Katsunori , Yajima Hirofumi , Ishii Tadahiro , Kaidou Hiroyuki , Ahagon Asahiro 
Published: February 2011

Abstract
Effect of stretching on oxidative crosslinking of a carbon black filled IR vulcanizate at a normal temperature was studied by means of ESR and crosslink density measurements. Upon deformation, ESR intensity increased and crosslink density decreased, indicating scission of load supporting bonds generating free radicals. Bond scission increased with increasing strain. Resting after deformation, the ESR intensity decayed steadily following simple combination of first order and second order kinetics. The decay was overwhelmingly caused by first order reactions, which were considered to be irrelevant to crosslinking. On the other hand, crosslink density increased during resting. The results strongly suggested that ESR observed the radicals at the surface of the carbon black filled rubber, while crosslink density evaluated the bulk property. The crosslink density increase during resting outweighed the reduction due to deformation. Deformation accompanied by radical generation apparently accelerated oxidative crosslinking.
Wear Behavior of Silica Filled Tire Tread Compounds by Various Rock Surfaces
Authors: Nayek Suprakash , Bhowmick Anil K. , Pal Samir K. , Chandra Arup K. 
Published: February 2011

Abstract
Wear of silica filled tire tread compounds made from natural rubber (NR) and styrene butadiene rubber (SBR) against various rock surfaces at different normal loads and frictional work was investigated. The rocks chosen, i.e. granite, quartzite, limestone and shale, had variation in hardness and chemical composition. Wear, V, increased with normal load, N and frictional work, Fw, and these were related by V=βNα and V=k Fw n, where β,α,k and n were constants and dependent on the nature of the abraded surface and the rubber. The rate of wear of SBR was found to be much lower than that of NR against all rock surfaces. All the results could be explained with the help of dynamic co-efficient of friction, frictional work and structural changes during abrasion. The rate of wear as well as the dynamic coefficient of friction decreased with silica filler loading up to certain loading and then increased. These were 60 phr silica for NR and 70 phr silica for SBR. The surfaces of NR and SBR when abraded against different rock surfaces became tarry on prolonged abrasion. The debris were oily and aggregated for NR compound and were particulate for SBR compound. The debris and the ridges were analyzed by an image processing technique.
The Difference between Iodine Number and Nitrogen Surface Area Determinations for Carbon Blacks
Authors: Donnet J. B. , Santini A. , Maafa D. , Balard H. , Padella F. , La Barbera A. 
Published: February 2011

Abstract
The iodine number furnishes surface area values in disagreement with the NSA technique in the case of disordered carbon i.e., lower than NSA in case of high oxygen content (more than 2%), but higher for low oxygen content (less than 1%). Because carbon blacks are solids which exhibit graphitic structure, some milled graphite samples, were taken as model materials and analyzed. Surface area was determined by using both NSA and N≩I2 techniques, and the difference between the results given by the two techniques were observed and related to the microstructure, which was analyzed by using X-ray diffraction, Raman spectroscopy, and the oxygen content was measured by using elementary analysis. Two different models of iodine adsorption have been proposed, respectively, for the graphitic parts of the graphite grains and for the disordered part of the grains. An analytical relationship between the differences of iodine and nitrogen surface area values, microstructure and oxygen content was proposed and successfully tested. The same relationship was applied to some commercial and experimental carbon black with good results.
An Appropriate Model Compound for the Accelerated Sulfur Vulcanization of Polyisoprene: I. The Mechanism of Bisbenzothiazole-2,2′-Disulfide Accelerated Vulcanization of Squalene in the Absence of ZnO
Authors: Boretti L. G. , Woolard C. D. 
Published: February 2011

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