bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Stiffness Matrix of a Long Rubber Bush Mounting
Authors: Kari L.
Published: February 2011

The complete blocked dynamic stiffness matrix of a long rubber bush mounting of particular interest for noise abatement is examined by an analytical model, where influences of audible frequencies, material properties, bush mounting length, and radius, are investigated. The model is based on the dispersion relation for an infinite, thick-walled cylinder with arbitrary boundary conditions at the radial inner and outer surfaces; yielding the sought stiffness matrix, including axial, torsional, radial, and tilting stiffness. A nearly incompressible material model is adopted, being elastic in dilatation while displaying viscoelasticity in deviation. The applied deviatoric Mittag-Leffler relaxation function is based on a fractional standard linear solid, the main advantage being the minimum number of parameters required to successfully model the rubber properties over a broad structure-borne sound frequency domain. The dynamic stiffness components display a strong frequency dependence at audible frequencies, resulting in acoustical resonance phenomena, such as stiffness peaks and troughs. The low-frequency stiffness asymptotes of the presented model are shown to agree with those of static theories.
Specific Influences in the Polymerization of Dienes. Chemical Factors Influencing the Homogeneity of Synthetic Rubbers during Production
Authors: Penn William S.
Published: February 2011

At the present time, when so much synthetic rubber is being produced, the question of the polymerization of dienes is most important. Many thousands of tons of GR-S and related rubbers are being made by this means, and yet the process is only very imperfectly understood. Polymerization is still an uncontrolled reaction, although much work has been done in an attempt to overcome the deficiencies. The troubles are caused by the fact that the dienes do not polymerize in a regular way, because of the formation of branch chains and cross-linkages, which are a direct result of these branch chains. These irregularities must be controlled before satisfactory products can be obtained, and the present paper is written to correlate isolated evidence and present fresh material so that the processes involved during polymerization may be more perfectly understood and possibly controlled. It is natural in the first instance to examine natural rubber to see if any indication of the lines to follow can be obtained. Unfortunately, however, even natural rubber is not perfect, and from various sources of evidence it has been shown that branching does occur in the isoprene chains. This branching is, however, different from that in synthetics, and is quite regular. As will be seen shortly, it is difficult on chemical or physico-chemical grounds to see why this should be so, as the only directive group in the isoprene unit is the methyl side-group. It seems logical to conclude that natural rubber is not formed by a polymerization process, but that carbon and hydrogen atoms combine in such a way that they form directly a natural rubber-molecule.
The Polymerization of Methacrylonitrile. Polymethacrylonitrile
Authors: Kern Werner , Fernow Helmut
Published: February 2011

As the starting point for the preparation of methaerylonitrile, acetonecyanohydrin (α-hydroxybutyronitrile) was chosen because of its ready availability. β-Hydroxybutyronitrile should likewise be well suited for the purpose, but, because of the difficulties involved in its preparation, it was not utilized in the work. The removal of water can be accomplished in various ways. (1) Phosphorus pentoxide does not give such smooth results as it does with ethyleneeyanohydrin, but the reaction can be carried out successfully by centrifuging and the addition of quinoline. Under the same conditions acetaldehydeeyanohydrine (lactonitrile) yields no acrylonitrile. (2) The thermal decomposition of acylated hydroxy-acid derivatives can be applied to acetonecyanohydrin, but this method of preparation is difficult to carry out on a laboratory scale. (3) Removal of water can be carried out very smoothly with thionyl chloride. In addition to methacrylonitrile, α-chloroisobutyronitrile is formed, and from the latter more methacrylonitrile can be obtained by scission of hydrogen chloride. In this procedure, it is highly important to use pure raw materials, especially thionyl chloride, for with pure compounds the yields are higher. It is likewise advantageous to use a slight excess of thionyl chloride.
The Production of Rubber from Furfural
Authors: Burnette Llewellyn Wilson
Published: February 2011

The preparation of piperylene, or 1,3-pentadiene, from furfural has been undertaken with the view of developing a commercially practical process. Although other paths are possible, the following three steps were considered the most direct and feasible. During the course of this study, a patent was granted which covered essentially the same process, but the claims, particularly of the last two steps, were not substantiated in this laboratory. Vapor-phase catalytic reactions were utilized in the process. For the first two steps, a vapor phase hydrogenation apparatus with a recirculation device, was employed. This effected the saving of considerable quantities of hydrogen and uncondensed materials. The apparatus could also be employed for the dehydration in the last step. More than twenty catalysts were studied for the conversion of furfural to methylfuran (sylvan). Only two types were found to be satisfactory. The copper deposited from the decomposition of copper acetate on a carrier such as activated charcoal was found to give yields of the order of 80–85 per cent consistently with one passage of the furfural over the catalyst. The best catalyst tried, however, was copper chromite dispersed on activated charcoal. This has been observed to give a yield of 95 per cent of sylvan in one passage. The optimum temperature observed for these catalysts was around 200° C. It is interesting to note that copper chromite in the liquid phase produces furfuryl alcohol (or tetrahydrofurfuryl alcohol according to the conditions used) in quantitative amounts.
The Mechanism of Reinforcement
Authors: Goldfinger G.
Published: February 2011

In the fundamental study of the influence of reinforcing pigments, particularly carbon black on rubber, one of the great experimental difficulties is to establish the stress-strain properties of that fraction of the rubber stock which is between the pigment particles, and whose deformation, influenced by the presence of the pigment, is the quantity desired. This paper shows that it is not justifiable to assume that the rubber between pigment particles is equivalent in properties to the original gum stock without pigment, because the addition of pigment induces fractionation of the rubber in such a manner as to concentrate preferentially one molecular configuration around the pigment particle, and hence leave the rubber richer in some other configuration in the spaces between pigment particles.
Stress-Temperature Relations in a Pure-Gum Vulcanizate of Natural Rubber
Authors: Wood Lawrence A. , Roth Frank L.
Published: February 2011

Stress-temperature relations at constant elongation have been investigated for a pure-gum vulcanizate of natural rubber. The rubber was first allowed to relax for about two hours at constant elongation and constant temperature to minimize the effects of short time relaxation of stress. The stress, except under special conditions, was changing very little at the end of this time. The stress-temperature relations for temperatures below the relaxation temperature could be represented by straight lines. The values of the slopes and intercepts of these lines are presented in tabular form. The stresses at the end of the relaxations were used as the basis of stress-strain curves. Crystallization was found to be an easily-recognized factor of considerable importance in the interpretation of the results.
The Stiffness of Rubber on Bending, or Its Dynamic Hardness. The Method of Resonance Vibrations
Authors: Reiss K. H.
Published: February 2011

When used for industrial purposes, vulcanized rubber products must often meet an extraordinarily complex set of requirements. Not only are they subjected to shearing stresses, but they must withstand various compression, tensile and bending stresses, such as are encountered in V-belts, conveyor belts, and diaphragms. In many cases these stresses are very rapid, and consequently a knowledge of the dynamic stiffness of a product may often be of technical interest and value. As will be shown, this dynamic stiffness cannot be estimated directly in terms of static hardness, for it depends also on the character of the fillers or pigments in the rubber.
Dichlorostyrenes and Their Polymers
Authors: Michalek J. C. , Clark C. C.
Published: February 2011

Styrene, which was first synthesized by Berthelot in 1866, has done much to foster the rapid growth of those two prodigious youngsters of chemical industry—synthetic rubber and plastics. Polymerized to polystyrene, it has made available a thermoplastic with good dimensional stability and unique insulating properties. Copolymerized with butadiene, it has made possible the widely used GR-S (or Buna-S). Both polystyrene and GR-S have suffered from a common difficulty. They are adversely affected by heat. The strength of GR-S is greatly decreased at the high temperatures developed by heavy-duty tires. Polystyrene wilts below the temperature of boiling water, and, as a result, its uses have been restricted. Attempts have been made to modify polystyrene and GR-S by the addition of other compounds to the plastic or rubber-compounding formula. These have been successful in raising the heat resistance of such materials at the expense of other valuable characteristics, such as the insulating property of polystyrene.
Large Deformation Analysis for a Cylindrical Hyperelastic Membrane of Rubber-Like Material under Internal Pressure
Authors: Guo Xiaoping
Published: February 2011

This work studies the large deformation of a cylindrical hyperelastic membrane circumferentially bonded and sealed at each end to a rigid tube. The membrane is subjected to the delivery of an inflating fluid through the tubular channel, causing it to undergo the large, quasi-static axisymmetric deformation. The membrane is made from a rubberlike material and assumed to be isotropic and incompressible. The Lagrangian formalism is employed to develop geometric relations of the deformation field and the system of governing equations in terms of principal stretches and Cauchy stresses. With the material's constitutive laws and proper boundary conditions, the incorporation of the geometric relations and governing equations is made to derive the numerical solution system of the deformation field in the form of two-point boundary-value problem as composed of four first-order ordinary differential equations. Special attention is given to relevant numerical formulation. The Newton-Raphson iterative algorithm, together with the fourth-order Runge—Kutta algorithm, is utilized. A geometric approximation on an inflated bulge is presented to give an initial guess to a deformed membrane profile. In an attempt to obtain convergent behavior of numerical solution along the equilibrium path of deformation, a displacement control strategy is suggested to mimic the quasi-static volume-controlled inflation process. Numerical results are presented. The occurrence of deformation instability is discussed. The effects of various strain energy density functions on inflation kinematics are analyzed.
Relationships Between Mixing Method, Microstructure and Strength of Nr:Br Blends
Authors: Clarke J. , Clarke B. , Freakley P. K.
Published: February 2011

Much published literature on the way in which phase morphology and filler distribution affect blend properties is contradictory or confusing. Experiments were carried out to elucidate the relationships and to determine whether the use of compatibilizers or special mixing techniques might have a beneficial effect on natural rubber:butadiene rubber (NR:BR) blend properties. NR:BR blends were prepared using both a masterbatch method and a single-stage mixing method. A cure system which gave an even distribution of crosslinks between the phases was used. The morphology, tensile strength and tear strength properties of the blends were measured. Results indicated a high degree of compatibility with fine textured blends (domain sizes < 1µm) being quickly and easily produced, even from masterbatches of very different viscosities. Strength properties of these fine textured masterbatch blends could be predicted by applying the simple rule of mixtures to properties of individual compounds mixed under the same conditions. Although in particular situations a coarse morphology could result in high tear resistance values, for most applications a fine textured morphology gives the most satisfactory overall tensile and tear strength properties. For blends mixed in a single-stage process, development of a fine textured morphology was much quicker than that of filler dispersion. For NR:BR blends containing an optimum cure system it was concluded that the mixing cycle should be chosen to optimize filler dispersion and that use of a compatibilizer will not significantly shorten the mixing cycle or improve the properties of the blend.
Reversion Stable Networks with Polysulfide Polymers as Vulcanization Agents
Authors: Hahn J. , Palloch P. , Thelen N. , Weidenhaupt H-J.
Published: February 2011

To study the network structure generated by the polysulfide polymer [[(CH2)2S4]p as a crosslinking agent, model compound vulcanization with 2,3-dimethyl-2-butene as the model alkene was carried out. It was found that the polysulfide polymer generates hybrid bridges of the general constitution Sn−(CH2CH2−Sm)k(n=1−4,m=1−4,k=1−6). To a lesser extent the polysulfide polymer behaves as a sulfur donor generating conventional sulfur bridges Sx(x=1−5). Polysulfidic bridges (x=4, 5) were only detected in the very early stage of network formation. The process of network formation and the development of the bridges during prolonged heating was monitored by 1H NMR spectroscopy and compared with that of a sulfur cure. In the case of the polysulfide polymer cure the early network contained a relatively high amount of mono-and disulfidic bridges and a stable network was formed after at least 60 min of heating (150 °C). This effect results from the higher thermal stability of hybrid bridges in comparison to conventional sulfur bridges. The higher stability of the hybrid bridges also leads to a suppression of the formation of 3,4-dimethylthiophene which has been identified in the sulfur cure as a product of reversion processes. Thus, the increased reversion stability of polysulfide polymer cures, which has been claimed earlier, can be related to the formation and the increased stability of the hybrid bridges.
Ozonation of Unstretched Natural Rubber: Part I. Effect of Film Thickness
Authors: Rodrigues F. H. A. , Santos E. F. , Feitosa J. P. A. , Ricardo N. M. P. S. , de Paula R. C. M.
Published: February 2011

Unstretched films of natural rubber from Hevea brasiliensis were exposed to ozone flow of 5 and 15 mL/min for 4 to 60 min. The effect of reaction time and the film thickness was studied by viscometry and gel permeation chromatography (GPC). For film thicknesses, in the range of 40 to 350 µm, an initial increase in the intrinsic viscosity, [η], was observed within 8 min of reaction, followed by a decrease for longer times. For thin films, only a decrease in the [η] was observed. The viscosity increase, followed by its decrease, suggests the formation of crosslinking and chain cleavage, respectively, both expected by Criegge mechanism. The plot of [η] versus film thickness and the Chromatographic analysis, related either to 8 or to 60 min of reaction, show that the ozone penetration and the ozone reaction progresses into deeper layers than those previously described in the literature (∼0.5 µm), in this case, 170 and 250 µm, respectively. One model was proposed to explain the viscosity, GPC and attenuated total reflection (ATR) results.
Aging of Natural Rubber in Air and Seawater
Authors: Mott P. H. , Roland C. M.
Published: February 2011

Accelerated aging experiments were carried out on a natural rubber vulcanizate exposed to air and to seawater. Failure strain, shown to correlate well with the fatigue lifetime, was used to monitor the extent of degradation. The effect of temperature on the rate of aging followed an Arrhenius law, with activation energies equal to 90 ± 4 and 63 ± 3 kJ/mol for air and seawater aging, respectively. The difference can be accounted for by the difference in oxygen concentration for the two environments.
Structural Characterization of Natural Polyisoprenes: Solve the Mystery of Natural Rubber Based on Structural Study
Authors: Tanaka Yasuyuki
Published: February 2011

Structural characterization of naturally occurring polyisoprenes was carried out to solve the mystery of natural rubber (NR), such as the biosynthesis mechanism of rubber formation, the origin of outstanding properties of NR and the role of rubber in rubber trees. The NMR analysis, based on terpenes and polyprenols as models, disclosed the structure of both terminal groups of rubber chain. Structural evidence indicated that the biosynthesis of rubbers from Lactarius mushroom and leaves of high plants starts from trans, trans-farnesyl diphosphate or trans, trans, trans-geranylgeranyl diphosphate and terminates by dephosphorylation to form a hydroxyl terminal group. The biosynthesis of NR was presumed to start from unidentified initiating species containing two trans-isoprene units and peptide group and to terminate forming a phospholipid terminal group. The initiating group of NR associated with proteins formed branch points, which can be decomposed by enzymatic deproteinization. The branch points formed by phospholipid group were decomposed by transesterification with sodium methoxide. Rapid crystallization of NR was explained by the presence of mixed fatty acids synergistically with linked fatty acids, which were included in phospholipid. Saturated fatty acids linked to rubber chain induced crystallization, while mixed unsaturated fatty acids acted as plasticizer and accelerated the crystallization rate. This was confirmed by the preparation of model cis-polyisoprene grafted with stearic acid. The green strength of NR decreased to the same level as synthetic cis-polyisoprene after transesterification, indicating the effect of branching formed by the phospholipid terminal group and fatty acids in NR. The role of NR in Hevea trees was analyzed using NR from Hevea trees never tapped before. The formation of hard gel and oxidative degradation during the storage of NR in Hevea trees suggested that NR acted as a radical scavenger to remove hydroperoxide.
The History of Rubber—A Survey of Sources about the History of Rubber
Authors: Long Joan C.
Published: February 2011

This paper is a bibliographic survey of the major sources of information about historical aspects of rubber and rubber products that appeared in the 20th century. These sources, primarily those in the English language, on various aspects of rubber history have been categorized according to whether the emphasis is on natural or synthetic rubber, general rubber history and processing, rubber organizations, and people and companies that have played an important role. A section on the history of tires is included.
Fundamentals of Rolling Resistance
Authors: Hall David E. , Moreland J. Cal
Published: February 2011

Increasing pressure over the last three decades to improve vehicle fuel economy and decrease emissions along with a strong sense of environmental stewardship has driven the tire and rubber industries to reduce tire rolling resistance. This has been accomplished while simultaneously improving other aspects of tire performance dramatically. Reductions in rolling resistance of 50% relative to 1980 levels have been realized, and efforts continue to decrease rolling resistance further. Laboratory measurement and empirical modeling of rolling resistance behavior have evolved substantially, and the tire industry can characterize a tire's rolling resistance with great precision and accuracy. Rolling resistance behavior is quite complex, and nearly all conceivable operating conditions have a measurable effect. The effect of each parameter has received considerable attention in the archival literature, and this review highlights the conclusions of these studies. One of the most powerful tools available to the tire industry is numerical modeling. Combined with accurate dynamic material property measurements, finite element models have provided designers with a tool to understand the behavior of each rubber product and optimize tire construction and material properties to minimize rolling resistance. However, with the current level of understanding and optimization of rolling resistance, substantial breakthroughs in the areas of material development and tire construction are needed to achieve further rolling resistance reductions.
Basic Studies on Development of Structure Hierarchy in Tubular Film Blown Dynamically Vulcanized PP/EPDM Blend
Authors: Wang M. D. , Cakmak M.
Published: February 2011

The processing characteristics and structural hierarchy development in a tubular blown, dynamically vulcanized polypropylene/ethylene—propylene—diene monomer rubber (PP/EPDM) blends were investigated. The semi-crystalline PP phase exhibited a* and c-axis orientations with the a* oriented populations dominating low draw-down ratio (DDR) conditions. At high DDR, both a* and c-axis oriented populations were observed. Little or no preferential orientation was detected in the discrete EPDM phase using dichroism studies. The blown films were found to exhibit an unusual asymmetric structure: The PP phase was found to fibrillate at the outside surface while the inner surface remained relatively featureless. This was attributed to disproportionately rapid cooling of the outside surface by the air stream blown externally onto the film being extruded. This, in turn, resulted in solidification of very thin PP surface layers that caused their fibrillation under the heavy stresses they had to endure. Increasing the blow-up ratio was found to expand this web-like surface texture. As a result of this fibrillation mechanism, the increase of both the blow-up ratio and draw-down ratio was found to reduce the mechanical properties.
Carbasulfanes as Crosslinker for Dienerubber — A Model Compound Study
Authors: Hahn J. , Palloch P. , Walter E. , Thelen N.
Published: February 2011

Model compound vulcanization in combination with reversed-phase high-performance liquid chromatography (RP-HPLC), NMR spectroscopy, and mass spectrometry was used to study the properties of the polysulfide polymers [Sx(CH2)y]p  (x=2,3,4, y=1,2,3,6) as crosslinking agent in the vulcanization process. It was found that the tetrasulfidic polymers [S4(CH2)y]p are capable of forming hybrid bridges of general constitution Sn-[(CH2)y-Sm]k. Besides, they react as sulfur donors producing ordinary sulfur bridges. The yield of hybrid bridges strongly increased when the alkanediyl unit ((CH2)y) of the polymer was changed from methanediyl (y =1) to ethanediyl (y =2) and remained nearly constant for longer alkanediyl segments (y =3, 6). In general, the repeating unit k also increased with increasing length of the alkanediyl segment. The only exception was observed for poly(tetrathiopropanediyl) [S4(CH2)3]p. Compared to [S4(CH2)2]p it gave a slightly lower portion of hybrid bridges and also the maximum value of k appeared to be somewhat reduced. When the number of sulfur atoms in the poly(polythioethanediyl) polymers [Sx(CH2)2]p(x=2–4  was reduced from 4 to 3 the yield of bridged molecules diminished slightly. But in the case of the disulfidic polymer nearly no crosslinked products were observed. The disulfidic polymer could be activated by the addition of sulfur into the vulcanization mixture. Hybrid bridges Sn-[(CH2)6-Sm]k of low k-values were obtained when 1,6-bis-(N,N-dibenzyl-thiocarbamoyldisulfido) hexane was used as curing agent. In addition to RP-HPLC, we also used gel permeation chromatography (GPC) in the characterization of the vulcanizates. In contrast to RP-HPLC, where the number of sulfur atoms has the strongest influence on the retention time, GPC separates the vulcanization products according to the number k of alkanediyl units present in the hybrid bridge.
Pyrolysis-GC/MS and TGA as Tools for Characterizing Blends of SBR and NBR
Authors: Shield Stephanie R. , Ghebremeskel Ghebrehiwet N. , Hendrix Cebron
Published: February 2011

There is increased technological interest to use blends of various dissimilar elastomers in applications for which service, material availability, or cost of a single elastomer do not provide the necessary processing, vulcanizate, or economic properties. Properties of polyblends are sensitive to variations in the amounts of the individual polymers used. Therefore, there is a need for developing a variety of analytical tools that will enable the compounder to monitor the consistency of blend compositions. In this study, the feasibility of using pyrolysis-GC/MS and thermogravimetric analysis (TGA) to estimate the blend composition of SBR/NBR blends was investigated. Pyrolysis-GC/MS degradation products that are characteristic of each polymer were identified. The GC/MS peak areas were used to determine the blend composition. The blend compositions were estimated by TGA from the linear correlation between the polymer composition and the temperature required to pyrolyze a sample to a specific “% weight loss.” The results obtained by pyrolysis-GC/MS and TGA were compared to calculated blend ratios of SBR/NBR in order to estimate the accuracy of the test methods presented in this study.
Synthesis, Characterization and Properties of Montmorillonite Clay-Polyacrylate Hybrid Material and its Effect on the Properties of Engage-Clay Hybrid Composite
Authors: Ray Sudip , Bhowmick Anil K.
Published: February 2011

Clay-Polyacrylate hybrid material was prepared from Montmorillonite (M) clay and polytrimethylol propane triacrylate (PA) using intercalation polymerization process. Characterization of the composite was done by x-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) techniques. The results show the successful intercalation of PA in the M moiety. The MPA hybrid material was then blended with a polyolefin elastomer, Engage. Tensile and dynamic mechanical properties were measured on the polymer-filler composite and the results showed interaction between the treated clay and the base polymer. There was a significant improvement in modulus, tensile strength and elongation at break of the base polymer as compared to the composite prepared with the untreated clay.
Effect of Degree of Neutralization on the Properties of Ionic Thermoplastic Elastomer Based on Sulfonated Maleated Styrene-Ethylene/Butylene-Styrene Block Copolymer
Authors: Ghosh Swapan K. , Bhattacharya A. K. , De P. P. , Khastgir D. , De S. K. , Peiffer Dennis G.
Published: February 2011

Novel block copolymer ionomers having both carboxylate and sulfonate groups in the same polymer backbone were obtained by sulfonating maleated poly (styrene-(ethylene-co-butylene)-styrene) block copolymer (m-SEBS), followed by its neutralization with barium acetate. The effects of the degree of neutralization on the properties of the ionomers were studied. Infrared spectroscopic studies confirm the formation of both carboxylate and sulfonate salts and the occurrence of the sulfonation reaction in the para position of the benzene rings of polystyrene segments. Dynamic mechanical thermal analyses show the presence of a high temperature rubbery plateau, particularly at high degree of neutralization, in addition to the glass-rubber transitions due to the polystyrene (PS) and ethylene-butylene (EB) phases. Tg of the PS block remains unchanged and tanδ at the Tg gradually decreases with increasing the degree of neutralization. But Tg of the EB block gradually increases and tanδ at the Tg marginally increases. The decrease in tanδ at δ of the PS block is ascribed to the stiffening of the polystyrene segments on neutralization.Increase in the degree of neutralization causes formation of ionic crosslinks which increases the Tg of the EB block. Dielectric thermal analyses show that incorporation of ionic groups plays an important role in the temperature dependence of the dielectric constant of the ionomers. At lower degrees of neutralization (25 and 50%), the ionomers behave like the base polymer in the sense that dielectric constant increases at elevated temperature(>120°C). At higher degrees of neutralization, however, the increase in dielectric constant in the high temperature region is restricted due to the formation of the rubbery network arising out of the ionic aggregates. Transmission electron micrographs reveal that on neutralization the domain shape changes from predominantly cylindrical type to exclusively spherical one and at 100% neutralization the diameter of the spheres ranges from 15 to 20 nm. Processability studies show that as the degree of neutralization increases, the melt viscosity of the ionomers increases. The tensile strength, hardness, modulus and tear strength increase but the elongation at break and tension set decrease with increase in the degree of neutralization. Thermal stability of the polymers increases with the degree of neutralization. Reprocessability studies show that the ionomer can be recycled without fall in properties. The barium salt of sulfonated maleated SEBS at higher degrees of neutralization (75 and 100%) behaves as an ionic thermoplastic elastomer.
Better Process Description for the Extrusion of Silica and Carbon Black Compounds
Authors: Limper A. , Schramm D.
Published: February 2011

In comparison to plastics processing, rubber processors handle a much more complex material. Due to active fillers used in rubber compounds, such as carbon black and silica, in some cases extraordinary filler/filler interactions occur. In general the multi-component system leads to a very complex rheological behavior. If silica compounds e.g. are processed the chemical modification of the filler surface (by organosilanes) has to be taken into account. By this the rheological behavior of the material changes dramatically. All these circumstances make rubber processing to a very complex theme. This paper presents results which are obtained within an European research project. The work is focussing on a better process description of the extrusion process of rubber compounds. It handles both applications of the extrusion process, i. e. for technical rubber goods or for making tire parts like the extrusion of tread stripes. Hence in this paper a new approach for modeling the flow in the extruder screw will be presented. Using this as a simulation tool a systematic analysis of the extrusion process is possible in reasonable time. Another field of interest in this context is the rheological characterization of rubber compounds with a so called „Extrusion-Rheometer“. The advantages of this device will be shown for the investigation of processability and gathering representative rheological data for recalculations of screw and die flow in the extrusion process.
Rubber Chemicals Derived from Conjugate Addition. I. Syntheses of Novel 2-Thio-5-Amino Substituted Benzoquinones
Authors: Katritzky Alan R. , Odens Herman H. , Voronkov Michael V. , Rostek Charles J. , Maender Otto W.
Published: February 2011

Alkylthio-substituted benzoquinones were prepared from benzoquinone and mercaptans in 50–94% yields via NaIO4 oxidation of the intermediate hydroquinones. Subsequent addition of primary and secondary amines, in the presence of air as an oxidizing agent, gave a range of 2-thio-5-amino-substituted benzoquinones. No oxidation at sulfur was detected under the described conditions.
A Comparative Study of Styrene Polymerization in Deproteinized and Undeproteinized Natural Rubber Latex
Authors: Tho Nguyen V. , Kadir Mohd Omar Abd , Hashim Azanam S.
Published: February 2011

An investigation on in situ polymerization of styrene in deproteinized natural rubber (DPNR) latex and high ammonia natural rubber (HANR) latex was carried out. The ratio of styrene to dry rubber was fixed at 25 : 75 by weight. It was observed that, at reaction temperature of 60 °C and reaction time of 10 hours, the styrene-DPNR system could attain a high conversion of 97% without adding surfactant. The degree of chemical bonding estimated for the resultant polystyrene-DPNR dried material was about 80%. The styrene-HANR system, however, required the addition of surfactant to complete the reaction time; but the conversion was found to be relatively low, in the region of 66%. This low conversion could be attributed to the role played by the protein/lipid layer, which is virtually absent in the styrene-DPNR system.
Dispersion Studies of Agglomerates in Steady and Dynamic Flows of Polymeric Materials
Authors: Levresse P. , Manas-Zloczower I. , Feke D. L.
Published: February 2011

The hydrodynamic dispersion of spherical calcium carbonate agglomerates was studied under both steady and oscillatory shear-flow conditions. For a given intensity of steady shear flow, erosion rates were strongly influenced by the cohesive strength of the agglomerates with less cohesive, low-density agglomerates exhibiting faster erosion than high-density agglomerates. The dispersion kinetics were also affected by the extent of matrix infiltration within the agglomerate, with more infiltration resulting in reduced erosion rates. Experiments conducted in oscillatory shear flow fields provided new insights on local mechanisms of erosion.
Thermoplastic Elastomers and Rubber-Toughened Plastics from Recycled Rubber and Plastics
Authors: Liu H. , Mead J. L. , Stacer R. G.
Published: February 2011

An experimental investigation has been conducted to evaluate the use of recycled rubbers in blends for the development of new thermoplastic elastomers (TPE) and rubber-toughened plastics. The recycled rubbers were obtained from various commercial sources and included representatives from the EPDM, SBR, and NR/SBR blend families, as well as a range of particle sizes. A series of five different virgin polypropylenes (PP) were used as the plastic phase, representing a range of molecular weights and suppliers. Blends were prepared in a Haake Buechler batch mixer over a broad range of constituent fractions. Compatibilization and reactive blending techniques were used to improve the quality of the scrap rubber/plastic blends with respect to both mechanical and rheological properties. Results indicate that these blending techniques are required to obtain acceptable mechanical strength in the resultant materials. Additional parameters that significantly enhanced properties included elevating the blending temperature, reducing rubber particle size, and increasing PP molecular weight. This later conclusion was attributed to a lower degree of crystallinity in the PP phase that contributes to better blending between the phases.
The Fracture Behavior of Rubbery Vulcanizates: I. Single Component Versus Blend Systems
Authors: Qazvini N. Taheri , Mohammadi N. , Jalali A. , Varasteh A. , Bagheri R.
Published: February 2011

The tear energy and heat build up of NR, SBR and BR vulcanizates and their corresponding blends were measured at several temperatures via modified trouser tear and Goodrich flexometer experiments. In all single component samples, by increasing temperature from -10 to 125 °C, the fracture energy decreases, goes through a minimum and increases again. Nevertheless, in SBR and BR, a level off and a level off followed by second drop occur at higher temperatures, respectively. On the other hand, for aforementioned samples the heat build up decreases monotonically by raising the temperature. For two-component blends, the fracture energy and heat build up show different dependencies on temperature in comparison to single component systems. The fracture energy either increases, does not change at first and then decreases, or does not change as the temperature increases. While the heat build up is more or less constant by raising the temperature up to a certain point and then decreases but by a different path from single component vulcanizates. These peculiar behaviors are attributed to the competition between residual stress release and reduction of viscose loss term, while the temperature increases.
Weld-Line Strength of Rubber in Injection Molding: Effect of Injection Factors and Compound Characteristics
Authors: Seadan M. , Pongbhai P. , Thairaj P. , Kamtornkul T. Watana
Published: February 2011

The effect of injection molding system to weld-line strength in rubber O-rings was studied using a V-shape two-stage REP injection machine. Two types of injection molds were designed and built, a standard dumbbell mold with double gates and a circular cross-section O-ring mold. Several formulations of carbon black filled NR and SBR compounds were used and vulcanization temperature was either 180 or 200 °C throughout. The results show that mold cavity pressure, compound viscosity and compound scorch time are important variables for the weld-line strength of the products. The shot volume change had no direct effect on strength, but mold cavity pressure was an important factor; unfilled shot volume gave low cavity pressure thus lowering the weld-line strength of the O-rings. The compounds having 45 or lower Mooney viscosity, ML(1 + 4)120 °C, had the same weld area strength as that of the other regions of the O-ring, but the high viscosity compounds produced low weld-line strength. Only the compounds with Mooney scorch time shorter than 10 minutes gave low weld-line strength.
Cure Kinetics for Silane Coupled Silica Filled SBR Compounds
Authors: Jeong Jae-Hyeuk , Moon Chae-Woo , Leonov Arkady I. , Quirk Roderic P.
Published: February 2011

Vulcanization kinetics for silane-modified, silica-filled SBR has been investigated using the cure meter and swelling measurements to determine the crosslink density. The silane modifier was Si-69, bis(3-triethoxy-silylpropyl)tetrasulfane. To simulate the induction and curing periods as a function of temperature and compounding recipe, a three component kinetic model for curing was developed. The kinetic model consists of (a) curing in the bulk elastomer phase, (b) curing at the silica surface and (c) cross-phase curing between the bulk components and the silica surface. In order to describe the partitioning of reagents between the bulk and surface domains, the parameter reactive surface thickness,θ, was introduced into the kinetic model. An average value of 24.7 nm for θ was calculated from the kinetic data and the silica particle surface area. Physically significant model kinetic parameters were extracted from the experimental data using a cure meter at different temperatures for (a) bulk curing (no filler) using the model of Ding and Leonov; (b) curing at the silica surface with Si-69 (no sulfur); and (c) whole compound recipe. Crosslink density values determined from the shear modulus were in good agreement with results from equilibrium swelling measurements. Using experimental data from the cure meter studies at 160 and 180 °C, it was possible to calculate (predict) the cure meter data at 140 °C for several different recipes.
Rubber Recycling
Authors: Myhre Marvin , MacKillop Duncan A.
Published: February 2011

For both environmental and economic reasons, there is a continuing broad based interest in recycling of scrap rubber and development of recycling technologies. The use of post- industrial scrap is established as a systematic business. However, the disposal and reuse of scrap tires remains a serious environmental concern and a business opportunity. The method for reclaiming rubber utilizing aqueous alkaline solutions has been abandoned in North America because of environmental pollution hazards. The focus of more recent research is to apply processes that do not generate disposal hazards and that might be carried out directly in the product manufacturer's factory. The major process at the present time is to utilize the scrap rubber as a very finely ground crumb. Crumb is produced either by ambient temperature mechanical grinding or by cryogenic shattering. In general, the crumb rubber is combined with virgin elastomer compounds to reduce cost. However, there is some loss in physical properties and performance. This factor has motivated the search for cost effective in-situ regeneration or devulcanization of the scrap rubber to provide superior properties. Some progress has been achieved utilizing mechanical shear, heat and other energy input, and a combination of chemicals such as oils, accelerators, amines, etc. to reduce the concentration of sulfur crosslinks in the vulcanized rubber. The major application of scrap rubber, particularly as crumb, is outside the conventional rubber industry. More than half of the scrap is burned for its fuel value for generation of electricity and as a component in cement production. The utilization in extension of asphalt in road construction is now recognized to provide superior road performance and reduced cost. The simple use of crumb rubber as a component in artificial turf is developing into a significant industry. Rubber crumb is now widely utilized in rubber products such as mats, floor tiles, carpet undercushion, etc., where the crumb is rebonded using polyurethane or latex adhesives. Other applications, such as in landfill, concrete, thermoplastic blends, pyrolysis to generate carbon black and chemicals, are discussed. The tire industry does utilize a significant proportion of fine crumb rubber in tire compounds. This is likely to not increase much due to the concern about tire performance and safety. However, there is a serious interest by tire manufacturers to increase the use of scrap tire rubber, if the recycled rubber could be regenerated to improve compatibility and performance in tire compounds.
Microscopy of Rubber Products
Authors: Smith Ronald W.
Published: February 2011

This paper is a review of published literature containing some aspects of rubber product analysis using microscopy techniques. This includes close-up photography, photomicrography, photomicrography obtained from light optical microscope (LOM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Products represented are tires, belts, hoses, seals, rubber bands, balloons and some miscellaneous products such as a submarine hydrophone boot, rubber mat, shoe soles, tire curing bladder, and roofing membrane.
Structure Optimization in Colloidal Reinforcing Fillers: Precipitated Silica
Authors: Schaefer Dale W. , Chen Chunyan
Published: February 2011

In an attempt to elucidate the role of filler morphology in elastomer reinforcement, we use x-ray, light and neutron scattering to determine the structure of precipitated silica powders. We find the signatures of at least three levels of structure: primary particles, aggregates and agglomerates. By observing the evolution of the scattering profile during solution synthesis, we are able to identify when these structures appear. We also investigate the effect of ionic strength on morphology and find evidence for the interpenetration of aggregates on drying of powders prepared at low ionic strength. Using a reinforcement model by Witten, Rubinstein and Colby, we conclude that the ideal filler will consist of soft agglomerates made up of hard aggregates. Based on the dependence of morphology on synthetic protocol, we present strategies for design of efficient reinforcing fillers.
The Effect of Interphase Coupling on the Structure and Mechanical Properties of Silica-Siloxane Composites
Authors: Schaefer Dale W. , Vu Bic T. N. , Mark James E.
Published: February 2011

Silica-reinforced siloxane composites are synthesized with heat labile azo groups at the polymer-filler interface. The azo group serves as a “smart interface” in that it is responsive to heat. This system is used to assess the influence of interfacial chemical bonds on mechanical properties. By thermally severing the azo linkage, we can determine the influence of interfacial bonding on properties independent of other morphological factors. The virgin filler powders, azo-modified powders, silica-filled composites and azo-modified-silica-filled composites are characterized using small-angle x-ray scattering, IR spectroscopy, and scanning electron microscopy. Mechanical properties are correlated with the presence or absence of interface coupling, filler loading and thermal exposure. The data show that, at loadings above 5 wt%, elongation is enhanced in the azo-linked composites compared to the composites with bare fillers; modulus is enhanced at low silica loadings (<5wt%) but is reduced at high loadings. On thermal clipping of the coupling agent, we find a slight enhancement of the ultimate elongation, but only at loadings above 5 wt%. We conclude that although interfacial bonding has a positive effect on reinforcement, the influence of physical interactions at the interface overrides that of chemical bonds.
A Note on the Gent Model for Rubber-Like Materials
Authors: Pucci Edvige , Saccomandi Giuseppe
Published: February 2011

We consider the strain energy recently proposed, on a phenomenological basis by Alan Gent to take into account limiting chain extensibility in rubber-like materials. We show that this model gives the simplest rational approximation for the reduced tensile force associated with uniaxial extension that satisfies the usual basic assumptions of continuum mechanics. Then by examination of the classical Treloar data on uniaxial extension of rubber, we explain why the Gent model cannot give good predictions for small and moderate strains. We propose some modifications and find a particular one which is able with a minimum number of phenomenological coefficients to give a very good fit to uniaxial data over the full range of deformations.
Mechanical and Viscoelastic Characterization of Hyperbranched Polyisobutylenes
Authors: Puskas Judit E. , Paulo Christophe , Altstädt Volker
Published: February 2011

Structure-property relationships were investigated in hyperbranched polyisobutylenes, in comparison with commercial linear butyl rubber. The gel-free, soluble hyperbranched polyisobutylenes, synthesized by living carbocationic polymerization, had molecular weights, Mw≈400,000 to 1,000,000 g/mol, molecular weight distributions, MWD ≈1.2 to 2.6, and branching frequencies, BR ≈ 4 to 60. The mechanical and viscoelastic characterization of these polymers revealed interesting properties, including the characteristics of crosslinked rubbers.