bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tear Strength of Elastomers under Threshold Conditions
Authors: Bhowmick A. K. , Gent A. N. , Pulford C. T. R. 
Published: February 2011

Abstract
Measurements have been made of the tear strength of several elastomeric materials under threshold conditions, e.g., in the swollen state and at high temperatures when dissipative contributions to the work of fracture are minimized. The materials studied were Neoprene WRT, BR, SBR, EPDM, and a castable polysulfide material, LP-32. They were crosslinked to different degrees, using a free-radical source, or sulfur, or a metal oxide as the crosslinking reagent. Values obtained for the threshold tear strength were similar in all cases, lying in the range 50–200 J/m2. They appeared to be approximately proportional to E−1/2, where E is the tensile (Young's) modulus of the elastomer, as predicted by the theoretical treatment of Lake and Thomas. Values for networks with polysulfidic crosslinks were significantly higher than with monosulfide or C—C crosslinks, by about a factor of 2. Values for carbon black-filled materials were higher also, by about the same factor, in comparison with the equivalent unfilled materials. These effects are attributed to rupture of labile crosslinks, or bonds to carbon black, prior to main-chain rupture.
Resistivity and Surface Roughness Analyses for Evaluating Carbon Black Dispersion in Rubber
Authors: Cembrola R. J. 
Published: February 2011

Abstract
A comparison of the three techniques shows that while all can discriminate dispersions, their useful ranges are different. The electrical resistivity method is relatively insensitive at the early stages of mixing but has a high sensitivity at the intermediate and latter stages. This method is directly influenced by the dispersed black. There are limitations, however, to its utilization. The method works only within a narrow range of volume loadings (35–75 phr) and can only be used for small and intermediate particle size carbon blacks. One advantage that the resistivity technique has is that uncured rubber is tested. Elimination of the vulcanization step makes the resistivity technique an attractive quality control test. The Phillips rating and surface roughness are not limited by the volume loading of filler or the nature of the filler. Each technique works quite well at intermediate dispersions and only loses sensitivity at very good dispersions. These methods differ from the resistivity in that they are sensitive to the undispersed filler. The surface analysis is a more objective and quantitative technique than the Phillips rating. The surface analysis technique can have a microcomputer interfaced to store data and calculate results. This reduces the test time to a matter of minutes. The Phillips dispersion rating is made on vulcanized rubber so that there is added sample preparation which leads to a longer analysis time. The surface analysis has been reported for both vulcanized and unvulcanized rubber; however, the unvulcanized samples present special problems in cutting and do not show as strong a correlation with other dispersion ratings.
Stress Relaxation Measurement as a High-Speed Method for Predicting the Long-Term Behavior of Vulcanized Rubber
Authors: Clamroth R. , Ruetz L. 
Published: February 2011

Abstract
Intermittent stress relaxation is well suited for quantifying aging processes in rubber. For NR, the effects of different antioxidants can be measured by the rates at which the modulus falls. In synthetic rubbers (SBR, NBR, and CR), it can be measured through the modulus increases caused by oxygen crosslinking. Equal-value times, e.g., t0.75 for NR and t1.25 for SBR, NBR, and CR, are the times taken by the modulus to decrease or increase to a given percentage of its original level. They are better measures of aging than the modulus change after a given time. For NR, it has been shown that stress relaxation measurements at elevated temperatures and in pure oxygen correlate with the results of conventional aging methods. Thus the testing times can be drastically reduced—from up to 28 days to 1–8 hours. Discontinuous stress relaxation measurements are considerably more accurate and selective than conventional oxygen aging. For the repeatability of a single equal-value time measurement, we obtained a coefficient of variation (s/x) of 5–10% for stress relaxation measurement and about ±20% for oxygen aging. The degree of selectivity for oxygen aging and stress relaxation was found to be 3.6 and 18, respectively. The correlation between the results of stress relaxation measurements and those of the conventional oxygen and hot air aging tests was investigated for a large number of NR compounds and for some SBR, NBR, and CR compounds. The correlation is not very good, but it must be remembered that the equal-value times determined according to the two methods show relatively pronounced variability. With the conventional aging methods, the results also depend on what quantity is measured, e.g., the change in tensile strength or hardness, and on what equal-value time is chosen, e.g., the time taken by the property concerned to decrease to 90 or 75% of its original value. The conclusion of the investigations described above is that intermittent modulus measurement is an interesting high-speed method for the assessment of aging behavior. It will acquire a firm position in the arsenal of rubber testing methods, but will probably supplement, and not completely replace, the aging methods currently used.
Prediction of Hysteresis Properties from Reticulation Studies of Carbon Black Suspensions in Mineral Oil
Authors: Sircar A. K. , Wells J. L. 
Published: February 2011

Abstract
1. A linear log-log relationship was observed both for specific conductivity-time and viscosity-shear rate of carbon black suspensions in liquid vehicles. The slope, n, is related to the rate of recombination of carbon black aggregates, while the intercept (ρ0) is a measure of specific conductivity of carbon blacks after one minute recombination. 2. The reformation rate index, n, varies inversely with the surface area of the blacks. 3. The hysteresis relationship for suspensions (ρ0×1/n), correlates with hysteresis properties in a solid rubber. 4. Thus, hysteresis properties of black loaded elastomers can be predicted from reticulation studies of carbon black suspensions in liquid vehicles.
Innovation in Flame and Heat Resistant EPDM Formulations
Authors: Kato H. , Adachi H. , Fujita H. 
Published: February 2011

Abstract
A series of experiments on the flammability of EPDM formulations which contained a minimum amount (30 phr) of aromatic organic flame retardant (DBDO) revealed that increasing the crosslink density increased the flame resistance. This was especially true when the formulations were cured by a combination of DCP, TAIC, and HVA-2. The best result was obtained in a formulation which was cured by DCP/TAIC/HVA-2 at 2.5/1.0/0.5 phr, respectively. This material had excellent physical properties that would be well suited for use in the wire and cable industry. It was also found that good dispersion of individual ingredients was needed to obtain optimum flame resistance.
Theory of the Elastic Net Applied to Cord-Rubber Composites
Authors: Clark Samuel K. 
Published: February 2011

Abstract
There has been considerable interest over the last twenty years in the subject of the elastic properties of cord-rubber composites. This has been due to the rather intensive study of composite material characteristics, brought about by the increased use of rigid composites in many structural applications. In addition, work on the prediction of cord rubber composite properties has also continued because of the active development of finite element programs for analysis of pneumatic tire properties. These finite element programs require a thorough knowledge of cord-rubber composite elastic characteristics, which in turn are found to be considerably more difficult to calculate than had been originally thought. The present paper introduces a simplified theory for the prediction of such properties with sufficient accuracy for engineering uses.
The Effects of Carbon Black and Other Compounding Variables on Tire Rolling Resistance and Traction
Authors: Hess W. M. , Klamp W. K. 
Published: February 2011

Abstract
The rolling resistance of SBR/BR radial passenger tire treads was varied as a function of carbon black type and loading, as well as other compounding variables, such as oil content, high-viscosity oil and resin addition, and NR substitution. In all instances, the rolling loss variations showed a good correlation with either tan δ or resilience. The tan δ response was valid for a wide range of test temperatures, frequencies, and strain amplitudes. Wet (32 km/h) and dry (64 km/h) traction indicated a high positive correlation with loss compliance (D″). Here, the best correlations were obtained at lower dynamic testing temperatures (0–25°C.) and higher strain amplitudes. High-speed wet traction (97 km/h) appeared to be relatively independent of the tread compounding variables but did show a slight correlation with tan δ measured at ™25°C. The following patterns were observed relative to tread rolling resistance, traction, and wear as a function of compounding variables: 1. Black loading.—Reduced black loading lowers rolling resistance without much effect on traction. About 4% less black in the tread compound lowers rolling resistance by about 5–6% in the formulations which were evaluated. 2. Oil loading.—At a fixed black level, increased oil raises both rolling resistance and traction. About 2% higher rolling resistance was found for a 10 phr increase in oil loading, but the effect on wet traction appeared to be much greater (7–8%). 3. Black type.—Increasing black fineness raises both rolling resistance and traction, the latter effect being considerably less. Increased DBPA has very little effect on rolling resistance but reduces traction. At reduced black loadings, the finer and higher DBPA blacks show the least loss in treadwear resistance. Blacks with broad aggregate size distribution give lower rolling resistance at the same surface area and DBPA. For extreme blends (carcass and tread grades), however, the loss in treadwear resistance is quite severe (∼30%). 4. Curatives.—Increased sulfur and accelerator levels produced a significant reduction in tan δ, with a similar but lesser drop in D″. The same reduction in tan δ with increased accelerator (OBTS) level produced less effect on D″ than the sulfur increase. 5. Natural rubber substitution.—Compounds in which 30 phr of NR were substituted for 25 phr of SBR and 5 phr of BR indicated slightly better performance in terms of both rolling resistance and traction. 6. High-viscosity oil or resin substitution.—Replacing conventional extender oil with high-viscosity oil or resin appears to improve traction but has a greater adverse effect on rolling resistance. 7. Compound optimization.—N299 black gives the best overall balance of performance in terms of rolling resistance, traction, and treadwear at reduced black loadings. N121 confers about 10% better treadwear and equal traction in the same compound, but at about 4% higher rolling resistance.
The Use of a Screening Test for Assessing the Hydrogen Sulfide Resistance of Elastomers
Authors: Pfisterer H. A. , Dunn J. R. , Vukov R. 
Published: February 2011

Abstract
A screening test has been devised which in 24 h exposure at 200°C to a gas mixture containing 32.7 ± 0.7% hydrogen sulfide at 1.725 pressure can distinguish the hydrogen sulfide resistance of a variety of vulcanizates. As expected, fluoroelastomer vulcanizates exhibited the best retention of properties, but carboxylated NBR was also surprisingly stable, especially in modulus retention. The most important variable in regular NBR vulcanizates was the acrylonitrile content. Stability in presence of hydrogen sulfide increased with decreasing acrylonitrile level. The effect of acrylonitrile level has been rationalized by the observation that hydrogen sulfide reacts with nitrile groups to form thioamide, which subsequently enters into crosslinking reactions. The reaction of hydrogen sulfide with double bonds does not result in crosslinking.
Present Status and Future Trends of Specialty Polymers for Automotive Hose in Japan
Authors: Inagami Masaaki , Saito Yoshiomi , Hashimoto Kinro 
Published: February 2011

Abstract
In Japan, official specifications covering automotive devices do not specify the polymer(s) to be used. Accordingly, we have reviewed the market trend of polymer usage for various hoses in these devices, and through a review of published papers, indicated polymer usage reported or suggested in them. As the development of automotive parts requiring higher endurance and reliability has been greatly emphasized in Japan, we, a specialty polymer supplier, have expended our best efforts to comply with such requirements.
Calculation of the Temperature and Extent of Reaction during the Vulcanization of Powdered Rubber
Authors: Accetta A. , Vergnaud J. M. 
Published: February 2011

Abstract
Although vulcanization is a complex series of reactions, the overall result for heat of reaction could be described by an Arrhenius equation and a single activation energy. The activation energy for the vulcanization of powdered rubber recovered from tires was about 106 kJ/mole and the rate of reaction was described by a first-order reaction. With the kinetic parameters determined for the curing reaction by DC, the temperature profiles in rubber sheets were calculated. A numerical method of Dusinberre's generalization was an explicit incremental method applied to one-dimensional conduction and took into account the internal generation of heat due to the cure reaction and the heat transfer through the mold-rubber interface. The last problem was resolved by considering the fact that there was the same heat transfer rate on each part of the interface. This method proved to be as accurate as the implicit Grank Nicholson method, and its great advantage over the latter was that this explicit method needed only a small and inexpensive computer. Experiments pointed out the effect of several parameters on temperature profiles and midplane temperature for rubber sheets. Thus, the sheet thickness, mold temperature, initial rubber temperature, and a single two-step programming of mold temperature were considered. Some importance was given to possible applications. The determination of the time necessary for the midplane temperature to reach particular values such as the mold temperature or its maximum value. It is worth mentioning that our method allowed us to correlate the extent of reaction with the time and, therefore, to predict the time necessary for the extent of the reaction to reach a suitable value with a specified quality of vulcanizate for given operating conditions.
Studies of Vulcanization of Reclaimed Rubber
Authors: Phadke A. A. , Bhattacharya A. K. , Chakraborty S. K. , De S. K. 
Published: February 2011

Abstract
Rubber vulcanizates can be reclaimed by milling them with curing ingredients. Physical properties of the RR vulcanizates are inferior to those of the control vulcanizate. RR compounds exhibit poor processing characteristics. Poor physical properties and processing characteristics can be improved by blending with fresh rubber. However, a higher proportion of RR increases the stiffness and causes brittle failure.
Bulk Polymerization Kinetics by the Adiabatic Reactor Method
Authors: Camargo R. E. , Gonzalez V. M. , Macosko C. W. , Tirrell M. 
Published: February 2011

Abstract
We have shown that the adiabatic reactor method (A.R.M.) is useful to measure bulk polymerization kinetics. The choice of an adequate model is fundamental to represent the kinetics and for use in modeling and processing applications. The definitions of differential and integral errors have been introduced. It has been shown that these definitions lead to different objective functions and minimization problems. With an adequate model, we must be able to find a single set of parameters to minimize both errors simultaneously. We have shown that the n-th order and autocatalytic models are particular cases of a generalized phenomenological model. We continue to study this technique and to develop new forms of estimation. Dynamic models for complex situations which may include heat losses and intermediate species are now under development, and we expect to present them in a forthcoming publication.
Short Silk Fiber Reinforced Natural Rubber Composites
Authors: Setua D. K. , De S. K. 
Published: February 2011

Abstract
(1) The resorcinol-hexa-silica bonding system is essential for NR-silk fiber systems. (2) Mechanical anisotropy is observable only at higher fiber loadings (20 phr and above) in NR-silk fiber systems. (3) In composites containing a sufficient amount of bonding agents and fibers for tensile anisotropy to be observed, tensile failure occurs by both fiber breakage and debonding. (4) Addition of silk fiber to NR causes (a) increase in hardness, (b) reduction in resilience and elongation at break, (c) increase in heat buildup and set, and (d) increase in tear resistance. (5) The aging resistance of silk fiber-reinforced NR composites is excellent only beyond a fiber loading of 20 phr. (6) Mill shrinkage and green strength of NR improve, while Mooney viscosity and scorch time increase with the addition of silk fiber to NR.
Study of Cure Synergism of the Thiocarbamylsulfenamide-Dibenzothiazyl Disulfide Accelerator System in the Vulcanization of Natural Rubber
Authors: Pal D. , Adhikari B. , Basu D. K. , Chaudhuri A. K. 
Published: February 2011

Abstract
N-cyclopentamethylenethiocarbamyl-N′-cyclopentamethylenesulfenamide (CPTCS) and dibenzothiazyldisulfide (MBTS), as binary accelerators in a mixture have been found to provide significant mutual enhanced activity with regard to modulus, tensile strength, hardness, and elongation at break in the vulcanization of NR gum stocks. The synergistic activity of the CPTCS-MBTS system is very much dependent upon the accelerator ratios, concentration of sulfur and accelerator, as well as the temperature of vulcanization. Investigations carried out with the Monsanto rheometer also corroborate the above results. It is suggested that the synergism arises out of the interaction between CPTCS and MBTS which produces intermediate accelerators. N,N-Diethylthiocarbamyl-N′-cyclohexylsulfenamide (DETCS) in conjunction with MBTS, produces similar results in the vulcanization of NR. Structural characterization of the vulcanizates obtained at 140 and 160°C reveals that predominantly monosulfidic linkages are obtained with CPTCS or DETCS and MBTS combinations. The intermediate combinations, at near equimolar concentration of the two accelerators, exhibit maximum crosslink density. An attempt has been made to correlate physical properties with crosslink density as well as various types of crosslinks.
Strain-Time Correspondence: Critical Examination of the Principle and Its Application to Classification of Gum Elastomers
Authors: Nakajima N. , Harrell E. R. 
Published: February 2011

Abstract
The first step in elastomer processing is compounding, where the behavior of gum elastomer has a decisive influence. For this reason, characterization of processability of gum elastomers in the compounding step is very important. The elastomer behavior in compounding may be described as large deformation and fracture. These behaviors have been subjects of our fundamental studies. This paper is concerned with the deformation aspect of the processability, but not the fracture. The focal point of the study is how to describe a large deformation in a concise, systematic manner. The discovery and subsequent adoptation of the “strain-time correspondence principle” enables us to achieve this objective, namely, the viscoelastic data obtained with different instruments, employing different modes of deformation, were shown to be transformed to a master curve encompassing wide ranges of time scale. The implication of the achievement, although not fully proven, is two-fold; first, if one type of deformational behavior is observed over a sufficiently wide range of time scale, any other type of deformational behavior may in principle be calculated. Second, the master curve may be used as an indirect expression for processability of a given elastomer, although the master curve itself does not describe the deformations in the processing. In demonstrating the strain-time correspondence, various examples of master curves were shown. In these, the experimental data had rather large errors, although the scattering was random. The primary reason for the scattering of the data lies in the use of high-speed tensile stress-strain measurements, in which the experimental errors were rather large. For this reason, a more accurate demonstration of the strain-time correspondence principle is attempted in this work. A cone-and-plate assembly was used in rotational, oscillatory, and relaxation modes of testing with both small and large deformations.
Rubber-Thermoplastic Compositions. Part VIII. Nitrile Rubber Polyolefin Blends with Technological Compatibilization
Authors: Coran A. Y. , Patel R. 
Published: February 2011

Abstract
The results of this work suggest a practical route to hot-oil-resistant thermoplastic elastomers based on NBR and a polyolefin resin (such as polypropylene). Although these two types of polymer are normally grossly incompatible with each other, a melt-mixed blend thereof is technologically improved by the presence of a small amount of a compatibilizing block copolymer which contains both polar and nonpolar segments. Ideally, the block copolymer should contain molecular segments of the types of polymers to be compatibilized. The compatibilizing block (graft) copolymer can form in situ during melt-mixing. Dynamic vulcanization (during melt-mixing) of a compatibilized NBR-polypropylene blend produces a thermoplastic elastomer with mechanical properties about as good as those of a corresponding composition of EPDM and polypropylene (two polymers which are nearly mutually compatible in a thermodynamic sense). The compatibilizing NBR-polypropylene graft copolymer might act by reducing (molten-state) interfacial tension at the NBR-polypropylene interface and also by increasing the interfacial adhesion in the “solidified-state” composition during its use. The hot-oil resistance of the compatibilized NBR-polypropylene thermoplastic vulcanizates is excellent. Also, the NBR-polypropylene compositions can be blended with thermoplastic vulcanizates based on EPDM and polypropylene to obtain thermoplastic elastomeric compositions which exhibit both good hot oil resistance and low temperature brittleness characteristics.
Reactivity Optimization of Prevulcanization Inhibitors
Authors: Sullivan A. B. , Davis L. H. , Maender O. W. 
Published: February 2011

Abstract
A series of phthalimide-based prevulcanization inhibitors has been used to probe the relationship between MBT reactivity and inhibitor performance efficiency in NR accelerated with TBBS. Based on these results, there appears to be a reactivity window for best performance. For the phthalimide series, it occurs with secondary alkyl mercaptans. Inhibitors with MBT reactivity below the optimum are less effective because they do not compete with the accelerator for the autocatalyst. The activity also falls off at higher reactivities. There are two explanations for this behavior. First, as proposed by others, the very reactive inhibitors may not completely survive mixing and precuring, so that some of the inhibitor is lost to unproductive side reactions. Over and above this effect, the performance declines because the MBT is trapped less securely when the BtSSR is derived from a more reactive mercaptan. Although other leaving groups were not evaluated in this work, it is clear that reactivity optimization can be achieved with any leaving group, L, by proper selection of -SR. For example, in the work of Morita and Sullivan with thioketal type prevulcanization inhibitors, it was demonstrated that primary alkyl and aromatic mercaptans were required to achieve optimum inhibitor activity.