bluuebunny/crossref_metadata_2025_split huggingface dataset:
Filler-Elastomer Interactions. Part V. Investigation of the Surface Energies of Silane-Modified Silicas
Authors: Wang Meng-Jiao , Wolff Siegfried 
Published: February 2011

Abstract
As shown in previous papers of this series, the main feature of silicas with regard to surface energy, which distinguishes them from carbon blacks, is a low dispersive component, γsd, and a high specific component, γssp, of surface energy. The low γsd, would result in a lack of interaction between filler and hydrocarbon rubbers, while the high γssp would suggest a high degree of agglomeration of the filler particles in the polymer matrix. In this study, the surface free energies and the energy distribution on the surfaces of precipitated silicas which had been modified with octadecyltrimethoxy silane, 3-thiocyanatopropyltriethoxy silane and bis(3-trimethoxysilylpropyl)-tetrasulfane, respectively, were investigated by chromatography at infinite dilution and at finite concentration. A comparison with the initial silica suggests a drastic decrease in surface energy, especially of the specific component, as a result of the modification and a strong dependence of surface energy on the chemical nature of the grafts and the ratio of these grafts. The energy distribution function shows that, while the surface of the ungrafted silica is heterogeneous, the heterogeneity of the fully modified surface is drastically reduced, particularly when the product was modified with octadecyltrimethoxy silane.
Optimizing Mixing in the Banbury Mixer with Synchronous Technology (ST) Rotors
Authors: Donoian G. S. , Canedo E. L. , Valsamis L. N. 
Published: February 2011

Abstract
This presentation is concerned with the mixing performance of the new ST™ rotor design in Banbury® mixers operating at even speed. Rotor orientation was used to optimize machine performance in mixing a standard one-step rubber formulation, in terms of productivity, energy consumption, and product quality. Experimental data is presented on mixer discharge temperature, Mooney viscosity, and maximum rheometer torque, and their standard deviation. The effect of rotor orientation on these parameters is discussed, and optimal rotor configurations are identified.
Recuring Vulcanizates. II. Effect of Added Accelerators
Authors: Layer Robert W. 
Published: February 2011

Abstract
Vulcanizates, to which more accelerator has been added by swelling, were recured to study the interaction between the accelerator and the sulfur crosslinks. The addition of benzothiazole, or dithiocarbamyl sulfenamides, to SBR, SBR/ BR, or NR vulcanizates caused more crosslinks to form on recuring. A typical induction period was also noted. The results were essentially the same in all rubbers. Crosslink formation, as measured by modulus development or rheometer torque, increased with increasing loadings of accelerator. Similarly, at a given accelerator loading, crosslink formation increased with increasing length of the polysulfide crosslink. These results indicate that an equilibrium exists between the zinc salt of the accelerator and the polysulfide crosslinks.
Direct Characterization of Tire Materials by Photoacoustical Infrared and Proton Induced X-Ray Emission Spectroscopy
Authors: Waddell Walter H. , Parker James R. 
Published: February 2011

Abstract
In an effort to find out if compound composition could help explain the observed differences in “chip/chunk tearing” on worn off-the-road tires from two manufacturers, direct characterizations were made on tread lugs from the two tires. Two nondestructive direct analytical methods were used. They are photoacoustical Fourier transform infrared spectroscopy (PA-FTIR) and proton induced x-ray emission spectroscopy (PIXE). These techniques were also used to examine a variety of rubber compounding ingredients, such as polymers and fillers, and model tire compounds containing different levels of these ingredients. PA-FTIR requires essentially no sample preparation. It was successfully used to determine the polymer structure and to suggest the nonblack filler type in highly loaded carbon-black filled, sulfur-cured compounds and in tire sections. The characterization was based upon structural information derived from vibrational band frequencies. Elemental information was obtained by using direct PIXE spectral analysis of polymers, fillers, and two worn off-the-road tire tread lugs. Again, no sample preparation was needed and quantitative information was obtained on the elements present. Results show that the tire that did not display a tear problem was manufactured with a cushion (tread base) and a tread (cap), both containing silica at the 12–15 phr levels. The tire that had a visible chip/chunk problem was constructed with two layers of a very similar stock, but neither layer contains silica.
Filler-Elastomer Interactions. Part VI. Characterization of Carbon Blacks by Inverse Gas Chromatography at Finite Concentration
Authors: Wang Meng-Jiao , Wolff Siegfried 
Published: February 2011

Abstract
Carbon blacks ranging from N110 to N990 were characterized by means of inverse gas chromatography at finite concentration. The isotherms, net heat, and spreading pressures for benzene and cyclohexane adsorption suggest a general trend of increasing surface activity with increases in specific surface area. This is in good agreement with surface-energy measurements reported previously. The energy-distribution function of adsorption shows that while the concentrations of low-energy sites are comparable for most of the carbon blacks, differences exist with regard to high-energy sites. These suggest that small-particle-size blacks possess a greater number of high-energy centers. The graphitization of carbon blacks results in a considerable reduction in their adsorption capacity and narrows the energy distribution of their surfaces. One can therefore conclude that high-energy sites play an important role in the determination of the surface energies and reinforcing ability of carbon blacks.
Nonlinear Load-Deflection Relations of Bonded Elastomeric Circular Disks and Strips
Authors: Ling Yun , Engel Peter A. , Brodsky William L. 
Published: February 2011

Abstract
The nonlinear load-deflection relations of bonded circular disks and infinitely long strips are studied. Finite element analysis is used to evaluate the empirical formula proposed by Payne, which justifies the need for a better formula to predict the load-deflection relation for blocks with large shape factors under a relatively large deformation. General expressions for the load-deflection relations of blocks under axisymmetrical and plane-strain deformations are presented based on a variational approach, i.e. the Raleigh-Ritz method, in which no specific form of strain energy functions is required. Nonlinear load-deflection relations of circular discs and infinitely long strips made of a Mooney-Rivlin material are explicitly given in a power series form. It is found that these solutions agree well with the finite element results and are much more accurate than the empirical formula. It is shown that the solutions obtained by the Raleigh-Ritz method are not sensitive to deformations assumed.
Aggregate Structure: Effect on the Agglomerate Morphology and Cohesivity
Authors: Drakopoulou A. , Feke D. L. , Manas-Zloczower I. 
Published: February 2011

Abstract
The relationship between the structure of individual aggregates of carbon black and the packing density and perceived cohesivity of the agglomerates they form is investigated. Five grades of carbon black aggregates have been analyzed for their size and shape characteristics. The aggregates exhibit fractal-like structures and can be distinguished in terms of their perimeter fractal dimension. The cohesivity of agglomerates formed from individual grades of aggregates has been measured using a tensile-test method. These results can be interpreted in terms of Hamaker constants that characterize the cohesive interaction on the length scale of either the aggregate or primary particle. To build a framework in which the morphology and cohesivity of agglomerates can be linked through knowledge of aggregate characteristics, we utilize a three-parameter shape function to describe the configuration of the aggregates. Here, the two-dimensional projections of the aggregates are assumed to be given in polar coordinates by r=α+ε sin (ηθ) where α is related to the aggregate size, η is a measure of the number of projections of the aggregate, and ε gauges the roughness of the aggregate. The shape of the aggregates and the minimum solids loading within a cohesive agglomerate can adequately be represented using this postulated form.
Ultimate Properties of Stereoregular and Stereoirregular 1,4-Polybutadiene Networks and Their Correlation with Theories
Authors: Sharaf M. A. 
Published: February 2011

Abstract
The ultimate properties of stereoregular and stereoirregular 1,4-polybutadiene (PB) networks covering a range in micro-chemical structure (cis-trans-vinyl) have been investigated. The dependence of the ultimate properties, namely the ultimate strength and the maximum extensibility, on sterochemical structure, has been demonstrated at different temperatures. Also, dependence of the ultimate properties on temperature has been apparent. Focusing special attention on the physical processes that culminate in rupture of the network, confirmed and extended the primary role played by strain-induced crystallization. More specifically, strain-induced crystallization enhances attainment of greater values of strength and extensibility. Noncrystallizable elastomers were found to have lower ultimate properties due to the absence of rupture-impeding mechanisms and consequently they become incapable of reaching their maximum extensibility. The frequently observed maximum in plots of the ultimate strength fr vs. the molecular mass Mc has been verified as an intrinsic property of the networks. This property was found to depend on the degree of crosslinking, rather than being time dependent. Values of the ultimate strength fr of both crystallizable and noncrystallizable networks were well reproduced by Bueche's theory of rupture. On the other hand, the Griffith criteria were found to have some success with noncrystallizable networks. Calculated values of the threshold surface free energy G0 were in agreement with those reported in the literature for similar noncrystallizable networks.
The Preparation, Properties and Potential Applications of “Diimide-Hydrogenated” Styrene-Butadiene (HSBR) and Polybutadiene (HBR) Thermoplastic Elastomers
Authors: Parker Dane K. , Roberts Robert F. , Schiessl Henry W. 
Published: February 2011

Abstract
Our unique diimide-based process for preparing HNBR latex from NDR latex without the use of hydrogen, noble metal catalysts or solvents has now been successfully extended to the preparation of hydrogenated thermoplastic elastomers latexes directly from SBR or BR latex precusors. Commercially available SBR latex such as SBR 1502 can be readily reduced to high saturation levels (95+%) via the diimide reduction technique. Latex cast films of the highly reduced elastomer show excellent ozone and oxidation resistance as expected. Unexpectedly however, the hydrogenated polymer films demonstrate high tensile strength and thermoplastic elastomer (TPE) behavior. The TPE properties have been found to be caused by polyethylene crystallites that exist even in the unstretched films under ambient conditions. Latex is an unusual physical form for a TPE material. As a latex, TPE elastomers can be fabricated into sheets or other products by simple dipping or spraying methods—methods not normally available to TPEs in bulk form. In this regard, HSBR or HBR could function as superior replacements for natural rubber (NR) latex in articles such as tubing, gloves, condoms etc., where ozone and oxidation resistance may be required or in applications where good strength properties coupled with the absence of potentially allergenic proteins and/or curatives may be desirable. Alternatively, HSBR or HBR latexes may also be conventionally coagulated and processed using standard rubber/TPE compounding techniques.
Reduced Time Approach to Curing Kinetics, Part II: Master Curve from Nonisothermal Data
Authors: Shyu G. D. , Chan T. W. , Isayev A. I. 
Published: February 2011

Abstract
Nonisothermal curing kinetic data obtained from differential scanning calorimetry (DSC) for a rubber compound are corrected for the effects of temperature lag between the DSC sample and furnace. The method of Eder and Janeschitz-Kriegl, which is based on experimental data alone without reference to any kinetic model, is used for these corrections. A method is presented for shifting the corrected nonisothermal curing kinetic data with respect to an arbitrarily chosen reference temperature to obtain a master curve. The method is based on experimental data alone without assuming any specific form of kinetic model. When the isothermal curing kinetic data for the same material are shifted with respect to the same reference temperature, a master curve is also obtained which basically overlaps the corresponding master curve from nonisothermal data. It follows that nonisothermal DSC measurements provide the same curing kinetic information as isothermal ones, only over a wider range of temperatures. The shift factors obtained from experimental data alone are compared with the corresponding values calculated from a kinetic model with an Arrhenius type of temperature dependence. This serves as a means of model evaluation. It is concluded that the kinetic model is good at describing isothermal curing kinetic data. But it yields reliable curing kinetic information over a narrower range of temperatures than nonisothermal data alone without resort to any model. The Arrhenius extrapolation of the limited isothermal data to a wide range of temperatures is quite good.
Kinetics of the Epoxidation of Butyl Rubber; Development of a High Precision Analytical Method for Unsaturation Measurement
Authors: Puskas Judit E. , Wilds Christopher 
Published: February 2011

Abstract
A precise, simple and inexpensive method was developed for measuring the unsaturation (U) in butyl rubbers. The method, based on the epoxidation of the double bonds using 3-chloroperoxybenzoic acid, was suggested first by Dreyfuss and Kennedy, Their test was refined based on rate measurements. The accuracy and precision of the new, refined version was found to be very good; 44 data points yielded a standard deviation of 0.0128 mol % around the sample mean U=1.78 mol %. The results agreed very well with 500 MHz 1H NMR data, and were shown to be superior to the traditional iodine index test. The epoxidation was shown to be a second order reaction by the kinetic measurements. The rate constant of the epoxidation was found to be k=287 L/mol · s at 25°C. Rate measurements in the 25–40°C temperature range yielded ΔH*=32 kJ/mol (7.66 kcal/mol) for the activation enthalpy of the epoxidation. The reaction was simulated by a fifth order Runge-Kutta numerical integration with adaptive step-size control, using measured rate constants. Measured values under different conditions showed very good agreement with the simulated rate plots. The traditional qualitative analytical approach was shown to require varying reaction times for varying levels of unsaturation due to a minor side reaction. Understanding the kinetics allowed the determination of unsaturation based on ‘kinetic’ approaches, eliminating the problems associated with the traditional approach. One kinetic approach developed uses two rate measurements at t1/t2=2, and does not require the knowledge of the rate constant. Unsaturation values obtained by this method agreed well with 500 MHz NMR data, but its precision was not satisfactory. The other kinetic approach predicts unsaturation from a single rate measurement. Data generated by this method agreed very well with 500 MHz NMR data, and the precision of this method was found to be equal to that of the ‘traditional’ analytical method discussed in this paper.
Mechanical Properties of Blends of Crystallizable Polybutadienes Containing Amorphous Polybutadiene Diblock Copolymers
Authors: Nir Moira Marx , Cohen Robert E. 
Published: February 2011

Abstract
Tensile failure properties of syndiotactic 1,2 polybutadiene/trans 1,4 polybutadiene crystalline blends are improved by addition of 5–10% amorphous 1,2 polybutadiene/1,4 polybutadiene diblock copolymer. The effect of block molecular weight and microphase behavior of the diblock copolymer was investigated. Heterogeneous diblocks enhance blend properties to a greater extent than homogeneous diblocks. In blends with enhanced properties, percent coverage of interfacial surface area by diblock is on the order of 10%.
The Mechanical Behavior of Double Network Elastomers
Authors: Santangelo P. G. , Roland C. M. 
Published: February 2011

Abstract
It was found that at low residual strains, the modulus of double network rubbers can be less than that of an isotropic elastomer of equal crosslink density. At higher residual strains, the equilibrium modulus is higher for the double network. This aspect of the behavior of networks was investigated using two phenomenological descriptions of rubber elasticity, the Mooney-Rivlin (MR) and the Roth, Martin, and Stiehler (RMS) Equations. Calculations using either approach, which make use of the independent network hypothesis, were qualitatively in agreement with the experimental data. The tensile strength of double networks based on natural rubber were found to be independent of the amount of residual strain. This is true even at higher residual strains, wherein the modulus is significantly amplified. This suggests that the conventional compromise between modulus and failure properties can be circumvented using double network rubbers. Their utilization can yield elastomers of better mechanical properties.
“Explosive Decompression Failure” of Rubbers: A Review of the Origins of Pneumatic Stress Induced Rupture in Elastomers
Authors: Briscoe B. J. , Savvas T. , Kelly C. T. 
Published: February 2011

Abstract
The Review first describes the general features of gas induced rupture in elastomers, induced by a reduction in the ambient gas pressure, and introduces the main variables such as the gas-polymer transport and equilibrium properties. The phenomenologieal nature of the failure processes are also described and the characteristics of the failures encountered are summarized. It is proposed that the failure processes, which involve bubble expansion and subsequent tearing of the interior and exterior of the elastomer, arise from the action of at least two stress fields; one is provided by a simple triaxial tension and the other by an evolving gas concentration gradient. Various routes to model this process are described in the Review. In addition, the importance of the main system variables, on these rupture processes, is assessed and means of deducing, and directly measuring the parameters which may influence the rupture process are described. These include various equilibrium and transient properties such as the extent of the gas mass sorption, the associated volume change and the variation of the mechanical and thermal properties of the polymer-gas system at elevated pressures.
The Development of Fracture Mechanics for Elastomers
Authors: Thomas A. G. 
Published: February 2011

Abstract
The energy balance, or fracture mechanics, approach has proved successful in treating a number of fracture phenomena and unifying them in terms of what is believed to be a basic characteristic, the crack growth behavior when expressed in terms of the energy release rate T. It has also enabled some of the underlying physical factors to be identified and incorporated into appropriate theories. There are, however, some important limitations and outstanding problems which remain. For example, we do not at present have any quantitative understanding of what determines the precise form of the crack growth characteristic under repeated stressing. During the development of the approach, numerous checks were made of its validity by comparative experiments on different test piece geometries. This is important, as it is not certain that such comparisons will invariably give equivalent results and that the T vs. rate of tear relation is a true material characteristic. For example, if a test piece, such as the “split” test piece in Figure 2(d), is subjected to large pre-extensions in the direction of tearing, the tear resistance in some cases may apparently be much reduced from its unprestrained value. (Anisotropy is produced which is believed to be important in knotty tear development). Gent and Kim found a similar effect with laterally pre-strained pure shear test pieces. Also, if tear measurements are made with an edge crack test piece of natural rubber and the strains become great enough to produce crystallization in the main bulk of the test piece, the stick-slip behavior is suppressed and the tear strength appears to be increased. Thus it appears that in some cases the assumption that the strains just around the tip at the instant of tearing are independent of the bulk deformation is not true. Fortunately these cases seem to be the exception rather than the rule, but their occurrence demands continuing caution. Some peel tests of rubber-to-metal bonds for example show apparently anomalous force dependencies on peel angle. The current interest in the understanding and prediction of strength and durability of elastomer articles stems from the increasing importance attached to avoiding premature failure in service. The growing availability of finite element programs capable of dealing with large strains has already meant that force-deflection behavior can be at least approximately designed for; but a corresponding failure design procedure based on fracture mechanics is still in the stage of development.
Advances in Natural Rubber Production
Authors: Kadir Abdul Aziz S. A. 
Published: February 2011

Abstract
This paper will attempt to highlight the various advances made to date in the production and processing of natural rubber (NR). The commercially planted rubber tree, Hevea brasiliensis, can yield as high as 3,000 kg of rubber per hectare in contrast to the 500 kg rubber per hectare obtained from the wild Amazonian rubber trees. The high yield of commercial rubber trees is attributed to the successful breeding program, efficient development of agronomic and crop management practices and proper exploitation systems. Today, the Hevea brasiliensis trees not only contribute to the supply of world natural rubber, but also to the ever increasing demand of tropical timber. Latex extracted from the rubber tree is processed to meet the specific requirements of the consumers. In the area of processing, emphasis is on the production of NR as an industrial raw material with improved quality and consistency. Efforts are also placed on processing efficiency, optimum product mix and production of value added modified NR such as epoxidized and deproteinized NR. The processing activities also take into consideration the control of processing effluent with appropriate effluent treatments or conversion of effluent to useful materials.