bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence Structure of Styrene-Butadiene Copolymer Determined by Ozonolysis-HPLC Method
Authors: Tanaka Yasuyuki , Nakafutami Yasunobu , Kashiwazaki Yasushi , Adachi Junichi , Tadokoro Kaoru
Published: February 2011

The configurational sequence of styrene units and the arrangement of styrene and 1,2-butadiene units in styrene-butadiene copolymers were characterized by 1H- and 13C-NMR analysis of the ozonolysis products which were separated by a combination of GPC and HPLC. The ozonolysis products from diad and triad styrene sequences flanked by 1,4-butadiene units showed two and three peaks in HPLC, respectively, reflecting the diad and triad tacticity. The probability of racemic addition was found to be 0.56 and 0.58 for radical and anionic SBR, respectively. The ozonolysis products from styrene-1,2 sequences were separated into three fractions by HPLC. The first and second fractions were assigned to a 1,4-1,2 styrene-1,4 (VS) structure differed only in cotacticity. The third fraction was considered to be a mixture of the meso and racemic forms of the l,4-styrene-l,2-l,4 (SV) sequence. The GPC fraction corresponding to a sequence consisting of two styrenes and one 1,2 units was separated into four peaks by HPLC. Both large peaks contained SSV + VSS structures, where one peak consisted of meso configurations with respect to the two styrene units, and the second peak contained racemic styrene alignments. The two small peaks were SVS with the separation due to cotacticity. Based on the intensity of HPLC peaks, it was deduced that the addition of a 1,2 unit after the styrene terminal predominated the addition of a styrene unit after the 1,2 terminal.
Melting Temperatures as a Function of the Strain of Oriented Polymer Networks
Authors: Göritz D. , Grassler R.
Published: February 2011

The reduction in conformational entropy on stretching elastomers causes an increase in melting point of the temperature-induced crystallisation. The dependence of the melting point on degree of deformation is relatively weak. The high melting points of the strain-induced crystallites must be caused by regions whose orientation is markedly higher than that which corresponds to the macroscopic strain. Such a bimodal orientation distribution is explained by an inhomogeneous deformation of the rubber. There exist either regions in the specimen which do not participate in the deformation or regions with very low strength. Stretching leads to an affine deformation of a part of the specimen. If one lets this crystallize, temperature-induced crystallites find themselves in surroundings whose orientation is describable with the assumption of a Gaussian network. Correspondingly, the increase in melting point as a function of strain can be calculated with the aid of the statistical theory of entropy elasticity, in the way Roe and Krigbaum did. The other, essentially smaller part of the sample contains the inhomogeneities. They cause locally highly oriented fibrillar-like regions which lie in the deformation direction. The strain-induced crystallites are formed within these regions of exceptionally low entropy. The simultaneous existence of temperature- and strain-induced crystallisation is interpreted as evidence for inhomogeneous deformation in elastomers.
An Empirical Model for the Design of Rubber Shear Bushings
Authors: Petek N. K. , Kicher T. P.
Published: February 2011

The objective here was to formulate guidelines for the design of a particular class of rubber bushings exhibiting nonlinear load/deflection behavior. This was accomplished by the derivation of an empirical model of bushing performance based on data from a designed experiment. The data from a two-level, full factorial experiment with six design variables were reduced to equations for the prediction of ten response variables. The range of applicability of the prediction equations was extended with an effective dimensional analysis, validating similarity relationships of the system's variables. Thus, an empirical model useful for the first approximation of rubber shear bushing design is established. Further details regarding this model are contained in Reference 3. The nonlinear load/deflection characteristics of rubber shear bushings offer a designer several unique features to utilize advantageously. The plateau region near the center of their stroke provide bushings with low stiffness in their operating range. Unlike linear springs, nonlinear bushings can achieve their load carrying requirement for the operating range while maintaining compact package size. Although similar to Belleville washers in that geometric parameters can be varied to tailor the load/deflection behavior, rubber bushings offer an additional design variable by virtue of their material. The stiffness and damping properties of rubber compounds are readily modified to attain a desired bushing performance.
Determination of PVC in Presence of Reactive Fillers
Authors: Walter S. E.
Published: February 2011

PVC content in thermoplastic materials can be determined from the total chlorine or more specifically from organic chlorine content. Organic chlorine content can be determined by ASTM D 1551 using the described modifications. Presence of reactive fillers such as CaCO3 results in large negative errors. When reactive fillers are expected to be present, the quantity of PVC should be determined with methods measuring total chlorine or by TGA. TGA can be used successfully for the analysis of such samples. Plasticizers and PVC stabilizers are extracted before analysis to eliminate interfering or variable mass loss in PVC thermograms. This technique can also be used for the analysis of PVC/NBR mixtures. In unknown compounds, the technique should be used in conjunction with FTIR analysis to facilitate polymer identification and to rule out interference by other halogenated polymers. Excess of unreacted CaCO3 can be observed and the amount determined from thermograms. Remaining CaCO3 can be determined from mass loss due to elimination of CO2. If a cooling step is introduced before the atmosphere is switched from nitrogen to air, a clearer separation of residue oxidation and CO2 elimination are obtained. On reheating, residue oxidation then takes place between 450 and 500°C, well separated from CO2 elimination at about 700°C. Variation of thermograms using PVC obtained by different polymerization procedures needs to be further investigated. Structural differences and thermal stability of PVC samples made by emulsion, suspension, and bulk polymerization have been examined by various techniques, but no thermogravimetric data are given.
Pressure-Sensitive Adhesion of Isopropyl-Azodicarboxylate-Modified Polybutadiene to Glass
Authors: Chen J. C. , Hamed G. R.
Published: February 2011

The pressure-sensitive adhesion (i.e., adhesive tack) of isopropyl azodicarboxylate modified polybutadiene contacted with glass has been studied using a 180°-peel geometry. Fracture energies were studied as a function of IAD content, contact time, and peeling rate. Additionally, the creep compliance J was measured and related to the peeling response. At low levels of modification, J decreases with increasing IAD content; however, J increases at intermediate IAD levels—indicative of softening in the material. This is thought to be due, at least in part, to a reduction in the entanglement density and is a condition that favors wetting. For example, the elastomer with 33% IAD achieves 46% of its equilibrium bond strength to glass after 2 min of contact while, after the same tc, IAD-29 (with its lower compliance) attains only 26% of its ultimate bond strength. In some circumstances, there is an interesting decrease in the fracture energy as contact time is increased. This is accompanied by a change in the locus of failure from Ig to Im. When failure is Im, the adhesive layer remains flat during peeling and hence, no energy is expended to bend this layer; this results in a lowering of the fracture energy.
Modelling of Shear Viscosity Behavior and Extrusion through Dies for Rubber Compounds
Authors: White James L. , Wang Yeh , Isayev Avraam I. , Nakajima Nobuyuki , Weissert Frederick C. , Min Kyonsuku
Published: February 2011

This paper marks a first effort to develop a fundamental basis for die flow analysis and design for rubber compounds. We have accomplished a modelling of the shear viscosity function and its application to one- and two-dimensional shearing in die cross sections. There are major limitations in what we have done, much of which is apparent even in the early work of Mooney. In particular, we have not considered (i) slip phenomena on die walls, (ii) die entrance and exit pressure losses associated with converging and diverging dies, nor (iii) extrudate swell. We have an active research in our laboratories investigating these problems. In the future, we are seeking to generalize the procedures described in this paper to more complex die designs. Inclusion of entrance and exit effects and rigorous analysis of coathanger dies requires the handling of elongational flow contributions, a still unsolved problem.
Recent Advances in the Molecular Aspects of Polymer Viscoelasticity
Authors: Pearson Dale S.
Published: February 2011

Polymers are materials worthy of study both because of their unique properties and because of their common occurrence in industrial products and in biological systems. The attention focused on them has been rewarded by an increased amount of success in establishing the relationships between their complex physical properties and their molecular structure. This article is concerned with a particular aspect of these investigations, the Theological properties of polymers in the liquid state. There has been an increase of activity in this field during the last fifteen years, which is the period covered by this review. The interested reader is directed to earlier reviews and articles that discuss related subject material. We begin with a qualitative description of a rheological experiment which demonstrates the mechanical response of polymers as well as introduces some of the essential phenomena which need to be explained. When a small shearing force is applied to a high-molecular-weight polymer liquid, it deforms rapidly. At first, the material acts like a rubbery solid and, if the stress is quickly removed, it essentially recovers its original shape. The constant relating the applied stress, σ, and the initial deformation or strain, γ, is the elastic modulus, GN, often referred to as the plateau modulus.
Quantitative Surface FT—IR Spectroscopic Analysis of Polymers
Authors: Ishida Hatsuo
Published: February 2011

This paper is a review of modern Fourier transform infrared (FT-IR) spectroscopic analysis of surface species. Emphasis is placed on the quantitative nature of various surface analytical techniques. In each section, a brief description of theory precedes the application examples, in particular for the surface analysis of polymeric materials. Results obtained by dispersive instruments or for nonpolymeric materials are also given whenever appropriate. This review is intended for a beginner to appreciate the state-of-the-art surface quantitative FT-IR techniques and for one more experienced is a convenient collection of introductory theory and experimental examples which serve as a reminder whenever they are needed.
Dynamic Mechanical Properties of NR-HDPE Blends
Authors: Akhtar S. , Bhagawan S. S.
Published: February 2011

Dynamic mechanical properties such as storage modulus, loss modulus, and loss tangent have been evaluated over a wide range of temperatures for thermoplastic elastomers prepared from blends of NR and HDPE. It was observed that above room temperature, both storage and loss moduli increased and loss tangent decreased as the HDPE content in the blend increased. The effects of dynamic crosslinking and carbon black filler on dynamic mechanical behavior of 70/30 NR/HDPE blend were also examined. Carbon black increased the storage and loss moduli but lowered and broadened the tan δ peak. On the other hand, crosslinking increased storage modulus and decreased the loss modulus and loss tangent, particularly after the NR Tg. The tan δ peak area which appeared at Tg for NR was proportional to the rubber content in the blends.
Determination of the Structure of Chlorobutyl and Bromobutyl Rubber by NMR Spectroscopy
Authors: Chu Chia Yeh , Watson Kenneth Norman , Vukov Rastko
Published: February 2011

An analysis of the 1H and 13C NMR spectra of the chlorobutyl and bromobutyl rubbers was performed. Peaks were assigned based on evidence from broad-band decoupled, off-resonance decoupled, selectively decoupled and J-modulated spectra, the known characterization of butyl rubber and halogenation studies on model compounds. The assignment of the minor peaks indicated that the exomethylene-type structure is predominant in both halogenated rubbers. They also contain some nonhalogenated isoprenyl units. Bromobutyl rubber also contains some α-bromomethyl-type structures resulting from rearrangement of the exomethylene structure. The presence of endo-type structures will require further study for confirmation.
A Vibrational Spectroscopic Analysis of the Structure of Natural Rubber
Authors: Lu F. J. , Hsu S. L.
Published: February 2011

It is not an overstatement to say that natural rubber (NR) is one of the most used polymers. There are numerous studies dealing with the structural aspects of rubber which give rise to its elastic property. However, it should be emphasized that the majority of these studies are generally concerned with rubber in the vulcanized state or, in fact, dealing with the vulcanization process. Relatively few studies have actually been directed at a better understanding of the composition, structure, and properties of raw rubber. This area of study is also important because the composition and the structure of NR differ from synthetic polyisoprene in that the presence of functional groups on main chains and nonrubbery materials, such as proteins, can significantly affect the rheological properties and the processing conditions of rubber before the vulcanization process. Raw rubber can be divided into two different fractions, sol (soluble part) and gel (insoluble part). Of course, this definition depends somewhat on the solvent used. Even though the main chain in both portions of rubber are chemically similar, their significantly distinct mechanical properties have, in fact, been attributed to the nonrubbery materials such as proteins interacting with isoprene chains. It is generally accepted that the amount of nonrubbery materials in the gel fraction is much higher than the sol fraction. The protein apparently interacts quite strongly with specific functional groups on the isoprene chain and is difficult to remove from the gel phase by physical means. It is probable that the different properties between sol and gel rubber is due to the amount of crosslinking of the main chains, but several aspects of the structure need to be answered in greater detail. We know, for example, that the amount of gel fraction can change as a function of extraction solvent. Therefore, one cannot conclude that the interaction between rubber chains even in the gel fraction is strictly chemical in nature. Our premise is that the protein is an important component connecting the isoprene chains.
Effect of Chemical Modification of Solution-Polymerized Rubber on Dynamic Mechanical Properties in Carbon-Black-Filled Vulcanizates
Authors: Nagata Nobuo , Kobatake Takushi , Watanabe Hiroyuki , Ueda Akio , Yoshioka Akira
Published: February 2011

From the Part I experiments, n-butyl-EAB shows a strong interaction (chemisorption) with the carbon black surface. The chemical structure of chemisorbed n-butyl-EAB is similar to that of the component, with a peak at 290 nm. The EAB groups of the chain-ends in the modified polymer enhance the adsorption of the polymer onto CB-N, because of a chemisorption by the EAB groups. We estimate that the reaction mechanism of chemisorption is an acid-base reaction and that SBR-EAB has a conformation somewhat rising in the radial direction on the CB-N surfaces. From the Part II experiments, the saturated adsorption of n-butyl-EAB or the chemically-modified polymer prevents the agglomerate-growth of carbon black and enhances the dispersion stability of the carbon black dispersed in a nonpolar solvent such as benzene. From the Part III experiments, the chemically-modified rubber absorbed strongly onto the CB-N surface enhances the dispersion stability of the carbon black in vulcanizates, and, hence, suppresses the transient-structure formation or network formation of carbon-black-carbon-black particles. The reduction in the transient structure decreases the dynamic-shear modulus at low strain amplitude and, hence, decreases the loss modulus maximum G″max, causing the increase of rebound resilience.
Comparison of Screw Extrusion of Rubber Compounds with Different Extruder/Screw Combinations
Authors: Kubota Kazuhisa , Brzoskowski Ryszard , White James L. , Weissert Frederick C. , Nakajima Nobuyuki , Min Kyonsuku
Published: February 2011

The extrusion of rubber compounds has long been an area of industrial importance. There have, however, been few basic studies on the flow characteristics of rubber compounds. Considerably more extensive investigations have been reported on the mechanisms of screw extruders for thermoplastics. The latter researches are summarized in the monograph by Tadmor and Klein and the textbook of Tadmor and Gogos. Maddock, and others carried out experimental studies which led to basic flow mechanisms of thermoplastics in screw extruders. Maddock fed pigmented pellets to screw extruders and pulled screws from the barrel with the plastic stips in it, which were then unwound and cross-sectioned. Few screw-pulling investigations have been published for rubber compounds. We are only familiar with the work of Menges and Lehnen and our own recent studies. In the present paper, we describe a fundamental study of flow mechanisms in screw extruders for rubber compounds. We expand our studies based on the Maddock screw-pulling procedure, with rubber strips containing markers in a comparison of three different screw extruders. The placement of the rubber is recorded and the rubber sections examined for their flow patterns. This work also extends our earlier market experiments on flow of rubber compounds through dies. Our results on screw extruders exhibited both transverse flow patterns and sometimes showed a starved, partially filled screw. Our efforts in the present paper seek to generalize these results. We also describe a theoretical model for the flow of rubber compounds in a screw extruder and compare it to our experiments.
Air-Lubricated Die for Extrusion of Rubber Compounds
Authors: Brzoskowski Ryszard , White James L. , Szydlowski Witold , Weissert Frederick C. , Nakajima Nobuyuki , Min Kyonsuku
Published: February 2011

The flow of a rubber compound through a die is an essential step of a rubber extrusion operation. The die forms the compound into the desired shape. In many cases, the output of the extruder is limited by the resistance of flow in the die. Too high pressure losses in the die may additionally result in an excessive increase of the temperature, and unwanted crosslinking of the rubber compound may occur. Various possibilities are available to reduce the resistance of flow in the die. The simplest one is elevation of the processing temperature, which leads to reduction of viscosity. This can be done, however, only within some limit. Reduction of the pressure losses in the die may also be achieved by decreasing the die length, but this option produces larger swelling. Other more innovative procedures may be suggested. Evidence exists that the pressure losses in the die can be reduced by introducing sound or ultrasonic waves of high intensity into the die zone. In this paper, we present what we believe is a new idea, another option of decreasing a resistance of flow of the rubber compound in the die. This is achieved by injecting air between the rubber compound and the wall of the die. This paper continues the experimental studies of the authors on the flow of rubber compounds in dies and screw extruders.
Determination of the Coefficient of Friction of Rubber at Realistic Tire Contact Pressures
Authors: Lazeration J. J.
Published: February 2011

The rotational friction test effectively eliminated the severe normal contact pressure gradients inherent to many of the conventional test apparatus. The uniform pressure distribution of the annular test specimen, confirmed by Fuji pressure-sensitive paper, provided a pointwise value of the coefficient of friction essential to full-field traction and wear prediction. Models of the form μ=AP−1/k as predicted by true contact area and elasticity theory gave excellent correlation to experimental data and showed that, at high pressures, the value of μ can vary significantly from its value at the average contact pressure acting on the tire. A decrease in the pressure dependence of μ with increasing surface roughness was observed by investigating μ on plexiglass, ground glass, and machined steel substrates. A pressure dependence of P−1/2 for plexiglass, P−1/4 for ground glass, and P−1/5 for machined steel was determined. The surface roughness of both the rubber and the test substrate were found to influence the magnitude and pressure dependence of μ. Consequently, care must be taken with sample preparation for reproducibility and simulation of an actual tread surface if tire performance predictions are to be made.
Effect of Network Chain Length on the Tearing Energy Master Curves of Poly(Dimethyldiphenyl Siloxane)
Authors: Yanyo L. C. , Kelley F. N.
Published: February 2011

Five different molecular weights of vinyl-terminated poly(dimethyldiphenyl siloxane) were endlinked with tetrakis(dimethylsiloxy)silane to produce networks of various crosslink densities. A hydrosilation endlinking reaction was chosen, since this method provides the advantage of easily controlling the network chain length and network morphology. Tear energies were determined using a modified trouser-tear test piece at several rates and temperatures. All of the tear energy data for each crosslink density could be shifted to a single master curve with the same WLF coefficients, C1=6 and C2=108 K. The threshold tear energy of PDMDPS is different from unsubstituted PDMS because the average molecular weight per backbone atom and density are increased by the presence of phenyl groups. Each of the tear-energy master curves of PDMDPS shift to a single curve with Mc1/2, except in regions near the glass transition. Deviations of the curves are observed to coincide with increases in the crack-tip diameter with increasing molecular weight between crosslinks. In the lower transition region of the tear-energy master curve, the loss function is determined by the hysteresis of the material. Near the glass transition, the effect of the strain energy and strain-energy distribution, as well as the hysteresis, must be considered. Deviations of the master curves with crosslink density can also be explained from the changes in the loss function for each curve due to the differences in strain and strain distribution for different crack-tip diameters which were visually evident. Andrews' representation of the loss function of the tear energy is known to be dependent on hysteresis, strain energy, and the strain-energy distribution near the crack tip. Modifying his relation, the tear energy was shown to increase with hysteresis as long as the strain energy and strain-energy distribution remained constant. The strain energy distribution was also shown to increase directly with the molecular weight between crosslinks of the network.
Rolling Resistance and Fatigue Life of Tires
Authors: Grosch K.
Published: February 2011

The elastic energy amplitude to which every point of a rotating tire is subjected to, leads to an increase of temperature in the tire as some of this energy is converted into heat because of the viscoelastic nature of rubber. It also influences the fatigue life of a tire, since the rate of crack growth depends both on the energy input and the temperature which results from the energy loss.
Variation in the Molecular Weight Distribution of Rubber from Cultivated Guayule
Authors: Backhaus R. A. , Nakayama F. S.
Published: February 2011

The molecular weight (MW) and the molecular weight distribution (MWD) of natural rubber (NR) are directly related to rubber quality. Although over 2000 species of plants are capable of producing rubber, only about a dozen are recognized as producing sufficient quantities of high quality, high MW rubber necessary for commercial use. Guayule, Pathenium argentatum Gray, can synthesize high MW rubber similar to Hevea and is actively being developed as a new source of NR for the arid regions of the world especially in the United States. Rubber of MW 105 or less is considered unsuitable for much commercial use. Unfortunately, most of the 2000 rubber synthesizing species are believed to produce rubber with a MW of approximately 5×104 and a unimodal MWD4. The MWD of Hevea, however, has a bimodal distribution exhibiting two MW peaks. The major peak exists at a MW of about 7×105 and extends to 106 and beyond. A minor peak or flattened shoulder is also frequently present which corresponds to a MW of 5×104. This bimodal MWD nearly always exists for Hevea, but the amplitude of the two peaks may vary due to variety, age, and tapping frequency. Such variation in the MWD can lead to differences in the average MW. In rubber obtained from native stands of guayule, reports indicate the existence of only a unimodal MWD. Little is known about the environmental or genetic factors influencing rubber MW in stands of cultivated guayule. Since general husbandry and genetic variation seem to affect Hevea rubber, it is not unreasonable to suggest that differences may also appear in guayule, as other work implied.
Absorption of Silicone Oil by a Dimethylsiloxane Elastomer
Authors: Rice S. L. , Diaz A. F. , Minor J. C. , Perry P. A.
Published: February 2011

Polydimethylsiloxane elastomer immersed in DC 200 silicone oil at temperatures of 180–200°C absorbs oil by two concurrent processes, a rapid and reversible diffusion process and a slower, irreversible process resulting from the chemical degradation of the sample. Absorption by diffusion reaches equilibrium in 200 h, and the absorption capacity depends on the amount of curing agent used in the preparation of the elastomer composite. The oil absorbed during this period can be removed by extraction. The absorption capacity is less for the elastomer composites containing silica and decreases linearly with the volume fraction of elastomer in the sample, indicating that only the elastomer absorbs oil. The rate of absorption depends on t1/2 and has a weak temperature dependence. The diffusion coefficients are in the range 10−12 m2/s, and do not seem to be affected by the presence of filler. While the diffusion of oil does not appear to produce chemical changes in the elastomer, the elastomer is gradually destroyed by the slower chemical process, which promotes the absorption of additional amounts of oil.
A Novel Dynamic Light-Scattering Method to Determine the Modulus of Gels
Authors: Nossal Ralph
Published: February 2011

Laser light sources currently are employed in numerous remote sensing applications. The following discussion concerns a particular application, namely, the use of laser light to probe the mechanical response of soft gels and, thereby, to measure the storage shear modulus and internal viscosity of a sample. The technique described in this paper was developed for biological investigations (e.g., the study of fibrin clots or cytoplasmic gels). However, it has much wider applicability and has been employed, for example, to study thermoreversible polysaccharide gels, as well as covalently crosslinked polyacrylamide networks. This paper in part is a survey of previous applications, and in part a report of new results. The initial sections contain discussions of the basis of the measurement and its use to ascertain the shear storage modulus. The later sections contain new material relating to detection of dissipative mechanisms which, when certain conditions are satisfied, can be described by a gel viscosity coefficient.
A New Pull-Out Test for Tire Cord Adhesion—Part I. Hot Bonding
Authors: Ellul M. D. , Emerson R. J.
Published: February 2011

A new pull-out cord adhesion test has been investigated. It consists of a cord partially embedded axially in a long steel-enclosed rubber cylinder. A strain-energy fracture mechanics approach was used to analyze the test in order to derive the energy of detachment, a more fundamental measure of the strength of adhesion than pull-out force, since the modulus and geometry terms are factored out. Good agreement was observed between strain-energy fracture mechanics theory and experiment. In the model system in which steel rods of various diameters were substituted for the cord, rubber thermal shrinkage after cure caused partial internal debonding along the rod if the level of adhesion was not sufficiently high. While no debonding could be detected with truck tire cords, the shrinkage probably reduced any friction effects leading to a more accurate measure of the energy of detachment/fracture. The disadvantage of the Coaxial Shear Pull-out Test geometry (for samples prepared by the hot-bonding procedure as described here) is that scientific discretion based upon measurements of axial stiffness and shear modulus calculations together with subsequent comparisons to shear moduli from an independent measurement, (e.g., hardness) must first be used in order to determine whether debonding has occurred. If debonding is present, then it should be corrected for as shown in the previous discussion section. If no debonding has occurred (e.g., certain brass-plated steel tire cord adhesion systems) then the analysis is more straightforward. Thus, in principle, providing the right analysis is performed on the result, this test is capable of yielding reasonably accurate estimates of the work of adhesion when failure is interfacial or the work of cohesive fracture when failure is in the rubber. In practice however, this pull-out test with samples prepared by the hot-bonding procedure should be reserved for measurements of strong adhesive systems, such as original adhesion of truck tire cords in commercial compounds. A mechanical solution for debonding, involving a cold-bonding procedure is advanced in Part II of this study.
Nonisothermal Vulcanization of Rubber Compounds
Authors: Isayev A. I. , Deng J. S.
Published: February 2011

In the present paper, progress has been made in developing a model for nonisothermal vulcanization of rubber compounds. The model is presently based on differential scanning calorimetry (DSC) measurements of heat evolved during vulcanization. The model parameters are determined from several isothermal DSC scans including measurements of induction time and rate of vulcanization. This model has conveniently been employed for a calculation of the temperature distribution during vulcanization of a rubber slab based on a one-dimensional heat-conduction equation with a heat-generation term. The simulation allowed us to predict the dynamics of the development of the state of cure distribution in the rubber slabs. Predicted results from the vulcanization model have been verified with experimental data on induction time and rate of vulcanization from nonisothermal DSC scans and with measurements of the state of cure distribution in rubber slabs cured under different vulcanization conditions between two heated plates. Although this model is based on DSC data, the approach developed can easily be extended to similar curing data obtained by means of the modulus measurement technique.
Processing Ease and Rubber—Carbon-Black Interaction
Authors: Nakajima N. , Miller R. A.
Published: February 2011

Two samples of poly(ethyl acrylate) rubber, different in their mill processability and their manner of accepting carbon black were examined. This is a case history of how we differentiated Theological behavior of gum elastomers and how we characterized the rubber—carbon-black interaction in the compound. For the former objective, the dynamic mechanical properties were measured over the temperature range of interest. This information was used to interpret the difference in mill processability. For the latter objective, several carbon blacks in different particle size and structure were compounded with these samples. The effect of the different carbon blacks on these elastomers was examined with tensile stress-strain measurements. At least a part of the differences in behavior could be interpreted as the differences in the interaction between rubber and carbon black.
Sulfur-Free Vulcanization Systems for Diene Rubber
Authors: Kempermann Th.
Published: February 2011

In accordance with the types of crosslinking listed in Figure 17, the vulcanizing agents discussed in this survey can be classified as follows: (see PDF for table)
Effect of Carbon Black on the Mechanical Properties of Elastomers
Authors: Meinecke Eberhard A. , Taftaf Mansour I.
Published: February 2011

The strain-amplification concept developed by Guth and Gold can predict the effect of carbon black loading on the mechanical properties of elastomers, provided that the experimental conditions and the samples correspond to the assumptions made in the derivation of the Guth-Gold equation, namely: a) Any artifacts arising from dynamic testing in tension have to be considered and eliminated by the proper analysis. b) Samples have to be prestretched prior to testing to break up particle agglomerations and to eliminate any possible entanglement slippage. c) Spherical particles have to be used or Medalia's occluded volume concept has to be applied for fillers with high structure. d) Hysteresis properties are dependent upon the square of the strain-amplification factor. e) Viscoelastic effects on the shape and level of stress-strain curves have to be eliminated.
Autohesion and Cohesion of Uncrosslinked Elastomers
Authors: Hamed Gary R.
Published: February 2011

Over the past several years the author and collaborators have studied the autohesion (tack) and cohesion (green strength) of uncrosslinked elastomers. It is the purpose of this short review to present some highlights of this research. This is not meant to be a brief review of the entire literature on the subject.
Elastomers—Past, Present, and Future
Authors: Mark Herman F.
Published: February 2011

If we look back on our story we might summarize: laborious and imaginative pioneering was done over about 100 years in the past. As soon as a few basic principles were established, the synthesis, structure, and uses of elastomers rapidly invaded large disciplines of polymer science and engineering in 60 years up to the present. From now on, in the future, there can be expected a period of more concentrated efforts on selected problems of special urgency.
Ambient Electrical Properties of Mica-Styrene-Butadiene Rubber Composites
Authors: Debnath S. , De Prajna P. , Khastgir D.
Published: February 2011

We have studied the effect of addition of (a) mica, (b) silane coupling agent, and (c) silane-treated mica on the ambient dielectric properties of vulcanized styrene-butadiene rubber. It is observed that both dielectric constant and dielectric loss increase as mica, silane, and silane-treated mica are added. The increase is more pronounced in the case of silane-treated mica than for the untreated mica systems. The observed values of dielectric constants are in close agreement with the calculated ones obtained from different theories of heterogeneous dielectrics. Dielectric strength shows an increasing trend in the presence of mica. At higher mica loading, D.C. conductivity decreases slightly.
Photocrosslinking of EPDM Elastomers. A New Method for Rapid Curing of Elastomer Coatings at Room Temperature
Authors: Hilborn J. , Rånby B.
Published: February 2011

Photocrosslinking with UV light in air of silica-filled EPDM rubbers is possible in practical applications for at least 2 mm thick layers which are cemented onto a steel substrate. To find the optimum formulation of the rubber composition, it is essential to know the function of each component. Further optimization can be achieved by using the APOE to the TMPTA system and by using a suitable primer cement on the metal.
Morphology and Physical Properties of Thin Films of Thermoplastic Elastomers from Blends of Natural Rubber and Polyethylene
Authors: Akhtar Sania
Published: February 2011

The morphology and properties of thin films prepared from NR-PE blends have been discussed. The present paper emphasizes the effect of method of preparation on the final properties. To this end, the films were quenched in ice (−10°C), cooled in water (25°C), cooled in air (30°C), and cooled in the press (from 160°C to room temperature) under a pressure of 0.34 MPa. The modulus, tensile and tear strengths, and elongation at break were found to vary considerably with the method of preparation. X-ray and DSC results confirmed the fact that the changes were related to the crystallite morphology rather than the degree of crystallinity. In addition, it was observed that the high rubber blends were less susceptible to the method of preparation than the high plastic blends and pure polyethylene.
Mixing of Carbon Black with Rubber. VI. Analysis of NR/SBR Blends
Authors: Cotten George R. , Murphy Lawrence J.
Published: February 2011

The distribution of carbon black in NR/SBR blends was determined through the analysis of bound rubber. The NR/SBR blends were found to be very different from the previously studied SBR/BR compounds: these differences were assigned to mutual insolubility of the two polymers and a very high molecular weight of NR. In NR/SBR blends, it was found that changes in molecular weight of the polymer has no effect on the carbon black distribution in the blend. While the “activity” of carbon black did not affect the distribution, the loading of the black in NR decreased linearly with increasing surface area of the black. Approximately 35% of normal tread blacks (surface area 80–100 m2/g) was found in the NR phase. However, the bond between NR and carbon black is quite weak, and black continues to migrate into the SBR phase on prolonged mixing or during blending of NR and SBR masterbatches.
Identification of Organic Components in Uncured Rubber Compounds Using Mass Spectrometry
Authors: Lattimer R. P. , Harris R. E. , Rhee C. K. , Schulten H-R.
Published: February 2011

Three carbon-black-filled rubber compounds of known composition were analyzed by mass spectrometry. Direct thermal desorption was used with three different methods of ionization (EI, CI, FI). In addition, the three rubbers were examined by FAB-MS (without liquid matrix) as a means for surface desorption/ionization. Extracts of the rubbers were also examined using two different solvents (acetone and acetonitrile). Each extract was examined directly by five methods of ionization (EI, CI, FI, FD, FAB). Of the various vaporization/ionization methods, it appears that FI/FD is the most efficient for identifying typical organic additives in rubber stocks. The analysis can be carried out using either the untreated rubber (FI mode) or else a solvent extract (FD mode). Molecular ions are dominant, which facilitates the characterization of the complex organic additive mixtures that are present in typical compounded rubbers. For samples in which the identity of FD/FI molecular ions is unclear, further analysis using other methods (EI, CI, FAB, MS/MS, GC/MS, LC/MS, high resolution) can be carried out to gain additional information. We conclude that FD and FI yield the most useful information in the shortest period of time. The main difference between the results of this study and those of the volcanizate study is with respect to the curatives. Intact accelerator molecules could readily be observed in the spectra from the uncured stocks, while only accelerator fragments could be observed from the vulcanizates.
An Experimental Study of Flow and Stress Fields in a Pressurized Mooney Viscometer
Authors: Montes Sergio , White James L. , Nakajima Nobuyuki , Weissert Frederick C. , Min Kyonsuku
Published: February 2011

The boundary conditions of rubber compounds on solid surfaces during extrusion has long been a subject of question. The concerns of Mooney on this topic date back 60 years. He continued to return to this question throughout his career. In more recent years Vinogradov and his coworkers have called attention to slip phenomena occurring in the extrusion of elastomers through dies. This is associated with fluctuating pressure losses which occur at the onset of extrudate distortion. Such behavior has also been observed with rubber-carbon-black compounds. More recently, Turner and Moore have developed a pressurized rotational rheometer to characterize this type of behavior in rubber compounds. We have recognized the importance of this problem in our own laboratories. Marker experiments have been used in extrusion of rubber compounds to detect slippage. In the present paper, we describe an experimental study of the response of gum elastomers and their carbon black compounds in a pressurized Mooney viscometer of the general design of Turner. We look first specifically at the variations of steady torque (shear stress) with the magnitude of applied pressure. We then look at the characteristics of sheared samples and the responses to pressure transients.
A Novel System for Crosslinking Fluoroelastomers
Authors: Ogunniyi D. S.
Published: February 2011

The use of HBTBP as a crosslinking agent in fluoroelastomers has been reported. HBTBP was found to be especially suitable for FKM-G polymer, and the mechanism of crosslink formation in this fluoroelastomer was investigated. Compounding studies, swelling measurements, solvent extraction, and nitrogen tests have been used to tentatively shed light on the crosslinking mechanism. The results of these tests were used to propose mechanisms of crosslink formation occurring through a combination of: (i) radical abstraction of the methylenic hydrogen in FKM-G and crosslink formation through the interaction of the resulting radicals, (ii) interaction of a reactive intermediate from (i) with the raw FKM-G polymer, and (iii) nucleophilic substitution.
Structure-Property Relationship in Rubber-Modified Propylene-Ethylene Block Copolymer Blends
Authors: Sain M. M. , Hudec I. , Beniska J. , Rosner P.
Published: February 2011

The incorporation of a phase modifier, as is well known in the case of elasto-plastic blends, leads to an improvement of mechanical properties and brittleness character for PRP-EVA blends. Similarly, the influence of a cocuring agent and a phase modifier on NR-PRP blends also improved the mechanical properties. Although the modification of the PRP-EVA blend has very little influence on glass transition temperatures, the NR-PRP blends show a measurable shift in their glass-transition temperatures. It is demonstrated that strong interaction occurs between the elastic and plastic components of the blends. Further, it has been shown that this interaction is responsible for improved properties of the blends over that of the pure polymer components.
Monte Carlo Simulation of Styrene-Butadiene Elastomers
Authors: Stamhuis J. E. , Heitman W. G. , van Ballegooijen H. , Osborne D. J.
Published: February 2011

A relatively simple model for SBR networks has been developed that is based on reaction kinetics. In addition, any copolymer structure not directly originating from reaction kinetics but from the polymer physicist's imagination can be fed into the model; the only thing to be done in this case is to construct an imaginary polymer composition curve as input for the model. The model then visualizes in a quantitative manner the resulting polymer chains and their structure in the network in terms of monomer sequence distribution, network segment distribution, and the distribution of the crosslinks over the individual chains. These features are essentially the basis of further work regarding the mechanical and viscoelastic properties and, ultimately, the road behavior of solution-SBR-based tread vulcanizates.
Heat Build-Up and Blowout of Rubber Blocks
Authors: Gent A. N. , Hindi M.
Published: February 2011

The phenomenon of explosive “blowout” of thick rubber blocks, under repeatedly applied, severe compressive loads, is due entirely to the development of high internal temperatures. If the compound is electrically conductive, the phenomenon can be duplicated in a microwave oven without imposing any mechanical loads. Blowout appears to consist of the expansion to burst of pressurized cavities within the rubber. Pressure appears to be generated internally by a volatile constituent or decomposition product of the rubber compound. Expansion is restrained by elastic stresses set up in the rubber as the cavity expands. Bursting is made easier in some compounds because they soften markedly at high temperatures and thus lose resistance to cavity expansion. Different elastomers have strikingly different blowout temperatures. Butyl rubber compounds blow out at relatively low temperatures, about 180°C, whereas NR and SBR compounds blow out at temperatures of about 200°C or higher. Also, different vulcanizate structures have different blowout temperatures. For example, materials with C-C or monosulfidic crosslinks show higher blowout temperatures than those with polysulfidic crosslinks. Polybutadiene compounds did not blow out at all. Instead, they developed internal cavities that grew in size and number but never burst open to the exterior, probably because the internal pressure never reached sufficiently high levels. It is concluded that the principal cause of blowout is the generation at high temperatures of sufficient quantities of a volatile decomposition product, but the reaction is specific to the particular elastomer and crosslinking system employed. It does not appear to consist of simple thermal decomposition of the hydrocarbon elastomer, which would require higher temperatures than those observed at blowout.
Strain-Rate Amplification of Carbon-Black-Filled Rubber Compounds
Authors: Nakajima Nobuyuki
Published: February 2011

The strain amplification is one of the recognized causes of the reinforcement of rubber by carbon black. Previously, we evaluated strain amplification in nonequilibrium, i.e., stress-strain measurements. Carbon-black-filled rubber compounds were used. In these examples, not only strain but also strain rate must be amplified, since it is a dynamic situation. Because the behavior of the gum matrix is strain-rate dependent, strain-rate amplification is also an important aspect of the rubber compound behavior. In this paper, we presented case studies of strain-rate amplification with several compounds involving variation of gum rubbers and carbon blacks.
Rubber-Bound Antioxidants. I. Amine Antioxidants Bound to Polychloroprene Rubber
Authors: Al-Mehdawe Mohammed S. , Stuckey J. E.
Published: February 2011

Amine antioxidants are found to react with chloroprene (CR) type-W rubber with its reactive chlorine atoms. These reactions take place during high-shear mixing in a torque rheometer, or in a Winkworth mixer at higher temperature, or during the vulcanization of the elastomers at 160°C. Mixed alkyl, aryl secondary amines are shown to react only at the alkyl-substituted amino group. The concentrations of the bound antioxidants are estimated by IR spectroscopy after complete extraction. Monsanto Rheometer studies show that, in many cases, the crosslinking reaction of CR rubber, which takes place through the chlorine atom, is reduced by the presence of the antioxidants. The effectiveness of the rubber-bound antioxidant is assessed by accelerated oven aging and stress techniques. It is shown that immobilization of amine antioxidants by combining them with the network does not impair their antioxidant activity.