bluuebunny/crossref_metadata_2025_split huggingface dataset:
Introduction to the Mechanism of the Hydrochlorination of Rubber
Authors: Gordon Manfred , Taylor James S. 
Published: February 2011

Abstract
The mechanism of rubber hydrochlorination is discussed in the light of the known crystal structure of rubber hydrochloride. The coiling of a rubber chain segment into a trans-decalin-shaped transition state is shown to be necessary and sufficient to explain the alternation along the polymer chain of d- and l-asymmetric carbon atoms, each separated from the next by three CH2 groups. As a preliminary to kinetic analysis, techniques are described for precise measurements of the degree of hydrochlorination of latex at various times of reaction. An analytical technique defines the reaction progress to 0.5 per cent, and serves to calibrate a diffusion-gradient method of following the reaction by density change. This method is at least equally sensitive, but more convenient. Despite the complexity of the natural-latex medium, the reaction kinetics are shown to be reproducible and free from uncontrolled effects. The reaction is rate-controlled chemically rather than by transport. The main part of the rate curve consists of two straight-line (zero-order) portions meeting at a kink.
Relationship of Oxygen to the Activity of GR-S Reclaiming Agents
Authors: Bennett R. B. , Smith G. E. P. 
Published: February 2011

Abstract
1. An alkylphenol sulfide reclaiming agent was found to have little activity in the absence of oxygen ; conversely oxygen produced little activity without the reclaiming agent. Together, the oxygen and reclaiming agent showed exceptional activity in attacking a sulfur-cured GR-S gum vulcanizate to produce soluble, low molecular-weight fragments under relatively mild experimental conditions. 2. The solubilizing effects of oxygen with reclaiming oils and the alkylphenol sulfide reclaiming agent were produced without significant increase of the amount of combined oxygen in the acetone or chloroform insoluble portions of the vulcanizate. Large increases of oxygen content were produced quickly by subsequent exposure of the treated and extracted samples to an atmosphere of oxygen. 3. No significant quantity of combined sulfur was removed under experimental conditions involving an excess of liquid reclaiming oils and agents. However, a significant, constant amount of sulfur was removed under conditions in which only small amounts of the reclaiming oils and agents were carried on the surface of the ground vulcanizates. This loss of sulfur was independent of both oxygen and of reclaiming aid and appeared to depend solely on the type of stock and on the physical conditions employed.
A Study of Stiffness Testing of Elastomers at Low Temperatures
Authors: Conant F. S. 
Published: February 2011

Abstract
In light of the above discussion, it does not appear logical to choose a “best” test for determining low-temperature moduli. A study of the data as a whole indicates that the correlation between the two sets of values from the simple beam-method (laboratories C-1 and C-2) are closest, but there is nothing to show that they are the most valid. It should be emphasized that, in the temperature region of greatest technical importance, that is, where the rubber is changing from its ordinary flexible state to a hard stiff material, the different tests show good agreement. A low-temperature limit of serviceability would be close to −80° F for the Hevea gum and −60° F for the GR-S by each of the methods studied. Another conclusion that might well be reached by a study of the test methods and data presented is that the term “modulus”, as applied to rubberlike materials, is rather vague unless the method of obtaining that modulus is also given.
A Study of Hardness Testing of Elastomers at Low Temperatures
Authors: Labbe B. G. 
Published: February 2011

Abstract
The spring-actuated instruments are desirable, since instantaneous readings may be obtained. Unfortunately, neither of the Shore instruments (A or D) provides adequate results over the complete range of temperatures for the stocks herein studied. A hardness instrument embodying the indentor point of the Shore-A Durometer with a loading spring requiring 0 to 5 pounds for the scale range would probably be more suitable for low-temperature work. The Pusey and Jones instrument is somewhat difficult to operate at the low temperatures (−60° and −80° F) because of the manner of loading and because of friction between the moving parts. The Olsen instrument provided similar difficulties as far as frosting of the parts was concerned. Some trouble was experienced with this instrument even at −40° F. No results were reported for the Armstrong indentation equipment below −40° F because of the unavailability of conditions below that temperature. On the basis of the information furnished, it appears that the Material Laboratory Indentometer is the most satisfactory of the dead-weight load hardness testers for use at low temperatures.
Crystallization and the Relaxation of Stress in Stretched Natural-Rubber Vulcanizates
Authors: Gent A. N. 
Published: February 2011

Abstract
Experiments are described in which the decrease of volume and simultaneous relaxation of stress in crystallizing extended samples of vulcanized natural rubber were followed with time at a temperature of −26° C. The theoretical treatment of Avrami is extended and shown to predict to a first approximation the time functions governing crystal growth in stretched vulcanizates. A continuous transition from polyhedral to aciform crystal growth on increasing the extension is indicated The relaxation of stress is found to be approximately proportional to the degree of crystallization throughout the process, the factor relating them being given by the theory of Flory at high extensions, that is, for aciform crystal growth. The retarding influence of vulcanization is attributed to a banned volume mechanism, whereby an element of volume around each cross-link is prohibited to nucleation, and an approximate value for the banned volume has been obtained. The influence of irregular chemical groups and prior heating on the rate of crystallization is also discussed.
Migration of Antioxidants during Oven Aging
Authors: Schonlau W. J. K. 
Published: February 2011

Abstract
The aging characteristics of a natural-rubber vulcanizate containing no antioxidant, measured in a Geer oven at 70° C, are affected by migration of phenyl-β-naphthylamine from other vulcanizates aged in the same oven at the same time.
Crystallization in Butadiene-Styrene Copolymers
Authors: Wood Lawrence A. 
Published: February 2011

Abstract
From Figure 3 one draws the following significant conclusions: (1) Crystallization is not observed if the polymerization temperature is above 60° C. (2) For polymerization at 50° C, a small amount (2 to 6 per cent) of bound styrene inhibits crystallization completely. (3) For polymerizations at 5° C, the limit is at about 15 to 18 per cent bound styrene content. (4) At the lowest polymerization temperatures normally utilized, this limit is at about 30 per cent bound styrene. Direct experimental observation is in general accord with these conclusions.
Effect of Structurizing Agents on the Plasticization and Vulcanization of Butadiene-Styrene Rubber
Authors: Novikov A. , Galil-Ogly F. A. 
Published: February 2011

Abstract
Compounds of the type of p-anisidine and N,N′-diphenyl-p-phenylenediamine cause structural changes in SKS-30A rubber and its solutions, particularly during heating. Vulcanization accelerators, in particular, mercaptobenzothiazole, greatly accelerate these structural changes in rubber in the presence of p-anisidine or N,N′-diphenyl-p-phenylenediamine during both heat oxidative plasticization and vulcanization. The degree and nature of the structural changes in rubber vary according to the type of accelerator. The structurizing action of p-anisidine and of N,N′-diphenyl-p-phenylenediamine during vulcanization is manifested in the increase of the tensile strength, equilibrium modulus, and rebound resilience of vulcanizates, and the retention of high relative elongations. The agents cited accelerate somewhat the process of combination of sulfur with the rubber in the initial stage of vulcanization, without increase of combined sulfur content at the point of optimum vulcanization. The hypothesis is advanced that the influence of p-anisidine and N,N′-diphenyl-p-phenylenediamine on the observed structural changes in SKS-30A rubber during its heat plasticization and vulcanization is related directly to the character of the oxidation processes, and may be caused by the reaction of the oxidized segments of the rubber (peroxide radicals, stable peroxides, functional oxygen groups, etc.) In unvulcanized rubber, this leads to a loss of plasticity and solubility, and, by vulcanization, to the formation of additional cross-links, to an increase of tensile strength, and with retention of high elongation at rupture. Vulcanization accelerators, such as mercaptobenzothiazole, which activate the oxidation processes in the rubber, increase considerably the rate and extent of these structural changes.
The Interaction of Sulfur and Sulfur Compounds with Olefinic Substances. VII. Low-Temperature Sulfuration of Trialkylethylenes with Hydrogen Sulfide-Sulfur Dioxide and with a Sulfur-Zinc Dithiocarbamate System
Authors: Farmer E. H. , Ford J. F. , Lyons J. A. 
Published: February 2011

Abstract
The sulfuration of trialkylethylenes with hydrogen sulfide-sulfur dioxide at 0° C (Peachey process) results in disubstitutive cross-linking of the olefins, yielding dialkenyl tetrasulfides. At higher temperatures, substitutive-additive cross-linking occurs, and alkyl alkenyl polysulfides are formed. Dialkenyl tetrasulfides are similarly formed by causing the olefin to react with sulfur at room temperature in the presence of zinc oxide and zinc dibutyldithiocarbamate, low concentrations of hydrogen sulfide acting as a catalyst for this reaction. At higher temperatures, the reaction is also exclusively disubstitutive, a feature connected with the function of zinc compounds in influencing the cross-linking reaction. The sulfuration of olefins with tetramethylthiuram disulfide at 140° C shows a similar influence of zinc compounds.
Studies of Rubberlike Polymers by Nuclear Magnetism
Authors: Honnold V. R. , McCaffrey F. , Mrowca B. A. 
Published: February 2011

Abstract
The actual width of the proton resonance line in uncured natural rubber has been determined at room temperature to be 0.06 gauss. Curing of polymers increases the line width at a given temperature. The small increase in natural rubber is possibly compatible with a physical bonding rather than the usually assumed cross-linking. For a butadiene-styrene copolymer, the increase of line width due to cure is somewhat larger. Carbon-black loading increases the line width to a lesser degree than does cure. This is compatible with the concept of physical bonding between the blacks and the polymer chain molecules. Variations of line width caused by changes in chemical composition and copolymerization were also investigated. Polypropylene and polypropylene oxide of roughly the same average molecular weight are compared. The polypropylene oxide exhibits a greater degree of “rotation” about its C—O bonds than polypropylene does about its C—C bonds. Two butadiene-acrylonitrile copolymers also have been studied as a function of temperature. Finally, spin-lattice relaxation time vs. temperature studies are reported for a butadiene-acrylonitrile copolymer and for raw Butyl, over the temperature range from −50° to 70° C. Estimates of the magnitude of the barriers hindering “rotation” are made.
Some Osmotic Measurements of the Molecular Weight of a High Molecular-Weight Fraction of Rubber Hydrocarbon
Authors: Drake G. W. 
Published: February 2011

Abstract
Fractionation of the rubber hydrocarbon in temperate climates has usually resulted in high molecular-weight fractions, with a molecular weight of the order of one million. Bloomfield has shown that fresh latex contains a considerable proportion of hydrocarbon having an intrinsic viscosity (η) of 10 or over and, therefore, a molecular weight of well over 106. The fractionation technique used by Bloomfield in Malaya has now been applied by the writer to smoked sheet and to F rubber, working in the United Kingdom. No very high molecular-weight fractions were found in the smoked sheet, but the F rubber yielded a fraction of (η)=7.3 and a number average molecular weight 6×106, determined osmometrically. The average molecular weight of natural rubber when freshly prepared is probably well over a million, and includes a substantial portion having a molecular weight of several millions. By the time smoked sheet has reached temperate climates, the high molecular-weight portion has probably been converted to gel. F rubber, presumably because of its different method of preparation, retains the major part of its high molecular-weight material during prolonged storage.
Measurement of Steady Flow Characteristics of Rubber at High Rates of Shear
Authors: Bulgin D. , Wratten R. 
Published: February 2011

Abstract
A coaxial cylinder viscometer suitable for use with long-chain polymers and technical rubberlike materials is described. Special features of the apparatus are the use of thin films to reduce heating, the ease of obtaining end corrections, and the use of high pressures to eliminate slip and facilitate filling the shearing gap. Results with uncompounded rubber show that the shear stress converges to a value of approximately 2.5 dynes per sq. cm. at shear rates in the region of 100, and that this value is independent of temperature (90° to 150° C) and of the chain length of the polymer. Certain polymers do not show this convergence.
The Mooney Viscometer
Authors: Baader Th 
Published: February 2011

Abstract
The preparation and forming of test-specimens for the Mooney viscometer by compression between the stator and rotor is accomplished in a rather crude way, and certainly more care should be taken than is evidently considered necessary. Investigations have shown that, by the use of pieces of rubber stock of as nearly the same size as possible as the cavity between the stator and rotor, several sources of error and certainly disturbing factors can be avoided, or at least minimized. As a good example of such errors are the considerable internal stresses which affect the measurements. In Figure 1, the effects caused by internal stresses, which, after completion of a test and removal of the specimen from the rotor, cause shrinkage and swelling, are easily recognizable by a comparison, to scale, with a vulcanized specimen whose cross-section is the same as that of the unvulcanized specimen as it fills the cavity between the rotor and stator. The internal stresses result in a hardening of the test-specimen, which may increase the true Mooney viscosity by as much as 5 per cent.
Chlorination of Natural Rubber Solutions by Means of Phenyl Iododichloride
Authors: Ramakrishnan C. S. , Raghunath D. , Pande J. B. 
Published: February 2011

Abstract
The loss of unsaturation attending the chlorination of carbon tetrachloride solutions of unmasticated pale crepe and deproteinized rubbers by means of phenyl iododichloride was followed by quantitative ozonization of the chlorinated products, ranging in chlorine contents from 2.3 to 73.6 per cent. It is concluded from such studies that the reaction proceeds mainly by the additive reaction of the chlorine radicals produced by the thermal decomposition of phenyl iododichloride. The hydrogen chloride found in the preparation of these chlorinated products was determined. It has a value below 1 per cent up to about 15 per cent chlorine content and thereafter it increases. However, this value generally does not exceed 4 per cent. This indicates the occurrence of only a slight amount of substitutive reaction by chlorine. Cyclization also takes place, probably following an additive reaction of the chlorine radicals. The main difference between the deproteinized rubber and pale crepe rubber reactions is confined to the very early stages, wherein the nonrubber components have a directive influence in bringing about a slightly earlier onset of cyclization. It is also concluded that atmospheric oxygen has a negligible effect on the reaction.
Nonrubber Components of Ammonia-Preserved Latex. An Analytical Study
Authors: Tunnicliffe M. E. 
Published: February 2011

Abstract
Analyses of ammonia-preserved latex concentrates have been made in order to study some of the main features of composition of the nonrubber material at the time of using the latex, usually about three months after tapping on the plantations. The information thus obtained is supplementary to corresponding work carried out on fresh latex in Malaya. Latex, at the stage now being considered, contains no phospholipin as such; but its decomposition products, ammonium soaps, free choline, and combined phosphate (probably glycerophosphate) are found. There is protein in the serum and at the rubber interface, a small amount of free amino acid, and probably also substances of a polypeptide nature. The serum contains salts of volatile and nonvolatile acids, in some cases as ammonium salts, and also a considerable amount of quebrachitol. The rubber phase contains phytosteryl esters. From the analyses of an electrodecanted and a centrifuged concentrate prepared from a common field latex it is shown that the higher amounts of some, but not all, nonrubber components in the electrodecanted concentrate are in accordance with its having a smaller average rubber particle size. The excess of both protein and phospholipin breakdown products indicates the existence of a protein-phospholipin complex. Analysis of the serum remaining after electrodecantation and of the original field latex has enabled a tentative distribution of nonrubber material to be calculated between serum and rubber phases.
The Thermal Effect in the Elongation and Relaxation of Rubber
Authors: Ehrbar J. P. , Boissonas Ch G. 
Published: February 2011

Abstract
Samples of natural rubber and synthetic rubber were stretched, and the temperature rises were followed by a thermocouple. The heat evolution was found to correspond to an adiabatic process. The study of the dependence of the heat effect (the Gough-Joule effect) on time shows that, while stretched, rubber crystallizes slowly and the phenomenon can be followed experimentally for several hours. The final stage of crystallization is probably a first-order reaction, the velocity constant of which is nearly independent of the percentage elongation and which has a small temperature coefficient. On the contrary, fusion following release of the applied stress is relatively rapid.
Thermodynamics of Crystallization in High Polymers. Natural Rubber
Authors: Roberts Donald E. , Mandelkern Leo 
Published: February 2011

Abstract
The existence of an equilibrium melting temperature, T0m, at 28 ± 1°, for unstretched natural rubber has been established, using dilatometric methods. The lower melting temperatures previously observed are a consequence of the low temperatures of crystallization and the rapid heating rates employed. From melting point studies of mixtures of the polymer with low molecular-weight diluents, the heat of fusion per repeating unit, ΔHu has been evaluated as 15.3 ± 0.5 cal./g. The values of ΔHu and T0m have then been combined with data of other workers to obtain the following information concerning natural rubber: (1) The variation of melting temperature with applied hydrostatic pressure has been calculated from the Clapeyron equation to be 0.0465° C/atm. (2) The degree of erystallinity resulting from maintaining a sample at 0° until the rate of crystallization is negligible has been calculated, by three independent methods, to be in the range 26 to 31 per cent. (3) Analysis of the stress-strain-temperature relationship has indicated that crystallization is the cause of the large internal energy changes that are observed at relatively high elongations.
X-Ray Investigation of the Amorphous State of Rubber
Authors: Kasatochkin V. I. , Lukin B. V. 
Published: February 2011

Abstract
The x-ray diffraction pattern of amorphous rubber, which is an amorphous ring, resembles the pattern of low-molecular liquids. In our previous work, it was established that the diffraction pattern observed is due to the coherent scattering of only those segments of the molecular chains in which the aggregation is analogous to that of low-molecular liquids, and is determined by the presence of a pseudo-order. A large part of the links of the molecular chains, owing to the prevailing disorder, scatters the x-rays incoherently, like scattering by a gas. For one component of amorphous rubber, the concept of “liquid phase” was introduced, and, for the other, that of “gaseous phase”, thereby subdividing them according to the type of scattering of x-rays. Amorphous rubber, according to our data, contains a large number of chair segments which are characterized by a high degree of disorder. The presence of such a disordered molecular phase is a general and characteristic property of high-molecular substances, and is caused by natural obstacles in the dense packing of the large molecules. This characteristic of molecular aggregation is undoubtedly reflected in the physical-mechanical properties of polymers.
Molecular Weights of Emulsion Polydienes
Authors: Morton Maurice 
Published: February 2011

Abstract
In the polymerization of dienes there is always the possibility of a cross-linking reaction between the polydiene chains because of the residual double bonds in the chains. Such a reaction can eventually lead to the formation of “infinite networks” which are characterized by loss of solubility (gel). The statistics, mechanism, and kinetics of the formation of such networks during polymerization have been treated in recent years. From this treatment it becomes apparent that the onset of gel occurs when there is one cross-linked monomeric unit per weight-average primary chain. The latter term refers to the polymeric chain uncontaminated by any cross-links. Recent data have shown that the rate of the cross-linking reaction is relatively slow compared to the propagation reaction during a polymerization, and that polydiene chains can reach lengths of at least several thousand units without including a cross-linked unit. This permits the attainment of synthetic rubber of reasonably high molecular weight without the inclusion of an insoluble gel fraction. The emulsion polymerization system, which is used so extensively in the synthetic rubber industry, is governed by special considerations, as regards both the cross-linking reaction and the factors controlling the chain length. Because the bulk of the polymerization occurs within the polymer particles, which are kept more or less saturated with monomer, their concentration remains relatively constant as long as any free monomer phase exists (50 to 60 per cent conversion). Hence, unlike the case of bulk polymerization, the rate of the cross-linking reaction (as well as that of the polymerization reaction) remains constant up to 50 to 60 per cent conversion. In other words, in emulsion systems, the cross-linking reaction proceeds at a uniform but faster rate than in bulk systems during the first half of the polymerization, owing to the higher concentration of polymer at the locus of reaction. Beyond that point, the cross-linking rate increases as the polymer concentration increases.