Properties Of Carbon Blacks Research Articles

Modification of Carbon Black with Ionizing Radiations

Abstract It is well-known that the reinforcing properties of carbon blacks used as active fillers for rubber depend to a considerable extent upon the adsorption properties of the surface of the carbon black particles. The presence on this surface of atoms and groups of polar or apolar character chemically bound with it, the surface relief and the presence of atoms with unsatisfied valencies in the hydrocarbon framework of the elementary crystallites determine the specific adsorption properties of carbon black of various types. In the present investigation we demonstrate the possibility of modifying the surface of the carbon blacks by the action of ionizing irradiation and by the radiochemical “sewing-up” of various compounds on their surface. Such modified carbon blacks have a considerable influence upon the physico-chemical properties of the resulting vulcanizates, which may make is possible to create new materials. The investigation was devoted to: (1) Ukhta thermal black—a typical representative of the soft semireinforcing blacks (practically not oxidized) ; (2) channel black from the same works—a hard active black, having a markedly oxidized surface, capable of irreversible interaction with the surface of the rubber and with the compounding ingredients.

Effect of Heat Treatment on Reinforcing Properties of Carbon Black

Abstract The high degree of stiffness or modulus which reinforcing carbon blacks impart to rubber has often been associated with reinforcement. Modulus appears to be associated with the chemical nature of the carbon black surface ; when the carbon black surface is cleaned of combined oxygen and hydrogen, a drastic drop in modulus occurs, and this is not accompanied by an equally drastic decrease in tire road wear. Reinforcing and semireinforcing carbon blacks have been heat-treated at successive increments through a temperature range of 1000° to 2700° C. Treatment up to 1500° results in removal of all combined oxygen and hydrogen, followed by an increasing degree of graphitization at higher temperatures. These carbon blacks have been compounded in a standard natural-rubber compound and properties evaluated. Modulus is profoundly altered by the chemistry of the carbon surface. Electrical resistivity passes through a minimum at 1500° C. Scorchiness or premature vulcanization improves with removal of volatile matter. The degree of graphitization of the carbon has only a minor effect on rubber properties. A highly graphitized carbon black still imparts a high degree of resistance to abrasive wear to tire treads.

Effect of Heat Treatment on Reinforcing Properties of Carbon Black

Effect of Heat Treatment on Reinforcing Properties of Carbon Black

Structure and Properties of Carbon Black - Changes Induced by Heat Treatment

Structure and Properties of Carbon Black - Changes Induced by Heat Treatment

On carbon blacks as raw materials for composition carbon resistors

Composition carbon resistors were made using 18 kinds of carbon blacks of various manufacturing processes as raw conductive materials and phenol resins as binders on a definite condition, and their voltage coefficients and noises were estimated. Comparing those results with the chemical and physical properties of carbon blacks used, following facts were convinced. Carbon blacks of smaller particle sizes and of better uniformity inparticle sizes are more suitable for resistors from the view points of those properties, almost without connection with their chemical properties. An acetylene black showed an exceptional case in spite of its smaller size and better uniformity, but the reasons were not made clear.

Mechanical Processing of Carbon Blacks. Resultant Effects in GR-S Compounds

Abstract It was suggested that carbon blacks owe some of their characteristic properties to a tendency for individual particles to cluster into chainlike groupings or secondary aggregates. Results of mechanical processing experiments show that application of mechanical work altered or destroyed secondary aggregates. This conclusion was made since resistance to compression had been permanently overcome. Analytical measurements confirmed the supposition that secondary aggregates had been altered or destroyed, since oil absorption and liquid retention values markedly decreased with mechanical work. Finally, properties of compounded GR-S stocks were seriously altered—namely, smoothness of milled stock, high modulus, and enhanced electrical conductivity. It is concluded that these properties were originally caused by the presence of secondary aggregates or structure units. Alternative interpretations of these data are possible—namely, it might be concluded that it was not possible to disperse the densified material to the same extent as the original carbon black. However, this hypothesis contends that a large particle size material is being dispersed. Therefore, a decrease in tensile strength should have been noted. There is also some meager evidence suggesting that the chemical nature or activity of the carbon black surface was altered, so that its contribution to modulus was limited. It is believed, however, that most of the evidence offered by the data presented here preponderantly supports the structure theory of high modulus blacks. The authors consider these results as preliminary in the study of the structure properties of carbon blacks. They appear to be of sufficient interest to be brought to the attention of those studying reinforcement. Data available at present do not permit an interpretation of the contribution of structure to properties of “smooth-out” modulus and electrical conductivity of compounded rubber stocks.

Conductivity of Rubber Tread Stocks. Effect of Properties of Carbon Black

Abstract The conductivity of a rubber tread stock compounded with 50 parts of carbon black increases exponentially as the particle size of the black decreases. As the crystal structure of the carbon approaches a more graphitic form, the conductivity increases sharply. Noncarbon surface components, either of the hydrocarbon or carbon oxide type, decrease the conductivity. This effect is less important than particle size or crystal structure. However, increases in conductivity or more than tenfold can be brought about by removal of surface components.

Surface Area and Properties of Carbon Black

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

Surface Area and Properties of Carbon Black

Abstract The surface areas of a number of commercial carbon blacks have been determined by the low-temperature adsorption isotherm technique. Thermal decomposition and other nonimpingement type blacks possess areas of 15 to 64 M2 per gram. Channel blacks commonly employed as reinforcing agents in rubber have areas around 100 M2 per gram. Ink and color blacks range from 100 to nearly 1000 M2 per gram. The color values of these carbons increase with surface area. The relation of iodine and diphenylguanidine adsorption to surface area has also been studied. Iodine adsorption is a direct function of surface area and, with the exception of certain high-volatile blacks, may be used as a direct measure of total surface. The adsorption of diphenylguanidine depends much more strongly on the volatile content of the black rather than its total surface. While rubber reinforcement depends in a general manner on surface area, certain blacks of nearly identical surface vary widely in the properties they impart to compou...

Adsorptive Properties of Carbon Black. A New Angle

Abstract (1) A new method has been developed for quantitatively determining the adsorptive properties of finely divided fillers, whereby advantage is taken of the partition coefficient of solutes between immiscible solvents. If carbon black is shaken with a mixture of polar and non-polar solvents (e. g., benzene and water) the carbon black is always retained in the non-polar layer after separation. The behavior with other fillers has been investigated. This phenomenon has made it possible rapidly to determine the amount of iodine, benzoic acid, or phenol adsorbed by carbon black from the two phase liquid system by titration of the aqueous layer after equilibrium has been reached. A knowledge of the partition coefficient then enables the adsorption from the non-polar liquid to be readily calculated. (2) The adsorption isotherms for carbon black, degassed carbon black and heat-treated carbon black have been investigated, employing this technic. (3) Since the partition coefficient of a solute between immiscible liquids is unaffected by the presence in either liquid of a substance insoluble in the other phase, the method developed can be used to investigate the effect of dispersed rubber, sulfur, etc., upon the adsorptive properties of the filler. Sulfur and stearic acid were found to have a negligible effect upon the absorptive power of carbon black for phenol benzoic acid, and iodine; whereas the presence of 1 per cent rubber in the benzene phase greatly reduced the ability of carbon black to adsorb the first two of these substances. This action of rubber in depressing adsorption also occurred in the presence of sulfur and stearic acid, and suggests powerful adsorption of rubber upon the surface of carbon black.

Experiences with a Direct Accelerator-Adsorption Test

Abstract A method for determining the accelerator adsorption properties of carbon blacks is described. This method is novel in that an extremely dilute solution of diphenylguanidine in benzene is employed. Application of the test to a large number of carbon blacks has revealed its practical value as a measure of those variations in adsorption properties which are of teal significance to the rubber manufacturer. The method has been employed in several separate control laboratories and it has been found to be of distinct value in indicating quality of production. Since the results can be interpreted without knowledge of source or history of the particular carbon black being tested, the test can be employed for control purposes by the rubber manufacturer as well as by the carbon black manufacturer.

Influence of Physical Properties of Carbon Black on Its Tinting Strength

Abstract 1—Tinting strength is not an absolute function of particle. 2—No direct ratio exists between tinting strength and hiding power. 3—The thickness of the film of adsorbed gases on the carbon-black particles determines the tinting characteristics. 4—The volatile matter present and the oil-absorption properties serve as a measure of the relative thickness of such films. 5—The completeness with which these gases are displaced materially affects the tinting strength. 6—Complete displacement is only possible when the inter-facial tension produced by the dispersing medium at the surface of the carbon-black particle is sufficiently low to assure complete wetting.

Some Properties of Carbon Black. I. Adsorption

Abstract The diphenylguanidine (O. P. G.) adsorption test correlates well (0.8) with rubber-curing behavior in organically accelerated mixings, in respect to the broad classes of carbon black, but only moderately (0.4) in respect to standard rubber carbon black. The D. P. G. or similar adsorption test, although correlating better than the volatile-matter test, is therefore not capable of predicting with precision the rubber-compounding behavior of standard (rubber) carbon black. Carbon-black adsorption is much more marked in the alkaline than in the acid range. While heat-activated carbon blacks show marked increase in D. P. G. adsorption, heat-deactivated carbon blacks show greatly reduced alkaline and slightly increased acid adsorption, 2 which probably explains the anomalous iodine adsorption of heated blacks noted in the literature. In litharge compounds without added fatty acid, high-adsorption blacks spoil the cure by removing the fatty acid present in the rubber. Heat-deactivated carbon black leaves the cure relatively unaffected. In litharge compounds containing an excess of added fatty acid, however, both heat-deactivated and high-adsorption blacks improve the cure, doubtless through removal of excess acid. In general, for carbon black-litharge compounds a low-adsorption carbon black is preferable because it permits a minimum dosage of fatty acid.

Influence of Physical Properties of Carbon Black on Its Tinting Strength

Abstract 1—Tinting strength is not an absolute function of particle. 2—No direct ratio exists between tinting strength and hiding power. 3—The thickness of the film of adsorbed gases on the carbon-black particles determines the tinting characteristics. 4—The volatile matter present and the oil-absorption properties serve as a measure of the relative thickness of such films. 5—The completeness with which these gases are displaced materially affects the tinting strength. 6—Complete displacement is only possible when the inter-facial tension produced by the dispersing medium at the surface of the carbon-black particle is sufficiently low to assure complete wetting.

Some Properties of Carbon Black I—Adsorption

Some Properties of Carbon Black I—Adsorption

Some Properties of Carbon Black

Abstract The term “carbon black” will be used in this paper to include all the varieties of moderately pure carbon existing in the form of soot. So far as the rubber industry is concerned, four distinct types of carbon black are in general use, as follows: (1) Gas Black.—Sometimes itself called carbon black, made by the incomplete combustion of natural gas, the principal component of which is methane. The flames of burning gas impinge on metal surfaces, on which the black is deposited. (Cf. Neal and Perrott, Bull. No. 192, United States Bureau of Mines, 1922.) (2) Acetylene Black.—Produced by the explosive combustion of purified acetylene in closed chambers. (3) Lamp Black.—Obtained by incomplete combustion of fats, oils, tars, etc. Unlike the gas black particles, which are removed from the interior of the flame, those of lamp black pass through the outer layer before deposition. (Twiss, India Rubber J., 65, 607, 651, 393 (1923)). (4) Thermatomic Black.—Made by thermal decomposition of natural gas out of contact with air. The difference in physical properties of these blacks depends largely on differences in heat treatment during manufacture. They are arranged above in order of the size of the individual particles, those of gas black easily averaging the smallest.