bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contributions of Elastomer Behavior to Mechanisms of Carbon Black Dispersion
Authors: Nakajima N. , Harrell E. R. 
Published: February 2011

Abstract
In order to achieve good mixing of elastomer and carbon black, the elastomer domains must be reduced in size, that is, the elastomer must be broken into smaller pieces. If this is the only requirement, Region I of the Tokita-White scheme may be most preferred, because the elastomer easily breaks up at this state. However, it is too stiff for compaction of the compound; that is, the elastomer is too stiff to conform to the complex topology of carbon black. If the compaction is the only requirement. Region IV is most preferred, because the material is in the melt-flow state. In reality, Region II, the rubbery, highly stretchable state gives the best result. It appears that the use of Region II is a compromise. However, there is a more important reason for the preference of Region II, that is, the effectiveness of this region for the breakdown of carbon black agglomerates. The breakdown mechanism involves elastomer as a medium for the transfer of force. The effectiveness of the elastomer medium depends on its ability to stretch with the development and maintenance of a high stress. The former may be characterized by the failure envelop and the latter by the stress relaxation experiments. In roll mill as well as internal mixer processing, the folding of compound and the subsequent stretching of it, e.g., lamination mechanism, are the effective means for carbon black dispersion. It is postulated that the lamination mechanism generates localized high shear fields, which force carbon black agglomerates to rotate in the high modulus medium; this results in peeling of the aggregates from the outer shells of the agglomerates.
A Parametric Study on Interlaminar Shear Strains in Cord-Rubber Composites
Authors: DeEskinazi J. , Cembrola R. J. 
Published: February 2011

Abstract
The effect of different design variables used in the construction of tire belts on the interply shear phenomenon was studied using a simple, belted cylinder structure. Only balanced belt constructions were considered. The finite element method was used in the analysis of the belted structure. Predicted results were verified by performing experiments with selected combinations of the design parameters studied. Predicted and experimental results indicate the presence of interply shear strains in the cross-sectional plane of the belts; however, due to difficulties involved in measuring these strains experimentally, they have not been treated in this study. Results for shear strains in the circumferential planes only have been presented. Results for the interply shear strains at the belt edge indicate that the belt cord angle has a very strong influence on the interply shear phenomenon. It was shown that the shape of the curve depicting the relationship between cord angle and interply shear strains is influenced by other design variables of the belt as well as properties of adjacent plies, such as the bladder used to simulate a radial tire carcass ply. Interply shear strains decrease with increasing thickness between the plies and modulus of the interply rubber. In the case of a stiffer rubber, the reduction in shear strain is entirely due to a reduction in the relative motion between the belts. However, in the case of an increased interply thickness, which is accompanied by an increase in relative motion between the belts, the reduction in shear is the result of the relative motion being distributed over a larger thickness. Increasing the belt cord modulus results in an increase in interply shear strains for relatively low values of the modulus. However, beyond a certain value, approximately the modulus of fiberglass cords, increasing the cord modulus does not significantly affect interply shear strains. The shear strain-belt width relationship is strongly influenced by the cord angle used in the belts. Depending on the value of the latter, the shear strain can be a decreasing function of belt width or remain relatively constant as belt width is varied. The degree of localization of the interply shear phenomenon at the belt edge was also studied. All of the variables considered in this study, with the exception of the cord modulus, seem to affect the distribution of the shear strain along the width of the belt to varying extents. The belt width seems to have a strong influence, with wider belts resulting in significant shear strains confined to the vicinity of the belt edge.
Structure-Property Relationships of Perfectly Alternating Polycarbonate-Polydimethylsiloxane Block Copolymers, Part II
Authors: Tang S. H. , Meinecke E. A. , Riffle J. S. , McGrath J. E. 
Published: February 2011

Abstract
The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.
Cryoground Rubber-Natural Rubber Blends
Authors: Phadke A. A. , Chakraborty S. K. , De S. K. 
Published: February 2011

Abstract
Addition of cryoground rubber (CGR) causes changes in curing characteristics (decrease in Mooney scorch time, optimum cure time, and reversion time) and shows a detrimental effect on most of the vulcanizate properties (tensile, resilience, flex, hysteresis, set, and abrasion). Tear strength, however, is not adversely affected by CGR. Higher doses of curatives (sulfur 3.5 phr and acelerator 1.4 phr) and addition of reinforcing carbon black make up the losses in physical properties. Scanning electron microscope fractographs show that there is little adhesion between natural rubber and CGR. But addition of carbon black overshadows the effect of CGR, and the fractographs show the characteristics of black-filled vulcanizates.
Tack and Related Properties of Isopropyl Azodicarboxylate Modified Polybutadiene
Authors: Hamed G. R. , Shieh C-H. 
Published: February 2011

Abstract
Polybutadiene has been modified by reaction with isopropyl azodicarboxylate (IAD). The reaction is quite efficient, resulting in a structure in which there are pendant hydrazoester groups dangling from the BR backbone. The Tg's of the modified polymers increase with IAD content. Eventually, at high levels of modification, two Tg's are observed, indicating the presence of two phases. Infrared analysis indicates the presence of H-bonding within the modified polymers. The green strength of these polymers increases with IAD content, whereas, tack passes through a maximum with increasing IAD level. At low IAD levels, the increase in green strength is attributed to increased polar interactions between chains, whereas, at higher IAD levels, there appears to be an additional contribution from strain-induced phase separation (see Reference 1). This type of behavior is favorable for high tack. The initial increase in tack as IAD is incorporated is due, in part, to the enhanced green strength. A more important feature is that the green strength is enhanced without great loss of the molecular mobility needed to form a tack bond. This occurs because of 1) the slow rise in Tg and 2) a lowering of the entanglement density with modification. Blocky additions of the IAD contributes to the former effect as does the presence of the alkyl group (isopropyl) in the polar IAD moiety. Additionally, it is inferred that the IAD-BR molecules do not have to interdiffuse as far across the interface to develop a strong tack bond as do purely hydrocarbon BR chains. Evidence for this is the rapid initial increase in relative tack for the IAD modified elastomers. Finally, the loss of tack at high IAD levels is due to a severe decrease in chain mobility, thereby prohibiting the formation of an extensive tack bond.
Advances in SEM of Polymers
Authors: White J. R. , Thomas E. L. 
Published: February 2011

Abstract
We hope that this review contains convincing evidence of the value of scanning electron microscopy in polymer studies. Much information has been provided by this technique which could not be obtained by any other means. We hope, too, that we have indicated the kinds of problems that are confronted when dealing with this class of materials. Charging can be a problem, but this can normally be countered by applying a conductive coating. More serious is radiation damage, which may cause image deterioration and artifact production. Sometimes this will obscure the features about which information is sought and could lead to false interpretation. Proper controls should be applied and observations made at several magnifications and several beam potentials and currents to establish the best conditions. Although we have emphasized the difficulties that may be encountered when studying polymers in the SEM, many polymers provide very easy subjects, especially if high resolution (∼ 10 nm) is not sought, and standard SEM procedures are very straightforward. We hope that the value of the technique indicated by the many successful applications to which we have referred will act as sufficient incentive to outweigh any deterrent message that might be derived from our more cautionary passages relating to the difficulties.
Dispersive Mixing in Rubber and Plastics
Authors: Manas-Zloczower I. , Nir A. , Tadmor Z. 
Published: February 2011

Abstract
Most useful plastics and rubber products are mixtures of pure polymers or copolymers with a variety of additives such as pigments, stabilizers, antioxidants, flame retardants, crosslinking agents, fillers, reinforcing agents, plasticizers, foaming agents, etc. Moreover, much attention is being placed recently on the preparation of blends of polymers, leading to products of unique properties. The distribution of additives into the polymeric matrix and the detailed topological structure of the blends depend on the nature of the mixing mechanisms, hence they are intimately related to the mixing equipment configuration and mixing operating conditions. It is convenient to distinguish between two mixing mechanisms extensive and intensive or dispersive. The former, in the very viscous polymeric systems, is achieved by and large by convection. It may either be distributive or laminar. Distributive mixing may involve an ordered or random rearrangement process. Laminar mixing is achieved by imposing on the material permanent deformation in various laminar flow patterns (e.g., shearing, squeezing, or elongational flows). The objective of extensive mixing is to bring about composition uniformity throughout the mixture. For extensive mixing, large strains have to be imposed upon the liquid. This requirement, however, must be complemented by the equally important requirement of distribution of interfacial elements (or solid additives) throughout the system. Initial orientation and spatial location may be critical in laminar mixing. Dispersive mixing generally involves rupture of agglomerates formed by a solid phase and separation of closely packed particles after rupture. This is followed by the distribution of the separated particles throughout the polymeric matrix, which of course, is an extensive mixing step. The most investigated dispersive mixing operation is that of carbon black into rubber. The mechanical properties of the rubber are directly affected by carbon black dispersion. In this review, dispersive mixing mechanism and equipment are reviewed. Although the emphasis is on rubber-carbon black systems, the discussion is relevant to dispersive mixing operations of other solid fillers in rubber and plastics as well as to dispersion of one liquid polymeric phase in another (homogenization) as in blending of polymers. First, mixing equipment and its hydrodynamic analysis are reviewed. Next, the chemical and physical characteristics of some of the solid additives, specifically carbon black, are discussed. The dispersion of the solid particles takes place in various deformation fields. Hence, the behavior of single particles in flow field, of doublets and swarms of particles is relevant, as well as the interaction between particle and matrix. Finally, various postulated dispersive mixing mechanisms, consequent scaleup techniques, and the quantitative characterization of the mixture are discussed in some detail.
Polymer-Bound Antioxidants
Authors: Kuczkowski J. A. , Gillick J. G. 
Published: February 2011

Abstract
The service demands placed on finished rubber products continue to increase year after year. Tires, hose, automotive belts, and components are expected to perform without failure for periods which are now two to three times those expected just ten years ago. Many of these increased demands are the result of radical and innovative changes in the design and construction of rubber products. One obvious change has been the change from bias ply to radial passenger tire construction. This has increased the expected service mileage from approximately 20 000 miles (32 Mm) to over 40 000 miles (64 Mm). Other changes have resulted in response to environmental legislation. The switch to nonleaded gasoline has increased the aromatic content of our fuel. It has also resulted in the use of additional and different fuel additives such as methanol, ethanol, and t-butylmethyl ether. These aggressive solvent changes obviously affect the extractability of stabilizers from hose products. Additional legislation has changed mileage and pollution requirements for engines. This has, in general, increased the operating temperature under the hood, resulting in more severe aging conditions for belts, cables, and hoses. At the same time, it has increased the demands placed on seals and gaskets which are in contact with hot lubricating oils. Similar situations also apply in areas outside the automotive area. Rubber products used in the garment and carpet industries are also exposed to extraction conditions during detergent washing and dry cleaning processes.
The Effect of Variations in Chain Connectivity on Strain-Induced Crystallization in Unvulcanized EPDM Elastomers
Authors: Scholtens B. J. R. 
Published: February 2011

Abstract
The introduction of a small amount of chemical or physical crosslinks has an enhancing effect on SIC in EPDM. This situation results from a decrease in stress relaxation or creep, so that the individual chains are deformed more affinely. At the same time, there is no deleterious effect of crosslinks on the crystallization of nonstretched EPDM because of its copolymeric nature. Therefore, the higher connected chains have a smaller melting entropy upon stretching, which promotes the crystallization process. In both EPDM green rubbers and black compounds, the amount of crystallinity and the end-melting temperature increase considerably with strain, in contrast to literature reports. These are desirable qualities for rubber tack. In spite of the positive effect of a higher chain connectivity on SIC, chain connectivity has a detrimental influence on tack. This effect is the result of a drastic reduction in bond formation caused by diminished material flowability and chain interdiffusion. Hence, we conclude that a tack-grade EPDM should, preferably, contain no branched or lightly crosslinked structures.
Model Vulcanization of EPDM Compounds—Part II: Influence of Temperature and Time on the Vulcanization Products from Ethylidene Norbornane
Authors: van den Berg J. H. M. , Beulen J. W. , Hacking J. M. H. , Duynstee E. F. J. 
Published: February 2011

Abstract
Influence of vulcanization temperature and time on the sulfur crosslinks in vulcanized EPDM (third monomer ENB) was studied using the low-moleular model compound ENBH (C9H14). For each vulcanization condition (60 min at 180°, 160°, 140°, and 120° and 60, 30, 15, and 5 min at 140°), the nature of the crosslinks is represented by the composition of the C9H13−Sn−C9H13 vulcanization mixture as indicated by its HPLC chromatogram. In this way it is shown that increase in temperature favors formation of disulfidic crosslinks at the expense of the higher-sulfide crosslinks. Under the mildest vulcanization conditions (60 min at 120° or 5 min at 140°), disulfidic crosslinks are nearly absent and penta-sulfidic crosslinks are the most important.
Mechanisms of Antioxidant Action: Aromatic Nitroxyl Radicals and Their Derived Hydroxylamines as Antifatigue Agents for Natural Rubber
Authors: Dweik H. S. , Scott G. 
Published: February 2011

Abstract
Diarylnitroxyl radicals and their reduction products, the diaryl hydroxylamines are effective anti-fatigue agents for rubber, confirming the previously proposed mechanism of action of the diaryamincs. The nitroxyls are reduced by sulfur species formed during the vulcanization reaction to a mixture of hydroxylamines and parent amines, and these species act as reservoirs for the nitroxyl radical during fatiguing. Removal of the reservoir of reduced species by solvent extraction removes the antifatigue activity.
Correlation Analysis of Curing Agents
Authors: Morita E. 
Published: February 2011

Abstract
The linear correlation of the pKa to the σ* constants of the substituted phenylthio group indicates the validity of the σ* being equal to the sum of the Hammett's constant of these substituent groups and the σ* of the phenyl group (0.6). The inhibitory activity of the compound LSR depends on the reactivity of BtSSR with BtSH and the general stability of the mixed disulfides which form during the curing process. For BtSSR as accelerators, the Hammett's rule applies to scorch delay time versus σ* constant as the variable with negative slope in the LFER. In benzothiazole-2-sulfenamides, the 13C NMR chemical shift of the carbon at the 2-position of the benzothiazolyl group (C8) is consistently greater than the chemical shift at the carbon adjacent to the amino nitrogen (CN) in the same molecule. It indicates that the electronic distribution at the S-N bond is consistently more positive at the S atom and more negative at the amino nitrogen. The 13C NMR chemical shift at C8 is inversely proportional to the σ* constant of the amino substituents. A wider range of amino substituents is applicable for the correlation analysis with 13C chemical shifts than σ* constants as the variable. When benzothiazole-2-sulfenamides are used as accelerators, two linear relationships with slopes of opposite signs are obtained for the N-substituted phenyl and the N-alkyl sulfenamides, respectively, in the relationship of the scorch delay to the 13C8 chemical shift or the σ* constant. Longer scorch delay was obtained with the pertinent electron-withdrawing phenyl or the sterically hindered alkyl substituents. The more basic amino derivatives give a faster acceleration rate and a higher crosslink efficiency. A significant linear correlation was obtained for scorch delay versus Hammett's σ constant of the phenyl substituents of the N,N′-dithiobisformanilides as vulcanizing agents.
Investigation of Abrasion of Nitrile Rubber
Authors: Zhang S. W. 
Published: February 2011

Abstract
Abrasion of NBR appears as a dry (particulate) wear, similar to unfilled BR, NR, and SBR, and filled BR. The abraded surface seems textured on two scales: that of the ridges of the abrasion pattern and that of small particles of debris. The formation of macroridges on filled and unfilled NBR appears to involve two distinct ridges one formed after the other. First, fine and tightly spaced primary ridges, followed by rough and sparsely spaced secondary ridges. The abrasion pattern on unfilled NBR is relatively stable once steady state has been reached and the pattern has been fully developed. As for the filled NBR, both the scale and roughness of the secondary ridges are uneven, even if steady state has been reached completely. Wear rates of filled and unfilled NBR have been found to be proportional to an exponent n of the applied frictional work. The unsteady state rates of wear were also somewhat dependent on the number of revolutions of the test wheel. Both the proportionality coefficient k and exponent n are dependent upon the composition and also upon the wear state. The exponent n for unfilled NBR is greater than that for filled NBR, and for the unsteady state it is greater than that for steady state. Reversals in the relative rates of wear between filled and unfilled NBR are also observed at different severities of abrasion. This phenomenon perhaps reflects a competition between two different physical processes: crack growth and rupture of tongue tip. The dominant process may be crack growth at low severities of wear and rupture of the tongue tip at high severities of wear. Therefore, the fact that, at high severities, carbon black markedly reduces the rates of abrasion might be attributed to the tensile strength gain of rubber compounds due to reinforcement by carbon black.
Mechanisms of Antioxidant Action: The Antioxidant Activity of “Spin-Traps” in Rubber
Authors: Nethsinghe L. P. , Scott G. 
Published: February 2011

Abstract
A number of nitrones containing a partially hindered phenolic group are shown to be effective antidegradants for sulfur vulcanized rubbers. They exhibit a high level of antiozonant and antifatigue activity, but unlike commercial antiozonants they do not cause discoloration of light colored formulations. The new antidegradants are less effective than conventional additives as thermal antioxidants, but their performance as antifatigue agents and antioxidants is augmented by their use in combination with nonstaining antioxidants. The mechanism of action of the phenolic nitrones is believed to involve their oxidation to stable phenoxyl/nitroxyl radicals.