bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Different Brass Pretreatments on Rubber-Metal Bonding: Investigated by Analytical Electron Microscopy
Authors: Kretzschmar T. , Hummel K. , Hofer F.
Published: February 2011

Brass samples (thin foils or plates) were pretreated either by etching with aqueous HC1 or by rubbing with emery cloth. A mixture of cis-l,4-polybutadiene with sulfur and N,N-dicyclohexyl-2-benzothiazylsulfenamide was vulcanized in contact with the brass surfaces. The bonding layers were investigated by analytical electron microscopy (AEM). Two preparation techniques for AEM were used, namely cryo-ultramicrotomy to obtain cross sections (applied to foils), or separating ultrathin surface layers with an aqueous HCl/FeCl3 solution (applied to plates). Across the bonding layers, various crystallographic structures and chemical compositions were found, depending on the pretreatment of the brass.
Qualitative and Quantitative Analysis of SBR/BR Blends by Thermogravimetric Analysis
Authors: Amraee I. Amiri , Katbab A. A. , Aghafarajollah Sh
Published: February 2011

The objective of this paper is to present a new method for analyzing SBR/BR blends in passenger tire tread compounds by thermogravimetric analysis. Since the base polymer of most tread compounds in passenger tires are normally either SBR or blend of SBR/BR, the importance of this method is self-explanatory.
Analysis of Power Requirements and Dispersion Quality in Batch Compounding Using a Dispersion Model for Single Agglomerates
Authors: Bohin Fabrice , Feke Donald L. , Manas-Zloczower Ica
Published: February 2011

The extent of dispersion and torque requirements vary with processing time during the compounding of filled polymers in batch mixers. Starting with a model for the erosion of single agglomerates under simple shear flow conditions, equations have been developed that enable correlation and prediction of the evolution of both dispersion quality and mixing torque during the course of processing. There was an excellent agreement between the shape of predicted dimensionless torque curves and experimental results for silica-silicone rubber premixes. The model was also found useful in correlating results reported in the literature for the quality of dispersion of carbon black into natural rubber.
A New Constitutive Relation for Rubber
Authors: Gent A. N.
Published: February 2011

A simple, two-constant, constitutive relation, applicable over the entire range of strains, is proposed for rubber networks. Behavior in simple extension is derived as an example.
Temperature of the Rubber Wheel during Wear Testing on a Lambourn Abrader
Authors: Ramakrishnan R. , Kliman J. , Donovan J. A.
Published: February 2011

Contact of a slipping rubber wheel with the grinding wheel during wear testing on a Lambourn abrader cools the rubber wheel in the contact zone because: (a) the relatively high thermal conductivity of the grindstone conducts the heat into the grindstone; and (b) there is little or no sliding, and therefore no heat generated by sliding. The temperature increase, measured on the rubber wheel outside the contact zone, results from compression and adhesional or tangential deformation hysteresis, and is not from sliding friction. Therefore, the temperature in the wear zone is only 5–10°C above the ambient, and does not simulate the temperature developed in a tire during use. These conclusions are based on real time infrared thermometry of a carbon black filled rubber wheel rotating against an alumina grindstone, a steel wheel and a HDPE wheel at slips ranging from 0 to 13.5% and speeds from 65 to 400 rpm.
Far-Infrared Studies of Polyisoprene Vulcanization
Authors: Hann C. J. , Kuhls G. H. , Hann G. L. , Gilpin R. K.
Published: February 2011

The distribution of crosslink types (i.e., monosulfidic, disutfidic, polysulfidic) in accelerated sulfur vulcanized rubber dramatically effects the performance properties. Chemical probe reagents have been used extensively to determine the distribution of various crosslink types. However, this technique of selectively cleaving the different types of crosslinks and then measuring the swelling of the rubber is time consuming and experimentally difficult. The utility of using Far IR analysis to make these measurements has been explored. Correlations of Far IR data with classical chemical probe data will be presented. To minimize complexity this initial probe is limited to simple model gum polyisoprene/sulfenamide/sulfur formulations representing “Conventional” and “Hi-Lo” vulcanizate categories.
Crosslink Reaction Mechanisms of Diene Rubber with Dicumyl Peroxide
Authors: González L. , Rodríguez A. , Marcos A. , Chamorro C.
Published: February 2011

The scope of this paper is to review peroxide curing of diene elastomers. At high dicumyl peroxide loading and high curing temperature, changes in the crosslinking mechanisms were observed. Both Abstraction of allylic hydrogen and addition to the double bond can act as mechanisms of crosslinking. IR spectroscopy reveals a significant decrease in double bonds, and a new relaxation at temperatures above the Tg of the elastomers is present.
Characterization and Performance Testing of Guayule Latex
Authors: Schloman W. W. , Wyzgoski F. , McIntyre D. , Cornish K. , Siler D. J.
Published: February 2011

Physical and biological properties were determined for a preliminary production run of low-ammonia latex from guayule (GR latex). GR latex, and dipped films produced from compounded GR latex, contain none of the Hevea allergens known to elicit Type I systemic allergic reactions. The polymer phase of GR latex has a lower bulk viscosity and a higher resin content than that of NR. In addition, GR latex serum and rubber lack the activating components present in NR latex. As a result, GR latex cures more slowly and reaches a lower state of cure. The aged stress-strain properties of cured GR films are nonetheless similar to those of NR films.
Diffusion of Solvents in Polybutadiene Rubber Using Capillary Column Inverse Gas Chromatography
Authors: Faridi Niloufar , Duda J. L. , Danner Ronald P.
Published: February 2011

The capillary column inverse gas chromatography (CCIGC) method at infinite dilution of solvent was used to measure the diffusion and partition coefficients of cyclohexane, toluene, n-heptane, chloroform and methyl ethyl ketone in polybutadiene (BR, 95% cis). Experiments were performed over a temperature range of 0 to 70°C. Chromatographic data analysis was carried out in terms of the elution model described by Pawlisch and coworkers. Attempts to conduct experiments at temperatures below 0°C yielded erroneous results. At these low temperatures the high activity of the solvent causes the system to be far from the linear portion of the absorption isotherm or in some cases results in condensation in the capillary column. The Vrentas-Duda free-volume diffusion model was used to interpret and correlate the diffusion data obtained at infinite dilution of the solvent.
Chemical Aspects of Rubber Reinforcement by Fillers
Authors: Wolff Siegfried
Published: February 2011

For decades, the rubber industry, and the tire industry in particular, have been using mainly carbon blacks as reinforcing fillers. Since their structure and specific surface area can be varied over a wide range, carbon blacks are capable of meeting a wide range of different requirements. Even today, we are unable to exert a specific influence on the third component of reinforcement, the “surface activity” (surface energy) of carbon blacks. This problem and new, more stringent tire performance requirements lend new significance to the need for further carbon black research and development. Silicas, which were developed during the nineteen forties and fifties, were mainly used in shoe soling materials. Specific surface area and structure of the silicas were constantly adjusted to meet new requirements in this area. As our knowledge of the reinforcing mechanism of silicas in rubber increased, the benefits and drawbacks of silicas in rubber, in comparison to carbon blacks, became more and more apparent. The challenge to improve their reinforcing effect was then taken up. Since the beginning of the nineteen seventies, the chemical industry has concentrated on developing silanes for the rubber industry. The significance of the formation of covalent rubber-to-filler bonds for rubber reinforcement was recognized, and ways and means for the optimum and most efficient use of silicas and silanes were found, in a long and difficult process. During the past ten years, research and development efforts were dominated by the demand for increasing abrasion resistance, improving wet traction, and achieving the lowest possible rolling resistance. The combined use of silicas and silanes opened up new possibilities for meeting the requirements of the tire industry. After first adapting silanes to the silicas available, research and development efforts have recently been focused on adjusting the silicas to the silanes in order to achieve optimum effectiveness of this reinforcing system. All in all, a process seems to have been initiated in the tire industry which aims at using the silica/organosilane system to much greater advantage.
Studies of Polymer Properties via Inverse Gas Chromatography
Authors: Li Bincai(Pun Choi)
Published: February 2011

Gas Chromatosraphy (GC) using a polymer as the stationary phase to reveal the properties of the polymer — known as Inverse Gas Chromatography (IGC) — is in contrast to conventional GC where gaseous components in the mobile phase are separated and studied. Figure l(a) and l(b) are schematic diagrams showing the arrangement of apparatus in a gas Chromatograph for IGC. The column is filled with packings consisting of thin layer of polymer coated onto an inert support, typically Chromosorb W, Chromosorb G (70 ∼ 80 mesh, acid washed and dimethyldichlorosilane treated), or Teflon. The carrier gas, such as N2, H2, or He, acts as the mobile phase. The solvent, injected as a sharp pulse and vaporized immediately into the carrier gas stream at the entrance of the column, is called the probe. As the probe is carried forward, it is partitioned between the mobile gas phase and the stationary polymer phase. The time required to elute the probe through the column is called the retention time (elution is monitored in the detector and reflected on the recorder or integrator as a peak maximum). The corresponding amount of carrier gas needed is called the retention volume. The detector for the probe may be a thermal conductivity cell (TCD) or flame ionization detector (FID). When an FID is used, the flow of gas is diverted to the flow meter before it reaches the detector as shown in Figure l(b). Some notes on the experimental techniques will be discussed in Section IX. GC has been classified into Gas-Liquid Chromatography (GLC) and Gas-Solid Chromatography (GSC) according to whether the stationary phase is a liquid or a solid, respectively. In IGC, the process is GLC when the temperature of the polymer under investigation is far above its glass transition temperature Tg. The retention is due to absorption of the solvent vapor into the polymer bulk (an amorphous polymer above Tg is viewed as a liquid). When the temperature of the polymer is well below its Tg, the process is GSC and the retention mechanism becomes adsorption of the vapor onto the polymer surface. We shall initially discuss the GLC of polymers and then extend our discussions to GSC. Important applications of IGC to polymer research have been the studies of the thermodynamics of polymer-solvent and polymer-polymer interactions via GLC.
Use of Nonblack Fillers in Tire Compounds
Authors: Waddell Walter H. , Evans Larry R.
Published: February 2011

A variety of nonblack fillers are used in the rubber components of tires. Calcium carbonate, clay, precipitated silica, talc and titanium dioxide are used in white sidewall compounds to impart desired physical properties and appearance. Precipitated silica can be used in black sidewall compounds, including nonstaining EPDM black sidewalls, to significantly improve tear strength, cut-growth resistance and resistance to ozone aging. Precipitated silica is used extensively in wire coat compounds in conjunction with resorcinol and methylene donating resins, and can be used with organocobalt salts to improve adhesive properties, tear strength and cut-growth resistance. Calcium carbonate, clay, mica and talc are found in innerliner compounds, and precipitated silica can be used. Precipitated silica is used in the treads of off-the-road tires such as earthmover tires, in order to improve tear strength and cut-growth resistance. Clay and talc can be used in tire treads. Precipitated silica is also used in the treads of tires of vehicles used for highway driving, such as passenger cars and trucks, in order to reduce the rolling resistance and increase the wet traction of the tire. It is necessary to modify the surface of precipitated silica with a bifunctional organosilane coupling agent in order to maintain tire treadwear for highway vehicles. Figures 16 and 17 are pictorial summaries of the use of nonblack fillers and the benefits of using precipitated silica in the various components of tire compounds, respectively.
Furnace Carbon Black Characterization: Continuing Saga
Authors: Gerspacher M. , O'Farrell C. P. , Nikiel L. , Yang H. H.
Published: February 2011

A summary of the latest efforts to characterize carbon black and the latest findings using state-of-the-art scientific instrumentation is presented. Over the years, advanced studies of furnace carbon black formation and characterization have helped the rubber technologist to better predict the performance of the end product (i.e., a tire) but still today these characteristics are not totally sufficient and more work is necessary to better define and describe the exact nature of carbon black produced using the furnace process.
Strength of Sulfur-Linked Elastomers
Authors: Chun H. , Gent A. N.
Published: February 2011

Fracture energies have been determined for tearing through a sheet of a polysulfide elastomer, and for peeling apart two sheets bonded together with sulfur interlinks. Measurements were made over wide ranges of rate of crack propagation and test temperature. By shifting curves at various temperatures along the rate axis, using shift factors aT calculated from the “universal” form of the WLF equation, master curves were obtained for tear and peel energy vs. rate of tear or peel at the glass transition temperature Tg about −55°C. These master curves of strength vs. effective rate of crack propagation at Tg were closely similar to those obtained previously for several hydrocarbon elastomers: BR, SBR and EPR; interlinked with C-C bonds. Thus, under comparable test conditions the strength of the present polysulfide elastomer with sulfur crosslinks is similar to that for hydrocarbon elastomers with C-C crosslinks. The question then arises: Why are sulfur-vulcanized elastomers stronger in common experience than peroxide-cured ones? Possible reasons are discussed.
Origin of Characteristic Properties of Natural Rubber—Synergistic Effect of Fatty Acids on Crystallization of cis-1,4-Polyisoprene: I, Saturated and Unsaturated Fatty Acids
Authors: Kawahara Seiichi , Nishiyama Naoyuki , Kakubo Takashi , Tanaka Yasuyuki
Published: February 2011

The influence of stearic acid, linoleic acid and their methylesters on crystallization of synthetic cis-1,4-polyisoprene was investigated at the isothermal crystallization temperature of −25°C by means of differential scanning calorimetry and dilatometry. The overall crystallization rate of cis-1,4-polyisoprene increased in step with increasing stearic acid content, while the glass transition temperature of cis-1,4-polyisoprene did not change with the additive level. The addition of 1 wt % stearic acid or methyl stearate showed an acceleration effect on the initial crystallization of the polymer, while 1 wt % linoleic acid or methyl linoleate suppressed the initial crystallization. Coexistence of stearic acid and linoleic acid or stearic acid and methyl linoleate in cis-1,4-polyisoprene gave rise to a dramatic increase in the overall crystallization rate of the polymer. The characteristic properties of natural rubber were revealed to be related to the specific ratio of miscible fatty acids to immiscible fatty acids in natural rubber.
Curative Migration in Rubber Compounds Containing Brominated Poly(Isobutylene-co-4-Methylstyrene)
Authors: Dias Anthony J. , Galuska Alan A.
Published: February 2011

Blends of elastomers are widely used throughout the rubber industry. Blends are frequently used to get a balance of properties which cannot be achieved through the use of a single elastomer. For example, poly(isobutylene-co-4-bromomethylstyrene) can be blended with highly unsaturated general purpose rubbers to impart unique barrier or dynamic properties and enhanced oxidative stability. The final properties of such a blend are the result of a complex series of compounding, mixing and curing stages. These stages profoundly impact the homogeneity of the mixed components which include: the polymers, the filler, and the curatives. It is important to develop tools to monitor the changes which occur during compounding. This paper details the application of static secondary ion time-of-flight mass spectroscopy (ToF-SSIMS) imaging to simultaneously map polymer phase information with specific chemical information. The paper will highlight the utility of ToF-SSIMS for the study of the chemical and physical changes occurring during elastomer compounding. Blends of poly(isobutylene-co-4-bromomethylstyrene) and general purpose rubbers were compounded with typical cure systems and studied under a variety of mixing conditions.
Interaction between Carboxylated Nitrile Rubber and Precipitated Silica: Role of (3-Aminopropyl)Triethoxysilane
Authors: Bandyopadhyay Sumanda , De P. P. , Tripathy D. K. , De S. K.
Published: February 2011

On the basis of measurements of bound rubber and physical properties and the results of Monsanto rheometer, dynamic mechanical and infrared spectroscopic studies, it is observed that strong rubber-filler interaction occurs between XNBR and precipitated silica filler. During molding, XNBR was found to be crosslinked by the filler surface through the formation of primary bonds. The coupling agent, namely (3-aminopropyl)triethoxysilane facilitates the formation of rubber-filler bonds at the expense of filler-filler networks, leading to improved dispersion and enhanced degree of crosslinking.
Electrostriction of Rubber Sheets
Authors: Ma Y. , Reneker D. H.
Published: February 2011

Electrostriction coefficients were measured for sheets of five commercially important rubbers. The rubbers, polychloroprene, polyisoprene, chlorobutyl, nitrile, and chlorosulfonated polyethylene, were formulated and cured in a way ordinarily used for rubber applications. The electrostriction coefficients were in the range of 0.2 to 1.4×10−17m2/V2, which is approximately 50 times larger than the electrostriction coefficients reported for the higher modulus polymers used in fibers, films and structures. The electrostriction was measured perpendicular to the sheet, with the electric field in the same direction. All the rubbers contracted along the direction of the electric field as the magnitude of the field increased. Mechanical constraints at the surfaces of the sheets were shown to affect the measured values of the electrostriction coefficients. Relaxation measurements showed that the electrostriction coefficients increased at longer measurement times. Corrections were made for the relatively small decrease in the thickness of the samples due to the attractive electrostatic force between the electrodes. Thermal expansion effects were reduced to negligible levels by choosing samples with high electrical resistivity, and by using short measurement times.
Particle Size Distribution of SBR and NBR Latexes by UV-VIS Turbidimetry near the Rayleigh Region
Authors: Llosent Mario A. , Gugliotta Luis M. , Meira Gregorio R.
Published: February 2011

This paper deals with data treatment problems that arise when turbidimetry is employed to estimate the particle size distribution (PSD) of soft polymer latexes with low diameter limits around 40 nm. Scanning electron microscopy and dynamic light scattering were used as comparison techniques. Industrial latexes of styrene-butadiene rubber (SBR) and of acrylonitrile-butadiene rubber (NBR) were investigated. The data treatment involved the use of Mie's Model to obtain an average diameter and/or the complete PSD. For estimating the complete PSD, a least squares optimization (with an imposed distribution shape) and a numerical deconvolution procedure (without assumptions on the distribution shape) were attempted. A synthetic example was solved to investigate the limits of the applied numerical methods. For the polymer refractive index functions, Cauchy's Law was used — and its adequate adjustment proved essential for good turbidimetric estimations. A reasonable agreement between the turbidity measurements and the other independent estimations was verified. For the SEM observations, the soft latexes were hardened by irradiation before observation, but negligible diameter variations were detected.
Evaluation of Chain Scission during Mixing of Filled Compounds
Authors: Ahagon Asahiro
Published: February 2011

Whether chain scission takes place during mixing of black-filled compounds has been a debatable subject which is yet unsettled. The uncertainty originates from the material system which contains gel. A direct method to evaluate scission is to quantify the change in the number of chain ends, since two chain ends will be newly created on each event of scission. It requires determination of an average molecular weight of the linear components which constitute the gel-containing system. The degree of polymerization denned in the Charlesby-Pinner theory, derived for crosslinking study by means of sol-gel analysis, could be conveniently used for the purpose. The theory, however, cannot be directly applied for black-filled compounds because the composite structure in the compounds does not allow one to satisfy the assumptions made in the theory, i.e., an equal chance of crosslinking for every reactive site. A new technique is developed so that the assumption is satisfied and the sol-gel analysis can be carried out even with black-filled compounds. This technique is applied for numbers of compounds, with the same formulation but mixed under various conditions. A NR and an SBR formulations are used here. The results clearly indicate that chain scission takes place during mixing of both NR and SBR compounds.
Tear Strength of Carbon-Black-Filled Compounds
Authors: De D. , Gent A. N.
Published: February 2011

Measurements are reported of tear strength for several carbon-black-filled compounds over a wide range of temperature. Attention is focussed on “knotty tearing” when the tear deviates from the straight-ahead direction and sometimes splits, and the tear force rises markedly. Knotty tearing occurs only over certain temperature ranges which appear to be related to the glass temperature of the elastomer. It is suppressed when the crosslink concentration is either unusually high or unusually low. It is strongly dependent on the type of carbon black, and sensitive to the particular elastomer used, being virtually absent with one cis-polybutadiene elastomer although evident with others. It appears to be related to the ability of the compound to create a high degree of orientation of carbon black particles at the crack tip and thus induce a marked anisotropy of strength in this region. However, it was often absent in pure shear experiments, when the overall extension of the specimen was much smaller, and absent in conventional tensile tests when the initial crack was small and grew rapidly as a smooth fracture. Even in the absence of knotty tearing, the tear strength of filled compounds was found to be five to ten times higher than for the corresponding unfilled compounds. This is attributed, at least in part, to enhanced hysteresis.
Tire Wet Traction—Explaining Performance Variation Using the ‘Criticality’ Concept
Authors: Veith Alan G.
Published: February 2011

The results of four different wet traction evaluation techniques show that the relative performance for individual candidate tires is a function of the test conditions as well as tire design features. For a given tire, test conditions such as test speed, pavement texture and water depth determine the relative magnitude of two basic footprint lubrication modes (1) boundary layer (BL), with intimate contact and good grip which predominates at low speeds, high texture and minimal water depth, and (2) elastohydrodynamic (EHL), with minimal contact and poor grip which predominates at high speeds, low texture and deeper water. A concept called ‘critically’ is defined as the fraction of the footprint contact area in the EHL mode Knowledge of the test conditions permits an estimate of the relative critically of any testing operation. Definitive wet traction performance interpretation depends on criticallyy information since tests at low critically frequently show minimal differences (among candidate tires) while tests at high critically usually show a wide range of performance.
Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins
Authors: Versloot P. , Haasnoot J. G. , Nieuwenhuizen P. J. , Reedijk J. , van Duin M. , Put J.
Published: February 2011

The sulfur vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the vulcanization process.
Vulcanization of Ultrasonically Devulcanized SBR Elastomers
Authors: Levin V. Yu , Kim S. H. , Isayev A. I.
Published: February 2011

Sulfur cured SBR elastomers, devulcanized by high power ultrasonic irradiation, were revulcanized by using the same curing conditions as for virgin SBR. Crosslink density and gel fraction of virgin, devulcanized, and revulcanized elastomers were measured. Curing behavior of some model compounds based on virgin and devulcanized SBR was investigated. Strongly pronounced differences between the curing behavior of virgin and devulcanized elastomers were observed. Torque and DSC studies indicate that two different processes during the crosslinking of devulcanized rubber take place. The existence of these two processes is explained by crosslinking of sulfidized polymer chains followed by crosslinking due to the presence of sulfur and accelerator. Chemical differences between virgin and devulcanized elastomers, explaining the observed phenomena, are discussed.
An Evaluation of Strain Amplification Concepts via Monte Carlo Simulations of an Ideal Composite
Authors: Govindjee Sanjay
Published: February 2011

In the modeling of carbon-black filled elastomers it is important to have a good estimate of the state of the elastomer itself, since many nonlinear effects originate in the matrix material. A common notion in such estimates is the idea of a “strain amplification” factor that relates a macroscopically imposed strain state to the average strain state in the elastomer matrix material. In this paper Mullins and Tobin's interpretation of the Guth—Gold and Smallwood's amplification factor, and a more recent proposal by Govindjee and Simo will be examined. All three theories are compared to the results of a series of Monte Carlo simulations on an ideal composite with a Neo-Hookean matrix and semi-rigid inclusions. It is shown that for the idealized material, one can not interpret the Guth—Gold and Smallwood amplification factors as an estimate of the strain state of the matrix material. The theory of Govindjee and Simo, on the other hand, is shown to accurately predict the strain state of the matrix.
Some Initial Trials and Applications of the DFCS Test for Carbon Black Dispersion
Authors: Murray G. A. W. , Ng B. H. R. , Jahromi M. R. Vaseghi , Southwart D. W.
Published: February 2011

The Dark Field Cut Surface (DFCS) test is a quantitative method for determining the state of dispersion of carbon black in rubber compounds. The method has been described fully in another paper. Here are reported some of the first applications of the test and some trials that were carried out specifically to investigate and develop the DFCS test. The test is demonstrated to follow accurately the progress of dispersion of carbon black in milled or mixed compounds of NR and SBR. Some tests have been carried out using large batches of test results and these have demonstrated a good fit with a normal distribution. By this means, some recommendations have been derived for suitable sampling rates. The relative merits of the standard deviation and the average for characterizing dispersion have been highlighted. A further way of presenting the results as distribution curves has been demonstrated. A check has been performed to demonstrate that mastication of rubber has little or no influence on the DFCS test results. The DFCS test has been used to give an interesting (provisional) insight to the best ways to operate a rubber mixer. To date, the measured patterns of scattered light show a promising correlation with the anticipated dispersion of carbon black in the specimens tested.
Electrical Conductivity of Polystyrene-Rubber Blends Loaded with Carbon Black
Authors: Soares B. G. , Gubbels F. , Jéro^me R. , Vanlathem E. , Deltour R.
Published: February 2011

Polystyrene/rubber blends have been loaded with carbon black (CB) and the filler localization in the two-phase polyblends has been studied in relation to the chemical structure of the rubber. The CB localization and the electrical conductivity are greatly influenced by the substitution of the rubber chains. In polystyrene/polybutadiene blends, the filler is localized within the polybutadiene phase. In contrast, in polystyrene/polyisoprene and polystyrene/ethylene—propylene rubber (EPM) blends, CB is mainly localized at the interface, so that the CB percolation threshold in cocontinuous two-phase polyblends is dramatically decreased.
On the Ogden Strain-Energy Function
Authors: Yeoh O. H.
Published: February 2011

The Ogden strain-energy function for rubber appears to be gaining popularity among users of finite element analysis. This paper discusses some of the special features of this material model. It explains why nonlinear regression analysis of stress-strain data obtained from just one mode of deformation may yield an Ogden strain-energy function that is unsatisfactory for predicting behavior in other deformation modes. It suggests the regression analysis be constrained such that some of the coefficients are chosen based upon the known behavior of rubbery materials.
Superior Mechanical Properties of Reclaimed SBR with Bimodal Network
Authors: Isayev A. I. , Kim S. H. , Levin V. Yu
Published: February 2011

The correlation between the mechanical properties of revulcanized SBR, total and polysulfidic crosslink density, gel fraction of original vulcanizate, ultrasonically devulcanized, and revulcanized rubber is described. Under some processing conditions the tensile strength of revulcanized SBR is found to be much higher than that of the original vulcanizate with elongation at break being practically intact. A model explaining the increase in mechanical properties of revulcanized rubber is proposed.
Strain-Crystallization of Guayule and Hevea Rubbers
Authors: Choi I. S. , Roland C. M.
Published: February 2011

A comparison was made of the room temperature strain-crystallization of naturally-occurring cis-1,4-polyisoprenes having varying non-rubber content. A variety of measurements were employed to assess crystallization, including stress relaxation, optical birefringence, and the infrared absorption spectrum. All methods yielded the same result: The strain required to induce crystallization is less for polyisoprenes having larger concentrations of impurities. The ability to crystallize at lower orientation presumably underlies the superior failure properties of guayule rubber and the poorer grades of natural rubber (NR) in comparison to deproteinized NR.
Quantitative Determination of the Microstructure and Composition of Crosslinked Rubber Blends
Authors: Thorn-Csányi Emma , Luginsland Hans-Detlef
Published: February 2011

Intermolecular metathetic polymer degradation opens up an analytic method to identify the quality and quantity of the components in blends of different types of rubber even if they are crosslinked and filled with carbon black, mineral oil, etc.. Furthermore the amount of soluble and insoluble additives can be determined. Moreover, metathetic degradation allows for determination of detailed information about the chemical microstructure (e.g. sequence length distribution of 1,2-butadiene and styrene units) of the rubbers used. This method is suitable for analysis of rubber components in tires.
Solid State 13C NMR Analysis of Vulcanized Rubbers XVI. The Competitive Vulcanization of Natural Rubber and Polybutadiene Blends
Authors: Klei B. , Koenig J. L.
Published: February 2011

Solid state 13C NMR was used to study the competitive vulcanization of blends of natural rubber and high cis polybutadiene. A NMR sampling technique utilizing the stacked homopolymers was developed that helps to determine the spectral differences occurring due to competitively vulcanizing an elastomer blend. The small amount of interfacial crosslinking was expected to be undetectable but has been tentatively observed. Concentration of crosslinks at the interface may occur from limited solubility of curative species in both rubbers. The NMR spectra also showed inhibition of cis-trans isomerization in natural rubber with addition of polybutadiene.
Simulation of Non-Newtonian Flow of Rubber Compounds in a Pin Barrel Screw Extruder
Authors: Shin Kyung Chul , White James L.
Published: February 2011

A simulation is presented of flow of a rubber compound, modeled as a power law non-Newtonian fluid, in screw designs including screws with slices and a pin barrel extruder. Calculations were carried out using the flow analysis network (FAN) technique. Pressure fields, flux fields, and screw characteristic curves were determined. Introducing non-Newtonian (shear-thinning viscosity) characteristics reduces screw pumping ability. Slices in screw flights produce backward fluxes in the screw channel and reduce pumping capacity. Introduction of pins into the barrel has only a minor effect on screw pumping characteristics, and the pumping capacity of a pin barrel extruder closely resembles that in a screw extruder with slices in its screw flights.
Crack Analysis of Unfilled Natural Rubber Using Infrared Microspectroscopy
Authors: Neumeister Lori , Koenig J. L.
Published: February 2011

The characterization and analysis of the crack tip region of unfilled natural rubber is crucial in developing a fatigue resistant material. Therefore, the molecular structure and orientation of the material in the crack tip region has been compared to the bulk. Cracks formed by different methods were evaluated using both transmission and reflection techniques of infrared microspectroscopy. The material around the crack tip and crack edges shows much higher absorbances than the bulk material for stressed rubber. This is due to a higher concentration of material and residual orientation effects. For unstressed material the crack tip region exhibits identical characteristics to the bulk material.
Preparation and Characterization of Solution SIBR via Anionic Polymerization
Authors: Halasa Adel F.
Published: February 2011

Harnessing anionic terpolymerization of styrene, isoprene and butadiene to a degree where one can achieve simultaneous control of composition, microstructure and sequence distribution results in a unique family of elastomeric materials. We now can tailor-make elastomers having diverse viscoelastic responses to suit specific tire applications, in particular, those required for high performance tires. Furthermore, we have demonstrated unique morphologies attainable for SIBR ranging from lamellar to spherical. Such morphologies were reported previously for soft/hard block copolymers, i.e. SBS and SIS, but not for soft/soft systems. It is our contention that this will further contribute to our understanding of the relationship between morphology and cured physical properties.
Scanning Probe Microscopy of Polymer Surfaces
Authors: Tsukruk Vladimir V.
Published: February 2011

Basic principles and recent results of scanning probe microscopy (SPM) studies of polymer surfaces are reviewed. Applicability of various SPM techniques—including contact, dynamic, force modulation, friction force, chemical force, electrostatic, adhesion, and thermal modes—to probing of polymer surfaces is illustrated. Examples of recent studies of surface morphology and properties of various polymers are presented and briefly discussed. An extensive bibliography of more than 200 references is included. Classes of polymers considered here are: crystalline and amorphous, composites and blends, fibers and deformed polymers, block polymers and latexes, rubbers and liquid crystalline polymers, thin films and ionomers. Current focuses and future trends are summarized including quantitative SPM measurements, probing of nano- and microscale mechanical properties, studying dynamical surface properties, and exploring local chemical interactions.
NMR Imaging of Elastomers: A Review
Authors: Blümler P. , Blümich B.
Published: February 2011

From curiosity driven investigations about 10 years ago NMR imaging of materials has developed into a useful tool for characterization of polymers, in particular of elastomer products. A clear indicator of this development is the increasing number of imaging spectrometers in use at industrial research and quality-control laboratories. Typical applications of NMR imaging to elastomers are investigations of the homogeneity of a compound or product components like gaskets or tire profiles, studies of the aging behavior under different loading conditions, the mapping of stress, strain and temperature distributions, and the analysis of material change after application of an overload. Elastomers constitute a class of materials particularly suitable to NMR imaging, because they are rich in protons, the most sensitive, stable NMR nucleus, and the material is soft, giving rise to small dipole-dipole couplings and thus to comparatively narrow lines and favorable imaging conditions. Yet the residual dipole-dipole interaction which remains unaveraged from the thermal motion of intercrosslink chains is a most valuable source of information. It determines the relaxation times so that measurement of various relaxation parameters provides information on cross-link density, stress, strain, and temperature in rubber materials. Spectroscopic investigations on the other hand are not very informative, because they are sensitive to chemical change, which is often too small to be detectable under reasonable conditions even for chain scission or additional cross-linking during aging. The measurement of relaxation times does not require homogeneous magnetic fields, so that new NMR devices based on inexpensive, permanent magnets can be developed, which are applied to the surface of arbitrarily large elastomer products. The NMR MOUSE is such a mobile NMR scanner, which has been shown to be sensitive within limits to changes in cross-link density, strain and temperature. Thus NMR imaging is progressing from the acquisition of entire images which show distributions of material properties to the monitoring of volume-selective NMR information, which can be expected to be used not only for quality control and failure analysis but also for process control and on-line monitoring in the future.
Effect of Various Bonding Agents on the Sulfidation of Brass-Plated Steel Cords Immersed in Squalene Mixtures
Authors: Hamed G. R. , Paul R.
Published: February 2011

Brass-plated steel cords have been immersed at elevated temperatures in various squalene mixtures containing sulfur curatives and commercially available bonding agents. Copper sulfide growth was characterized by scanning electron microscopy and energy dispersive x-ray analysis. The bonding agents cause early sulfide growth, even prior to “scorch,” but mitigate sulfide overgrowth upon humid aging. Both effects are expected to improve joint durability.
Chemical Interaction between Surface Oxidized Carbon Black and Epoxidized Natural Rubber
Authors: Manna Ajoy K. , De P. P. , Tripathy D. K. , De S. K. , Chatterjee M. K.
Published: February 2011

This study—based on Monsanto Rheometer measurements, determination of bound rubber, enthalpy of reaction, solvent swelling studies, and measurement of physical properties— revealed that the functional groups of intermediate super abrasion furnace (ISAF) carbon black chemically interact with the epoxidized natural rubber. The extent of interaction is greater in the case of an oxidized grade of ISAF black than the nonoxidized grade. Infrared spectral studies show that the interaction between the rubber and carbon black leads to chemical bond formation. It is believed that the oxidized grade of carbon black forms ester-type as well as phenolic ether-type bonds, while the nonoxidized grade forms primarily the phenolic ether-type of linkages.
Viscoelastic Behavior of NBR/EVA Polymer Blends: Application of Models
Authors: Bandyopadhyay G. G. , Bhagawan S. S. , Ninan K. N. , Thomas S.
Published: February 2011

The viscoelastic properties of blends based on nitrile rubber (NBR) and ethylene-vinyl acetate copolymer (EVA), a thermoplastic elastomer, are investigated in terms of storage modulus and loss tangent for different compositions. These small-strain dynamic mechanical properties have been evaluated using a Rheovibron Viscoelastometer covering a wide temperature range. Attempts have been made to fit the experimental results with computations based on mean field theories developed by Kerner. Predictions based on the discrete particle model (which assumes one of the components of the blend to be the matrix and the other dispersed as inclusions) are found to be satisfactory in the case of 30/70 NBR/EVA blend but not 70/30 and 50/50 blends. The packed grain model (which assumes neither of the components to be the matrix but approximates a co-continuous structure of the two) predictions do not agree with the experimental data on 50/50 blend for which a co-continuous morphology was revealed by SEM observations.
Solid-State C-13 NMR Studies of Vulcanized Elastomers XVII. Effect of Carbon Black Grade on the Network Structure in Natural Rubber Vulcanizates
Authors: Mori Makio , Koenig Jack L.
Published: February 2011

The vulcanization chemistry and network formation of carbon black filled natural rubber vulcanized with sulfur and TBBS were studied using solid-state C-13 NMR and equilibrium swelling measurements. A reduction in the sulfur rank of the A1 type sulfide and increased production of B1 type polysulfide are observed when the carbon black concentration increases in natural rubber. At the same loading level, the structural property or grade of carbon black does not affect qualitatively the type of sulfide formation. The efficiency of the intermolecular crosslinking over the whole range of sulfurizations is 45.7% for the unfilled vulcanizate. The extent of the chemical sulfurization reactions (NMR result) is constant with black incorporation, while the total network (swelling result) increases with increases in the black loading. The amount of physical entanglements, estimated from the comparison of the NMR and swelling results, is found to increase linearly with the carbon black concentration. The entanglements increase as a function of the 300% modulus, which suggests that the effective level of reinforcement depends on the nature of the individual carbon black. It is assumed that physical adsorption plays a major role in the polymer-filler interactions in the natural rubber/carbon black system.
Characterization of Polymer Adsorption on Disordered Filler Surfaces by Transversal 1H NMR Relaxation
Authors: Lüchow H. , Breier E. , Gronski W.
Published: February 2011

The transversal 1H NMR relaxation of the bound rubber shell of carbon black loaded elastomers can be decomposed into three relaxation regimes corresponding to the loosely bound rubber, the rubber that is immobilized on the carbon black surface and a third component of intermediate mobility. The relaxation time T2 of the intermediate component is related to the end-to-end distance of polymer segments between adsorption sites on the carbon black surface, by converting the relaxation times to length scales on the basis of recent work on NMR relaxation of elastomeric networks. From measurements on SBR loaded with carbon black N 220, a distance of 2.3 nm was obtained in agreement with characteristic dimensions of crystallite sizes and surface roughness as determined by atomic force and scanning tunneling microscopy. The analysis was applied to novel inversion blacks which give lower tan δ/60°C, and rolling resistance without affecting tan δ/0°C and wet skid behavior. These blacks were found to possess a higher density of adsorption sites and a greater surface roughness as compared to standard carbon blacks. In addition to the surface characterization, the analysis of the mobile component of the compound allowed the estimation of the density of entanglement couplings between the rubber matrix and the bound rubber shell.
Thermoplastic Elastomeric Blends of Nylon-6/Acrylate Rubber: Influence of Interaction on Mechanical and Dynamic Mechanical Thermal Properties
Authors: Jha Abhijit , Bhowmick Anil K.
Published: February 2011

Nylon-6 and acrylate rubber (ACM) were melt blended in a Brabender Plasticorder at 220 °C and 40 rpm rotor speed. The reactive nature of the blend is reflected in the mixing torque behavior of the blends at different compositions. The solubility characteristics of the blends in formic acid solution gives an approximate idea of the amount of nylon-6 grafted onto ACM and vice-versa. A reaction mechanism is proposed based on the well known epoxy—amine and epoxy—acid reactions and is confirmed by infrared spectroscopic studies of the blends. The influence of interaction between the two polymers on the mechanical and the dynamic mechanical properties of the blends is analyzed in detail, and the results are interpreted on the basis of the formation of nylon—ACM graft copolymer at the interfaces. The dynamic mechanical thermal analysis (DMTA) reveals a two phase morphological structure, indicating incompatibility of the blend components. The grafting reaction results in dramatic increase in both the storage modulus and the Young's modulus of blends. The presence of grafted rubber chains is reflected in the secondary transition of the rubber loss peak at higher temperature. Also, a substantial improvement in the damping properties of the blends in the service temperature range (i.e., 25 to 175 °C) is revealed from the DMTA results. The dynamic vulcanization of the ACM phase during melt mixing improves the elongation at break values of the blends.