bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Viscosity of Carboxy-Terminated Polybutadienes
Authors: Kraus Gerard , Gruver J. T. 
Published: February 2011

Abstract
Newtonian viscosities have been determined for carboxy-terminated polybutadienes varying in microstructure, molecular weight and degree of carboxy-functionality. The latter was varied by total or partial methylation of initially di- or mono-functional polymers. The viscosity of non-functional (methylated) polybutadienes is shown to be proportional to the 3.4 power of the weight average chain length, irrespective of microstructure, provided the comparison is made at equal (T−Tg). The temperature dependence of viscosity is well represented by the Vogel equation, with constants given by Berry and Fox for polybutadiene of 8% vinyl unsaturation, again independent of microstructure. The presence of carboxy end groups increases the viscosity as a result of an association equilibrium with raises the effective molecular weight of the polymer. The absolute magnitude of the temperature coefficient of viscosity increases with carboxy-functionality, as required by the postulated association equilibrium. Theoretical calculations show that the viscosities of mono-carboxy polybutadiene and α,ω-dicarboxypolybutadiene cannot be reconciled unless some of the carboxy-associations in the latter are intramolecular. In the molecular weight range considered the glass temperature is substantially independent of carboxy-functionality.
Some Aspects of the Relationship between Molecular Structure and Flow Behavior of Polymer Melts
Authors: Blyler L. L. 
Published: February 2011

Abstract
The shear dependent viscosity and related properties of a number of ethylene polymers of differing molecular structure have been characterized using a capillary extrusion rheometer. The structural aspects of interest were average molecular weight, branching, and the presence of strong intermolecular secondary forces. It was found that average molecular weight influences the degree of shear dependence of the viscosity, branching affects both flow activation energy and the nature of the observed “melt fracture” phenomenon, and intermolecular hydrogen bonding enhances viscosity and activation energy and leads to increased shear dependence of flow behavior. The results are interpreted in terms of specific molecular mechanisms.
Thermoelastic Behavior of Natural Rubber
Authors: Shen Mitchel C. , McQuarrie Donald A. , Jackson Julius L. 
Published: February 2011

Abstract
Stress—temperature measurements of natural rubber were carried out up to the elongation ratio, α, of 2.0. An automatic stress relaxometer was constructed for this purpose which can be completely enclosed in a controlled environment. Experiments were so conducted as to minimnze possible chemical effects and nonequilibrium conditions. Relative internal energy contribution to stress, fe/f, is calculated as a function of α in terms of statistical and thermodynamic theories. Both of these yield similar results. It is shown that in the region of low strains (1.0&lt;α&lt;1.5),fe/f decreases rapidly with increasing α, but appears to remain constant at 1.5&lt;α&lt;2.0. This observation is not in agreement with the prediction of the current statistical theory of rubber elasticity, which stipulates that the energy effects are intramolecular and independent of deformation. Implications of these findings are discussed. It is suggested that perhaps at low strains the intermolecular interactions are large in comparison with intramolecular energies, but become relatively insignificant at higher elongation ratios. The temperature coefficient of unperturbed chain dimensions is also calculated from thermoelastic data. It is constant only in the region 1.5&lt;α&lt;2.0. Finally, a new, more exact derivation of the Elliott—Lippmann anisotropy factor in terms of the statistical theory is given in the Appendix.
Evidence for Chemical Interaction in Carbon and Polymer Associations. Butyl and Acidic Oxy Blacks. The Possible Role of Carboxylic Acid Groups on the Black
Authors: Gessler A. M. 
Published: February 2011

Abstract
Assuming that the enhanced reinforcement capacity of oxidized black in butyl is related specifically to acidity provided by carboxyl groups on the surface of the black, the black was neutralized by esterification and saponification, respectively. The reduced carbon-polymer bonding activity resulting from these neutralizations is discussed in the light of the cationic interaction mechanism which it is proposed is involved.
Thermal Analysis of Butadiene Styrene Block Copolymers
Authors: Anderson J. N. , Weissert F. C. , Hunter C. J. 
Published: February 2011

Abstract
The Gordon—Taylor—Wood relationship between composition and glass temperature has been used as the basis of a DTA method for block styrene analysis in butadiene styrene copolymers having the same microstructure and a similar compositional distribution. The determined K value of the Gordon—Taylor—Wood equation for these polymers prepared with a butyllithium catalyst is in fair agreement with values previously determined for emulsion butadiene styrene copolymers. The total styrene content of the copolymer was determined using the refractive index method, and the composition of the “non-block” segment of the copolymer was obtained from DTA measurement using a Tg as a function of composition graph The amount of block styrene can then be obtained by difference. Evidence is presented supporting the validity of the method, and the results are compared with those obtained by a chemical method which involved polymer degradation by a hydroperoxide in the presence of osmium tetroxide. The thermal analysis requires approximately one-half hour. All measurements are made on the dry polymer eliminating the necessity of redissolving the polymer as required by most other methods of analysis.
A New Improved Tirecord Fatigue Tester
Authors: Forster M. J. , Prettyman I. B. 
Published: February 2011

Abstract
Based on the illustrations presented, it is suggested that the SCEF fatigue tester has given realistic results, consistent with general principles established in tire dynamics analysis and performance. It has done this with a simple test specimen, yet one which locates the test cord in an environment similar to that found in service. Testing results have been reproducible and obtained in a reasonable time. It is felt that it will make a unique and meaningful contribution to the laboratory evaluation of fatigue performance characteristics of a tirecord.
A Peroxide Curing Butyl Rubber
Authors: Oxley C. E. , Wilson G. J. 
Published: February 2011

Abstract
The reactions of peroxides with polymers have been studied for some time. They form an extensive part of vulcanization technology. Two types of reactions are generally recognized, those leading to crosslinking between polymer chains and those leading to scission of the chains. Natural rubber, polybutadiene and ethylene-propylene rubber are examples of polymers in which crosslinking reactions take place to a greater extent than reactions leading to chain scission and these polymer reactions with peroxides form a useful method of vulcanization. On the other hand, polyisobutene is an example of a polymer which degrades extensively and for polyisobutene and butyl rubber, peroxides have not found use as cross-linking agents.
The Correlation between Entanglement and Chemical Crosslinks in EPDM Vulcanizates
Authors: Baldwin F. P. , Borzel P. , Makowski H. S. 
Published: February 2011

Abstract
Using peroxide cured specimens prepared from a selected EPDM terpolymer containing olefinic residues derived from ethylidene norbornene, and Young's modulus measurements taken in compression on n-heptanc swollen vulcanizates, a correlation between the apparent total, effective network chain density and the chemical network chain density has been derived. The type of correlation equation used may be generally useful.
The Engineering of Polymers for Mechanical Behavior
Authors: Kelley F. N. , Williams M. L. 
Published: February 2011

Abstract
The broad subject matter in this paper is treated in only cursory fashion. Our intent was to present an approach to the systematic analysis of the relationships between engineering properties and molecular variables for viscoelastic materials. Literature omissions will undoubtedly be numerous, but the basic concept of the Interaction Matrix allows for continual upgrading and refinement. The examples chosen were based on the stress relaxation modulus which provided an ideal starting point due to the wide use of this property in viscoelastic stress analysis and fracture mechanics. Other important engineering parameters which might be selected for similar examination include bulk compressibility and dilation for example; and, of course, the rupture properties under various imposed stress fields.
Transfer of Labeled Hydrogen between Elastomers and Carbon Black
Authors: Papireb E. , Voet A. , Given P. H. 
Published: February 2011

Abstract
Radioactive hydrogen exchange was studied between tritium labeled carbon blacks and elastomers as well as between tritium labeled elastomers and carbon blacks, after solvent mixing and after milling. A substantial exchange was observed upon solvent mixing of an unsaturated elastomer (SBR) and a reinforcing black (HAF), with commercial blacks as well as in carbon black samples from which surface oxide groups were removed by calcination. Milling did not significantly increase the hydrogen exchange. Nonreinforcing blacks did not show any exchange. Saturated elastomers, such as butyl rubber, which bond predominantly to the carbon black particles by means of surface oxide complexes, did not show any significant hydrogen exchange, not even with channel blacks. The phenomena could be adequately explained by assuming as the material basis of reinforcement of unsaturated elastomers a process of chemisorption through abstraction of reactive hydrogen from the elastomer to a reactive site on the carbon black surface, followed by a chemical reaction of the resulting elastomer free radical chain with another reactive carbon black site. Thus, active sites on the carbon black surface and reacting hydrogen in the unsaturated elastomer are the determining factors in reinforcement.
Low-Frequency Losses in Rubbers Cross-Linked in the Presence of Diluent
Authors: Langley N. R. , Dickie R. A. , Wong Chiu-ping , Ferry J. D. , Chasset R. , Thirion P. 
Published: February 2011

Abstract
Measurements of the complex shear compliance have been made from 0.1 to 7 cycles/sec and from − 5° to 45° C on several samples of natural rubber cross-linked by dicumyl peroxide in the presence of a diluent oil (volume fraction of rubber, v2=0.63 and 0.76) which was subsequently extracted. The properties of the extracted vulcanizates were compared with those having the oil still present and with those of conventional undiluted vulcanizates. Measurements of the diffusion coefficient of radioactively tagged n-hexadecane in trace amounts through the polymer structure were also made both before and after extraction of the oil. The diffusion coefficient was higher in the presence of the oil by an amount consistent with the Fujita theory for concentration dependence of diffusion rate based on free volume considerations. The low-frequency mechanical losses (reduced to 25° C by the method of reduced variables), as measured by the loss tangent, were shifted to higher frequencies by the presence of oil to a much larger degree than would be expected from the difference in local mobility gauged by the diffusion coefficient. The equilibrium modulus, derived by extrapolation to zero frequency, was diminished by the presence of oil to a greater extent than the factor of v21/3 expected from the simple theory of rubberlike elasticity. The low-frequency losses in the extracted vulcanizates were smaller than those in conventional vulcanizates with comparable degrees of cross-linking; the differences are attributed to differences in network topology.
Effect of Oil and Black on the Injection Molding of EPDM Compounds, II, Molding Studies
Authors: DePierri W. G. 
Published: February 2011

Abstract
The results which we discussed in this paper show that the demands made on the compound in an injection molding operation are more severe than those made by compression molding. The flow properties of the compound are much more critical in injection molding because of the high flow rates which are encountered. Compounds must have viscosities which are low enough to allow the mold to fill completely in the injection step. The level of oil and black in the compound are very important factors in controlling compound viscosity. The cure system is more critical, for it must give good physical properties at the elevated temperatures used in injection molding. The ability to attain good physical properties at low cure temperatures does not necessarily mean that good properties will be achieved at elevated cure temperatures as was shown by the comparison of physical properties of specimens prepared by high temperature injection and low temperature compression molding. The physical properties of injection molded specimens made from some compounds cured at high temperatures indicated a lower state of cure at optimum cure than compression molded specimens cured at lower temperature. Much of this effect can be explained by changes in state of cure caused by the increased temperature. The oil type used in the compound did not appear to be especially important in determining the physical properties of molded items. Oil level, however, is an important factor in determining both the processability of a compound and the physical properties of the finished product. Some of the problems associated with injection molding of EPDM compounds encountered in this work may result from the experimental injection molding equipment used in the study and may not be evident when commercial equipment is employed. Other of the problems could be solved by compounding, especially by changes in the cure system.
Analysis of Tire Tread Rubbers by Gas Chromatography
Authors: Ney E. A. , Heath A. B. 
Published: February 2011

Abstract
A method is presented which allows the simultaneous quantitative determination of natural rubber, polybutadiene and SBR in tire components. The method consists in pyrolyzing samples of cured and filled ternary rubber mixtures at 450°–550° C and subjecting the decomposition products to programmed gas chromatography. The quantities of dipentene, vinyl cyclohexene, and styrene formed during pyrolysis are then used to determine the percentage ratio of natural rubber, polybutadiene and SBR in the vulcanizate.
Skeletal Deformation Vibrations and Rotational Isomerism of Methylbutenes and Methylpentenes as Model Compounds of 1,4-Polyisoprene
Authors: Shimanouchi T. , Abe Y. 
Published: February 2011

Abstract
Infrared spectra of methylbutene and methylpentenes in the skeletal deformation region have been measured. The force constants for the skeletal deformation vibrations are determined from the frequencies of isobutylene, isobutylene-d6, and methylbutenes. The frequencies of methylpentenes are calculated for the various conformations, and the stable rotational isomere determined. The energy differences between the isomers are determined from the temperature dependence of the spectra. These results are correlated with the conformations of cis- and trans-1,4-polyisoprene chains, and possible conformations are suggested.
The Effect of Crosslink Structure on the Tensile Strength and Oxygen Absorption Characteristics of Natural Rubber Vulcanizates
Authors: Lal J. 
Published: February 2011

Abstract
The chemical nature of crosslinks in natural rubber—sulfur—diphenylguanidine vulcanizates was modified by reaction with triphenylphosphine under nitrogen to determine the effect of this change on tensile strength and oxygen absorption characteristics of the vulcanizates. The vulcanizates were characterized by organically combined sulfur and polysulfidic sulfur. Polysulfidic crosslinks, i.e., crosslinks containing three or more sulfur atoms in the crosslink, were found not to be essential for the attainment of high tensile strength in these vulcanizates. Data for the samples which had lost significant amounts of polysulfidic crosslinks by reaction with triphenylphosphine fitted the tensile strength versus 300% modulus curve for the control samples. Vulcanizates which had been reacted with triphenylphosphine for 16 days at 80° C, had lost 95–99.6% of their polysulfidic sulfur. These triphenylphosphine-reacted vulcanizates exhibited significantly lower rates of oxygen absorption at 100° C as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.
Rapid Stress-Induced Crystallization in Natural Rubber
Authors: Mitchell J. C. , Meier D. J. 
Published: February 2011

Abstract
Stress-induced crystallization in a rapidly stretched natural rubber gum vulcanizate has been studied using thermal techniques to follow the development of crystallinity. A special-purpose analog computer has been assembled and used online to process the thermal and mechanical data obtained in high speed tensile testing. Roughly first-order room temperature crystallization kinetics curves were obtained having time constants of 50–60 msec in the range of 400–540% extension. While the rate of this rapid, presumably primary crystallization appears rather insensitive to elongation in this limited range, the extent of crystallization at 400 msec increases smoothly from zero at 340% elongation to around 18% at 540% elongation. It is shown that our high-speed tensile tester can stretch this vulcanizate fast enough that most of the crystallization takes place after extension has been completed. Stress—strain curves obtained at this high rate are compared with those obtained at lower rates where crystallization takes place during the stretching.
Friction and Frictional Rise of Wedge Sliders on Rubber
Authors: Schallamach A. 
Published: February 2011

Abstract
The friction of wedge sliders on rubber depends surprisingly little on the angle between their leading faces and the rubber surface. Friction remains moderate even when this angle is 90°. A simple theory is put forward which accounts qualitatively for the observed limitation of the frictional force and which also predicts an experimentally verified lift of the sliders. In agreement with these findings, a photoelastic investigation of the stress distribution around the sliders reveals that no ramming pressure precedes them in the rubber. The absence of a ramming pressure is attributed to a forward tilt of the rubber which originates from the couple of the frictional force with respect to the undeformed rubber underneath.
Research for a Uniform Quality Grading System for Tires
Authors: Brenner F. C. 
Published: February 2011

Abstract
The National Traffic and Motor Vehicle Safety Act of 1966 requires the establishment of a uniform quality grading system. This paper discusses the needs for the system and the complexity of the problem. The system proposed here will depend on five properties; tread wear, traction, impact resistance, endurance, and wheel speed capability.
Mastication of Elastomers II. Cold Mastication of Natural Rubber
Authors: Bristow G. M. 
Published: February 2011

Abstract
The cold mastication of natural rubber in oxygen is shown to proceed rather more rapidly than that in air. Reasons for this difference are considered. Mastication under these conditions is considered as a low temperature oxidative process and consistent with this the subsequent reactions of RO2 radicals produced by mechanical shear are shown to lead to some additional chain scission. The thermal oxidation of rubber masticated in oxygen is rather more rapid than that of rubber masticated in nitrogen in the presence of a radical acceptor.
Effect of Carbon Black Dispersion on the Mechanical Properties of Rubber Vulcanizates
Authors: Boonstra B. B. , Medalia A. I. 
Published: February 2011

Abstract
A study has been made of the mechanics of mixing of carbon black in rubber by determining the influence of agglomerates in the mix on the final properties of the vulcanizate. It is suggested that the mixing starts with the forming of soft agglomerates which contain polymer and black in about the proportion of the void ratio aa determined by oil absorption. In subsequent stages these agglomerates are torn apart— to smaller and smaller sizes and finally dispersed. When the agglomerates that are first formed in the mix are left intact as is the case in a very short mixing cycle, a noticeable deteriorating effect is found on the mechanical properties relating to rupture (tensile, abrasion). On the other hand, viscosities and moduli for short mixing cycles can be higher by a factor of 2 or more than the final viscosity and modulus after all the black is apparently well dispersed. This has been shown both experimentally and theoretically. Hard particles have also been added intentionally to assess the effect of their size, frequency and chemical nature. It appears that hard particles in an amount of 10–20% of the total black become very harmful at an average diameter of about 1 µ. At the 0.5 µ size, particles of medium thermal black are almost without influence on service properties of the vulcanizate such as tensile and tear strength, abrasion resistance, etc. Above the critical size, the size of the particle has little influence on the reduction in mechanical properties. This reduction is determined by the amount (by weight) of the coarse particles present. The effect of these hard particles on tensile and abrasion is much greater than that of the soft agglomerates formed in short mixing cycles.
Theory for the Meridian Section of Inflated Cord Tires
Authors: Day R. B. , Gehman S. D. 
Published: February 2011

Abstract
The general equation for the equilibrium shape of an ideally thin, flexible, inflated, undeflected cord tire is derived from the equilibrium conditions for an individual cord. Various special cases are discussed and equations are derived for the cord tension, bead tension, and shearing stress between plies.