bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoanalytical Methods in Vulcanizate Analysis II. Derivative Thermogravimetric Analysis
Authors: Brazier D. W. , Nickel G. H. 
Published: February 2011

Abstract
We have shown in this and the preceding paper that fully compounded stocks can be analyzed for all main constituents by use of a combination of DSC, TG, and DTG. Further, this can be achieved on a time scale consistent with routine quality control. DSC gives information on cure characteristics, sulfur, and accelerator levels in approximately five minutes. Elastomer, elastomer ratio, carbon black, oil/plasticizer, and inorganic pigments are determined in about 35 minutes by TG/DTG, at a scan rate of 10°C/min. This time can be reduced by increasing the scan rate, but interference from highly exothermic reactions can be a limiting factor. Each compound must be treated individually to determine the maximum scan rate that can be used without impairing reproducibility. Clearly limitations exist for identification of unknown blends by DTG. The main problem is that many commercial elastomers have very similar thermal stabilities, which results in DTG peaks in the same temperature range. Further work is being undertaken with the DTG—gas chromatography interface to identify not only the pyrolysis products, but the temperature range over which they are evolved. In this manner, the DTG acts essentially as a thermal fraetionation unit and GC analysis of products from a given component in a blend can be achieved.
Thermal Degradation of Copolymers of Butadiene and Acrylonitrile
Authors: Grassie N. , Heaney A. 
Published: February 2011

Abstract
Copolymers and polymer and copolymer blends incorporating two or all three of the monomers, acrylonitrile, butadiene, and styrene, have become important commercial materials. It is therefore important to have information about their stability toward the various degradative agencies. A description of the thermal degradation of copolymers of styrene and acrylonitrile has been given; this paper extends this work to the butadiene—acrylonitrile copolymer system.
Advances in Catalysts Based on Aluminum Hydride Derivatives for the Synthesis of High-Cis Polyisoprene
Authors: Balducci A. , Bruzzone M. , Cucinella S. , Mazzei A. 
Published: February 2011

Abstract
The stereospecific polymerization of isoprene with simple alanes and poly (N-alkyliminoalanes) (PIA) and TiCl4 is critically reviewed and related to the more recent finding on the “cage” structure and composition of PIA's. In particular, the polymer yield was found strictly dependent on the structure of the PIA, which in turn depends on the nature of the alkyl groups bonded to nitrogen. The effects of the chemical composition of the PIA and of the halogen level in its halogenated derivatives on the activity of the catalyst and on the possibility of side reactions is discussed with reference to conventional aluminum alkyl catalysts. The identification of new structures within this class of cocatalysts is discussed
Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Polymers. Part IV. Peak Assignment for Styrene-Butadiene Copolymers
Authors: Katritzky A. R. , Weiss D. E. 
Published: February 2011

Abstract
The low-field region of styrene-butadiene copolymer spectra provides little information because of overlap of peaks and broad representation of diads. The high-field region gives much useful information. From our data and our assignments, we are now proceeding to interpret the microstructure of styrene-butadiene copolymer in terms of diad composition and average run lengths for block styrene and block butadiene Our 13C nmr studies of copolymers show the broad application of this technique for revealing detailed structural information in both vinyl and non-vinyl continuous polymer chains. Previously, tacticity (configuration) and unit sequence both have been indicated in triad (3 unit) resolution for a copolymer of two repeating units and now nearly complete diad resolution is obtained for a copolymer with 4 individual repeating structural units.
The Reaction of t-Butyllithium with Styrene and Isoprene. A Comparison of Chain Initiation with the Isomers of Butyllithium
Authors: Roovers J. E. L. , Bywater S. 
Published: February 2011

Abstract
The use of lithium alkyls as polymerization initiators provides an important method for the production of monodisperse polymers. Surprisingly large differences in initiation rates are observed between straight and branched chain lithium alkyls. s-Butyllithium, for example, initiates several powers of ten more rapidly than n-butyllithium in benzene. Less work has been carried out on t-butyllithium. Hsieh has reported that in cyclohexane the order of efficiency (defined as more complete initiation at lower monomer consumption) is s- &gt; t- &gt; n-butyllithium for the dienes and s &gt; n- &gt; n-butyllithium for styrene. These experiments were carried out using commercial products, and it seemed of interest to repeat these experiments on purified materials as the reactions of lithium alkyls are known to be sensitive to impurities. In addition the exchange reactions of t-butyllithium with other alkyls are known to be slow whereas those of n- and s-butyllitbium are considerably faster. If, as suggested, the slow exchange rate is determined by the rate of dissociation of the predominantly tetrameric t-butyllithium, then it seemed likely that, at least in benzene, some differences in initiation behavior might be expected. In this solvent the initiation mechanism has been suggested to involve a prior dissociation of the aggregates. The rate of addition of t-butyllithium to 1,1-diphenylethylene has already been studied in benzene. At very low monomer concentration, the reaction order in initiator was found to be 0.25, which suggests the dissociative mechanism holds under these conditions. We have, therefore, studied the reaction of t-butyllithium with isoprene in benzene and hexane and with styrene in benzene and cyclohexane. The use of aliphatic hydrocarbon solvents produces quite different initiation behavior to that in aromatic solvents.
Particulate Reinforcement of Polyacrylate Elastomers. II. Mechanical Properties
Authors: Blackley D. C. , Sheikh M. W. 
Published: February 2011

Abstract
This paper presents and discusses the mechanical properties of crosslinked poly (ethyl acrylates) containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. That the adhesion is affected by surface treatment has been demonstrated in two ways: (1) Unfilled elastomer sheets have been cast in contact with glass surfaces which had been treated with the same reagents as the beads. The force required to peel the elastomer from the glass was then measured and found to depend strongly upon the surface treatment. (2) Scanning electron micrographs of the ruptured surfaces of used tensile test pieces cut from filled elastomer sheets confirm that surface treatment has a profound effect upon the adhesion between bead and matrix. Results are presented for the hardness and tensile stress-strain properties of elastomers containing various amounts of beads. In all cases, the stiffening effect of the beads increases as the adhesion between beads and matrix is improved. Beads which had been treated in such a way as to minimize the adhesion to the matrix were found to cause an apparent softening of the material as revealed by the tensile stress-strain curve. It has been shown that this effect can be satisfactorily explained if it is assumed that in this case the beads merely serve to increase the void content of the material.
Particulate Reinforcement of Polyacrylate Elastomers. III. Swelling Measurements
Authors: Blackley D. C. , Sheikh M. W. 
Published: February 2011

Abstract
This paper presents and discusses results which have been obtained for the swelling in chlorobenzene of crosslinked poly (ethyl acrylates) containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. The swelling behavior has been found to correlate very closely with the extent of adhesion as judged by peel force measurements and tensile stress-strain properties reported previously. In the case of beads showing pronounced adhesion to the matrix, restrictions on swelling have been interpreted in terms of an apparent enhancement of crosslink density by the reactive beads.
Radiation-Induced Crosslinking of Chlorobutyl and Polydiene Elastomers. Promotion by Polythiols
Authors: Zapp R. L. , Oswald A. A. 
Published: February 2011

Abstract
The response of Chlorobutyl (CIIR), an elastomer with 1,1-disubstituted carbon atoms along the polymer chain, to ionizing radiation has been directed toward a predominantly crosslinking reaction by addition of 1–4 phr of thioetherpolythiols (TEPT) prepared by reaction of trivinylcyclohexane or cyclododecatriene with H2S or low-molecular-weight dithiols. From a fundamental viewpoint, the unique feature of the CIIR-TEPT system is the reversal of expected behavior for a polymer molecule containing 1,1-disubstituted carbon atoms when exposed to high energy radiation: instead of chain scission, cross-linking is the predominant physical change to an extent comparable to that obtained from thermal curing processes. The TEPT becomes part of the radiation-cured network, for, as the radiation dose is increased, there is progressive addition of thiol sulfur to the crosslinked network. Concomitantly, there is a progressive reduction in the chlorine content as radiation-induced vulcanization proceeds. These polythiols are also powerful accelerators of radiation-induced cross-linking of polydiene elastomers, especially those with appreciable amounts of pendent vinyl unsaturation, such as conventional SBR. Evidence exists that a blend of CIIR and SBR can be covulcanized by radiation-induced curing in the presence of TEPT. Experiments were conducted with gamma radiation from a 60Co source and with a 1.4 MeV electron beam at dose rates of 20–120 kJ/kg (2–12 megarads). Physical properties of fully compounded polythiol-promoted CIIR systems crosslinked by radiation are lower than comparable thermally cured compounds, but the strengths would be adequate for many applications. Compounding ingredients, especially common accelerators of sulfur vulcanization, provide a wide range of inhibitory action toward radiation precure. However, with selected types, especially organometallic derivatives which are less soluble in the compound, radiation cure can proceed with a minimum of inhibition.
Factors Influencing the Strength of Rubbers
Authors: Thomas A. G. 
Published: February 2011

Abstract
The strength behavior of rubbers is discussed in terms of fracture mechanics which treats fatigue and tensile failure as crack growth processes from small flaws. Crack growth can be influenced by the presence of oxygen or ozone. The nature of the vulcanizing system affects strength : crosslinks probably rupture and reform under stress. A new approach to the problem of abrasion is presented using fracture mechanics. Schallamach has shown that rubber often develops a pattern of ridges perpendicular to the direction of abrasion. In the simplest case abrasion is produced by a line contact (e.g., a razor blade) which pulls a tongue of rubber from the ridge producing crack growth at the base of the tongue. Provided the surface configuration is in a steady state, the quantity of rubber abraded can be related quantitatively to the frictional force and the crack growth characteristic of the rubber on some reasonable assumptions. Good agreement with experiment is found for noncrystallizing rubbers but the behavior of strain crystallizing natural rubber suggests that crystallization cannot occur under the conditions used so that the rubber is not strengthened by this means.
Viscoelastic Properties of Rubber Networks
Authors: Thirion P. 
Published: February 2011

Abstract
The molecular theory of Rouse, Zimm, and Bueche correctly accounts for the viscoelastic properties of polymers in very dilute solution and, to a large extent, for those of polymers in bulk or in concentrated solution, as long as their mean molecular weight is below about 20 000. Above this MW limit, relaxation times appear which are longer than those provided for in this theory. The “viscoelastic plateau”, which then appears in the long relaxation time region of the dynamic spectrum, is ascribed to entanglements of molecular chains which behave like temporary crosslinks. An analogous phenomenon occurs in the same way in permanent polymer networks, such as rubber vulcanizates. In this case one finds abnormally slow relaxation or creep rates during the approach to equilibrium, as well as increased low-frequency mechanical energy losses under forced sinusoidal vibration. The presence of colloidal fillers, such as carbon blacks used to reinforce rubbers, also seems to increase this hysteresis within the polymer matrix, independent of thixotropic effects which result from the reversible rupture of filler particle aggregates under large-amplitude cyclic deformations. We propose to analyze here the results (obtained jointly at the Institut Français du Caoutchouc and at the laboratory of Professor J. D. Ferry, University of Wisconsin) of measurements over the entire rubbery spectrum of the dynamic properties and of stress relaxation on vulcanizates of natural rubber, cis-polybutadiene, and styrene-butadiene copolymer (SBR) in the absence of secondary crystallization or aging phenomena. Then we examine the interpretation of the behavior of these materials, both at low frequency and during the approach to equilibrium, by analogy with the theories of the “viscoelastic plateau” of linear polymers.
Structural Characterization of Vulcanizates. I. Crosslinking Efficiency of Sulfur in Unaccelerated Natural Rubber-Sulfur Systems
Authors: Moore C. G. , Mullins L. , Swift P. McL. 
Published: February 2011

Abstract
This paper deals with the determination of crosslinking efficiencies of sulfur in a series of unaccelerated XR-sulfur vulcanizates produced at 140° C. The method used is that described under (1) above, values of the degree of chemical crosslinking being derived from stress-strain measurements on the unextracted vulcanizates.
New Vulcanizing Systems for Ethylene-Propylene Elastomers
Authors: Wei Peter E. , Rehner John 
Published: February 2011

Abstract
The absence of chemical functionality in ethylene-propylene elastomers precludes crosslinking with conventional rubber vulcanizing agents. It is known that such elastomers can be vulcanized with combinations of sulfur and certain organic peroxides, but the resulting vulcanizates leave something to be desired from the standpoint of tear strength, odor, and peroxide cost. A chemical study of the reaction between isoparaffins, sulfur, and organic peroxides gave results showing that some important alterations must be made of previous views that have been advanced for the vulcanization of saturated hydrocarbon elastomers by peroxides alone. A new reaction scheme is briefly reviewed. In the course of this study, three new classes of substances have been discovered to be effective vulcanizing agents for ethylene-propylene elastomers, and for other rubbers also. The outstanding characteristics which these new agents produce in ethylene-propylene elastomer vulcanizates are excellent tear strength and no objectionable odor. Data are presented on some properties of vulcanizates prepared with these agents.
Vulcanization of Rubber in the Presence of Organic Accelerators
Authors: Dogadkin B. A. , Shershnev V. A. 
Published: February 2011

Abstract
Rubber Reviews for 1957 included an extensive survey by Craig devoted to the vulcanization of rubber with sulfur. In that survey, however, neither the thinking of Soviets nor of Germans were mentioned; likewise Japanese studies, of which a considerable number had been published in the preceding decade, were omitted. The purpose of the present survey is to supply, in some degree, the deficiency of the Craig review, particularly that part which deals with the problem of the chemistry of vulcanization of rubber by means of sulfur in the presence of accelerators. In recent years the attention of investigators, engaged in the study of vulcanization, has been focused chiefly on the clarification of elementary chemical reactions of the process, on the mechanism of the action of accelerators and on the establishment of the nature of vulcanization structures and their influence on physicomechanical properties of the vulcanizates. For the resolution of these questions, along with chemical analysis methods, attention is drawn to the physical methods of optical and electron microscopy, of isotope interchange, and of analyses of kinetics by means of radioactive sulfur. Important results were obtained through the study of sulfur in model low molecular weight compounds. Furthermore, it has been demonstrated that there are two tendencies toward interpretation of the general nature of chemical reactions of sulfur with rubber. In some studies, radical processes are assigned an important role in the explanation of structural changes in rubber during vulcanization; in others, elementary reactions are considered as proceeding in accordance with a polar (ionic) mechanism. It occurs to us that the differences in points of view, regarding the mechanism of vulcanization, are not so much a matter of approach to the interpretation of experimental factors, as this fact—that for such a complicated phenomenon as vulcanization, it is impossible to support a single mechanism. The mechanism of a reaction may vary, depending on thermodynamic considerations with regard to the reaction, the type of rubber used, and especially on the types of accelerators and activators employed. Such a conclusion was reached also by Shelton and McDonel. For this reason, in this survey we shall present material representing a number of individual viewpoints regarding vulcanization along with a discussion of some general features.
An Electron Microscope Reinforcement Criterion for Carbon Black Masterbatches
Authors: Prestridge Eddie B. 
Published: February 2011

Abstract
With the advent of wet masterbatching methods, which provide a preliminary dispersion of carbon black in latex, techniques for the microscopic evaluation of the quality of this incorporation proved inadequate. Three reinforcement criteria were developed for such evaluations: dispersion, grinding, and bonding. Using these criteria the performance characteristics of a tread stock made with such masterbatches can be predicted with good reliability. The correlation of reinforcement criteria and the raw Mooney of the masterbatch reveals the striking effect of improved carbon black incorporation on this property. Using this correlation it should be possible to evaluate masterbatch production on a continuous basis.
Swelling and Network (Crosslink) Density of Carbon Black-Filled Natural Rubber Vulcanizates
Authors: Westlinning H. , Butenuth G. 
Published: February 2011

Abstract
The method cited by W. Kuhn and coworkers for the determination of network densities on the basis of a thermal analysis of swollen samples has been applied to unfilled and carbon black-filled natural rubber vulcanizates. The results with unfilled rubber on the basis of the new method are in the expected correlation with the measurements of the degree of swelling and the modulus of elasticity. From the results with carbon black-filled samples it is probable that an inhomogeneously crosslinked system is formed under the influence of the filler. It is concluded that there are regions of high network density adjacent to regions of low density. Consequently, the degree of swelling, referred solely to the rubber portion, is to be considered a mean value in the case of filled vulcanizates from which the network density cannot be deduced without additional measurement.
Estimation of Wear Resistance of Tread Vulcanizates
Authors: Gelinas L. P. , Harris I. W. E. , Storey E. B. 
Published: February 2011

Abstract
A simple procedure has been described to provide an estimate of the wear characteristics of a vulcanized polymer by means of a towing device. The present paper describes modifications that have been adopted to increase the efficiency of this procedure and reports the effect of various test conditions that have been explored by statistical methods. Estimates of the wear resistance of various types of rubber in suitable tread recipes are given together with an observed order of rating based upon their response to the severity of the imposed conditions.
Rubber Structure and Coefficient of Friction
Authors: Bartenev G. M. 
Published: February 2011

Abstract
1. As a result of analysis of the formulas of friction of rubber and of a comparison with experimental data for steady-state friction on smooth solid surfaces it is demonstrated that the friction of vulcanized rubber is determined by three constants of the material, depending upon the type of rubber polymer and the structure of the vulcanizate. 2. The constant α characterizes the constant of the formation of the area of actual contact Sa under loading. This constant does not depend upon the rate of slip and the nature of the solid surface, but it does depend upon the stiffness of the vulcanizate, which is directly proportional to the crosslink density. 3. The tangential stress on the actual area of contact α=F/Sa depends upon the temperature, the rate of slip and the two constants of the material Sk and U. The first of these is the effective area of contact of a chain with the solid surface, depending upon the number of chains in the network of the vulcanizate, the second is the activation energy, depending upon the nature of the frictioning surfaces, in particular upon the structure of the polymer chain of rubber. 4. A method is proposed for calculating the area of actual contact of a vulcanizate from the number of chains per unit volume and from the number of chains which are in contact with the solid surface.
Measurement of Friction between Rubber-Like Polymers and Steel
Authors: James D. I. 
Published: February 2011

Abstract
A machine for measuring the coefficient of friction between a flat sheet of polymeric material and a ground steel plate is described in detail. An inverted lathe cross slide forms the basis of the drive mechanism. Frictional force is balanced against the tension developed in a spring (proof ring), the extension of which measured with a commercial displacement pickup, gives a direct reading of coefficient of friction. A few results are given for a PVC sample plasticized with 40% dioctyl phthalate. A circuit for automatic operation and recording is also described.
Calculation of the Behavior of Rubber-Covered Pressure Rollers
Authors: Parish G. J. 
Published: February 2011

Abstract
Data are given which enable the properties of nips between metal and rubber-covered pressure rollers to be calculated from the parameters of the system. The properties with which the calculation is primarily concerned are the nip width and the mean pressure in the nip, but the principle can be extended to include the peak pressure and the distribution of pressure through the nip. The calculation is based on the well-known Hertzian formula and on empirical relations, which express the important effects of the rubber-cover thickness. The data refer not only to roller systems in which the loading is uniform, but also to non-uniform nips, in particular to those which show what is probably the commonest cause of non-uniformity, roller deflection. Although the calculations refer primarily to nips between one hard roller and one relatively soft, covered, roller, they are directly applicable to nips between two identical covered rollers and may be applied, within limits, to systems in which the rollers are dissimilar in properties.