bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rubber, Polyisoprenes and Allied Compounds. II. The Molecule-Linking Capacity of Free Radicals and Its Bearing on the Mechanism of Vulcanization and Photo-Gelling Reactions
Authors: Farmer Ernest Harold , Michael Stephen E. 
Published: February 2011

Abstract
Ostromislensky discovered that benzoyl peroxide when heated with rubber to 140° brought about a species of vulcanization of the rubber, the chemical nature of which has been the subject of much conjecture and experimental investigation. It was thought at first that the process was essentially one of oxidation and, indeed, free benzoic acid derived from the peroxide was isolated by Ostromislensky from the reaction product; but van Rossem, Dekker, and Prawirodipoero found that, although much benzoic acid was liberated during the reaction, some became united with the rubber, and could afterwards be freed by saponification. Van Rossem and his collaborators, however, were unable to correlate the accumulated observations with the previously published generalizations of Gelissen and Hermans concerning the nature of the reactions between benzoyl peroxide on the one hand and numerous substances, including alcohols, organic acids, and saturated and benzenoid hydrocarbons, on the other; nevertheless, they agreed with Gelissen and Hermans on one point, viz., that to some extent cleavage of the peroxide with formation of benzoic acid probably occurred, and they suggested that the concomitant reaction was a dehydrogenation of the rubber, the latter possibly becoming cross-linked as a result (2C5H8+PhCO·O·O·COPh→—C5H7·C5·H7—+2PhCO2H). Subsequently, Ostromislensky, following useful observations by Bock, made a new examination of the reaction, and concluded that it proceeded according to the equation:
The Crystal Structure of Rubber Hydrochloride
Authors: Bunn C. W. , Garner E. V. 
Published: February 2011

Abstract
“Rubber hydrochloride”, the crystalline substances made by addition of hydrogen chloride to rubber, is of interest for two reasons. First, the periodicity along the fibre axis of drawn specimens indicates that the carbon chain has not the simple plane zigzag form found in paraffin hydrocarbons, but is somewhat shortened by folding. There is similar evidence that several other chain polymers also have folded chains; the elucidation of the geometry of such molecules would form a useful contribution to our knowledge of the stereochemistry of carbon compounds in general and chain polymers in particular. Rubber hydrochloride appeared to be a suitable substance for crystallographic investigation from this point of view: it gives a well-defined x-ray diffraction pattern. Moreover, a prediction of the chain form has been made on the basis of a knowledge of the periodicity and the use of a hypothesis which has been called the principle of staggered bonds. The determination of the structure by x-ray methods forms the first test of the validity and usefulness of this hypothesis. Secondly, rubber hydrochloride is interesting on account of its physical properties. Unlike rubber itself, it is crystalline at room temperature, “melting” at about 115° C. The present work on its crystal structure forms part of a program of research being carried out in this laboratory, and is a contribution to the attempt to understand the physical properties of chain polymers in terms of molecular structure.
Some Observations on the Flex-Cracking Characteristics of GR-S (BUNA-S) Compounds
Authors: Breckley Joseph 
Published: February 2011

Abstract
Probably the most serious defect of GR-S rubber is its poor resistance to flex-cracking, and much research has been conducted in an effort to improve this characteristic. Among the many tests employed in the study of rubber is the bend-flexing method, using the De Mattia apparatus, as described in A.S.T.M. Method D430-35T. However, when GR-S vulcanizates were flexed according to the standard procedure, erratic results were obtained. In an effort to secure more reproducible test data, a study was made of the crack growth that proceeded from small nicks made initially in the surface of the sample. Some difficulty was encountered in making a nick of uniform dimensions until a procedure was developed whereby a pinhole about 0.025 inch in diameter and approximately 0.05 inch deep was made in the center of the grooved surface of the test-piece. The hole was made by a pointed piece of steel, shielded so that it could penetrate the sample only to a constant depth. When the samples were prepared in this manner, the crack growth which extended from the hole during flexing was fairly uniform, and the results were reproducible within rather close limits.
The Influence of Chemical Structure on the Imbibition of Liquids by Rubber. I
Authors: Whitby G. S. , Evans A. B. A. , Pasternack D. S. 
Published: February 2011

Abstract
Studies of the swelling of rubber which had been carried out up to 1924 were reviewed by one of the authors in an earlier publication. A review of subsequent studies is to be found in a paper by Scott, who himself has contributed some data on the subject. These prior studies were not, however, concerned primarily to secure systematic information on the influence of the chemical structure of liquids on their imbibition by rubber, and they involved only a relatively small number of liquids, except for the study by Lee, in which the behavior of raw rubber in sixty-nine liquids was observed only qualitatively. Further, a good many of the earlier observers used material of unknown history and composition, such as “black rubber tubing”, and often assuming the swelling to reach a maximum in twenty-four hours. In the present study the course of the swelling of rubber, both raw and vulcanized, has been followed, quantitatively, at intervals over long periods, and a very large number of liquids have been examined. The present installment deals largely with classes of liquids (acids, alcohols, aldehydes, ketones, etc.) containing the more highly polar groups. A collection of hydrocarbons is, however, included, because hydrocarbons are in general good swelling agents, and data on them will serve for comparison with that on other classes of compounds.
Molecular Structure and Rubberlike Elasticity. II. The Stereochemistry of Chain Polymers
Authors: Bunn C. W. 
Published: February 2011

Abstract
In Part I of this work, the determination of the crystal structures of three long-chain polymers by interpretation of x-ray diffraction photographs was described. In all three crystals—β-gutta-percha, rubber and polychloroprene—themolecules have nonplanar zigzag chain forms and are asymmetric. It is now necessary to consider the bearing of the new knowledge of molecular geometry on the possibility of understanding rubber like properties in terms of molecular physics. It is widely believed that the flexibility, softness and other characteristic properties of rubberlike substances are in some way due to the flexibility of the molecules themselves. Long-chain molecules owe their potential flexibility to the swivelling of the chain units around the single bonds as axes, and it is therefore necessary to consider which bond positions are the most stable and what hindrances there are to rotation away from these positions. The present paper deals chiefly with the question of the most stable bond positions. The enquiry has interest, not only in relation to the problem of the origin of rubberlike properties, but also because it opens the way to a systematic consideration of chain types. There is already evidence that in many crystalline long-chain polymers, such as rubber hydrochloride, polyisobutylene, and some of the polyesters, the chains have not the fully extended plane zigzag form of polyethylene, but somewhat shortened (necessarily nonplanar) forms. It should be possible to discover what these forms are by interpretation of x-ray diffraction photographs, but the difficulties are in some cases formidable; some assistance in the form of guiding principles for the construction of possible chain types is desirable. It is the purpose of this paper to show that sufficient evidence already exists to suggest a general principle regulating bond positions in aliphatic molecules containing sequences of singly linked atoms. It will be called the principle of staggered bonds. In the three molecules whose structures were determined in Part I, every fourth chain bond is a double bond; the question of bond positions is less simple for such molecules than it is for those in which all the bonds are single. The latter will therefore be considered first.
The Course and Mechanism of Autoöxidation Reactions in Olefinic and Polyolefinic Substances, Including Rubber
Authors: Farmer E. H. , Bloomfield G. F. , Sundralingam A. , Sutton D. A. 
Published: February 2011

Abstract
The tendency of olefins to absorb molecular oxygen increases rapidly with increase in unsaturation. In monoolefins absorption is usually very slow unless it is actively promoted by irradiation, by the use of temperatures above room-temperature, or by chemical catalysts; in dienes and trienes it usually becomes considerable in diffused daylight; and in higher polyenes it tends to occur unpreventibly and excessively. The strong tendency towards oxidation shown by polyenes appears to be shared by unconjugated and conjugated substances alike, although the precise courses of reaction are probably somewhat different in the two cases. In the present paper attention is focussed mainly on monoolefinic and unconjugated polyolefinic substances.
Thermodynamic Study of the Elastic Extension of Rubber
Authors: Treloar L. R. G. 
Published: February 2011

Abstract
It is shown that the internal energy and entropy changes which take place when rubber is stretched may be determined either by a study of the variation of tension with temperature or by measurement of the heat evolved. The results obtained by a number of authors using both methods are considered. Although quantitative accuracy is not found, the evidence substantiates the kinetic-statistic explanation of rubber elasticity. Crystallization, though giving rise to important thermal effects, is not essentially connected with the phenomenon of elasticity.
The Caoutchol Component of Natural Rubber. A Correction
Authors: Roberts K. C. 
Published: February 2011

Abstract
The author recently described a method, developed in Malaya, for separating natural rubber into two main fractions, one containing, among other things, a hydrocarbon which was called caoutchene; the other including an oxygenated substance which constitutes about 2–5 per cent of natural rubber. The latter, which was named caoutchol, was described as a nontacky, freely soluble, highly elastic substance, for which the formula C80H130(OH)2 was suggested. Caoutchene, constituting 87–91 per cent of total rubber, and isolated only in a crude state, was described as tacky, of low tensile strength, and giving solutions of notably low viscosity, and its elongation under tension was stated not to exceed 200 per cent. It was further suggested that the elasticity of rubber was derived essentially from its minor component, caoutchol. The author has now been able to examine again the substance, in collaboration with his colleagues on the staff of the British Rubber Producers' Research Association. Fresh facts have been brought to light, both here and elsewhere, in consequence of which it has been found necessary to amend or withdraw the suggestions originally put forward. Nevertheless it is emphasized that caoutchol is a naturally occurring substance of real interest, quite distinct from artificially oxidized rubbers.
The Structure of Polychloroprene
Authors: Clews C. J. Birkett 
Published: February 2011

Abstract
Specimens of polychloroprene and light-treated polychloroprene have been examined by x-ray methods. There is evidently no change in the crystalline structure of the two substances, although there are differences in physical properties which are ascribed to cross-linking of the long polychloroprene chains. This conclusion is confirmed by the x-ray work. The unit cell of polychloroprene is probably orthorhombic, with dimensions a=8.90 A.U., b=4.70 A.U., c=12.21 A.U. From the experimentally determined density of 1.086 g. per cc, it is deduced that there are four chloroprene units in the cell. The x-ray density (for the stretched material) is 1.14 g. per cc. The long chains lie parallel to the b-axis (the direction of stretching), and four of these chains pass through the unit cell. It is concluded, from the identity period, that the chain is not planar and a possible spatial configuration is given.
The Magnetic Anisotropy of Stretched Rubber as a Function of the Tension to Which It Is Subjected
Authors: Cotton-Feytis Eugénie 
Published: February 2011

Abstract
From the standpoint of its magnetic anisotropy, stretched rubber is comparable in a first approximation to a uniaxial crystal, in which the direction of the axis is the same as the direction of elongation. It is possible to measure this anisotropy by means of the oscillation method used by Krishnan, Guha and Banerjee in studying crystals. The sample to be examined is suspended in a uniform horizontal magnetic field in such a manner that its axis is horizontal. It is then so arranged that the torsion of the suspension wire is zero when the rubber sample is in a position of equilibrium in the field. The times of oscillation T′ and T for very small angular displacements around this position, in the presence and then in the absence of the magnetic field, are then recorded. In this way the difference between the specific susceptibilities in the direction of the axis and in the horizontal direction perpendicular to the axis is calculated by application of the equation:
Gelation of Rubber Sols by Ultraviolet Light
Authors: Buckingham R. , Planer G. V. 
Published: February 2011

Abstract
On exposure of rubber sols to ultraviolet light in the absence of oxygen, gels known as rubber photogels are formed under certain conditions. It has been found that on removing the solvent the rubber recovered exhibits properties somewhat similar to those obtained on vulcanization. The study of photogelation is of interest, apart from the purely theoretical aspect, because of its possible bearing on the problem of vulcanization, including the various sulfurless vulcanization reactions. Another important aspect is the bearing on the study of the aging of rubber, as well as on the industrial manufacture of rubber cements and solutions. Solvents used in the preparation of photogels are divided into active ones, i.e., those which condense with the rubber on irradiation, and nonactive ones. A number of accelerators are effective in the reaction ; among the most efficient of these are carbonyl compounds Buch as benzophenone, acetone, benzaldehyde, as well as benzoquinone, chloranil, eosin, etc. The nature of the reaction has not hitherto been satisfactorily explained, and a number of widely varying theories have been advanced in the literature. Some investigators regard the reaction as being a polymerization. Pummerer and Kehlen support this view because of the similarity to the photopolymerizations of styrene and isoprene, both of which are favored by the same accelerators as those used in the formation of photogels. Stevens, on the other hand, mentioned cyclization of the rubber molecules as a possible mechanism, and Asano drew attention to the possibility of a stereochemical rearrangement taking place in the molecule on irradiation, producing insolubility. In the experimental work to be described, the reaction was studied by determining the reaction curves under various conditions. As it has frequently been pointed out in the literature that inconsistent quantitative results have been obtained in the study of this reaction, particular importance was attached to developing methods which enabled reproducible results to be obtained.
Organic Analysis of Hevea Latex. VII. Fat Acids, Resin Acids, Sterols, and Wax Alcohols. A Preliminary Note
Authors: Altman R. F. A. 
Published: February 2011

Abstract
In this note the isolation of the ether-soluble nonrubber components of latex will be described. As far as feasible, a quantative separation of the fat acids, resin acids, sterols, and wax-alcohols was attempted.
Hardness Tests at Low Temperatures
Authors: Lainé Paul , Roux André 
Published: February 2011

Abstract
The lack of precision in measuring hardness at low temperatures by the simple method of removing samples from a cold chamber and measuring their hardness as quickly as possible induced the present authors to construct a durometer which is particularly well adapted to studies at low temperatures. This apparatus is shown in its original form in Figure 1. The sample, E, is held fast on the bottom support, P, by a steel disc held tight from below by adjustable tension springs. This disc has a hole in its center, through which the penetrating point of the durometer can pass. The force required for the penetrator to enter the rubber is applied by a weight of 500 grams placed on the platform P1, and is transmitted to the penetrator by thin maillechort tubes, the heat conductivity of which is low.
Chemical Nature of the Rubber-To-Brass Bond
Authors: Buchan S. , Rae W. D. 
Published: February 2011

Abstract
In the initial stages of the reaction at the rubber-brass interface, formation of cuprous sulfide takes place. After this compound is formed, three possible reactions can occur. (1) The cuprous sulfide can unite with a “free” sulfur atom to form cupric sulfide. (2) The cuprous sulfide can attach itself to a sulfur atom already combined with the rubber. (3) The cuprous sulfide can attach itself directly to the rubber at points of unsaturation. In all cases of bad bonding brass examined by physical means, failure appeared to be due to nonuniformity in the structure of the plating. This lack of uniformity gave rise to a greater degree of corrosion and to conversion of the cuprous sulfide formed in the first place to cupric sulfide. Secondly, bad bonding stocks were characterized by two things : (1) The rate of reaction of the sulfur with rubber proceeded at a greater pace. (2) A greater degree of sulfide formation occurred at the brass rubber interface. This implied that reaction (2) was taking place, with the added complication of chains of sulfur atoms between rubber and copper. In other words it is necessary that a proper balance be maintained between the velocities of combination of sulfur with rubber and with brass. Thus, when the balance is disturbed, for example, by addition of more active accelerators, or, if the brass is in a more reactive state, then failure in adhesion results.
Properties of Sponge Rubber as a Material for Damping Vibration and Shock
Authors: Kosten C. W. , Zwikker C. 
Published: February 2011

Abstract
In order to obtain vibration-proof mountings, use is frequently made of sponge rubber. In this paper investigations are described concerning the factors on which its vibration damping properties depend. Formulas have been deduced for the mechanical impedance of sponge rubber, taking into account the presence of pores in the material. The formulas render the results of the measurements satisfactorily and, at the same time, they show how the qualities depend on factors such as porosity, kind of rubber, size of the pores, dimensions, etc. Under Section 6 we have examined more closely the choice of sponge rubber and the way of utilizing it in order to obtain the best results. 1. General.—Sponge rubber appears to possess excellent qualities as a damping material. This being so, the question arises as to what part is played by the air it contains, and how this air content must be fixed to obtain the best results. We have attempted to answer this question by paying attention to the mechanical impedance of sponge rubber.
Structure of Rubber
Authors: Clews C. J. B. 
Published: February 2011

Abstract
The results of the x-ray study of rubber structure may be summarized as follow : (1) The unit cell is monoclinic, space group C2h5, a=8.53±0.05, b=8.16±0.05, c=12.66±0.05 A˚, β=83°20′, with four isoprene chains in the cis modification passing through the cell, which contains 8 C5H8 residues. (2) In the unstretched state there is a random distribution of ordered crystalline regions and disordered regions. On stretching, the crystalline regions become orientated in one or more crystallographic directions, thereby giving rise to the x-ray fibre diagram. The crystalline regions may be identified with the micelles, which are groups of Hauptvalenzketten bound together by van der Waals' forces; a given Hauptvalenzkette is undoubtedly associated with more than one micelle. It is possible that the abnormal elastic properties are due to the chains becoming aligned parallel to the direction of stretching, and in addition there may be some extension of the chains themselves. Such an effect has been observed by Astbury in his work on keratin. Some recent work on the structure of butadiene and its derivatives in the solid state is described, which, although offering no immediate solution of our problem, may prove of value when further accurate data are available, both for these compounds and for the corresponding rubbers.
Effect of Light on Unvulcanized Rubber
Authors: Blake J. T. , Bruce P. L. 
Published: February 2011

Abstract
Although it has been known for centuries that light affects rubber, the action is still among the least understood changes which rubber undergoes. On exposure to light, but under no mechanical strain, vulcanized rubber develops a chalking on the surface and a network of very shallow cracks. If it is under mechanical tension deep cracks appear at right angles to the direction of the stress. This latter is a secondary effect however, since van Rossem has shown that direct exposure to light is not necessary for its production and that ozone is probably the cause. Raw rubber exposed to sunlight becomes sticky or tacky. This tackiness may increase until the rubber is practically liquefied or it may decrease and the rubber be trans-formed slowly into a resinous material. This paper is concerned primarily with the effect of light on raw rubber and with the catalysis (both positive and negative) of this effect.
The Oxidation Products of Rubber
Authors: van Rossem A. , Dekker P. 
Published: February 2011

Abstract
In their summary of the aging of vulcanized rubber, Porritt and Scott state that three factors are responsible for the changes in mechanical properties of vulcanized rubber during aging, viz.: (a) oxidation of the rubber; (b) after-vulcanization; (c) some colloidal change of the rubber, sometimes termed aggregation. Of these factors, oxidation is by far the most important because it is responsible for the decrease in mechanical properties, which leads to the general deterioration of rubber from a technical standpoint. It was Marzetti who proved that the decrease of mechanical properties in accelerated aging is due to oxidation. Later, Kohman confirmed this in a more concise way and showed that even such small amounts as 0.5% of oxygen absorbed by vulcanized rubber are sufficient to decrease tensile properties to 50% of their original value. When studying aging, three ways of tackling this problem are possible, viz.: (1) Investigations of the mechanical properties, either under normal conditions, or under special conditions such as elevated temperature or high speed. (2) Determination of oxidation products, which are formed during oxidation of the rubber. (3) Direct determination of the amount of oxygen which is absorbed by the rubber. It is clear that any of these methods may be combined with accelerated aging tests.