bluuebunny/crossref_metadata_2025_split huggingface dataset:
Homogeneous Zinc (II) Catalysis in Accelerated Vulcanization: V. The Prevailing Mechanism of Crosslink Formation in Mercaptobenzothiazole Systems
Authors: Damen R. , Nieuwenhuizen P. J. , Haasnoot J. G. , Reedijk J. , Couchman S. M. , Jeffery J. , McCleverty J. A. 
Published: February 2011

Abstract
This paper reports a detailed investigation of the molecular mechanism of crosslink formation in sulfur vulcanization accelerated by mercaptobenzothiazole accelerators, such as bis(mercaptobenzothiazolato)zinc(II) (ZMBT), mercaptobenzothiazole disulfide (MBTS) and N-cyclohexyl-2-benzothiazole sulfenamide (CBS). First, the current state of knowledge regarding the mechanism of crosslink formation in these systems is briefly reviewed.
Subsequently, Reaction-Stage Modeling experiments are reported with the model-crosslink precursor (2,3-dimethyl-2-butene-1-yl)(mercaptobenthiazolato)sulfide (dmb-S2-Bt). These experiments reveal that in the presence of bis(cyclohexylamine)bis(mercapto benzo-thiazolato)zinc(II) (ZMBT·(H2NC6H11)) the precursor dmb-S2-Bt is transformed into a disulfidic crosslink and MBTS via symmetric disproportionation reactions. Also sulfuration and isomerization reactions, leading to a hitherto unknown type of pendent group, namely 2-(2,3-dimethyl-2-buten-1-yl)-1,2-benzisothioazolin-3-thione, were shown to occur. The zinc-amine complex was found to have a pronounced catalytic effect on the crosslink reaction; in its absence, hardly any crosslinks are formed. Reactions performed in the presence of additional MBTS showed an inhibitory effect on crosslink formation, suggesting that the disproportionation reaction is in fact an equilibrium reaction. Indeed, it appeared possible to transform disulfidic model crosslinks into crosslink precursors in the presence of both MBTS and the ZMBT-amine complex. These results have lead to determine the prevailing mechanism by which crosslinks are formed during mercaptobenzothiazole vulcanization, namely through an equilibrated, ZMBT-catalyzed disproportionation reaction of crosslinks precursors. This mechanism not only explains the observations in the present model study, but is also in line with results obtained earlier in real rubber experiments.
Influence of Crosslink Characteristics Induced by Aromatic-Based Antioxidants on the Swelling and Stress-Strain Behavior of Natural Rubber Vulcanizates
Authors: Madkour Tarek M. , Azzam Rasha A. 
Published: February 2011

Abstract
Stress-strain measurements were performed on dry and swollen natural rubber vulcanizates prepared using both sulfur as the crosslinking agent and aromatic-based bound antioxidants acting as a second crosslinking agent. The aromatic-based antioxidants were synthesized and analyzed spectroscopically in order to relate the final behavior of the vulcanizates to the nature of the crosslink characteristics. The anomalous upturn in the modulus values of these networks in response to the imposed stress was shown to persist in the dry as well as the swollen state. Since the swollen elastomeric chains cannot undergo a strain-induced crystallization, the abnormal upturns in the modulus values in an absence of a filler were explained on the basis of the limited extensibility of the short chains of networks prepared using two different crosslinking agents in line with earlier modeling predictions. Remarkably, the swelling experiments revealed the increase in the crosslink density of the networks in the early stages of the thermal oxidative degradation procedure indicating a post-cure of the chemically bound antioxidants to the elastomeric chains, which incidentally corresponds to a maximum in the modulus values of the networks. The rheological and other mechanical properties such as the hardness were shown not to have been affected as a result of the incorporation of the chemically bound antioxidants.
Evaluation of Isobutylene-Based Elastomers in a Model Winter Tire Tread
Authors: Waddell Walter H. , Kuhr Julie H. , Poulter Robert R. 
Published: February 2011

Abstract
The performance of butyl, chlorobutyl, bromobutyl, and brominated isobutylene-co-para-methylstyrene (BIMS) rubbers were evaluated versus a solution-polymerized styrene-butadiene rubber with 20% bound styrene in model winter tire tread formulations containing natural rubber and butadiene rubber. Isobutylene-based elastomer performance was compared in carbon black-filled and silane-coupled silica-filled systems. Based on laboratory dynamic properties predictive of wet and winter traction, and on DIN abrasion index values, BIMS is the elastomer of choice affording increased tangent delta values between 0 °C and −40 °C, and the highest DIN abrasion index values of the isobutylene-based elastomers. Evaluation of BIMS / NR / BR blends in model compounds show its utility as a tread polymer for improving winter performance.
Structure and Properties of Natural Rubber and Modified Montmorillonite Nanocomposites
Authors: Magaraphan Rathanawan , Thaijaroen Woothichai , Lim-ochakun Ratree 
Published: February 2011

Abstract
Montmorillonite clay was organically modified by primary and quaternary ammonium salts (having C12-C18). The modified clay was added to a solution of natural rubber in toluene at various contents. Characterization of the structure of the nanocomposites was performed by using x-ray diffraction and transmission electron microscope. The results showed that the silicate layers of the clay were expanded so that the exfoliated nanocomposites were obtained at clay content below 10 phr; above that the nanocomposites became partially exfoliated. Moreover, long primary amine showed more improved mechanical properties than the quaternary one (at the same carbon numbers). The longer organic modifying agents resulted in better expansion of silicate layer distance indicating more intercalation of natural rubber molecules in between clay galleries. The curing properties were also improved. It was found that a small loading of 7 phr is enough to bring good mechanical properties in comparison to those of high structure silica filled and carbon black filled natural rubber vulcanizates.
Effect of Carbon Black Concentration on Cut Growth in NR Vulcanizates
Authors: Hamed G. R. , Al-Sheneper A. A. 
Published: February 2011

Abstract
Dumbbell specimens containing edge razor-cuts of various depths, c, have been prepared from sulfur-vulcanized natural rubber compositions containing 0–75 phr of N115 black. Normal tensile strengths (c=0) of the gum and all black-filled samples are similar. However, cut growth resistance (CGR) relative to the gum, depends strongly on black content and cut depth. With about 6–15 phr of black, filled specimens are weaker than the gum and fracture occurs by simple forward growth of the original cut tip, i.e., a single crack develops and propagates laterally. At about 18 phr of black, filled specimens become stronger than the gum and cracking becomes complex. Prior to catastrophic rupture, crack splitting occurs near the original cut tip - forming at least two slowly-growing, longitudinal cracks. These reduce the stress concentration caused by the cut, thereby delaying rupture, and marking the onset of “reinforcement”. All pre-cut specimens containing 18–75 phr of black are stronger than the gum and they exhibit crack splitting. Specimens containing 50 phr of black have the highest strength - being about ten times as strong as the gum when cuts are large. The decrease in CGR at low levels of black and increase at high levels is attributed to competing effects upon the addition of carbon black to NR.
Miscibility of EPM-EPDM Blends
Authors: Dikland H. G. , Van Duin M. 
Published: February 2011

Abstract
Blends of elastomers are often used as a basis for compound formulations. For instance, tire tread formulations may contain NR, BR and SBR in order to provide cost-effective products with good mechanical properties, dynamic properties and abrasion resistance. Blends of dissimilar EPDM grades are often used when formulating EPDM compounds. In many cases such EPDM-EPDM blends are used to obtain synergy, i.e. properties of the parent EPDM grades are not averaged, but favorable properties of the blend components are combined or unfavorable properties suppressed. In the present paper the miscibility regime for gum stock EPDM-EPDM blends has been calculated based on elementary thermodynamic considerations. Results of calculations have been validated by experiments, and excellent agreement was found. It was found that the chemical composition of EPDM grades has a major influence on miscibility. It is concluded that, as a rule of thumb, two EPDM grades are thermodynamically miscible if the difference between the combined ethylene and third monomer content is less than 12 % by weight. Based on the results it is possible to understand and to some extent predict the behavior of rubber products based on dissimilar EPDM grades.
Effects of Storage and Service on Tire Performance: Oil Component Content and Swelling Behavior
Authors: Kataoka Takahiro , Zetterlund Per B. , Yamada Bunchiro 
Published: February 2011

Abstract
In order to investigate the effects of storage and service on passenger car tire performance, two separate sets of samples were characterized: (i) tires stored at a temperature of 45–50 °C for different time periods, and (ii) used tires of different mileage. The tires were analyzed with respect to the performance of the tread rubber as manifested in the modulus at 200% elongation, the tensile strength at break, the elongation at break, the hardness, the viscoelasticity of the rubber, swelling, and the oil component content. The change in the properties of the tires as functions of increasing storage time and mileage indicated a marked deterioration in performance. The rate of change in these properties was found to be markedly enhanced by the extra stimuli provided by service, as demonstrated by comparing tires of similar age but different mileage. The results were analyzed and rationalized in terms of the change in the degree of crosslinking and transfer of oil components from the tread rubber to the inner part of the tire or to the surroundings.
Effect of Carbon Black on Crosslinking
Authors: Gent A. N. , Hartwell† J. A. , Lee Ginger 
Published: February 2011

Abstract
For a number of different vulcanization systems, the equilibrium swelling ratios for carbon-black-filled and unfilled samples are shown to be linearly related, as found by Lorenz and Parks, indicating that the degree of crosslinking is not changed by incorporating carbon black. However, filled compounds swell less, and thus the apparent degree of crosslinking is significantly greater. For example, it is about twice as large for compounds containing 50 phr of HAF carbon black. This is confirmed by measurements of the elastic modulus of swollen samples. Relatively strong bonds appear to be formed between rubber molecules and the surface of carbon black particles - bonds that can withstand swelling stresses and temperatures of up to 120 °C. Bonding between rubber and carbon black is also indicated by the limited swelling of filled rubber compounds even before vulcanization, although in this case the apparent degree of crosslinking is smaller. Thus, vulcanization appears to enhance the contribution of rubber-particle bonding to the elastic modulus and restricted swelling of carbon-black-filled vulcanizates. Simple procedures are suggested for estimating the actual degree of crosslinking in filled rubber vulcanizates from measurements of equilibrium swelling or elastic modulus.
Durability Review of Elastomers for Severe Fluid Duties
Authors: Campion Robert P. 
Published: February 2011

Abstract
Durability aspects of elastomers when exposed to fluids under severe conditions for Offshore Oil Production and other applications have been reviewed. Examples are provided of situations where estimations of residual life might be made, and of others where different considerations might be the overriding factors. The approach has been to extend previously-presented overviews focused on the use of elastomers in the hostile conditions of the oil field industry, and made largely from personal experience, to include some work of others with reference to other application areas as well.
Dynamically Vulcanized PP/EPDM Blends: Effects of Different Types of Peroxides on the Properties
Authors: Naskar K. , Noordermeer J. W. M. 
Published: February 2011

Abstract
Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are thermoplastic elastomers produced by simultaneous mixing and crosslinking of a rubber and a thermoplastic. The effects of different types of peroxides as curing agents on the properties of PP/EPDM TPVs were investigated at a fixed blend ratio. The mechanical properties change significantly with the chemical nature of the peroxides, the extent of crosslinking of EPDM and the extent of degradation of PP. Three main parameters have been identified governing the final mechanical properties of TPVs: the solubility parameter of a peroxide relative to the substrates PP and EPDM, the fragmentation mechanism of the peroxide and the kinetic aspects of the peroxide fragmentation. Dicumyl peroxide gives the best balance of all properties, it complies the best of all with these parameters.
A “Wobble-Plate” Dynamic Test Device
Authors: Gent A. N. , Thompson T. T. , Ramsier R. D. 
Published: February 2011

Abstract
A simple dynamic tester is proposed, in which a disk of rubber is subjected to a rotating tilting deformation. In one arrangement, the rubber disk rests on a horizontal base and a light steel plate rests on its upper surface. A circular groove in the upper surface of the plate is centered on the axis of the rubber disk. An off-center vertical load is then applied to the rubber disk via a steel ball running in the circular groove. As the ball rolls round the groove, driven by friction with a rotating countersurface, the rubber disk undergoes a rotating off-center compression - a tilting deflection - that rotates at the same rate as the ball. If the rubber is perfectly elastic, no torque is required to maintain this motion and the deflection of the rubber will be exactly in phase with the compressive force. The maximum deflection then occurs at the location of the ball. However, if the rubber exhibits delayed elasticity, then the maximum deflection occurs after the ball has passed, at an angular separation δ, where δ is the angle of mechanical loss. Thus, the phase angle δ can be observed and measured directly. Also, if required, the separate components E′ and E″ of the complex dynamic modulus can be calculated from the applied force and deflection, and the torque required to maintain the motion.
Recent Advances in Anionic Synthesis of Chain-End Functionalized Elastomers Using Epoxides and Related Compounds
Authors: Quirk Roderic P. , Gomochak Deanna L. 
Published: February 2011

Abstract
Recent developments are reviewed for the applications of reactions of polymeric organolithium compounds with epoxides and oxetane to obtain the corresponding ω-hydroxy chain-end functionalized polymers. State-of-the-art characterization methods for ω-functionalized polymers are also reviewed. Investigations of the usefulness of functionalization reactions of polymeric organolithium compounds with ethylene oxide, propylene oxide, 1-butene oxide, styrene oxide, oxetane, 3,4-epoxy-1-butene, 3-glycidoxypropyltrimethoxysilane and other epoxides are described. In general, these functionalization reactions are very efficient (&gt; 90% yields of ω-hydroxy-functionalized polymers). The use of substituted epoxides is shown to provide an efficient methodology for attachment of a variety of groups at the polymer chain end.
Atomic Force Microscopy in Analysis of Rubber Materials
Authors: Yerina Natalya , Magonov Sergei 
Published: February 2011

Abstract
Atomic force microscopy (AFM) and electric force microscopy (EFM) have been applied for compositional mapping of a number of elastomers and related multicomponent materials. Several aspects of optimizing AFM experiments on polymers are discussed. AFM images revealed changes of EPDM morphology caused by crosslinking and by loading with fillers [carbon black (CB) and silica particles] and oil. It was shown that the morphology of isotactic polypropylene (iPP)/EPDM vulcanizates, which were studied with AFM and EFM, depends on the ratio of components, degree of cure and processing conditions. Diffusion of oil from the elastomer component to the matrix is evidenced in the AFM images. Selective distribution of CB in the iPP matrix is responsible for the electric conductivity of the thermoplastic vulcanizate.
Effect of Chain Length of Amine and Nature and Loading of Clay on Styrene-Butadiene Rubber-Clay Nanocomposites
Authors: Sadhu Susmita , Bhowmick Anil K. 
Published: February 2011

Abstract
Polymer nanocomposite is one of the highly discussed research topics in recent time. In this paper, we have reported the preparation and the properties of different nanoclays based on sodium montmorillonite, bentonite and potassium montmorillonite and organic amines of varying chain lengths, and Styrene Butadiene Rubber (SBR)-clay nanocomposites. The clays and the rubber nanocomposites have been characterized with the help of Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). X-ray results suggest that the intergallery distance is increased by incorporation of various amines. There is a great improvement in mechanical properties like tensile strength, elongation at break, modulus, work to break, and hysteresis on incorporation of nanoclay in SBR. TEM photographs show exfoliation of the clays in rubber to 5–10 nm range. The X-ray diffraction peak observed in the range of 3°– 10° for the control and the modified clays also disappears in rubber nanocomposites. Increasing chain length of clay modifiers and loading and nature of clays affect the mechanical and thermal properties significantly.
Role of Strain Crystallization in the Fatigue Resistance of Double Network Elastomers
Authors: Santangelo P. G. , Roland C. M. 
Published: February 2011

Abstract
Double networks were prepared from guayule rubber (GR), deproteinized natural rubber (DPNR), and styrene-butadiene rubber (SBR), and their properties compared to conventional “single networks” having the same crosslink density. Substantial residual strains (&gt; 150%) were obtained in all double networks, whereby the modulus parallel to the residual strain was enhanced. For the two strain-crystallizing elastomers, the fatigue resistance of the double networks (for extensions parallel to the residual strain) was higher than for their single network counterparts. Moreover, the guayule rubber, which is more strain-crystallizable than DPNR, exhibited the greater enhancement. For the amorphous SBR, on the other hand, the network structure had an insignificant effect on the fatigue life. These results demonstrate that longer mechanical fatigue lifetimes in double network rubbers are a consequence of their intrinsic orientation. This provides the capacity to retain crystallinity at the front of growing cracks, even in the absence of stress. The origin of the improved fatigue resistance is similar to the mechanism responsible for the better performance of strain-crystallizing rubbers subjected to non-relaxing cyclic deformations.
A Morphometric Investigation by TEM/AIA on Elastomer-Based Compounds Filled with an Untreated Precipitated Silica
Authors: Falqui L. , Costa G. , Castellano M. , Turturro A. , Valenti B. 
Published: February 2011

Abstract
An accurate morphological investigation has been carried out on vulcanized compounds based on different matrices, butadiene rubber, natural rubber and styrene-butadiene rubber, filled with 35phr of a precipitated silica. The analysis has been performed by using transmission electron microscopy (TEM) and automated image analysis (AIA) to achieve quantitative information on the filler dispersion. Significant differences in the aggregate size and shape distribution of silica within the different matrices which, in principle, can be related to the polymer-filler interactions, have been found. The results are in a very satisfactory agreement with thermodynamic predictions obtained by inverse gas chromatography. The use of two complementary techniques, TEM/AIA, allows attainment, in a reasonably short time, quantitative information on the filler dispersion and, consequently, on the performances of these elastomers-based composite materials.
Continuous Mixing and Compounding of Polymer/Filler and Polymer/Polymer Mixtures with the Aid of Ultrasound
Authors: Isayev A. I. , Hong C. K. , Kim K. J. 
Published: February 2011

Abstract
High power ultrasound is applied to break down silica agglomerates in EPDM/silica mixtures and to compatibilize plastic/rubber and rubber/rubber blends during extrusion process. Ultrasonically treated EPDM/silica mixtures without silane treatment of silica indicated significantly reduced sizes of silica agglomerates in comparison with those obtained by an internal mixer and lower than the EPDM/silica mixtures treated by the silane. The viscosity of the ultrasonically treated mixtures was found to be higher than that of the silane treated mixtures, while the extrudate swells of both mixtures were close to each other. Ultrasonically treated plastic/rubber and rubber/rubber blends indicated in-situ copolymer formation and compatibilization in the melt state leading to significant enhancement of the mechanical properties of the blends. An idea is put forward about the possibility of in-situ copolymer formation at the interfaces and their vicinities in the ultrasonically treated blends during extrusion. Data obtained by a solvent extraction indicating reduction in the amount of the extractable component, gel permeation chromatography indicating formation of the high molecular weight tail, atomic force microscopy indicating smooth interfacial region and scanning electron microscopy indicating stabilization of the phase morphology in the melt state of the ultrasonically treated blends point towards the occurrence of in-situ copolymer formation. The discovery creates a new field of the study of ultrasonic-assisted mixing of rubber with filler and compatibilization of immiscible polymer blends during extrusion.
Atomic Force Microscopy Studies on Morphology and Distribution of Surface Modified Silica and Clay Fillers in an Ethylene-Octene Copolymer Rubber
Authors: Ray Sudip , Bhowmick Anil K. , Bandyopadhyay S. 
Published: February 2011

Abstract
Topographic and phase imaging in tapping mode atomic force microscopy (TMAFM) has been performed to investigate the effect of surface modification of silica and clay fillers on the morphology and the microdispersion of the filler particles in the rubber matrix. The above fillers have been modified by using surface coating agents like an acrylate monomer (trimethylolpropane triacrylate, TMPTA) or a silane coupling agent (triethoxy vinylsilane, TEVS) followed by electron beam modification at room temperature. Both unmodified and surface modified fillers have been incorporated in an ethylene-octene copolymer rubber. The phase images of the above composites elucidate the reduction in aggregate size due to the filler surface modification, which is more pronounced in the case of silane modification. The results obtained from the section analysis and the histogram of the filler distribution further corroborate the above findings. The corresponding topographic images are characterized by various statistical quantities like roughness parameters and two-dimensional power spectral density (2-D PSD). As compared to the control silica and clay filled rubbers, a noticeable reduction in the surface roughness is observed in the case of modified filled composites. Thus, the whole study based on AFM suggests that the surface modification of the above fillers significantly reduces the filler-filler interaction, which in turn reduces the filler aggregate size and helps in improving the filler dispersion.