bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of Stress Relaxation with Finite Strain
Authors: Bernstein B. , Kearsley E. A. , Zapas L. J. 
Published: February 2011

Abstract
Two simple types of constitutive equations appropriate to materials exhibiting viscoelasticity are presented, one of a basic solid nature and one of a basic fluid nature. The predictions of the equations for a stress relaxation experiment are worked out and compared to the data from some experiments on various elastomers. The fluid theory is shown to be most appropriate in a certain sense.
Polyisobutene Degradation in Laminar Flow: Composition and Shear Variables
Authors: Portes Roger S. , Johnson Julian F. 
Published: February 2011

Abstract
Mechanical degradation of polyisobutene solutions in laminar flow under known shear stress conditions was performed in a thin-film, high-shear, rotational viscometer. Polyisobutenes with molecular weights from 40000 to over a million were studied at several temperatures and concentrations in n-hexadecane. Reduced variables, of a form similar to those used in studies of temporary viscosity losses, can be used successfully to correlate permanent viscosity losses due to degradation. The variables which superimpose are stress, temperature, and concentration. The range in which reduced variables apply corresponds to concentrations and molecular weights where degradation is commonly observed and to the region where polymer entanglements exist.
Effect of Extraction and Rubber Purity on Stress Relaxation of Cumyl Peroxide Vulcanizates
Authors: Dunn J. R. 
Published: February 2011

Abstract
Oxidative stress relaxation of peroxide vulcanizates of various grades of natural rubber has been investigated at 100° C. The rubbers were examined both with and without hot acetone extraction before or after cure. Highly purified rubber vulcanizates exhibited autocatalytic relaxation, but those based on crepe or smoked sheet did not, because they retained natural antioxidant even after extraction. Autocatalysis was no longer found in extracted purified rubber vulcanizates if these were prepared from a mix containing phenyl-β-naphthylamine. The antioxidant reduced network scission but had less effect upon the amount of crosslinking taking place during aging.
Study of Carbon Black Structures in Rubber
Authors: Payne A. R. 
Published: February 2011

Abstract
The effect of carbon-black structures in rubber were studied using dynamic testing techniques. The aspects studied were the effects of the degree of vulcanization and the degree of dispersion on dynamic modulus and loss. Relationships were established between electrical conductivity and dynamic modulus, and between the maximum dynamic viscosity and the carbon-black modulus changes on oscillation. Finally, use was made of carbon-black/paraffin-oil mixtures as model materials in order to explain the effect of carbon-black structures on the modulus enhancement of carbon-black-loaded vulcanizates.
Relevance of Elastic and Loss Moduli of Tire Components to Tire Energy Losses
Authors: Collins J. M. , Jackson W. L. , Oubridge P. S. 
Published: February 2011

Abstract
This study of energy losses in tires was undertaken to obtain a better understanding of the contributions of tire components, and to relate them more precisely to laboratory measured dynamic properties. Details are given of a general method of analysing total tire energy losses into components due to the tread, sidewall, textile and carcass rubber. The method entails measuring the losses, as determined by rolling resistance experiments, of tires in which the composition of the components has been varied systematically. The results have been correlated to the dynamic properties of the tire components, and the tire parameters, deflection and inflation pressure. The method has been applied to two extreme sizes of tires, 9.00–20 and 2.25–8. The work described in this paper will enable the tire designer and rubber and textile technologist, to predict with greater certainty the effects on tire energy losses of any changes in tire materials and will also give them more guidance in formulating these changes.
Influence of Regeneration of Reduced Triphosphopyridine Nucleotide (TPN) on Formation of cis-Polyisoprene in Hevea Brasiliensis
Authors: Ribaillier Daniel , Cuong Tuong Chi , Fournier Paul 
Published: February 2011

Abstract
Hevea brasiliensis latex can use glucose-6-phosphate to produce triphospho-pyridine nucleotide and adenosine triphosphate. Conversion of sodium acetate and mevalonic acid depends on the presence of these cofactors.
Behavior of cis-Polybutadiene during Mastication
Authors: Kraus Gerard , Rollmann K. W. 
Published: February 2011

Abstract
Cold mastication of natural rubber in presence of oxygen leads to scission by a shear mechanism with subsequent stabilization of the free radicals by oxygen, while at high temperatures oxidative scission becomes the dominant mechanism. Studies of the behavior of cis-polybutadiene reveal that similar reactions are effective, but occur at much reduced rates. Shear degradation is particularly difficult to achieve in typical cis-polybutadienes. This is related to the molecular weight distribution of these polymers which usually lack the very high molecular species most subject to shear-induced degradation, in agreement with the theory of F. Bueche. It is shown that when such a high molecular weight fraction is supplied, shear breakdown may be realized. All cis-polybutadienes undergo oxidative breakdown at high temperatures, the scission rate becoming appreciable above 140° C. A number of oxidation catalysts have been found which markedly increase the scission rate without leading to a correspondingly large increase in crosslinking. Significant improvements in processing may be realized in this manner.
Nuclear Magnetic Resonance Studies of Molecular Motion in Some Elastomers
Authors: Slichter W. P. , Davis D. D. 
Published: February 2011

Abstract
The nuclear magnetic resonance (NMR) relaxation has been studied in polyisobutylene and polybutadiene at temperatures from −175° to +200° C and at three resonance frequencies: 20, 30, and 50 Mc/sec. In polyisobutylene, the spin-lattice relaxation time (T1) passes through two minima with change in temperature. The low-temperature minimum is ascribed, as in other compounds, to methyl-group rotation, but in polyisobutylene this motion is found to encounter relatively large hindrance, presumably owing to interlocking among the groups. The high-temperature T1-minimum is ascribed to rotational and translational motion of the segments. The extent of motion is qualitatively gauged by calculation from the Bloembergen-Purcell-Pound theory for NMR relaxation in simple liquids. T1 is insensitive to molecular weight (M.W.) over a wide range, but the dependence of T2 upon M.W. changes abruptly when M.W.≅4×104. In polybutadiene, T1 is found to depend markedly on the cis-trans content.
cis-Polychloroprene
Authors: Aufdermarsh C. A. , Pariser R. 
Published: February 2011

Abstract
cis-Polychloroprene was synthesized by chlorinolysis of 1,4-poly-2-(tri-n-butyltin)-l,3- butadiene. The latter was obtained by free radical polymerization of 2-(tri-n-butyltin)-l,3-butadiene. The structure of cis-polychloroprene was established by ozonolysis, and by infrared and NMR spectroscopy.
Vulcanization of Elastomers. 44. Vulcanization of Polybutadiene with Cumyl Peroxide. I.
Authors: Hummel Klaus , Kaiser Günter 
Published: February 2011

Abstract
Cumyl peroxide vucanization of cis-1,4 polybutadiene with 2“3 per cent 1,2 addition was compared with that of natural rubber. The essential findings are: 1) In both rubbers, cumyl peroxide decomposed at exactly the same rate. 2) As shown earlier for natural rubber, the crosslinking reaction was over in polybutadiene when cumyl peroxide decomposition was complete. 3) Final crosslink density in polybutadiene decreased with increasing vulcanization temperatures. 4) Crosslinking yield in polybutadiene can be estimated simply by comparison with the crosslinking yield in natural rubber.
Antioxidant Properties of Carbon Black in Unsaturated Elastomers. Studies with cis-Polybutadiene
Authors: Gruver J. T. , Rollmann K. W. 
Published: February 2011

Abstract
The thermal antioxidant behavior of carbon black was studied in vulcanized cis-polybutadiene and related to the surface chemistry of the black. Continuous and intermittent stress relaxation and oxygen absorption measurements were employed to determine the antioxidant ability of the carbon blacks. The blacks were characterized by the surface concentrations of oxygen-containing functional groups, using methods described in the literature. Antioxidant activity was found to be highest in carbons containing relatively large amounts of bound oxygen. These carbons are also acidic and decompose peroxides by the ionic mechanism. This was demonstrated with cumyl peroxide. However, even though the acidity and ability to decompose cumyl peroxide to phenol and acetone could be destroyed by methylation, this treatment did not seriously impair the antioxidant activity, so that the role of acidic groups appears to be minor. Evidence is presented which suggests strongly that the antioxidant behavior of carbon blacks is due to surface quinones, possibly hydrogen-bonded with adjacent hydroxyl groups. Measurements made on samples vulcanized in peroxide and sulfur curing systems indicate that the antioxidant behavior of carbon black is independent of the method of vulcanization in the absence of other antioxidants. A characteristic feature of the antioxidant action of carbon blacks is their tendency to repress the oxidative crosslinking reactions, the relative amount of compensation of chain scission by crosslinking being smaller than in gum vulcanizates.
Aging of SBR
Authors: Bevilacqua E. M. , Wenisch W. J. 
Published: February 2011

Abstract
Changes in properties of vulcanized SBR during aging at 130° C in air are the result of reactions involving both the hydrocarbon and the crosslinks. Hydrocarbon oxidation is related to the overall rate of oxidation; it leads to both scission and crosslinking. Sulfur crosslinks are broken and new crosslinks formed in reactions which are affected by oxygen but relatively independent of the overall rate of oxidation. The excess of crosslinking over scission decreases progressively with increasing cure.
Phenothiazine as an Antifatigue Agent for Natural Rubber, Synthetic Polyisoprene and SBR
Authors: Tarasova Z. N. , Eitingon I. I. , Senatorskaya L. G. , Fedorova T. V. , Dogadkin B. A. 
Published: February 2011

Abstract
Phenothiazine has no effect on vulcanization of rubber or standard mechanical properties of the vulcanizates. Phenothiazine considerably increases fatigue resistance of vulcanizates of the rubbers studied, under different fatigue conditions. Under the effect of thermal oxidation and repeated deformation phenothiazine or its conversion products combine with the vulcanizate. The phenothiazine does not combine when subjected only to heating. When used with certain inhibitors of oxidation phenothiazine has a synergistic effect.
Effect of Thio-Derivatives of Amines and Phenols on the Behavior toward Thermomechanical Treatment and on Fatigue of Vulcanizates
Authors: Tarasova Z. N. , Eitington I. I. , Senatorskaya L. G. , Fedorova T. V. , Snisarenko A. M. , Andronova G. I. , Dogadkin B. A. 
Published: February 2011

Abstract
1. It has been shown that thio-derivatives of amines (phenothiazine, benzo-α-phenothiazine, and 9-oxybenzo-α-phenothiazine in comparison with corresponding diphenylamine and phenyl-α-naphthylamine) cause a relatively lower rate of oxygen combination with rubbers and vulcanizates, a decrease in the rate of thermal breakdown of hydroperoxides, retardation of chemical stress relaxation and an increase in fatigue resistance. 2. Thio-derivatives of amines and phenols, by comparison with corresponding amines and phenols, contribute considerably to the preservation of the original vulcanization network in the course of “thermomechanical” action and thermal oxidation. 3. Thio-derivatives of amines and phenols, in combination with amines and phenols exhibit more than additive (reinforcing) action. Synergism in these systems is attributed to the effect of thio-derivatives on breakdown of hydroperoxides.
Measurement of Rubber Tack
Authors: Skewis J. D. 
Published: February 2011

Abstract
An instrument for measurement and study of tack of rubber compositions is described. The method involves pressing together two specimens of polymer compound with a chosen force for a predetermined time, and then measuring the time to separate them with a preselected force. Development of tacky adhesion is related to the product of force and a function of time that the specimens are pressed together. The measure of adhesion also involves the product of force and a function of time required for complete separation. Empirical treatment yields an equation to describe tacky behavior of a rubber composition in terms of the ratio of these products of force and time, the ratio being designated as the tack index of that composition. An example is given by comparing tack of SBR with that of natural rubber. SBR exhibits a tack index of about unity over a wide temperature range while natural rubber has a large tack index at 25° C, which decreases with increasing temperature. It is suggested that the excellent tack of natural rubber is due to crystallization with elongation.
Polymer Flow Behavior from Multispeed Viscometry
Authors: Wolstenholme W. E. 
Published: February 2011

Abstract
A practical viscometric technique has been developed for measuring flow of commercial elastomeric and thermoplastic materials at processing temperatures. A standard procedure for testing bulk polymer samples in a modified shearing disk Mooney viscometer with rotor speeds from .05 to 77 rpm is described in detail. Research, development or process control personnel can rapidly convert viscometer torque dial readings at the various rotor speeds to an isothermal flow curve in absolute units of shear stress and rate of shear by either of two methods shown by examples. Total time to test a polymer sample and plot the flow curve is less than one hour. Representative flow curves illustrate how polymers with essentially equivalent ML-4 @ 212° F can have large differences in flow at processing conditions. A set of isothermal flow curves covering a desired temperature range provides an excellent estimate of processing behavior over a range of temperatures. Numerical determination of the thermal dependence of flow is easily evaluated in terms of activation energy at constant shearing stress, constant rate of shear, or constant viscosity. Activation energy is a useful constant for characterization of non-Newtonian polymer flow.
Determination of Molecular Weight Distributions of Diene-Containing Rubbers by Precipitation Chromatography
Authors: Uraneck C. A. , Barker M. G. , Johnson W. D. 
Published: February 2011

Abstract
Ten variables were studied to optimize fractionation of synthetic elastomers by the Baker—Williams column technique. The two most critical factors were the rate of deposition of the polymer onto the beads within the column and stabilization of polydienes against crosslinking and degradation. After optimizing the fractionation technique certain fractionation and molecular weight distribution problems were studied. A problem frequently encountered in column fractionations is reversion, i.e., a drop in viscosity near the end of the fractionation. Reversion is attributable to branching, but polymer degradation and crosslinking can also contribute. The technique described can be used to detect long chain branching in elastomers. An important characteristic of emulsion polymers is the width of the molecular weight distribution. The fractionations showed that the heterogeneity index, Mv/Mn, of SBR increased with the magnitude of the regulating index of the polymerization modifier used. The most efficient modifier on a weight basis did not necessarily give the smallest heterogeneity index, as is predicted by theory. The heterogeneity index of a polymer prepared by incremental addition of mercaptan modifier was smaller than that of the control. The fractionation results were of value in understanding the behavior of modifiers in emulsion systems. In solution polymers an initiator with a large propagation/initiation rate ratio, or the use of branching or coupling agents, broadened the molecular weight distribution. The use of the Baker—Williams column on a routine basis has been valuable in the preparation of several new commercially accepted elastomers.
Development and Performance of the Portable Skid Resistance Tester
Authors: Giles C. G. , Sabey B. E. , Cardew K. H. F. 
Published: February 2011

Abstract
The portable skid-resistance tester can carry out a wide variety of measurements on the road and in the laboratory. This paper outlines the basic principles underlying the design of the tester and describes the laboratory and field trials conducted during the development of the instrument. The factors influencing its performance are emphasized. In its performance, the instrument behaves as a patterned tire skidding at 30 mph. It is particularly well suited for testing rough-textured surfaces, and readings are independent of gradient, camber, or crossfall on the test surface.
Synthesis of Trichain and Tetrachain Radial Polybutadienes
Authors: Zelinski R. P. , Wofford C. F. 
Published: February 2011

Abstract
Tri- and tetrachain radial polybutadienes have been synthesized by coupling very dilute solutions of linear polybutadienyllithium with stoichiometric amounts of methyltrichlorosilane or silicon tetrachloride. These polymers have three or four long chains (100–2000 carbon atoms) attached to a single atom.
Rheological Properties of Multichain Polybutadienes
Authors: Kraus Gerard , Gruver J. T. 
Published: February 2011

Abstract
The introduction of one or two long chain branches into a polybutadiene molecule to form trichain or tetrachain molecules, respectively, leads to profound changes in Theological behavior. At low molecular weights the Newtonian (zero shear) viscosity is decreased relative to a linear polymer of the same molecular weight. At molecular weights exceeding 60,000 (trichain) or 100,000 (tetrachain), the Newtonian viscosity rises rapidly above the corresponding value for a linear polybutadiene. However, non-Newtonian behavior of the branched polymers becomes more pronounced the higher the molecular weights, so that at moderate to high shear rates the viscosity of the branched polymers is uniformly lower than that of linear polymers of identical molecular weight.
Rheological Properties of cis-Polybutadiene
Authors: Kraus Gerard , Gruver J. T. 
Published: February 2011

Abstract
The steady-state viscosity of a number of cis-polybutadienes was determined as a function of shear rate and temperature by use of a capillary rheometer. Polymers investigated differed in molecular weight distribution and long chain branching. None of the polymers exhibited Newtonian behavior, even at the lowest shear rates attainable. Nevertheless, for polymers of similar molecular weight distribution and minimum branching, all the capillary viscometer data could be reduced to a single curve by a reduced variable treatment. The molecular weight shift function was found to be the same as for polymers exhibiting a Newtonian flow range, i.e., a 3.4th power law in weight-average molecular weight. Broadening the molecular weight distribution or increasing the degree of long-chain branching led to increasingly pronounced non-Newtonian behavior. Tensile creep experiments showed nonlinear viscoelastic behavior for all polymers studied, even at small strains. This behavior was most pronounced in the more highly branched polymers. At very low stresses some of these polymers exhibited extremely high viscosities, the strain being almost completely recoverable. Under larger stresses the viscosity of these rubbers dropped several decades and in the capillary extrusion experiments these polymers flowed readily. This is the same behavior observed previously in high molecular weight branched (multichain) narrow distribution polybutadienes. It is tentatively explained by a constraint of the branch points on the slippage of chain entanglements. The fact that all cis-polybutadienes exhibit this behavior, while linear polybutadienes made by organolithium initiation do not, suggests that all cis-polybutadienes may be branched to some extent.
Swelling of Vulcanized Rubbers in Binary Solvent Mixtures
Authors: Scanlan J. 
Published: February 2011

Abstract
The single-liquid approximation has been applied to the data of Bristow on ternary systems containing benzene and cyclohexane with one of the rubbers, natural, SBR, or butyl. Satisfactory fits are obtained with a constant value of the interaction constant between the two solvents χ12 which differs markedly, however, from the value obtained by measurements on the binary solvent mixture.
Mechanism of Tire Flatspotting and Its Relation to Fiber Properties
Authors: Papero P. V. , Wincklhofer R. C. , Oswald H. J. 
Published: February 2011

Abstract
Tire flatspotting has been shown to be related to cord compression in the footprint area. Because of compression, the cords are under less tension than those cords outside this area, and contract. Cord contraction and the depth of a flatspot which develops in a tire depend on: 1. Cord Physical Properties: Modulus dependence on temperature, Tg, crystallinity and orientation; response to applied stresses, and creep. 2. Tire Design Factors: size, number of plies, cord angle, cord construction (linear density and helix angle). In order to exhibit low flatspotting, a tire yarn must meet the following physical property requirements: high immediate elastic region—high modulus, high glass transition temperature—low creep, high yield point, high intermolecular chain friction (H-bonding, crystallinity) and low moisture regain.