bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoelastic Characterization of Long Branching and Gel in Elastomers by Comparison of Large and Small Deformational Behavior
Authors: Nakajima N. , Scobbo J. J. , Harrell E. R. 
Published: February 2011

Abstract
Ten different raw elastomers of varied chemical structure and Mooney viscosity were characterized with both tensile stress-strain behavior and dynamic shear behavior. The room temperature tensile stress-strain behavior was determined at strain rates of 0.239, 0.0892, and 0.00653 sec−1. These stress-strain data were reduced with a use of strain-time correspondence principle. The dynamic-shear behavior was observed over the frequency range from 10−2 to 102 rad/s. Double logarithmic Cole-Cole plots were used to characterize a relative degree of long branching and gel content. The reduced data of tensile stress-strain measurements were compared to the data of dynamic measurements. From this comparison, the sample containing a long-range crosslinked network was differentiated from that containing microgel.
Cure Modification Effected by 2-Iminothiophthalimides in the Vulcanization of NR Accelerated by Thiocarbamyl Sulfenamides and Dibenzothiazyl Disulfide
Authors: Das Prasanta Kumar , Datta Rabindra Nath , Basu Dipak Kumar 
Published: February 2011

Abstract
Studies have been made on the effect of N-oxydiethylene thiophthalimide (ODTP) and N-cyclopentamethylene thiophthalimide (CPTP) as retarders in the vulcanization of NR. N-oxydiethylenethiocarbmyl-N′-cyclopentamethylene sulfenamide (OTCS) and N-oxydiethylene thiocarbamyl-N′-oxydiethylene sulfenamide (OTOS) have been used separately with MBTS to form the binary systems of accelerators. Retardation exhibited by the combinations OTCS-MBTS-ODTP and OTOS-MBTS-CPTP is noteworthy. In these systems, both CBDS and OBDS are formed. The enhanced activity with regard to torque, scorch, modulus, tensile strength, etc. is believed to be due to the presence of CBDS and OBDS. Probable reactions for the formation of various compounds responsible for acceleration and retardation of vulcanization of NR have been explored. It has been observed that ODTP and CPTP provide better cure-retardation than CTP and in almost all the cases, the cure rate and torque values of the resulting vulcanizates are increased. In the case of filled vulcanizates containing HAF, it seems that the nature of the reaction is of the same kind as observed in the case of gum stocks but differs only in degree. The physical data of the vulcanizates containing HAF also indicate that both ODTP and CPTP excel CTP in many respects.
A Large-Deformation Finite-Element Analysis for Multilayer Elastomeric Bearings
Authors: Seki Wataru , Fukahori Yoshihide , Iseda Yutaka , Matsunaga Tsutomu 
Published: February 2011

Abstract
Finite element methods are applied for multilayer elastomeric bearings under large deformation. The method is capable of handling nonlinear elasticity and incompressibility of rubber-like materials. The strain energy density function which determines elastic properties of the materials is obtained empirically through strip biaxial testing. The computation using the strain energy density function is conducted to analyze the stress and strain distribution and the performance characteristics of multilayer elastomeric bearings, which is in good agreement with the results of actual experiments.
GPC Analysis of Rubber in Guayule and Five Species of Parthenium (Asteraceae)
Authors: West Jan , Rodriguez Eloy 
Published: February 2011

Abstract
The genus Parthenium includes one species, guayule (P. argentatum Gray), that produces large amounts of good quality rubber. At present, guayule is the subject of research to determine if it can be developed as an alternative crop for the arid areas of the United States and other countries. Interspecific hybridization between guayule and other species of Parthenium can be accomplished without major difficulties, and there are several desirable agronomic traits that can be transferred from these species to guayule. These other species have not been reported to have large amounts of rubber. Rollins reported that some biotypes of Parthenium incanum H.B.K. contain small amounts of rubber. Taylor and Benedict reported that P. tomentosum D.C. var. stramonium (Greene) Rollins contained 0.02% rubber. Angulo-Sanchez examined 21 guayule plants from native stands near Saltillo and found Mw values varied between 6.10×104, 6.10×105, and 1.13×106; Mn values varies between 6.10×104 and 6.10×105 (Reference 7). These values are comparable to Hevea clones examined by Subramanian. In this study, the molecular weights of guayule and five species of Parthenium are reported, the F1 hybrids between guayule and one of these species, P. alpinum was also examined to determine the size of polymers that characterize this particular hybrid.
Effect of Carbon Black on the J-Integral and Strain Energy in the Crack Tip Region in a Vulcanized Natural Rubber
Authors: Liu H. , Lee R. F. , Donovan J. A. 
Published: February 2011

Abstract
1) The J-integral is path independent in both PS and SEN specimens and equals the tearing energy. 2) The critical J-integral at initiation is less in PS specimens than in SEN specimens, because the greater biaxial stress in PS restricts the process zone. 3) At initiation, the crack-tip radius, proportional to the local strain, is independent of CB. 4) The energy density within and the size of the process zone near the crack tip increase with CB; these are major contributions to CB reinforcement.
Elastic Stability of Rubber Products
Authors: Tabaddor Farhad 
Published: February 2011

Abstract
Due to severe nonlinearities, inherent in the finite-element elasticity, uniquely defined boundary-value problems of rubber elasticity may have multiple stable and unstable solutions. An early example was given by Rivlin, who considered the problem of a Neo-Hookean cube, in a state of pure homogeneous deformations, and subjected to three pairs of equal and opposite forces acting normally on the faces of the cube and distributed uniformly over them. He found that, for forces below a certain value, the only possible solution is the symmetric solution, as might be expected. Beyond that certain value, however, there are seven possible equilibrium solutions. One of these seven solutions is the symmetric solution. It is interesting to notice that the symmetric solution, which is initially stable, becomes unstable when loads have reached a certain threshold. The stability problems of homogeneous deformations of Mooney-Rivlin type of materials, under symmetric loading, for triaxial loading and for the plane stress and plane strain cases, are dealt with in Reference 3. It was shown that a finite-element method can be applied for such analyses. The stability of a sheet of Mooney-Rivlin type of material has been studied for a symmetrical loading condition. Such instability phenomenon was first observed by Treloar. In this work, the problem of a sheet of Mooney-Rivlin type of material, subject to general biaxial loading, is studied both analytically and by finite element. An energy approach to the problem is first presented. This problem represents the biaxial loading of rubber sheets or combined extension and inflation of rubber tubes, which are often used in experimental work for characterization of rubber materials. It is shown that the problem has multiple solutions for a certain domain of loading. The equilibrium state, actually attained, is dependent on the manner of quasistatic loading. Various stable solutions are obtained by finite element.
The Influence of Frictional Heating on the Sliding Friction of Elastomers and Polymers
Authors: McC. Ettles C. M. , Shen Jui Hsieh 
Published: February 2011

Abstract
The friction of polymers and elastomers has been widely researched, both in practical applications and in fundamental experiments. Although some of the basic mechanisms of elastomer friction have been well explored, the effect of frictional heating has not received much attention. This is surprising since the low thermal conductivity of elastomers can result in quite high temperatures being generated at the interface. This paper is concerned specifically with the influence of heat generation on the level of friction at the interface. Some present theories of elastomer friction are well established. The important factors that govern friction are considered to be the strength of interface bonds and the loss tangent, tan δ, where δ is the phase lag between harmonically applied strain and the stress response. On a rough surface, friction is considered to occur from hysteretic losses. On a smooth surface, friction is considered to occur from the formation of bonds across the interface, the extension of the bonds and their eventual fracture. In several quantitative models of elastomer friction summarized by Moore and Geyer, the result for friction is directly proportional to tan δ, thus for a perfectly elastic material, the friction (according to these models) tends to approach zero. Factors affecting the interface bond strength are somewhat better understood, Schallamach proposed that the bonds were molecular. This allowed an Eyring-type rate process theory to be applied, as illustrated with great clarity by Grosch. Grosch showed that the Williams-Landel-Ferry transformation could be applied to condense the friction-speed characteristics measured at various temperatures to a single “master curve.” These experiments gave convincing evidence that rubber friction is a thermally activated, molecular kinetic, stick-slip process. Grosch's experiments were later confirmed by Ludema and Tabor.
Friction on Ice
Authors: Ahagon Asahiro , Kobayashi Toshio , Mlsawa Makoto 
Published: February 2011

Abstract
The friction on ice is strongly dependent on temperature. At sufficiently low temperatures, the frictional resistance on ice is high comparable to those on wet or even dry solid surfaces. As temperature rises and approaches the melting point of ice, however, friction rapidly decreases. Differing from the friction of a rubber on ordinary dry or wet solid surfaces the energy loss processes in the rubber do not seem to be the direct source of the frictional resistance on ice. Although frictional melting of ice could occur at high sliding speeds, an ice surface is inherently lubricated with a persistent mobile fluid layer at relatively high temperatures, near the melting point of ice. When a rubber slides on an ice surface, the fluid layer is sheared and undergoes drag flow. The energy loss process necessary for the frictional resistance takes place primarily in the fluid layer, and not in the rubber. The frictional resistance on ice is primarily determined by the viscosity and the thickness of the lubricating fluid layer. What is required of a rubber for better traction under such a condition is that the rubber surface follows the topography of the ice surface as closely as possible, so that more patches of ice surface can be sheared. Therefore, the rubber has to be sufficiently soft to show high friction on ice. Further improvement of the friction could be obtained by making it more resilient. Thus, a rubber with high friction on ice must be compounded so that the polymer chains maintain a high level of mobility at moderately low temperatures. This can be achieved by using polymers with low glass-transition-temperatures. An increased softener loading level helps to improve friction, but to a limited extent. In order to take maximum advantage of softeners, the choice of softener system is important. A relation common to all the mixed softener systems, except the ones containing high-viscosity softeners, was found to exist between the friction on ice and the solubility parameter of the softener mixture in the rubber. The friction on ice was maximized by selecting a softener system with a solubility parameter near that of the polymers in the rubber. The solubility parameter dependence of the friction was consistent with those of softness and resilience.
Polyurea Synthesis and Properties as a Function of Hard-Segment Content
Authors: Chen Z. S. , Yang W. P. , Macosko C. W. 
Published: February 2011

Abstract
High-molecular-weight linear polyureas of different hard-segment content are obtained with a two-step solution polymerization. Elimination of water, careful choice of solvent, reactant concentration, and good control of reaction temperature are essential to obtain satisfactory results. We have studied the influence of the hard-segment content on the mechanical, dynamic-mechanical, and thermal properties of these solution polymerized amine-terminated polypropylene-oxide-based thermoplastic polyureas. Two-phase morphology is predominant within the range of the hard-segment concentration studied. Inversion of the continuous and dispersed phase might occur in the polyurea series at about 60 wt.% of hard segment. This changes the nature of the polyureas from a tough elastomeric material to a more brittle, high-modulus plastic. The modulus of the rubbery plateau measured from dynamic-mechanical spectra increases with hard-segment concentration due to the reinforcing effect of hard-segment domains. However, continuous improvement in dynamic-mechanical modulus is not significant when the hard segment is above 50 wt.% due to higher degree of phase mixing in high hard-segment concentration systems. The amount of solubilized hard segment in the soft-segment phase in these polyureas is limited as judged from the relatively constant soft-segment Tg. However, the extent of phase separation, as determined by the heat capacity change ΔCp across the soft-segment Tg, decreases with increasing hard-segment content. The same characterizations and analyses have also been carried out on a series of RIM produced polyurea samples of the same composition. Great difference in properties is observed in comparison of these two sets of samples due to their different synthesis routes. In general, samples produced by RIM exhibit lower molecular weight, lower dynamic-mechanical modulus, higher soft-segment Tg, more phase-mixed, and more tensile elongation than those synthesized by solution polymerization. The detailed comparison will be treated in a separate paper.
Application of Magnesium Hydroxide as a Flame Retardant and Smoke Suppressant in Elastomers
Authors: Holloway L. R. 
Published: February 2011

Abstract
This study has provided information about the performance of magnesium hydroxide in two EVA copolymers while also comparing the performance of the copolymers. The low-ethylene EVA tolerates the higher filler loadings of magnesium hydroxide more readily than the high-ethylene EVA. On the other hand, the latter has certain advantages, exhibiting higher tensile and tear strength values. Increasing the loading of magnesium hydroxide has a beneficial influence on tear strength and water adsorption. It was also interesting to note the differences in limiting oxygen index between the two sets of filled compounds. Compared with EPDM, much lower filler loadings are needed to achieve similar values of oxygen index. Taking all properties into account, the range 100 to 150 phr of magnesium hydroxide would be recommended for further development work.
Thermoplastic Elastomer Compounds from Sulfonated EPDM Ionomers
Authors: Paeglis A. U. , O'Shea F. X. 
Published: February 2011

Abstract
The zinc sulfonate of EPDM, an ionic elastomer polymer, can be readily formulated into useful thermoplastic elastomer compounds having beneficial properties and processing characteristics. The thermoplastic processing characteristics of these ionic elastomers are uniquely controlled by “ionolyzers,” preferential ionic plasticizers. These additives induce thermal reversibility in the ionic crosslink and control the response of the ionic associations to temperature. Ionic elastomer compounds maintain many of the performance features characteristic of vulcanized EPDM, such as low-temperature flexibility, thermal stability, and weatherability, while providing the added advantages of heat weldability and elimination of vulcanization. We have developed a cost-effective ionic elastomer formulation that meets or exceeds the RMA recommendations for black EPDM in a demanding, high performance application, single-ply roofing membrane. High-strength lap seams can be rapidly fabricated using portable hot air welders, a technique unavailable to conventional vulcanized EPDM sheet. Other applications have been investigated for these polymers, such as hose, footwear, mechanical goods, adhesives, impact modifiers, and asphalt modifiers both as thermoplastic elastomers and as modifiers for other materials. These applications have taken advantage of the unique rheological and solubility properties of these polymers. In addition, a new polymer grade offers an advance in the ability to formulate higher strength and more highly filled and extended ionic elastomer compositions.
Peroxide Curing of Ethylene-Propylene Elastomers
Authors: Keller Robert C. 
Published: February 2011

Abstract
1. Ethylene-propylene elastomers, suitably compounded for extrusion applications, can be readily vulcanized with organic peroxides to meet emerging requirements of improved performance and longer service life. 2. Aralkyl or dialkyl classes of peroxides produce the preferred cure performance, highest physical properties, and lowest compression set. Choice of peroxide governs rate of cure but not necessarily the optimum in crosslinking efficiency. 3. Coagents are essential to the development of optimum cure and stress-strain properties. The bis-maleimide is very effective in compounds that contain significant quantities of process oil, antioxidants for increased heat resistance, or other materials that consume free-radicals. 4. Ethylene-propylene compositional parameters influencing vulcanization activity are the diene, both type and concentration, and the ethylene content. Reactivity of the terpolymers is dependent on the type and amount of diene utilized in the polymer synthesis. High ethylene content improves crosslinking efficiency because there are fewer propylene sequences where chain scission can occur. 5. Increasing levels of hydrocarbon process oil needed in fast extruding compounds require higher peroxide concentrations to maintain cure and stress-strain properties.
A New Pull-Out Test for Tire Cord Adhesion—Part II. Cold Bonding
Authors: Ellul M. D. , Emerson R. J. 
Published: February 2011

Abstract
Coaxial Shear Pull-out Test samples which are essentially free from residual stresses can be fabricated using a cold-bonding procedure for the outer metal sleeve. Encapsulation of the rubber-cylinder—cord entity by the metal sleeve changes the type of deformation in the rubber from tensile as in the TCAT to simple shear. Consequently, a linear strain-energy analysis can be readily performed with good accuracy for the CSPT. This is the principal advantage of the CSPT over the TCAT. The work of adhesive or cohesive rupture, G, can then be easily determined with reasonable accuracy. G is a more meaningful estimate of the composite strength than the pull-through force used in standard ASTM tests, especially if adhesion with materials of different moduli and cords of various sizes are to be compared. Since shear stresses are predominant in tire belts, this model is assumed to simulate relative failures of such cord—rubber composites and is useful as a laboratory test for adhesion of tire cords to rubber.
The Nature and Action of Tackifier Resins
Authors: Aubrey Derek W. 
Published: February 2011

Abstract
A good tackifler resin appears to require a combination of high T9 at low molecular weight, and for this a highly condensed alicyclic structure appears to be desirable. Except for the rosin derivatives, the chemical structures of common tackifier resins are not fully resolved and some more definitive studies are needed. In addition, a high degree of miscibility of resin with rubber is important. Although some common tackifier resins cause phase separation over certain concentration ranges when blended with rubbers, this is probably exceptional, and it seems likely that most adhesive compositions are single phase in this respect. Where phase separation does occur, there is a need for fuller elucidation of the phase morphology and composition of the phases. The widely-held view that a two-phase morphology is necessary for the development of high tack appears to be incorrect. The few studies which have been carried out so far indicate that the surface energy of a rubber is modified only slightly by the incorporation of a tackifier resin. It is unlikely that this surface energy change can seriously affect the tack value as measured by the common form of probe test. The viscoelastic behavior of rubber-resin blends provides an adequate explanation for the phenomenon of tack. Over long response times, the low modulus (high compliance) of the blend compared with that of the rubber alone allows a high degree of intermolecular contact to be achieved during the bonding stage of a tack test. Over short response times, corresponding to the de-bonding stage of the test, the blend shows transition zone response with high energy dissipation and consequent high separation force. For further progress in our understanding, however, there is a need to distinguish clearly between the bonding and debonding effects of the resin and also for a more definitive study of the factors controlling the bonding stage.
Interfaces between Natural Rubber and Metals. Part I. A Study of the Interaction between Squalene and Steel Using XPS and SIMS
Authors: van Ooij W. J. , Rangarajan V. 
Published: February 2011

Abstract
1. XPS and SIMS in conjunction with a suitably chosen liquid model system form a powerful and highly complementary set of analytical tools for the study of the interaction between steel surfaces and unsaturated molecules; 2. We have presented evidence for an oxidative mechanism for the formation of a chemical bond between freshly abraded steel surfaces and squalene at 160°C. Such a bond can only be formed by unsaturated molecules on clean steel surfaces which exhibit a catalytic activity for the oxidation reaction. 3. This squalene approach appears to be very useful for the study and optimization of the bonding of 1,4-dienes to steel directly. The effects of the individual compounding ingredients on the rate of bond formation might conveniently be studied in this way in order to optimize compound formulations and surface preparations. The usefulness and limitations of a liquid model system such as squalene for the study of various aspects of natural rubber chemistry have been documented.