bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Vulcanization Characteristics of Crude Rubber
Authors: Thirion Pierre 
Published: February 2011

Abstract
Any vulcanization test of crude rubber which is based on a measurement of the strain modulus for only one time of vulcanization is insufficient as a source of information to the investigator of the rate of vulcanization and at the same time of the order of magnitude of the maximum modulus. It is proposed to complete this test by a second vulcanization for a different length of time and to correlate the complete vulcanization curves with the exponential functions of time. In this way it seems possible to derive two experimental values of the modulus: (1) A limiting modulus which characterizes the ultimate stiffness of the vulcanizate. (2) A vulcanization time constant which serves as an index of the rate of vulcanization of a rubber mixture. The more rapid the rate of vulcanization, the smaller is this constant. Application of this method to nine different lots of crude rubber proved that by this means it is possible to show well defined differences between various individual lots of crude rubber. Much more extensive studies will be necessary before it is known whether the method is applicable to the great majority of crude rubbers and whether it is adaptable in its present form to the formulation of a general specification for testing crude rubber. There is reason to believe that the use of the modulus value at 100 per cent elongation, already proposed by Gee, and his coworkers instead of 600 per cent elongation, would from this viewpoint offer numerous advantages.
Douglas Frank Twiss 1883–1951
Authors: Murphy E. A. 
Published: February 2011

Abstract
Among the celebrated names of those who have contributed so much in the last thirty years to rubber technology is that of Douglas Frank Twiss. Born in Birmingham, England, in 1883, he graduated at Birmingham University and received the Doctor of Science degree in 1910. Among other academic qualifications, he was a Bachelor of Science of London University and became a Fellow of the Royal Institute of Chemistry in 1908, on whose Council he served for nine years. He was also one of the pioneer members of the Institution of the Rubber Industry at its inception in 1921, and in 1934 he received the highest honor the Institution awards—the Colwyn Gold Medal—for his outstanding scientific work in rubber technology. During the long and active part he played in the British rubber industry, he served on various committees of the Research Association of British Rubber Manufacturers and the Institution of the Rubber Industry. Dr. Twiss's first appointment was as a lecturer in chemistry at the Birmingham College of Technology until 1914, when he joined the Dunlop Rubber Company to form a Chemical Research Department. Within a year he was appointed Chief Chemist, a position he held until his retirement in 1946. Some idea of his wide and varied interests can be obtained from over seventy scientific publications and two hundred patent specifications bearing his name and sometimes those of his fellow workers. He was also part author of a text book on practical organic chemistry and two volumes on inorganic chemistry dealing with oxygen and sulfur, and he served for many years as Special Editor in rubber and elastomers for British Abstracts.
Studies of the Mechanism of Mastication of Rubber. III. The Mutual Effects of Organic Bases and Softeners on the Viscosity Lowering of Rubber Solutions
Authors: Imoto Minoru 
Published: February 2011

Abstract
1. A large decrease in viscosity of a rubber solution was observed with the addition of furfurylamine in a quantity ten times as much as the softener used, such as furfuranthiol, thiophenol, β-naphthalenethiol, or benzoyl peroxide, but a small change with the addition of a large quantity of an amine, until finally reaching to a point where the decrease was less than that when only a softener was added. 2. For this reason, the following hypothesis is presented. Hyperconjugaation of the group (see PDF for diagram) in the hydrocarbon molecule of rubber increases with the addition of a small amount of an amine, promoting the rearrangement of the electron pairs of the double linkage, but with the addition of a large quantity of the amine, dissociation of the softener into its ionic form takes place and, as a result, the softener merely adds on to the double bond, the rubber molecule being unbroken.
Estimation of the Technological Properties of Rubber Mixtures by Their Fluidity
Authors: Galperina F. I. 
Published: February 2011

Abstract
In our laboratory practice, plastometers of different constructions and operating on different principles are used for determining the plasticity of rubber and of rubber mixtures. With all these instruments, the plasticity is measured at 70° ± 2° C, and this makes impossible any estimation of the properties of rubber mixtures during the initial period of vulcanization, when they are heated to temperatures much exceeding 70° (up to 130° C and higher). Furthermore, the plasticity factor (according to Karrer) is the product of the softness and elasticity, which also are measured at 70° C. For this reason, plasticity gives no indication of the behavior of mixtures at vulcanization temperatures, particularly since there is no simple relation between the softness and elasticity of synthetic rubbers. In the production of shoes by hot vulcanization, it is essential to know the behavior of the rubber mixture in the initial period of vulcanization, i.e., during the period of fluidity, at temperatures from 130° to 140° C and higher, when molding.
Identification of Accelerators and Antioxidants in Vulcanizates by Infrared Spectroscopy
Authors: Mann J. 
Published: February 2011

Abstract
Reliable methods for the chemical analysis of vulcanizates have been available for many years, and standard methods have been published in a British Standard which has recently been revised, but these methods do not cover the identification of accelerators and antioxidants and no comprehensive scheme for this type of analysis has been published. The identification of accelerators and antioxidants in vulcanizates presents a difficult problem because of the small concentrations employed, the close chemical similarity of many of them, and the wide variety of substances used. Many chemical tests have been developed for their identification, but difficulties arise when they are applied to vulcanizates. On the whole these chemical tests are unsatisfactory, and it seems unlikely that a comprehensive chemical scheme can be devised for the identification of accelerators and antioxidants in vulcanizates. There are, however, several physico-chemical methods which can be used for such analyses. The work of Proske has shown that accelerators in vulcanizates can be detected and estimated by the polarograph. The method is applicable to thiazoles, thiuram disulfides, and dithiocarbamates, but cannot be used with such accelerators as guanidines. Chromatography has recently been applied to the problem with considerable success. It has been shown that several accelerators give a characteristic chromatogram when the acetone extract of their vulcanizate is chromatographed on alumina, either alone or in the presence of cobalt oleate. In addition, antioxidants can be separated by chromatography from the rest of the acetone extract and can then be identified by color reactions. Although this method has been found in the R.A.B.R.M. laboratories to be very useful, there are serious difficulties in the way of developing a comprehensive scheme of analysis on this basis. For example, distinction between the various dithiocarbamate accelerators is difficult, and the method sometimes gives ambiguous results when applied to complex mixtures. Ultraviolet spectroscopy has been applied to the detection of accelerators and their decomposition products in vulcanizates, to the estimation of accelerators in masterbatches, and to the quantitative estimation of antioxidants. These applications suggest that ultraviolet spectroscopy should be a useful method for the identification of accelerators and antioxidants in vulcanizates.
Effect of Speed of Stripping on the Measured Adhesion between Conveyor-Belting Plies
Authors: Borroff E. M. , Elliott R. , Wake W. C. 
Published: February 2011

Abstract
No work seems to have been published on the effect of stripping speeds on the load required to separate belting plies. This report is a preliminary study to indicate the order of any effects. Two series of tests were carried out, with stripping rates of 1 inch per minute up to 74 inches per minute. Statistical examination of the results shows that the measured ply adhesion depends on the rate of stripping, and can be regarded as a linear function of the logarithm of the rate. The experimental error in determining ply adhesion is, however, relatively large, and in the second series of experiments the standard deviation was just under 1 pound per inch of width. It follows from this that for a specification rate of stripping of 1 inch per minute no significant difference would, in fact, be found if the rate dropped as low as 0.2 inch per minute or rose to 5 inches per minute. The report should be of interest to those engaged in fixing limits for specification tests.
Modulus and Relaxation of Elastomers in Torsion at Low Temperatures
Authors: Mooney Melvin , Wolstenholme W. E. 
Published: February 2011

Abstract
Second-order transition temperatures, Ts, indicated by volume or specific heat data, have been reported for many high polymer elastomers. Studies of the modulus-temperature relationship in the vicinity of Ts have revealed that the modulus below Ts is always enormously higher than above Ts. In the transition region, roughly from Ts+10°C to Ts, the modulus values, as usually measured, show a progressive rise with decreasing temperature. However, these modulus values, usually measured less than 1 minute after loading, are strictly transient modulus values, since at 1 minute the deformation under constant load is far from being constant. The present investigation was undertaken to determine how the equilibrium modulus, if any exists, varies with temperature in the transition region above the Ts, temperature. The method employed was, in principle, to impose a fixed deformation and to measure the stress after a lapse of time sufficient for the stress to become constant. Cylindrical samples, of 0.25-inch diameter, were twisted one turn per inch in a cold bath, and the torque at constant twist was measured as a function of time. The measurements were continued in many cases for months, but in no case did the torque show any indication of approaching a limiting value other than zero. These tests therefore failed in their initial purpose, which was to establish and measure the equilibrium modulus. However, the torque-relaxation tests did yield some interesting data, which indicated that all the elastomers tested develop crystallinity or a similar-ordered state when subjected to prolonged strain at reduced temperature. Moreover, the equipment used was well suited to low temperature thermo-stress measurements—that is, measurements of stress in a cycle of temperature variation at constant deformation. Two thermo-stress curves on Hevea gum stocks extending to low temperatures have previously been reported, one by Greene and Loughborough and another by Gehman, Woodford, and Wilkinson. In the present work thermo-stress measurements were made on a few elastomers at temperatures extending down as close to Ts, as was experimentally feasible.
Quantitative Characterization of Cure. IV. Definition and Measurement of Rate of Cure for Pure-Gum Natural-Rubber Compounds
Authors: Gee Geoffrey , Morrell S. H. 
Published: February 2011

Abstract
The purpose of this paper is to develop a simple practical method of assessing rate of cure, based on sound theoretical principles, and using only measurements which are normally available or easily made. Mathematical and experimental studies of modulus-time curves are presented, and it is shown that several types of gum compound give curves of a simple mathematical form, equivalent to that of a first-order chemical reaction. It is concluded that in such cases rate of cure can be defined and measured by the value of a first-order velocity constant, having dimensions time−1, the reciprocal of which determines the vulcanization period needed to produce a given percentage cure. Application to a substantial number of rubbers has shown that the method is capable of yielding reproducible results for the rate of cure of a single compound, and of distinguishing with high significance between different compounds. A connection is predicted between rate of cure, as thus measured, and scorch; preliminary data are consistent with expectation.
Transmission of Mechanical Vibrations through Rubbers
Authors: Morris Ross E. , James Robert R. , Snyder Harold L. 
Published: February 2011

Abstract
The purpose of this investigation was to determine how simple compression mountings for machinery compare with regard to transmission of mechanical vibrations when the mountings are made from different rubbers. The only difference between the mountings was the rubber contained; all mountings had the same physical dimensions, the same static modulus, and essentially the same hardness. Natural rubber was found to transmit less vibrational force than any of the other rubbers in the range of frequencies from 25 to 2000 cycles per second; moreover, its transmissibility was practically constant over this range of frequencies. Neoprene Type FR transmitted a little more force than natural rubber. Its transmissibility also remained practically constant over the frequency range except for a rise at low frequencies. The transmissibilities of all other synthetic rubbers tested were higher and increased with rising frequency over the entire range. The information obtained is of considerable value in the design of rubber mountings for isolation of machinery vibrations in the range of audible frequencies.
Elastoviscous Properties of Amorphous Polymers in the Transition Region. I.
Authors: Bischoff J. , Catsiff E. , Tobolsky A. V. 
Published: February 2011

Abstract
Experimental data on the stress-relaxation modulus Er,T(t) of a GR-S gum vulcanizate at a series of temperatures in the transition region are presented, and a “master curve” of log Q(t/K) vs. log (t/K) is thereby constructed. The characteristic relaxation time, K, for each temperature is defined and tabulated. A distinctive temperature, Td, is observed at which the activation energy for K is a maximum. Analytical expressions are given which describe the GR-S master-curve with great accuracy. The same analytical procedure can be successfully applied to data previously obtained for polymethyl methacrylate. A reduced equation is proposed which describes the time and temperature dependence of Q(t/K) in the transition region for both polymers.
The Diamagnetic Anisotropy of Natural and Synthetic Rubbers
Authors: Toor Elizabeth Weir , Selwood P. W. 
Published: February 2011

Abstract
The change in anisotropy with elongation has been found for natural rubber and for several synthetic rubbers. Unsaturated rubbers have a large principal susceptibility perpendicular to the direction of stretching, because of the presence of olefinic double bonds. The differences between natural rubber and polybutadiene are attributed to the presence of unsaturated side-groups caused by 1,2-addition in polybutadiene. Probably the magnetic anisotropy of these rubbers depends, not on the actual degree of crystallinity of the rubbers, but on the ability of the long-chain molecules to align themselves parallel to the direction of stretching. Therefore the changes in anisotropy with stretching are large when there is no cross-linking, and small when cross-linking occurs to any large extent. Saturated rubbers have an anisotropy opposite in sign to that of unsaturated rubbers. This must be caused by the broadening of electronic orbits perpendicular to the direction of stretching. Apparently methyl side-groups cause such a broadening of electronic orbits in polyisobutylenes, an effect much greater than the similar effect in polyethylene.
Statistical Kinetics of Hevea Rubber Cyclization
Authors: Gordon M. 
Published: February 2011

Abstract
Rubber cyclization provides a useful illustration of statistical effects intervening in the reactions of long-chain polymers. Analogously to the known cyclizations of simple diisoprenic terpenes, each individual cyclization act links two adjacent isoprene units in the rubber chain into a six-membered ring. However, some of the units remain stranded between neighboring rings and escape cyclization for want of a partner. Thus the final polymer has a copolymer structure of 86.5 per cent of diisoprenic rings and 13.5 per cent of uncyclized monisoprenic units. This result is derived from a statistical theory of Flory, and has previously found accurate experimental verification. The bearing of this statistical effect on the reaction kinetics has now been studied for the first time. Dilatometric experiments on rubber emulsions in sulfuric acid have shown that the cyclization reaction conforms in the main with a statistical cyclization law much better than with a first-order equation uncorrected for the survival of stranded units. High accuracy was required for this experimental distinction, whose importance lies in the implicit proof that the polymer units participate in the rate-determining transition complex, in accordance with the accepted proton transfer mechanism. A kinetic proof has incidentally been furnished for the fact that the rubber polymer contains long chains of identical units. When handled by an emulsion technique, this polymer can provide a useful “model compound” for its simpler terpene analogs. Certain rate abnormalities have been observed, including an induction period of reduced rate, probably connected with diffusion effects. A small volume change subsequent to the cyclization reaction may reflect a prototropic double-bond shift. The activation energy and entropy are found to be lower than in previous work, an effect traced in part to a curvature of the Arrhenius plot. The known dependence of cyclization rate on Hammett's acidity function H0 is quantitatively confirmed.
Action of Light on Sodium-Butadiene Rubber
Authors: Postovskaya A. F. , Kuzminskiĭ A. S. 
Published: February 2011

Abstract
An apparatus was devised and experimental methods of investigating the action of light on polymers in a high vacuum (10™6 mm. of mercury) were developed. The limits of accuracy of the methods for measuring gas formation and decrease of unsaturation are 1–2 per cent. The effect of ultraviolet radiation on sodium-butadiene rubber in a high vacuum is the formation of gaseous byproducts. The latter appear as two fractions: one which condenses at 180° C, and one which does not condense under the same conditions. The noncondensing part comprised 84 per cent of the total, and consisted of 64 per cent hydrogen and 32 per cent methane; this indicates rupture of the —C—C— and —C—H bonds. The action of light on rubber is accompanied by a loss of unsaturation. The change of unsaturation is primarily in the main chains and only to a small degree in the side chains (we know that the reverse is true with respect to the effect of heat). Measurements were made of the light energy absorbed by rubber, and the quantum yield of gaseous products was calculated. The small quantum yield (2×10−3) indicates the incatenate nature of the process. The decrease of solubility of an irradiated polymer is a consequence of a reaction between free radicals forming after rupture of the —C—H bond, and also after rupture of the carbon chain.
Ozone Resistance of Neoprene Vulcanizates. Effect of Compounding Ingredients
Authors: Thompson D. C. , Baker R. H. , Brownlow R. W. 
Published: February 2011

Abstract
The resistance of Neoprene vulcanizates to attack by ozone as measured by accelerated tests has been studied. The known superiority of Neoprene in this property was found to be affected more by compounding ingredients than previously recognized. It was found that neither the presence of accelerators nor their influence on the modulus of fully cured Neoprene vulcanizates affected ozone resistance. The addition of fillers impaired ozone resistance in proportion to the amount used. The coarse particle size fillers were particularly harmful. Petroleum base plasticizers had a negligible adverse effect, but certain of the ester and similar types were significantly deleterious. Unsaturated vegetable oils and their derivatives, as well as wood resin, are beneficial to ozone resistance. Certain softeners and extenders frequently used to promote ozone resistance so function only by virtue of the stress relaxation they induce in vulcanizates. A number of antioxidants, especially those which reduce flex cracking are powerful ozone-resisting agents, particularly when used in large quantities. Certain of the nondiscoloring type of antioxidants are harmful to ozone resistance.
Ozone in Los Angeles and Surrounding Areas
Authors: Bartel A. W. , Temple J. W. 
Published: February 2011

Abstract
It has become rather generally accepted among rubber technologists that ozone stands alone as the cause of exposure check-cracking of rubber. Newton, Crabtree and Kemp, and Fielding are apparently supporters of this view, and the present authors have concurred. The viewpoint, however, need not be considered as fixed. The experiment with nitrogen dioxide, cited by Haagen-Smit, raises interesting speculation of a possible exception, unless indeed the explanation lies in an intermediate formation of ozone in the system nitrogen dioxide-oxygen-sunlight. (This likelihood was suggested by Haagen-Smit in a private communication to one of the authors.) Interesting as some of these variant possibilities might be, however, the present authors record their belief in the simple rather than the complex explanation of rubber checking in Southern California, namely, that of ozone. The general similarity of pattern between the city and noncity stations argues against any dominant effect due to special components of the city atmosphere. The general prevalence of checking in the whole area, relative to that of the country at large, is generally consistent with the high level of ozone indicated by the measurements given here. Under present information, it seems unlikely to us that effects of alternately proposed chemical agents will bulk importantly in the total effect. The further development of information on these questions may be awaited with much interest.
Analysis of Vulcanized Rubbers. Influence of Accelerators on the Determination of Free Sulfur by the Copper Spiral Method
Authors: Mann J. 
Published: February 2011

Abstract
The copper spiral method is being inserted in a revised edition of the “British Standard Methods of Testing Vulcanized Rubber”, and this raises the question of what sulfur compounds react as “free” sulfur. In this method, “free” sulfur is considered to be that part of the sulfur which is present in the acetone extract and which reacts with a copper spiral, placed in the acetone during the extraction, with the production of copper sulfide, the amount of which can be estimated after its removal from the acetone. Since most accelerators contain sulfur, it is obvious that the presence of accelerators or accelerator fragments is a potential source of error. Fourteen accelerators of various types were therefore examined, and it was found that some react with copper, producing compounds which evolve hydrogen sulfide on treatment with hydrochloric acid.