bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheology and Microstructure of Polymer/Asphalt Blends
Authors: Bouldin M. G. , Collins J. H. , Berker A. 
Published: February 2011

Abstract
This work demonstrates the effectiveness of polymers in improving, especially, the high temperature properties of asphalt. The appropriate choice of asphalt, asphalt-grade, polymer type, polymer concentration, and the method of mixing determine if a network-like structure is formed. This morphology significantly improves the creep performance of the binder at elevated temperatures, i.e., the binder has the ability to store deformation energy with subsequent recoil. This is contrary to Newtonian fluids which transform the energy into viscous flow (no recoil). Within the context of dynamic mechanical measurements, the presence of a polymeric network is manifested through the appearance of a plateau modulus. In the case of binders containing block copolymers, we have repeatedly observed that such property improvement in the high-temperature range is generally accompanied by a reduction of the glassy modulus at the low-temperature range as well. It should be noted that by modifying low-viscosity asphalts (i.e., low AC-grades) with polymers, binders can be obtained which exhibit significantly lower moduli at low temperatures and higher moduli at elevated temperatures. This suggests that although using a high AC-grade asphalt may yield satisfactory results at a particular temperature (high temperature), one may instead optimize binders over the entire temperature range (high and low) by starting with a low AC-grade and adding polymer. These results indicate that careful Theological measurements can be a powerful tool in the characterization and design of viscoelastic blends.
Recent Advances in Anionic Synthesis of Functionalized Polymers
Authors: Quirk Roderic P. , Yin Jian , Guo Shao-Hua , Hu Xiao-Wei , Summers Gabriel J. , Kim Jungahn , Zhu Lin-Fang , Ma Jing-Jing , Takizawa Toshiki , Lynch Thomas 
Published: February 2011

Abstract
There has been growing interest and research on new synthetic methods for the preparation of well-defined polymers with in-chain and chain-end functional groups. These functional groups in polymers can participate in (a) reversible ionic association; (b) chain extension, branching or crosslinking reactions with polyfunctional reagents; (c) coupling and linking with reactive groups on other oligomer or polymer chains; and (d) initiation of polymerization of other monomers. It is noteworthy that the use of end-functionalized polybutadienes formed by reaction of poly(butadienyl)lithium with 4,4′-bis(diethylamino)-benzophenone has been reported to provide marked improvements in the wear and traction properties of tires. In order to exploit the unique potential of functionalized polymers, it is important to consider the scope and limitations of current functionalization methodology using anionic polymerization. Anionic polymerization approaches the goal of synthesizing polymers with predictable, well-defined structures in certain systems such as diene, styrene, methacrylate, and heterocyclic monomers, which proceed in the absence of chain termination and chain transfer reactions. These living polymerizations generate stable, anionic polymer chain ends when all of the monomer has been consumed. In principle, these anionic chain ends can react with a variety of electrophilic species to generate a diverse array of functional groups. Unfortunately, many of the reported functionalization reactions have not been well characterized. Another limitation of the use of specific electrophilic functionalization reactions is the necessity of developing, optimizing, and characterizing new procedures for each different functional group. Variables such as chain-end structure, solvent, temperature, concentration, stoichiometry, mode of addition of reagents, and polar additives can have dramatic effects on yield and product distributions. This review will first provide a critical overview of some recent developments in the use of specific functionalization reactions to prepare polymers labeled with carboxyl, hydroxyl, amino, and sulfonate end groups via alkyllithium-initiated polymerization methods. In addition, a recently developed methodology will be described which utilizes the addition reactions of organolithium compounds to substituted 1,1-diphenylethylenes as a general, quantitative functionalization reaction, independent of the specific functional group.
Effect of Surface Cracks on Torsional Damping
Authors: Gent A. N. , Mifune N. 
Published: February 2011

Abstract
Small cracks are often present in the surfaces of rubber samples. They would be expected to lead to enhanced mechanical damping from frictional energy losses as the surface is deformed. Model experiments reported here have shown that marked increases in tan δ, by as much as 10×, can arise from small relative sliding motions of cuts in the surface of rubber samples. The effect is strongly dependent on the area of the cut surfaces, the direction of the cuts relative to the imposed motion, and stresses acting to open the cuts or keep them closed. When a viscous oil was applied to the cut surfaces, the effect was generally enhanced. Not always, however—friction of dry rubber was found to give rise to equally large energy losses in SBR.
Analysis of Nonlinear Stress—Strain Relationship of Large Elastic Deformation of Rubber and Studies on Rubber—Rubber Composites
Authors: Sarkar Amalendu , Dutta Debashis , Bhowmick Anil K. , Majumdar Swapan 
Published: February 2011

Abstract
1. A computer program based on the numerical method of finite-element analysis using Rivlin-Saunder's equation has been developed for the calculation of nonlinear stress-strain behavior of rubber. 2. The experimental stress-strain relationship can be predicted from the above theory. 3. The theoretical deformation pattern of a binary joint composite is in qualitative agreement with the experimental findings. 4. The stress-distribution pattern of the binary joints is largely dependent upon the geometry of the composite. The stress distribution of the transverse-type composite follows a linear relationship, while for the radial type composite, it increases gradually and reaches a maximum value at the bondline junction, then it again decreases with further increments in value of the y-axis. 5. The more acute the joint angle is, the higher is the stress concentration at the angle tip. 6. The higher the difference in the modulus value across the interface, the higher is the shear stress at the junction and the lower the tensile strength. 7. For transverse type composites, the stress concentration at the crack tip near to the edge is much higher than that at the crack tip near the bondline. 8. In the case of adhesively bonded joints, the stresses along the bondline decrease with the increase in distance away from the crack front.
Numerical Prediction of the Aramid-Cord Load in the Goodrich Block Fatigue Test
Authors: de Jong M. C. , Winkler E. M. 
Published: February 2011

Abstract
In the Goodrich Block Fatigue test, tire cords are tested for their (compression) fatigue behavior. The test specimen, a rubber block with a cord in its center, is cyclically extended and compressed. After a certain running time the retained cord strength is measured. The local cord load cannot be measured directly. Therefore, a calculation procedure is provided to predict the local stress and strain along the cord due to clamping, elongation and compression of the specimen. To this end, a few—for aramid only four—basic linear finite-element computations are needed. Calculation results show that clamping causes a complex load distribution along the cord. This load is not uniform but varies along the axis, and the center of the cord is already in compression. By subsequently elongating the specimen, this compressive region decreases while compression of the specimen leads to an increase. From the standard aramid test conditions, it is apparent that the cord remains compressed in the center. The cord part beginning at the end always remains under tension. Furthermore, there is a small cord section at some distance from the center which is cyclically stretched and compressed during the dynamic load. Experiments show that a fatigued aramid cord mostly breaks in this area, where the cord is subjected to both tension and compression. By combining calculation results with experimentally determined breaking positions of cords, accurate information can be obtained about the loading conditions which are most severe. These findings lead to a better understanding of the failure mechanism of tire cords in the Goodrich Block Fatigue test.
Anisotropy of Ultimate Properties in Vulcanizates of EPDM/High-Diene-Rubber Blends
Authors: Coran A. Y. 
Published: February 2011

Abstract
It can be concluded from this work that the ultimate mechanical properties of NR/EPDM blends are indeed anisotropic, but that the tendency towards anisotropy (and, thus, the tendency towards weakness in certain directions, e.g., a tendency to tear with the processing-flow direction or grain) is greatly reduced when one uses the dynamic vulcanization technique. This technique improves cut-growth resistance (in the grain direction), peel strength, and interply adhesion. Also, because of the modification of the EPDM to give reactive sites (pendent succinic-anhydride groups) for vulcanization to occur by a means other than sulfur, the cure-rate incompatibility problem is greatly ameliorated. Thus, improvements in permanent set, hysteresis, and rebound are obtained by using the techniques of this report.
Pattern Abrasion and Other Mechanisms of Wear of Tank Track Pads
Authors: Medalia A. I. , Alesi A. L. , Mead J. L. 
Published: February 2011

Abstract
Wear of tank track pads has been studied under different conditions. With T142 pads tested on an M-60 tank, the mode of failure was found to depend on the test conditions. Among eighteen experimental compounds tested, improved wear (vs. the standard compound) under one test condition was generally at the expense of poorer wear under one or both of the other test conditions. However, in agreement with previous results, an HNBR/Zn-methacrylate/peroxide compound gave improved wear rate under all three test conditions. Wear of the T142 pads on a hilly cross-country course and on a combination course was generally by massive chunking. On a paved road course, most compounds wore by pattern abrasion. A few compounds worn on this course formed deep pockets parallel to the surface, resulting in the eventual loss of the large flaps between the pocket and the surface. Pattern abrasion was also found on T156 pads of four different compounds, tested on an M-1 tank on the paved road course. The abrasion patterns of both types of pads had a shingled appearance, with the ridges pitched so as to bite into the road surface. The abrasion patterns were characterized quantitatively by profilometry, using standard parameters calculated for surface roughness of metals and other materials. The ridge height and its ratio to ridge spacing correlated positively with wear rate on the paved road; whereas there was no correlation of ridge spacing with wear rate. The compounds which gave the lowest wear rate on the paved road, including the HNBR compounds, gave shallow ridges with little or no pattern.
Microencapsulated Antidegradants for Extending Rubber Lifetime
Authors: Evans Larry R. , Benko David A. , Gillick James G. , Waddell Walter H. 
Published: February 2011

Abstract
Microcapsules containing rubber antidegradants were formed in a spray-drying process. Studies were carried out to select the proper wall material based on the processing properties, migration rate of the antidegradant through the capsule wall, thickness of the capsule wall, and overall capsule diameter. The resulting capsules were incorporated into a rubber article, providing a reservoir of antidegradant during the exposure lifetime. Testing of the rubber compounds with microcapsules having diameters less than 50 µm containing AN-(l,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine in a matrix of cellulose acetate showed a significant increase in the crack-free lifetime of the rubber when flexed in exposure to ozone.
Recuring Vulcanizates. I. A Novel Way to Study the Mechanism of Vulcanization
Authors: Layer Robert W. 
Published: February 2011

Abstract
Vulcanizates, to which a curative is added by swelling, can be recured to easily study a variety of aspects of the vulcanization process, such as maturation, reversion, and even how much accelerator remains active as its zinc salt at the end of the cure. In effect, vulcanizates can be viewed as high-molecular-weight model compounds. In this study, we find that recuring SBR/BR vulcanizates, to which sulfur or the sulfur donor, N,N′ -dithiodimorpholine, is added, develops the same state of cure as the same amount of sulfur (or sulfur donor) added for the initial cure. This suggests that exchange reactions occur between crosslinks and the zinc-sulfur-accelerator complex during the cure and that all of the accelerator remains as its zinc salt at the end of the cure. This last result is interesting, since it is not consistent with the current view that most of the accelerator becomes irreversibly bound to the rubber and lost during the vulcanization of polybutadiene rubbers.
Self-Crosslinkable Polymer Blends Based on Chlorinated Rubber and Carboxylated Nitrile Rubber
Authors: Ramesh P. , De S. K. 
Published: February 2011

Abstract
Melt-mixed blends of chlorinated natural rubber and carboxylated nitrile rubber get crosslinked during prolonged molding at elevated temperatures in the absence of any crosslinking agent. Dynamic mechanical measurements show that such blends are compatible. The physical properties depend on the blend composition. The blends exhibit excellent processing safety, good oil resistance, and high abrasion resistance.
Electrical Conductivity of Barium-Ferrite-Vulcanized Polychloroprene Filled with Short Carbon Fiber
Authors: Jana P. B. , De S. K. , Chaudhuri S. , Pal A. K. 
Published: February 2011

Abstract
Short-carbon-fiber-filled polychloroprene composites, prepared by mill-mixing and cement-mixing methods were vulcanized by barium ferrite. The effects of concentration and aspect ratio (L/D) of short carbon fiber on volume resistivity have been studied. Composites prepared by the cement mixing method having high fiber aspect ratio (L/D 100) show higher hardness and modulus accompanied by lower elongation and volume resistivity than the composites prepared by the mill mixing method, which give low fiber aspect ratio (L/D 25). Experimental values of volume resistivity agreed reasonably well with the calculated values from the theory based on probability of formation of conductive network. The temperature dependence of volume resistivity of the composite shows a positive temperature coefficient. The shape of the hysteresis loop, observed during the heating and cooling cycle in the variation of volume resistivity with temperature, depends on the concentration and aspect ratio of short carbon fiber. Hall-effect studies indicate that increase in fiber concentration and aspect ratio in the composites causes increase in carrier concentration and decrease in mobility of the carriers. With increase in temperature, both conductivity and carrier concentration decrease and mobility of the carriers increases.
Studies on a New Binary Accelerator System for the Sulfur Vulcanization of Styrene—Butadiene Rubber
Authors: Mathew George , Pillai P. Viswanathan , Kuriakose A. P. 
Published: February 2011

Abstract
The chemical reactions involved when a binary accelerator system is used in rubber vulcanization varies with the systems used. The exact mechanism of these reactions is not fully understood even now. Accelerators in which sulfur is combined as S—S, C—S—C, or S—N are generally inactive at low vulcanization temperatures because of the high thermal stability of their sulfur bonds. But sulfur-containing nucleophiles such as thiourea or its derivatives enable accelerators like TMTD or CBS to operate at lower vulcanization temperature, indicating a nucleophilic reaction mechanism in these vulcanization reactions. But, no conclusive evidence is given for such a postulate. In the present study, 1-phenyl-2,4-dithiobiuret and 1,5-diphenyl-2,4-dithiobiuret, which are more nucleophilic than thiourea but which vary in their nucleophilic reactivity, were tried as secondary accelerators in binary systems containing TMTD or CBS in sulfur vulcanization of SBR. Both the above dithiobiurets were found to reduce the optimum cure time considerably compared to the reference mixes. 1-phenyl-2,4-dithiobiuret, which is more nucleophilic than 1,5-diphenyl-2,4-dithiobiuret, is found to reduce the optimum cure time more, showing a nucleophilic reaction mechanism in the systems under review. In both cases, the optimum dosage of the secondary accelerator required has been established. The vulcanizates obtained with these new systems showed definite increase in tensile properties and good retention of these properties after aging. In the evaluation of other physical properties, these vulcanizates gave promising results. In order to correlate these physical properties to the type of chemical crosslinks formed, chemical characterization of the vulcanizates was also carried out. Also, to study the effect of these nucleophiles on the temperature of vulcanization, these mixes were cured and evaluated at two different temperatures, viz., 120°C and 150°C. To overcome the lower green strength and gum tensile strength in SBR, incorporation of fine reinforcing fillers and the use of special combinations of accelerators is required. In this context, the study was extended to evaluate the effect of fillers—carbon black, precipitated silica, and china clay—on the cure characteristics and vulcanizate properties.
Electrical Conductivity of Thermo-Oxidatively-Degraded EPDM Rubber
Authors: Mattson Bengt , Stenberg Bengt 
Published: February 2011

Abstract
Oxidative degradation of rubbers, and the development of oxidized layers at the surfaces, results in increased electrical conductivity. This paper shows that for EPDM rubbers heavily oxidized at 200° C, the DC-conductivity increases more than two orders of magnitude, and the percolation threshold for DC conductivity is decreased below 5 phr carbon black. The effect of oxidation upon the electrical properties is explained as being due to the presence of polar groups, e.g., carbonyl groups, in between the carbon-black agglomerates which provide shorter distances for the electrons to tunnel through.
Rubber Process Oils for Peroxide Curing of Ethylene—Propylene Elastomers
Authors: Chasey Kent L. 
Published: February 2011

Abstract
Ten rubber process oils were evaluated in a peroxide-cured EPDM compound. The effects of the process oil on cure-development characteristics and stress—strain properties are discussed. Certain types of molecular structures in the oil can significantly interfere with free-radical vulcanization, and analytical methods for the detection of these structures are provided. The combined effects of the process oil and the peroxide—coagent concentration are also described.
Solid-State C-13 NMR Studies of Vulcanized Elastomers X. N-t-Butyl-2-Benzothiazole Sulfenamide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75.5 MHz
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
Accelerated sulfur vulcanized cis-polyisoprene was analyzed using C-13 solid-state NMR to determine the chemical microstructure of the network. Three formulations were analyzed consisting of varying accelerator/sulfur ratios. All formulations yielded similar network structures, but the amount of sulfurization varied with sulfur concentration. At low percent cure, only polysulfidic A-type cis-structures were found. For longer cure times, the A-type structures shortened to monosulfldic, and B-type polysulfidic structures, both cis and trans, were formed. The amount of trans-sulfurized product was constant with cure once this resonance appeared. No isomerization, chain scission, saturation, or double bond migration was detected. The NMR measurements appeared to show fairly good agreement with equilibrium swelling measurements.
A Review of Group-Transfer Polymerization
Authors: Brittain William J. 
Published: February 2011

Abstract
Group-transfer polymerization is a very useful synthetic method for the preparation of acrylic ester polymers. This living polymerization process works well at room temperature and can be used to prepare a wide variety of complex polymer structures. Mechanistic work suggests that GTP is a form of anionic polymerization where propagation occurs via a small concentration of enolate anions which are in equilibrium with dormant silyl ketene acetal chain ends. GTP will find the most use in specialty applications including dispersants, toners, photoresists, and rheology control agents.
Polymer Surface Modification
Authors: Waddell Walter H. , Evans Larry R. , Gillick James G. , Shuttleworth Derek 
Published: February 2011

Abstract
Surface modification as a technology has been employed in various ways for many years, however, the breadth and magnitude of its applications have grown significantly during the last decade. Much of this growth has been facilitated by the development and spread of rapid and reliable surface characterization techniques. And, as would be expected of a maturing field, the bulk of investigations are now turning to applications rather than a pure understanding. Publications in both the scientific literature and patents describe research on a diverse range of polymeric substrates and potential applications using a wide range of modification techniques. Methods include chemical, photochemical, and high-energy physical techniques to modify polymer surfaces. Searches were made of these methods as applied to the surface modification of polymeric materials of particular interest to the rubber industry. Chemical methods include reactions such as halogenation, addition, etching, and oxidation. Photochemical techniques include surface reactions such as oxidative and nonoxidative degradation, halogenation, and photografting. Physical methods include corona discharge, plasma, electron and ion beam treatments. The 1980's literature on these subjects is published in a variety of languages, including a number of informative review articles and books printed in English on various aspects of this subject. The subject of this review concentrates on the surface modification of polymeric materials of particular interest to the rubber industry by focussing largely on scientific literature published in English and patent literature published during this time period that describe interesting and useful surface chemistry on elastomer substrates and rubber articles containing polymers such as natural rubber, cis-polyisoprene, styrene-butadiene copolymer, nitrile rubber, silicone, etc, and fibers and fabric made from fiber-forming polymer materials such as aramid, nylon, polyester, and carbon fiber, and those techniques reported successful in altering their surfaces. For organizational simplicity, three basic categories are used: elastomers, fibers and others. The latter category refers to those substrates without specific, current application in the rubber industry, but which have interesting or novel scientific features. Restriction of interest to rubber-relevant materials greatly reduced the scope of this work, and the interested reader should be aware that a great deal of activity is to be found in the rigid plastic and, to a lesser extent, biopolymer industries.