bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Elasticity Models with Constraints on Chains and Junctions to Characterization of Randomly Crosslinked Networks
Authors: Queslel J. P. 
Published: February 2011

Abstract
Characterization of randomly crosslinked networks requires a topological description of imperfect network structure and a molecular-elasticity theory, preferably with a minimum number of adjustable parameters, relating macroscopic stress and strain or swelling ratios to molecular deformation. It is shown that simple relationships exist between the molecular weight between consecutive junctions, the molecular weight of linear precursor chains, the cycle rank, and the number of junctions for networks having no defects other than chain ends. The idealized affine deformation model (in which the constraints on junction fluctuations are infinite) and the idealized phantom-chain model (in which the constraints are absent) are inadequate for network characterization. The more realistic Flory-Erman constrained junction model is applied to the description of cis-polyisoprene cured with dicumyl peroxide. Swelling equilibrium experiments are in agreement with stress-strain measurements. Analysis of these stress-strain data with the constrained-junction and constrained-chain models gives similar results. This validates the Flory hypothesis that it is generally sufficient to concentrate the effects of the constraints on the junctions. Nevertheless, the constrained chain model proposed by Erman and Monnerie has the advantage of depending on one parameter, KG, instead of two, κ and ζ, for the constrained junction model.
Flexible Rubber-Steel Sandwich Springs
Authors: Muhr A. H. , Thomas A. G. 
Published: February 2011

Abstract
This novel form of spring has been developed to the point where the force-deflection behavior can be predicted with confidence from the known modulus of the rubber and the bending stiffness of the metal layers. Different geometries have been studied including three-point bend and cantilever configurations, with satisfactory agreement between theoretically predicted and experimentally measured stiffnesses. Dynamic behavior can be controlled by selection of the rubber compound. Depending on the geometry, the proportion of the deformation energy stored in the rubber itself, compared with the metal, can be varied, and this also influences, in a predictable manner, the overall damping characteristics of the spring. Epoxidized natural rubber, for instance, may be a candidate for the applications requiring higher damping. As the deflection of the spring is increased, a point is reached at which waves form in the metal layer that is under compression. This leads to a buckling of this layer and clearly limits the deformation which the spring can undergo. This important failure process has been studied experimentally and theoretically, and it is possible now to predict with some confidence the conditions under which it will occur. Fatigue failure under repeated stress has also been studied for a cantilever configuration. Lifetimes of over a million cycles were obtained with a range of samples, even when the deflection was close to that required to produce catastrophic buckling. However, for certain metal thicknesses, there is some indication that fatigue failure of the metal itself due to bending may become the dominant failure process. No failures either in the rubber or at the bond were observed.
Miscible Elastomer Mixtures
Authors: Roland C. M. , Trask C. A. 
Published: February 2011

Abstract
The degree of miscibility of the various IR/BR mixtures is not obvious from inspection of the chemical structures. IR and 1,2-BR, despite their distinct differences in chemical structure, form blends that are always homogenous. On the other hand, the liquid structural differences between IR and 1,4-BR overwhelm their chemical similarities, and it is the former that governs the phase behavior. As the 1,4 content of BR increases, the thermodynamic behavior of BR/IR blends ranges from nearly ideal mixing to the occurrence of an LCST due to negative excess mixing volumes. While the observation of lower critical solution temperatures in polymer mixtures in which no specific interactions exist is unusual, the same mismatch in liquid structure gives rise to the LCST commonly observed in polymer solutions. The interaction parameter for 1,2-BR in blends with IR is circa 2×10−4, which is remarkably low given the absence of specific chemical interactions. These mixtures most closely approximate ideal mixing behavior of any known pair of chemically distinct polymers. Even mixtures of BR isotopes are more nonathermal than blends of 1,2-BR with IR; moreover, the thermodynamic behavior of these isotope mixtures are not in conformance with simple Flory-Huggins lattice theory.
Heat Aging Performance of Ethylene Propylene Elastomers in Electrical Insulation Compounds
Authors: Spenadel L. 
Published: February 2011

Abstract
It is possible to develop an EPDM insulation compound with outstanding heat stability in the 160–180°C temperature range. Several key compounding ingredients are necessary in order to achieve the desired heat aging performance. They include the use of EPDM with high ethylene, low unsaturation, polychloroprene at the 5–10 phr level, zinc oxide at the 10–15 phr level, TMPT at the 2–4 phr level, hydrated alumina as the major mineral filler, reaction product of acetone and diphenylamine at 1 phr level, zinc salt of methylmercapto benzoimidazole at the 2–3 phr level, and dicumyl peroxide at the 5–6 phr level.
Compaction as a Part of the Mechanism in Incorporating Carbon Black into an Elastomer
Authors: Nakajima N. , Harrell E. R. 
Published: February 2011

Abstract
The first stage of mixing elastomer with carbon black is the incorporation, where the free carbon black becomes incorporated inside the elastomer matrix. During this process, elastomer and carbon black are compacted to become a solid mass. The compaction requires, first, deformation of elastomer domains to conform with the topology of the carbon black and next, relaxation of the elastomer in the deformed state. A model experiment has been conducted to characterize both deformation and relaxation behavior during the compaction. A preblended powdered rubber and carbon black were loaded into a Rheometrics Mechanical Spectrometer and compressed in the space confined by a molding ring and the parallel plates. The deformation was characterized as a change in the apparent volume with compressive force being held constant. From this result, a degree of compaction was evaluated as the extent of penetration by elastomer into the void volume of carbon black. The relaxation behavior was represented by the relaxation of compressive force. The temperature dependence of relaxation was well represented by the temperature-time shift of the elastomer component. The energy required for compaction estimated from the compression data was about 6% of the energy spent for the incorporation process.
Ammonium Salt Catalyzed Crosslinking Mechanism of Acrylic Rubbers
Authors: Giannetti E. , Mazzocchi R. , Fiore L. , Crespi E. 
Published: February 2011

Abstract
Crosslinking mechanisms of acrylic rubber containing both carboxylic and epoxy curing active sites were studied on low molecular weight polymers using different recipes. High cure rates were obtained with quaternary ammonium salts and/or triaryl nucleophiles of Group Va elements. A reaction mechanism based on carboxylate onium salt activity was suggested. Very high reaction rates were obtained with catalysts having low basicity and high steric hindrance, whereas polyamines like o-tolylbiguanidine were less effective. A very simple method for scorch time regulation was devised.
A One-Dimensional Numerical Model of Heat Transfer in the Process of Tire Vulcanization
Authors: Schlanger H. P. 
Published: February 2011

Abstract
A one-dimensional heat flow model based on the Crank-Nicolson system of nodes is described. Conventional cooling theory has been incorporated into the model which may then be entirely represented in matrix form as a generalized theory. A considerable amount of investigation of the tire shoulder region has shown that by simulation, one-dimensional heat transfer theory is applicable to the molding process of tire vulcanization. The problem is one in which a unique set of thermal constants may specify the basic process. In heating, these constants are the apparent thermal diffusivity and equivalent tire shoulder thickness and, in cooling, the so-called surface heat transfer coefficients are used to define the material. The tire curvature and groove geometries may be considered to perturb the linear model but are accounted for by adjustments of the equivalent tire thickness which is determined empirically. Generally, agreement between theory and experiment is very good, and hence, such a model paves the way for on-line computer control of the production press.
Studies on the Reaction between Thiocarbamylsulfenamides and Diebenzothiazyl Disulfide
Authors: Adhikari Basudam , Pal Dhananjay , Basu Dipak Kumar , Chaudhuri Ajit Kumar 
Published: February 2011

Abstract
The use of binary systems as accelerators in the vulcanization of rubber has received considerable attention, since many of them in suitable combinations, have been shown to provide efficient vulcanization systems. Dogadkin and co-workers and Skinner and Watson reported mutual activation with a number of popular accelerator combinations. It was suggested that the mutual activation occurs by the interaction of the accelerators to form intermediate complexes which decompose to produce free radicals responsible for initiating the various reactions involved in the vulcanization process. Recently Krymowski and Taylor studied the reaction between N-oxydiethylenethiocarbamyl-N′-oxydiethylenesulfenamide (OTOS) and N-oxydiethylene-2-benzothiazylsulfenamide (OBTS), a synergistic accelerator system, in tetrachloroethane at 142°C, and identified the various products formed. Many of these reaction products themselves are familiar as vulcanization accelerators and thus may contribute to the synergistic activity observed with the OTOS-OBTS system. In the present investigation, we have studied the reaction between thiocarbamylsulfenamides and dibenzothiazyl disulfide (MBTS) in the solid phase in order to get an insight into the mutual activity provided by this system in filled and gum vulcanizates of NR.
The Thermal Stability of Monosulfidic Crosslinks in Natural Rubber
Authors: McSwkeeney G. P. , Morrison N. J. 
Published: February 2011

Abstract
(1) Networks containing mainly monosuifidic crosslinks at methylene sites in the polyisoprene chains of natural rubber are expected to be more thermally stable than existing efficiently vulcanized networks. (2) Certain zinc-accelerator species promote the decomposition of crosslinks at high temperatures, but may be deactivated by complexation with zinc stearate (which is formed from stearic acid during vulcanization).
Effect of Accelerator Type on Brass-Rubber Adhesion
Authors: Hamed G. R. , Donatelli T. 
Published: February 2011

Abstract
A natural rubber compound accelerated with tetramethylthiuram disulfide (TMTD) was studied and compared to an N-oxydiethylene-2-benzothiazolesulfenamide (MBS) accelerated compound in order to determine the factors resulting in the poor adhesion to brass of the former. Adhesion to brass-plated steel cord was measured by using the TCAT pull-out test. Vulcanization time and temperature were varied. Also, both compounds were analyzed for crosslink density and type at different states of cure by selective cleavage of the crosslinks with thiol reagents. The poor adhesion to brass of the TMTD compound was not accounted for by cure rate or crosslink density or crosslink type. Synchronization of the rubber cure rate with the sulfidation rate of the brass surface appeared to be unimportant in determining the brass adhesion characteristics of that compound. This was investigated by testing the adhesion of the TMTD compound to brass plated steel cords of different reactivities. Cords were analyzed for copper sulfide formation by an energy dispersive x-ray (EDX) technique after pull-out and also after immersion in squalene solutions containing each accelerator with and without added free sulfur. This analysis showed that there is significant sulfidation of brass in the presence of TMTD accelerator. Atomic absorption analyses of the squalene solutions, after the cord immersions, showed relatively large amounts of copper and zinc present in the TMTD solutions as compared to the MBS solutions. This indicates that TMTD corrodes brass to a much greater extent than the MBS accelerator. From the data presented, the following conclusions can be drawn: (1) The poor adhesion to brass of TMTD accelerated compounds is not related to: (a) their rapid cure rates, (b) a lack of synchronization between cure rate and sulfidation rate, or (c) crosslink density or type. This implies that a deficiency of physical entanglements of rubber crosslinks within the copper sulfide layer is not a reason for the poor adhesion to brass of these compounds. (2) Considerable sulfidation of brass occurs in squalene solutions with TMTD indicating that lack of sulfur availability for brass sulfidation is not a valid explanation for the poor brass adhesion of TMTD compounds. Contrarily, in fact, the data suggest that excessive sulfidation of brass occurs in the presence of TMTD. (3) The corrosive nature of TMTD toward brass has been documented for cords dipped in TMTD/squalene solutions. This characteristic of TMTD likely results in a copper sulfide layer on the brass which is porous and mechanically weak. It is proposed that this direct interaction of TMTD with brass provides an explanation for the poor adhesion to brass of TMTD accelerated compounds. The mechanism by which the TMTD causes the very rapid removal of the brass into solution is not known at this time. Perhaps the TMTD or its decomposition fragments form relatively stable complexes with copper and zinc such that their removal is favored.
The Role of Filler Properties in the Creep Deformation of Filled Elastomers
Authors: Thiele J. L. , Cohen R. E. 
Published: February 2011

Abstract
The use of the creep T-jump experiment as a sensitive tool for elucidating the mechanistic behavior during the deformation of a complex material such as the carbon black filled elastomer has been illustrated. The activation energy for creep was determined as a function of stress for various vulcanizates. The effects of the choice of elastomer, and of variations in surface chemistry, structure, and loading of the filler, were studied. The T-jump results combined with electrical conductivity measurements confirmed the presence of a carbon black network which is considerably involved in the creep deformation process at low strain but not at high strain. In NR vulcanizates, there is a high-strain mechanism not observed in SBR vulcanizates; presumably strain-induced crystallization is responsible for the NR behavior. Oxidation of filler surfaces had essentially no effect on the creep deformation mechanisms, suggesting that, during creep, slippage of elastomers along the surface does not occur to any great extent for conventional or oxidized surfaces.
Oil Resistant Elastomers for Hose Applications
Authors: Dunn J. R. , Vara R. G. 
Published: February 2011

Abstract
Since there are so many types of hose based on oil resistant elastomers and so many specifications for each type, sometimes with conflicting requirements, it is not possible to generalize regarding current uses or future trends. NBR makes up the bulk of elastomer usage for hose tubes; CR has the highest usage in covers and is used in tubes also. NBR/PVC is used in both tubes and covers. High volume usage of these polymers is expected to continue where low cost and ease of handling are paramount. When higher heat resistance is required in covers, CSM and CM are used, and the trend towards use of these is expected to continue. XNBR/PVC blends may also be used in covers when excellent abrasion resistance is required. CSM and CM may be used in tubes requiring moderate oil resistance and good heat aging. For still better heat aging, the tendency is to use ethylene-methylacrylate or silicone. When low fuel permeability is required, ECO is used; it may also be used in the cover, since it is inherently ozone resistant. The ultimate in combined fuel, oil, and heat resistance is afforded by fluoroelastomers, the use of which is increasing, where hose service requirements are particularly severe, despite their higher cost.
Particle Size Measurement of Rubber Latices
Authors: Gorton A. D. T. , Pendle T. D. 
Published: February 2011

Abstract
It is obvious that there are a wide variety of experimental techniques available for the examination of the particle size in polymer latices. Some of these are well-established, such as the electron microscope, while others, such as chromato-graphic and photon correlation methods, are relatively new. Some systems are used for routine investigations of particle size distribution while others appear to be largely academic. Different methods yield diverse information with regard to the particles, and some are plainly unsuitable for latices with marked polydispersity. In order to summarize the various methods and the information they supply, Table I has been provided. This is an attempt to show, in a simplified manner, the chief features of the various techniques described above. It is hoped that this will be of value both to those established in this field and those beginning to lake an interest in the particle size of polymer latices.
Modification and Dielectric Properties of Polyisoprene
Authors: Honskus J. 
Published: February 2011

Abstract
The dielectric method can be used for determination of the polar groups modifying the nonpolar polymers. This method was used for the study of such complicated systems as the sulfur-accelerated vulcanizates. Results of the chemical analyses were compared with the results of dielectric measurements, and very good agreement was obtained.
Effect of Extending Oil on Viscoelastic Behavior of Elastomers
Authors: Nakajima N. , Harrell E. R. 
Published: February 2011

Abstract
For a number of years, oil-extended elastomers have been in commercial use. The obvious advantage is to dilute elastomers with less expensive oil. In addition, oil improves the processability of the elastomer. This enables the use of a higher-molecular-weight polymer, which, in turn, yields mechanical properties comparable or superior to those of a lower-molecular-weight polymer without oil extension. The viscoelastic properties of the oil-elastomer mixtures at a wide range of concentration and temperature offer information useful for understanding elastomer processability. The viscoelastic properties of such systems are also most sensitive manifestations of the polymer chain structure and, therefore, they represent fundamental characteristics of a given elastomer sample. In this work, two samples of ethylene-propylene copolymer differing in chain structure were selected. The oil-elastomer mixtures were prepared for polymer concentration in the range of 2.5–100%. The viscoelastic properties have been measured in the temperature range of 30–150°C. The frequency range was 10−1–102 rad/s and in some cases −2–102 rad/ s. The superposition principles have been examined with these data for both the temperature and concentration dependence.
Fatiguing of Rubber-Rubber Interfaces
Authors: Fielding-Russell G. S. , Rongone R. L. 
Published: February 2011

Abstract
Mechanical fatigue results of three rubber systems, obtained by using a Painter adhesion testpiece, modified in such a way that it mates rubber-rubber surfaces (rather than metal-rubber surfaces) indicated that the testpiece is capable of fatiguing a rubber-rubber interface and therefore is useful for evaluating rubber-rubber joints. The mode of failure, correlation of the present results with static interfacial results, and the wide range of crack growth constants all indicated interfacial fatiguing. Test results, i.e., time to failure versus applied dynamic load, gave good agreement with established rubber fracture theory.
Strength of Neoprene Compounds and the Effect of Salt Solutions
Authors: Bhowmick A. K. , Gent A. N. 
Published: February 2011

Abstract
Soft CR vulcanizates resemble NR vulcanizates in many ways. Their tensile strength is high at low temperatures and drops sharply at a characteristic temperature to a value of about 1–1.5 MPa. Their tear resistance decreases smoothly as the temperature is raised and does not reach a lower limit, even at temperatures as high as 150°C. However, they show continuous tear propagation at room temperature under relatively large tear forces, whereas NR materials do not. This difference must reflect different strengths of the crystallites formed at the tear tip, those in CR being significantly weaker. Also, a specific environmental effect is noted: When immersed in solutions of FeCl3, the CR materials show more rapid tearing, and they tear at significantly lower forces than in water or in NaCl solutions (or in air). Although they swell continuously in water and in salt solutions, the rate of swelling seems far too low to account for the weakening observed. Moreover, the swelling is greater in water, whereas the weakening is specific to FeCl3 solution. It is attributed to a chemical reaction between FeCl3 and the CR molecule.
Improvements in the Oxidized Gasoline Resistance of NBR Elastomers
Authors: Killgoar Paul C. , Lemieux Marvin A. 
Published: February 2011

Abstract
Nitrile compounds have been developed which have excellent sour gasoline resistance. The compounds are cured with a mixed urethane/sulfur (80/20) crosslinking system. After 6 weeks aging in sour gasoline, the physical properties of the urethane cured nitriles were still superior to the best sulfur-cured nitrile and epichlorohydrin compounds which had been tested for 3 weeks. Heat resistance of the urethane-cured compounds is not as good as the sulfur-cured compounds; however, it is anticipated that the new compounds can meet the current temperature requirements for the fuel hose tube.
Fracture Mechanics Applied to Elastomeric Composites
Authors: Gent A. N. 
Published: February 2011

Abstract
Griffith introduced a general fracture criterion in 1920: a crack will grow only when enough energy is available in the system to cause further fracture. This simple concept has been applied by Rivlin and Thomas to various tear processes in elastomeric materials and by Kendall to a variety of adhesive failures. Their results are reviewed, with particular reference to the fracture and debonding of elastomeric composites. Two further cases are then considered: the detachment of an elastic matrix from a rigid spherical inclusion and the pullout of inextensible cords from an elastic block in which they are embedded.