bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Mixing Efficiency in Batch and Continuous Mixers
Authors: Manas-Zloczower Ica 
Published: February 2011

Abstract
In this paper we have reviewed some of the results of 3-D, isothermal flow simulations for batch and continuous mixers. The flow patterns were obtained by using FIDAP, a fluid dynamics analysis package based on the finite element method. The problem of time dependent flow boundaries due to the rotations of the rotors in the Banbury mixer, was solved by selecting a number of sequential geometries to represent a complete cycle. Non-slip boundary conditions for the stationary and moving surfaces were employed. For different regions of continuous mixers we used a nominal value for the normal stress difference in the axial direction as an additional boundary condition. The results obtained in terms of velocity and pressure profiles were further processed to analyze mixing efficiency. Dispersive mixing efficiency was studied in terms of the shear stresses generated and the elongational characteristics of the flow field. Distribution plots for shear stresses and a parameter λ, quantifying the elongational flow components, were obtained in various regions of the mixing equipment. Volumetric distributions for the same parameters as well as average values can be also used to analyze dispersive mixing efficiency. Distributive mixing was studied numerically by means of tracking particles in the mixing equipment. In batch mixers or batch elements of continuous mixers distributive mixing can be well characterized in terms of the pairwise correlation function. In continuous mixing equipment, distributive mixing can be analyzed in terms of concentration functions and the spatial evolution of pairwise correlation functions. The framework developed to analyze dispersive and distributive mixing efficiency opens the way for an unambiguous evaluation of the performance of any mixing equipment and, furthermore, for their design and process optimization.
Methods of Devulcanization
Authors: Warner Walter C. 
Published: February 2011

Abstract
The literature contains the record of numerous methods which have been used to reverse the vulcanization process. Indeed, many of these methods have long been used, especially for purposes of analysis and/or studying mechanisms of vulcanization, so that they are commonplace in most large laboratories. The purpose of this paper is to review the literature on an eclectic basis. The opportunity exists to take a fresh look at some of these techniques with a view to consider up-scaling for recovery of rubber and other ingredients for eventual commercialization. The processes would have to be studied from the standpoint of fine-tuning reactants, solvating media, conditions of minimal degradation, keeping toxic exposure to safe levels, economics, etc. The possibility also exists of combining some of these techniques with others, such as those presented at a recent symposium, which have been developed to a more advanced stage of engineering. Included in a list of the chemical probes which will be discussed and/or referenced are propanethiol, hexanethiol, sodium di-n-butyl phosphite, triphenylphosphine, lithium aluminum hydride, methyl iodide and phenyl lithium. Related methods which have been mentioned include microbial action, grafting reactions, catalysis, microwaves, sonics and solution by o-dichlorobenzene.
Measurement of the Unsaturation of Butyl Rubbers by the Iodine Index Method
Authors: Dhaliwal G. K. , Wilson G. J. 
Published: February 2011

Abstract
Iodine index is used in the rubber industry to measure the unsaturation of butyl polymers. The procedure involves a complex mixture of iodine, mercuric acetate, and trichloroacetic acid (TCAA), and requires an empirical calibration to convert the iodine index to the degree of unsaturation. In this paper, the chemistry of the iodine index test is discussed and, the factors affecting the measurement, are detailed. Acetyl hypoiodite formed in situ by the reaction of I2 and Hg(OAc)2 is postulated to be the reactive species which iodinates the unsaturation in butyl rubber. Mercuric acetate is not a catalyst, as usually believed, but is consumed in stoichiometric amounts. Hence, care has to be exercised not to use too little of the mercuric acetate when determining the iodine index of polymers with high levels of unsaturation. A large excess of mercuric acetate must also be avoided, as it may form complexes with iodine and, thereby, lower the effective concentrations of both the reactive reagents.
Chemical Surface Treatments of Natural Rubber and EPDM Thermoplastic Elastomers: Effects on Friction and Adhesion
Authors: Ellul M. D. , Hazelton D. R. 
Published: February 2011

Abstract
Natural rubber thermoplastic elastomers (NRTPEs) made by dynamic vulcanization of natural rubber during its mixing with polypropylene were subjected to various halogenation surface treatments. Marked reduction in the coefficient of friction is possible depending on the chemical treatment employed, TPE composition and the presence of a lubricant. As a result of halogenation there is an increase in the microroughness and hardness of the NRTPE surface. These effects in part explain the large decrease in the friction coefficients since the contact area is decreased. Thus NRTPE can be employed in applications requiring low friction, such as certain types of seals. Another consequence of halogenation of NRTPE is the increase in its surface energy which in turn promotes adhesion to various polar substrates. Indeed it was determined that halogenation of NETPE is an effective way of priming the surface of these materials for adhesion to acrylic and other substrates. Ethylene Propylene Diene Monomer rubber-Polypropylene thermoplastic elastomers (EPTPEs) were used as a control in this study to assess how a low unsaturation EPDM-based TPE compares with the high unsaturation NRTPEs in different halogenation surface treatments.
Effects of Aging on the Fracture Behavior of Chlorinated Polyethylene and Chlorosulfonated Polyethylene
Authors: Nichols Mark E. , Pett Robert A. 
Published: February 2011

Abstract
The thermoxidative aging behavior of chlorosulfonated polyethylene (CSM) and chlorinated polyethylene (CPE) vulcanizates has been investigated. Aging rates were determined by measuring isothermal oxidative induction times in a differential scanning calorimeter. Aging rates were also determined by measuring the decrease in the critical tearing energy of compounds as a function of aging time and temperature. Rate constants determined from induction time and tearing energy experiments displayed typical Arrhenius behavior. Below 240°C, rate constants from both experiments fell on the same line, suggesting that both experiments probe the same reaction. Activation energies for degradation of CSM and CPE were 88 and 108 kJ/mol respectively. Above 240°C, the mechanism of degradation changes with a corresponding change in activation energy to 190 and 232 kJ/mol for CSM and CPE, respectively. In the unaged state, the critical tearing energy of the carbon black-filled CPE compound is 50% higher than that of the carbon black-filled CSM compound. The rate of aging of CSM compound is approximately twice that of the CPE compound at equal temperatures. Decreases in tearing energy were attributed to additional crosslinking of the elastomer network. Combining oxidative induction times and critical tearing energy measurements may offer significant advantages in streamlining accelerated testing of elastomeric materials.
NMR Study of Miscibility in Polyepichlorohydrin/Poly(Vinylmethylether) Blends
Authors: McGrath K. J. , Roland C. M. 
Published: February 2011

Abstract
129Xe NMR spectroscopy is employed to demonstrate that polyepichlorohydrin and poly(vinylmethylether), which have virtually equal glass transition temperatures, form thermodynamically miscible blends. This conclusion is drawn from the appearance of a single resonance in the blend spectrum, at a chemical shift differing from that calculated for the fast exchange regime. 13C NMR results are consistent with thermodynamic miscibility, and reflect the similarity of the component dynamics.
Cure and Mechanical Behavior of Rubber Compounds Containing Ground Vulcanizates. Part I—Cure Behavior
Authors: Gibala David , Hamed Gary R. 
Published: February 2011

Abstract
SBR compounds containing ground vulcanizates of known composition and cure state were prepared and the cure behavior studied. Decreases in scorch times and maximum rheometer torques were observed when ground vulcanizates were added to the SBR compounds. Two primary phenomena are proposed to explain these findings: (1) migration of sulfur from the matrix rubber to the ground vulcanizate (causing torque reduction) and (2) migration of accelerator fragments from the ground vulcanizate to the matrix (causing decreased scorch time). The first proposal is based on direct measurement of sulfur concentrations in both ground particles and the matrix. The second is based on the detection, by high performance liquid chromatography, of mercaptobenzothiazole in the extract from ground vulcanizates. The second also is inferred from the fact that ground vulcanizate particles cured with peroxide do not alter scorch time. Moreover, a compound containing sulfur and ground (accelerated-sulfur vulcanized) rubber, but no added accelerator, nonetheless exhibits acceleration of cure.
Reduction in Viscosity of an SBR Compound Caused by Mastication and Disagglomeration during Mixing
Authors: Clarke J. , Freakley P. K. 
Published: February 2011

Abstract
It would be advantageous to determine the causes of changes in rheological behavior of a compound during mixing, so that mixing times and conditions could be optimized to give the desired processing behavior and properties of the final product. The causes of changes in viscosity during mixing of a compound containing only elastomer and carbon black were investigated by examining concurrent changes in viscosity of the gum, density of the compound and degree of carbon-black disagglomeration. The reduction in viscosity occurring during mixing could be attributed to mastication of the elastomer and disagglomeration of the carbon black. The effect of mastication could be removed by calculating values of relative viscosity, using the viscosity of the gum treated in a similar way to the compound and with an allowance being made for strain-rate amplification. The decrease in relative viscosity of the compound with increased mixing was attributed to a reduction in effective volume fraction of filler caused by immobilized rubber being released as carbon black agglomerates were broken down. The dibutyl phthalate absorption (DBPA) value of the carbon black gave a good indication of the amount of immobilized rubber present in an agglomerate.
Characterization of the Behavior of Rubber for Engineering Design Purposes. 1. Stress-Strain Relations
Authors: Davies C. K. L. , De Dilip K. , Thomas A. G. 
Published: February 2011

Abstract
The stress-strain behavior of a range of black-filled rubbers has been studied in extension, compression, pure shear and simple shear. The data have been analyzed to examine the validity of Gregory's hypothesis that the stored energy function U of filled rubbers can be expressed solely in terms of the strain invariant I1, ignoring I2, to an accuracy adequate for most engineering design requirements. Our results confirm his suggestion. An analytical form for U is proposed which gives a very good fit to the experimental data for strains from less than 0.1% to somewhat greater than 100%, which cover the range of interest for most engineering applications. The dependencies of the parameters in the expression for U on filler level and degree of crosslinking have been examined. It has thus been demonstrated that, for a given material, the form of U can be determined from the measured stress-strain relation in any simple deformation mode, shear or tension for example, without the necessity of relatively difficult biaxial measurements, and that this function should then be applicable to any deformation mode, complex or simple.
On the Puncture Mechanics of Rubber
Authors: Stevenson A. , Malek Kamarudin Ab 
Published: February 2011

Abstract
The mechanics of puncture have been studied experimentally and theoretically, by means of fracture mechanics. When a sharp cylindrical indentor penetrates rubber, a starter crack initiates as a ring on the rubber surface before puncture occurs. By treating this as militating puncture, an equation has been derived for the energy of puncture. The elastic energy stored in the rubber is considered in terms of the energy beneath and surrounding the indentor. An equation for the energy beneath the indentor is determined with the aid of a model experiment based on the biaxial stretching of rubber by inflation. The energy stored in the rubber surrounding the indentor is calculated using elasticity theory. The magnitude of these contributions is assessed for different indentor sizes and different rubber vulcanizates, The theoretical approach is shown to be verified by a series of experiment for sharp indentors. The values of puncture energy so obtained were found to agree well with the catastrophic tearing energy obtained from trouser tear tests. For blunt indentors which do not cause ring crack formation, other considerations are needed. These are discussed together with experimental results for hemispherical indentors.
Quantitative Metathetic Degradation of Rubbers and Sulfur Crosslinked Rubbers—Including Tires
Authors: Thorn-Csányi Emma 
Published: February 2011

Abstract
Unsaturated polymers can be converted metathetically to fragments of low molecular weight by adding monoolefins. Since the scission of the polymer backbone always occurs at the double bonds, analysis of the degradation products enables a conclusion about the polymer microstructure. Our earlier works have shown that in case of polybutadienes and styrene-butadiene copolymers, the catalyst system “tungsten hexachloride/tetraalkyltin/diethylether” allows a selective degradation and detailed determination of the microstructure. On the other hand complete degradation of polyisoprenes and sulfur crosslinked rubbers failed using conventional metathesis catalysts. Our latest investigations show that using stable transition metal carbenes as catalysts, degradation of polyisoprenes and sulfur-crosslinked rubbers (including tires) proceeds quantitatively. This opens up a method of microstructure determination of crosslinked rubbers, including tires. Results obtained using well denned transition metal carbenes will be compared with those gained employing conventional catalyst systems.
Influence on Friction Force of Adhesion Force between Vulcanizates and Sliders
Authors: Mori Kunio , Kaneda Satoshi , Kanae Kentaro , Hirahara Hidetoshi , Oishi Yoshiyuki , Iwabuchi Akira 
Published: February 2011

Abstract
The effects of vulcanizate and slider surface free energy—as well as the adhesion force (P) between them—on friction the force (F) and the coefficient of friction (μ) has been investigated. SBR and NBR vulcanizates were prepared using three molds differing in surface free energy. The mold with a high surface free energy gave a vulcanizate surface possessing polar groups. The mold with low surface energy gave a vulcanizate surface with many nonpolar groups. The coefficient of friction increased with the surface free energy of SBR and NBR vulcanizates. With SBR vulcanizate (surface free energy, 31.3 mJ·m−2) and teflon slider (surface free energy, 28.1 mJ·m−2) combination having the least surface free energy, the coefficient of friction was constant at greater than a 0.2N load. With vulcanizates and an aluminum slider with high surface free energy, friction force could be detected even at zero load because of the adhesion force at the interface. Friction force increased linearly with adhesion force between vulcanizates and sliders when the physical properties of the vulcanizates and net work chain density were constant. The present results clearly demonstrate the contribution of adhesion force to the friction of vulcanizates.
Rheological and Mechanical Properties of Filled Rubber: Silica-Silicone
Authors: Aranguren Mirta I. , Mora Elsi , Macosko Christopher W. , Saam John 
Published: February 2011

Abstract
This work focuses on the relationship between the morphology of filled rubbers and their behavior at small and large deformations. Composites were made from vinyl terminated polydimethylsiloxane (PDMS) and different fumed silicas. Filler concentration range was kept between 0 to 40 phr (parts of silica per hundred parts of PDMS). Small deformation tests done in oscillatory shear showed that there is coupling of the filler agglomeration and crosslinking effects at high crosslink density while the coupling is negligible at low crosslinking levels. Since crosslinking (hydrosilation) proceeds through the end vinyl groups of the PDMS, lower molecular weight polymers produce rubbers with higher elastic modulus than do high molecular weight silicones. However, the rubbers formed from low molecular weight PDMS break at lower extensions. As in the case of uncured composites, the moduli of the samples increase with silica concentration and amount of silanols on the silica. A silica treated with divinyltetramethyldisilazane gave rubbers of high modulus similar to those obtained from untreated silicas, highlighting the importance of good adhesion between filler and polymer.
Thermally Induced Crosslinking between Polyacrylic Acid and Epoxidised Natural Rubber: Effect of Carbon Black Filler on Strain Dependent Dynamic Mechanical Properties
Authors: Mallick A. , Tripathy D. K. , De S. K. 
Published: February 2011

Abstract
Increases in dynamic strain amplitude (DSA) causes changes in the dynamic mechanical properties of high abrasion furnace (HAF) carbon black filled polyacrylic acid (PAA) and epoxidised natural rubber (ENR) blends. But the changes are more prominent in comparison to conventional rubber vulcanizates. It is believed that crosslinking between PAA and ENR in the presence of carbon black results in the formation of a network-induced-agglomerate superstructure which, however, breaks down on the application of dynamic strain.
Measurement of Elastomer's Bulk Modulus by Means of a Confined Compression Test
Authors: Peng Shu H. , Shimbori Takao , Naderi Akbar 
Published: February 2011

Abstract
The bulk modulus represents a material's resistance to volume change when subjected to pressure loading. Determination of bulk modulus is important for evaluation of applications where compression is involved. Most methods proposed for this purpose are complicated and costly. A simple method is to compress an elastomer button, fully confined in a metal fixture, on a tensile/compression machine. The reliability of this method is studied and a data-treatment technique is proposed to improve the accuracy. It shows that the testing method, with the new analysis technique recommended, is efficient and can be used as a routine test.
Flow Visualization of Intermeshing and Separated Counter-Rotating Rotor Internal Mixer
Authors: Kim Pan Soo , White James L. 
Published: February 2011

Abstract
A flow visualization investigation of material motions and compounding in an internal mixer with intermeshing rotors is described. Rotors based on the design of R. T. Cooke of Francis Shaw and Company are used. Compared with separated rotor designs developed by F. H. Banbury, the distinctive feature is the passage of the rubber and compounding ingredients through the calendering gap between the rotors during mixing. The intermeshing rotors were found to rapidly circulate the materials from rotor to rotor around the mixing chamber and to more rapidly incorporate carbon black and oil relative to double-flighted separated rotors.
Structural and Rheo-Optical Characterization of Random Bicomponent Networks Prepared of Hydroxyl-Telechelic Polyisobutylene and Polytetrahydrofuran
Authors: Kyu Thein , Lee Hak-Soo , Gadkari Avi , Kennedy Joseph P. , Lin Jar-Shyong 
Published: February 2011

Abstract
The structure of a bicomponent network prepared of hydroxyl-telechelic polyisobutylene (HO—PIB—OH) and polytetrahydrofuran (HO—PTHF—OH) has been characterized by small-angle and wide-angle x-ray scattering, birefringence, and differential scanning Calorimetry. A single phase random network was obtained by endlinking HO—PIB—OH/HO—PTHF—OH mixtures using triphenyl methane triisocyanate (TTI) as a crosslinking agent. A small-angle x-ray scattering peak was observed in the PIB networks as well as in the PIB/PTHF bicomponent networks. The glass transition temperature of the random bicomponent network increased with decreasing PTHF molecular weight as the network became tighter. Network tensile properties were analyzed in terms of Gaussian and non-Gaussian network models. The stress-optical law was tested for random networks by measuring the variation of birefringence and stress as a function of elongation. Author to whom correspondence should be addressed. Present Address: Exxon Chemical Co. , Baytown Polymer Research Center, Baytown, TX 77520.
Adhesion and Autohesion of Rubber Compounds: Effect of Surface Roughness
Authors: Gent A. N. , Lai S-M. 
Published: February 2011

Abstract
Sheets of various rubber compounds were pre-molded using different mold surfaces: Mylar film, smooth steel, and roughened steel. Two sheets of the same compound were then bonded together by crosslinking them in contact. Measurements of peel strength were carried out over a range of temperatures from −40°C to + 130°C. When an uncured sheet was crosslinked in contact with a smooth fully-cured sheet, the peel strength was generally lower than the tear strength of either sheet and the degree of interlinking was inferred to be only about one-half of the degree of crosslinking. On the other hand, when a sheet was cured in contact with a rough surface the strength of adhesion was 2× to 3× higher than with a smooth surface, probably because of increased area for bonding. Thus, when a rubber compound was cured in contact with a fully-cured sheet having a roughened surface, the two effects largely cancelled out and the resultant bond was about as strong as the material itself. Examples are given for carbon-black-filled and unfilled compounds based on polybutadiene, a styrene-butadiene copolymer, and natural rubber.
Mechanical Behavior of a Solid Composite Propellant during Motor Ignition
Authors: Traissac Y. , Ninous J. , Neviere R. , Pouyet J. 
Published: February 2011

Abstract
In order to understand the behavior of composite propellants during motor ignition, a particular study about mechanical and ultimate properties of a Hydroxy-Terminated Polybutadiene (HTPB) filled propellant under superimposed hydrostatic pressure was carried out. The mechanical response of the propellant was obtained for uniaxial tensile and simple shear tests at various temperatures, strain rates and superimposed pressures from atmospheric pressure to 15 MPa. The experimentally observed ultimate properties were found to be strongly pressure sensitive and the data were formalized in a specific stress failure criterion.
Effect of Adhesion on the Equilibrium Swelling of Short Sisal Fiber Reinforced Natural Rubber Composites
Authors: Varghese Siby , Kuriakose Baby , Thomas Sabu , Joseph Kuruvilla 
Published: February 2011

Abstract
Solvent swelling of natural rubber composites, containing both untreated and acetylated short sisal fiber, has been investigated in a series of normal alkanes such as pentane, hexane, heptane and octane. The restriction on elastomer swelling exerted by sisal fiber as well as the anisotropy of swelling of the composite have been confirmed by this study. The results showed that increased fiber content and the addition of bonding agent reduced the swelling considerably. It has been demonstrated that with improved adhesion between short fiber and rubber, the factor, (VI−VF)/VI, decreases, where VI and VF are the volume fraction of rubber in dry and swollen samples, respectively.