bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractal Structures in Carbon Black Reinforced Rubbers
Authors: Klüppel Manfred , Heinrich Gert 
Published: February 2011

Abstract
This paper considers the fractal nature of primary and secondary carbon black aggregates in rubber and the implications for the mechanical and electrical properties of rubber goods. In particular, the effects of dispersion and primary aggregate breakup during mixing are investigated. Founded on recent studies of the disordered growth processes of colloids, a model concerning formation, structure and properties of tenuous secondary carbon black aggregates (clusters) in rubber is formulated. We distinguish between two different mechanisms of cluster growth at carbon black concentrations ϕ below and above the gel point ϕ** of the filler network. For ϕ≤ϕ**, the restricted mobility of the dispersed primary aggregates governs the cluster growth and neighboring clusters are seperated by a rubber-specific minimum distance d0. These gaps between neighboring clusters are joined together in a bond percolation model that determines the conductivity in a transition regime ϕ*≤ϕ≤ϕ** above the electrical percolation threshold ϕ*. The mechanical action of carbon black clusters below the gel point ϕ** is estimated by a hydrodynamical amplification factor that is related to a rigidy condition for the clusters. At sufficient large filler concentration for ϕ≥ϕ**, the restricted mobility of primary aggregates in the rubber matrix is insignificant for the cluster growth and a kinetic cluster by cluster aggregation (CCA) process is applied. The resulting fractal carbon black network corresponds to a spacefilling configuration of CCA-clusters. From this network structure, a scaling invariant power law arises for the small-strain modulus as function of carbon black concentration. The conductivity in the networking regime ϕ≥ϕ** shows a typical power law behavior that is implied by an anomalous diffusion of the charge carriers on the fractal clusters. For the frequency dependence of the conductivity a cross-over to a power law regime at large frequencies results. The predicted properties of carbon black filled rubbers are discussed in the framework of experimental results taken from different authors.
Deformation of Filler Morphology in Strained Carbon Black Loaded Rubbers. A Study by Atomic Force Microscopy
Authors: Maas S. , Gronski W. 
Published: February 2011

Abstract
The changes of the filler morphology of SBR vulcanizates loaded with 10 phr carbon black (N234 and N990) subjected to large strains were studied by Atomic Force Microscopy and image analysis. It was found that the filler particles tend to align in the force field. The average distance of the filler particles at the surface in the direction parallel and perpendicular to the strain direction is much smaller then according to affine deformation. The measurements give evidence of the inhomogeneous deformation of the rubber matrix and demonstrate the onset of failure at large deformation.
The Technological Compatibilization of Natural Rubber/Polystyrene Blends by the Addition of Natural Rubber-graft-Polystyrene
Authors: Asaletha R. , Thomas Sabu , Kumaran M. G. 
Published: February 2011

Abstract
Compatibility of natural rubber (NR)/polystyrene (PS) blend is poor and can be enhanced by the addition of a graft copolymer of natural rubber and polystyrene (NR-graft-PS). The effects of homopolymer molecular weight, copolymer molecular weight, copolymer concentration, processing conditions and mode of addition on the morphology of the dispersed phase have been investigated by means of optical microscopy. The addition of a small percentage of the compatibilizer decreases the domain size of the dispersed phase. The effect levels off at higher concentrations. The leveling off could be an indication of interfacial saturation. The experimental results were compared with the theoretical predictions of Noolandi and Hong. The addition of the graft copolymer improves the mechanical properties of the blend and attempts were made to correlate the mechanical properties with the morphology of the system. Attempts were also made to understand the conformation of the graft copolymer at the interface.
Rheological Studies of Dynamically Vulcanized and Mechanical Blends of Polypropylene and Ethylene-Propylene Rubber
Authors: Han Peter K. , White James L. 
Published: February 2011

Abstract
An experimental study is presented of the rheological properties of (i) polypropylene, (ii) a commercial polypropylene/ethylene-propylene terpolymer a dynamically vulcanized blend (PP/EDPM-TPE) and (iii) a mechanical blend of a polypropylene and an ethylene-propylene copolymer. The polypropylene behaves as a typical flexible chain thermoplastic exhibiting a zero shear viscosity and higher shear rate non-Newtonian viscosity, well defined normal stresses, an elongational viscosity three times the zero shear viscosity, and an equality of the shear viscosity and the complex viscosity (Cox-Merz Rule). The PP/EPM-TPE exhibits an apparent yield value in shear flow, unmeasurable normal stresses and a complex viscosity which is much greater than the shear viscosity. This is behavior similar to that of particle filled compounds, block copolymers and liquid crystalline thermoplastics and suggests a material with a rest state structure. The behavior of the PP/EPM mechanical blend is intermediate.
Sulfur/Olefin Copolymers as Vulcanizing Agents for Rubber
Authors: Colvin Howard , Bull Charles 
Published: February 2011

Abstract
Sulfur/olefin copolymers are known as vulcanizing agents for rubber, but synthetic procedures for these materials are poor and there is little in the literature to relate the structure of the copolymer with the vulcanizate properties of the rubber. This study discusses a new suspension process for the preparation of sulfur/dicyclopentadiene and sulfur/dicyclopentadiene/styrene copolymers. The relationship between the sulfur/olefin copolymer and vulcanizate properties is discussed in terms of the structure of the copolymer and other reaction products.
Direct Analysis of Elastomer Compounds by Soft Ionization, Tandem (MS/MS) and High Resolution (AC-MS) Mass Spectrometry
Authors: Lattimer Robert P. 
Published: February 2011

Abstract
In recent years very effective mass spectrometric methods have been developed for direct polymer compound analysis. The high sensitivity, high specificity, and superb mixture analysis capabilities of modern mass spectrometry make it an invaluable tool in the polymer industry, particularly for qualitative analysis (chemical identification) of organic additives as well as polymeric components. “Survey” mass spectra obtained with soft ionization methods — field ionization (FI-MS) and chemical ionization (CI-MS) — provide diagnostic overviews of chemical composition. The supplemental tandem (MS/MS) and atomic composition (AC-MS) techniques are used to make specific identifications of various organic ingredients. This report describes the direct mass spectrometric analysis of three different elastomer compounds. Organic additives, including curatives, were identified via thermal desorption methods in a commercial EPDM bearing as well as a diene rubber V-belt. The composition of a commercial thermoplastic polyurethane was determined via pyrolysis (Py-CI-MS). These problem-solving examples illustrate the very effective role that mass spectrometry can play in the industrial polymer analysis laboratory.
Correlation between Laboratory and Road Rubber Wear Tests
Authors: Krishnan V. , Ramakrishnan R. , Donovan J. A. 
Published: February 2011

Abstract
The wear resistance ranking of three rubber compounds A, G and K measured in the laboratory at medium to high slip on sharp silicon carbide (SiC) grinding wheels was similar to that determined by road tests at Pecos, Texas. The wear resistance ranking of the three compounds changed on blunt alumina grinding wheels compared to wear resistance rankings on sharp SiC grinding wheels. The change was most probably due to a change of mechanism from mainly cutting on sharp surfaces to predominantly fatigue on blunt surfaces. For these three compounds a change in the ambient temperature from 23 to 75°C during laboratory testing had no effect on the wear resistance ranking. The wear of the rubber compounds on the abrasive grinding wheels and during road tests followed Zapp's relation in which the wear is proportional to the ratio of dynamic modulus to rupture energy.
Influence of Aggregate Structure and Matrix Infiltration on the Dispersion Behavior of Carbon Black Agglomerates
Authors: Li Qi , Feke D. L. , Manas-Zloczower I. 
Published: February 2011

Abstract
The dispersion of carbon black agglomerates in poly(dimethyl siloxane) (PDMS) has been studied experimentally. Both the structure of carbon black aggregates comprising the agglomerate and the presence of the matrix within the agglomerate were found to affect the mode of dispersion, critical stress conditions, and the kinetics of the dispersion process. Agglomerates of high structure carbon black are generally more difficult to disperse than agglomerates of low structure carbon black at the same agglomerate density. Depending on the degree of saturation of the agglomerate by PDMS, the dispersion process may be either enhanced or retarded compared to the dry state.
Silica and Silane Coupling Agent for in Situ Reinforcement of Acrylonitrile-Butadiene Rubber
Authors: Murakami K. , Osanai S. , Shigekuni M. , Iio S. , Tanahashi H. , Kohjiya S. , Ikeda Y. 
Published: February 2011

Abstract
In situ silica reinforcement for the acrylonitrile-butadiene rubber (NBR) vulcanizates, which were premixed with a conventional silica (VN-3) and γ-mercaptopropyltrimethoxysilane (γ-MPS), was achieved by the sol-gel reaction of tetraethoxysilane (TEOS) using ethylenediamine. It was observed that the reinforcement efficiency tended to increase with the increase of mechanically premixed conventional silica. From the observations of transmission electron microscopy and scanning electron microscopy, the simultaneous use of VN-3 and γ-MPS was found to promote the formation of large silica particles and clusters with a relatively good dispersion by the sol-gel reaction of TEOS in the NBR vulcanizate. The results of hysteresis measurements supported this promotion. It was considered to be due to the surface modification of VN-3 by the sol-gel reaction of TEOS and the presence of γ-MPS which worked as a dispersion agent for silica particles. The relationship between the mechanical properties and the morphology of the in situ silica filled vulcanizates is discussed.
Basic Study of Continuous Ultrasonic Devulcanization of Unfilled Silicone Rubber
Authors: Diao B. , Isayev A. I. , Levin V. Y. 
Published: February 2011

Abstract
The present paper describes a basic study of the devulcanization of unfilled model silicone rubber vulcanizates using a continuous ultrasonic reactor. The devulcanization was conducted under several processing conditions. Cure behavior, rheological properties, structural characteristics of the devulcanized rubber, and mechanical properties of revulcanized rubbers were studied. Gel fraction and crosslink density measurement indicate that the rubber is partially devulcanized. The gel permeation chromatography (GPC) results imply that the creation of a branched structure in the network is a possibility after devulcanization. Under the optimal devulcanization condition, the mechanical properties of revulcanized rubber are better than those of the virgin rubber. Devulcanized silicone rubber was also blended with the virgin one. The blends show the same tensile strength and modulus as the virgin rubber but higher elongation.
Homogeneous Zinc(II) Catalysis in Accelerated Vulcanization II. (Poly)Olefin Oxidation, Dehydration, and Reaction with Anti-Reversion Coagents
Authors: Nieuwenhuizen Peter J. , Haasnoot Jaap G. , Reedijk Jan 
Published: February 2011

Abstract
This paper establishes a new and previously unrecognized pathway for the formation of dienes and trienes from model 1,5-polyolefins. It has been found that in the presence of dioxygen and at high temperatures model 1,5-polyolefins are oxidized to yield allylic alcohols or hydroperoxides. These structures subsequently dehydrate to form dienes and trienes, a reaction which was found to be catalyzed by bis(dimethyldithiocarbamato)zinc(II) (ZDMC) and bis(mercaptobenzothiazolato)-zinc(II) (ZMBT), but not by zinc stearate. The observed dehydration reaction has been established to occur exclusively via a 1,2-dehydration pathway; whereas 1,4-dehydration was not observed. In addition, the present paper reports that NBCI, a model compound for the anti-reversion agent 1,3-bis(citraconimidomethyl)benzene (BCIMB), reacts completely within 2 h with squalene at 170 °C in the absence of vulcanization curatives, which can be attributed to this oxidation/dehydration mechanism. The combined results suggest that the occurrence of dienes and trienes in vulcanized rubber may in part be caused by oxidation of the rubber backbone and subsequent dehydration.
Reactions of 2-t-Butylbenzothiazole Sulfenamide with Sulfur and Zinc Oxide in the Absence of Rubber
Authors: Gradwell M. H. S. , van der Merwe M. J. 
Published: February 2011

Abstract
The interaction of sulfur, ZnO and 2-t-butylbenzothiazole sulfenamide (TBBS) was investigated by differential scanning calorimetry (DSC) in the absence of rubber. Special reference was made to the role of the amine, the distinguishing characteristic of all sulfenamides. TBBS decomposes rapidly at 211 °C, the major products being 2-bisbenzothiazole-2,2′-disulfide (MBTS) and 2-bisbenzothiazole-2,2′-monosulfide (MBTM). High mass losses occured and very little free amine was found at these high temperatures. The major degradation products of the TBBS/sulfur system were MBTS, 2-bisbenzothiazole-2,2′-polysulfides (MBTP) and 2-t-butylaminobenzothiazole polysulfides (TBBP). Little free amine and very small mass losses were found. Reaction mechanisms were proposed to account for the formation of the products.
Insights into Sulfur Vulcanization from QSPR Quantitative Structure-Property Relationships Studies
Authors: Ignatz-Hoover Fred , Katritzky Alan R. , Lobanov Victor S. , Karelson Mati 
Published: February 2011

Abstract
Vulcanization of styrene-butadiene rubber, as accelerated by a series of sulfenamides and sulfenimides prepared from various aromatic heterocyclic thiols and various aliphatic amines, was studied using the curemeter under isothermal conditions. Further studies using MOPAC AM1 semiempirical quantum mechanical calculations and CODESSA QSAR software yielded excellent correlations of molecular descriptors of accelerators or accelerator thiolate zinc complexes to the onset of cure and maximum rate of vulcanization. The QSAR results support previously proposed mechanisms describing the origin of scorch delay for the delayed action, fast curing sulfenamide accelerators. In addition, the results support a carbanionic concerted mechanism for the sulfurization and crosslinking reactions.
Topology of Wear Particles
Authors: Padovan Joe , Prasad Neelesh , Gerrard David , Park S. W. , Lindsley Ned 
Published: February 2011

Abstract
This paper describes the evolution of elastomer/rubber wear debris morphology from the in situ leading to trailing edges of sliding contacted wear surfaces. Special attention is given to establishing the role of grit size, slip rate, and contact length on the formation of wear particles, as well as the subsequent in situ aggregation of such product into a hierarchy of particulate material. Of specific interest is the determination of the in situ mass/number count partitioning between true wear particles and aggregates. This population balance is achieved by establishing and monitoring the morphological signature of the various particle types as one moves along various in situ positions to the wake location. The validity/reliability of the empirical trends obtained are verified through the use of the appropriate statistical measures.
An Approach to Chemorheology of a Filled SBR Compound
Authors: Ding R. , Leonov A. I. 
Published: February 2011

Abstract
Three steps in complex chemorheological studies are necessary for complete rheological characterization of filled rubbers during cross-linking reaction. They include: (i) kinetic studies of cross-linking reaction, (ii) rheological studies of green rubber compounds, and (iii) correlation between the rheological parameters and the degree of cure. Basic experiments in the steps (i)–(iii) and their modeling are presented in this paper on the example of a filled SBR compound with sulfur accelerated vulcanization. The approach provides a unique possibility to trace therheological properties of rubber compounds from the green to completely cured states.
Strain-Dependent Dynamic Properties of Filled Rubber: A Non-Linear Viscoelastic Approach Based on Structural Variables
Authors: Lion Alexander 
Published: February 2011

Abstract
This essay deals with a general framework based on the phenomenological theory of non-linear thermoviscoelasticity to represent the characteristic strain dependence of dynamic moduli of carbon black-filled vulcanizates (Payne effect). By virtue of thermodynamical arguments we develop a one-dimensional model consisting of non-linear springs and damping elements. We introduce viscosity functions depending not only on the temperature but on other variables besides. They can be related to the current state of the material's microstructure. Under dynamic loads and stationary conditions, these variables become approximately constant so that the model can be simplified. One of the main results is that the reduced set of equations becomes comparable to linear viscoelasticity but the structural variables imply a dependence of the viscosities on the deformation amplitude. It follows from our theory that the amplitude-dependent parts of storage and dissipation modulus are not independent of each other, as frequently assumed. Both moduli depend in a characteristic manner on the strain amplitude. If we assume, for example, a decreasing power-law relation between viscosities and structural variables, the theory reduces to the widely-accepted G′(Δε) and G′″(Δε) models proposed by Kraus and substantiated by Huber and Huber et al. If we introduce an additional mechanism of exponential-type we obtain the improved G′″(Δε) model developed by Ulmer. Under transient conditions with varying strain amplitudes, as studied experimentally by Wang et al., the model describes thixotropic recovery effects of the moduli as well as more complicated memory phenomena. Under further assumptions we can apply the frequency/temperature shift principle in combination with a frequency/amplitude shift principle to determine the material parameters. Since the model is based on rheological elements, its compatibility with the second law of thermodynamics is ensured.
Stresses, Slip and Abrasion of Rubber Covered Conveyor Rollers
Authors: Metlikovič Peter , Meinecke Eberhard A. 
Published: February 2011

Abstract
Conveyors consist of rubber coated, fiber reinforced belts which are supported and driven by rollers. The rollers are generally coated to increase and stabilize the friction and to reduce abrasion, noise and dirt buildup. Pressures and shear stresses in the rubber layer depend on belt tension, driving forces, geometry and material properties of belt and roller. Most rollers fail due to abrasion when the shear stresses are higher than the friction forces. Slip due to pressure between the belt and the rubber layer is proportional to pressure. Additional slip arises from troughing transitions, uneven belts and rollers and from driving forces. Abrasion due to slip is proportional to the pressure of the belt to the power 1.5 to 3. Equations to predict stresses, slip and abrasion are presented. To reduce abrasion rates, conveyors should have large diameter rollers, low belt tension and a wide belt. Also, cylindrically machined pulleys, high quality belts and long troughing transitions should be employed.
Glass Transition of Elastomers Using Thermal Analysis Techniques
Authors: Sircar A. K. , Galaska M. L. , Rodrigues S. , Chartoff R. P. 
Published: February 2011

Abstract
The paper defines the glass transition temperature (Tg) of elastomers using various thermal analysis techniques (differential scanning calorimetry, DSC; derivative DSC; thermomechanical analysis, TMA; dynamic mechanical analysis, DMA; dielectric analysis, DEA; thermal stimulated current, TSC) and compares Tg values of eight elastomers by the first four techniques. Comparison of Tg by two TMA methods (expansion and penetration) is also included. Necessary information regarding both the specific technique and the sample used to compare published data is mentioned. Their inclusion, along with the Tg data, is emphasized. Correlation of Tg, as determined by thermal methods with that determined by an industrial low-temperature test method (ASTM D 1053-89a) is discussed. The factors that are unique to elastomer Tg determination, such as subambient operation, as compared to other polymers, are pointed out.
Ethylene—Styrene Copolymerization
Authors: Pellecchia Claudio , Oliva Leone 
Published: February 2011

Abstract
Ethylene—styrene copolymers are new materials developed within the last decade using the new homogeneous olefin polymerization catalysts (generally referred to as “metallocene catalysts”). By proper selection of the catalytic system and the reaction conditions, a variety of copolymers with different compositions, structures, and properties can be obtained. Thus, copolymers containing a very low amount of styrene (or p-methylstyrene) on a substantially polyethylenic backbone are crystalline thermoplastics, which could be used to produce functionalized PEs. Increasing the styrene content leads to a rapid decrease in the crystallinity, affording materials which show good thermoelastomeric properties. Copolymers containing around 20 mol % styrene are effective compatibilizers for polyethylene—polystyrene blends. The molecular structure of these copolymers has been defined being “pseudorandom,” since EEE, EES, ESE, and SES sequences are observed, and no SS sequences are present, thus the styrene content cannot exceed 50 mol %. Very recently, however, a random copolymer containing SS sequences in a stereoregular arrangement has been reported. Also, truly alternating E-S copolymers have been obtained with suitable catalysts. These poly(ethylene-alt-styrenes) can be either atactic (and thus amorphous) or stereoregular, depending on the particular catalyst used. Interestingly, isotactic poly(ethylene-alt-styrene) is a new crystalline material with a melting point of 145 °C, whose crystal structure has recently been determined. In conclusion, further research on ethylene—styrene copolymerization promises to afford a variety of new interesting materials starting from two widespread, easily available and inexpensive monomers.
Thermodynamic Interactions in Blends of Polydienes
Authors: Krishnamoorti Ramanan 
Published: February 2011

Abstract
Thermodynamic interactions and phase behavior in binary blends of model mixed microstructure polybutadienes with model 1,4-polyisoprene were studied using small angle neutron scattering and differential scanning calorimetry (DSC). The microstructure of the polybutadiene ranged from 8% 1,2 (92% 1,4) to 90% 1,2 (10% 1,4) units, while the polyisoprene contained 93% 1,4 and 7% 3,4 units. The blends of protonated polybutadienes (HPB) with deuterated 1,4 polyisoprene (DPI) exhibited lower critical solution temperature (LCST) behavior when the polybutadiene contained 38 mol % or more of 1,2 units. Below this 1,2 content of the polybutadiene, all HPB/DPI blends were found to be phase separated at all temperatures above 25 °C. The DSC measurements revealed that other than a blend containing 8% 1,2-polybutadiene and (protonated) 1,4 polyisoprene, all other blends were single phase at room temperature. These results are understood in the context of previous work performed by Han and coworkers on deuterated polybutadiene-protonated polyisoprene blends.