bluuebunny/crossref_metadata_2025 huggingface dataset:
Latex Contaminated with Copper Compounds as a Source of Danger of Fire
Authors: Fol J. G. , de Visser W.
Published: February 2011

A textile factory in Holland made double texture cotton fabric by applying a layer of latex to one of the fabrics and passing both fabrics through a calender, after which they were dried and pressed together. From the calender the double texture was rolled up immediately without previous cooling and the big rolls were stored. Shortly after storage a smell of burning was noticed in the store-room, and on closer inspection it appeared to emanate from the rolls. On opening these rolls it was found that the color of the fabric had turned from white to light brown. The cloth had lost its suppleness and could be readily torn. In the interior of the roll the cloth was scorched and even locally charred. One got the impression that the rubber in the cloth was severely oxidized, i. e., resinified. The problem to be solved was what caused this strong oxidation, which eventually led to spontaneous combustion. According to information received from the mill, the latex was placed in a brass tank and it also came in touch with a brass roller. From further information it became evident that the ammonia, which is added to the latex as a preservative, dissolved copper out of the parts of the machine mentioned. In this way the cloth was covered with a layer of rubber in which copper compounds were evenly distributed. As copper and copper compounds have an extraordinary accelerating effect on the oxidation of rubber and oxidize the latter in a very short time even at ordinary temperature, it was clear that the oxidation mentioned above was caused by the contamination of the latex with copper compounds.
The Effect of Heat on Raw Rubber in the Presence and Absence of Air
Authors: Fry J. D. , Porritt B. D.
Published: February 2011

During the process of milling or masticating rubber, three agents, namely, mechanical working, heat, and the constituents of the air, are evidently present which may be individually or collectively responsible for the resulting physical changes. The generally accepted explanation of the effects produced is that the mechanical treatment breaks down some form of structure existing in the raw rubber or rubber particles and consequently it is customary to describe material as “overworked” when milling has been carried too far, and to reserve the terms “burnt” and “scorched” for cases in which the heat generated in the process has caused premature vulcanization. The correctness of the assumption that milling is essentially a mechanical operation at first sight seemed to be supported by an experiment made by one of the authors in which the treatment was carried out under a stream of cold water when it was found that the solution viscosity of the material diminished in much the same way as in the normal process, the only apparent difference in the final product being the almost complete absence of the adhesiveness characteristic of milled rubber. Further consideration, however, suggested that though the conditions under which the test was made undoubtedly minimized contact with air and the development of heat, the possibility that oxygen might still play a part was not entirely excluded, while the fact that the bulk of the rubber was kept cold did not necessarily preclude local rises in temperature taking place in the material when passing between the rolls.
Some Features of Sulfur in Rubber Manufacture
Authors: Twiss Douglas F.
Published: February 2011

By a striking coincidence the element sulfur appears to have been associated with rubber as a dusting powder, for the removal of tackiness, for a considerable time before its unique vulcanizing power was discovered. The actual incorporation of sulfur into rubber by Goodyear in 1839 is consequently the less surprising although his discovery and its rediscovery by Hancock lose on that account no whit in importance. With all compounding ingredients for rubber, fineness of division is an important and desirable characteristic, and it is often assumed that the desirable degree of fineness is limited only by the cost of production. Sulfur, however, is exception in that for ordinary use with rubber the optimum limit of fineness of division can easily be exceeded. Very finely divided sulfur—probably on account of the known depressing influence of fineness of division of a substance on its melting point—often tends to cake undesirably during the mixing operation, and so may actually lead to an impaired dispersion relative to that obtainable with less finely powdered material. In spite of this limit to useful expenditure on further disintegration of sulfur for ordinary “dry mixing” with rubber, it must be admitted that such finely dispersed forms as milk of sulfur or precipitated sulfur, and various colloidal sulfurs are applicable with especial advantage in many of the newer “latex processes.” Small particle size here is favorable to the production of more stable suspensions or to the avoidance of settling. For the production of vulcanized latex, indeed, finely divided sulfur is particularly desirable; not only is the suspension of the particles here of importance, but also a fairly uniform distribution or partition among the rubber globules. Otherwise the vulcanized state may be attained by relatively few of the globules.
Color Reactions of Rubber
Authors: Pauly H.
Published: February 2011

WHILE the organic chemist, working with comparatively small molecules, can proceed directly by exact methods to an explanation of the structure of compounds, and therefore. considers color reactions of minor importance, these reactions often afford a convenient tool for the chemist who is investigating substances of very high molecular weight, which occur for the most part in nature. They offer a quick means of obtaining a preliminary idea of the presence of certain chemical groups, or of distinguishing between substances which can be identified physically only with difficulty. One would rob protein chemistry of indispensable methods were one to remove its color reactions. in the examination of natural substances they are a guide in the immense field of qualitative tests. Likewise, in research on rubber, the question to what extent it is to be considered a homogeneous substance greatly restricts the investigator in his methods of purification. Therefore, it would be of value to him to be able to control the course of his reactions through simple color tests. Such means have been unknown in rubber chemistry.
Power Variables in Milling and Mixing Rubber
Authors: Shoaff P. S.
Published: February 2011

OF THE expenses involved in the milling and mixing of rubber, the costs of materials and of labor are constantly subjected to the closest analysis. Economic drives are concentrated mainly upon them. Power, being a less tangible thing, often eludes the attention that is warranted by the profitable study of factors which may introduce savings. Frequently its cost equals or exceeds that for labor in a mill-room operation. When in a large factory there may be previously plasticized daily a half million pounds of crude rubber, when a half million pounds of master-batches are prepared, and when every day one and a half million pounds of compounded rubber stocks are mixed, power bulks enormously. Milling and mixing equipment to do that demands a power input of approximately 21,500 horsepower, or about 386,000 kilowatt hours. At one cent per K. W. H., as an example, this represents a daily cost of $3,860. With an average of 250 working days a year, the total reaches nearly a million dollars. The smaller manufacturer makes a proportionate outlay for power in these preparatory processes. So it would seem worth while to study power applications and those variables which may be turned to account in the search for greatest efficiency. Some points which may be mentioned are in part a review or confirmation of the findings of others which have appeared in published articles, other facts are from observations of very recent practice.
Experiences with Mixing Mill Roll Speeds and Speed Ratios, and Batch Sizes
Authors: Zimmerman Erle C.
Published: February 2011

THE remarks which I am about to make concerning mixing mills apply especially to 84″ mills ,with 26″ front rolls and 22″ rear rolls. Other sizes of rolls have been experimented with, and the results have been about the same as with the 26″ and 22″. The system of cooling used was that described by H. K. Jennings at the meeting of this group on February 15,* which consists of a spray pipe and open roll and a means for cleaning the inner surface of the roll. The mill was supplied with 10 gallons of 54° F. water per minute, with 5.5 gallons to the front roll and 4.5 gallons to the rear roll. The speed and ratio of mixing mills can be most clearly described in terms of roll surface speed and roll surface speed ratio. A great variety of surface speeds and surface speed ratios are in use at the present time. Front roll surface speeds as low as 75 feet per minute and as high as 135 feet per minute can be found, and ratios run anywhere from even speed up to front roll to rear roll ratio of 1:2. The effect of mill speeds and ratios on the mixing of stocks can be best determined by making a study of the temperature of the stock on the mill, the plasticity of the stock and the degree of uniformity of the mixing. Such information may be obtained on one mill equipped to give different speeds and ratios, or on several different mills of the same type. Whatever stock is to be experimented with should be mixed on the mill or mills in question for a few hours, after which several batches should be mixed, on which the average results are to be based. The same mill operators should be used, and the raw material should, of course, be standardized.
Plasticity and Elasticity of Rubber
Authors: van Rossem A. , van der Meijden H.
Published: February 2011

PLASTICITY determinations of raw and masticated rubber have in recent years attracted a great deal of the rubber chemists' attention, as the publications of Marzetti, Williams, De Vries, Griffiths and others have proved. In various laboratories, plasticity measurements have even become routine tests for raw and masticated rubber. There are, generally speaking, two methods of determining the plasticity of rubber, viz.: (1) The extrusion method, in which the masticated dough is extruded through an orifice (Marzetti), and the extruded portion weighed. This method can be used only for masticated rubber and rubber mixings. (2) The compression method, in which a piece of raw or masticated rubber is compressed and the decrease in thickness is measured. The latter method has been used in the past by many investigators for plasticity measurements of various substances, e.g., by Speedy, who as long ago as 1920 carried out plasticity determinations on gutta-percha, balata, and various bitumens with the Widney resiliometer, an apparatus based on the compression principle. Williams was the first to apply this method, in 1924, to the determination of the plasticity of rubber, and since then De Vries especially has made use of this method in his extensive investigations of the plasticity of raw rubber.
Researches on the Structure of Rubber
Authors: Bary Paul , Hauser Ernst A.
Published: February 2011

The theory according to which rubber consists of two components which normally are dissolved one in the other (Bary), is based on a number of physico-chemical observations, and is in general agreement with the results of x-ray work. The very nature of the x-ray diagrams substantiates the theory by introducing the idea that stretching rubber causes a separation of part of the dissolved component from its solvent (theory of Hauser and Mark). It may be concluded that rubber consists of a network of β-rubber which is capable of giving x-ray diagrams only when it is sufficiently condensed, that is, when its chains of carbon atoms have little freedom of oscillation. This result can be obtained either by freezing the rubber, which increases the proportion of the β-form, or by elongation, which expels the a-portion and concentrates the β-portion. This concept appears to explain all observations on the physical and mechanical properties of rubber.
A Scheme for Accelerator Classification
Authors: Dinsmore R. P. , Vogt W. W.
Published: February 2011

MUCH has been written about the constitution and chemical behavior of vulcanization accelerators. Theories have been advanced regarding the mechanism of vulcanization effected with their aid. Yet even the authors of such papers—presumably best qualified to interpret their contents—would hesitate to predict, from chemical structure, many of those features which are of practical interest to the rubber manufacturer. Nevertheless, an increasing number and variety of organic accelerators are being offered on the market, and it is not strange that the mind of the average rubber man is confused by the excess at his command and the conflicting claims of the distributors. In these circumstances it is natural to hesitate to undertake the somewhat formidable task of sorting and classifying. Fortunately, however, it is not necessary to do all the work of classification on a factory scale. Certain laboratory helps are available and can be used to reduce considerably the arduousness of the task. It is believed that an outline of such methods, a discussion of their significance, and a table of results, may be helpful to many in the industry, and it is for this purpose that this paper has been written.
Evaluation of Variable-Temperature Cures
Authors: Sheppard J. R. , Wiegand W. B.
Published: February 2011

Employing the generally accepted empirical rule that intensity of curing action doubles with a rise of 15° F., relations are developed between the several variables of a cure segment with a constant temperature gradient—viz., “intensity of curing action,” “curing effect,” time, and temperature—and the constants of such a cure, initial temperature and temperature gradient. Exact evaluation of cures is extended to schedules involving variable temperatures by the equations showing curing effect as a function of the other properties of a cure. These are the equations of chief practical importance. Curing effect, the measure of the net value of a schedule in effecting vulcanization, may be determined for a given schedule either by calculation from one of the “effect” equations, by direct reading from one of the several herein displayed graphs of effect vs. other properties, or by estimation of the area under an intensity-time curve.
Abrasion Tests of Rubber Stocks Containing Various Types of Carbon Black
Authors: Plummer W. B. , Beaver D. J.
Published: February 2011

With respect to the results noted herein an the relation of abrasion loss to size of abrasive material, it is regretted that as yet no results have been obtained which cast much light on the reasons for the break in the curves of Figure 1. It is possible, if not probable, that the unexpected phenomena whose existence is indicated by these results may be responsible for the commonly observed discrepancies between laboratory abrasion tests and road tests. It is hoped that further studies may give more useful information on this relation. The abrasion results on aged stocks present several important points. It is, of course, obvious and fully realized that abrasion in use takes place only on the surface layer of a tire tread, but attention has not before been called to the very considerable effect which the aging characteristics of the carbon black used in the stock may have on the abrasion resistance of this surface layer. The present results show that, with two stocks differing only in their carbon black content, the relative abrasion resistance of the surface layers after aging may be in reversed ratio to those of the unaged stocks. This evidently will be a decisive factor in the relative useful life of the tread if the rate of surface aging is greater than the rate of tread wear. Surface conditions or, in other words, the time of storage before use, the daily mileage, existing road and climatic conditions, etc., will determine this relation.
Carbon Blacks and Their Use in Rubber. III—Aging Effects
Authors: Cox L. B. , Park C. R.
Published: February 2011

The aging properties of compounded rubber stocks are affected by the carbon black which is used. The order of increasing superiority for the blacks tried is Super Spectra, Micronex, Charlton, Goodwin, and Thermatomic. The order of increasing superiority of accelerators is diphenylguanidine, hexamethylenetetramine, ethylidene-aniline, mercaptobenzothiazole. The last two are put in this order mainly because of the inferior original properties of ethylidene-aniline. Results of tensile, abrasion, and weight increase tests are in reasonably good agreement. The effect of acidity in any compounding material is neutralized in a stock containing zinc oxide. Stearic acid is without effect upon aging properties of cured rubber.
Softeners and Anti-softeners
Authors: Zimmerman Erle C. , Cooper Leslie V.
Published: February 2011

In the manufacture of rubber goods various materials are incorporated with the rubber in order to produce a mixture that will process more easily. Such materials are usually called fluxes or softeners. A simple method of determining the relative effects of such materials is described. This consists in mixing the material in rubber under standardized conditions and determining the plasticity of the product by the Williams method. Some materials show stiffening instead of softening action and both types are shown in the results reported in this paper. Benzidine and p-amidophenol are examples of materials which stiffen rubber. MANY materials used in the compounding of rubber exert an influence on the plasticity. Usually a material is specifically added to increase the plasticity and is called a softener, but in some cases the effect on plasticity is purely incidental to some more important function, such as acceleration or protection against deterioration on aging. The effect of this class of materials may be towards either a more or a less plastic mix; in the latter case it is correct to class the material as an antisoftener.
Reënforcement of Rubber by Fillers
Authors: Blake John T.
Published: February 2011

Wiegand's “Δ A” function, as represented by the double integral of tensile with respect to elongation and volume of a pigment over the base mix, is a practical means of expressing the reënforcing effect of the filler. On the other hand, the volume range over which the bonding of the filler is greater than the strength of the rubber matrix gives a better understanding of the condition of the filler in the rubber. Apparently, the importance of fatty acids and other polar compounds in dispersions can be put on a sound theoretical basis.
Determination of Sulfur in Rubber by the Perchloric Acid Method
Authors: Wolesensky Edward
Published: February 2011

In a search for a rapid and accurate method for determining sulfur in rubber it was found that oxidation of the sample by means of sodium peroxide in the Parr bomb is unsatisfactory when the sulfur content of the rubber is low because the samples that can be used for this purpose are too small for accurate results, or, if larger samples are used, the oxidation is incomplete. The use of a mixture of nitric and perchloric acids, as described by Kahane, is also unsatisfactory; but with certain modifications the method may be made to yield very good results, and if fusions are unnecessary, it will save time and labor. The chief modifications recommended are the use of a more dilute solution of nitric acid (equal volumes of the concentrated acid and water), allowing the rubber to dissolve completely on the steam bath before heating more strongly, then heating to gentle boiling until oxidation is complete, and finally destroying the residual nitric acid by means of hydrochloric acid. The use of a larger flask (500 to 800 cc.) is also recommended, and suggestions are also made for the adaptation of this method to the analysis of those rubber compounds which contain barium, lead, etc.
Inaccuracies in Determination of Acidity of Raw Rubber by Water Extraction
Authors: Cummings A. D. , Simmons H. E.
Published: February 2011

From the results obtained it is concluded that the boiling water hydrolyzes some of the esters in the acetone extract. In the case of direct extraction of the rubber with water, hydrolysis of esters must take place in the rubber, forming water-soluble acids; or else, although the esters are practically insoluble in the water, it extracts a little ester each time the extraction thimble empties (Bailey-Walker apparatus), carrying the ester down to be hydrolyzed in the boiling water below. Temperature and time of heating play a prominent part. The temperature must be close to the boiling point and the acidity increases progressively with time of heating. The fact that temperature is so important in producing this effect accounts for the erratic values obtained by direct water extraction. On the electric hot plates used water did not always boil steadily, and that contained in the thimble might vary considerably in temperature, much of the time not being hot enough to hydrolyze or extract any ester. Therefore, to avoid any difficulty in the determination of water-soluble acids in rubber, extract first with acetone, then digest this extract with water on a boiling water bath until no increase in acidity of the water extract is obtained. This is a part of the procedure developed at the Netherlands Government Institute by Van Rossem and Dekker.
Effect of Repeated Reclaiming of Rubber
Authors: Miller George W.
Published: February 2011

1—Reclaimed rubber, without the addition of new rubber in a subsequent vulcanization, cannot be repeatedly cured and reclaimed without a considerable deterioration in its physical properties. 2—The rubber scrap for reclaiming should be intelligently blended, and an endeavor made to keep the concentration of once-reclaimed rubber as low as is economically possible. 3—The chloroform extract and sulfur analyses of the uncured reclaimed rubber yield valuable information in regard to the quality of the product.
Principles of Patent Law Involved in the Weiss Patent Litigation
Authors: Deller Anthony William
Published: February 2011

OWING to the widespread interest in the chemical industry generally, and especially in the rubber industry, in diphenylguanidine as an accelerator in the vulcanization of rubber, it is believed that a discussion of the recent decision of the Supreme Court of the United States in the matter of the Weiss diphenylguanidine patent will serve a dual function of informing chemists about the status and the history of the Weiss patent and, at the same time, of expounding some of the principles of patent law involved in the case.
Color Reactions of Rubber and Gutta-Percha
Authors: Kirchhof F.
Published: February 2011

THE present paper was suggested by a recent publication of Pauly on the same subject, who applied the well known sterol reactions of Hesse, Liebermann, Tschugajeff, etc., to the hydrocarbons of rubber and gutta-percha. These reactions depend either upon the action of concentrated H2SO4 on chloroform solutions of the substances in the presence or absence of acetic anhydride (Liebermann, Burchard and Hesse reactions) or other solvents, or condensation reagents are used, such as acetyl chloride and zinc chloride by Tschugajeff, and acetic acid with arsenic trichloride by Kahlenberg, and trichloroacetic acid with a trace of formaldehyde by Godoletz. All the known sterol reactions take place also with rubber or gutta-percha, with the appearance of intense red or violet colorations of varying stability, the color depending in part upon the quality and in part upon the purity of the samples. The Burchard reaction in particular is very sensitive in these respects. Thus with rubber purified with alkali by the Pummerer method, the color is a Bordeaux red which does not change for a long time, whereas solutions of unpurified rubber change rapidly, a change which is rightly ascribed by Pauly to relatively rapid oxidation in the presence of oxidation products in the case of the unpurified rubber.
Some New Laboratory Work on Rubber
Authors: Somerville A. A. , Ball J. M.
Published: February 2011

CRUDE rubber is not of much use commercially or industrially until after it has been put through a chemical process discovered by Charles Goodyear: that of adding sulphur and heating. But sulphur is not the only material that can be used to change and improve the natural physical properties of raw rubber. There are other things than sulphur that are beneficial, one of which is Selenium. It is a pleasure to be permitted to talk here in Boston before a meeting of the Northeastern Section of the American Chemical Society and the Boston Rubber Group, devoted at this time particularly to the subject of rubber. It is a privilege to be permitted to talk on the subject of Selenium at this meeting because it is coming back very close to the home of Selenium so far as it is associated with the rubber industry.
The Mechanism of the Reinforcement of Rubber by Pigments
Authors: Depew Harlan A.
Published: February 2011

Dispersed pigment reinforces by increasing the tear resistance. Flocculated pigment hardens rubber and reinforces by increasing the resistance to cutting. It may also increase the tear resistance, but not to as great an extent as if the pigment were well wet. The mechanism of the reinforcement by increasing tear resistance is that the pigment particles act as obstacles that cause the tear to proceed in a longer path going around the particles. Due to the round-about path, the component of the force in the direction of the tear may be small. Accordingly, it is possible in the case of a fine pigment to increase the tear resistance even though the rubber-pigment bond is much weaker than the rubber itself. The hardness of a stock containing flocculated pigment is due to the rigidity of the structure assumed by the flocculated pigment. During the early moments of hot vulcanisation, rubber is semifluid and the degree of dispersion may be largely determined during this period; some of the pigments becoming dispersed and some becoming flocculated. Flocculated pigment and large particles introduce uneven stresses during the straining of rubber that lower the reinforcement below what might be expected.
The Evaluation of Carbon Blacks
Authors: Cranor D. F. , Braendle H. A.
Published: February 2011

In conclusion, it is shown that the “Delta A function” provides an instrument for the classification of carbon blacks as regards their usefulness to the rubber compounder. It is an index of widely inclusive character and not only indicates performance at optimum concentration, but also the range of effectiveness. The writers have undertaken exposition of the special applications of this to the classification of carbon pigments, pointing out the precautions necessary for its accurate use. We believe it important to supplement the “Delta A function” with other stress-strain data, also with laboratory performance tests, and finally with service records, when it is necessary to differentiate between carbons of the same general category. On the other hand, we believe no study of carbons or other pigments is complete unless “Delta A” values are included. Acknowledgment is gratefully made for the valuable suggestions of W. B. Wiegand and also the cooperation of Binney & Smith Co., who supplied all of the carbon blacks investigated and gave permission to publish the data covered by this paper.
Technical Application of Antioxidants
Authors: Bridgwater E. R.
Published: February 2011

IT is unfortunate that the process of vulcanization, to which the commercial use of rubber is almost wholly due, makes it much more susceptible to oxidation. The deterioration that sets in as soon as rubber is vulcanized was first attributed to oxidation by Miller in 1865 but it is only during the last 20 years that a serious effort has been made to find means of preventing it. During this period it has been found that many chemicals retard the oxidation of rubber when incorporated with it prior to vulcanization. Phenolic compounds, primary and secondary amines, aminophenols and condensation products of aldehydes with amines are the chemical groups within which the most valuable antioxidants are found. Many amines and aldehydeamine condensation products are also vulcanization accelerators and some of the earliest known accelerators have a mild antioxidant effect. Para-phenylenediamine and para-aminodimethylaniline were used as accelerators long before the term antioxidant was coined and their favorable effect on the aging properties of rubber compounds has been a matter of common knowledge for more than ten years. Recent investigations have disclosed numerous compounds in these classes that have little or no accelerating effect and are far more effective in retarding oxidation than any of the known accelerators.
Goodyear Experience in Temperature Control of Mill Rolls
Authors: Moorhouse R. W.
Published: February 2011

IT is well known that in milling a batch of rubber or compounded stock, the temperature of the mill rolls rises—rapidly at first, then more slowly—to a given temperature at the end of the run. There are, however, a number of factors which affect in varying degree not only the temperature eventually reached, but the intermediate temperature of the roll surfaces. Of these we may form two groups, those tending to increase and those tending to decrease the temperature. Factors Affecting Roll Temperature Initially high temperature of batch, toughness of the rubber or stock, heavy loading, large bank and gage and increasing ratios of roll speeds, tend to increase the temperature. Merely starting the average cold rubber through the mill increases the roll temperature 15° F. in the first five minutes, while using hot stocks increases this to 20° F. in two minutes. Toughness of stock affects roll temperature by varying the amount of heat produced in the first few minutes of milling, the rise of temperature increasing with the tougher stock. Doubling the gage of the mill increases the roll temperature 10° F., due to increased working of the batch. The same effect is obtained by increasing the size of the batch, up to the point of producing an idle bank. As small a change of ratio as from 1.11 to 1.17 will produce a rise of 10–12° F. in roll temperature. Cooling may be obtained, but only momentarily, by the addition of cold compound or a little water to the stock on the mill.
Contribution to the Thermochemistry of Rubber
Authors: Boström Siegfried
Published: February 2011

1. An apparatus is described suitable for the calorimetry of slow reactions. 2. By determining the heat of adhesion between fillers and rubber when mixed together, a method is found for the relative evaluation of technical rubber fillers. The utility of the method is shown by the comparison of the thermal data obtained using several types of black with physical data already published. 3. The elongation and contraction of raw rubber were studied from a thermodynamic standpoint, and also the change in total energy, the work of elongation, and its temperature coefficients. 4. The heat tone of the reaction between sulfur chloride and rubber dissolved in benzine was determined at a concentration of 0 to 1.3 g. of sulfur chloride to one gram of rubber. Heat tones depending on chemical and colloid-chemical processes may be exhaustively studied in this way.
Making Rubber Goods of Latex by Electro-Deposition
Authors: Klein Paul
Published: February 2011

Present manufacturing methods are characterized by repeatedly plastifying the rubber, partly by mastication and partly by heating. These operations involve the use of heavy machinery, and furthermore in certain cases the rubber mixes are then dissolved in organic solvents, a procedure which has the additional drawback of a more or less considerable loss of organic solvents. The question at once arises: why should these many difficult and expensive steps be necessary in order to prepare a shaped body containing all the compounding and other ingredients from the original latex? There is only one answer to this question, and that is, the actual rubber manufacturer does not start with the liquid sap. Obviously it should be much easier to handle a liquid, to add to it the desired dispersed ingredients, and then to use it in some way or another to obtain the shaped article instead of performing all the masticating operations which are carried out with so much power and such heavy and expensive machinery. But not only is this an economic question. There is more involved. The mastication of the rubber impairs its quality, and the longer the mastication of a certain mix, the poorer the physical properties of the product obtained therefrom will be.
Rubber Structure Research and Its Bearing on the Elastic Properties of Colloids in General
Authors: Hauser E. A.
Published: February 2011

The least, therefore, to which in my opinion the colloid chemist or colloid physicist may lay claim is credit, not only for a fair contribution to the structure of rubber, but for more than that—for having laid the foundation of an entirely new conception of fibrous and elastic matter in general; this with the aid of a method, x-ray analysis, which has been so severely criticized in its connection with colloidal research. I have purposely said “foundation,” because considerably more work will have to be done, and a final conception will not be generally accepted until we have learned to correlate this finding with results still to be obtained in a study of double-refraction phenomena and possibly when we have learned more in regard to the interpretation of results obtained when using light of intermediate wave lengths. There is, however, nothing which should discourage us and our slogan for the purpose of increasing progress should be at all times—keep going—and how?
A New Physical Test for Vulcanized Rubber
Authors: Wright D. D.
Published: February 2011

This test, by use of a sample of new design, subjects rubber to a combination of tensile and shearing stresses. Shear, however, is the predominating stress. Certain aged inner tubes have been found which deteriorated more when examined by this test than a comparison of their tensile-stress-strain curves with those of fresh tubes would indicate. Tearing action seems to be approximated by this test. The effect of overcure in some cases has been recorded at earlier stages by this test than by the tensile criterion. The test is easy to perform and with usual precautions should have an accuracy of approximately 10 per cent. VULCANIZED rubber is frequently required to withstand, not only the simple stresses such as those of compression, tensile, and shear, but also the combined effects such as torsion, tearing, bending, etc. It has been observed that, as some vulcanized rubber samples age, their resistance to shearing and tearing stresses decreases much faster than their resistance to tensile stresses, as determined under the standard procedure of rubber-testing.
Diffusion of Water through Rubber
Authors: Schumacher Earle E. , Ferguson Lawrence
Published: February 2011

The diffusion of water through thirteen rubbers of different compositions has been measured. The data obtained by two different methods are in satisfactory agreement. The mathematical derivation of a simple formula for calculating the rate of diffusion has been given. The diffusion measurements have shown: (a) that the rate of diffusion of water through a rubber membrane is inversely proportional to the square of the thickness; (b) that the rate of diffusion decreases greatly with increase in hardness; (c) that the effect of saturating the rubber with water is to increase the rate of diffusion through it, due probably not only to an increase in the water vapor pressure within the rubber, but also to a decrease in hardness; (d) that there is no intimate relationship between rate of diffusion and minor variations in the composition of the rubber.
The Oxidation of Vulcanized Rubber
Authors: Van Rossem A. , Dekker P.
Published: February 2011

SINCE Kirchhof in June, 1927, gave to the first general meeting of the German Rubber Society in Essen a detailed review of work concerned with the oxidation of rubber, it seems superfluous to publish any extensive bibliography thereon. We prefer to limit ourselves, for the present, almost exclusively to a few experiments in this field. However, we may refer in a general way to the work of others. It is a notable fact that all investigations of the oxidation of vulcanized rubber have been always based on the kinetics of the oxygen combination, and, as far as isolation of the oxidation products is concerned, on a late stage of oxidation, the isolation of oxidation products during the early stages of oxidation being left out of consideration. Thus, for example, Kirchhof in his work published in 1913 studied the behavior of ground vulcanized rubber which had been heated for 100 hours in a current of air at 100° C. and thereby strongly oxidized, as indicated by the increase in weight (11–13%). Eaton and Day later in 1919 made experiments of a similar nature. Here, too, the kinetics principally were studied, and the samples were examined only after oxidation was far advanced. Again in Kirchhof's recent work already mentioned, the oxidation products were studied only after prolonged oxidation.
Observations on the Chemical Constitution and Physical Properties of Rubber
Authors: Hock Lothar , Fromandi Guido
Published: February 2011

Some time ago we published the finding that the decrease in the iodine number of rubber on cyclisizing it electrically was accompanied by a marked loss of valuable colloid-chemical properties, and, moreover, that isoprene rubber originally characterized by a low iodine number improved in properties under the influence of the silent electric discharge, while the iodine number increased. These facts suggested that commercially less valuable grades of rubber might owe their inferiority to their essentially lower degree of unsaturation. Therefore the investigation was begun by comparing the known iodine numbers of the best grades of plantation rubber with those of the poorer grades. Pure rubber, as, for example, that prepared by Pummerer's method, is known to have an iodine number very near the theoretical (372.8). In the case of raw rubber each per cent of the rubber hydrocarbon present requires 3.728 units of the iodine number, so that naturally a lower value is to be expected as approximately four units must be subtracted for each per cent of impurity. If we suppose smoked sheets to contain 93% of rubber hydrocarbon, we can ascribe to it an iodine number of only about 347, provided that the impurities do not combine with any iodine, which, however, though not important, is not so. A sample of smoked sheet containing 3.2% of acetone-soluble material and 0.4% of mineral matter besides protein, etc., was found to have an iodine number of 348. Washed Congo rubber containing 5.9% of acetone-soluble material and 1.7% of mineral matter had an iodine number of 329. The iodine number of the acetone-soluble portion was 24, so that 5.9% of extract required approximately 1.4 units of the iodine number; hence the rubber hydrocarbon present had an iodine number of 327.6. If the components of the rubber insoluble in benzene were filtered off and the rubber precipitated twice with acetone and once with alcohol and then dried in a vacuum at 50° C. to constant weight, the iodine number rose to 351.4, thus closely approaching the theoretical value, considering the impurities still present. It is questionable whether or not one may attribute the less valuable properties of this wild rubber to its very slightly lower degree of unsaturation. For the present we shall restrict ourselves to the publication of our results in the following table, with the intention of returning to this question after a detailed examination of a greater amount of material.
The Purification and Fractionation of Rubber. (7th Communication)
Authors: Pummerer Rudolf , Andriessen Albrecht , Gündel Wolfgang
Published: February 2011

I—The Alkali Purification of Concentrated Latex. Nitrogenous Impurities in Latex Preserved with Ammonia It has already been shown that in the purification of latex by alkali, fresh and ammonia-preserved latex behave differently toward alkali. The former is changed even in the cold through decomposition of the proteins (as shown independently by de Vries and Beumée-Nieuwland), whereas the latter first shows evidences of changes at 50°, at which point it creams. Furthermore, experiments with “Revertex”, a concentrated latex, have shown that ammonia-preserved latex is changed in a still different way. Pummerer and Pahl consider the “total rubber”, obtained by them from ammonia-preserved latex by the action of alkali, to be free proteins and nitrogen. This view is, however, open to correction. Total rubber is probably fairly free of proteins, but contains nitrogen. The nitrogen content, which is still appreciable even after prolonged treatment with alkali at 50??, varies from 0.15 to 0.4%. This nitrogen was at first overlooked, because it was not detected in a few qualitative Lassaigne tests, nor in a quantitative Dumas determination. Moreover analysis indicated nearly 100% of hydrocarbon. Nevertheless new tests have shown that many samples contained 0.4% nitrogen. When the samples were incinerated with a reduced copper spiral, there was a deficit of 0.4% in the carbon-hydrogen determinations. Accordingly a substance containing 0.4% protein-nitrogen would show a deficit of about 1% on account of the oxygen in the protein. The nitrogen remaining after the alkali purification of ammonia-preserved latex is not protein-nitrogen but amino-nitrogen, which probably is formed by the action of ammonia during long storage. A gel-rubber (0.4% nitrogen) refluxed in benzene for a day with dilute NaOH yielded no amino acids to the NaOH. The neutralized aqueous solution did not give the ninhydrin reaction, nor did the rubber itself when it was boiled with the reagent.
The Preparation and Molecular Size of Isorubber Nitrone. (8th Communication)
Authors: Pummerer Rudolf , Gündel Wolfgang
Published: February 2011

Continuing earlier experiments of Angeli, Alessandri, and Pegna, of Alessandri and of Bruni, the latter and Geiger have recently studied the action of aromatic nitroso compounds on rubber, and have obtained notable results. The earlier experimentors succeeded only in obtaining from nitrosobenzene a compound of the composition C58H61N5O9. It has recently been proved that one molecule of the nitroso compound for each isoprene nucleus enters the rubber molecule. However, as the earlier investigators have shown, three molecules of nitroso compound react with each C5H8 group when the rubber is warmed in benzene on a water bath for 15 minutes. The solution changes from green to dirty green and finally to brown-red. After cooling it is poured into petroleum-ether, whereupon yellow flakes of the composition [C11H11ON]x, decomposing at 135–140°, separate, the yield being 94–98%. This product is evidently formed by the reaction of one molecule of nitrosobenzene with C5H8 with loss of 2 atoms of hydrogen. This hydrogen reduces a second molecule of nitrosobenzene to phenylhydroxylamine, which with a third molecule yields azoxybenzene. The latter was isolated from the mother liquor. The rubber derivative which is formed may be regarded as a nitrone of an isorubber:
Pigment Reinforcement
Authors: Lunn R. W.
Published: February 2011

This paper considers the reinforcement of rubber by various agents, but the point of view is taken from a rather new position. As a result the familiar conclusions are reached, but the new aspect has some points of interest. The first thing is to define the meaning of the term “reinforcement”, and for the purpose of this paper it is used to indicate energy. The extension of rubber and its compounds involves the input of energy, which increases continuously to a maximum at which breakdown occurs. This paper is a consideration of the energy relationships between rubber and pigment under extension. A familiar way of comparing the reinforcing powers of rubber pigments is to compare the total energies of resilience of the compounds containing the pigments. Pigments are compared on a basis of equal volumes. The resilient energy figures compared are those of the whole compound. For the purpose of this investigation an attempt is made to analyze the total energy value and assign a certain proportion of it to the rubber and the remainder to the pigment. However, it must not be understood that the pigment as such has an energy value like rubber. The addition of pigment causes an energy change in the rubber compound which can be associated with that pigment. To make the idea clearer it may be useful to express it in an elementary mathematical form.
Some Observations on Rubbers with Low Nitrogen Content
Authors: Cummings A. D. , Sebrell L. B.
Published: February 2011

Rubber has been prepared protein-free, although not entirely nitrogen-free, by digesting latex with caustic soda, as recommended by Pummerer and Pahl. Rubbers with a nitrogen content of from 0.004–0.0096 per cent have been prepared by a slight modification of the original procedure. This rubber can be compounded and cured to give good quality vulcanizates, which compare very favorably with the controls. Protein-free rubber, when acetone-extracted, becomes nitrogen-free. This can still be vulcanized, although it cures slowly. The rate of cure of rubber from protein-free latex is affected very little by the pH of the coagulating medium whereas with full-nitrogen rubber rate of cure varies considerably with change in pH value at the time of coagulation. It was also found that protein-free rubber could be racked. Data on the preparation, coagulation and nitrogen content as well as the vulcanization results of protein-free rubber are presented. The observations lead to the conclusion that protein is not the key to the explanation of the physical properties of rubber. Rubber cannot be prepared absolutely nitrogen-free by the method of Pummerer and Pahl, even though the treatment of the latex with caustic is continued twice as long as they recommend. The residual 0.004 to 0.009 per cent of nitrogen is not protein nitrogen, since it is removable by acetone extraction and the amount of nitrogen falls so low as to be unmeasurable with accuracy by the exact method used in this research—i. e., colorimetric determination with Nessler???s solution. The authors note with satisfaction that Pummerer has come to exactly the same conclusion. Comparison of the results of vulcanizing protein-free rubber with those of the controls and with the results of the previous research shows that the rate of cure is constant under different conditions of coagulation and that the quality of the nitrogen-poor vulcanizates compares very well with the controls and with the earlier mentioned work described by Dinsmore. It appears, therefore, that the variation in cure and quality as noted by Dinsmore was due entirely to some particular condition of the rubber protein brought about by the varying pH values existing at the time of coagulation. Protein-free rubber, after acetone extraction, is practically nitrogen-free and cures slowly to give vulcanizates of lower quality than is obtained with the protein-free rubber. It should be remembered, however, that, as stated above, this effect may not be due entirely to the absence of nitrogen. Definite conclusions on this phase of the question must be withheld until more experiments are made. The evidence presented shows that protein-free rubber can be compounded and cured to give good quality products. Hence the protein is not an essential factor in producing the physical properties of vulcanized rubber. The condition of the protein does affect the rate of cure and so exerts an indirect effect upon the quality of the rubber.