bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of the Mechanism of the Deactivation Effect
Authors: Foll Jacques Le 
Published: February 2011

Abstract
The only method by which significant differences between the effects of antioxygenic agents and deactivating agents can be detected has been found to be a study of relaxation phenomena. An investigation by this method has also furnished further support to the theories of Tobolsky and his coworkers. The changes which take place during aging in the physical properties of vulcanized rubber are the result of two independent phenomena which occur simultaneously: (1) chain scission, and (2) formation of intermolecular bonds. As far as the aging of vulcanizates of natural rubber under normal conditions, e.g., socalled natural aging, is concerned, the chief phenomenon involved is scission of the chain molecules. In principle, therefore, there are two methods for combatting the deterioration of rubber on aging: (1) to impede chain scission by obstructing the fixation of oxygen, and (2) to promote the progressive formation of intermolecular bonds which compensate for the effects of the scission process. The first of these processes is that in which antioxygenic agents play the active part; in the second process, deactivating agents play the active part. From this viewpoint, deactivating agents play a part analogous to that of accelerators, and they may be regarded as representing a special type of acceleration. This theory makes possible a better understanding of a number of facts which, a priori, seem surprising: (1) the relationships of both chemical structure and mode of action of accelerators and deactivating agents, and (2) the protective effect of litharge, peroxides, and nitro compounds, all of which are vulcanizing agents. With respect to the intimate mechanism of the deactivating effect, one question remains unanswered, viz., how are intermolecular bonds formed under the influence of deactivating agents? This question recalls the question of the function of vulcanization accelerators, which has been the subject of many investigations, but which still remains a mystery.
Comparison of Rotation, Extrusion, and Compression Plastometers
Authors: Whorlow R. W. 
Published: February 2011

Abstract
Instruments expected to give results characteristic of the various classes of plastometer have been compared in a number of respects. The Dillon extrusion plastometer, shearing cone rotation plastometer, and Williams compression plastometer, were compared for their power of discriminating between samples of smoked sheet masticated for different periods, or between samples of MPC carbon black masterbatch remilled for various periods. In the first case, the Dillon instrument was found to be inferior to the other instruments, while for the black masterbatches the Williams instrument was inferior to the other two. The Williams instrument was the most, and the shearing cone the least, influenced by carbon black structure, a result in agreement with the use of the energy expended on the rubber as a measure of structure breakdown. Consideration of the correlation between shearing cone and Dillon plasticity values gives no evidence of marked slippage effects with the extrusion instrument, although it cannot be shown conclusively whether or not slippage occurs with the present form of instrument. It is concluded that a Mooney or shearing cone instrument is probably the best for general use, but that the Dillon instrument may have advantages for tests on carbon black loaded stocks.
Tensile Properties of Films from Low-Temperature GR-S Latex
Authors: Brown R. W. , Messer W. E. , Howland L. H. 
Published: February 2011

Abstract
Studies were made of the influence of a number of polymerization variables on the tensile strength of vulcanized evaporated films from low-temperature high-solids GR-S latexes. Previous reports of film tensiles on the order of 3000 pounds per square inch for latexes of 70/30 butadiene-styrene charge ratio were confirmed. The levels of accelerator necessary for optimum vulcanized properties were found to be considerably lower than those normally used, particularly for latexes shortstopped with dithiocarbamate salts. Microscopic coagulum found in some latex samples had a pronounced effect in decreasing film tensile of vulcanizates. Cured films from latexes emulsified with mixtures of fatty acid and rosin soap possessed considerably better tensile strengths than those from latexes using all fatty acid soap emulsification. Wide variations on Mooney viscosity had relatively little effect on ultimate film tensiles. Incorporation of small amounts of lignin into the latex as the ammonium or sodium salt decreased cure rates of films and aided in giving more reproducible tensile results. Both lignin and the sodium salt of cresyl monosulfide improved the aging characteristics of films.
The Polymeric Structure of Natural Rubber
Authors: Bateman L. , Watson W. F. 
Published: February 2011

Abstract
From the tree to the vulcanized article, the changes in the elastic properties of natural rubber are dependent on essentially second-order modifications of the parent polymer. Successfully in some ways, less so in others, rubber technologists have learned empirically how to develop advantageous qualities and to prevent or minimize the undesirable ones. This empiricism is inevitable because the chemical reactions which produce the physical changes are so little understood. For example, vulcanization represents the conversion of the chainlike polymer into a cross-linked network, but the nature, number, and distribution along the chain of the cross-links, and their variation with curing conditions and on subsequent aging are largely matters of speculation. In fact, one of the major impediments to scientific rationalization of rubber technology is the inability to interpret common physical observations, e.g., on plasticity, state of cure, deterioration on aging, cracking, in terms of molecular structure. The main chemical attack on the problem in these laboratories has been based on the rigorous, but necessarily long-term, course of first resolving the chemistry of a particular process with the aid of model systems, whereby product analysis and identification can be firmly established, and then determining how rubber behaves when caused to undergo similar reactions in a controlled manner. In other words, attention has been directed to the atomic details of aging, vulcanization, etc., rather than to their significance in modifying polymer structure. Our purpose here is to lay emphasis on the latter approach, first by surveying briefly the main physical changes encountered in rubber technology, and then, stimulated by some very recent work on the nature and degradation of raw rubber, by tracing certain fundamental factors underlying these phenomena.
Investigation of the Role of Intermolecular Forces in the Mechanism of High-Elastic Deformation. VII. The Effect of Molecular Interaction on the Fatigue Resistance of High Polymers Having Highly Developed Spatial Structures
Authors: Gul V. E. , Fedyukin D. L. , Dogadkin B. A. 
Published: February 2011

Abstract
It is shown experimentally that an irregular change of the fatigue resistance of loaded natural-rubber vulcanizates with increase of the degree of swelling in paraffin oil and in dibutyl phthalate is caused by the superposition of two processes: the increase of fatigue resistance, as a result of the reduction of mechanical losses, and the decrease of fatigue resistance due to the decrease of tensile strength proportional to the higher degree of swelling.
An Interesting Property of Certain Conductive Rubbers
Authors: Kersta L. G. 
Published: February 2011

Abstract
During the course of electrical measurements of conductive rubbers, an interesting characteristic of some such materials was discovered. As far as we know, this characteristic has not been previously reported. It was found that, under certain conditions, a polysulfide rubber (Thiokol LP2) shows a decrease of electrical resistance as the material is stretched. The resistance declines up to elongations of perhaps 20 per cent. Beyond this it becomes fairly flat for an interval, and then increases from there on to the elastic limit. An example of elongation vs. resistance is shown by the full line of the accompanying figure.
Electrophoretic Mobility Study of Fresh Hevea Latex
Authors: Bowler William W. 
Published: February 2011

Abstract
To both the producer of natural rubber latex and the manufacturer of latex goods, the stability of Hevea latex is one of its most important properties. Two aspects of this important property are the mechanical stability and the chemical stability. The former is measured by the sensitivity of latex to mechanical agitation, the latter by the sensitivity to addition of ionic material. Although there is no clear relation known to exist between these two stabilities, the electrical charge on the rubber particles is considered to be important in either case. Since electrophoretic mobility determinations furnish one of the most direct methods for studying the charge on colloidal particles such as those in rubber latex, the effect of seasonal and clonal variations, latex aging, ionic strength, pH, and the presence of added materials on the electrical mobility of fresh Hevea latex was studied. At the same time the mechanical stability of many latexes was measured in order to determine what correlation exists between mobility and mechanical stability.
The Microchemical Analysis of Rubber
Authors: Wyatt G. H. 
Published: February 2011

Abstract
While those who profess to be microchemists have a number of specialized techniques, it is surprising how often microchemistry is used without appreciation that this is being done. As examples in the analysis of rubber, two qualitative color tests may be mentioned that are both applicable to small samples. The first was described by Weber in 1900, but interest in it has been revised recently by Stern and by Parker and Wake. In this test the rubber is treated with bromine and then with phenol; natural rubber gives a violet color and so may be distinguished from synthetic elastomers. In the second test, due to Kirchhof, natural rubber is detected by the yellow-to-red color which it gives with trichloroacetic acid. Other reactions carried out with small quantities of rubber for identification purposes include the well known Beilstein test for halogens, in which the organic substance when heated on a copper wire imparts a green color to a Bunsen flame. This method was suggested by Newton for the detection of chloroprenes, and has been applied by Shaw in a systematic procedure for the identification of plastics in general. Spot tests have also been devised that depend on the reactions of the vapors produced by destructive distillation of the rubber being examined; for example, Neoprene gives vapors which bleach paper impregnated with potassium chromate, or the density and pH value of the distillate may be determined. The rates of reaction of natural rubber and various synthetic elastomers with mixed nitric and sulfuric acids has been shown to be characteristic and may be determined with small samples. In contrast with the above, some procedures have been called micromethods by their advocates merely because the samples used are smaller than usual. Microchemistry was clearly defined by Emich as covering the range 2 to 10 mg. of substance, and the present author's work described below should properly be termed semimicroanalysis.
Relation between Stress Relaxation and Aging Resistance of Rubber Vulcanizates. II. Effect of Copper in Various Accelerated Stocks
Authors: Pedersen H. Leth 
Published: February 2011

Abstract
As was shown in a previous paper, a definite relation exists between aging and relaxation rates for rubber vulcanizates. Gee has shown that the modulus of stocks with the same “compound” viscosity determines the average molecular weight between bonded units. We shall, therefore, expect to find a constant sulfur-bond distribution in related vulcanizates with the same niveau of moduli and Mooney plasticity and, hence, the same free energy for the process of oxidation. If various retarding agents such as antioxidants are added, measurement of the rate of relaxation of the stress at constant elongation will conform with the rate of aging expressed in terms of tensile strengths. For vulcanizates with the same system of accelerators but containing different fillers, the moduli will vary widely, and interpretation of the stress relaxation measurements (abbrev. SR) will become difficult. The same will hold for systems with boosted accelerator complexes. Plain accelerator/sulfur stocks seem, on the contrary, to give approximately the same range of stability whether tested in aging or relaxation. Thus the merit of the relaxation method is the rapid evaluation of the catalytic effect of compounds which does not interfere with the state of cure. By a proper choice of the temperature, the SR measurement can be completed in minutes, and it is possible to select the active compounds for the more tedious control in aging. Especially for work with the antioxidant effect in thiuram vulcanizates without addition of sulfur where the shelf aging in air at 95° C lasts for 50–60 days, the use of the stress relaxations measurement at temperatures of 130–150° C represents a very convenient method of information. The copper effect described in the following was actually stated with the SR method. Since the method easily might be conducted half or fully automatically, it is very suited for research work or even for control.
Abrasion of Automotive Tires
Authors: Kern Walter 
Published: February 2011

Abstract
This paper is intended to show that tire engineering is not concerned merely with improvement of quality, but also is concerned, on the part of engineers, with information on the friction phenomena in the boundary layer between the tire tread and the road surface. For a tire to have good abrasion properties, the resistance of the tread should be high and the work of friction should be as low as possible. Methods for measuring the work of friction are described, with some examples of influences which have control over it. While at the present stage of progress in technical developments, improvement of the resistance to abrasion of tire treads and in the design of treads is limited to small percentages, external conditions in service may increase the work of friction several fold. This accounts for common wide differences in the life of similar tires on the road. It is hoped that this paper may lead to further cooperative research on phenomena at the boundary surface between the surface of a tire and of the road. Such studies would be in the interest of the rubber industry, the automotive industry, and the consumer.
A Study of Electrostatic Charge Conditions in Automobile Tires
Authors: Giese O. , Stein H. , Lauer F. J. 
Published: February 2011

Abstract
If the test results for the various systems considered are interpreted with respect to the generation of flexure voltages, the following generalization can be made. A flexure voltage is produced in the case of opposite polarity between casing and tube. This is true unless stationary charges on the tread surface prevent generation of the potential. Another result of interpretation of Table 1 is the statement that the following voltage observations are to be regarded as determining the character of a tire system: (see PDF for table) It is believed that the foregoing has shown that there is reason to regard tires as a self-contained unit, as a system, with respect to their static behavior. The results plainly illustrate the interaction between inner tube and casing. A merit factor for the rating of tire systems has accordingly been derived, to take adequate account of practical considerations. This merit factor is taken as the sum of the voltages for the characteristic terms as enumerated above, namely : GZ=AP/E+AD/AS+AP/AD/E+AS/AD/E+AD/AS/E The resulting merit factors GZ have been assembled in Table 3. Summarizing, it may be said that, for a satisfactory solution of the problem of static charges on vehicles according to the experimental results reported, the following conditions should be met. The tire system should not generate any high tread-voltages and no flexure voltages should be generated. Both conditions are satisfied by the use of conductive inner tubes. Conductive inner tubes, in all cases tested, reduced flexure voltage to zero and the tread potential to such an extent that no undesirable effects could arise.
Chain-Length Distribution Functions of Polymers after Random Degradation and Cross-Linking, with Particular Reference to Elastomers
Authors: Watson W. F. 
Published: February 2011

Abstract
The distribution of chain lengths of polymers on formation, random degradation and random cross-linking, have been derived by a simple statistical treatment. Chain-length distribution functions for all cases are represented by special forms of the expression : Nx/N=(α+β+γ)exp[−(α+β+γ)x] where β is the reciprocal of the average chain length on polymer formation, α is the degree of random degradation, and γ is the degree of cross-linking.
The Structure of Neoprene. VI. Crystallization
Authors: Maynard J. T. , Mochel W. E. 
Published: February 2011

Abstract
This study of the crystalization behavior of chloroprene polymers has shown for the first time that the melting point of the crystalline phase of these polymers is an inverse linear function of the polymerization temperature. This relationship causes the previously unaccounted for decreased rate and degree of crystallization in polychloroprenes prepared at higher temperatures, and presumably is the reason for the similar behavior of polybutadienes. The melting point of crystalline polychloroprene is depressed by the introduction of monomeric diluents, as well as by the introduction of irregularities in the polymer chain by copolymerization with other monomers. It is very likely, therefore, that the lowering of the melting point in polychloroprenes by raising polymerization temperatures is the result of introducing an increasing proportion of structural irregularities by modes of polymerization other than trans-1,4. The branched units resulting from 1,2- and 3,4-polymerization may make a significant contribution, although ozonolysis has indicated that 40° C Neoprenes do not contain more than about 5 per cent of such branched structures. It is likely that 1,4-units in the cis-configuration are most important, and calculations based on the observed melting-point depressions in polychloroprenes suggest that, in 40° C polychloroprenes, cis-l,4-units could account for another 10–15 per cent irregularities. The question of the occurrence of head-to-head, tail-to-tail polymerization remains moot, although this is unlikely to be an important factor because of the polar nature of the chloroprene molecule. Regardless of these questions, it has been clearly demonstrated that Neoprenes have the most regular structure of any diene polymer so far characterized. Information about the degree of crystallization of polychloroprenes gained from dilatometric measurements has made it possible to calibrate the crystallization sensitive bands which appear in infrared absorption spectra, and these bands can now be used for rapid determination of the degree of crystallinity of Neoprene films. The heat of fusion of the crystalline phase of polychloroprenes has been determined. Copolymer data give the value 15.3 calories per gram, and diluent data indicate the value to be 22.7 ± 2 calories per gram. The latter value is probably the more reliable. It has been found that variations of molecular weight and degree of cross-linking have no apparent effect on the rate of crystallization of polychloroprenes made at a given temperature.
The Proton Magnetic Resonance in Natural Rubber
Authors: Gutowsky H. S. , Meyers L. H. 
Published: February 2011

Abstract
The proton magnetic resonance has been observed in natural rubber from liquid nitrogen temperature to room temperature. The absorption line widths show two regions of change. With rising temperature, the first change in width starts at about 155° K, and we assign it to the onset of CH3 group rotation. The second, larger change to a narrow line, starts at about 225° K and is assigned to the onset of segmental motions. The latter change coincides with the second-order transitions observed in various physical properties and provides a direct confirmation of the cause of the transition. Samples cured 30, 60, and 90 minutes were investigated, and it was found that curing has a larger effect on the line width changes at lower temperature than at higher temperature. The inferred greater effect of curing on CH3 group motions than on segmental motions suggests that cross-linking is not the primary mechanism of vulcanization. Rubber stretched 70 per cent was found to have the same resonance absorption as unstretched samples.
Phosphatides of Hevea Latex
Authors: Smith R. H. 
Published: February 2011

Abstract
Phosphatides, together with other lipin substances, were extracted from fresh latex in the form believed to be that in which they naturally occur. Analysis, after removal of water-soluble impurities, gave evidence that the total lipin contained approximately 51 per cent lecithin, 10.5 per cent inositol phosphatide, 3 per cent phosphatidyl ethanolamine, 20 per cent triglycerides and 15.5 per cent unsaponifiables. An enzyme was found to be present in latex, which is capable of liberating choline from the lecithin component after coagulation by adding to alcohol below 40° C, by adding to formic acid, or by freezing, but inactive in untreated latex. The enzyme was destroyed slowly on storing fresh latex and rapidly on adding ammonia or formaldehyde. The implications of these findings on the properties of commercially prepared rubber are discussed. Destruction of the phosphatide during storage of some untreated latexes was observed, but the effect was insufficiently consistent to account for the universal property of spontaneous coagulation.
The Plasticization of Rubber on Roll Mills
Authors: Stalinsky Eugene 
Published: February 2011

Abstract
Consider two mills with rolls of the same diameter, and assume that the rolls rotate n and n′, respectively, turns per minute, between 12 and 30. Let t and t′ be the times in minutes necessary to bring the same standard amount of rubber to the same degree of plasticity on each mill. It can be shown experimentally that the times t and t′, expressed in minutes, are related in the following way:
Possibilities in the Use of Sodium Chlorite in Latex
Authors: Tournier Josette 
Published: February 2011

Abstract
The oxidation of rubber by sodium chlorite can be accomplished either with rubber in the solid form or with rubber in aqueous suspension. The first process gives highly oxidized and very sticky rubbers. By the second process, the oxidation can be controlled so that all the sodium chlorite is decomposed in the latex, i.e., before coagulation and drying. The decomposition reaction is carried out either in neutral medium in the presence of an activator of decomposition of the sodium chlorite, e.g., formaldehyde, or in an acid medium with pH between 3 and 4. The oxidation process, which requires only small percentages of sodium chlorite, can be adapted to the manufacture of adhesive from latex and the preparation of rubbers plasticized directly without mastication. These degraded latexes react easily with various reactive agents of normal rubber, in particular with halogens.