bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of Chemiluminescence in Rubber Research
Authors: Forsström Dan , Kron Anna , Mattson Bengt , Reitberger Torbjörn , Stenberg Bengt , Terselius Björn 
Published: February 2011

Abstract
The oxidation of most organic materials is accompanied by the emission of weak light, so called chemiluminescence (CL). This emission has previously often been designated oxyluminescence. CL has been known for several years, but it is not until recently that the development of photon counting equipment has allowed detection of levels down to a few photons per second. This development makes CL a promising nondestructive and extremely sensitive technique to provide data which may be useful to estimate the service life of polymeric materials. Various applications of the CL-method for the detection of oxidation of elastomers are reported: such as, stabilization of hydroxyl-terminated polybutadiene; degradation of latex coating of paper; long-term thermo-oxidation of natural rubber; indication of ultrathin coating of cellulose fiber with polybutadiene.
Applications of FT-NMR to Crosslink Density Determinations in Natural Rubber Blend Vulcanizates
Authors: Brown Paul S. , John M. , Loadman R. , Tinker Andrew J. 
Published: February 2011

Abstract
Previously 90 MHz CW-NMR spectroscopy has been used to estimate the crosslink density in individual components of elastomer blends. Transfer of the technique to a 300 MHz FT instrument is not straightforward. Chemical shifts of polymer resonances in spectra of single-polymer vulcanizates are dependent on crosslink densities of the vulcanizates. Additionally, two resonances are observed for small molecules such as TMS and residual protonated solvent. The smaller resonance of each pair changes in shape and position in synchrony with the polymer signals and is considered to originate from solvent within the swollen polymer. The secondary TMS peak is used as the reference position from which to locate polymer signals in the spectrum. The position of these secondary peaks, and thus the polymer spectrum, relative to the “free” TMS is a function of crosslink density and also of carbon-black loading and type in filled vulcanizates. 13C-NMR line widths are observed to increase with crosslink density and this effect was used to study blends of NR with EPDM or a maleic acid modified EPDM. NR crosslink densities determined from 13C line-width analyses were in good agreement with those obtained from 1H-NMR and increased crosslinking in the modified EPDM was confirmed.
The Mechanical Properties of a Thermoplastic Elastomer Produced by the Bacterium Pseudomonas oleovorans
Authors: Gagnon K. D. , Lenz R. W. , Farris R. J. , Fuller R. C. 
Published: February 2011

Abstract
PHO, a poly(β-hydroxyalkanoate) copolymer containing mostly β-hydroxyoctanoate repeating units, was produced in a fed batch fermentation process by Pseudomonas oleovorans when grown on sodium octanoate as the sole carbon source. The polymer from different batches—evaluated with regards to composition, molecular weight distribution, thermal transition temperatures, and decomposition temperature—was found to be highly consistent batch-to-batch. Polymer composition as a function of growth time did not change significantly once the culture reached the stationary growth phase. PHO when crystallized at room temperature from the melt, forms a physically crosslinked network with the crystalline regions acting as the physical crosslinks. The molecular weight between physical crosslinks was determined to be approximately 4000. The stress-strain properties, hardness, and tensile set of PHO were found to be within the range of values defined by a variety of commercially available thermoplastic elastomers with differing chemical structures. The tensile set of PHO was high, 35% after 100% elongation. Experimental evidence supports three possible sources of the high tensile set: permanent strain-induced orientation or displacement of the physical crosslinks, irreversible strain-induced crystallization, and deformation-induced changes of the size and purity/perfection of crystalline regions.
Simulation of the Breakup of Dense Agglomerates in Simple Shear Flows
Authors: Horwatt Steven W. , Manas-Zloczower Ica , Feke Donald L. 
Published: February 2011

Abstract
The transmission of stress within an agglomerate and hence the stress required for the agglomerate breakup is strongly dependent on the agglomerate structure. In this work, the influence of agglomerate structure on the dispersion process has been investigated through the use of computer simulations. Two different particle-particle agglomeration mechanisms, similar to the conditions under which carbon black is pelletized, have been used in this study. The linear trajectory agglomeration mechanism results in highly branched structures having a dense core, while the Eden model results in very dense clusters exhibiting rough surfaces but little internal porosity. The critical stresses to initiate dispersion of these structures, as well as the fragment size distributions resulting from the application of a simple shear flow field at stresses in excess of the critical value, were simulated. The results show that for the highly ramified agglomerates, the amplification of stress at the roots of the branches in the structure is controlling the dispersion process, whereas for the dense, unbranched agglomerates, the presence of strength-limiting flaws determines the breakup behavior. The results of the simulations were compared to previously performed experimental studies of dispersion for carbon-black agglomerates.
The Dispersion of Carbon Black in Rubber Part III. The Effect of Dispersion Quality on the Dynamic Mechanical Properties of Filled Natural Rubber
Authors: Coran A. Y. , Donnet J-B. 
Published: February 2011

Abstract
The Part I of this series described a rapid method for determining the quality of carbon-black dispersion. The second paper (Part II) was concerned with the kinetics of the dispersion of carbon black into natural rubber (dispersion quality as a function of mixing time) in an internal mixer. In this paper we consider the effects of changes in dispersion quality on the dynamic mechanical properties of both unvulcanized and vulcanized natural rubber. The effects of changes in the degree of carbon-black dispersion were measured by using a new prototype moving-die rheometer (which is presently being developed at Monsanto Instruments & Equipment Research Laboratory). By using this prototype rheometer, G′ and G″ were measured as functions of shear-strain amplitude, temperature, and frequency. Increases in the degree of carbon-black dispersion in uncured natural rubber (starting from very poor dispersion quality) give decreases in the values of both G′ and G″. The decrease in dynamic moduli with increases in the degree of carbon-black dispersion might be explained on the basis of a network of agglomerates which exists when the quality of dispersion is extremely poor. In the case of uncured samples, values of G′, measured at low strains (e.g. ±1%), become reduced after the imposition of a larger (±50%) sinusoidal shear strain for a short period of time (e.g. 3 s). Then, with the passage of time, the reduced value of G′ partially recovers. The extent of this recovery increases with increases in the dispersion rating DR. Similar results were obtained with respect to the loss modulus G″. In both cases, the extent of recovery is much less when the carbon black is very poorly dispersed. The unrecoverable proportion of G′ or G″ is also considered to be due to a network composed of mutually interactive agglomerates of carbon black.
Mill Processing Behavior of Polychloroprene and Acrylic Rubbers
Authors: Kumar Nalini R. , Bhowmick Anil K. , Gupta B. R. 
Published: February 2011

Abstract
Mill processing behavior, with respect to front to back roll (F-B) transition, of polychloroprene and acrylic rubbers has been studied. The critical nip gap at which F-B transition occurs has been determined for these rubbers and their filled compounds (including HAF, MT, silica, and whiting) over a range of friction ratios and temperatures. The nip gap increases with friction ratio and temperature. The theoretical model of Tokita based on dimensional analysis, reveals three conditions corresponding to three types of behavior of various rubbers in drop mill operation. Mill band formation indices corresponding to these behavior types have been defined. These indices can be used to determine the conditions for front roll band formation. The systems investigated satisfy one of the conditions of the model. The mill processing behavior of these systems in a continuous milling operation has also been reported.
Spin-Spin Motional Analysis of Accelerated Sulfur Vulcanized Cis-Polyisoprene
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
Spin-spin relaxation (T2) measurements were used to analyze the motional behavior of accelerated-sulfur vulcanized cis-polyisoprene. Biexponential decay behavior was found in all samples studied. This was modeled to consist of T2s (short) and T2l (long) components, with the T2s due to crosslinked regions and T2l due to regions distant from nodal points. T2 behavior was shown to depend strongly on crosslink density, but not to vary with concentration of cyclic structures. A simplified model was used for calculation of the average correlation time.
The Effect of Mold Pressure on the Electrical Resistivity of Elastomers
Authors: Thompson Corley M. , Allen J. Scott 
Published: February 2011

Abstract
Elastomers are commonly used as electrical insulators in marine acoustic devices. A previous paper discussed the very large decrease in electrical resistivity of a Neoprene GRT formulation when subjected to moderately high molding pressures. In the present paper, data will be presented showing similar dependencies on mold pressure for natural, polybutadiene, 39%-acrylonitrile NBR, and chlorobutyl elastomers and the absence of the effect for an EPDM, and a 27%-acrylonitrile NBR elastomer. These data are not easily explained. The previous paper also discussed that increasing the carbon-black loading caused the electrical resistivity to decrease at even lower molding pressures. Similar trends are presented here for the other elastomers whose electrical resistivities are dependent on molding pressure. Data will also be presented that show that the addition of poly-para-dinitrosobenzene (Poly DNB®) to a CR formulation will eliminate the mold pressure vs. electrical resistivity effect.
Universal Relationship between Abradability and Breaking Energy, Shear Loss Modulus, and Ridge Spacing
Authors: Thavamani P. , Bhowmick Anil K. 
Published: February 2011

Abstract
An attempt is made here to find a universal relationship between abradability and breaking energy, shear loss modulus and ridge spacing per unit frictional force for a series of filled and unfilled rubbers (NR, SBR, and HNBR) tested under a variety of experimental conditions.
Effects of Temperature on Fatigue and Fracture
Authors: Young D. G. , Danik J. A. 
Published: February 2011

Abstract
Although fatigue tests at varied temperatures are not common due to the added burden of testing, there are times when variable temperature testing is important to ensure that rubber compounds will be suitable for the full range of use conditions. This is particularly true when materials with high Tg(&gt;−50°C) are being considered for use in tires. Results for two high Tg rubber compounds (ECO and HS-SBR) showed fatigue crack growth (FCG) rates that were roughly 100 times those of a BIIR liner compound over the temperature range of −25 to 100°C. Additional tests with BIIR and NR showed that most crack growth results for temperatures of −25 to 100°C, and various strains, followed similar fatigue functions (dc/dn vs. T). The exception was some data for NR at 0 and −25°C which showed inhibited rates of FCG due to strain crystallization. There appears to be a window of strain rate, temperature and strain level where this effect is noticed, but these results need to be confirmed for NR and other strain crystallizable elastomers. Two fully cured NR belt skims used in truck tires showed linear results for log dc/dn vs. log T at temperatures of 70 to 100°C. However, undercured samples of one compound exhibited more temperature sensitivity of FCG results; specifically, rates of FCG increased significantly with temperature at low strain levels. This suggests the need for further evaluation of the effect of cure state on FCG over a range of test temperatures.
Universal Properties in Filler-Loaded Rubbers
Authors: Kilian H. G. , Strauss M. , Hamm W. 
Published: February 2011

Abstract
Stress-strain cycles in filler loaded rubbers can be described with the aid of the van der Waals-network model. Reinforcement comes about by drawing pairs of filler particles apart. Reinforcement is observed because the intrinsic strain within the rubber bridge which is located between the filler particles exceeds the macroscopic strain very much, so much that interfacial slippage is enforced. The rubbery intra-cluster bridge distribution is represented by three dominant filler particle distances. One of them describes direct filler-to-filler (FF-) contacts, the critical strength of which is different from the filler-to-matrix (FM-) contacts of the filler-to-filler chains which are located on the whole surface of the filler particles. Formation of clusters is described by a power law. Stress-strain experiments are described with the aid of this model for different filler-matrix combinations (NR, SBR, carbon blacks, silica). Many universal features are observed: The intra-cluster rubber bridges display the same mean thickness when being related to the radius of the primary filler particles. The exponent in the power law is always identical. The deformation mechanisms, including irreversible slippage, do not to depend on the type of strain (simple extension, uniaxial compression). Yet, the Einstein-Smallwood effect turns out to be anisotrop so far as quasipermanent filler-to-matrix interactions seem to be determined by normal forces in the particles surfaces only. Different filler and matrix combinations display different strengths of the FF- and FM-contacts independent of the type of strain.
Filler-Elastomer Interactions. Part XI. Investigation of the Carbon-Black Surface by Scanning Tunneling Microscopy
Authors: Wang Meng-Jiao , Wolff Siegfried , Freund Burkhard 
Published: February 2011

Abstract
Scanning tunneling microscopy (STM) has recently been demonstrated to be a powerful and versatile tool to image the microstructure of the surface of carbonaceous materials. In this study, the surfaces of carbon blacks, both graphitized and nongraphitized, were investigated with this technique. The STM images show that the carbon-black surface can be classified into two domains, an organized and an unorganized one. The degree of carbon atom organization varies with the carbon-black grade and increases drastically upon graphitization. The surface energies and energy distributions of graphitized and nongraphitized carbon blacks, measured by inverse gas chromatography, correlate well with their surface microstructure. Mapping of the carbon-black topography showed that although the surface is not smooth, there is no significant porosity either.
Mechanical Seal with Elastomeric Rotating Element. Part 2: Experimental Study
Authors: Rivkin Michael , Kholodenko Arnold 
Published: February 2011

Abstract
An innovative flexible faced mechanical shaft seal using common elastomeric materials was designed and tested to determine its friction coefficient at a wide range of temperatures and speeds, its rate of heat generation, and its feasibility for use in the process industry. The new seal was constructed using an elastomeric rotating element stretched over the sleeve to at least 20 percent of its original length and an unlapped silicon carbide stationary annular ring. It was found that the main advantage of the elastomeric seal is its ability to maintain stable lubrication with a fluid film considerably thinner than that of traditional hard face seals, and consequently achieve negligible net leakage. This is particularly significant with respect to control of volatile organic carbon emissions. An experimental device was designed for precise measurement of the friction coefficient as well as the long term friction behavior of seal pairs in a wide range of liquid pressure and temperature. The original data were obtained for friction coefficient of EPDM, HNBR, FKM, and TFE/P type elastomers in contact with silicon carbide in the temperature range 15–110°C, linear speeds 0–12 m/s, water pressure 0.15–0.40 MPa, and effective contact pressure 0.8–1.2 MPa. Experiments showed that the friction coefficient constantly grows, typically from 0.05 to 0.15 at sliding speeds of 2–12 m/s, with temperature increases from 15 to 70°C. The temperature behavior of the friction coefficient above 70°C greatly depends on the elastomer. For high temperature elastomers, such as FKM, the friction coefficient may decrease slightly at 70°C; whereas, for EPDM, it continues to increase as temperature increases.
Vulcanization Chemistry. Comparison of the New Accelerator N-t-Butyl-2-Benzothiazole Sulfenimide (TBSI) with N-t-Butyl-2-Benzothiazole Sulfenamide (TBBS)
Authors: Hann Cynthia J. , Sullivan Alfred B. , Host Brian C. , Kuhls George H. 
Published: February 2011

Abstract
The sulfur vulcanization chemistry of cis-polyisoprene formulations accelerated with N-t-butyl-2-benzothiazole sulfenimide (TBSI) is compared to the chemistry of equivalent formulations accelerated with N-t-2-benzothiazole sulfenamide (TBBS). High performance liquid chromatographic analysis (HPLC) is utilized to examine the kinetics of accelerator-sulfur disappearance and the formation-appearance profiles of extra-network cure intermediates across the vulcanization process for stocks with a wide range of sulfur/accelerator ratios. Some unique features of TBSI vulcanization that distinguish it from TBBS are defined. A major distinction is the apparent consecutive step-wise kinetics of accelerator decay across the vulcanization process. A sequential reaction process may be indicated. Evidence is also offered that BtSxBt(x=2→6) is the crosslink precursor in TBSI vulcanization just as with TBBS formulations.
Steady-State Shear Flow Properties of Carbon-Black Filled Rubber Compounds
Authors: Ertong S. , Eggers H. , Schümmer P. 
Published: February 2011

Abstract
The steady shear viscosities of four model rubber/carbon-black compounds are measured with a modified Weissenberg Rheometer in a range of moderate shear rates. Yield stresses and low-shear viscosities are determined from creep-flow experiments. Yield stresses are found to increase strongly with filler content while their dependence on temperature can be described by an Arrhenius-type function. Flow curves are reduced to master curves by means of the time-temperature superposition principle. The shift factors are well approximated by the WLF-relation. The contribution of the “secondary” carbon-black network to the viscoelastic behavior requires additional vertical shifting for the filled compounds. Viscosities are found to be in very good agreement with the Herschel-Bulkley model when using the experimentally determined yield values.
The Dispersion of Carbon Black in Rubber Part IV. The Kinetics of Carbon Black Dispersion in Various Polymers
Authors: Coran A. Y. , Ignatz-Hoover F. , Smakula P. C. 
Published: February 2011

Abstract
A rapid technique for evaluating the rate and state of dispersion of carbon black in natural rubber has been extended to study the dispersion of carbon black in various polymers. The technique measures the extent and rate of dispersion of the black in the rubber. The kinetics of dispersion was characterized for a variety of polymers (e.g. SBR, EPDM, IR, IIR, BR and NR). Kinetic parameters were correlated with molecular weight and molecular weight distribution.
Sulfur Vulcanization of Simple Model Olefins, Part II: Characterization and Reactivity of Intermediate Vulcanization Products of 2,3-Dimethyl-2-Butene
Authors: Versloot P. , Haasnoot J. G. , Reedijk J. , van Duin M. , Duynstee E. F. J. , Put J. 
Published: February 2011

Abstract
In a study of the mechanism of the sulfur vulcanization of unsaturated rubber, 2,3-dimethyl-2-butene (C6H12) was used as a simple, low-molecular model alkene. Only equivalent allylic positions are present in this alkene. Treating C6H12 with a mixture of ZnO, S8 and the accelerator tetramethylthiuramdisulflde at 140°C for 20 minutes yields a mixture of addition products (C6H11—Sn—C6H11) and also intermediate products (C6H11—Sn—S(S)CN(CH3)2). The formation of C6H11—Sn—C6H11 from these intermediate products only proceeds in the presence of the zinc dimethyldithiocarbamate complex and free alkene.
Minimizing Nitrosamines Using Sterically Hindered Thiuram Disulfides/Dithiocarbamates
Authors: Layer Robert W. , Chasar Dwight W. 
Published: February 2011

Abstract
Sulfenamide accelerators and sulfur donors based on secondary amines must liberate all of their amine in order to function. Consequently, they are capable of producing relatively large amounts of nitrosamines. Thiuram disulfides and dithiocarbamates, on the other hand, only liberate their amines because of undesired side reactions. Accordingly, compared to sulfenamides, they produce significant, but much lower levels of nitrosamines during the cure. In an effort to reduce these side reactions, and thus the amount of nitrosamine which forms, we investigated the effect of steric factors on nitrosamine formation. We find that thiurams and dithiocarbamates made from sterically bulky amines, like diisobutylamine, produce orders of magnitude lower levels of nitrosamine than TMTD. At the same time, when used as a kicker for 2-benzothiazole sulfenamides, N,N,N′,N′-tetraisobutylthiuram disulfide has better scorch safety but cures at the same rate as TMTD. Uniquely, N,N,N′,N′-tetraisobutylthiuram monosulfide acts as a retarder as well as a kicker for 2-benzothiazole sulfenamides.
A Review of Methods to Characterize Rubber Elastic Behavior for Use in Finite Element Analysis
Authors: Charlton D. J. , Yang J. , Teh K. K. 
Published: February 2011

Abstract
The purpose of this paper is to provide a review of methods used to characterize the elastic behavior of rubber for use in Finite Element Analysis (FEA). A sample of elastic strain energy density functions used to characterize rubber is given, along with the tests required to characterize rubber according to these functions. The use of synthetic test data as an alternative to full physical testing is discussed, and highlighted by a case study. The paper closes with a discussion on potential errors associated with FEA of rubber components.