bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Structure and Rubberlike Elasticity. II. The Stereochemistry of Chain Polymers
Authors: Bunn C. W.
Published: February 2011

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Measurement of the Absorption of Oxygen by Vulcanized Rubber in Air
Authors: Milligan A. G. , Shaw J. E.
Published: February 2011

It is generally agreed that oxidation is the controlling factor in the decay of rubber compounds. Measurements of the decay of any physical properties—commonly tensile strength—can be made in a convenient time only if the decay is greatly accelerated, and there is always a grave doubt about the equality of the acceleration for different materials. There is also a difficulty in selecting a universally suitable aging period, since the decay of the physical properties is not linear. A direct measure of the rate of oxidation is, in our view, more fundamental and less equivocal. It can, moreover, be made in a reasonable time at a temperature not far removed from service temperatures. Again, whereas tensile tests require several samples of each point in the timecurve to give acceptable mean values, here a single sample suffices for the whole test, and this sample can be simply prepared from a specimen of any form by rasping. The merits and simplicity of the method should commend it to rubber technologists.
The Direct Determination of Oxygen in Rubber. The Adaptation of the Ter Meulen Method to Rubber and Its Application to the Study of Aging
Authors: Cramer H. I. , Sjothun I. J. , Oneacre L. E.
Published: February 2011

The ter Meulen method for the direct determination of oxygen has been adapted, with modifications, to the analysis of raw and vulcanized rubbers. Raney nickel has been found to be quite effective as the reducing catalyst and to be satisfactorily resistant to sulfur poisoning. The method has been applied to the study of the aging of vulcanized rubber in the Geer oven and oxygen bomb. From this study the following conclusions may be drawn: (1) The increase in combined oxygen is greater in the oxygen bomb than in the Geer oven. (2) Deterioration of rubber in the oxygen bomb involves oxidation primarily, whereas that occurring in the Geer oven involves not only oxidation but also thermal decomposition followed by volatilization of oxidation products. (3) The effectiveness of an antioxidant in retarding the absorption of oxygen in oxygen-bomb aging agrees well with its ability to maintain the physical properties of the stock in which it is present. (4) The deterioration in physical properties of a rubber stock in the oxygen bomb during the early stages of aging is a linear function of the increase in combined oxygen. For stocks containing antioxidants and diphenylguanidine as the accelerator, an increase in combined oxygen of approximately 1.2% corresponds to a decrease in tensile strength of 50%. (5) The relationship of increase in combined oxygen to decrease in tensile strength seems to be affected not only by antioxidants, but also by accelerators of vulcanization.
A Proposed New Method of Retarding the Aging of Vulcanized Rubber by Means of Peroxides and Nitro Compounds
Authors: Minatoya S. , Ando^ T.
Published: February 2011

(1) Considering that low-sulfur vulcanization gives high resistance to aging, because vulcanization does not go beyond the primary stage, it has been sought to effect this control in stocks accelerated with diphenylguanidine. m-Dinitrobenzene has been selected from a number of possible agents as a reliable controller; other agents which retard vulcanization and have weak control effect or active oxidizing effect were rejected. (2) From a comparison of m-dinitrobenzene and aldol-α-naphthylamine in diphenylguanidine stocks, successful aging resistance has been observed. Mechanical tests were carried out before and after bomb aging, and chemical analyses were made of the vulcanized rubbers to throw light on the vulcanization mechanism and the reasons for improved resistance to aging. (3) Parallel experiments with other accelerators failed to reveal improved aging resistance, and in the presence of mercaptobenzothiazole in particular, m-dinitrobenzene acts as an oxidizing agent. (4) Tests of the stability of m-dinitrobenzene, alone and when mixed with various reagents, by the Abel test for stability of explosives have shown that the stability depends on the purity of the compound. Diphenylguanidine is effective as a stabilizer of m-dinitrobenzene, while other accelerators act as decomposers, thus providing a reason for the age resistance observed with diphenylguanidine. As a result of the stability tests, it has been found that various amines, soaps and mineral oils are effective as stabilizers of m-dinitrobenzene. As an instance of their application, aging tests have been carried out on rubber compounds accelerated with mercaptobenzothiazole and containing m-dinitrobenzene stabilized with diphenylamine. It has been found that the age resistance is much improved and is comparable with that obtained in the presence of aldol-α-naphthylamine.
Fatigue in Rubber. Part II
Authors: Naunton W. J. S. , Waring J. R. S.
Published: February 2011

1. An apparatus is described for measuring the modulus and resilience of rubber over a wide range of frequencies. 2. These measurements can be made at any point in the stress-strain curve of the sample. 3. By increasing the power input, the same apparatus can be used to induce high frequency fatigue in the sample. 4. The earlier work with the torsion head apparatus has been confirmed, namely, that internal friction is greatest near zero strain. 5. High frequency resilience is more independent of degree of vulcanization than tripsometer resilience. 6. Modulus tends to increase with frequency. The effect is least with a rubber gum stock and is greater with compounds containing gas black. 7. Resilience decreases with frequency both in gum and gas black compounds. The decrease is more rapid in the gum compounds. 8. Viscous resistance decreases with frequency and becomes constant at higher frequencies. 9. The modulus of both rubber and Neoprene carbon black compounds decreases with fatigue. 10. The change in modulus with frequency in fatigued stocks is exactly analogous to the change before fatigue in rubber, but there is a slight divergence in the case of Neoprene.
Note on the Theory of Water Absorption by Rubber
Authors: Daynes H. A.
Published: February 2011

There is still a need for a quantitative theory of the form of curves describing the changes of water content of rubber with time of exposure to various conditions of ambient humidity. Although considerable progress has been made in recent years, both in our understanding of the factors which determine such curves and in the use of empirical relations, there is still no fundamental solution which will enable reliable predictions to be made either for practical purposes or for verification of theories of the mechanism of absorption. It has been shown that, although this problem has much in common with that of the conduction of heat in solids, the chief obstacle to the application of the latter theory is the great deviation from linearity in the relation between humidity and the concentration of water in rubber which is in equilibrium with that humidity. It was also realized that it could not be assumed that the diffusion constant was independent of concentration (Daynes, Trans. Faraday Soc., 33, 531 (1937)). Blake and Morss (Proc. Rubber Technology Conference, London, 1938, 868), making use of this analogy between diffusion and heat conductivity, applied the well known differential eauation:
The Ultra-Rapid Testing of Rubber. The Testing of its Oxidizability in One Quarter of an Hour
Authors: Dufraisse Ch , Bras J. Le
Published: February 2011

It is hardly necessary to go into further detail to demonstrate the great advantages of such a test when used in a practical way. In the control laboratory, it will supplement and confirm the various other routine tests and, most important, immediately detect an error which the other tests will not do, particularly the omission, insufficiency or incomplete distribution of antioxygen. It will also reveal the presence of harmful impurities. For specifications and in manufacture, it will enable the article itself to be tested, either by removing a small piece or by providing a cavity for this purpose in the mould. Of course it is not necessary to limit the testing time to a quarter of an hour. If greater differences in the manometric levels are desired, the oxidation curve may be continued for a longer period, one hour, for example. Finally this oxidizability test at 120° C. would appear to fulfill the requirements of rapidity and precision of control testing, at least in the present state of stability of rubber products. Only in case of greatly increased resistance to oxidation would it be necessary to prolong the test for more than one quarter of an hour.
Forced and Spontaneous Changes in the Arrangement of the Molecules in Stretched Rubber. Crystals and Fused Phase in Stretched Rubber
Authors: Thiessen P. A. , Wittstadt W.
Published: February 2011

An unsaturated hydrocarbon of the formula (C5H8)2x is the basis of natural rubber. Although there are still differences of opinion about the size of the molecules, it may nevertheless be accepted as fairly certain that the parent substance, the unsaturated hydrocarbon, is composed of a mixture of various steps of polymerization. At ordinary temperatures and under no mechanical stress, both vulcanized and unvulcanized rubber are isotropic glasses. Exposed to x-rays they give the diagram of an amorphous substance, i.e., a broad, diffuse ring. As a result of mechanical deformation, especially stretching, rubber becomes anisotropic. This anisotropy is manifest by the appearance of optical double refraction, as well as by an x-ray fiber diagram, which replaces the amorphous ring. This indicates orientation of the molecules and rearrangement into a space lattice, measurements of which have been made repeatedly and which make probable a rhombic structure.
An Apparatus for Measuring Compressibility and Permanent Set of Rubber and Rubber-Like Materials at Various Temperatures
Authors: Hoekstra H. A. , Hoekstra J.
Published: February 2011

The importance of rubber and rubber-like substances for packings as shock-absorbers between parts of machinery, in short, the use of rubber under compression in mechanical construction is continually increasing. Several methods have already been proposed to investigate the behavior of rubber under these conditions, and the most ingenious method seems to be a two-dimensional stretching of rubber films in the form of balloons (Sheppard and Clapson, Ind. Eng. Chem., 24, 782 (1932)). This deformation is identical to homogeneous compression if volume changes by the deformation may be disregarded. The latter does not hold true if inactive fillers are used, which give rise to vacuoles in stretching but not in compression. However, in practice homogeneous compression is rare, as the material will never be able to glide without friction along the compressing parts to which in many cases the rubber is vulcanized. Because of the complicated deformation of rubber in practice, it is necessary to imitate the real conditions under which compression takes place. for these reasons a simple compression of cylindrical specimens between parallel plates was chosen as a first basis for the investigations.
A New Method of Investigation in the Evaluation of Fillers for the Rubber Industry
Authors: Behre Johannes , Göhde Karl
Published: February 2011

The busy technologist in the rubber industry is continually faced with the problem of choosing, by ready and simple means, the fillers best suited to his needs from the endless number offered him. In many cases there is no information at all about their composition or activity. In examining a filler it is necessary therefore to determine first of all whether it conforms to chemical requirements; whether for instance, it contains any substance poisonous to rubber. The degree of fineness must also be determined. Only if these tests are satisfactory is the filler given its final and conclusive test in a rubber mixing. Obviously there is little time to carry out such a series of tests in a systematic way, so in most cases a standard mixing is chosen to serve as a means of judging a filler. It is however well recognized that it is very difficult to reach any satisfactory conclusion by such a procedure, since only relative values are obtained, i.e., the values must be compared with those obtained with other fillers. Furthermore in such a test it is almost impossible to maintain the experimental conditions as constant as is necessary when it is intended to compare the results of two series of measurements with one another. It is readily understandable therefore that for a long time rubber technologists have wished for some kind of method which would make it possible to measure in absolute terms the activity of a filler in rubber.
A Mechanical Oscillograph for Routine Tests of Rubber and Rubber-Like Materials
Authors: Yerzley Felix L.
Published: February 2011

The oscillograph described has been developed primarily as a laboratory instrument to evaluate rubber and Neoprene compounds for mechanical applications. It is complete in itself as a means of measuring all of the quantities inherently involved in such service in units which are understandable to rubber technologists and mechanical engineers alike. It is hoped that it may serve its purpose by bringing into closer cooperation those who make and those who use rubber springs. The details of the test have been carefully developed, and it is expected that the machine and standard test-specimen described will not need essential modification for routine use. However, enough background has been given so that the machine may be modified in accordance with definite principles in order to gain greater load capacity if required. The test has been restricted thus far to compression. The author expects to adapt the machine to tests in shear, and by correlation between shear data and compression data to obtain figures capable of substitution in relationships already offered by other investigators for calculations in the applications and design of rubber springs. This field of calculation is complicated and in an early state of development, but by the use of the oscillograph it should be easier to obtain the quantities of information required to clarify our understanding of the mechanical characteristics of rubber-like materials within the range of deformation encountered in structural use.
Sol and Gel in Hevea Latex and Crude. Rubber Influence of Oxidation on Gel-Sol Transformation
Authors: Kemp A. R. , Peters H.
Published: February 2011

An apparatus and procedure to determine the amounts of sol and gel rubber in dried latex films and crude rubber have been described. It is shown that whereas plantation smoked sheet and crepe contain large and varying quantities of rubber soluble in petroleum ether, dried rubber films from latex are practically free from sol rubber when oxidation has been avoided. Latex increases in sol rubber content when subjected to various treatments permitting oxidation of the hydrocarbon. It appears from this work that the rubber in the form of latex is very susceptible to oxidation, which however involves only minute quantities of combined oxygen. When latex film rubber is subjected to creeping, it shows an increased content of sol rubber corresponding to that of crepe. A short milling of crepe was found to convert it completely into sol rubber. This confirms the gel-sol transformation mechanism of breakdown. Gel rubber from dried latex films is swelled to a maximum of 1500 to 7800 per cent but is not dissolved when placed in benzene, chloroform, carbon tetra-chloride or carbon disulfide and allowed to stand for several days. Gel rubber becomes soluble and therefore diffusible in these solvents as a result of oxidation. It was found that dried latex film and various types of crude rubber swelled to a maximum of 1000 to 2400 per cent in petroleum ether and that this swelling was not proportional to the sol content. This investigation strengthens the belief that sol rubber is an oxidation product of gel rubber. The formula for sol rubber is suggested as (C5H8)nO2, and a relationship between the molecular weight and the oxygen content is postulated on the basis that oxygen acts as a molecular splitting agent for both gel and sol.
Composite Nature of the Stress-Strain Curve of Rubber
Authors: Williams Ira , Sturgis B. M.
Published: February 2011

The stress-strain curve of rubber can be imagined to consist of three curves which tend to approach straight lines. The first curve has a high elongation load ratio and intercepts the second portion at an elongation which depends on the temperature. The second curve is parallel to the elongation axis and represents a condition of flow. The third curve has a low elongation to load ratio and represents rubber with a high load carrying capacity. It is evident that the second curve must be avoided as much as possible in most industrial applications. Most industrial applications require the rubber to work only within the limits of the first curve. The first curve is lengthened when the temperature is increased and the rubber can work efficiently to a higher elongation. No evidence has been found regarding the nature of the change which occurs in rubber during the period of flow. Since the flow is reversible, it must be within the molecule and not between molecules.
The Resistance of Rubber to Dynamic Forces Part I
Authors: Ariano R.
Published: February 2011

The subject of the present paper, which is of great interest on account of the numerous service conditions under which rubber is subjected to dynamic forces, has received little attention, perhaps because of the complexity of the phenomena and the consequent difficulty of coming to any definite and significant conclusions from experimental data. It is a widespread belief, for instance, that in static tension plastic flow takes place and that this is responsible for the Joule effect and that it modifies the shape of the stress-strain curve. By working at high velocities of extension, Williams proved that at room temperature and also at 60° C the stress-strain curves are straight lines and that complete elastic recovery takes place. The importance of verifying such a conclusion as this is obvious. Since, in fact, the elongations for a given load found by Williams were in every case greater when the stress was static, one is led to the conclusion that the deformation brought about by a given load is the sum of two components; one a perfectly elastic component, which obeys Hooke's law and which therefore is applicable to the established science of construction; a second component, which, in contrast to the first, is plastic in character and consequently depends on the duration of application of the load and on the loads previously applied. In brief, the law of deformation should be capable of reduction to the laws of two types of systems, viz., an elastic system and a plastic system. Unfortunately however this assumption could not be confirmed.
Rubber Stretched by Forces in Two Directions Perpendicular to One Another
Authors: Ariano R.
Published: February 2011

In previous publications the author has defined by means of relatively simple expressions, the behavior of rubber under tension and under compression. However, as was mentioned in a book entitled “Finite deformations” by the author, it is not possible to develop a theory of elasticity for highly deformable objects, which have their prototype in rubber, unless it is known how they behave when each element is acted upon by the primary three forces which, according to the theory of finite deformations, as well as the ordinary theory of elasticity or again the theory of infinitesimal deformations, are sufficient to define each state of tension. With regard to the last theory, the linear relation between deformation and stress makes it possible to accept the principle of the superposition of simultaneous forces, i. e., to add algebraically all coexistent forces and deforma- tions. However, this is obviously impossible for finite deformations, for which the linear relation in question has not been confirmed. Rather than proceed on the basis of hypotheses to develop theories and to verify them by deductions, it seemed more reasonable to undertake an experimental investigation, which later would serve as a background for the theoretical development of the problem. As a beginning, the case of the coexistence of two principal stresses in a relatively thin film has been considered. The experimental results are described in the present paper and will be discussed in a forthcoming paper.
The Problem of Crude Rubber
Authors: Thomas A.
Published: February 2011

In recent years, rubber manufacturers have made tremendous progress in compounding and in methods of manufacture, yet they continue, as they always have done, to regard smoked sheet and crepe from the plantations as the essential raw material of their industry. As a matter of fact, however, latex is the essential raw material, and the changes which it undergoes on the plantations are among the factors which influence the quality of the final rubber and therefore play a part in its possible uses. In the face of this, it seems like a paradox to say that the processing of latex on the plantations is based on arbitrary methods, without any consideration taken of their effects on the properties of the finished rubber, whereas mixing and vulcanizing operations are scrupulously controlled by manufacturers. For what reason does this paradoxical situation continue to prevail? Only because of the way by which the broker still evaluates rubber. The plantations are obliged to classify their commercial product into different types, according to color, superficial appearance, cleanness and the presence or absence of bubbles in sheet rubber, with complete disregard to its intrinsic properties, the latter not even being measured. To be regarded as the best quality, commercial rubber must be of a uniform color, must have a regular surface and must contain neither impurities nor bubbles.
Specific Gravity of Latex and of Rubber
Authors: Smith H. Fairfield
Published: February 2011

From observations on specific gravity and dry rubber content of latex, of centrifugal concentrates, and of latex-water mixtures, a number of attempts have been made to deduce the specific gravity of the rubber phase. Such estimates, after allowing for criticisms and adjustments which have been put forward, range from 0.901 to 0.914. But writers have made no attempt to consider how their calculations would be affected by treatments of the latex such as ammoniating and centrifuging, by different ways of evaluating the results, and by variations in temperature. When consideration is given to such matters almost all observations published during the last 20 years are found to be in good agreement one with another. Specific gravity, the ratio of the mass of a certain volume of a substance, at temperature t2, to that of the same volume of water, at temperature t1 is commonly designated dt2t2. To avoid excess affixes, when the temperature of the substance does not require to be stated, let:
Second Report of the Investigation of the Crystallization of Crude Rubber
Authors: Park Chullchai
Published: February 2011

Very recently the writer observed a small residual elongation in a stretched ribbon of smoked sheet rubber brought about by freezing, and it was found that the maximum residual elongation occurred after stretching about 200–300 per cent of the original length, and also that there was almost no elongation after stretching higher than about 700 per cent. To explain the behavior of crude rubber by crystallization, including these facts, it was assumed that the long chain molecules of rubber are in the form of large irregular spirals.
Heat Conductivity of Rubber at Low Temperatures
Authors: Schallamach Adolf
Published: February 2011

While examining the possibilities of applying rubber in low temperature work, we were hampered by the lack of available data on its physical properties at low temperatures. We were aware of the difficulties to be expected in making accurate measurements in that temperature region, and this applied especially to the heat conductivity, in which we were particularly interested. To obtain at least an estimate of the order of magnitude, we carried out some measurements of the heat conductivity of commercial rubber (North British tire rubber) at room temperature and at the temperature of liquid air.
Synthetic Rubbers: A Review of Their Compositions, Properties, and Uses
Authors: Wood Lawrence A.
Published: February 2011

Synthetic rubber has been the dream of many during the century which has passed since Faraday first determined the carbon-hydrogen ratio in natural rubber, but it has completed only about a decade of commercial success. Every year of the past ten has seen an increase in the quantity produced, the number of varieties available, and the number of applications. The aims in various countries have been different, and the development has proceeded in different directions. The most active research has been carried on in Germany, Russia, and the United States. There has been relatively little collection and intercomparison of the rather limited data on the physical properties of the different varieties of synthetic rubber. Scientific articles have been largely devoted to descriptions of single varieties or to discussions of limited phases of the work with respect to one variety. The present paper represents an attempt to make a summary of the facts regarding the different varieties, an intercomparison of some of their properties, as reported in previous publications, and to present a fairly complete bibliography of the modern literature on the subject of synthetic rubber. Because of the relatively short time during which the different varieties of synthetic rubber have been available, the data concerning them have been reported almost entirely by observers in the laboratories of companies each interested in the manufacture and sale of a particular variety. In almost every case, therefore, the figures necessarily lack independent confirmation.
Color Reactions between Clays and Amines
Authors: Hauser E. A. , Leggett M. B.
Published: February 2011

The formation of colored compounds on clay has been shown to be the result of a reaction between clay and aromatic amines. The influence of various substituents, acid and bases, is discussed. A preliminary hypothesis explaining the mechanism of the reaction is advanced and further work outlined.
Surface Area and Properties of Carbon Black
Authors: Smith W. R. , Thornhill F. S. , Bray R. I.
Published: February 2011

The surface areas of a number of commercial carbon blacks have been determined by the low-temperature adsorption isotherm technique. Thermal decomposition and other nonimpingement type blacks possess areas of 15 to 64 M2 per gram. Channel blacks commonly employed as reinforcing agents in rubber have areas around 100 M2 per gram. Ink and color blacks range from 100 to nearly 1000 M2 per gram. The color values of these carbons increase with surface area. The relation of iodine and diphenylguanidine adsorption to surface area has also been studied. Iodine adsorption is a direct function of surface area and, with the exception of certain high-volatile blacks, may be used as a direct measure of total surface. The adsorption of diphenylguanidine depends much more strongly on the volatile content of the black rather than its total surface. While rubber reinforcement depends in a general manner on surface area, certain blacks of nearly identical surface vary widely in the properties they impart to compounded rubber. That the state of the surface is probably of equal importance is indicated by the fact that the activity of the surface, as judged by relative ease of oxidation, may vary widely in blacks of equal area.
Crystallization Phenomena in Raw Rubber
Authors: Treloar L. R. G.
Published: February 2011

The process of crystallization in raw rubber held at various extensions at 0° C has been studied by following the accompanying changes in double refraction and in density. From a comparison of the two sets of data, it is concluded that a very low extension produces a relatively high degree of orientation of the axes of the crystallites in the direction of the extension. From 100 per cent extension to the breaking-point, the increase in birefringence with elongation is due almost entirely to an increase in the proportion of crystalline rubber present; over this range the birefringence therefore gives a quantitative measure of the amount of crystallization. From the study of birefringence at 25° and 50° C, it appears that crystallization sets in rather rapidly at a certain intermediate elongation, and then increases continuously to the breaking-point. The observed changes in crystallization show a close correlation with plastic flow and elastic recovery phenomena. The bearing of these observations on the molecular structure of rubber and its mode of crystallization is discussed. It is estimated that the increase of density of rubber on crystallizing is not less than 3.75 per cent.
The Impregnation of Cotton Yarns with Latex
Authors: Nederveen Gvan
Published: February 2011

1. Thin sections of yarn impregnated with rubber can be made in a simple manner according to the modified Kronacher-Lodemann method here described; and fibers, rubber, and embedding material can be clearly distinguished. 2. Impregnation of a cord with latex in which a wetting agent is dissolved results in a far lower degree of penetration by rubber than impregnation with latex following treatment of cord with a solution of the wetting agent. 3. When the proper conditions and wetting agent are selected, bicycle tire cord previously treated with a wetting agent can be completely impregnated with latex. 4. There is a definite relation between the microscopic picture indicating the degree of penetration of rubber between fibers and the results of fatigue tests.