bluuebunny/crossref_metadata_2025 huggingface dataset:
The Vulcanization of Rubber with m-Dinitrobenzene
Authors: Wright J. M.
Published: February 2011

The literature referring to the vulcanization of rubber with m-dinitrobenzene indicates the present undeveloped state of knowledge of the reaction and of the most favorable conditions for its employment. Much is vague and even contradictory. Ostromislensky (J. Russ. Phys.-Chem. Soc., 47, 1462 (1915)) stated that certain nitro compounds are capable of vulcanizing rubber in the absence of auxiliary substances, and that the products of vulcanization are superior in some respects to sulfur vulcanizates; tensile strengths obtained were comparable with those of sulfur vulcanizates; aging properties were found to be good; color and finish were better than those of sulfur vulcanizates. On the other hand, Porritt (J. Soc. Chem. Ind., 35, 986 (1916)), and Stevens (J. Soc. Chem. Ind., 36, 107 (1917)) failed to confirm these statements, but agreed that the presence of litharge is beneficial. Again in 1929, Ostromislensky (India Rubber World, 80, 55 (1929)) confirmed his original report, stating that he believed that this form of vulcanization is due to an action between rubber and the oxygen of the nitro compound. Blake (Ind. Eng. Chem., 22, 7 (1930)) stated that vulcanization of rubber with dinitrobenzene involves a monomolecular chemical reaction between rubber and dinitrobenzene, in which, of the 6 per cent dinitrobenzene, practically all of the nitrogen combined with the rubber. The end-product of the reaction appears to be a soft vulcanized rubber; no one has claimed to be able to produce an ebonite by the use of this reagent.
The Properties of Rubber Cements
Authors: Ford T. Foster
Published: February 2011

Rubber cements used in factories manufacturing rubber goods consist of rubber-solvent dispersed systems. They usually contain, in addition to rubber, various pigments, softeners, curing agents, etc. The smoothness and thickness of the films deposited, the readiness with which the films break over small apertures in dipped objects, the viscosity, and the stability of the cements as liquid systems are characteristics which affect their utility. The purpose of this paper is to present a summary of empirical data relating such working properties and important variables in composition. Whereas there is in the literature much data on the properties of extremely dilute rubber solutions, obtained in the course of theoretical researches, little information is available concerning the much more concentrated cements used commercially. Of the classical properties of liquids only viscosity will be discussed in this paper.
pH Properties of Colloidal Carbon
Authors: Wiegand William B.
Published: February 2011

IF ONE part of colloidal carbon pigment is boiled for 15 minutes or more with three to ten parts of distilled water and cooled, the supernatant liquid decanted, and the sludge placed in contact with the glass electrode of a pH electrometer, a reading is obtained which is characteristic of the material. A representative list of the pH values thus obtained is shown in Table I. In this preliminary account some of the factors will be given which influence pH values of particulate carbon, some of the relations between pH and other properties of colloidal carbon, and something of the significance of these pH properties.
Some Applications of the Microscope to Rubber Technique
Authors: Tidmus J. S. , Parkinson D.
Published: February 2011

This paper is not intended to be a review of work done in the rubber industry with the aid of the microscope, but rather a record of some investigations by the authors in this field. The examination of rubber products usually consists of a chemical examination of the ingredients used, and physical and actual service tests of the finished products. In the course of manufacture one often meets with phenomena which cannot be explained by the results of these examinations. In many of these instances an explanation can be found with the aid of a microscope. Microscopical methods do not seem to hold the place in rubber testing which they merit. This is due partly to the technique required in preparing specimens, and also to the experience required for the proper interpretation of the facts observed. One must, however, recall the valuable work of Depew and Ruby (Ind. Eng. Chem., 12, 1156 (1920)), Green (Ind. Eng. Chem., 13, 1130 (1921)), Greenquist (Ind. Eng. Chem., 20, 1071 (1928); 21, 665 (1929)), Steele (Ind..Eng. Chem., Anal. Ed., 2, 421 (1930)), and Arnes (J. Roy. Microscop. Soc., 1923, 265).
The Goodrich Flexometer
Authors: Lessig E. T.
Published: February 2011

The Goodrich flexometer is of simple design and is easily operated at ordinary or elevated temperatures. Test pieces procured from laboratory specimens or from finished rubber or rubber-fabric products may be tested, using moderate loads that produce equilibrium temperatures during flexure or larger loads that rupture the test piece. This machine may be used to study the effects on heat generation of the time of cure, the magnitude of the applied load, changes in pigmentation, and variations caused by anisotropy in rubber compounds. It is so designed that the structural changes such as softening or stiffening may be followed during the period of flexure.
Enhanced Polymerization and Depolymerization of Natural Rubber by Quinones and Related Compounds
Authors: Spence D. , Ferry John D.
Published: February 2011

1. The enhanced polymerization or the depolymerization of natural rubber may be effected thermally or photochemically by one and the same reagent. 2. The action of quinones, carbonyl compounds, and other quinonoid compounds in this connection has been studied. 3. Depolymerization is favored by (a) dilution of the rubber by a solvent or swelling agent, (b) increase of temperature, (c) presence of molecular oxygen. 4. The results are interpreted in terms of concurrent reactions.
Rubber. XVIII. Various Ozonides of Rubber and the Problem of the Existence of the Primary Ozonides of Harries
Authors: Pummerer Rudolf , Richtzenhain Hermann
Published: February 2011

A permanently valuable service was rendered by Harries when he introduced the ozone cleavage of unsaturated compounds as a general method of investigation in organic chemistry. By analogy with other addition reactions of double bonded carbon atoms he derived the formula (a) for the ozonides which are first formed, but to support the existence of which he was able to obtain only scant experimental data. Harries relied above all on two observations, first, that mesityl oxide ozonide reverts to mesityl oxide when heated by itself, and, secondly, that fumaric acid is supposed to combine loosely with ozone and then readily split off again. Both of these suppositions have remained undisputed up to the present time. Harries reported that it was not possible, with any of a wide variety of reducing agents, to reduce the ozonides to the original compounds or to 1,2-glycols, as would be expected from their structure. Staudinger has laid great stress on this fundamental objection, and he considers that most ozonides have an isoözinide formula, as shown by formula (b) above, in which the carbon chain is already ruptured, so that by reduction only the usual types of cleavage products rather than glycols with intact carbon chains can be formed, as has been found experimentally. Staudinger assumed that the primary reaction products of treatment with ozone are molozonides containing the group:
The Coagulation of Latices by Polar-Nonpolar Liquids
Authors: Daniel F. K. , Freundlich H. , Söllner K.
Published: February 2011

(1) Diluted latices—Abiarana gutta-percha latex was specially investigated—may be coagulated by shaking them with organic liquids, not miscible with water in all proportions, provided that the liquids form a second liquid phase and that their molecules have a polar-nonpolar structure (butyl alcohol, isobutyric acid, cyclohexanol, etc.). Nonpolar liquids (petroleum ether, chloroform, etc.) do not coagulate diluted latices on shaking under these conditions. (2) This coagulating action can be explained by assuming that the latex particles are strongly accumulated at the interfaces of polar-nonpolar liquids and water; this is not the case with nonpolar liquids. (3) Small concentrations of some polar-nonpolar substances of small molecular weight, soluble in water, can also coagulate Abiarana gutta-percha latex if they form unstable foams; this was observed with propanol and isopropanol. If the foam formed under these conditions is stable, as with small concentrations of dissolved butanol and isobutanol, no coagulation takes place. This behavior can be explained as in (2), the air bubbles behaving like the second liquid phase. (4) Jelutong latex is known to contain an excess of resins, compared with the amount of rubber. A method of coagulating this latex quickly and separating the resins from the rubber consists in shaking the latex for some seconds with certain polar-nonpolar liquids, forming a second liquid phase, such as isobutyl or isoamyl alcohol. A lump of rubber is accumulated at the interface of the two liquids; the resins are contained in the organic phase.
The Mechanism of the Action of Vulcanization Accelerators. Derivatives of Mercaptobenzothiazole. II. The Transformation of Mercaptobenzothiazyl Sulfide
Authors: Zeĭde O. A. , Petrov K. D.
Published: February 2011

1. During the vulcanization of rubber, mercaptobenzothiazyl sulfide is transformed into mercaptobenzothiazole and the zinc salt of the latter. 2. This transformation is effected by the interaction of mercaptobenzothiazyl sulfide with sulfur. As a result of this reaction unstable products of addition of sulfur and mercaptobenzothiazyl sulfide are formed, and when heated these are converted into benzothiazyl disulfide. 3. During vulcanization, benzothiazyl disulfide decomposes into mercaptobenzothiazole and the zinc salt of the latter. 4. The acceleration of vulcanization of rubber by mercaptobenzothiazyl sulfide, as well as by other derivatives of mercaptobenzothiazole in which the mercapto —SH group is substituted, is attributable to several causes, the chief of which is the formation of mercaptobenzothiazole and its zinc salt.
Research Coöoperation in the Rubber Industry
Authors: Geer William C.
Published: February 2011

One of the outstanding observations which one may make of the rubber industry of today is the high degree of technical competition. Research laboratories are large and their members are well trained and resourceful. The achievements of these groups of competing technologists find their way to the public as patented articles or methods and scientific articles in the literature. In the majority of cases the new products or methods are promptly studied by competing laboratories and ways are found to accomplish the same end by means which do not infringe a given patent. Therefore, much of the energy of research is expended merely in the effort to keep pace with competitors. Because of this price competition and the narrow margin of total profits, there is a constant pressure upon technical groups to apply their energies to the solution of immediate needs. The physical proximity of the laboratories to the factories and the force of competition usually lead these men to appraise new ideas in the light of practicability. Can the trick be turned within one or two years? If not, efforts should be expended in apparently more fruitful fields.
A Manometer for Measuring the Oxidizability of Rubber
Authors: Dufraisse Charles
Published: February 2011

In view of the practical interest in a method for measuring directly the rate of oxidation, i. e., the oxidizability of rubber, it has seemed worth while to devise an apparatus with which the technic of making such measurements is so simple that it is within the compass of operators with no particular training. With this in mind the author has been led to construct a new manometer for measuring oxidizability. Before describing the apparatus and its method of operation, however, it is necessary to explain its principles. Later on, it is intended to deal in a more thorough way with the significance of the measurements, with the various causes of errors arising from the nature of the substance studied and the technic employed, and finally with different ways of expressing the results obtained.
The Influence of Vulcanization on Oxidizability in Relation to Aging. A Preliminary Study
Authors: Dufraisse Charles , Étienne André
Published: February 2011

Because of its preliminary character, the present investigation does not admit any definite conclusions. Rather, by bringing out clearly the various complications which arise in studying the oxidizability of rubber, especially when the aim is to establish a parallelism between oxidizability and the ill-defined phenomenon of aging, the investigation has shown the many difficulties in general involved in the problem. These complications are to a certain extent attributable to the nature of the phenomenon itself which has been measured, i. e., the oxidizability; but for the most part they owe their origin to the nature of the substance studied, and especially to its heterogeneous character. For these reasons the uncertainty in the results is increased by vulcanization, and the more vigorous the treatment, the greater is this uncertainty. As a result, considerable fluctuation in the measurements occurred. This is the reason why, in the past as well as now, so much emphasis has has been laid on the advisability of considering as significant only relatively large differences in measurements when drawing conclusions from them. With these reservations in mind, the facts which emerge from this opening work may be reviewed briefly. First of all, it may be stated that, as a principle, the higher the percentage of combined sulfur, the greater is the oxidizability of rubber. In other words, it is, in a different guise, the principle accepted by the majority of technologists, and which Martin expressed in a particularly clear fashion, viz., that the lower its state of vulcanization, the more stable is rubber.
The Activating Influence of Metallic Oxides on Vulcanization in the Presence of Organic Accelerators
Authors: Cotton F. H. , Westhead J.
Published: February 2011

1. The activating influence of the oxides of six metals, zinc, cadmium, mercury, magnesium, calcium, and barium in Group 2 of the periodic table, has been investigated with raw and acetone-extracted rubber mixes containing accelerators representative of seven chemical classes. 2. Oxides of barium, calcium, and magnesium exert insignificant activating influence on vulcanization in the presence of all accelerators tested. 3. Cadmium oxide is superior to zinc oxide in activating effect when employed in normal rubber mixes accelerated with zinc isopropylxanthate, tetraethylthiuram disulfide, mercaptobenzothiazole, and ethylideneaniline. 4. Cadmium oxide proved superior to zinc oxide in activating all accelerators tested (other than diphenylguanidine) in a mix made from acetone-extracted rubber. 5. In a mercaptobenzothiazole stock, mercuric oxide gave greater activation than either zinc oxide or cadmium oxide. This superiority was more marked when using acetone-extracted rubber. 6. The activating influence of molar or semimolar proportions of twenty-four metallic oxides on vulcanization in the presence of diphenylguanidine and mercaptobenzothiazole was investigated and reported in the form of graphs showing the rigidity developed after varying times of vulcanization, with mixes containing either raw rubber or acetone-extracted rubber or rubber with additional stearic acid. 7. With mixes containing diphenylguanidine, the activating influence of oxides on vulcanization was more marked the lower the fat acid content. Most oxides gave the highest modulus in a mix containing acetone-extracted rubber and diphenylguanidine. 8. In mixes containing mercaptobenzothiazole, most oxides exhibited an increasing activating influence as the fat acid content of the rubber increased, although in several instances stearic acid in excess of that naturally present in the raw rubber merely acted as a softener. 9. Although development of modulus was retarded by increase in the fat acid content of a diphenylguanidine mix, it was frequently observed that the tensile strength and elongation at break were higher in the presence of stearic acid, suggesting that this improved dispersion of the oxide. 10. Of the twenty-four oxides tested, zinc oxide, cadmium oxide, red lead, and arsenious oxide proved most effective in the presence of diphenylguanidine, arsenious oxide giving greater rigidity than zinc oxide. 11. Bismuth trioxide, cadmium oxide, mercuric oxide, litharge, red lead, and zinc oxide were found satisfactory as activators in mixes incorporating mercaptobenzothiazole; and all the former gave stiffer vulcanizates than obtained with zinc oxide. 12. Cadmium oxide and red lead proved effective with both diphenylguanidine and mercaptobenzothiazole. 13. Cupric oxide showed distinct activating properties, but an equimolecular proportion of cuprous oxide caused such rapid deterioration during and subsequent to vulcanization that it was not practicable to complete physical tests.
Investigation of the Thermal Conductivity of Rubber
Authors: Frumkin L. , Dubinker Yu
Published: February 2011

1. The apparatus for the determination of the coefficients of thermal conductivity which is described is satisfactory for the investigation of rubber mixtures. 2. A review of the results of the determinations of K values of various mixtures leads to the following conclusions: (a) The thermal conductivity of rubber mixtures containing synthetic rubber is greater than that of mixtures containing natural rubber. (b) The addition of zinc oxide even in considerable quantities to rubber mixtures containing a large percentage (55 per cent) of carbon black does not substantially increase thermal conductivity. (c) In the case of carcass mixtures a considerable increase in the coefficient of thermal conductivity is observed when the content of zinc oxide is increased from 7.5 to 15 per cent by weight; on further increase in the zinc oxide K increases but little. (d) The K value of carcass mixtures before vulcanization is smaller than that of the same mixtures after vulcanization by an average of 23 per cent. (e) The thermal conductivity of uncured tread mixtures is the same as that of vulcanized mixtures. (f) The coefficient of vulcanization has no effect on the K value of unloaded mixtures and mixtures containing fillers. (g) The K value of rubber mixtures increases sharply with addition up to 60 per cent by volume of fillers with good thermal conductivity (zinc oxide and graphite), but only slowly with the addition of fillers of medium thermal conductivity (carbon black). In other words, the curve of the relation between the coefficient of thermal conductivity and the percentage by volume of graphite and of zinc oxide is convex to the filler axis and is concave in the case of carbon black.
Comparative Viscometric Studies of Solutions of Crepe Rubber and of Buna
Authors: Philippoff W.
Published: February 2011

Measurements and their representation as flow curves of solutions of Buna-115 in tetrachloroethane give a means of obtaining an insight into the properties of Buna-115 in solution. By measurements of the viscosity as a function of temperature, it was proved that the temperature coefficient is similar in magnitude to that of natural rubber and that of polystyrene. A comparison of the flow curves of Buna, masticated rubber, pyroxylin, and Cellit leads to certain conclusions regarding the elasticity of colloids in solution and the role of the distribution curve. At low temperatures, i. e., below −40° C., both Buna and natural rubber show transformation points, which are manifest by increases in the otherwise very small temperature coefficients. The measurements reveal no property of natural rubber and of Buna which is peculiar to these two substances alone.
Water Resistance of Neoprene
Authors: Starkweather Howard W. , Walker Herbert W.
Published: February 2011

Superior water resistance of well-cured Neoprene, like that of natural rubber, depends upon the absence of water-soluble ingredients and agents that are capable of absorbing water. It has been shown that the water resistance of Neoprene varies greatly with different activating agents. This paper includes a more detailed study of the water absorption of Neoprene—magnesia—zinc oxide compounds and describes certain loaded stocks with improved water resistance. The water absorption was determined by the method already outlined, using slabs 0.20 cm. thick. Calculation of Water Absorption The water absorption can be calculated from the increase in weight or from the increase in volume of a stock during immersion in water. A difference between these values is an indication of chemically combined water. This is based upon the assumption that water undergoes no significant change in volume during absorption but that there is a change in volume during a chemical reaction. The two methods of calculating the absorption of water are shown by the equations:
A New Method for the Direct Determination of Rubber. A Preliminary Communication
Authors: Kheraskova E. , Korsunskaya E.
Published: February 2011

The conventional methods for the direct determination of rubber cannot be used for determining natural rubber in the presence of sodium-butadiene rubber. These methods are based either on precipitation of the rubber from solution or on the determination, by one method or another, of the double bonds in the rubber molecule. Since natural rubber and synthetic rubber differ in their solubilities but little, the method of precipitation obviously cannot be used for their separation. Nor are methods which involve determining the double bonds adequate to distinguish them, because both kinds of rubber are unsaturated compounds. It was therefore of interest to develop a method of analysis based on the determination of the methyl groups, which are present only in the natural rubber molecule. Kuhn and L'Orsa (Z. angew. Chem., 44, 847 (1931)) have shown that, in the oxidation of organic compounds, a methyl group connected with a carbon atom is partially oxidized to acetic acid. The object was to develop this reaction into a method of rubber analysis by establishing the optimum conditions for the quantitative oxidation to acetic acid of all the methyl groups in the rubber hydrocarbon.
The Marking of Uncured Rubber Mixes
Authors: Stern H. J.
Published: February 2011

One of the problems which confront almost every rubber manufacturer is to avoid confusion between the various qualities of mixings which he uses. Few indeed are the factories where the qualities are not so numerous and difficult to distinguish from their appearance as to provide a possible source of troublesome and costly errors. Rubbers which have received different mastication treatments and pure gum mixings are most difficult to recognize. In some cases, of course, the uncured mixings may be readily distinguished by their color. Even where this is not so, it is frequently possible to add, during the mixing process, a small quantity of coloring matter, which, though sufficient to prevent errors, is unnoticeable in the vulcanized result. This method is an excellent one, but its use is restricted to neutral tinted goods, which are not sold on color. Goods which are colored, or of a good white, and of course all black mixings, will require a different means of identification. After a mixing has been made, it may be necessary to store it for some time before it is used. A system of storage bins or shelves, divided into sections which are labelled and reserved for the various mixings, is helpful, but by no means foolproof. Unless the greatest care is taken, mixings will find their way into the wrong compartment, and the marking or labelling of each batch is therefore an essential safeguard.
The Preparation of Latex and Determination of Quality
Authors: Davey W. S. , Coker F. J.
Published: February 2011

Latex production has steadily increased during the last few years, as shown by the figures in Table I, which have been extracted from data published by the International Rubber Regulation Committee. Since 1934, output has nearly doubled, and for this year it is estimated, from the average figures for the first nine months of the year, that it will amount to approximately 35,000 tons. No statistics are published as to the respective amounts of preserved field latex and concentrated latex which comprise this 35,000 tons, but assuming the latex to contain an average of 50 per cent dry rubber, this quantity would represent approximately 16,000,000 gallons. Almost the whole of this latex is exported from Malaya and the Netherlands East Indies, only a negligible quantity being shipped from other rubber-growing countries. This production is confined to relatively few estates and in this respect affords a strong contrast to the production of estate rubber in the form of sheet or crepe, which is spread over many estates and small holdings (in Ceylon alone it is computed that rubber is produced on 100,000 estates and small holdings, mostly the latter). Latex production must of necessity be limited to the larger estates for both technical and commercial reasons, as the smallest consignments which are conveniently handled by European importers are around 500 gallons, and for some estates even the production of this quantity entails bulking several days' crop. On the other hand, some large estates export regularly 20,000 gallons or more every month, and the practice is growing of bulking supplies from individual small estates at central factories.
Some Properties of Rubber Latex
Authors: Schmidt Ernst , Stamberger Paul
Published: February 2011

Rubber latex of the commercial type preserved by ammonia was freed almost completely of its serum components by a method involving two steps: 1. Electrophoretic deposition of the rubber particles on a membrane, followed by 2. Dispersion of the resultant paste in a 0.6-per cent solution of ammonia in distilled water. This process was repeated until the aqueous phase obtained from this separation was free of non-rubber components in the latex.
The Gough-Joule Effect in Vulcanizates
Authors: Gleichentheil S. , Neumann W.
Published: February 2011

Since the phenomenon now known as the Joule effect was first measured, only a few investigators have concerned themselves with this phenomenon. Hock, one of these investigators, measured the heat which is evolved by raw rubber when stretched, and found that the quantity of heat evolved is proportional to the degree of elongation. When, therefore, the quantity of heat is plotted against the percentage elongation, a straight line is obtained. The present authors have measured the heat evolved when vulcanized rubber is stretched, the method being to stretch a strip of rubber in a calorimeter filled with mercury.
Oxidation Products of Rubber: Rubbone
Authors: Stevens H. P. , Popham F. J.
Published: February 2011

(1) The methods of making Rubbone are described and data given regarding the “dry” method in which rubber containing catalyst is milled with cellulosic materials and fillers. (2) The properties of Rubbone are described, including the polymerized products, the resistance of films to weak acids as for lacquering tins, and the electrical properties. (3) Rubbone can be vulcanized with sulfur. The products have applications as cements. (4) The method of preparation and properties of the hydrochloride and chlorinated Rubbone, and their use as a basis for alkali-resistant paints are described. These products have a tendency to gel, but this may be prevented by the incorporation of coumarone.
Difficulties in the Thorough Impregnation of Textiles with Latex
Authors: Bongrand J.-Ch
Published: February 2011

In a patent of 1920 by Hopkinson, there appears the claim that cotton thread need only be immersed in latex to bring about complete impregnation and even penetration of the latex into the canals of the fibers. This is a quite unwarranted claim, and it can be explained by the fact that Hopkinson was primarily a lawyer as far as patents are concerned, and there is a natural tendency in this profession to place a mortgage on future accomplishments. As a matter of fact, in spite of its very low viscosity (200 times less than that of benzene solutions containing the same percentage of rubber), latex does not penetrate spontaneously into textiles in the same way that clear solutions of rubber do. The work of Hauser and Hünemörder (cf. Rubber Chem. and Tech., 5, 685(1932)) has more or less settled this question. According to their technic, rubberized threads to be examined are immersed in gelatin, the preparation is frozen by carbon dioxide, and fine sections are cut by means of a microtome. The gelatin and also the cotton structure which has not been impregnated are then destroyed by concentrated sulfuric acid, and are eliminated by washing. The remaining rubber has a red-brown color. In this way Hauser and Hünemörder established definitely that whereas clear solutions containing, for example, five per cent of rubber, penetrate cotton threads, latex only coats them superficially and does not penetrate them.
Flocculation of Pigment in Carbon Black—Rubber Mixtures
Authors: Park C. R. , McClellan Paul P.
Published: February 2011

NUMEROUS references occur in the literature as to the cause of so-called scorching or burning in rubber-pigment mixes containing no vulcanizing agent. It was suggested (6) that this stiffening effect may be caused by flocculation of the pigment particles. Green (8) demonstrated a relation between the stiffness and flocculating tendency of pigments in paint mixtures, and Depew and Ruby (4) and Green (7) suggested that the phenomenon of flocculation may have some relation to the properties of cured rubber mixes which contain pigments, especially carbon black pigments. Grenquist (9) reported that carbon black exists in a more or less flocculated condition in vulcanized rubber, and some evidence was presented by Park and Morris (11) that mill-scorched batches which exhibit abnormal stiffness possess a structure which suggests that the black has been flocculated. The increase in stiffness of unvulcanized rubber—carbon black mixes upon standing for periods of several days was mentioned by Stamberger (13). Busse and Davies (2) presented data showing the effect of heat upon the stiffness of such mixes and mentioned the possible relation between flocculation and increase in stiffness. In order to throw more light upon the behavior of carbon black in the stiffening of rubber, a series of experiments was planned following the general methods of Busse and Davies, which include heating the sample for various periods of time and attempting to follow the changes in gross physical properties and in the minute structure of the mix.
Extraction of Water-Soluble Accelerators in Water Cure
Authors: MacKay J. W.
Published: February 2011

No measurable quantity of the water-soluble accelerators tested was extracted from the rubber during the water extraction. Therefore, these accelerators will not be extracted during vulcanization in water. The softening action observed in water-cured latex products is due to the extraction of water-soluble nonrubber components from the rubber film. The water-soluble accelerators tested have a selective solubility for rubber which is many times greater than their solubility in water.
Control Tests of Uniformity in the Manufacture of Carbon Black
Authors: Grote H. Walter
Published: February 2011

Twenty-five years ago, a pneumatic tire for an automobile cost twenty-five dollars and gave service of about 3500 miles. Today a pneumatic tire costs only one-half as much and can be relied upon to give service of about 25,000 miles. These improvements are the result of various factors, such as the use of cord fabric, organic accelerators, antioxidants, and other carefully chosen raw materials. Among these latter, it is safe to say that carbon black is unquestionably the raw material which has contributed most of all to the increased mileage of pneumatic tires. Years ago when the reënforcing properties imparted to rubber by carbon black first became recognized, this product was furnished without any particular requirements other than freedom from impurities. Later, as the percentage of carbon black incorporated in rubber mixtures continued to increase, certain measures were taken to control the grit content. Ultimately, with the aim of furnishing the rubber industry with a product of the highest quality and greatest uniformity, the most important producers of carbon black, in coöperation with the laboratories of rubber factories, proceeded to develop a series of check tests and various other tests, which have led in turn to the development of the present-day specifications of carbon black.
The Creaming of Hevea Latex by Colloids
Authors: Vester C. F.
Published: February 2011

Hevea latex is generally considered to be a suspension of rubber particles of various dimensions up to about 3 µ. The rubber hydrocarbon contains no “ionogenic groups,” and it is believed that part of the serum components imparts a negative charge to the rubber particles. Almost all latex imported into Europe is preserved by means of 0.5 to 0.7 per cent of ammonia. This ammonia plays a three-fold part: (1) it prevents premature souring of the latex; (2) it increases somewhat the charge on the particles; and (3) it attacks all types of serum components so that within a short time the “preserved” latex is hardly comparable with natural latex. As with all suspensions in which the dispersed phase is lighter than the dispersing medium, rubber latex exhibits the phenomena of creaming. The density of the rubber particles is approximately 0.914, that of the medium, 1.020. By means of creaming, it is possible to obtain a latex (1) which has a higher rubber content, whereby transportation space and cost are saved, and (2) which contains no components having a tendency to deposit a sediment. The natural creaming of latex, which is of no importance technically, was observed by Faraday as early as 1825.
The Behavior of Raw Rubber When Stretched Isothermally
Authors: Hintenberger H. , Neumann W.
Published: February 2011

The S-shaped form of the stress-strain curve of rubber is today explained in a quite satisfactory way. In the first part of the curve, i. e., the gradual ascent, work must be expended because of the van der Waals forces of attraction of the molecules; in the second part, i. e., the steep ascent, the elasticity is chiefly an entropy effect, which is finally exceeded by crystallization phenomena. The phenomenon of crystallization itself has been the subject of extensive investigations, but in most cases vulcanized rubber has been employed, and because of the various accelerators and fillers which the rubber has contained, the products have been rather ill-defined. It is evident that the phenomena involved in crystallization would be much more clearly defined if the substance under investigation were to be in a higher state of purity. If experiments are carried out with raw rubber, a flow effect is added to the various other phenomena. As a result of this flow effect, Rosbaud and Schmidt, and Hauser and Rosbaud as well, found that the stress-strain curve depends on the rate of elongation at very low extensions, with a greater stiffness at high rates of elongation. As found recently by Kirsch, there is no evidence of any flow phenomena in vulcanized rubber at room temperature. Most investigations have been so carried out that the stress has been measured at a definite elongation. It was therefore of interest to determine the elongation at constant stress, and the changes in this relation with time and with temperature, of various types of raw rubber.
The History of Rubber. Franz Carl Achard's “Experiments on Elastic Resin”
Authors: Eck Leo
Published: February 2011

It is a curious fact that it is in the history of rubber that extreme difficulty is encountered in altering current beliefs. This is attributable in part to the fact that the history of rubber is usually treated in a cursory way in the introduction to a work, and an investigation of the original sources is ordinarily omitted. It is also attributable to the general belief that everything has been settled in this field, and therefore that it is sufficient merely to refer to this or to that original work. The present writer has plenty of evidence at his disposal to support this contention. Although of great value in its day, the compilation of scientific publications on the entire history of rubber by A. Slingervoet Ramondt is today out of date in many respects. Unfortunately too, much that is of value in this work has been forgotten. Slingervoet Ramondt cites, for example, Gmelin's “Handbuch der Chemie” to the effect that Achard studied the action of nitric acid on rubber. As a matter of fact the original work of Achard is not mentioned, either in any notes in the text or in the chronological list of references to the literature. The present author has therefore deemed it a pleasant task to make better known the contributions of a German chemist to the earliest investigations of rubber, a chemist whose name is already held in high esteem for his work in another field, the production of beet sugar.
Chemistry of Soft Rubber Vulcanization. Reversion and Nonreversion in Low-Sulfur Compounds
Authors: Garvey B. S. , Forman D. B.
Published: February 2011

ACCUMULATION of evidence in recent years has led to a wide acceptance of the view that, chemically, vulcanization is the establishment of cross bonds between the fiber molecules of unvulcanized rubber. The usual concept is that of a chemical cross bond typified by the sulfur bridge (4). It was recently proposed (2) that “mechanical cross bonds” might be formed by the interlocking of the molecules as they become kinked as a result of cis-trans isomerization at some of the double bonds. It was also suggested that free rotation around single bonds might unkink the molecules. This straightening of the molecules would result in reversion of the vulcanized structure. This theory suggested that a study of reversion would be of value. For this purpose low-sulfur compounds are most suitable because the number of chemically stable sulfur bridges is small. Consideration of the experiments reported here suggests the interesting possibility that in vulcanized compounds there exists a sort of dynamic equilibrium between the formation of cross bonds and their destruction, which results in the maintenance of an adequate number of cross bonds although the individual cross bonds are not permanent. The general methods of mixing, curing, and testing were previously described (3). Since PBA and Altax gave the most clear-cut distinctions between reverting and nonreverting types of acceleration, the complete data are given for these two accelerators. Similar tests were made with the other accelerators, but only the conclusions from them are reported here.
The Rubber-like Behavior of an Artificial Substance (Oppanol) when Irradiated with X-rays
Authors: Brill R. , Halle F.
Published: February 2011

As is known, natural rubber has the property of giving, when stretched, an x-ray fiber diagram, whereas in a normal state the same rubber is amorphous. Numerous other natural substances such as hair and tendon, and artificial substances such as polychloroprene, behave in the same way. However, this effect is not confined to purely organic substances, and it is to be found, for example, in the case of so-called amorphous sulfur and polyphosphornitryl chloride (PNCl2)x. All these substances have the property in common with one another of exhibiting a rubber-like elasticity within a definite temperature range, and of being composed of long-chain molecules.
Determination of the Resistance of Vulcanized Rubber to Tearing
Authors: van Wijk D. J.
Published: February 2011

By the resistance to tearing of a material is meant the resistance shown by the material, while under tension, to tearing completely apart after a split has been made in the surface by any means whatsoever. Without question, the destruction of rubber articles can in many cases be traced to tearing. The initial tears can be regarded as the result of a splitting of the inelastic oxidized skin or of injury to the surface. Tears on the side walls of a tire, for example, can be attributed to the first cause; the wear on the tread is attributable to the second cause mentioned above. Resistance to tearing should therefore be regarded as one of the most important properties of rubber. The numerous and widely different methods which have been proposed and used for determining resistance to tearing are proof of this. A complete survey of the literature to 1932 was published by Lefcaditis and Cotton. These authors described about twelve different methods for determining resistance to tearing, proposed a modified form of the method of Heidensohn, and determined the tear-resistance of various mixtures by this method. Subsequently, Lefcaditis studied this method further, and determined the effect of fillers and of mastication on resistance to tearing.
Oxygen Pressure Aging. Improved Equipment
Authors: Freeman L. M.
Published: February 2011

Since the introduction of the oxygen pressure-aging test by Bierer and Davis, prevailing standard conditions for the test have been 70° C. (158° F.) and 300 pounds per square inch oxygen pressure. Various types of equipment have been used; usually the equipment has consisted of a pressure vessel immersed in a constant-temperature water bath to which is connected an oxygen supply. In the majority of instances the equipment has been difficult to operate and maintain for several reasons: Immersion of pressure vessels in a water bath made handling difficult. Corrosion was a continuous source of trouble, causing “freezing” of cover bolts and making it difficult to obtain a leakproof oxygen seal between cover and vessel. This caused loss of oxygen. Each time the pressure vessel was removed from the bath it was necessary to disconnect the oxygen supply and make the connection again when the test was started. This also caused loss of oxygen. If more than one pressure vessel was connected to the oxygen supply and a safety released, the entire oxygen supply was exhausted. The original pressure vessels were relatively large. Since the use of age resistors on a large scale, smaller units have been desirable in order to decrease migration of age resistors and eliminate erroneous results. Some of these operation difficulties were outlined by Ingmanson and Kemp, who also emphasized the importance of temperature control to obtain reproducible results. It is the purpose of this paper to describe an improved oxygen pressure installation which avoids some of these difficulties.
Apparatus for Evaluating Puncture Resistance
Authors: Bashore H. H.
Published: February 2011

In the development of improved compounds for products such as tires, inner tubes, conveyer belts, and hose, the need was felt of a quick and accurate test which would approximate the puncturing conditions these goods might receive in service. For such a test an apparatus was developed which provides for a puncturing pin to be pulled through the rubber sample, the pulling force being supplied by a vertical Scott tensile tester. The adaptation to the Scott machine (Fig. 1) eliminates the necessity of additional load-recording and extension-pulling apparatus. Construction The test apparatus, of which three views are shown in Fig. 2, is composed of two sections. The top section is a hollow tube through which the puncturing pin (Fig. 3A) travels downward in puncturing the sample (Fig. 3B), which is gripped firmly at the periphery between an internal shoulder on the tube and a sleeve (Fig. 3C) within a threaded cap (Fig. 3D) which screws on to the tube. Distortion of the test piece, while the screw cap is being tightened, is prevented by the inner sleeve which presses vertically against the specimen while the turning action is taken up by slippage between the sleeve and the cap. A horizontal pin is attached to the vertical puncturing pin to provide means for attaching the bottom tube section which pulls the pin downward. The hollow tube of the top section is slotted to allow vertical movement of this horizontal pin.
Effect of Curing Temperature upon the Properties of a Rubber-Sulfur Mix
Authors: Park C. R.
Published: February 2011

1—Within experimental error, within the range of temperature and in the case of the mix under consideration, the temperature of cure has no effect on the quality of the vulcanized stock. 2—Certain unexplained differences exist in the results obtained by various methods of aging. 3—The temperature coefficient of vulcanization is 2.50 per 10° C.
Standardization of Ozone Testing
Authors: Kearsley E. P. W.
Published: February 2011

THE progressive deterioration of soft vulcanized rubber, proceeding independently of actual wear, has always been a source of annoyance to the trade. Although evidences of such deterioration are varied in character, the many forms may be conveniently classified as surface deterioration and deterioration throughout the rubber. Surface deterioration, characterized by superficial film formation, is greatly accelerated when vulcanized rubber is exposed to light, particularly rays of short wave length, but that this function of light in the destruction of rubber is indirect in operation was recognized as early as 1883. by Burhardt (Jour. Soc. Chem. hid. 2, 119, 1883). The agency responsible for the changes which rubber undergoes on exposure to the atmosphere is undoubtedly oxygen, and suggested by Spiller (Jour. Chem. Soc. [London] 18, 44, 1865), as far back as 1865. That oxygen is essential for the deterioration of rubber has been shown by Fickenday (Kolloid Ztg. 9, 81, 1911), and many others since. The effect of sunlight on either raw or vulcanized rubber, is believed by Henri (Caout. et Gutta Percha 7, 2848, 1909) to be analogous, although Peachy and Leon (Jour. Soc. Chem. Ind. 37, 56T, 1918) offer the opinion that vulcanized rubber oxidizes less rapidly than raw rubber. Later investigators have proceeded still further in their conclusions, and Tuttle (The Rubber Age, N. Y. 8, 271-2, 1921) states, after studying the acetone solubility curves of vulcanized rubber exposed to light, that the action of the latter is one of oxidation, which when once started proceeds rapidly, due to the catalyzing effect of small amounts of oxidized rubber so formed.
The Influence of Zinc Oxide on the Action of the Principal Accelerators of Vulcanization. The Preparation of Transparent Vulcanized Rubber
Authors: Thiollet R. , Martin G.
Published: February 2011

IT HAS been known for a long time that the action of accelerators of vulcanization proceeds to a conclusion and in a regular way only in the presence of certain metallic oxides, of which zinc oxide is the most widely used. This substance behaves also as a reinforcing pigment, improving the physical properties of vulcanized rubber. We are not at the present time concerned with the second property, we are only concerned with ascertaining under what conditions zinc oxide promotes the action of accelerators. Zinc oxide makes rubber opaque. With certain articles like molded nipples and vulcanized crepe soles, this opacity offers a serious inconvenience and we have studied how it is possible to obtain transparent vulcanizates. To study these questions, we have carried out some vulcanization tests with the principal accelerators on the following three mixtures:
The Influence of the Amount of the Surplus Liquid on the Swelling Maximum of Rubber Jellies
Authors: Blow C. M. , Stamberger P.
Published: February 2011

It has been shown that the so-called “Bodenkörper” effect is caused in the case of rubber by the rubber itself being present in the outside liquid. Rubber swells to a less extent if the solvent contains some dissolved rubber. This effect is reversible if the swollen jelly is placed into solvent containing rubber. An osmotic assumption may be used to explain this process, but it is not possible to draw definite conclusions as to the exact mechanism.