bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.