bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Molecular-Weight, High-Unsaturation Copolymers of Isobutylene and Conjugated Dienes. II. Properties and Performance
Authors: Cohen H. , Rae J. A. , Buckley D. J. 
Published: February 2011

Abstract
Recent advances in cationic polymerization have resulted in the experimental production of a new class of isobutylene elastomers. These elastomers are copolymers of isobutylene with isoprene, piperylene, or cyclopentadiene with unsaturation levels up to about 40 mol%. Terpolymers can be made at similar unsaturation levels. Selected examples of these materials have been used to describe the general properties and also to investigate applications. The new compositions and structures exhibit a wide range of properties not attainable to date in isobutylene type elastomers. The new properties, in a number of instances, indicate that these elastomers are useful for certain tire applications. The tire performance studies included adhesion, ozone and fatigue cracking, skid resistance, and resistance of barriers to stain migration.
Blends of Elastomers and Thermoplastics—A Review
Authors: Dunn J. R. 
Published: February 2011

Abstract
In blends of elastomers and thermoplastics one component may be regarded as reinforcing the other. Examples are enhancement of tensile strength, tear strength, abrasion resistance, and modulus of elastomers by thermoplastics and improvement of impact resistance and environmental stress-cracking resistance of thermoplastics by elastomers. Certain elastomer-thermoplastic blends are rapidly growing in importance as thermoplastic rubbers because they combine the processing characteristics of plastics with physical properties similar to those of vulcanized elastomers.
In-Place Cleaning of Rubber Curing Molds
Authors: Sommer J. G. , Grover H. N. , Suman P. T. 
Published: February 2011

Abstract
Causes of mold fouling and conventional methods for cleaning fouled curing molds are reviewed. These methods generally require removal of the mold from the press for cleaning, and can abrade the mold surface. This paper describes the nature of some of the deposits that build up in the mold, and a new technique for cleaning in the curing press. Undesirable deposits are removed by vulcanizing a mold cleaning compound in the dirty mold. The aminohydroxy additive in the compound releases the deposit, which is then removed with the vulcanizate. Infrared analysis established both the presence of deposits on a metal surface by several different rubber compounds and their removal after treatment with the mold cleaning compound. In-place cleaning of rubber curing molds offers distinct advantages over conventional cleaning methods.
Reactions in Crosslinked Polymers. 3. A Metal Mold for Collecting Volatile Products during the Crosslinking Reactions
Authors: Wewerka D. , Hummel K. , Inselsbacher W. 
Published: February 2011

Abstract
Most methods of chemical and physicochemical analysis require the materials to be in homogeneous solution. The examination of crosslinking reactions, therefore, is subject to experimental difficulties since covalently crosslinked products are necessarily insoluble, and at best, swellable. Frequently it is simpler to analyze the low-molecular-weight byproducts of the crosslinking reactions and, in this way, to obtain information about their course. The separation of low-MW products by extraction has been valuable in investigations of reaction kinetics. Volatile compounds can also be collected by evaporation. We have previously described apparatus for investigating polymer reactions in solvents (e.g. bromobenzene) from which the volatile products can be distilled off. The present paper shows how the byproducts of crosslinking that are volatile at practical vulcanization temperatures (100–200°C) can be isolated. Several possibilities can be considered: The reaction mixture in powder form might be reacted in a glass vessel, or the mixture in film form might be reacted in an appropriate apparatus (e.g. that described by Voigt and Krüger for oxidative degradation). Both of these methods fail to give test specimens suitable for the customary crosslink measurement methods (e.g. equilibrium swelling). Hence we choose to conduct the reaction in a specially designed metal mold.
The Mechanical Behavior of Short-Fiber-Elastomer Composites
Authors: Coran A. Y. , Hamed P. , Goettler L. A. 
Published: February 2011

Abstract
The measured elastic and strength properties of angle-ply composites of short fibers and rubber depend on test-piece geometry. In general, higher tensile moduli and strengths are obtained when plies are both thin and wide. Once the effects of test-piece geometry are taken into account, elastic properties can be calculated as functions of the properties of a single ply. Classical compliance transformation equations can be used. However, because of the invariance of shear modulus in aligned composites, the tensor transformation equations are somewhat simplified. Tensile strengths of off-axis unidirectional composite plates and balanced-angle plies can be fitted by Hill's criterion. Unidirectional composites tend to fail in the weakest mode, depending on the angle of stress, but laminating causes all principal stresses in a ply to be near their ultimate limit at the time of failure.
Effect of Temperature on the Course of Thiuram-Accelerated Sulfur Vulcanization
Authors: Ducháček V. 
Published: February 2011

Abstract
These results confirm the validity of our theory of thiuram-accelerated sulfur vulcanization supposing that ZnDMDC arising from TMTD and zinc oxide is the actual accelerator in this type of curing system. The formation of ZnDMDC from TMTD during the curing process affects particularly the slow crosslinking reaction. Therefore, the activation energy of slow crosslinking is in very good accordance with the activation energy of TMTD decrease, and its value differs significantly from the activation energies of fast crosslinking and degradation. Simultaneously, these facts answer the question why the shape of the cure curves depends strongly on the temperature of cure.
Functionality Distribution of Hydroxyl-Terminated Polybutadienes by Gel Permeation Chromatography. II. Measurements for Commercial Polymers
Authors: Baczek S. K. , Anderson J. N. , Adams H. E. 
Published: February 2011

Abstract
The study of molecular weight and functionality parameters of telechelic hydrocarbon-based prepolymers has received much attention in recent years owing to the influence that these parameters exert on the vulcanization and product properties. An excellent review of these systems has been presented by French. Previous work has been limited to the determination of the average functionality of the whole polymer or of fractions obtained by some appropriate fractionation procedure. Muenker and Law, for instance, used extensive column elution techniques for separating the various species and then determined the average functionality of the fractions. In the previous paper, we described a dual-detector gel permeation chromatography (GPC) method for simultaneously determining the molecular weight averages, molecular weight distribution, hydroxyl equivalent weight, functionality averages, and functionality distributions of hydroxyl-terminated polybutadienes. The method is based on the simultaneous use of a differential refractive index and ultraviolet GPC detectors to analyze the polymers before and after derivatization of the hydroxyl groups with phenyl isocyanate. In this paper, the method will be utilized to determine these parameters for several commercial hydroxyl-terminated polybutadiene prepolymers and to compare the data with existing literature values.
Sequence Distribution of Polyisoprenes
Authors: Tanaka Y. , Sato H. 
Published: February 2011

Abstract
Isoprene can be polymerized into four types of isomeric structures; cis-1,4, trans-1,4, 3,4, and 1,2, depending on catalysts and polymerization conditions. So far, the difference of mechanical and thermal properties among polyisoprenes has been discussed chiefly on the basis of amounts of these isomeric structures. However, it is quite reasonable to expect that the polymer properties are affected not only by the composition of isomeric structures but also by the distribution of isomeric structures, the arrangement of head and tail linkages, and the degree of branching. This idea was adopted by Hackathorn and Brock as an explanation of the poor crystallizability of lithium polyisoprene; i.e. head-to-head and/or tail-to-tail linkages of 1,4- and 3,4-units prevented the crystallization of the polymer. Pyrolysis-gas chromatography has been applied to the investigation of the sequence distribution of 1,4- and 3,4-units in polyisoprenes. This method is based on the structural relationship between the isoprene dimers and the diad sequences of 1,4- and 3,4-units. However, it is difficult to discuss the slight differences in the yield of each dimer because the absolute amount of the dimers is small (∼30%) compared to the isoprene monomer (∼65%). Ozonolysis has been used to measure the amount of head-to-head, head-to-tail, and tail-to-tail linkages of the 1,4-unit in polyisoprenes. This method, however, is limited to the detection of these linkages of 1,4-units. In a previous paper, we have investigated 13C NMR spectra of chicle and cis-trans isomerized polyisoprenes and determined the sequence distribution of cis-1,4- and trans- 1,4-units in these polymers. We have also studied 13C NMR spectra of hydrogenated polyisoprenes prepared with n-BuLi-Et2O catalysts and found that 1,4- and 3,4-units were distributed randomly along the polymer chains regardless of the amounts of 3,4-units. In the present investigation we prepared various types of polyisoprenes and discussed the distribution of 1,4-and 3,4-units, arrangements of head and tail linkages, the branches of polymer chains, and the tacticity of polyads of 3,4-unit by the use of 13C NMR spectra of hydrogenated polyisoprenes.
Randomly Branched Polymers. II. Computer Analysis of Gel-Permeation Chromatograms
Authors: Kurata M. , Okamoto H. , Iwama M. , Abe M. , Homma T. 
Published: February 2011

Abstract
An iterative computer method was proposed for estimating the degree of branching and molecular weight distribution simultaneously from a pair of measurements on intrinsic viscosity and gel-permeation chromatography. The validity of the method as applied to randomly branched polymers was tested by using both fractionated and unfractionated samples of branched polystyrenes. It was experimentally concluded that the average number of branch points per unit molecular weight, λ, can be determined by this method with an accuracy of about 15%, and the weight-average molecular weight with accuracy of about 10%.
Effect of Curing Temperature on the Technical Properties of Nitrile Rubber and Carboxylated Nitrile Rubber
Authors: Bhowmick A. K. , De S. K. 
Published: February 2011

Abstract
In a mixed crosslink system (sulfur and metal carboxylate) of XNBR vulcanizate, the variations of the proportions of curatives (low sulfur/high accelerator or high sulfur/low accelerator) have little effect on the vulcanizate properties. But aging studies indicate that the metal ion crosslinks are modified in the presence of a sulfur vulcanizing system. NBR vulcanizates with a comparable recipe have less crosslink density than the corresponding XNBR ones. In general, the technical properties and aging resistance of mixed crosslink systems using ZnO2 and sulfur donor-sulfur are better than the NBR vulcanizates. Increase of curing temperature does not always lower the technical properties of XNBR and NBR vulcanizates. Addition of XNBR to NBR in XNBR-NBR blends lowers most of the technical properties, possibly due to different vulcanization characteristics.
Molecular Interpretations of Modulus and Swelling Relations in Natural Rubber Cross-Linked by Dicumyl Peroxide
Authors: Wood Lawrence A. 
Published: February 2011

Abstract
A survey of published experimental work on the modulus of natural rubber crosslinked by dicumyl peroxide permits a comparison with the results and molecular interpretations obtained in recent NBS work. Excellent agreement was found among values of the shear modulus G at the same crosslinking when the crosslinking is calculated from the amount of decomposed dicumyl peroxide. The types of deformation included torsion as well as uniaxial extension and compression. G increases linearly with crosslinking (except at the lowest degrees) with a slope from 5 to 15 percent greater than that predicted by the simple statistical theory. Data of Mullins demonstrated that at each degree of crosslinking the value of G is intermediate between 2C1 and 2(C1+C2) where C1 and C2 are the Mooney-Rivlin constants. Measurements of equilibrium swelling at a given degree of crosslinking are in reasonable agreement with each other. However, the entropy components of the modulus and the sub-chain density calculated from swelling measurements are appreciably greater than those calculated from crosslinking or from direct mechanical measurements. They increase linearly with crosslinking. It is concluded that the number of sub-chains effective in limiting swelling is greater than that effective in direct mechanical measurements.
Natural Rubber Foundation Bearings for Earthquake Protection—Experimental Results
Authors: Derham C. J. , Thomas A. G. , Eidinger J. M. , Kelly J. M. 
Published: February 2011

Abstract
The concept of earthquake protection of civil engineering structures by the use of rubber mountings of low shear stiffness has been discussed by Derham, Wootton, and Learoyd. Figure 1, taken from these references, shows the predicted response of a five-story shear-wall structure to an earthquake having a peak ground acceleration of 0.3 g. The accelerations shown at the various mass levels have been computed both for the building with its foundation fixed conventionally, and for the building “floating” on natural rubber bearings. The bearing stiffness was such as to make the horizontal natural frequency of the mounted structure 0.5 Hz. The basis of computation was the response spectrum of Housner. The results were later confirmed further by using a time-history analysis. The basic conclusion from these computer studies was that the use of rubber mountings leads the building to behave in an earthquake essentially as a rigid body. The rigid body accelerations, and hence the forces, are very much smaller than the accelerations experienced by a fixed-foundation structure, particularly in upper storys. For the case studied the overall maximum acceleration of the rubber-mounted structure was calculated to be one-tenth the maximum acceleration experienced by the fixed-foundation structure.
New Methods for Estimating Dispersibility of Carbon Blacks in Rubber
Authors: Jansen Jay , Kraus Gerard 
Published: February 2011

Abstract
Two convenient experimental methods are described for ascertaining dispersibility characteristics of carbon black. Both are based on the rate of development of optical density with dispersion or mixing time in a dilute suspension. One procedure uses polybutadiene medium and a roll mill to effect dispersion, the other chloroform and ultrasonic agitation. Correlations with conventional dispersion test results based on photomicrography are good. Advantages are precision and objectivity, not available to the same degree in photomicrograph evaluations.
A New Concept of Tire Load Inflation Formulae
Authors: Zheng-ren Z. 
Published: February 2011

Abstract
Since World War II the size and number of vehicles has increased greatly. Passenger cars have greater power and acceleration, whereas truck tires carry heavier loads at greater speeds. Earthmover vehicles now have heavier loads as well as greater traction. To keep up with the demands of the automotive industry, tire technologists have had to change from cotton and rayon cord to nylon, polyester, steel and aramid. Tire construction has changed from the conventional high aspect ratio to a lower one and from bias to radial design. A difference in thinking between European and American tire technologists appears based on different concepts of single and dual load capacities. The Americans (TRA) base their calculations on the dual load while the Europeans (ETRTO) base theirs on single load. This is not the principal argument, since both can use dual or single as the basis of calculating the tire load. Some do not believe in load calculation formulas; instead, they rely on their experience and estimation. It is not scientific to “estimate” the load of a tire by experience.
Molecular Fracture in Polychloroprene
Authors: Mead W. T. 
Published: February 2011

Abstract
The ESR spectra from polychloroprene uniaxially deformed at 77 K in an oxygen environment are composite spectra arising from two radical species. An allyl radical species results from main-chain rupture midway between the α-methylene groups, and a peroxy radical species is formed by reaction of the oxygen in the environment with the allyl radical species. The stability of these allyl radicals with respect to oxygen and temperature is apparently similar to the allyl radicals formed in polybutadiene and polyisopropene. At liquid nitrogen temperature all the radicals were stable. The peroxy radical species is unstable as Tg is approached and decays to give a resonance-stabilized allylic species, which is stable until the temperature of the sample is slightly above Tg. Above Tg a broad singlet is observed, and it is attributed to a polyenyl radical species.
Contribution of Power Profiles to Mixing Efficiency
Authors: Dolezal P. T. , Johnson P. S. 
Published: February 2011

Abstract
Our studies have shown that, on a laboratory scale, power curves can be used to elucidate the processes involved in mixing butyl rubber compounds. Through an understanding of the process and the construction of mixing profiles, it is possible to optimize mixing efficiency. In a production environment, power curves can obviously be of great value in monitoring quality control.
Scanning Electron Microscopy Studies of Fractured Natural Rubber Surfaces
Authors: Bhowmick A. K. , Nando G. B. , Basu S. , De S. K. 
Published: February 2011

Abstract
A tensile ruptured gum specimen shows formation of crystalline regions at an angle of 45° to the flow lines, whereas a tensile ruptured filled specimen shows formation of depression. A tear fractured gum specimen shows again the formation of crystallites at an angle of 45° to the flow lines. Tear fractured filled specimens show the enhancement of crystallinity throughout the matrix, but the surface is rough. Flex fractured gum specimen show a large number of cracks on the surface while the filled vulcanizate shows formation of balls presumably due to coiling of polymer chains on the filler surface. An abraded gum surface shows dimple structure, while a filled vulcanizate indicates coarse ribbed structure. Addition of lignin, in general, reduces the crystallinity of tensile and tear fractured samples and increases the fibrosity of flex cracked and abraded samples.
New Factors Affecting the Performance of Automotive Fuel Hose
Authors: Pfisterer H. A. , Dunn J. R. 
Published: February 2011

Abstract
The permeation of fuels through fuel hose compounds based on medium acrylonitrile NBR increases with aromatic content. Addition of low molecular weight alcohols as fuel extenders has an adverse effect on swelling and permeability, which is most marked at levels of 10–20%. NBR is resistant to unblended alcohols. Addition of tertiary butyl alcohol at levels up to 7% for improved octane rating does not adversely affect NBR. High acrylonitrile NBR and NBR-PVC blends have lower permeability to and greater resistance to swelling by aromatic fuel. They also exhibit improved resistance to swelling by alcohol modified fuel. XNBR has somewhat lower fuel permeability than regular NBR. A two-component fuel hose composed of a veneer of high acrylonitrile NBR, NBR-PVC or XNBR-PVC with the highest practical acrylonitrile level inside a medium acrylonitrile NBR is suggested as a route to satisfactory permeability and low temperature performance.
Polymerization of Diene Monomers by Ziegler Type Catalysis
Authors: Horne S. E. 
Published: February 2011

Abstract
I have not gone into compounding and testing results on polyisoprene and polybutadiene. As you well know, they are widely used in the rubber industry. From a technical standpoint, we know we can replace natural rubber with cis-polyisoprene. However, the profitability of the process is closely tied to the availability of isoprene monomer and the price ratio of cis-polyisoprene and natural rubber. Sometimes the economics is favorable and sometimes unfavorable. Consequently, polyisoprene expansion is slow in the Free World. In the Communist countries, however, the planned economy is pushing ahead with polyisoprene—projections for 1985 are for 817 000 metric tons versus 227 000 metric tons in the Free World. Is there a possibility of an entirely new synthetic rubber that will be the equal of polyisoprene, but more economical? Is there a blend of elastomers that will replace natural? Is there a chance the economics of polyisoprene might become more favorable? Certainly the answers pose a challenge to those of us in research. We cannot sit back and say we have reached the ultimate, for the world of the tire is constantly changing, and we must be able to meet the change. The work reported here could not have been carried out without the invaluable contributions of my colleagues at BFGoodrich. I wish to especially mention: Jim Shipman and Jack Kiehl for the early infrared work and claiming that I was trying to fool them with my first copolymer; Vern Folt, the enthusiastic section leader for the early project ; Earl Carlson, who elucidated the conditions for making trans-polyisoprene and trans-polybutadiene ; Dave Craig for supplying the pure isoprene for the early work; Bob Minchak and Harold Tucker for some of the cobalt studies and titanium studies; Harvey Scott for the cobalt chloridealuminum chloridethiophene catalyst; Ed Wilson and M. Reinhart for compounding studies; Waldo Semon and Carlin Gibbs for directing it all and allowing us such a free hand; Floyd Miller, who did such an outstanding job of scaling the process directly from a 50 g lab recipe to production size runs; and the numerous, capable technicians who have worked for me— they are the unsung heroes of the laboratory work. Let me say again how highly honored I feel to receive this award. I am accepting it for all at BFGoodrich, for it was truly a team effort.
Experimental Studies of the Influence of Particle and Fiber Reinforcement on the Rheological Properties of Polymer Melts
Authors: White James L. , Czarnecki Lech , Tanaka Hideho 
Published: February 2011

Abstract
An experimental study is reported on the rheological properties of compounds of a polystyrene melt with calcium carbonate, carbon black, titanium dioxide, calcium sulfate anhydride fiber, mica, glass beads and aramid, cellulose and glass fibers. Comparison is made of the shear viscosity, elongational viscosity and principal normal stress difference of these compounds at 20 volume per cent loadings. The polymer matrix and compounds with the smallest particle dimension greater than 10µ exhibit low shear rate Newtonian viscosities. Suspensions with particle sizes 0.5µ and smaller exhibit yield values. Yield values are also observed in elongational flow for systems exhibiting yielding in shear flow. The experimental data are contrasted to both mechanistic theories of suspensions with interaction between particles and a phenomenological plastic-viscoelastic tensor constitutive equation.