bluuebunny/crossref_metadata_2025 huggingface dataset:
The “Freezing” of Raw Rubber
Authors: Rossem Avan , Lotichius J.
Published: February 2011

The experiments lead to certain general conclusions. 1. Measurements of the changes in density, hardness, and light absorption show that all three properties suddenly decrease at the same temperature, doubtless as a result of the fusion of a crystalline component. 2. Measurements by means of a Bunsen ice calorimeter show that hard frozen samples of rubber have a definite heat of fusion. 3. The “melting point” of frozen rubber changes as time goes on, a phenomenon which may be explained by the growth of crystals. 4. A study of the freezing of raw rubber at ™10° C. and at 4° C. shows that freezing occurs in a few days, and that such rubber melts at a lower temperature than rubber which has been kept frozen for several years, phenomena which are explainable by the ordinary known laws of crystallization.
The Absorption of Oxygen by Rubber
Authors: Kohman G. T.
Published: February 2011

In order to determine the relation between natural aging and oxygen absorption at 80° C., the effects upon oxygen absorption of a number of factors which are known to affect natural aging have been studied. An apparatus is described with which it is possible to follow the absorption of oxygen at constant pressure, temperature, etc., over long periods of time. It has been found that the absorption of oxygen is autocatalytic in nature and appears to consist of at least two separate reactions—a decomposition and an addition reaction. The rate of absorption of oxygen at 80° C. is dependent upon surface area when the area is small, but when it is increased to as large as 40 square centimeters per gram, small variations in surface area are without great effect, probably because under these conditions rates of diffusion are high enough to keep the rubber particles practically saturated with oxygen. As rubber absorbs oxygen it appears to undergo changes similar to those occurring during vulcanization with sulfur. Surface checking is regarded as a preferential surface oxidation. The mechanism of oxygen absorption appears to be different for raw rubber from that for cured rubber. Curing rubber increases both the rate and amount of oxygen absorption over that for raw rubber, and changes the character of the absorption curve. The rate of absorption increases with the degree of cure. The action of anti-agers is one of negative catalysis rather than one of preferential absorption. The rate of oxygen absorption may be greatly retarded by their presence and their effectiveness varies with their concentration and constitution. The type of absorption of ozonized oxygen differs markedly from that for pure oxygen. The former is taken up very much more rapidly at first, but the rate rapidly decreases and less oxygen is finally taken up than in the case of pure oxygen. The action of ozonized oxygen upon rubber appears to protect it from the action of pure oxygen. The reaction between rubber and ozonized oxygen is not autocatalytic.
A Temperature-Recording Micropress for Studying the Course of Vulcanization
Authors: Walton James C.
Published: February 2011

A microscopic study of the course of vulcanization offers many possibilities, especially since, by its aid, the progressive changes which take place during vulcanization can be followed. Using the micropress described above, it is possible to observe these changes and to record the temperature at which they take place. A rubber-sulfur-litharge mixture after cure exhibits no recrystallization of sulfur even when cured for a very short time. A further microscopical study of the vulcanization of this type of rubber mixture may yield an explanation of the bloom-preventing properties of litharge. m-Dinitrobenzene and benzoyl peroxide both vulcanize rubber in the absence of sulfur. The former requires an activator such as litharge and does not recrystallize from the mixture when a cure is effected, whereas the latter does not require an activator and recrystallizes after cure in a manner very similar to sulfur.
Vulcanization without the Use of Sulphur
Authors: Ostromislensky Iwan
Published: February 2011

AS far back as 1915 I described the various methods of vulcanizing rubber without the use of sulphur which I was the first to discover. At the same time these researches gave rise to an international controversy in scientific circles. For reasons beyond my control I have not until now been able either to publish the results of my physical or strictly technical tests of rubbers vulcanized by my new methods, or to place numerical valuations on their physical properties. Many chemists who have repeated my experiments, of course under somewhat different conditions, often obtained results that did not coincide with mine. In consequence a number of discrepancies have gradually crept into the literature and in places even generalizations that are contrary to fact (C. Harries). Among others, B. D. Porritt claims that 1.3.5. trinitrobenzene, although a vulcanizing agent for rubber, is inactive in the absence of oxides. This statement, as will be shown subsequently, is incorrect. Moreover, some of the experimenters have come to the conclusion that the vulcanization of rubber without sulphur cannot be applied practically in the rubber industry.
Essentials for Accurate Gauging for Compressible Material
Authors: Brown Roy W.
Published: February 2011

Variables affecting the accurate thickness measurement of compressible sheet materials such as fabric and rubber stock are indicated as: 1. Linear accuracy of the micrometer. 2. Pressure exerted by the micrometer foot. 3. Size of the micrometer foot. 4. Friction in the micrometer mechanism. A unit area foot pressure of (70.3 gram. per sq. cm.) 1 lb. per sq. in. has been found satisfactory. Friction in the micrometer mechanism is shown to limit the minimum foot pressure to approximately (199.5 grams) .44 lbs., hence a (1.906 cms.) 3/4″ diameter circular foot, or equivalent, is required on present available mechanical gauges. Methods of meeting the above fundamental requirements are indicated for optical and magnetic gauges. Limiting factors in the accuracy sccurable by the use of dielectric gauges arc discussed. The necessity for standardised practices is so apparent as to command consideration of all concerned.
The Consumption of Accelerator during Vulcanization
Authors: Wistinghausen L. v.
Published: February 2011

THE so-called chemical theories of acceleration are based on the transformation of the accelerator during the process of vulcanization, but the quantitative study of such reactions is confronted by tremendous difficulties. From the increase in the amount of combined sulfur with time of cure, Hardman and White have drawn conclusions as to the relative stability of various accelerators. In these experiments they chose conditions which were specific for each accelerator, affording optimum effects. In the following work an attempt has been made to obtain some insight into the fate of the accelerator in the course of heating by a quantitative estimation according to the methods described below of the amount of accelerator found in the acetone extract of vulcanizates with increasing time of cure. In order to study the effect on the accelerator of various ingredients, the type of raw rubber, the quantity of sulfur, and the addition of fillers were considerably varied, while the ratio of accelerator to rubber remained constant.
Studies in the Oxidation of Rubber Mixings
Authors: Davey W. Cecil
Published: February 2011

The rubber airbags used for inflation purposes during the vulcanization of motor covers gradually change during use, and a hard, brittle material forms inside. The bags can, however, be kept in use long after the rubber or, at any rate, the inside rubber, is in an entirely perished condition. The ordinary physical testing methods used for following the changes in rubber are, therefore, not available under conditions where the deterioration is very intense; but the changes can be satisfactorily followed by chemical methods. In the present paper are given briefly some of the results obtained during extensive studies of rubber submitted to prolonged oxidation in a Geer oven at 70° C. Experimental.—The samples were vulcanized for varying periods, and after vulcanizing were sheeted out thin and placed in small beakers in the Geer oven. The progress of oxidation was noted from time to time by measuring the increase in weight and by removing and analyzing portions of the samples. In the early experiments rubber-sulfur mixings were used for simplicity, but later the work was extended to accelerated mixings. In order to obtain a theoretical insight into the changes taking place, the rubbers were in some cases extracted with acetone before oxidation (aging); also the aging of rubber previously extracted with first acetone and then chloroform was studied. In some series samples were submitted to repeated aging and extraction, that is, after the extraction following aging the samples were again returned to the oven. After a further period of aging they were again extracted, and so on repeatedly.
Colloid Chemical Changes in Rubber and Fatty Oils
Authors: Auer László
Published: February 2011

In attempting to solve many of the problems in connection with the chemistry of rubber and of the fatty oils, it is usually found necessary to employ the main principles of colloid chemistry. It is, however, impossible definitely to classify rubber, as either lyophobic or lyophilic in nature. Raw rubber, such as pale crepe or smoked sheet, is in the presence of organic solvents of lyophilic nature, whereas it is entirely lyophobic when dispersed in water. Rubber latex shows an intermediate behavior between lyophobic and lyophilic systems. After neutralization of the electrical charge of the particles, i. e., at the so-called isoelectric point and slightly beyond it, the rubber particles do not flocculate. From this behavior it may be imagined that latex is a lyophilic system, but it is found that a comparatively small excess of electrolyte causes complete flocculation of the rubber, i. e., the salting-out of the rubber particles. Freundlich and Hauser (Kolloid Z., 1925, Erg. Bd. 36) have shown that the rubber particles in latex are made up of a liquid interior and a semi-solid external layer. The protein and resin content of the latex are supposed to be present in this external layer of the particles. Von Weimam (Bull. Chem. Soc. Japan, 3, 157 (1928)) has found that if latex is treated with solvents or solutions which are dispergators (dispersing agents) of protein compounds, and which thus cause a dispersion of the proteins from the external layer of the particles, the emulsion of the rubber hydrocarbon, normally lyophobic in character, will immediately assume a lyophilic nature and the whole system will gelatinize to a solid mass. It seems to be probable that in latex the rubber hydrocarbon is in a lyophilic state and that the partly lyophobic nature of latex is due to the lyophobic character of the protecting protein layer. Immediately this is dispersed, the lyophilic nature of the rubber hydrocarbon becomes evident. Concentrated lithium iodide solution acts as a suitable protein dispergator. As proteins have partly lyophobic and partly lyophilic nature, it is possible that the protein itself forms a gel skeleton containing the rubber hydrocarbon particles dispersed in it. In this case the rubber hydrocarbon may be of a lyophobic nature. Against this hypothesis is the fact that the gelatinization occurs in the presence of protein dispergators and not in the presence of protein coagulators.
The Swelling of Rubber
Authors: Stamberger P. , Blow C. M.
Published: February 2011

Some recent experiments on the diminution of the vapor pressure of solvents in rubber jellies, as well as measurements of swelling pressure, allow us to draw some conclusions as to the nature of the swelling phenomenon. It has been found that, at the same concentration of rubber, the vapor pressure of rubber jellies from rubber of different origin was the same, and the previous mechanical working (mastication) of rubber had also no effect on this value (cf. Stamberger, Rec. trav. chim., 47, 316 (1928)). After the mechanical working, however, it swells in an unlimited manner, and gives as a resulting product up to a concentration of 30 per cent a more or less viscous liquid. This behavior shows that the solvent is not bound by surface adsorption and that there is a great resemblance to the process of molecular disperse solution. The three solvents used for these determinations were carbon disulfide, chloroform, and benzene. The same relative vapor pressure diminution was found when the concentration has been calculated as grams of rubber in 1 gram-molecule of solvent.
A New Plastometer
Authors: Karrer E.
Published: February 2011

AT THE Swampscott meeting of the American Chemical Society an analysis was given of the meaning of plasticity when this term names a property of solids that concerns the molding of plastics such as rubber. A function for plasticity was deduced with some suggestions on the adoption of a C. G. S. unit of plasticity. Also, a design of a plastometer, based upon this analysis, was outlined. It is the purpose of this paper to give a full description of such a plastometer. Original Plastometer A detailed drawing of the instrument as first conceived in February, 1927, is given in Figure 1. The rubber sample, 1, in the form of a cylinder 1 cm. long, 1 sq. cm. cross section, is held between two vertical round rods, A and B, which will be designated as upper and lower plungers. These plungers consist of contacting end caps, 15, 20, of steel mounted upon porcelain tubes, 19, which in turn are cemented into sockets 16, 21. The lower socket, 21, slides through a bushing 22. Its nether end is cut obliquely, and by means of a spring is pressed into contact with the surface of a cylindrical wedge, 23, movable in and out by means of a drum nut, 25, fitted to the threaded end, 24, of the wedge. The height of the sample may be read to 0.001 inch off the scale on the drum nut, 25. The upper socket, 16, slides in a tube, 17, and has a bearing shoulder for the spring, 9, called the force spring. The upper plunger, together with other parts bearing upon it from above, is carried by a light spring, 27.
Stearic and Oleic Acids as Rubber-Compounding Ingredients
Authors: Dinsmore R. P.
Published: February 2011

IT IS proposed in this brief discussion to touch upon the relative effects of stearic and oleic acids in a few typical rubber stocks; then to discuss certain anomalies as to the effect of stearic acid on chemical and physical cure; and, lastly, to consider some of the differences found by use of different accelerators. Inasmuch as oleic acid is the chief impurity in commercial stearic—running from 10 to 15 per cent—it seems desirable to know the behavior of oleic acid alone. Comparison of Stearic and Oleic Acids The following data show the comparative effects of double-pressed stearic and commercial oleic acids in typical rubber
Effect of Increased Quantities of Stearic Acid on Tread Abrasions
Authors: North C. Olin
Published: February 2011

The only conclusion justified, therefore, is that, in so far as abrasion index is concerned, we must fall back on road tests. There the values depend, not only upon the abrasion resistance of the tread, but also upon the design of the tire, its load, position on the car, etc. The Grasselli abrader is of value in laboratory work, but the results must always be carefully scrutinized and must be interpreted within the actual conditions of test.
Effect of Stearic Acid on Reclaimed Rubber
Authors: Winkelmann H. A. , Busenburg E. B.
Published: February 2011

1—Stearic acid does not compare with other softeners in plasticizing efficiency when used in contact with vulcanized rubber scrap during devulcanization. 2—Stearic acid when added as a softener to devulcanized scrap on the mill prior to refining imparts properties which are very desirable. (a) Makes the reclaim batch more plastic, (b) improves tubing and calendering properties, (c) reduces nerve without production of excess tack, (d) improves curing properties (higher tensile strength, higher modulus, and improved molding properties) of reclaimed rubber, (e) when pigments are added it gives better dispersion with improved physical properties. 3—Stearic acid when used in compounds containing reclaimed rubber improves the curing properties of these compounds.
Stearic Acid in Litharge-Cured Rubber Compounds
Authors: Sheppard J. R.
Published: February 2011

Although an organic acid is essential to vulcanization with litharge, smoked sheet usually has enough natural acid for full activation. For example, when 5 per cent stearic acid (or similar softeners) was added to a standard smoked sheet in a high zinc oxide stock the properties were lowered. On the other hand, a “low-grade” rubber, Lapori, was greatly improved in a high zinc oxide formula by stearic and by other acids. Acidic softeners in a high zinc oxide stock increased set, even when they promoted vulcanization. In a pure gum litharge formula with smoked sheet, 1 per cent stearic had but little effect, while in a high gas black formula, 4 per cent stearic raised the tensile (probably due to improved dispersion) but had no marked effect on rate of cure. When litharge was used as the activator for mercaptobenzothiazole, stearic acid had but little effect either in pure gum or high gas black stocks. On the contrary, when zinc oxide was used proper curing was highly dependent on stearic, especially with gas black. The litharge-mercaptobenzothiazole compounds with gas black in tread stock proportions, either with or without stearic, yielded a high tensile over a wide range of cures.
Dispersion of Pigments in Rubber—II
Authors: Grenquist Ernst A.
Published: February 2011

A theoretical conception of the reënforcement of rubber by pigments has been developed. New experimental evidence has been presented which leads to a better understanding of the final dispersion and reënforcement of a rubber compound. It is shown that pigment reënforcement is influenced by (a) rubber structure, (b) the state of aggregation of proteins and natural resins, (c) the isotropic properties of carbonblack particles, and (d) the presence of recrystallized rhombic sulfur at the beginning of vulcanization. A PREVIOUS paper (10)* described the distribution of particles in compounded rubber with special reference to agglomeration and flocculation. It was emphasized that a correct understanding of the final dispersion and reënforcement of a rubber compound could only be obtained with a more thorough knowledge of the structure and physical-chemical properties of rubber and pigments themselves and of the nature of the vulcanization process. New experimental results in regard to these particular points are presented in the following investigation.
On the Reduction of Rubber Stress-Strain Determinations
Authors: Wiegand W. B. , Braendle H. A.
Published: February 2011

In this paper the authors seek means of eliminating the personal equation in the selection of rubber stress-strain data. It became necessary to determine the most probable or true values for tensile strength, elongation, and intermediate values. The authors, therefore, tested a complete inner tube, securing ninety-five breaks, which were then reduced by statistical methods. Frequency distributions of rubber stress-strain data do not strictly obey the law of accidental error, being negatively skewed for breaking values, and positively skewed for intermediate tensiles. The true values, therefore, are not the arithmetic means but the modes, which are found to differ from the arithmetic means in every case to an extent greatly exceeding the probable error of such means. Using these true values, and dividing the ninety-five breaks into successive groups of five, the latter were weighted according to four empirical methods and the results compared with the modal values. The method of selecting three highest elongations out of five together with corresponding tensiles was found most closely to approach modal values. This method is therefore tentatively advanced as a starting point for the standardized selection of rubber breaks.
Importance of Temperature and Humidity Control in Rubber Testing. II—Resistance to Abrasion
Authors: Gibbons W. A. , Bierer J. M. , Bridgewater E. R. , Cranor D. F. , Park C. R. , Schade J. W. , Shepard N. A. , Somerville A. A. , Soule K. J. , Rupert F. E.
Published: February 2011

This study shows that in determining resistance to abrasion the temperature of the room or cabinet should be controlled within ± 1 ° C. in order to avoid significant errors in the results from this source. Below are shown the percentage differences per degree Centigrade obtained with each of the stocks. It must be remembered that this probably holds only over the range of temperatures studied and might change rapidly outside of this range. As the temperature changes from 15 ° C. to 35 ° C., the resistance to abrasion changes per degree Centigrade in the following manner: In the light of the present investigation there will be no great error in results caused by differences in relative humidity either with the raw or vulcanized stock. Where laboratories are equipped to condition raw and vulcanized stock for stress-strain tests, it appears that it would be advisable also to condition samples for determining resistance to abrasion. It would at least tend to produce more nearly uniform results by eliminating possible sources of small errors. As the relative humidity during exposure of raw stock increases from 10 per cent to 100 per cent, the resistance to abrasion per 1 per cent relative humidity changes roughly in the following manner: As these variations are small compared with the experimental error, it is evident that if the relative humidity does not vary over too wide a range its effect may be neglected. The temperature of storing the cured samples while maintaining a constant relative humidity has a negligible effect as in the case of relative humidity. As the temperature increases the resistance to abrasion per degree changes in the following manner:
The Aging of Vulcanized Rubber under Varying Elongation
Authors: Somerville A. A. , Ball J. M. , Cope W. H.
Published: February 2011

1—Deterioration in the oven is approximately 30 per cent greaterat 100 per cent elongation than at 0 per cent elongation. 2—Deterioration in the bomb is almost independent of elongation. 3—Deterioration in ozone is greatest at 5 and 10 per cent elongations. 4—Deterioration in sunlight with respect to stretch is analogous to deterioration in ozone. 5—Cracking of the test rings occurs in both ozone and sunlight when the rings are stretched, but not in the oven or bomb. This cracking is greatest at 5 and 10 per cent elongations. 6—A 40 per cent carbon-black stock shows marked deterioration and cracking in both ozone and sunlight at about 10 per cent elongation. 7—High sulfur causes greater deterioration in ozone and sunlight than low sulfur. 8—Undercures show greater deterioration than the optimum cure in ozone and sunlight. 9—Loading with a filler such as whiting does not change the shape of the ozone- and sunlight-aging curves, and does not materially affect the percentage deterioration. 10—Rubber bands show progres sively poorer aging in the bomb as the stretch increases from 0 to 700 per cent, while in ozone they give an aging curve having the characteristic dip at about 10 per cent elongation, showing the least deterioration at about 400 per cent elongation. 11—Tetramethylthiuram disulfide (3 per cent) as a vulcanizing agent causes rather low percentages of deterioration in ozone and sunlight, and gives fairly flat aging curves. 12—Mineral rubber (24 per cent) causes a smaller percentage deterioration than 4 per cent except at the critical elongation of about 10 per cent. 13—Paraffin (1 per cent) causes pretty bad deterioration in ozone but provides some protection in sunlight. 14—Added antioxidant does not change the shape of the ozone- or sunlight-aging curves but may lessen the amount of deterioration. 15—Two antioxidants may give comparable results in both oven and bomb, but quite different results in ozone and sunlight. 16—Synthetic rubber gives a characteristic ozone-aging curve.
Natural vs. Artificial Aging
Authors: Krall Stanley
Published: February 2011

A CONSIDERABLE number of types of artificial aging are being used today in an endeavor to determine the aging properties of rubber stocks in a short period of time without waiting for natural aging results. The data reported here were taken from some that are being obtained by Sub-Committee XV, Committee D-11 of the American Society for Testing Materials. Experimental Three types of pneumatic tire stocks were aged by two natural and two artificial methods: (1) Slabs were hung separately in the dark. (2) Slabs were hung separately exposed to the weather. (3) One-inch (2.5-cm.) wide strips were hung separately in the Geer (2) oven at 158° F. (70° C.). (4) One-inch (2.5-cm.) wide strips were hung separately in the Bierer (1) oxygen bomb at 158° F. (70° C.) and 300 pounds (21 kg. per sq. cm.) oxygen pressure. The stocks tested were a pure gum stock, a first grade, and a reclaim tread stock as follows:
Accelerated Aging vs. Shelf Aging
Authors: Follansbee Everett M.
Published: February 2011

SAMPLES of rubber-insulated wire were aged by exposing to the diffused light in the physical testing laboratory. The thickness of wall of rubber surrounding the tinned copper wire showed a variation from 0.030 to 0.065 inch (0.76 to 1.65 mm.). The thickness of wall of rubber surrounding the tinned copper wire showed a variation from 0.030 to 0.065 inch (0.76 to 1.65 mm.). The samples were tested for tensile strength and elongation during the aging interval and the results were then compared with accelerated life tests obtained on the same samples when new. Average results on 480 different compounds, ranging in quality from a low-grade compound to a compound containing 60 per cent by weight of crude rubber, show the following relationship between shelf aging and accelerated aging.
Correlation of Various Aging Tests with Natural Shelf Aging
Authors: Cadwell Sidney M.
Published: February 2011

In view of the many variables involved in accelerated and shelf aging, and of the fact that the correlation between the two is only qualitative, it is believed that there are two practical answers to the aging problem. One is incessant care. If the stock is properly balanced, if certain impurities are absent, and if the state of vulcanization is correct, good aging will be obtained. The other answer, which seems to be safer, is to use antioxidants. A certain antioxidant has always improved the aging of all sorts of stocks under all conditions; probably other antioxidants will do as well. Therefore, the use of antioxidants is the practical answer to the aging problem.
Influence of Pigments on Some Physical Properties of Unvulcanized Rubber
Authors: Depew Harlan A.
Published: February 2011

The solubility of pigmented rubber in benzene can be changed by altering the interfacial energy between the rubber and the pigment, and this can be accomplished either by changing the surface of the pigment or by changing the nature of the rubber—as, for example, by treating zinc oxide with sulfur trioxide gas and by adding organic acid to rubber. A plausible explanation has been offered as to why pigments cause rubber to become insoluble. In specific cases it has been possible to predict the solubility of unvulcanized rubber containing pigments. Data are presented showing the change in solubility of unvulcanized rubber during storage in contrast to the constancy in consistency, which gives evidence of a weak rubber structure that develops in storage. The influence of time and temperature of milling on consistency and solubility is shown.
On the Permeability of Rubber Mixings
Authors: Davey W. Cecil , Ohya T.
Published: February 2011

In order to obtain the longest life for motor cover inflating air-bags two features are necessary in the rubber: (a) that it is a mixing not readily oxidized, (b) that it has a low permeability. This latter point has been discussed by Daynes (Trans. Inst. Rubber Ind., 3, 438 (1928)), and it is probable that it is a very important factor as at the temperatures normally used in vulcanizing the rate of diffusion of gas through rubber is greatly increased. It is conceivable that a mix having a low permeability and poor aging would outlast one having high permeability and good aging, as in the former case the deterioration of the rubber would be kept close to the surface. As little information is available on the effect of different mixing ingredients on the rate at which a gas passes through the rubber, the experiments outlined below were made.
The Question of Vulcanization without Sulfur: Experiments on Hot Vulcanization and Vulcanization in Ultravoilet Light with the Aid of 1, 3, 5-Trinitrobenzene and Picric Acid
Authors: Kirchhof F.
Published: February 2011

THIS subject has been previously treated by L. Eck. The present article contains merely the results of a few experiments, which, as might be anticipated, seem suited to assist but little the progress of sulfur's new rivals. We recall that Ostromislensky is said to have succeeded in obtaining vulcanizates of technical value by means of nitro-compounds, especially 1, 3, 5-trinitrobenzene, in the absence of sulfur or any substance forming sulfur.
The Surface Energy between Rubber and Fillers
Authors: Hartner Fritz
Published: February 2011

The purpose of this research was to increase the reliability and accuracy of the calorimetric method elaborated by Bostroem, and to discover and overcome any difficulties or sources of error in order that the method might be applicable to the investigation of problems concerning the chemistry and technology of rubber. The following points were to be considered: 1. The dependence of the “reinforcing” action of a filler on its concentration, and the utilization of the surface energy between rubber and filler. 2. The evaluation of the surface tension in the system raw rubber/filler. 3. The aging phenomenon of rubber and the possibility of making it reversible 4. The comparison of various commercial gas blacks at a given concentration.
The Natural Coagulation of Hevea Latex
Authors: Corbet Alexander Steven
Published: February 2011

A bacteriological study has been made of Hevea latex and it has been found that one organism predominates. The characters and biochemical reactions of this organism have been studied in detail and, as it does not appear to have been denominated previously, the name Bacillus pandora is proposed for it. B. pandora is able to decompose latex substance with production of acid and hence bring about separation of the rubber particles. At a later stage it attacks the proteins with ammonia production and so is responsible for the acid serum and alkaline surface layer observed during the natural coagulation of latex. The reason for the employment of ammonia and sodium sulfite as latex preservatives is discussed.
Notes on Defects in Smoked Sheet and Crepe Rubber
Authors: Fullerton R. G.
Published: February 2011

In the following paragraphs a general account is given of the characteristics and the nature of commonly occurring defects in smoked sheet and crepe rubber, and of the principle underlying methods for their prevention as recommended for estate practice. Many of the defects referred to have no harmful effect on the quality of the rubber after vulcanization, and in the majority of cases the only reasonable excuse for their classification as defects is the unsightly appearance which they impart to the raw product. Since, however, standards of quality at present imposed by the market are based largely on appearance alone, methods have to be devised to prevent the occurrence of these defects.
Thermodynamics of Stressed Vulcanized Rubber
Authors: Gerke Roscoe H.
Published: February 2011

The first and second laws of thermodynamics are applied to the stretching of vulcanized gum rubber stocks. Equilibrium stress-strain curves without appreciable hysteresis are described. The modulus of elasticity of vulcanized rubber for higher elongations obtained from the equilibrium stress-strain curve is capable of giving agreement with predictions of the second law of thermodynamics and the Joule heat effect. The modulus of elasticity from the equilibrium stress-strain curve is practically independent of the time of cure for a range of cures for elongations less than 600 per cent. The customary stress-strain curves show the rubber to be stiffer with increased cure. These facts are additional evidence that the important effect caused by vulcanization is a greater resistance to plastic flow or permanent set.
The Tensile Strength of Java Plantation Rubber
Authors: de Vries O. , Riebl R.
Published: February 2011

In 1927 rumors were heard from different sides regarding a supposed decrease in tensile strength of plantation rubber. These took such a form that The India Rubber Journal took the matter in hand and published a review of data, furnished by different manufacturers and experts. We gave a short review of figures for Java plantation rubber for the years 1923-1926, from which no deterioration in tensile strength was to be seen; on the contrary, the figures showed a slight increase and the conclusion was that, at least for Java plantation rubber, there was no question of deterioration, as was to be expected for anybody conversant with methods of preparation on estates, which are more and more standardized and improved upon. We are now able to supplement these figures with the averages obtained in routine testing in our station during the years 1927-1929. The figures are:
The Coagulation of Hevea Latex
Authors: Beumée-Nieuwland N.
Published: February 2011

In checking up as to which substances are present in latex, we find the following: protein, which can act as a protective colloid, lipoids (sterols, lecithin which can protect the sterol, esters of sterols), and further the contents of the globules, which is probably viscous. In view of the above considerations it is my opinion that one can picture latex as follows: The rubber globules are suspended in a protein emulsion, and have a lipoid wall and a viscous content. In the case of ordinary coagulation, where the pH becomes 4.8, one might therefore form the idea that only the protein flocculated and formed a gel in which the globules stay put. Investigations by Rona and Deutsch have shown that the iso-electric point of lecithin is very much influenced by the presence of protein, and it is therefore probable that the lipoid substances will be flocculated already at that lower pH. When both protein and lecithin, the two hydrophilic colloids, are flocculated, there still remains the hydrophobic colloid sterol, which can easily be flocculated by the salts present. Then the contents of the globules are no longer protected, but stay included between the gels. The latter flocculation is irreversible and, therefore, once coagulation has taken place, inversion is impossible.
Studies of Conditions Affecting the Vulcanization of Rubber. IV. Heat Reaction during Vulcanization
Authors: Toyabe Yutaka
Published: February 2011

The heat reaction during vulcanization was traced by means of a differential thermocouple, of which one contact point was placed in a sealed glass tube enclosed in the sample and the other in the heating medium of a small electric furnace, e. g., asbestos yarn windings. Specially prepared rubber precipitated from latex by acetone was milled with varying quantities of sulfur and was vulcanized at 155° C. The heat change was observed during the vulcanization. The curves are shown in Fig. 1. Although the absolute or relative amount of heat evolved seems to be shown by the ordinate of the curves, it is not the case because of the uneven thermal resistivity of the samples. From these curves, therefore, it may only be seen that the profiles of them are similar to each other, showing maximum points at 60 to 70 minutes and decreasing asymptotically to a horizontal line, i. e., the temperature of the heating medium of the furnace. It is observed that the maximum points lie at about the same period, though the sulfur contents of the samples were varied. Similar results are shown by Perks (J. Soc. Chem. Ind., 1926, 142T). The present author analyzed the vulcanizates corresponding to the maximum points of the curves, the results of which are shown in the following table.
Evolution of Hydrogen Sulfide from Vulcanized Rubber
Authors: Wolesensky Edward
Published: February 2011

The rubber-sulfur compound in vulcanized rubber splits off hydrogen sulfide at all times and at all temperatures between 25° C. and the temperature of complete thermal decomposition. The rate of evolution of the gas depends upon the temperature, time, the proportion of combined sulfur, and possibly other factors. The reaction affords a new explanation of the formation of hydrogen sulfide during vulcanization, and possibly also, in part at least, of the excess of combined sulfur over that required by the formula C5H8S. It may also be another factor in aging, though, perhaps, only a minor one, and presents a new problem in the regeneration of rubber.
Recovering Lead in Rubber Factory
Authors: Haushalter F. L.
Published: February 2011

When we say that lead melts at 621 ° F. and has a tensile strength of 1900 lb. per sq. in., we have in mind pure lead that has not been remelted many times in crucibles that are not always clean. This metal, too, as ordinarily used in pipes and conduits has been drawn; stresses have been set up in the lead by this process, and their magnitude depends upon several factors, such as temperature of extrusion, extent of oxidation, rate of cooling, and impurities accumulated in the remelting. Where lead is melted and extruded onto wire and hose the tensi1e strength of such lead, when removed from the wire or hose, has increased to about 2400 lb. per sq. in. The percentage elongation, however, has decreased from about 50 to about 25. Industries where lead is used again and again by remelting, as in the rubber industry, where hose is vulcanized in a lead casing, the casing removed after vulcanization of the hose and remelted, the problem of controlling the physical properties of the lead becomes a serious one. After pure lead has been extruded onto the hose and the tensile strength thereby stepped up to about 2400 lb. per sq. in., the tensile strength then falls appreciably below the original value of 1900 lb. per sq. in. as soon as the vulcanization process begins, with the temperature of vulcanization at 280° F. When the samples of lead as stripped from the hose after vulcanization were tested for tensile strength at various temperatures, the curve approximated a straight line. A stress-strain curve on the lead at a temperature of 280?? F. indicates that at a tensile stress of about 600 lb. per sq. in. the lead begins to yield, for the curve departs from the original slope.
Polymerization Reactions under high Pressure. I. Some Experiments with Isoprene and Butyraldehyde
Authors: Conant J. B. , Tongberg C. O.
Published: February 2011

1. The rate of polymerization of isoprene under high pressures has been studied. The reaction is subject to positive catalysis by peroxides and negative catalysis by hydroquinone. Although the reaction is of a high order, the rate is approximately in accord with a first order reaction presumably because of an autocatalytic effect. The temperature and pressure coefficients of the rate have been estimated. The solubility and elasticity of the product depend on the extent to which the isoprene has been polymerized; when the polymerization is practically complete at room temperature at 12,000 atm. the product is very insoluble 2. The action of high pressures on n-butyraldehyde produces a solid only slightly soluble in organic solvents. It reverts to n-butyraldehyde rapidly. It is suggested that this polymer is similar to the well-known polymers of formaldehyde but that the energy relationships are such that the polymer is stable only at high pressures.
Natural and Synthetic Rubber. IV. 4-Methyl-4-Octene by Isoprene Ethylation
Authors: Midgley Thomas , Henne Albert L.
Published: February 2011

Isoprene has been ethylated; 4-methyl-4-octene was formed exclusively. The structure of this nonene is in agreement with the usual behavior of a conjugated double bond system. This type of addition is further evidence in favor of the hypothesis which regards the polymerization of isoprene to synthetic rubber as the formation of long chains of isoprene units linked together- by ordinary valences in the 1,4-position.
Natural and Synthetic Rubber. V. Tetramethyloctadiene
Authors: Midgley Thomas , Henne Albert L.
Published: February 2011

Dimethylbutadiene treated with potassium and alcohol gives 2,3,6,7-tetramethyl-2,6-octadiene and methyl-rubber. The structure of the first hydrocarbon has been established, and is used as an evidence that the methyl-rubber formula must be a long, open chain. This is also regarded as an evidence in favor of the chain formula of natural rubber.
Isoprene and Rubber. XIII. The Constitution of Rubber
Authors: Staudinger H. , Asano M. , Bondy H. F. , Signer R.
Published: February 2011

It is of special interest in connection with the structure of rubber as well as that of all natural products of high molecular weight that two basically different viewpoints exist, and that both have been supported by experimental investigations. Both these concepts concerning the constitution of rubber are discussed in the following paper. I. The Constitution of Rubber According to Pummerer Pummerer defends the correctness of the basic concept of Harries “that a parent rubber hydrocarbon exists, which as a result of some condition tends to association and as a result gives the impression of a rubber of gigantic molecular weight. The question of whether this point of view is justified is of the greatest interest to colloid chemistry. The tendency to association may depend upon various factors, for example, upon the state of saturation, upon the size, or even upon the form of the molecules”. Pummerer expresses similar ideas, as does Bergmann about the constitution of polysaccharides and albumins. This concept is supported by Pummerer by important experiments.
Some Studies Relating to the Compression and Shear Resistance of Rubber
Authors: Ingmanson J. H. , Gray A. N.
Published: February 2011

1. A method for evaluating rubber covered wire by correlating compression, shear, and adhesion tests with bomb aging has been described. 2. It has been shown that the shear test described can be used for evaluating vulcanized rubber compositions with certain advantages over tests commonly in use. 3. Methods and some few data regarding the compression characteristics of several rubber stocks and other deformable materials have been given.
The Compressibility of Rubber
Authors: Adams L. H. , Gibson R. E.
Published: February 2011

Although many of the elastic properties of rubber have been investigated with very interesting results, no measurements have been made, so far as we know, of its cubic compressibility at high pressures. Those measurements which have been made at low pressures yield results varying from 93×10−6 obtained by Clapeyron to an estimate of the order of the compressibility of bronze (about 1×10−6) given by Amagat. As the compressibility of rubber enters as a minor correction into most compressibility measurements at high pressures, it is very desirable to have a reliable estimate of its value. In this communication we propose to give the results of experimental determinations of the compressibility at 25° of three samples of rubber which were furnished to us by H. L. Curtis and A. H. Scott of the U. S. Bureau of Standards. The samples are described as follows: Sample A.—Hard rubber from panel made by the Goodrich Company. It is a rubber-sulfur compound containing no inorganic fillers. The total sulfur amounts to 27.4 per cent, of which 0.21 per cent, is free sulfur. The density is 1.149 at 27° C. Sample B.—A rubber-sulfur compound containing 90 per cent. smoked rubber and 10 per cent. sulfur and vulcanized 105 minutes at 300° F. Density = 0.990 at 25°. Sample C consists of pale crepe rubber 90.75 per cent., zinc oxide 5 per cent., sulfur 4 per cent., tetramethylthiuram disulfide 0.25 per cent. It was vulcanized for 30 minutes at 260° F. Density = 0.990 at 27°.
Studies in the Oxidation of Rubber Mixings
Authors: Davey W. Cecil
Published: February 2011

In a former communication (Trans. Inst. Rubber Industry, 4, 493 (1929)) some results were presented of studies on the changes of rubber samples oxidized to an intense degree. For that investigation the oxidation temperature used was 70° C. (Geer Oven), while in the present paper results are given of experiments made at 100° C. and their relation to the results at the lower temperature are discussed. The experimental procedure was similar to that previously used, the preliminary stage being the sheeting out of small portions of the samples by passing them through the tightly closed cold rolls of a laboratory mill. The weighed samples were then suspended by strings in an ordinary steam oven fitted with an air inlet near the bottom and an outlet at the top. The progress of oxidation of each sample was noted from time to time by (a) determining the increase in weight, and (b) removing and estimating the amount of resinous matter present by extraction with acetone for 24 hours. In some instances the acetone extraction was preceded by an extraction with chloroform.
Alternating Behavior of Fatty Acids in Rubber Compounds
Authors: Garner T. L.
Published: February 2011

It has been shown (Bayer, Ber., 10, 1286 (1877); Garner and Randall, J. Chem. Soc., 125, 881 (1924)) that the alternations in the melting points and heats of crystallization of normal fatty acids were due to differences in the crystalline structure. Two distinct curves of behavior corresponding to the acids with odd and even numbers of carbon atoms have been shown for the heats of crystallization. McKee (Naturwissenschaften, 11, 938 (1923)) discussing the fats used in the diet of diabetics, states that in the case of glycerides of acids with an uneven number of carbon atoms these are tolerated and their use leads to gradual reduction in acidosis. Glycerides having an even number of carbon atoms break down during metabolism to form butyric, oxybutyric, and acetoacetic acids. Smith and Boone (Ind. Eng. Chem., 19, 398 (1927)) have experimented with the addition of purified fatty acids to standard mixings of different kinds of raw rubber. They employed molar proportions of the acid to conform with the recommendations of Kratz, Flower, and Coolidge (Ind. Eng. Chem., 12, 317 (1920)) that comparisons of organic accelerators should be made with molecularly equivalent amounts of the substances in question. They determined the tensile strength and elongation of the vulcanized products and found no relations between the elongation and the number of carbon atoms present in the acids, but in the case of the tensile strength an alternating effect was evident, the extent of the differences being affected by cure. The tests were carried out on two kinds of rubber, namely, blanket crepe and pale crepe, and the alternating effect of the acids on the tensile strength was more marked in the former case. As pointed out in the paper, the difference in behavior of the two kinds of rubber when treated with fatty acids was presumably due to the difference in the kind and proportions of acids which they originally contained. In fact, in the case of pale crepe the fatty acids already present in the raw rubber masked the alternating behavior to a marked extent, and the curve obtained was in most respects quite different from that obtained with blanket crepe.