bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scanning Electron Microscopy of Rubber Tear
Authors: Bascom W. D. 
Published: February 2011

Abstract
A relatively simple technique has been described which allows observation of the deformation zone at tear tips in rubber specimens. Investigation of various rubbers revealed qualitative information about the type of yielding that occurs in the deformation zone under different conditions. The initial appearance of the tear tip in nitrile, polybutadiene (both with and without carbon filler), and natural rubber suggests a process of stretching followed by rupture and then relaxation onto the tear walls. Only in the case of a fluoro-elastomer was there evidence of cavitation, although microcavitation (of sizes ≪1 µm) may be occurring in the other rubbers at much higher magnification. On the other hand, aging in laboratory air had the dramatic effect of producing fibrous and nodular networks in the tear tip material of all the rubbers except the fluoroelastomer. In the first few hours, the network structure developed as cavities (Figure 9), but after 24 h the network was fully developed across the tear. The aging process is very likely an ozone attack not only on the rubber under stress at the tear tip, but also on the rubber on the tear wall. It is quite possible that there were residual stresses in the material on the wall which facilitated attack. Chain scission appeared to be allowing the rubber to relax by viscous flow under the action of surface forces. These results point up the need to distinguish between failure controlled by pure stress and failure assisted by oxidation/ozonolysis in studies of slow tear growth in rubbers. The SEM technique also provides information about fillers. Their elemental composition can be determined by XES, and some qualitative information can be gained about their adhesion to the matrix and their effect on tear tip yielding.
Kinetic Effects Associated with the Glass Transition of Polyisoprene
Authors: Prud'homme J. , Goursot P. , Laramée A. 
Published: February 2011

Abstract
In this study we have found that the glass transition temperature of polyisoprene as determined by DSC is not a linear function of the heating rate. An equivalent study of polystyrene suggests that this behavior is general for all amorphous polymers. When the heat history of the polymer is fixed by linear cooling, Tg measured as the inflection point of the DSC curve is a function of the type q=C exp (−E/RTg), where E varies slightly with the rate of cooling before the measurement. Analysis of the individual curves according to the method of Ellerstein shows that this behavior is compatible with a kinetic model of the glass transition which implies a simple relaxation process with an activation energy only slightly above the value of E determined from the dependence of Tg upon the heating rate.
Guayule Rubber: Vulcanization Properties of Gum and Filled Stocks
Authors: Winkler D. S. , Schostarez H. J. , Stephens H. L. 
Published: February 2011

Abstract
Guayule rubber has been used both in the resinous and deresinated form for more than sixty years during periods of either scarcity or high prices of hevea rubber. During this time little or no efforts have been made to standardize the individual processes to a point where the products had specifications similar to the “Technically Specified Rubbers”. This lack of specifications consequently left users of the guayule rubbers with various opinions of the capabilities of this type of natural rubber in their commercial products. It was generally believed that the rubber was only good for low-grade products or where guayule was only used as a tackifier for other rubbers. Recent interest in the utilization of arid regions and the increasing need for less dependence on foreign sources has led the Mexican government to develop a modern guayule product. It was the purpose of this study to evaluate Mexican guayule rubber in cooperation with CIQA in an effort to determine processing and vulcanization characteristics of the products prepared in their pilot plant in Saltillo, Mexico.
Rubber Elasticity in the Range of Small Uniaxial Tensions and Compressions. Results for Poly(Dimethylsiloxane)
Authors: Erman B. , Flory P. J. 
Published: February 2011

Abstract
Results of uniaxial tension and compression experiments are reported on crosslinked poly(dimethylsiloxane) networks in the unswollen state over the range 0.5&lt;α−1&lt;1.2 , where α is the extension ratio. Curves representing the reduced force [ƒ]=ƒ(V0/V)1/3(α−α−2)−1 plotted against α−1 can be approximated by straight lines for 0.5&lt;α−1&lt;0.9, in agreement with the phenomenological Mooney equation. As α−1 approaches 1, however, they tend to level off and continue into the α−1&gt;1 region with decreasing slope. These results are in agreement with the predictions of recent elasticity theories that incorporate the effect of junction-chain entanglements in the elastic free energy.
Rubber Heat Engines, Analyses and Theory
Authors: Farris R. J. 
Published: February 2011

Abstract
It has long been known that elastomeric solids could be used as the working “fluid” in engines designed to convert heat into mechanical work. In the past rubber heat engine cycles were not given serious consideration since energy alternatives were not in demand and the majority of the scientific community is unaware of their gas-like thermodynamic behavior. Consequently, past work has dealt with the subject primarily as a novelty or as a demonstrative proof of thermodynamic behavior. This paper provides an idealized mechanical and thermodynamic analysis of the rubber cycle and compares it to an equivalent cycle wherein a gas is the working fluid. Experimental data on a small rubber fiber engine are included which confirms the high power potential of these engines when they are designed using modern elastomeric fibers. These materials have remarkable properties and can respond rapidly to cyclic thermal disturbances. Power densities of roughly one watt/g of rubber have been attained using only a 30°C difference between the heat source and heat sink. Engine speeds well over 1000 rpm have also been attained when atmospheric pressure steam was used as the heat source. The analyses demonstrate that elastomers are ideally suited for energy conversion when only small temperature differences are available.
Influence of Carbon Black on Processability of Rubber Stocks. IV. Kinetics of Extrusion Shrinkage
Authors: Cotten G. R. 
Published: February 2011

Abstract
A careful examination of post-extrusion relaxation rates of SBR compounds containing various carbon blacks has shown that two distinct relaxation processes are taking place. The fast recovery region observed at times of less than 0.1 s after exit from the die is thought to be due to solid-like elastic recovery of the polymer imposed in the extensional flow region at the entrance to the die. The magnitude of that recovery increases with increasing surface area and decreasing structure of carbon black. The slow recovery region is observed at times longer than 1 s and caused by molecular orientation that occurs mainly during the extensional flow at the die entrance and maintained during the viscous flow through the die. Carbon black surface area and structure do not significantly affect the magnitude of the shrinkage in the slow recovery region. The observed two relaxation mechanisms may be simulated mathematically by two modified Maxwell elements in parallel, whose spring constants (and relaxation times) differ by a large factor.
13C NMR Analysis of Carbon-13 Enriched Ethylene Copolymers with Propylene
Authors: Brame E. G. , Holmquist H. E. 
Published: February 2011

Abstract
Carbon-13 nuclear magnetic resonance (13C NMR) has been used rather extensively in the characterization of ethylene-propylene copolymers and terpolymers. Chemical shift assignments on these copolymers were first made by Carman and revised only slightly by him recently. Despite all the work that has been done to assign the lines in the 13C NMR spectrum to the various sequence structures in ethylene-propylene copolymers, ambiguity still remains in some of the assignments, such as the assignment of the Sαβ line. It still is not known whether it is attributable entirely to two propylenes with one of them inverted, to an ethylene sandwiched between two propylenes with one of them inverted, or to an equal population distribution of these two structures. Carman and coworkers state that inversion of propylene in their copolymers is certain, but because of the large error in the calculation, the degree of inversion can be between 10 and 40% of the propylene content. His suggestion is that the Sαβ line is attributable to a combination of the two structure forms indicated above. Tanaka6 also makes this same suggestion in his 13C NMR work. He based his conclusion on some earlier infrared work. Most recently Randall describes a sequence length distribution method in which he estimates that the total amount of propylene inversions is the order of 20–30% for a concentration range of about 50–60 wt% propylene in copolymers with ethylene. Ray does not have to deal with the problem, as his 13C NMR spectra show no evidence of propylene inversions. His copolymers were prepared with an aluminum-titanium catalyst. Ours as well as Carman's were prepared with an aluminum-vanadium catalyst. Our reason for undertaking this program was to aid in the assignment of the Sαβ line. For this effort we prepared a series of ethylene-propylene copolymers that are carbon-13 enriched in both carbons of the ethylene, and we analyzed them by 13C NMR.
Elastomer Structures and ‘Cold Crystallization’
Authors: Bruzzone M. , Sorta E. 
Published: February 2011

Abstract
In a great number of applications an ideal elastomer should satisfy, to a certain extent, both of the following requirements: (1) nearly instantaneous crystallization upon application of strain (strain induced crystallization) and (2) slow or no crystallization when cooled at the temperature of maximum crystallization rate (cold induced crystallization). A noteworthy case of (2) is elastomer crystallization in a strained state. The connection between the points (1) and (2) has not been clearly understood up to now, but it is known that some crystallizable elastomers fulfil the requirements of both (1) and (2) better than others. From an experimental point of view, cold induced crystallization kinetics are substantially easier to measure than those of very fast strain induced crystallization. The phenomenon of cold induced crystallization in natural rubber, NR, has been known since the very beginning of elastomer technology and the tendency of natural rubber to crystallize by cooling has been overcome by crosslinking it with sulphur (vulcanization) without impairing its ability to crystallize by stretching (Goodyear, 1836). The synthesis of cis-polyisoprenes (IR) and cis-polybutadiene (BR) of different microstructural purity (different cis content) gave the possibility of changing the crystallization rate. It has also been reported that the very fast cold crystallization of trans-polypentenamer (TPA) could be reduced by lowering the trans content. The same fact had been observed earlier for trans-polychloroprene. There is a general agreement in postulating that the reduction of the crystallization rate, obtained either by cross-linking or by chain regularity reduction, can be linked with the lowering of the melting point. In both cases the low level of structural defects introduced in the chains does not affect the glass transition temperature in such a way as to vary the crystallization rate. The aim of this paper is to emphasize the importance of the variations of the glass transition temperature and melting point on the elastomeric cold crystallization rate and the way these may be used in planning new elastomer structures.
The Conversion Chemical Heterogeneity of Random Butadiene-Styrene Copolymers
Authors: Stejskal J. , Kratochvíl P. 
Published: February 2011

Abstract
The conversion chemical heterogeneity of random copolymers of butadiene and styrene with an average content 24 wt% of styrene is discussed quantitatively. With increasing weight conversion of copolymerization, the distribution of the chemical composition of the product becomes broader.
Effects of Sulfur on the Peroxide Cure of EPDM and Divinylbenzene Compounds
Authors: Fujio R. , Kitayama M. , Kataoka N. , Anzai S. 
Published: February 2011

Abstract
By introducing a small amount (0.15 part by weight) of sulfur into EPDM/DVB/DCPO compounds, Young's modulus and the rupture energy of the vulcanizates are markedly increased. The swelling equilibrium and dynamic mechanical behaviour show that an increase in crosslinking is achieved by the addition of sulfur. Moreover, electron microscopic study has revealed that vulcanizates from sulfur containing compounds have a better state of dispersion of the resinous poly-DVB phase than those without sulfur. When the amount of sulfur is too great (&gt;0.20 part), Young's modulus of the vulcanizate is markedly reduced, mainly because of insufficient polymerization of DVB. Sulfur apparently acts as a retarder of DVB polymerization. Furthermore, it is proposed that some reaction products of peroxide and sulfur could be the initiator of this polymerization.
Model Compound Vulcanization—Part I. Basic Studies
Authors: Lautenschlaeger F. K. 
Published: February 2011

Abstract
Rapid, yet reliable model compound vulcanization techniques have been developed in order to establish a link between MCV and vulcanizate properties. The main features of the new approach are the determination of the sulfidic product yield and a more extensive analysis of the isomer distribution. An increase in reaction time, a decrease in the sulfur level or an increase in the accelerator level lead to similar changes in the isomer distributions. Increasing zinc oxide levels lead to an increasing vulcanization efficiency. The isomer distribution is significantly affected by concentration changes. This has not been previously observed. A good correlation between MCV results and the analysis of sulfidic rubber networks in actual vulcanisates was observed.
Critical Reflections on Physical and Technological Test Methods in the Rubber Industry
Authors: Kainradl Primus 
Published: February 2011

Abstract
Surveying the development of test methods for vulcanizates since World War II and the currently used tests, we can distinguish three groups: (1) Tensile strength as well as tests for hardness and rebound, (2) Viscoelastic tests, (3) Endurance and aging tests. Along with the first group, during the war simplified tests appeared for flow and aging. Admittedly, tensile strength will continue to be employed in the future as the basic property for characterizing a vulcanizate and, still more, of a reinforcing system, even though vulcanizates of the equal tensile strength often differ in durability. For comprehensive description of vulcanizates, viscoelastic tests are advantageous and are finding ever wider use. Hardness and rebound resilience are related to viscoelastic properties and can serve as preliminary tests. Today there are numerous testing instruments, although these are mostly constructed and described by a single author. With respect to test conditions, they are very different. With increasing service requirements the necessity of endurance tests is becoming more and more recognized. These tests describe internal and external crack formation, with degradation from simultaneous heat generation. Aging from long usage, as shown by changes in properties, belongs in this group. All methods roust have a proven correlation with present product performance and, above all, be improved.
3-D Carbon Black Primary Structure Characterization via a New Electron Microscopy-Photogrammetry Technique
Authors: Mercer H. N. , Boyer A. H. , Deviney M. L. 
Published: February 2011

Abstract
In summary, we have presented a novel 3-D technique for image analysis of carbon black morphology. This technique involves measurements on a single aggregate while viewing this aggregate in three dimensions. The technique uses precision photogrammetry instrumentation and results in reasonable parameters characterizing carbon black. We believe this type of analysis to be useful on an individual laboratory or system basis, and not as an industry wide technique.
Analysis of Band Formation in Mill Operation
Authors: Tokita Noboru 
Published: February 2011

Abstract
A theoretical method has been developed to provide a rational means for preventing improper fast roll banding in drop mill operation. For a given material at a certain mill temperature, the material tends to go to the back roll with a very narrow nip distance. The material will go to the front roll at a certain nip distance as the nip is widened and will return to the back roll as the nip is again narrowed. This nip position is called the Front-Back Transition Point. A dimensionless number, the “Band Formation Index”, N0, is constant at the front-back transition point regardless of the type of mill and is a function of the friction ratio, nip distance at the transition point, and radius of the mill rolls. Applications of the N0 concept to a factory mill operation have been discussed, and practical means to avoid back roll banding and bagging have been described.
Rheology of Plastisols of Poly(Vinyl Chloride)
Authors: Collins E. A. , Hoffmann D. J. , Soni P. L. 
Published: February 2011

Abstract
The viscosity of PVC plastisols is seen to be affected by numerous variables. Increase in concentration of the resin causes the viscosity to rise, with the increase being more abrupt at the higher concentrations. Deviation from Newtonian behavior also increases with concentration. Decrease in the size of particles results in an increase in viscosity, the effect being more pronounced at low shear rates. Broadening the distribution of particle sizes results in a decrease in viscosity. Porous particles yield plastisols with higher viscosity as compared to nonporous compact particles. The type of plasticizer also affects the viscosity. A plasticizer which is a better solvent for PVC (low value of polymer-solvent interaction parameter, χ) results in a higher viscosity due to an increase in the amount of dissolved polymer. Additives such as alcohols and soaps affect the viscosity in an, as yet, unknown way. Fillers, heat stabilizers, and pigments also increase the viscosity. With increasing temperature, the viscosity first decreases, passes through a minimum and then increases until gelation. With further rise in temperature the viscosity again decreases and then levels out before degradation occurs. In future work, particular emphasis needs to be given to the understanding of the basic mechanism involved in the effect of additives on the flow behavior. Systematic experiments with a range of well-defined particle sizes and over a wide range of shear rates are also needed. A better understanding of the factors affecting the behavior of plastisols will go a long way in changing the art of plastisol formulation to a science.
Approximate Expressions for the Elastic Constants of Cord-Rubber Laminates
Authors: Walter J. D. , Patel H. P. 
Published: February 2011

Abstract
The relatively simple equations given herein for the four independent elastic constants of a single ply of cord and rubber and for the three independent elastic constants of a cord-rubber angle-ply laminate can be used to assess with sufficient accuracy for many purposes the effect of changes in constituent material properties and/or ply geometry on the stiffness characteristics of unidirectional, filamentary composites used in pneumatic tires.
Application of TMA for Rapid Evaluation of Low-Temperature Properties of Elastomer Vulcanizates
Authors: Brazier D. W. , Nickel G. H. 
Published: February 2011

Abstract
Static thermomechanical analysis has been investigated as a method for determining the low-temperature properties of vulcanizates. Dimensional changes of a sample in free expansion, indentation, or tension are monitored as the sample is heated at a known and reproducible rate. The first derivative of the dimensional change is simultaneously recorded. TMA/DTMA data obtained in free expansion gives the linear thermal expansion coefficient at any temperature during the experiment. The glass transition is observed as a change in slope as in dilatometric determinations. In the indentation mode, the thermogram is the result of competition between thermal expansion and indentation. For tension measurements, the thermogram records the additive sum of thermal expansion and tensional strain development. For indentation and tension, the glass transition is obtained by a standard extrapolation method. A maximum in the DTMA thermogram is also observed which represents the maximum rate of change as the sample is heated through the glass transition range. The temperature of this maximum, Tgd, is characteristic of a vulcanizate. Variation in scan rate between 2 and 20°C/min has little effect on Tgo and no effect on Tgd. At 50°C/min, thermal gradient effects predominate. For a wide range of vulcanizates in tension or indentation, Tgo or Tgd versus the Gehman rigidity modulus gives a linear relationship. Exact temperature agreement is not observed because of differences in the experimental techniques. In blends, several Tgd values are observed. Plasticizer effects can either be observed by a shift in the Tgo or by a change in the thermogram profile, the extent of indentation and temperature range over which it occurs. The extent of indentation correlates with vulcanizate hardness as expected. The indentation of a rubber sample by a flat probe has been treated mathematically in the literature, and the determination of Young's modulus by TMA/DTMA is now being investigated. In conclusion, the ease of sample preparation and the rapidity of TMA/DTMA measurements offers a quick approach to assessing the low-temperature properties of vulcanizates. At 20°C/min scan rate, runs can be completed in as little as four minutes (80°C total scan) if the sample has a single transition.
A Quantitative Study of the Carbon Black Reinforcement System for Tire Tread Compounds
Authors: Veith A. G. , Chirico V. E. 
Published: February 2011

Abstract
This comprehensive program clearly shows the influence of the four defined reinforcement system variables. The tread wear testing conducted over an extremely wide severity range illustrates how the influence of each variable or factor changes as the tire use of test severity is changed. The quantitative influence of the four variables is best illustrated by the index severity gradient, while the index range serves as a quick indicator. The influence of each factor of the reinforcement system increases as general test severity is increased. Carbon blacks with high structure and surface area are substantially superior to blacks with normal structure and surface area at the higher test severities. At the higher general severities, increased oil content produces higher wear rates. At any given severity level, the rate of wear passes through a minimum as carbon black level is increased. The carbon black content at this minimum wear rate shifts to higher values as general severity is raised. Test results at a series of specific cornering force levels (0.10–0.30 g range) indicate that the relative wear of typical tread compounds demonstrates crossovers of index values. Compounds that show superior wear resistance compared to a reference compound at high cornering severities often show inferior wear resistance at low cornering severities. Therefore, for maximum tread life or wear resistance, the reinforcement system with any tread rubber or rubber blend must be carefully adjusted to the anticipated level of tire use severity. The introduction of improved-technology carbon blacks with increased rubber-black interaction that is promoted by high DBP and EMA levels is a substantial advancement in rubber materials science and is most important for the production of high-performance long-treadlife tires.