bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile Rupture of Rubber
Authors: Thomas A. G. , Whittle J. M. 
Published: February 2011

Abstract
The dependence of tensile strength of a number of vulcanizates on temperature has heen studied. A critical temperature θc is found for natural rubber at which an abrupt change in strength occurs. This temperature depends on degree of crosslinking and also on the nature of the vulcanizing system. The presence of carbon black filler increases the strength above θc but has little influence on the value of θc or the strength at temperatures below it. The behavior can be explained qualitatively in terms of a change in mechanism of rupture from essentially a tear process above θc to a crack growth process below it. The influence of vulcanizing system is mainly due to changes in the nature of the crosslink rather than changes in regularity of the main chain as shown by the rate of low temperature crystallization.
Physics of the Slipping Wheel. II. Slip under both Tractive and Lateral Forces
Authors: Livingston D. I. , Brown J. E. 
Published: February 2011

Abstract
The mechanics of the slipping wheel has been investigated further with respect to the general problem of slip in any direction under the action of any combination of lateral and tractive force exerted by the road. The tire was considered to have two main directions of anisotropy in the contact surface, and a theory was proposed connecting the resultant force vector with the resultant slip vector regardless of their orientation. The connection was established through the use of a quantity called the slip-modulus which contains the lateral and longitudinal stiffness moduli and the slip components. The behavior of a tire may then be described by a characteristic relationship between the force and the slip-modulus, as has been found for pure lateral or longitudinal slip. Experimental measurements from three literature sources on the effects of tractive on lateral force were used to deduce the characteristic relationships, which represented a considerable condensation of the data. Thus, the theory was confirmed. The pressure distributions underlying these relationships were also calculated by a method given in this work and their distortions attributed to an artifact of variation of the ratio of the coefficient of friction to stiffness modulus with slip.
Research for a Uniform Quality Grading System for Tires. III. Breaking Energy
Authors: Simon B. G. , Mandel J. , Brenner F. C. 
Published: February 2011

Abstract
A test procedure designed to classify tires according to their average breaking energy has been applied to a sample of passenger car tires. Data are reported on 127 different tires of all grades and types over a range of sizes. A scaling system is devised and applied to the data. It is found that the system leads to conclusions similar to those derived from the original data.
Micrography of a Triblend
Authors: Marsh P. A. , Mullens T. J. , Price L. D. 
Published: February 2011

Abstract
A micrographic study has been made of a banbury-mixed triblend consisting of natural rubber, neoprene and ethylene-propylene terpolymer, of the composition 50 NR/30 CR/20 EPDM, in a pure gum blend as well as loaded with 35 phr N-330 black. A combination of techniques was used, including phase microscopy and electron microscopy of frozen as well as of embedded sections. Each of the above techniques contributed to the final interpretation of the observed complex phenomena. In the pure gum blend natural rubber forms a continuous phase. Neoprene rubber shows a three dimensional network of large strands of an average width of about three microns. The EPDM is dispersed in small globules throughout the matrix, generally of less than one micron diameter. Three different blends were made in which the carbon black was added to one single elastomer and then cut back with the remaining elastomers. The fourth blend was made by incorporating black in a preblend of the elastomers. A systematic approach to the evaluation of the carbon black distribution in triblends is described and its importance to reinforcement discussed. Problems in measurement of zone sizes are explained. The affinity of the black for the various elastomers is indicated. A major conclusion is that carbon black does not transfer from one elastomer phase to another during mixing. Most of the findings are applicable to all blend systems.
Effects of Termonomers on Crosslinking Rate and Crosslink Structure of Ethylene Propylene Terpolymers
Authors: Kujimoto K. , Nakade S. 
Published: February 2011

Abstract
A study was made concerning both the rate of crosslinking and the structure of crosslinks of terpolymers that have dicyclopentadiene, 1,4-hexadiene, methylene norbornene, and ethylidene norbornene for termonomers so as to look into the role of termonomers during crosslinking of ethylene propylene terpolymers. In the study, activation energy and frequency factor were determined by the rate constant of crosslinking. And differences in crosslinks were analyzed by both chemical and physical methods. Infrared analysis to follow the consumption of double bonds was adopted to examine the manner of crosslinking. With respect to the magnitude of the rate constant, ethylidene norbornene was first, followed by 1,4-hexadiene, methylene norbornene, and dicyclopentadiene. The structure of termonomers affected the apparent activation energy and the apparent frequency factor was subject to the influences of said structure and others including the variation in the degree of unsaturation. During the early stage of crosslinking, the formation of the polysulfide crosslink was paramount to all others and the speed of conversion therefrom either to disulfide-type or to monosulfide varied with the kind of terpolymers and was in proportion to the rate constant of crosslinking.
Relationships between Chemical Structures of Crosslink Sites and Physical Properties of Vulcanized Rubbers. Part V. Analysis of Chemical Structures of Combined Sulfur in Crosslink Sites for Various EPDM Vulcanizates
Authors: Imoto M. , Minoura Y. , Goto K. , Harada H. , Nishihira K. , Fujita H. , Fujimoto K. , Izuta T. , Kono K. , Fujioka K. , Shiota A. , Oba M. , Oshita H. , Usamoto T. 
Published: February 2011

Abstract
Various EPDM vulcanizates with different chemical structures of crosslink sites, such as C—C, C—R—C and C—Sz—C linkage, were obtained by using a variety of curing agents. C—Sz—C linkage was separated into polysulfide linkage and monosulfide linkage by using the LiAlH4 method which was confirmed beforehand with model compounds. The relationships between the chemical structure of combined sulfur in the crosslink sites and the type of curing agents used were clarified. For example, the mole ratios of polysulfide linkage to all the combined sulfurs in the vulcanizates by using DCP—S8, TMTD, S8—TMTD and S8-zinc dimethyldithiocarbamate curing system were respectively 0.35, 0.25, 0.53 and 0.82 at 160° C for 45 minutes. But in DCP—S8 curing system considerable C—C linkages seemed to be formed in addition to the C—Sz—C linkage.
Relationships between Chemical Structures of Crosslink Sites and Physical Properties of Vulcanized Rubbers. Part VI. Oxidative Degradation of EPDM Vulcanizates
Authors: Imoto M. , Minoura Y. , Goto K. , Harada H. , Nishihira K. , Fujita H. , Fujimoto K. , Izuta T. , Kono K. , Fujioka K. , Shiota A. , Oba M. , Oshita H. , Usamoto T. 
Published: February 2011

Abstract
Relationship between the chemical structures of crosslinks and the degree of oxidative degradation of EPDM vulcanizates was studied by stress relaxation and oxygen absorption measurements. It was found that the vulcanizates having C—Sx—C crosslink showed slower stress relaxation than the vulcanizate having other crosslink structures, i.e., C—S—C, C—C, and C—R—C. It was thought that C—Sx—C bond would reduce the scission of the network in oxidative degradation, since some polysulfide compounds had the same effect of protecting scission as antioxidant. The similar results were obtained in oxygen absorption measurements. In the case of heat aging, the vulcanizate having C—Sx—C linkage increased in crosslinks during aging and the rate of crosslinking was equal to the rate of scission of the network in the early stages, but the vulcanizates having other types of crosslinks did not show such behavior.
An Infrared Analysis for Ethylidenenorbor-Nene in Ethylene—Propylene—Ethylidenenor-Bornene Rubber
Authors: Levine I. J. , Haines R. G. 
Published: February 2011

Abstract
An infrared method based on the 5.88 μ absorption was developed for the analysis of ethylidenenorbornene in EPDM. The method was calibrated using a VPC analysis for unreacted monomer and by the addition of dichlorocarbene followed by an elemental analysis for chlorine. A check by NMR on a selected sample showed good agreement with the other methods.
Accessibility of the Carbon Black Particle Surface to Elastomers
Authors: Aboytes P. , Voet A. 
Published: February 2011

Abstract
Experimental carbon blacks were prepared with the generally encountered slit-shaped pores of discrete dimensions of 9,12.5, and 16 A˚ width in greatly differing size distribution. Equilibrium adsorption in the saturation range was determined in n-hexane for butadiene—styrene elastomers of the SBR type of average molecular weights of 1500; 2000; 15,000; and 300,000. In attempting to correlate the saturation adsorption values with carbon black surface areas, it was found that a simple linear relation in the range investigated could only be obtained by assuming that pores of 9 A˚ width were inaccessible to SBR of 1500 and 2000 MW; that pores of 9 and 12.5 A˚ width were inaccessible to SBR of 15,000 MW; and that all pores smaller than 20 A˚ width were inaccessible to SBR of 300,000 MW. The data indicated that there are no differences between high, regular and low structure blacks in saturation elastomer adsorption under conditions of equivalent dispersion. Equally, upon breaking the persistent carbon chain structure by dry ball milling in an inert atmosphere and equalizing the chemical surface properties by removal of surface oxides, no difference in elastomer adsorption from solution was observed. It must be concluded that commonly used high molecular elastomers do not have any access to smaller carbon black pores. Since access to the surface is a prerequisite for reinforcement, it is obvious that the surface in the pores of carbon black generally does not participate in reinforcing elastomers. The elastomer adsorbed per unit external black surface area appears to be independent of the carbon chain structure, indicating that the so called surface activity of the carbon black is independent of the chain length.
EPDM and Chlorobutyl Blends for Tire Sidewalls
Authors: Speranzini A. H. , Drost S. J. 
Published: February 2011

Abstract
Laboratory data have shown that the performance of tire sidewall components can be significantly improved by substituting EPDM and halogenated elastomers, either alone or in combination, for a portion of the highly unsaturated polymers now in use. Blends of EPDM and general purpose polymers provide improved weathering resistance, especially static ozone resistance. Blends of EPDM, chlorinated polymers and highly unsaturated elastomers offer a further improvement in weathering resistance and markedly better resistance to flex cracking. Chlorobutyl has been found to be more effective than polychloroprene in enhancing the dynamic properties of these blends. The level of performance achievable by these blends is a function of the chlorinated elastomer concentration. Current Los Angeles outdoor tire test results indicate that 25% RHC EPDM blends with general purpose elastomers perform adequately as sidewall components in the bias ply construction. The more severe dynamic sidewall flexing of the bias-belted and radial constructions, however, appears to require a higher level of sidewall performance. For these constructions, the tire test results indicate that select blends of EPDM, chlorinated butyl and highly unsaturated rubbers should provide satisfactory performance.
New Reactions for the Vulcanization of Natural Rubber
Authors: Baker C. S. L. , Barnard D. , Porter M. 
Published: February 2011

Abstract
One objective of a new crosslinking system for NR is a vulcanizate possessing good strength and fatigue properties and a high resistance to reversion; a second is a vulcanizate with reversibly thermolabile crosslinks. The reaction of amine-chloroboranes with NR was expected to give carbon-boron-carbon crosslinks possessing some measure of lability at high temperatures. In practice, the proportion of covalent crosslinks formed is very low and this is attributed to intramolecular additions and cyclizations. The majority of the effective crosslinks are stress-labile at ambient temperatures and the vulcanizates, therefore, have extremely high rates of creep and stress-relaxation. The nature of these crosslinks is still unknown. In all other aspects the physical properties of the vulcanizates are acceptable, reversion and aging resistance being particularly good. Surprisingly, the presence of the stress-labile crosslinks either in large preponderance or in various proportions with covalent crosslinks introduced by the compatible vulcanizing agents, dicumyl peroxide or TMTD-zinc oxide, did not impart the expected, very high tensile strengths. The amine-chloroborane vulcanizates are resistant to ozone cracking because of the rapid relaxation of surface strains. The second novel vulcanization system examined utilizes the attachment of hydroxyl or amino groups to the rubber chain by the thermal reaction of the appropriately substituted nitrosobenzene. Crosslinking is induced by means of difunctional isocyanates. This can be achieved in a one-step process, mixing and vulcanization being carried out under conventional conditions. A preferred variation, which overcomes the handling problems of free nitroso compounds, makes use of novel urethanes formed by the prereaction of p-nitrosophenol and diisocyanates. The efficiency of crosslinking and physical properties of the vulcanizates are much improved by the use of extra diisocyanate and by small additions of zinc dimethyldithiocarbamate which appears to act catalytically. Gum and black-filled vulcanizates have excellent reversion and aging resistance and, even before serious attempts at optimization, physical properties similar to those of a good sulfur vulcanizate.
The Influence of Residual Olefin Structure on EPDM Vulcanization
Authors: Baldwin F. P. , Borzel P. , Cohen C. A. , Makowski H. S. , Van de Castle J. F. 
Published: February 2011

Abstract
While the results of our study leave many questions regarding vulcanization still open, it is concluded that: 1. Effective, practical vulcanization of polymers containing simple monoolefinic residues by sulfur/accelerator, sulfur donor/accelerator, p-quinone dioxime (or dinitroso benzene), and halogenated alkyl-phenol/formaldehyde resins demands that there be present hydrogen on carbon alpha to the double bond (allylic hydrogen). 2. Peroxide curing is most efficient when the olefinic moiety presents a vinyl or vinylidene group. In the case of the latter, reactivity is enhanced when the doubly-substituted, double-bonded carbon atom is part of a strained ring system. while allylic hydrogen is not necessary, its presence is advantageous in these low unsaturation elastomers. 3. The presence of sulfur in a peroxide cure generally decreases vulcanization efficiency, the more so the more active the olefinic residue in the unmodified vulcanization reaction. However, when main chain scissioning is a highly significant part of the overall reaction, the presence of sulfur can actually enhance vulcanization efficiency. 4. Conventional sulfur/accelerator vulcanization is quite sensitive to the nature of the olefinic residue present. Vulcanization rate, efficiency, and crosslink distribution can be affected. Hence, no far-reaching generalizations can be drawn regarding “best” structures beyond that made in Conclusion 1 though internal olefins appear most active. 5. Effective, practical vulcanization with halogenated alkylphenol/formaldehyde resins in an initially uncatalyzed system demands not only allylic hydrogen but also a 1,1-disubstituted or 1,1,3-trisubstituted ethylene moiety.
Vulcanization of 1, 5-Polyenes with Sulfur as a Consecutive Reaction
Authors: Scheele Walter 
Published: February 2011

Abstract
The preceding treatise describes the vulcanization of 1,5-polyenes as a consecutive reaction based on kinetic investigations. Two ways of quantitative treatment of vulcanization processes are developed: one empirical and the other based on the kinetics of consecutive reactions. The results possibly give information about the sulfur content of the crosslinks, how to calculate their number, and, in certain circumstances, check the sulfur balance. The conditions are discussed which enable the kinetic results to be applied to such applications.
Mechanism of Rubber Coagent Peroxide Cure System
Authors: Cornell J. A. , Winters A. J. , Halterman L. 
Published: February 2011

Abstract
Peroxide vulcanization mechanisms of curing natural and synthetic rubbers have been extensively investigated. Little work has been reported on the use of polyfunctional monomers as coagents. Utilizing a model hydrocarbon, decane, with dicumyl peroxide and a methacrylate ester monomer, the mechanism for vulcanization in polyethylene is postulated. In the absence of the monomer, the dicumyl peroxide has been shown to abstract a hydrogen from the backbone —CH2— to form a radical. This radical terminates with another radical similarly formed to produce a crosslink. With n-decane, C20 dimers are formed. On the addition of a methacrylate ester, the hydrogen abstraction appears to still take place, but the methacrylate is added to the radical. This is not a typical polymerization initiation since the chain length of the methacrylate side chain is extremely short. Depending on the concentration, it may be limited to a single addition product. Using methyl methacrylate, infrared and nuclear magnetic resolution spectra confirm this addition product under experimental conditions. A similar product was also obtained when ethylene dimethacrylate was reacted, hydrolyzed, and re-esterified to the methyl ester. Comparative products using branched hydrocarbons indicated that tertiary hydrogens were also abstracted. Comparison of IR spectra obtained in a peroxide coagent vulcanization of polyethylene indicated the lack of polymethacrylate absorption. This curve is similar to that obtained with the decane, but quite different from that obtained with a mixed polymer of polyethylene and polymethyl methacrylate or polyethylene dimethacrylate.
Lithium Aluminum Hydride Analysis of Sulfur-Cured Vulcanizates
Authors: Studebaker M. L. 
Published: February 2011

Abstract
Since 1955 we have used lithium aluminum hydride for qualitative and quantitative analysis of the polysulfide content of various types of rubber vulcanizates. The first results were of qualitative or semiquantitative value, but by 1959 we felt that the method was revealing quantitative information. This work was presented at the International Meeting of the Division of Rubber Chemistry, A.C.S. and subsequently published. Since that time we have analyzed many thousands of rubber vulcanizates, and the method appears to provide useful data which are generally consistent with the results obtained with other probes. During this period several other laboratories have worked with lithium aluminum hydride with varying success. Other probes have been applied to the analysis of crosslink type. Among them are triphenylphosphine, sodium di-n-butyl phosphite, mercaptan-amine combinations, phenyllithium, and methyl iodide. The method of analysis with lithium aluminum hydride, including sample treatment prior to reduction and the titrations subsequent to reduction, has been investigated almost continuously in our laboratory since 1955. Some of the conclusions from this work are presented in this paper. We have also endeavored to study vulcanizates by combinations of probes which, taken together, tend to substantiate the simple stoichiometric relationships which are the basis of this method of analysis. Some examples will be presented. In reviewing the large mass of data which has been accumulated over a decade, it is impossible and undesirable to list all of the experimental results. Instead we will attempt to touch various topics in an overall survey. Actually, the majority of the results on method improvement are not suitable for this presentation, since virtually any factor which adversely affects the results gives nonreproducibility and scatter when plotting the measured quantities against the variables such as time, temperature, etc. Therefore, the results leading to an improvement in technique increase reproducibility; whereas undesirable practices have the opposite effect. This situation should be familiar to those who have studied oxidative phenomena, for instance.
Effect of Crosslink Structure on Properties of Natural Rubber
Authors: Lal Joginder 
Published: February 2011

Abstract
Natural rubber-sulfur-diphenylguanidine vulcanizates were allowed to react with triphenylphosphine under nitrogen to convert polysulfidic crosslinks principally to di- and monosulfidic crosslinks and to assess the effect of this change in the chemical nature of the crosslinks on tensile strength, flex life, and oxygen absorption characteristics. The vulcanizates were analyzed for organically combined sulfur and polysulfidic sulfur. Data obtained by this approach were treated statistically and showed that polysulfidic crosslinks are not essential for attaining high tensile strength or superior flex life. In another approach, polysulfidic crosslinks were introduced into dicumyl peroxide-cured vulcanizates containing carbon-carbon crosslinks to yield two-stage vulcanizates. Data for these vulcanizates fitted the curve of tensile strength as a function of 300% modulus for the precursor samples. It was further shown that the reduced failure envelope for natural rubber gum vulcanizates is independent of the type and relative concentration of chemical crosslinks. An interesting observation was made that the tensile strengths of dicumyl peroxide-cured samples were enhanced on extraction with acetone. Vulcanizates which had lost 95–99 per cent of their polysulfidic sulfur due to reaction with triphenylphosphine 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.
A New Approach to Rubber Reinforcement
Authors: Harwood J. A. C. , Payne A. R. , Smith J. F. 
Published: February 2011

Abstract
Hysteresis is an important factor in determining the strength of rubber vulcanizates, and the presence of small particle fillers in a rubber increases the hysteresis in at least two ways, (a) hydrodynamically and (b) viscoelastically. The two contributions are additive, the first remaining substantially constant with strain rate and temperature and the second increasing with decreasing temperature. The viscoelastic contribution is attributed to the region of immobile rubber chains close to the surface of the filler particles and has the effect of changing the viscoelastic response of the rubber network. It plausibly accounts for the observation that the strength behavior of a filler-loaded rubber at one temperature is similar to that of a gum rubber at a lower temperature. This change of viscoelastic behavior in the interphase between the polymer and the filler surface leads to a high level of creep even at low strains when filler or other solid particles are present. In the case of a strain-crystallizing rubber such as gum NR, only regions of high strain contain the necessary particulate inclusions. In this circumstance strength is obtained without serious creep in the bulk phase. Thus well-compounded natural rubber gum vulcanizates meet the requirements of a strong rubber with low creep and good resilience to a remarkable degree.