bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Evaluation of Raw Rubber
Authors: Martin G. 
Published: February 2011

Abstract
The purchase of supplies for a rubber factory often involves a decision as to the relative merits of different samples of raw rubber. In view of the variety of needs the method of arriving at a decision must be left to the wisdom of the technical staffs concerned; but when a large portion of the output from the East is involved, affecting producers and manufacturers everywhere, it is desirable to discuss fully the methods employed to ensure that the final decision is as wise as its importance warrants. A problem affecting the whole of the rubber industry has now arisen in the East in connection with the preparation of smoked sheet. Firewood for smoking is becoming more difficult to obtain, and already some estates have been compelled to consider the production of an alternative form of rubber. As the Tropics become more cultivated, the acuteness of the problem will increase, and unless some change in the method of production occurs, sheet will tend to be replaced by crepe. It is presumed that there is a demand for sheet apart from crepe and that each form of rubber serves a purpose which the other cannot fulfil; but there is no clear and authoritative indication from manufacturers as to the differences which make both forms of rubber essential. it is of interest to point out that apart from form, color, odor, and reaction to swelling agents, there is no test which would distinguish between high grade sheet and crepe rubber unless both are prepared from the same latex, in which case sheet has a slightly higher content of mineral matter (Bull. Imp. Inst., 21, 303 (1923)) and a greater tendency to absorb moisture from the atmosphere (de Vries, “Estate Rubber,” 1920, p. 340), and possibly better aging properties (Martin, Trans. Inst. Rubber Industry 2, 354 (1927)). It is not proposed to discuss the relative merits of sheet and crepe although the subject is an illustration of the difficulty of evaluating raw rubber so as to obtain results which are in agreement with the ideas and experience permeating the industry. To the planter there appears to be a demand for sheet as well as for crepe, and he purposes to meet that demand if it is at all possible.
The Surface Tension of Rubber Solutions
Authors: Shacklock G. W. 
Published: February 2011

Abstract
During the past few years much attention has been paid to the constitution of raw rubber. The much improved methods of production of plantation rubber have resulted in a reasonably pure product available for investigation, and chemical analysis undoubtedly shows an empirical formula of C5H8 for the hydrocarbon. From this point onward, knowledge becomes less certain. Osmotic pressure and molecular weight measurements give no confirmation of a simple molecular structure, but show, in benzene solution, a behavior comparable with that of colloids. This is supported by experiments on swelling and viscosity, and by ultramicroscopic examination, all of which lead to the conclusion that rubber is a lyophilic colloid. Hence arose the concept that the rubber particle is a polymer of simple molecules of formula C5H8 (possibly isoprene), such a structure being in agreement with the production of rubber-like substances by the action of sodium upon isoprene and butadiene (Harries, Annalen, 395, 211 (1912)). The decrease in viscosity of a rubber solution with increasing periods of mastication of the rubber is hence regarded as a measure of depolymerization due to mechanical action; the increased ease of solution after mastication is confirmatory evidence.
Effect of Storage on Milled Crude Rubber
Authors: Carson C. M. 
Published: February 2011

Abstract
Smoked sheets which have been milled to different degrees of plasticity and stored in bale form for periods up to 9 months show a decided increase in modulus, plasticity, and recovery values. The increase in recovery value is the most noticeable, the change being 180 per cent of the original, if the rubber is baled at 40–50° C. and stored at 10–20° C. for 9 months. When the aged, milled rubber is mixed in a tube stock and processed on a tubing machine, the stock is rougher and the speed of extrusion is slower than a similar stock containing freshly milled crude rubber. The plasticity of stocks which are subjected to tubing operations is shown best on an extrusion type plastometer in preference to the compression type. Milled crude rubber “freezes” at temperatures below 0° C. and thaws at room temperature of 15–25° C. It may be permanently frozen by being placed under slight pressure for several months, freezing temperature being unnecessary. In either sheet or milled form this type of frozen rubber requires a temperature of about 50° C. to thaw, whereas temporarily frozen rubber will thaw at room temperature.
Rate of Deposition of Latex on Porous Molds
Authors: Greenup H. W. 
Published: February 2011

Abstract
The effects of pressure, rubber concentration of latex, temperature, and hydrogen-ion concentration upon the rate of deposition of latex on porous molds are described. Pressure, rubber concentration, and temperature were found to be negligible factors in comparison with hydrogen-ion concentration. By adjusting the pH of the latex to 6.1 it was found possible to obtain aggregation of the latex particles and a marked increase in rate of deposition. THE manufacture of rubber articles by dipping porous forms in latex was first described by Condamine (5). He reported to the Paris Academy in 1736 that the natives in South America made such articles as shoes and bottles, using clay molds which, after drying of the deposited layer, were shattered and removed. The idea of making articles by a process of this sort, instead of by coagulating the latex, milling, and then shaping the milled rubber, appeals to the imagination. Increased tensile strength and improved aging have been claimed (10) for articles made directly from latex, and their remarkable resistance to tear, obtained under certain conditions, is well known.
Isoprene and Rubber. Part 26. Hemicolloidal Hydrorubbers
Authors: Staudinger H. , Geiger E. , Huber E. , Schaal W. , Schwalbach A. 
Published: February 2011

Abstract
The reduction of rubber without solvent takes place only at 270°, according to experiments by Fritschi. Below this temperature rubber is reduced only with difficulty and incompletely. In the dissolved eondition, on the contrary, Pummerer and Burkard showed that rubber can be reduced at ordinary temperature. In an earlier communication it was accordingly assumed that on heating a cleavage of secondary colloid particles into primary ones (into macromolecules) takes place, and that heating, therefore, has about the same effect as strong dilution. A distinction was made between primary and secondary particles, and it was assumed that the strong diminution in viscosity which is observed in dilute rubber solutions depends upon a cleavage of the secondary colloid particles, just as do the decreases in viscosity which rubber undergoes upon heating, and which have been generally described as depolymerization. These earlier ideas of ours are, however, incorrect. An extensive cracking of the rubber molecules takes place upon heating, and this was more carefully investigated by Geiger and later by Bondy. In this way reduction is facilitated. With strong dilution, on the other hand, the rubber solution passes from the gel state to the sol state, the rubber passes into normal solution, and therefore reduction can take place more easily in a dilute solution than in a concentrated one. With reduction by heat, therefore, a derivative of unchanged rubber cannot be expected; instead the hydrorubbers obtained, for example, those first prepared by Fritschi, are not reduction products of rubber itself, but are hemicolloidal decomposition products of the latter. Only by careful reduction in cold solution can one succeed in obtaining a hydrorubber in which the rubber molecules remain unchanged.
The Reinforcing Action and Other Properties of Titanium Fillers in Rubber Stocks
Authors: Bodger W. H. , Cotton F. H. 
Published: February 2011

Abstract
(1) The reinforcing properties of a high-grade titanium white, containing 74 per cent barium sulfate in intimate combination with the oxide, are slightly better than those of “White Seal” zinc oxide in mixes vulcanized with diphenylguanidine. (2) Titanium dioxide is generally inferior to titanium white as a reinforcing agent, and at high loadings gave poor tensile properties, especially in compounds accelerated with mercaptobenzothiazole. (3) The titanium fillers are incapable of behaving as activators of organic accelerators, as zinc oxide does, and from 3 to 5 per cent of zinc oxide is required in the majority of titanium stocks containing organic accelerators. (4) The aging properties of compounds reinforced with titanium fillers are generally similar to those conferred by zinc oxide, but are inferior to the latter at low volume loadings. (5) Better pigmentary and water-resisting properties are conferred by titanium dioxide than by titanium white, and both these fillers are superior to zinc oxide in these respects.
Water Absorption by Rubber. Part II. Vulcanized Rubber
Authors: Skinner S. J. , Drakeley T. J. 
Published: February 2011

Abstract
(1) The process of vulcanization decreases the amount of water absorbed by rubber. (2) Rubber containing a high percentage of protein material will not after vulcanization necessarily absorb more moisture than rubber with a lower nitrogen content. (3) Of the accelerators, diphenylguanidine induced the lowest water absorption and zinc diethyldithiocarbamate the highest. Both litharge and the ultra-accelerator showed higher absorptions than the unaccelerated base mix. (4) After a small initial rise there is a general decrease in water absorption with time of cure. A minimum absorption is noted at, or just after, optimum cure; the amount absorbed increases again after optimum and high absorptions occur with overcured rubber. (5) Zinc diethyldithiocarbamate shows the greatest increase in absorption with degree of overcure. Diphenylguanidine gives a vulcanizate, the absorption of which is rather insensitive to time of cure. (6) The incorporation of fillers lowers the absorption of water.
Rubber and Thioglycolic Acid
Authors: Holmberg Bror 
Published: February 2011

Abstract
Based on its behavior toward halogens, hydrogen halides, nitrous acid, ozone and hydrogen, rubber has one double bond for each C 5H 8 group. One would therefore expect that it would be possible to obtain from the addition products of these substances new compounds which would throw considerable light on the constitution of rubber. With the exception of the ozonides, however, this is true only to a very limited extent, a fact which depends in part upon the almost complete lack of water-soluble derivatives suitable for further reactions. It is true that the bromide of rubber can be converted by phenols into alkali-soluble compounds, but the carbon bonds of the compounds appear to be formed not only between the components but also by a closing of the ring within the rubber skeleton. Moreover in the transformation of the bromide by triethyl phosphine cyclicization appears to take place. In view of this, the constitution of these derivatives indicates that further work with them would be to little purpose, and as a matter of fact until now almost nothing of any great interest has appeared.
Some Aspects of Plasticity and Its Determination
Authors: Usherwood G. W. 
Published: February 2011

Abstract
In recent years the importance of plasticity in determining the ease with which a rubber stock can be processed has become increasingly realized, and several methods for its measurement have been devised. Before examining any of the methods employed for its measurement, it is advisable to consider what is meant by plasticity, since much loose and contradictory usage of the term exists in the rubber industry. The common meaning of plasticity refers to those characteristics of matter which have to do with the receiving and holding of form. A body is said to be plastic or possess plasticity when it can be permanently deformed by any force exceeding a definite minimum. The difference between a viscous substance such as pitch and a plastic substance such as clay is that the former slowly changes its shape under the smallest applied load, that is, its own weight, while the latter requires some force above a minimum before it will deform. In practice one must distinguish between two substances which, although soft and yielding with equal ease to any deforming force, differ widely with the fidelity with which they retain the deformation imparted. One may retain its deformed shape accurately and permanently, as, for example, a piece of sculptor's clay, while the other may, after some interval of time which may be long or short, resume to a considerable extent its original form, as, for example, a piece of masticated rubber. In the first case the clay is said to be more plastic than elastic, while in the second the rubber is said to be both plastic and elastic.
The Solvation of Rubber Sols
Authors: Lens J. 
Published: February 2011

Abstract
The purpose of this investigation was to get some idea of the role played by solvation in organo sols. However, we wish to state first that we do not bind ourselves to a special theory. Accordingly we give these systems the name sols simply because we cannot speak of them without giving them a name. It may be that the name “solution” is a better one, but for our purpose it does not make the slightest difference whether the rubber is dispersed in the medium as molecules or as aggregates of molecules. Hence we do not want to discuss the molecular structure of the rubber particles in detail. There are many methods of measuring the degree of solvation, but they almost never give quantitatively the same results, which cannot be expected at any rate. Previous investigators have used the greatest part of these methods with more or less success. The best known are the investigations of Posnjak on the swelling-pressure of rubber in organic solvents. Furthermore, many investigators have measured the viscosity of rubber sols. But while it is likely that the law of Poiseuille does not hold, and that these sols are plastic, it will be very difficult to interpret the values so obtained in the right way. Recently Stamberger measured the vapor pressure of rubber sole and got a good agreement with Posnjak's values. However, Stamberger did not extend his measurements to concentrations between 67 per cent and 100 per cent rubber, probably because he was looking for this agreement only.
Experiments on Oil-Proof Rubber
Authors: Ishiguro Katsumi 
Published: February 2011

Abstract
Tests of rubber mixtures compounded with nine different accelerators indicated that those with relatively great hardness have relatively little absorption and those with less hardness have more. Rubber products which are not required to be particularly soft can be made with fairly good oil-resistant properties by the proper selection of accelerators and by vulcanizing to the optimum point.
The Effect of Particle Size of Zinc Oxide on the Physical Properties of Rubber
Authors: Haslam G. S. 
Published: February 2011

Abstract
The particle size of the pigment may be expressed in terms of several average diameters, depending on the method of measurement. In this work three of these averages were considered; namely, d1, which is the arithmetical mean, d3, which is the average diameter from which specific surface is calculated, and D, which is the average diameter from which the number of particles per gram is calculated. A series of samples was prepared and these three average diameters were determined These samples were then compounded with rubber and several physical properties measured. As a result of these tests it is shown that, in general, the physical properties vary directly as the specific surface and the number of particles per gram. However, if the number of particles per gram is maintained constant and the specific surface is varied, it was found that the physical properties vary directly as the specific surface. No such relationship was found when the specific surface was maintained constant and number of particles per gram varied. It is further pointed out that the only satisfactory means of measuring the d3 diameter, and therefore the specific surface, is by some microscopic method which determines the size-distribution curve for the pigment.
The Abrasion Question. Some Factors in the Deterioration of Rubber When Exposed to Frictional Contacts with Other Materials
Authors: Cosler V. A. 
Published: February 2011

Abstract
If we accept the proposal that the fundamental effect produced by the machines diagrammed in Fig. 1 is that of dragging a series of saw-toothed paddles across the surface of rubber specimens, we must accept as fact the theorem that the results recorded by these types of machines is a summarization of values rather than a fundamental value. If we accept the evidence that relations cannot be varied on any type of present abrasion testers to duplicate the conditions existing in all situations where rubber is exposed to frictional contacts with other materials, we must accept the fact that some fundamental factor is absent, or is over- or under-emphasized as these relations are varied. Whether these missing reactions can be supplied by evaluating other characteristics which will properly modify the results obtained on any given abrasion tester is an open question. It can be safely stated, however, that results obtained from any type of tester discussed can only be considered as evaluating rubber compositions at or near the point of optimum cure under one particular set of wear conditions. With one exception these conditions may safely be considered as approximating the conditions obtaining between a tire tread and the road under normal operating conditions. The Sproul-Evans tester may safely be considered as more closely approximating sand-blast hose conditions than tire-road conditions. It is the thought of the author that the most promising field of future endeavor lies in the direction of studying the possibility of reproducing more fundamental effects, rather than attempting to add more reactions to the already complex set of conditions present in the known types of abrasion testers. The suggestion is also offered that a most promising field of study lies in the direction of studying the modifying effect of distortion upon the fundamental characteristics of rubber, and attempting to establish the extent of distortion present when rubber is exposed to frictional disintegration in actual service conditions.
Structural Viscosity in Some Lyophilic Sols. II. Rubber Sols
Authors: Gallay Wilfred 
Published: February 2011

Abstract
The relative viscosities of sols of natural and purified rubber in benzene were measured at varying pressures, using the overflow viscosimeter. Deviations from Poiseuille's law to varying extents were found in all cases, with regions of structure and turbulence at various pressures. The limiting concentrations above which structure is evident and Poiseuille's law is not obeyed were found to be in agreement with those calculated by Staudinger on the basis of his theory of the relation between the viscosity and molecular weight of polymeric molecules. Exposure to ultra-violet light was found to decrease considerably the viscosity of a sol of purified rubber.
A Multi-form Plastometer
Authors: Lefcaditis G. D. 
Published: February 2011

Abstract
The methods of measuring plasticity are usually divided into two classes, that applying the principle of extrusion, and that based on compression. There is no considerable difference between methods based on extrusion. The compression methods, however, have been subdivided into categories, such as constant volume of tested material and hence decreasing pressure, or constant area and pressure, etc. It is not the object of the present article to enter into a critical discussion of the theories underlying the various methods. Such attempts are numerous in recent publications. (Griffiths, Trans. Inst. Rubber Ind., 1, 308 (1925); Martin, Ibid., 6, 298 (1930); De France, Ind. Eng. Chem., 23, 824 (1931); Scott, Trans. Inst. Rubber Ind., 7, 169 (1931); Behre, Kautschuk, 8, 2 (1932). If reproduction of figures given in the literature is desired, it is necessary to process the particular modified plastometer by which flue figures in question have been obtained. The compression plastometers being probably the most extensively used nowadays, it was thought that an instrument could be designed which would incorporate the various modifications of the compression plastometer, thus obviating the need for several instruments. In this paper such an instrument is described. An additional feature is a revolving disc, which is of convenience in preheating the test samples.
Some Observations on Rubber Testing
Authors: Scott J. R. 
Published: February 2011

Abstract
The subject of rubber testing and its standardization has received so much attention in recent years, that some apology might seem necessary for discussing it further. A few years ago the present writer had occasion to call attention to several respects in which existing test methods showed unnecessary lack of uniformity (Trans. Inst. Rubber Ind., 5, 139 (1929)), and it must be admitted that this lack of uniformity still persists to a great extent, with a corresponding loss in the value of published test results. It is the object of the present note to call attention more particularly to some unsatisfactory features in the selection of the “best” or “optimum” cure of a mix for purposes of comparison with other mixes. It is scarcely necessary to emphasize the fact that in comparing the properties of different mixings, as in examining the effects of fillers, accelerators, antioxidants, softeners, etc., all the mixings must be vulcanized to comparable states of cure. Nevertheless, an examination of published data shows that often insufficient attention is paid to ensuring strict comparability. For instance, it is not uncommon to find the effect of fillers examined by taking an accelerated base stock, adding the fillers to it, and vulcanizing all the resulting mixings for the same time, it being assumed that the fillers do not affect rate of cure. This assumption is not justifiable, even in the case of seemingly inert materials. An obvious case is that of gas black, which, though chemically inert, retards vulcanization in presence of organic accelerators. Moreover, such “inert” materials as barytes, blanc fixe, whiting, and strontium sulfate may markedly alter the rate of cure. Thus, in some experiments made by the writer, a base mix accelerated with dephenylguanidine (0.75% on the rubber) gave optimum mechanical properties after 90 minutes at 141° C., but mixings containing the fillers mentioned had optimum curing times ranging from 65 to 110 minutes. The writer has, indeed, come across a filler consisting of a very inert compound, which nevertheless completely puts out of action the most powerful organic accelerators. It is thus clearly unsafe to assume that any material will be inert as regards its effect on rate of vulcanization, whether in presence of an organic accelerator or not.