bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Silicone Rubbers
Authors: Štefcová Petra , Schatz Miroslav
Published: February 2011

The method of preparation of elastic permanent magnets of silicone rubber is described, and the values of the basic magnetic properties of these rubbers, i.e., the coercive force, the remanent induction, and the maximum energy product, are given.
How to Achieve Quality Polymer Blends by a New Extrusion Technique
Authors: Hindmarch R. S. , Gale G. M.
Published: February 2011

The flow patterns of a striation through a Cavity Transfer Mixer was demonstrated. These were seen to take an optimum path and action to achieve exponential efficiency of mixing. The striation was seen to turn through 90° before being cut in successive segments, deposited in the next cavity row, and drawn out perpendicular to the original direction of shear. The effectiveness of the CTM is a result of the regular turning and cutting action which had been predicted and which has been demonstrated. Factory trials have shown that polymers and masterbatched materials can be blended efficiently in a CTM unit and that off-specification materials can be processed without further reduction in viscosity. Thermoplastic rubbers can be processed on rubber extruders with plain pumping screws fitted with CTM units to blend color or ingredient masterbatch without prior mixing. We would conclude that all the above advantages are secondary to the main advantage of “temperature blending” which the Cavity Transfer Mixer will achieve and which we have reported in our previous paper.
Water Permeation through Elastomer Laminates I. Neoprene/EPDM
Authors: Cassidy Patrick E. , Aminabhavi Tejraj M. , Brunson John C.
Published: February 2011

Two elastomers namely, neoprene and EPDM and their laminates were used to measure the permeation rates of distilled water and salt water at 23°, 40°, and 60°C. For laminates, the rates were measured in both directions. The laminates showed a directional dependence of permeation rate. These rates were lower than the arithmetic mean of the two single layers, but higher than the theoretical calculated values. Effect of temperature on permeation rate had an Arrhenius-type behavior, and the activation energies fall within the range for those membranes that follow activated transport mechanism. Tentative mechanisms were proposed for the directional flow behavior in regard to concentration-dependent permeation.
Gravimetric Analysis for Determining the Resin and Rubber Content of Guayule
Authors: Black L. T. , Hamerstrand G. E. , Nakayama F. S. , Rasnik B. A.
Published: February 2011

The method presented provides a fast and sufficiently accurate method for determining the resin and rubber contents of guayule. Although it does not provide definitive or “absolute” values that presumably can be obtained with sophisticated instrumentation, it is well suited for agronomic developmental studies at the field station level.
Mechanisms of Ozonation of N-(1,3-Dimethylbutyl)-N′-Phenyl-p-Phenylenediamine
Authors: Lattimer R. P. , Hooser E. R. , Layer R. W. , Rhee C. K.
Published: February 2011

The ozonation products of a common rubber antiozonant, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (HPPD), have been separated by liquid chromatography and identified by mass spectrometry. Three principal mechanisms appear to govern the ozonation of HPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. Side-chain oxidation leads to several low molecular weight products, including some that contain an amide moiety. Nitroxide radical formation leads to a nitrone that is the most abundant ozonation product; a dinitrone is also formed. Ozonation of HPPD occurs mainly with degradation of the alkyl portion of the molecule. The results of this study are consistent with a combined “scavenger-protective film” theory of antiozonant protection of rubber compounds.
A Low-Cost, Rapid Method for Determining Carbon Black Surface Area
Authors: Pausch Jerry B. , McKalen Caroline A.
Published: February 2011

For practical use of this method as a quality control procedure for carbon black, a combination of 4 mm3 and 6 mm octane doses appears to be the best compromise for a sample size of 0.1 g. These conditions cover well, a surface area range of 10–140 m2/g and surface areas up to 180 m2/g can be estimated. Larger doses of octane will extend the linear range on the high side, but the slope of the calibration curve is reduced significantly. A smaller slope yields lower precision. The regular testing of standards appears necessary to achieve optimum accuracy of surface area. At the present time, the method is calibrated against nitrogen surface area data, so the advantage of octane more closely simulating the rubber molecule is lost. We need to obtain adsorption isotherms that are better defined throughout the linear adsorption coefficient range for a number of carbon blacks, and thus become self-calibrated against octane. A more versatile dosing technique is preferred to enable these experiments to be run. An alternate approach is to correlate the headspace results with data obtained by other techniques such as CTAB. The advantages of automated headspace gas chromatography for measuring surface area have been outlined before . It is a rapid and simple method, which also exhibits relatively low labor involvement. The number of samples capable of being analyzed per day is significantly higher than by any other technique.
Elastomers in Medicine
Authors: Leeper Harold M. , Wright Rose M.
Published: February 2011

The last review in Rubber Chemistry and Technology of the role of elastomers in medicine was that of Silas Braley in 1971, “Elastomers for Implantation in the Human Body”. The present review focuses on the elastomer/biomedicine interface of the past dozen years, although the need for historical perspective requires inclusion of some earlier references. The technical literature during this period dealing with elastomeric biomaterials has broadened at what might be called an exponentially increasing rate. It becomes quickly apparent in reviewing the recent literature that elastomers have been making profound contributions to both the quality and the extension of human life. It is to some of these applications that this review will be confined. The dozens of less critical, albeit important, medical applications—population control devices, surgeon's gloves, medical tubing, finger cots, etc.—will have to be the subject of another review. Even with this attenuation of focus, only a small fraction of the most serious applications can be discussed. This review is addressed more to the rubber technologist than to the medical community; for this reason, it includes sections on testing, purification, and surface modification of elastomers, as well as the practical issue of the newly developing regulatory aspects of elastomeric medical devices. while this review was in preparation, the first total replacement of a human heart with a permanent artificial one constructed of rubber, metal, and plastic took place on December 2, 1982, at the University of Utah. Although the news media understandably focused attention on the few medical and engineering scientists immediately involved, the technical literature on development of the artificial heart (including left ventricular assist devices) tells the story of the labors of scores of biomedical scientists who made this event possible.
Developments in Extrusion Science and Technology
Authors: Johnson P. S.
Published: February 2011

There have been a number of developments in the design and operation of extruders in the last ten years. The developments to be expected in the next decade will be primarily in the field of process control using the insights gained into compound behavior, processability testing and, especially, microprocessors. Increasing economic pressures will direct these changes. Processors who attempt to ignore these developments will be laboring under a self-imposed disadvantage, relative to their competitors.
Water Permeation through Elastomers and Plastics
Authors: Cassidy Patrick E. , Aminabhavi Tejraj M. , Thompson Corley M.
Published: February 2011

The available data on permeability, diffusivity, and solubility of water and water vapor through elastomers and plastics have been summarized. In many ways, the last five years have been a relatively dormant period, following the previous fifteen years when most theories and experimental data were generated. From a practical and technical viewpoint, knowledge of permeation, diffusion, and solution behavior is essential for the successful design and use of many products, such as packaging films and other protective coatings. This knowledge had an immediate impact on the development of efficient permselective membranes to satisfy the exacting conditions required for use as media for reverse osmosis desalination, artificial kidney and lung components, and for other precise separations of multicomponent penetrant mixtures. The interdependence of polymer structure and transport behavior—a major factor affecting the ultimate properties of films and membranes—is of increasing importance as our ability to control polymer synthesis and characterize polymer structure has become more precise and predictable. It is to be expected that even more dramatic progress in membrane technology will result from the ever quickening pace of research in related areas of science spurred on by the increased awareness of the present and potential importance of membrane phenomena. There are two serious and pandemic problems which plague researchers in the field of transport of water through elastomers and plastics. One of these is that a variety of techniques are used to measure permeability that cannot be compared to one another. The second is that the composition of the membrane is often not reported precisely in the published data.
Short Fiber Reinforced Elastomers
Authors: Goettler L. A. , Shen K. S.
Published: February 2011

A comprehensive review of the journal literature dealing with short-fiber reinforcement of various types of elastomers over the past decade indicates an underutilization of the potential for this type of reinforcing agent within the rubber industry. Whereas the properties of continuous cords are not necessarily duplicated by discontinuous fibers, a unique and useful behavior is imparted by this latter class of reinforcement to the rubber matrices containing them. In many cases, new capabilities are generated for elastomeric materials by the nature of the short fiber composite—it is not just a combination of cords and rubber, but effectively a different compound in which individual dispersed filaments can synergistically interact with the rubber, much like a polyblend or alloy. Moreover, the structure, and hence the properties, of this blend can be manipulated through the processing or fabrication operation, as well as by compounding. Thus, new opportunities are opened for growth and expansion of the classical rubber market.
Macromolecular Engineering by Carbocationic Techniques: New Polymers That Contain Elastomeric Sequences
Authors: Kennedy Joseph P.
Published: February 2011

The aim of this review was to outline some key concepts the macromolecular engineer can utilize in the task of assembling useful polymers. In addition to useful ultimate properties, convenient processing characteristics are also an important consideration. The way toward these objectives is by skillful combination of elementary events—by exploiting the mechanistic understanding of initiation, propagation, and termination processes. Tables V and VI summarize the processes surveyed and outlines the structures of macromolecules that can be synthesized by utilizing carbocationic macromolecular engineering. Table V summarizes the “Undisturbed” Systems i.e., systems in which only the monomer, initiator and coinitiator appear. Table VI shows the “Disturbed” Systems, i.e., systems in which, in addition to the three main species, others, such as proton traps or inifers, also appear. The Undisturbed Systems are further subdivided into Static and Dynamic (or Continuous) Techniques. Static methods use batch operations while dynamic techniques use continuous feeding of monomer(s). The flow of the examples from the top of Table V to the bottom of Table VI is by increasing complexities of the manipulations involved. Thus, the tables start with examples of materials whose synthesis requires only controlled initiation. In other words, controlled initiation alone will give rise to head-functionalized polymers (H = head group) or macromers or gTaft copolymers or bigrafts. for the materials in the second group of Table V, end-functionalized polymers (E = end group) or certain graft copolymers, only termination control is needed. Next, to prepare polymers whose head and end groups are tailor made, the macromolecular engineer has to combine controlled initiation plus termination. The same is true for grafts whose branches carry designed end groups. Combination of controlled termination plus initiation yields diblock copolymers.
Oxidation and Stabilization of Rubbers
Authors: Shelton J. Reid
Published: February 2011

I would like to acknowledge the financial support of our research by the rubber industry, and by U.S. Army Ordnance Research, supplemented by other government agencies and the Petroleum Research Fund, ACS. I also want to emphasize that the honor of t award must be shared with all who have worked with me from the early 1940's to the present time. I will not name them here because there are so many, and I would not want to overlook anyone. I do want to thank my biographer. Professor Jack L. Koenig, who will introduce me this evening, and with whom I continue to collaborate on studies of both oxidation and vulcanization of rubbers. I am very proud to have been a member of the Rubber Division, ACS, since January of 1944, and I am very grateful to the division for choosing me to receive the Charles Goodyear Medal for 1983.
Improved Slip-Resistance on Oil from Surface Roughness of Footwear
Authors: Manning D. P. , Jones C. , Bruce M.
Published: February 2011

This appears 10 be the first published investigation of friction measurements throughout the useful lives of footwear, and the changing patterns of slip-resistance found justify this approach. The polishing effect of walking on some surfaces needs further investigation, and there should now be an evaluation of friction relative to surface texture of soles and heels. It may be possible to engineer a permanent surface roughness by varying composition and size of spaces in a cellular structure. Although it is unlikely that any single material will prove to be satisfactory for all types of floor hazards, our experience with polyurethane is encouraging. If it proves impossible to find a single material giving adequate slip-resistance on wet or icy pavements, wet PVC tiles, ceramic tiles contaminated with grease and water, and factory floors contaminated with oil, then materials should be specified for each type of hazard.
Studies of Polymer-Filler Interaction, Network Structure, Physical Properties, and Fracture of Silica-and Clay-Filled EPDM Rubber in the Presence of a Silane Coupling Agent
Authors: Pal P. K. , De S. K.
Published: February 2011

1. A silane coupling agent (Si-69) reduces the viscosity and increases the scorch lime in silica- and clay-filled EPDM. The cure lime of silica-filled mixes remained unchanged and that of clay-filled mixes increased on addition of Si-69. 2. In the presence of Si-69, the silica-EPDM system exhibits higher polymer-filler interaction than the clay-EPDM system. 3. Vulcanizates containing Si-69 exhibit higher apparent crosslink density and a higher proportion of polysulfidic crosslinks than the control vulcanizates. 4. Vulcanizates containing Si-69 show improved physical properties. Lower tensile and tear properties in vulcanizates with Si-69 at higher filler loadings is explained via a slippage mechanism. 5. SEM studies of fractured surfaces created under tension, tear, flexing, and abrasion have been made, and changes in the strength of the vulcanizates have been correlated with the fractographs.
A New Look at Direct Compound Analysis Using Pyrolysis Mass Spectrometry
Authors: Pausch Jerry B. , Lattimer Robert P. , Meuzklaar Henk L. C.
Published: February 2011

For direct compound analysis, pyrolysis mass spectrometry offers renewed hope that the time-consuming and costly separations currently required can be bypassed, at least in part. Polymer blends and copolymers are readily identified along with certain additives. The ability to achieve this information quickly from a single experiment is a valuable improvement. However, more work needs to be done to identify curatives, oils, and higher molecular weight rubber chemicals in compounds. For example, the mass range scanned needs to be expanded to detect higher molecular ions. Temperature-programmed Py-MS may prove useful in separating the more volatile components (nonpolymeric oils and organic additives) for easier detection. Future work will also assess the quantitative potential of the technique. The success with experiments on CPVC materials using pattern recognition techniques opens up a new dimension for compound analysis. Besides being able to determine composition, selected information about reaction mechanisms, morphology, physical properties, or other important parameters may now be possible.
The Identification of Rubber Compounding Ingredients by Using Thin Layer Chromatography
Authors: Gedeon B. J. , Chu T. , Copeland S.
Published: February 2011

TLC is a quick, easy method to the identification of rubber compounding ingredients. Both silica gel absorbent and C18 absorbent are suitable for these identifications. With the mobile phases used in this study, a better separation of antioxidants is possible using silica gel absorbent. Work should be continued on finding suitable mobile phases for the C18 absorbent, since the Rf values are more reproducible. For those separations that require a separation of compounds of varying molecular weight, the C18 absorbent is superior to silica gel absorbent. The visualization systems that have been developed for use with silica gel absorbent are suitable for use with C18 absorbent. These systems give the same colors for either absorbent.
Magic Angle Spinning 13C NMR Studies of Filled Vulcanizates
Authors: Komoroski Richard A.
Published: February 2011

Magic angle spinning (MAS) 13C NMR is investigated as an alternative method to IR spectroscopy of solution state NMR for the characterization of the elastomeric conmponents of filled vulcanizates. Good high resolution spectra can be obtained from standard. Bloch decays (i.e., without cross polarization) using magic angle spinning and high power decoupling. Although the peak resolution is not as good as in 13C spectra of comparable solubilized or pyrolyzed materials, the MAS spectra are of sufficient quality for polymer identification in simple filled vulcanizates in most cases. The MAS spectra are usable for direct quantitative analysis of the polymeric components without priot sample workup. A known series of filled cis-BR/SBR vulcanizates ranging from 0 to 100% SBR was examined. Direct analysis yielded results with an average absolute deviation of 1.2% from the expected values. A known series of NR cis-BR-SBR compounds which had been characterized previously by IR was also studied. The direct NMR analysts gave results comparable to those of the IR method. Use of a cis-BR/SBR standard curve derived from the previous cis-BR/SBR analysis improved the results for the triblend analyses. The MAS 13C NMR method has the advantage that a potentially suspect solubilization or pyrolysis step is eliminated. In many cases, results can be obtained in several hours. Also, results should not depend on degree of cure. The NR cis-BR/SBR results show that low levels of NR (∼3 to 5%) are detectable.
Colloidal Structure-Property Relationships in Carboxylated Styrene-Butadiene Latexes
Authors: Chatterjee A. K.
Published: February 2011

1. The hydrodynamic particle size of the latexes, measured by light transmission and liquid exclusion chromatography, was, in general, higher than the dry particle size measured by electron microscopy. At comparable high pH and acid level, a methacrylic latex swelled more than an itaconic latex, indicating difference in acid incorporation. 2. Carboxylic acid incorporation in batch-polymerized SB latexes containing itaconic and/or methacrylic acid was strongly influenced by the level and relative ratio of the two acid monomers in the recipe. Itaconic acid distributed primarily between the surface and the serum and none in the bulk polymer. Methacrylic acid distributed primarily between the surface and the bulk of the polymer and none in the serum. The acid distribution results can, in general, be understood in terms of the relative solubilities of the acid monomers in water and styrene. 3. It appeared that the percentage of the total acid bound to the surface could be maximized by the use of certain combinations of the two acid monomers rather than the sole usage of either acid monomer. 4. The latexes contained two kinds of surface-bound acid that differed slightly in ionization characteristics. In general, a direct relationship existed between the H+ ion stability and the ratio of type I to type II surface-bound acid concentration. Thus, the itaconic latex was the least H+ ion stable, while the methacrylic latex was the most H+ ion stable among the latexes. It is not clear at this point as to how exactly the two acid types are located on the particles. 5. The colloidal stability of a carboxylated latex depended on the type of cation, the amount of surface-bound acid and the extent of ionization. Both CCC and electrophoresis results showed that sodium chloride stability increased with the increase of surface-bound acid and pH of the latex. The calcium chloride stability, however, decreased with the increase of pH, indicating strong specific interaction between calcium and carboxylate ions. The interaction of a carboxylated latex with hydrogen, sodium, and calcium ions seemed to take place, respectively, through alteration of the surface acid dissociation equilibrium, reduction of the double layer potential, and surface charge reduction by chemical bonding.
Effect of Zinc Dithiocarbamates on NR Vulcanization Accelerated by Thiocarbamyl Sulfenamides and Dibenzothiazyl Disulfide
Authors: Datta Rabindra Nath , Basu Dipak Kumar
Published: February 2011

The hplc studies with all their limitations have been employed to obtain information regarding the vulcanization of rubber accelerated by CTOS and MBTS in the early part of the reaction. It is noticed that even in the initial part of the induction period (the scorch safety, t2, of the recipe is 10.5 min), CTOS and MBTS react so rapidly with each other and also with rubber that at the end of 10 min we could detect only MBT, while the concentration of the other components formed in the reaction—namely, CTOS, OBTS, CPTD, BPTD, PMTU, CPTM, BPTM, etc.—decreased to an extremely low level. We noticed that under the experimental conditions, OBTS and CPTU have the same retention time. This naturally obscures the path for understanding the individual effect of these accelerators. The sharp disappearance of OBTS, associated with the abundant formation of MBT and nonavailability of CPTU (from CPTD, Figure 11b), gives testimony to the fact that the unsymmetrical thiourea (PMTU) rather than the symmetrical one (CPTU) is solely formed in the vulcanizates under discussion. The accelerating as well as retarding effect of thiourea has been reported by Dućhac^ek in the vulcanization of NR. Substituted thiourea, namely, bis(oxydiethylene) thiourea, has also been shown to influence the vulcanization of SBR in the presence of a mixture of accelerators formed by the early reaction of OTOS and OBTS. The influence of PMTU, however, remains to be investigated, and studies in this line are being pursued. Also, we could not isolate the effect of MDB from that of CPTD, since both of them have the same retention time. From our experience, we know that in comparison with CPTD, the proportion of MDB formed under the experimental conditions is very low and, hence, it is believed that CPTD plays the major role. It has also been observed that BPTD rapidly transforms into BPTM which, as noticed by us, also influences vulcanization. It is concluded that in the binary system containing CTOS and MBTS, the intermediate accelerators, OBTS, CPTD, and BPTD play a vital role, and their growth and decay, either in the presence or absence of the ZDC, control the fate of the vulcanization reaction.
Natural Higher Fatty Acid Soaps in Natural Rubber Latex Concentrate and Correlations to Other Latex Variables
Authors: Jurado C. W. , Mayhan K. G.
Published: February 2011

The amounts and types of HFA soaps found in latex did not vary greatly from sample to sample. Greater than 95% of the free HFA soaps were associated with the rubber phase of the latex. The distribution of fatty acid soaps were markedly different in the serum and latex samples. About 80–90% of the HFA soaps are in their free form, but only about 50% of the furanoic acid was in its free form. Titration results agree fairly well with the GC results and indicate that titration can be a useful measure of HFA.
A Simple and Rapid Method for Determination of Guayule Rubber
Authors: Grinberg Sarina , Shaubi Eleonora
Published: February 2011

An improved turbidimetric analytical method for guayule rubber was developed. The method is simpler and faster than previously developed turbidimetric methods, and enables the use of commercial solutions of the rubber. Unlike Traub and Perry, who used diisobutyl ketone for extraction of guayule rubber for turbidimetric measurements, we used hexane, which did not extract aromatic compounds along with the rubber, thus giving the best yield of spectrally clean rubber. Propanol is our precipitant of choice for turbidimetric assay of rubber, since it is also good as a colloid-protection agent.
Mechanisms of Antiozonant Protection: Unextractable Nitrogen in Aged Cis-Polybutadiene Vulcanizates
Authors: Lattimer R. P. , Gianelos J. , Diem H. E. , Layer R. W. , Rhee C. K.
Published: February 2011

Rubber (BR) vulcanizates containing DOPPD antiozonant and DPG accelerator have been aged under various conditions, and the soluble constituents have been removed by acetone extraction. Small amounts of nitrogen become bound to the rubber network as a result of side reactions associated with vulcanization. Additional nitrogen becomes bound to the rubber during aging. The bound nitrogen level is greater in (a) dynamic as compared to static testing, and (b) an ozone atmosphere as compared to air or nitrogen. We believe that the principal reason for nitrogen becoming bound during aging is the trapping of macroalkyl radicals by aromatic amine-derived species (e.g., nitrones). The results of this work are consistent with previous studies in our laboratory that indicate a combined “scavenger-protective film” mechanism is principally responsible for antiozonant protection. We believe it is unnecessary to invoke reactions involving antiozonant and ozonized rubber to explain the results of “unextractable nitrogen” experiments.
High-Temperature Curing of Radial Passenger Tires
Authors: Walker Lloyd A. , Helt William F.
Published: February 2011

High temperature curing is feasible with adequate curative modifications. NR-containing compounds are prime considerations. Cure time reductions of about 35% or more are entirely within reason. Use of the modified compounds at conventional or low curing temperatures makes possible significant improvements in performance.
Inflation Characteristics of Unvulcanized Gum and Compounded Rubber Sheets
Authors: Kong Dancheng , White James L.
Published: February 2011

The inflation of rubber compound membranes to fill molds has a long history in rubber processing. There have, however, been few basic experimental studies of this topic. This free inflation of vulcanized rubber sheets was studied by Treloar and Rivlin and Saunders during the 1940's and 50's where it was used to investigate the form of the stress-strain relationship. Rivlin and Saunders sought to fit nonlinear elastic constitutive equations to data obtained at small inflation levels. In the early 1970's Denson and his coworkers utilized the inflation of unvulcanized polyisobutylene membranes to apply this as a procedure to evaluate biaxial and planar extensional viscosities. Similar studies were made by Maerker and Schowalter. These studies all involve free inflation of membranes. These studies of inflation of raw gum polyisobutylene sheets only looked at relatively small deformation levels where a hemispherical shape or less was achieved. Failure mechanisms in similarly inflated vulcanized SBR 1502 rubber sheets were described by Dickie and Smith. These authors did not describe the shapes of the inflated sheets. There seem to be no studies of inflation of rubber membranes into molds or useful equivalent studies of molten plastics such as thermoforming. It is the purpose of this paper to present a basic study of the inflation of membranes of various gum and compounded elastomers. We observe the manner in which the membranes freely inflate into air and also the manner in which they fill molds of various shapes. We begin with qualitative considerations but will also present quantitative measurements. Biaxial elongational viscosities have been estimated.
Characterization of Elastomers and Rubber Chemicals by Modern NMR Techniques
Authors: Komoroski R. A. , Shockcor J. P. , Gregg E. C. , Savoca J. L.
Published: February 2011

High resolution NMR has undergone a revolution in the last ten years or so. The ability to manipulate spin systems to a high degree in the pulse FT NMR experiment, coupled with advances in NMR computing systems, has led to the design of many multipulse and two-dimensional (2-D) NMR experiments which can provide considerably more information than a standard spectrum. In addition, experiments to obtain high resolution NMR spectra of solid materials have opened a whole area of chemistry to NMR. The new interpretive techniques for spectra obtained in solution have been applied to synthetic polymers or polymer chemicals only recently. However, the solid-state methods already have seen wide application in the polymer area. In this report, we describe some work from our laboratory employing some of these advanced methods in both solution and the solid state. This is not meant to serve as a detailed discussion of the techniques employed, but rather as an introduction to potential applications in the rubber and polymer industries.
Recent Advances in the Phenomenological Theory of Rubber Elasticity
Authors: Ogden R. W.
Published: February 2011

We have shown that representations for the strain-energy function in terms of the stretches λ1, λ1, λ1, with particular reference to the Valanis-Landel hypothesis, provide a very good correspondence between theoretical stress-deformation relations and existing experimental data for a variety of different deformations of rubberlike materials. The stress-deformation relations themselves have a simple structure which makes for clear interpretation of the experimental results. As was emphasized in Section II.B., however, more data from biaxial tests on rubberlike materials of varying constitution are needed to support those already available. Also, further data from a variety of different experiments in which inhomogeneous deformations occur would be valuable. Finally, with reference to the effects of compressibility, data relating to volume changes—possibly from biaxial tests in the presence of hydrostatic pressure—would enable a more systematic approach to the construction of strain-energy functions for compressible materials to be pursued.
Ultimate Tensile Properties of Segmented Polyurethane Elastomers: Factors Leading to Reduced Properties for Polyurethanes Based on Nonpolar Soft Segments
Authors: Speckhard T. A. , Cooper S. L.
Published: February 2011

Factors that could explain the lower tensile properties of nonpolar soft-segment-based polyurethane block copolymers relative to those of conventional polyether or polyester polyurethanes have been examined. Many of the materials studied in the literature have suffered from the use of soft segments with poor functionality, which has led to low molecular weight, network defects, and an unfavorable amount of crosslinking. Additionally, most of the materials have been based on soft segments whose molecular weight appears to be too high to obtain optimum properties. Polyurethanes based on nonpolar soft segments are also likely to suffer from premature phase separation during polymerization leading to low molecular weight and compositional heterogeneity, especially if the reaction is done in bulk. The lower soft-segment glass-transition temperature of, in particular, the polydimethylsiloxane polyurethanes can also contribute to their lower tensile properties at room temperature. However, if differences in the soft-segment glass-transition temperatures are accounted for by comparing samples at equivalent values of T−Tg and other parameters are optimized, it appears that only a lack of soft-segment crystallizability under strain and possibly an excessively high degree of phase separation are inherently limiting the tensile properties of nonpolar soft-segment-based polyurethane block copolymers. The limited amount of available information concerning the effects of many of these factors suggests a need for additional work in this area.
Electrical Conduction in Carbon Black Composites
Authors: Medalia Avrom I.
Published: February 2011

Electrical conductivity is important in many rubber and plastic compounds including antistatic applications, wire and cable sheathing, and shielding against electromagnetic interference (EMI). Elastomers and plastics are insulators (dielectrics) to which conductivity is imparted by addition of a finely divided or colloidal filler of high intrinsic conductivity, such as carbon black. Over the years, there has developed a sizable body of information regarding measurement of conductivity, and the factors which affect it in such compounds or composites. With regard to the physical processes involved in the conduction of electricity, various mechanisms have been proposed by various authors. It appears that many physical processes can be involved and that the dominant process depends upon the composition of the composite and the conditions of measurement. The purpose of this review is to survey the proposed mechanisms of conduction in composites of carbon black and nonconductive polymers, taking special note of recent theoretical advances, and to examine the effects of the properties of the carbon black and the composition of the composite.
Application of Electron Beam Radiation Technology in Tire Manufacturing
Authors: Mohammed S. A. H. , Walker J.
Published: February 2011

Electron beam radiation is used in various industries for a number of reasons. In the rubber industry it is used primarily for its ability to crosslink certain polymers and thereby to provide either “green strength,” by causing partial vulcanization (precuring), or “elastomeric properties,” by fully vulcanizing (curing). Although the latter function has potential importance, the precuring function has more practical application at this stage in the development of the technology and is particularly valuable in the radial tire building process. The electron beam vulcanization, or precuring of rubber products, is usually accomplished continuously, on-line, at high throughput rates, following extrusion or calendering operations. This paper reviews the chemistry involved, the response of polymers, and the effects of compounding for electron beam radiation processes. The type of equipment used in the tire industry, the process variables, and the methods used to measure the energy input into compounds exposed to radiation are also described. As an example of the utility of this process, electron beam radiation of halo-butyl inner liners used in radial ply tires is discussed.
Carbon Black Treadwear Ratings from Laboratory Tests
Authors: Dannenberg E. M.
Published: February 2011

It has been seen from the above survey that a few of the treadwear predictor correlations have the required accuracy to provide a satisfactory alternative to road testing of tires for the wear performance of carbon blacks, depending on requirements and circumstances. Correlations based on laboratory rubber testing of rubber mixes and tread compounds are to be preferred over those based solely on carbon black colloidal and morphological measurements. In the author's opinion, Cotten and Dannenberg's correlation of treadwear index with Angle Abrasion measurements of 30 phr compounds and heated bound rubber, and Westlinning and Wolff's correlation with rebound resilience, and the Monsanto Rheometer determination of αF are satisfactory in most instances for the prediction of the treadwear index behavior of carbon blacks.
New High-Temperature Thermoplastic Elastomers
Authors: Chen Augustin T. , Nelb Robert G. , Onder Kemal
Published: February 2011

The unique reaction of carboxylic acids with isocyanates has made it possible to incorporate polyamide into some new thermoplastic elastomers such as PEA and PEEA. With these high melting, semicrystalline, hard segments, these elastomers have excellent thermal properties and higher application temperature ranges. Because of their easy processability, these polymers can be injection molded or extruded for a great variety of applications with conventional equipment.
Experimental Study of the Flow Characteristics of Rubber Compounds in Extruder Screws
Authors: Brzoskowski Ryszard , White James L. , Weissert Frederick C. , Nakajima Nobuyuki , Min Kyonsuku
Published: February 2011

The application of screw extrusion to rubber compounds probably dates back over a century. Rubber extrusion has been an area of industrial importance throughout this period. Technological innovation continues in this area, as may be seen in a recent review by Johnson. However, there have been only a few basic studies on the flow characteristics of rubber screw extruders. Many more extensive investigations on the working of plastics screw extruders have been carried out. The latter researches are summarized in the volumes by Tadmor and Klein and Tadmor and Gogos. The basic mechanisms of flow of plastics in screw extruders were first revealed in experimental studies by Maddock. He fed the screw with pigmented pellets, pulled it from the barrel with the plastic strips in it, which were then unwound and cross-sectioned. There seem to be few such similar published investigations for rubber compounds. We are only familiar with the work of Menges and Lehnen. It is our purpose in the present paper to initiate a fundamental study of flow mechanisms in rubber screw extruders. We will proceed by carrying out the Maddock procedure but with rubber strips containing markers, then vulcanize the rubber compounds in place, and pull out the screws. The placement of the rubber will be noted, and the rubber sections will be examined for their flow patterns. The paper extends our earlier marker experiments on flow of rubber compounds through dies.
Newtonian Simulation and Dimensional Control of the Single Roller Die Extrusion Line
Authors: Stevenson J. F.
Published: February 2011

A single roller die consists of a fixed plate die bounded on one edge by a rotating cylinder. Material is forced through the die by a combination of pressure flow from an extruder and drag flow by the roller. Extrusion lines for tire components have traditionally been controlled by manipulating the size (cross-sectional area) of the extrudate through adjustments of the line speed relative to the screw speeds for cold-feed extruders or feed-strip widths and/or mill speeds for hot-feed extruders. Intentional changes in shape (ratios of dimensions normalized for size change) required altering the die geometry. Sources of variation in size and shape during extrusion include transients during start up, property changes within and between batches, short-term cycling of output rate, temperature cycling and drift, and inadequate control of independent variables such as screw and line speeds. The objective of this paper is to demonstrate how a single roller die line can be used to control independently two categories of dimensions (e.g., thicknesses and widths). This independent control necessarily requires that at least two other variables be manipulated, in this case, screw speed and roller die speed.
On the Role of Nonlinearity in the Dynamic Behavior of Rubber Components
Authors: Harris J. , Stevenson A.
Published: February 2011

This paper has discussed the transmissibility behavior of rubber mounts with reference to nonlinearity originating from the material composition and from the geometrical design. It has been shown that in many cases, linear assumptions can be made, provided the limitations of these assumptions are understood. In this case, design can proceed as for a linear spring. Finally, there is some indication of how the nonlinear behavior can be exploited to advantage in the design of novel suspension components.
Buckling and Postbuckling of Elastomeric Components: Tactile Feel in Electric Switches
Authors: Padovan Joe , Schrader Mark , Parris Joel
Published: February 2011

Within the range of the parameters of the switch designs considered, only very slight cocking of the switch structure occurred. Thus, with minimal off-axis cocking, the axisymmetric assumption remained valid, resulting in a considerable finite-element economization when compared to a full three dimensional model. Some switch designs encounter localization problems, such as surface folding and stiffness mismatches. Mesh refinement is not a general panacea for these localization problems. Regardless, a fold of this type or stiffness mismatch is generally indicative of a potentially poor switch design, with the possibility of associated fatigue problems. For the switch designs considered, the peak strains were found to be less than 70 percent; thus the Mooney-Rivlin and Ogden material models yielded essentially similar results. Furthermore, a Hookean material model may be adequate for some purposes, because the tactile-feel response was found to be dominated more by switch geometry than anything else. Overall, we have seen that combining FE analysis together with the full continuum-constitutive-boundary formulation can successfully address the problem of buckling and postbuckling of elastomeric structures. In the case of switches, such behavior is an intrinsic property. This is an interesting contrast with traditional structures.
Thermo-Oxidative Degradation of Thick-Walled Rubber Materials Studied by IR-Technique and Computed X-Ray Tomography Scanning
Authors: Mattson Bengt , Stenberg Bengt , Persson Sture , Östman Erik
Published: February 2011

Natural rubber cylinders vulcanized with two different systems, TMTD, which is an efficient vulcanizing system (EV system) and S/CBS, which is a conventional system, have been studied with respect to thermo-oxidative aging gradients, by the ATR-IR-technique (attenuated total-reflection infrared spectroscopy), computed x-ray tomography scanning and swelling. Observed aging processes are dominated by the formation of an oxidized layer whose low permeability to oxygen protects the interior of the material from oxidative aging processes as long as it is intact. The time to the formation of the oxidized layer is the major reason for the differences in the aging gradients. The oxidized layer is formed rapidly in the conventional system, whereas the formation is inhibited by dithiocarbamates in the EV system. Oxygen therefore diffuses into the EV materials, giving deeper oxidative aging than in the conventional materials at the same temperature. The conclusion drawn from the results of this study is that an earlier formation of an oxidized layer is advantageous with respect to thermo-oxidative aging of the bulk. Although it must be stated that, due to the better thermal stability of an EV system and to the poor mechanical properties of an oxidized layer, no objection is here raised to the accepted view that an EV system has superior aging properties.
Characterization of Fillers in Vulcanizates According to the Einstein-Guth-Gold Equation
Authors: Wolff Siegfried , Donnet Jean-Baptiste
Published: February 2011

1. Up to now, the application of the Einstein-Guth-Gold equation seemed to be limited to inactive fillers. 2. However, in the form of Equation (6), it describes with high accuracy the moduli of vulcanizates containing active fillers as a function of the filler volume fraction at least up to ϕ=0.22 at uniaxial elongations and for any given value of λ. 3. The effectiveness factor ƒ is independent of crosslinking density, but is dependent on deformation, temperature, and the surface activity of the filler. 4. If ƒ as a function of elongation is known, the respective stress-strain curves of filled networks can be calculated in advance for any given crosslinking density. 5. The interpretation of the effectiveness factor will require further investigations, especially with regard to the influence of the structure and surface activity of the filler.
Mechanical Properties, Structure, and Morphology of Natural-Rubber/Low-Density Polyethylene Blends Prepared by Different Processing Methods
Authors: Qin Chuan , Yin Jinghua , Huang Baotong
Published: February 2011

Morphological studies with TEM and SEM showed that, in unvulcanized NR/LDPE blends, phase inversion occurred between NR/LDPE = 40/60 to 60/40; for dynamically vulcanized blends, LDPE remained as a continuous phase even at NR/LDPE = 70/30. Change in morphology of dynamically vulcanized blends of specified composition (NR/LDPE = 70/30) with vulcanization time as observed by SEM indicated that phase inversion occurred with the progress of vulcanization followed by fracture of the crosslinked phase into small particles. A model was proposed. For unvulcanized samples, the tensile strength steadily increased with increasing LDPE content, while their elongation at break first decreased and thereafter increased. Tensile strength and elongation at break of the statically vulcanized samples decreased to a minimum and thereafter increased with increasing LDPE content. However, an interesting trend appeared in the change in tensile strength and elongation at. break of the dynamically vulcanized system with increasing LDPE, where they first increased to a maximum and thereafter decreased. From the suggested model and the experimental results, it was shown that the mechanical properties of dynamically vulcanized blends were higher than those of unvulcanized blends but lower than those of statically vulcanized blends. The other physical properties of blends which are mainly dependent on the properties of the plastic phase, such as tear strength, 300% modulus, hardness and permanent set, all increased with increasing LDPE in different processing methods. In addition, changes in the mechanical properties of different compositions with the progress of dynamic vulcanization were also examined.