bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Relationship of Properties of Synthetic Poly(Isoprene) and Natural Rubber in The Factory. The Effect of Non-Rubber Constituents of Natural Rubber
Authors: Gregg E. C. , Macey J. H. 
Published: February 2011

Abstract
The causes of some of the differences in properties between compounded natural rubber and compounded synthetic poly (isoprene) have been traced to the insoluble non-rubber material in natural rubber. This material is mostly denatured proteins and is responsible for the higher modulus, faster scorch time, higher heat buildup, and higher hot tear strength of natural rubber. These properties may be related to the pigment effect of the denatured protein to act as a reinforcing filler at low concentrations (3–4 per cent by wt) as well as a curing activator. The greater green strength of compounded natural rubber has been related to its more perfect configurational regularity which contributes to faster crystallization. The crystallite concentration increases with increasing stress and the crystallites act like a reversible reinforcing pigment which disappears when the stress is released. The faster plastication rate has been related to the synthetic stabilizers used. Natural rubber hydrocarbon has been shown to be a high molecular lactone arranged in a six membered ring. We speculate natural rubber forms as a prosthetic group connected through a lactone linkage (or the δ-hydroxy acid precursor to the lactone) to a protein molecule in the cell of hevea brasiliensis. It is this structure of a high molecular weight hydrocarbon (natural rubber) attached to a (denatured) protein molecule that accounts for the remarkable dispersability of the insoluble fraction of natural rubber in rubber solvents : the rubber end of the structure tends to dissolve in the rubber solvent while the highly polar, insoluble protein end prevents solution. This structure is the reverse of a micelle in water in principle.
Rubber Chemicals from Cyclic Amines. VII. Cycloalkylthioamines as Accelerators and Prevulcanization Inhibitors
Authors: Morita E. , Boustany K. , D'Amico J. J. , Sullivan A. B. 
Published: February 2011

Abstract
Cycloalkylthioamines per se are moderately active accelerators. When used in conjunction with the benzothiazole accelerators, these thioamines act as prevulcanization inhibitors with cure activating properties, and generally, increase the crosslink density of the vulcanizates. The inhibition action of the cycloalkylthioamine may be due to its activity as a BtSH scavenger and also to its ability to reduce the number of the labile sulfur atoms, thereby the reactivity, of the more active polythiobenzothiazole intermediates. In addition to these capabilities the inhibition action of PVI in a benzothiazole sulfenamide-accelerated stock may be due to its ability to react with the free amine liberated during vulcanization. The relation of the curing properties of the cyclohexylthioamines to the structure of the amine moiety is analogous to the cases of dithiodiamines and 2-(imino)dithiobenzothiazoles as vulcanizing agents, or N-substituted-2-benzothiazole sulfenamides as accelerators. The relative curing properties either as accelerators or prevulcanization inhibitors can be attributed to the relative stability of the S-N bond based on the steric and electronic nature of the amine moiety. The cyclohexylthioamines derived from pyrrolidine and hexamethyleneimine are the most active as accelerators. The cyclohexylthioamine derived from the equally basic piperidine is slightly less active and gives significantly longer scorch delay. As a prevulcanization inhibitor the less basic morpholino and 2,6-dimethyimorpholino derivatives give much longer delayed action. The piperazine derivative is the most effective as a prevulcanization inhibitor.
Study of Crystallinity in Polymers by the Use of “Molecular Probes”
Authors: Guillet J. E. , Stein A. N. 
Published: February 2011

Abstract
Recent experiments in our laboratories have shown that the technique of gas chromatography can be utilized to obtain information about polymer structure and interactions in the solid phase. Although it might appear reasonable to apply the name “gas chromatography of polymers” to such experiments, the terminology is misleading in that the polymer is obviously not in the gas phase, nor is it undergoing a Chromatographic separation. The terms glpc (gas—liquid partition chromatography) and gspc (gas—solid partition chromatography) appear to be equally inapplicable. In fact the nature of the experiment has more in common with the molecular beam technique for gas reactions and we prefer therefore to refer to these as studies on polymers using “molecular probes.”
Gas—Liquid Chromatography on Polymers. II. Temperature Coefficients for Polyisobutylene—Hydrocarbons
Authors: Leung Yu-Kwan , Eichinger B. E. 
Published: February 2011

Abstract
Studies of the thermodynamics of polymer solutions by conventional static methods at very high concentrations of polymer are relatively few. Therefore, comparisons between enthalpy parameters obtained by the methods of glc and vapor sorption are limited to only a few cases. One other system for which comparable data are available is natural rubber and benzene. In this case, the glc value of κs is +0.18, while κs = 0.01 ± 0.1 has been obtained by vapor sorption. It appears from the somewhat sparse data collected to date that estimates of the residual enthalpy obtained by glc methods are as reliable as those obtained by static methods. Corrections for gas phase imperfection must be very carefully applied.
Some Novel Systems for Crosslinking Polychloroprene
Authors: Kato H. , Fujita H. 
Published: February 2011

Abstract
During the past three decades polychloroprene (CR), one of the earliest synthetic elastomers, has been widely used in many and varied technological applications. The established curing technique generally involves metal oxides as curing agents. The combination of ZnO and MgO with 2-mercaptoimidazoline (NA-22) as an organic accelerator is commonly used. Notwithstanding much work, the essential mechanism of the curing reaction is so complicated that many details remain to be resolved. An effective substitute for NA-22 has become desirable in Japan, mainly because of environmental pollution. Our search for novel organic accelerators has been stimulated by these circumstances and has resulted in the discovery of some promising candidates. This paper is concerned with these new accelerators for the vulcanization of CR and with certain chemicals which stabilize CR vulcanizates cured by them.
Strain-Dependent Dynamic Properties of Carbon-Black Reinforced Vulcanizates. I. Individual Elastomers
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
The degree of carbon—black particle aggregation (transient structure) in conventional vulcanizates varies with the nature of the elastomers. This is revealed by the variation of (Gm′−G∞ƒ′), which is a measure of the transient structure. The relationship between Gm″ and (Gm′−G∞ƒ′) as well as that between strain work and normalized modulus show similarity to earlier work in which the polymer type was not varied. This suggests that carbon-black structural elements act as energy storage units and are of the same type in all these polymers. While the decrease of in-phase modulus is primarily caused by carbon-black particle units, tan δ reflects also the effect of the polymeric matrix.
Quantitative Determination of the Polymeric Constituents in Compounded Cured Stocks by Curie-Point Pyrolysis—Gas Chromatography
Authors: Krishen Anoop , Tucker Ralph G. 
Published: February 2011

Abstract
Pyrolysis—gas chromatography has been shown to be an excellent technique for quantitative estimation of polymers. Its acceptance is apparent from the large number of publications reported in the past year. The increasing complexity of the constituents used in various applications has necessitated the use of more precise and sophisticated control over the experimental variables. The Curie-point pyrolysis technique has been able to provide a degree of control which has not been possible with any of the other pyrolysis techniques used. In this technique, the sample is heated in a helium stream to a precisely duplicable temperature which is dependent on the composition of the alloy used for the pyrolysis wire, the maximum temperature being the Curie-point when the ferromagnetic wire becomes paramagnetic and is thus incapable of absorbing any energy from the high frequency induction current source. The fast temperature rise results in more specific products on pyrolysis, and any contamination from previous samples can be avoided by using a new wire each time. Application of this technique to complex polymeric mixtures containing a large number of monomeric species is of considerable importance in establishing the composition of these mixtures. The ability to handle cured samples without any elaborate pretreatment makes this technique much more useful.
Structural Change Accompanied by Plastic-to-Rubber Transition of SBS Block Copolymers
Authors: Fujimura M. , Hashimoto T. , Kawai H. 
Published: February 2011

Abstract
It was shown that some block copolymers and their blends with corresponding homopolymers exhibit stress softening. When the specimens are stretched beyond the yield point, they become rubbery and exhibit high elasticity and large recoverable deformation, as a result of a breakup of their original rigid structure. Moreover, the deformed specimens heal, in that the properties of the original undeformed specimens are recovered upon removal of applied stress. This effect was attributed to the reformation of the original microdomain structure. In this work, we investigated an SBS block copolymer and a blend of the copolymer with homopolystyrene in regard to the structural change accompaning the plastic-to-rubber transition and the healing process. Electron microscopy and small angle X-ray scattering (SAXS) were used.
Strength of Elastomers. A Perspective
Authors: Smith Thor L. 
Published: February 2011

Abstract
The strength and extensibility of an elastomer depend on its overall viscoelastic properties, as reflected in the time and temperature dependence of stress-strain curves, and also on those discrete processes, including crack formation and growth, that culminate in high-speed crack propagation. The discrete processes determine the lifetime of a specimen; the viscoelastic characteristics affect the dependence of stress on deformation. The interplay between these effects causes strength and extensibility to depend strongly on test conditions. An elastomeric network composed solely of highly mobile chains is very weak indeed and fractures at a low elongation. This characteristic differs diametrically from that expected of an idealized network of mobile chains. If such a network were stretched, stress concentrations and unbalanced forces at the molecular level, which can result from short chains, entanglements, and network imperfections, would be vitiated rapidly by stress-biased segmental diffusion, especially at the elevated temperature. Therefore the network should be able to withstand a high elongation and thus a high stress. Hence, the low strength always exhibited by a single-phase non-crystallizable elastomer at elevated temperatures is incompatible with the characteristics ascribed to a network in the molecular theory of rubber elasticity. A network of mobile chains is weak for two reasons. First, microcracks develop readily in a stretched specimen. Their formation is usually attributed to stress concentrations near heterogeneties either within or on the surface of a specimen. Second, and most importantly, a microcrack—once it forms—encounters little resistance to growth because the chains are highly mobile. High strength results not because microcracks do not develop but because their growth is impeded. Unless processes that impede growth come into play, a microcrack enlarges rapidly and catastrophic propagation soon follows. When chain mobility is relatively low, the dissipation of energy through viscoelastic processes near the tip of a slowly growing crack retards its progressive growth. But this source of strength is rather ineffective except within narrow ranges of temperature and extension rate, or time scale more generally. Thus, high strength and toughness result from other mechanisms that impede crack growth. Effective mechanisms usually come into play and impart toughness if colloidal particulate fillers or plastic domains are present, except at low concentration.
Polyester in Reinforced EPDM—Factors Affecting Thermal Degradation
Authors: Shinada Y. , Hazelton D. R. , Esso Kagaku K. K. 
Published: February 2011

Abstract
Polyester cord strength loss in EPDM depends on three factors: the presence of moisture, the nature of the cure system, and the aging environment. Of these factors, moisture is most critical. Cord degradation is caused by hydrolysis and is catalyzed by amine or amine-like compounds formed from the curvatives. High temperature also accelerates the deterioration. Knowledge of the service environment is required to decide whether PET may be used to reinforce EPDM. Moisture has a very harmful effect on PET degradation, and a dry environment increases service life substantially. The most feasible method of controlling PET cord strength loss is via curative choice to minimize or avoid nitrogen-containing curatives. Use of desiccant to remove moisture gives no improvement under normal service conditions. “Amino Nitrogen Index” is shown to be useful in formulating EPDM cure systems which have least effect on PET. Systems with an ANI of less than 6 give satisfactory performance. Curatives and accelerators commonly used in EPDM can be ranked according to this concept to aid future compound development. The peroxide system is suggested for maximum heat and compression set resistance. Based on the laboratory performance level of commercial EPDM/cord systems, PET can be used in properly-compounded EPDM at temperatures to 125°C in combined glycol/air and to 150°C in hot air. The cord strength loss of rayon, nylon, and aramid is independent of cure system amino nitrogen content. When the proper cure system is used, the durability of PET is comparable to aramid in hot air. PET is equivalent in performance to rayon and nylon up to 125°C in glycol/air, but far below aramid. Aramid, nylon, and rayon appear suitable for continuous exposure to 150°C glycol. However, in practical applications of these cords other factors such as intermittent environmental changes, dimensional stability, etc. must be considered.
Distribution of Carbon Black in SBR
Authors: Oono Ryo 
Published: February 2011

Abstract
The interparticle distance between black aggregates in rubber was estimated by Fraunhofer diffraction with the mask of an electron micrograph of filled rubber. Up to 40 phr, the distribution of interpartiele distance has a sharp peak centered at 8000 A˚ with 20 phr and at 7000 A˚ with 40 phr. Above 60 phr, the interparticle distance distributes broadly in the vicinity of 4000 A˚. The size of black aggregates at 20 phr extends from 300 A˚ (one particle) to 3000 A˚, and the average diameter is 1200 A˚. Above 40 phr, black trends to aggregate more than at 20 phr, and the average diameter is about 1500–1600 A˚, the maximum diameter being 5000 A˚. In one black aggregate, there are about 40 spherical particles. The relation between the size and interparticle distance shows that isolated black aggregates are distributed in rubber under 40 phr and that at 40 phr they begin to connect partly with each other. Above 60 phr, a network of chains of black develops everywhere. The contact of black aggregates at 40 phr level corresponds to the abrupt change of physical properties of filled rubber.
Reinforcement of Elastomers by Carbon Black
Authors: Kraus Gerard 
Published: February 2011

Abstract
The reinforcement of elastomers by carbon black is governed by the morphology of the black and its physical and chemical interactions with the polymer. The latter are strongly affected by graphitization and surface oxidation. In modern rubber-grade carbon blacks strong bonding of the polymer to the carbon black surface is effected by several mechanisms, but surface chemical differences between blacks are relatively small, so that the dominant characteristic becomes the morphology. This is determined by the average size and size distribution of the particles which are fused together to form primary aggregates resembling branched random coils, the spatial arrangement of the particles in these aggregates, and the number of particles per aggregate and its distribution. This highly complex morphology can, to a first approximation, be represented by the specific surface area accessible to rubber and some, usually indirect, measure of the volume pervaded by the primary aggregates (“structure”). Important mechanical properties of reinforced rubbers depend to different degrees on these two characteristics, often in rather complex manner. Their effects on viscoelastic and failure properties are described. Additionally, some very recent observations on the effects of carbon black on network structure and the influence of the breadth of the aggregate size distribution on viscoelastic behavior are discussed.
Nonlinear Viscoelastic Behavior of Butadiene—Acrylonitrile Copolymers Filled with Carbon Black
Authors: Nakajima N. , Bowerman H. H. , Collins E. A. 
Published: February 2011

Abstract
Various viscoelastic measurements including dynamic mechanical measurements in tension at 110 Hz from −60–160°C, tensile stress relaxation measurements with 100% elongation at 25, 54, and 98°C, capillary flow measurements at 70, 100, and 125°C, and high-speed tensile stress-strain measurements carried to break at 25, 56, and 98°C were performed on four samples of carbon-black-filled butadiene—acrylonitrile copolymers. All the data were treated with the same equation for time-temperature conversion. The capillary viscosity—shear rate curves were significantly lower than the complex viscosity—angular frequency curves, indicating “strain softening” with extrusion. The viscosity was estimated from the stress-strain relationship at the yield point. The viscosity as a function of the strain rate is significantly higher than the complex viscosity as a function of angular frequency, indicating “strain hardening” with extension. The strain softening and strain hardening are attributable to the structural changes upon deformation of the carbon-black-filled elastomers. With the unfilled elastomers, neither strain softening nor strain hardening were observed in similar measurements.
Adhesion of Elastomers, with Special Reference to Triblock Copolymers
Authors: Gent A. N. , Hamed G. R. 
Published: February 2011

Abstract
Several physical and chemical factors affect the strength of adhesion (as measured by a peeling method) for elastomers adhering to rigid substrates. These factors include: the thickness of the elastomer layer (and of an adhering backing, if present); the rate of detachment and the test temperature; and the presence of chemical bonds between elastomer and the substrate. Adhesion of thermoplastic elastomers, i.e., SBS triblock copolymers, applied as hot melts, is much stronger than for the corresponding random copolymers, crosslinked in situ. These materials also show higher cohesive (tear) strength. Both effects probably arise from the same cause: an energy-dissipation process which operates at large stresses and prevents brittle fracture. This process is thought to be plastic yielding of the polystyrene domains.
The Kinetics of Polymerization Reactions
Authors: Gee G. , Melville H. W. 
Published: February 2011

Abstract
A general treatment of the kinetics of polymerization reactions is given to cover the two extreme conditions in which the lifetime of chain growth is (1) small, and (2) large compared with the half life of the monomer. Case (1) is considered on the basis of the assumption that the velocity coefficients do not depend on molecular size. Case (2) is considered for propagation coefficients which are on the one hand independent, and on the other hand dependent on molecular size. In addition, the distribution of molecular sizes is computed in those cases where the mathematical difficulties are not insurmountable. The application of these results to the analysis of polymerization reactions is discussed. The work described in this paper was completed when war broke out, and was to have been published as part of a book on polymerization processes. In view of the interest and development in these matters, it was felt desirable to give this account of these ideas now.
A New Method for Determining the Resistance of Soft-Rubber Products to Low Temperatures
Authors: Aengeneyndt J. , Kesternich W. 
Published: February 2011

Abstract
A simple method for testing the behavior of vulcanized rubber at low temperatures is described. In this method test-specimens in the form of strips prepared from finished goods, such as packing, hose, etc., are tested by a simple technique, without the necessity of mathematical calculations or the plotting of graphs. It is recommended that the hardening point be used as a criterion of behavior of vulcanized rubber in service at low temperatures, i.e., its resistance to cold. When this method is used, this hardening temperature should be 5° to 15° C below the lowest outside temperature at which the particular product must still operate satisfactorily.
The Evaluation of Tear Resistance in Elastomers
Authors: Graves Floyd L. 
Published: February 2011

Abstract
The fundamental fault in the stress distribution of the crescent tear-specimen has been discussed. A new angle tear specimen has been developed, with improved stress distribution. The specimen provides greater concentration of the pulling force at the point of tearing. The need of razor nicking of the test-pieces has been eliminated, with resulting marked improvement in the uniformity of tear resistance data. Tests carried out on four elastomers indicated that the crescent specimen values are dominated by the modulus and ultimate elongation of the material. Data obtained with the angle tear specimen indicated that tear resistance is a complex function of tensile strength and ultimate elongation. Inasmuch as the two specimens indicate different trends in tear resistance, it is hoped that this work will stimulate further discussion among rubber technologists on the evaluation of resistance to tearing.
Mechanism of Bias Filament Rupture in Fatigue of Nylon
Authors: Patterson Ralph G. 
Published: February 2011

Abstract
Cords in nylon tires fail at points of stress concentration owing to rupture of individual filaments by a characteristic fracture which occurs at an angle to the filament axis. Filaments fail by a crack growth process initiated at the fiber surface at defect sites. Crack formation and growth in single filaments were observed to occur at both natural and artificially induced surface defects. Failure begins at the compression side of the bend in filaments subjected to repeated cyclic bending. Similar findings were indicated for ductile metals. Fatigue failures in nylon filaments were related to the cyclic bending associated with compressive loading on inner ply cords of tires.