Identification of Carbon Black by Surface-Area Measurements

1943 ◽  
Vol 16 (3) ◽  
pp. 687-691
Author(s):  
F. H. Amon ◽  
W. R. Smith ◽  
F. S. Thornhill
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Point Of View ◽  
Curing Temperature ◽  
Single Type ◽  
Surface Areas ◽  
Vulcanized Rubber ◽  
Chemical Combination ◽  
Black Surface ◽  
Rubber Stock

Abstract In general then, we may conclude that carbon black can be recovered from rubber stocks with unchanged surface-area. The nitric acid technique is the most effective method of effecting the separation. The digestion temperature must be controlled to between 60° and 70° C, for a total of not more than 3 to, 4 hours. This method of identifying the carbon black in an unknown rubber stock is directly applicable only in the presence of a single type of carbon black. If blends of blacks are employed in the material under investigation, some secondary identification is also required. The nonimpingement-type blacks, for example, are readily identified by microscopic observation. From the known surface-areas of these materials and the total per cent carbon present in the stock, a fairly positive identification of the blend can be made. The fact that carbon black can be recovered quantitatively and with unchanged surface-area from vulcanized rubber stocks appears to lend impetus to a physical concept of carbon black reinforcement. This point of view implies that any chemical combination between the ingredients of the rubber stock and the carbon black would be evidenced by some alteration in the surface of the latter. A few experiments were performed in an attempt to establish to what extent this concept was valid. One hundred grams of Grade-6 carbon black were intimately mixed with 6.6 grams of sulfur. This is about the ratio in which they are present in a standard rubber batch. Samples of this mixture were subjected to the standard curing temperature of 134° C for 30, 60, and 90 minutes. The free sulfur was then extracted for 40 hours with acetone ,and the combined sulfur on the carbon was determined. Values of 0.16, 0.21, and 0.4 per cent combined sulfur were obtained. The original sample of Grade-6 carbon black had a surface-area of 108 square meters per gram. The extracted sample of black containing 0.4 per cent of combined sulfur had a surface-area of 109 square meters per gram. These values are identical within experimental error. While unaltered surface-area need not necessarily be interpreted as evidence of complete lack of surface reactions, it is the authors' opinion that the extent of chemical combination at the carbon black surface is very small. This interpretation is in accord with the views expressed in a previous publication3, where it was suggested that the chief role of carbon black in rubber reinforcement may rest on its ability to orient the chains of rubber molecules and thus alter the extent and type of rubber-sulfur bonds normally formed in non-reinforced rubber stocks.

A Low-Cost, Rapid Method for Determining Carbon Black Surface Area

1983 ◽  
Vol 56 (2) ◽  
pp. 440-449 ◽  
Author(s):  
Jerry B. Pausch ◽  
Caroline A. McKalen
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Low Cost ◽  
Control Procedure ◽  
Simple Method ◽  
Surface Areas ◽  
Measuring Surface ◽  
Headspace Gas ◽  
Black Surface ◽  
Area Data

Abstract For practical use of this method as a quality control procedure for carbon black, a combination of 4 mm3 and 6 mm octane doses appears to be the best compromise for a sample size of 0.1 g. These conditions cover well, a surface area range of 10–140 m2/g and surface areas up to 180 m2/g can be estimated. Larger doses of octane will extend the linear range on the high side, but the slope of the calibration curve is reduced significantly. A smaller slope yields lower precision. The regular testing of standards appears necessary to achieve optimum accuracy of surface area. At the present time, the method is calibrated against nitrogen surface area data, so the advantage of octane more closely simulating the rubber molecule is lost. We need to obtain adsorption isotherms that are better defined throughout the linear adsorption coefficient range for a number of carbon blacks, and thus become self-calibrated against octane. A more versatile dosing technique is preferred to enable these experiments to be run. An alternate approach is to correlate the headspace results with data obtained by other techniques such as CTAB. The advantages of automated headspace gas chromatography for measuring surface area have been outlined before . It is a rapid and simple method, which also exhibits relatively low labor involvement. The number of samples capable of being analyzed per day is significantly higher than by any other technique.

Accessibility of the Carbon Black Particle Surface to Elastomers

1970 ◽  
Vol 43 (2) ◽  
pp. 464-469 ◽  
Author(s):  
P. Aboytes ◽  
A. Voet
Keyword(s):  
Carbon Black ◽  
Particle Surface ◽  
Carbon Black Particle ◽  
Carbon Chain ◽  
Chain Structure ◽  
Inert Atmosphere ◽  
Chemical Surface ◽  
Molecular Weights ◽  
Surface Areas ◽  
Black Surface

Abstract Experimental carbon blacks were prepared with the generally encountered slit-shaped pores of discrete dimensions of 9,12.5, and 16 A˚ width in greatly differing size distribution. Equilibrium adsorption in the saturation range was determined in n-hexane for butadiene—styrene elastomers of the SBR type of average molecular weights of 1500; 2000; 15,000; and 300,000. In attempting to correlate the saturation adsorption values with carbon black surface areas, it was found that a simple linear relation in the range investigated could only be obtained by assuming that pores of 9 A˚ width were inaccessible to SBR of 1500 and 2000 MW; that pores of 9 and 12.5 A˚ width were inaccessible to SBR of 15,000 MW; and that all pores smaller than 20 A˚ width were inaccessible to SBR of 300,000 MW. The data indicated that there are no differences between high, regular and low structure blacks in saturation elastomer adsorption under conditions of equivalent dispersion. Equally, upon breaking the persistent carbon chain structure by dry ball milling in an inert atmosphere and equalizing the chemical surface properties by removal of surface oxides, no difference in elastomer adsorption from solution was observed. It must be concluded that commonly used high molecular elastomers do not have any access to smaller carbon black pores. Since access to the surface is a prerequisite for reinforcement, it is obvious that the surface in the pores of carbon black generally does not participate in reinforcing elastomers. The elastomer adsorbed per unit external black surface area appears to be independent of the carbon chain structure, indicating that the so called surface activity of the carbon black is independent of the chain length.

Carbon Black Surface Areas by the Harkins and Jura Absolute Method

1967 ◽  
Vol 40 (5) ◽  
pp. 1305-1310 ◽  
Author(s):  
G. Kraus ◽  
K. W. Rollmann
Keyword(s):  
Particle Size ◽  
Carbon Black ◽  
Surface Area ◽  
Nitrogen Adsorption ◽  
Absolute Method ◽  
Carbon Blacks ◽  
Surface Areas ◽  
Particle Size Determination ◽  
Light Reflectance ◽  
Adsorption Surface

Abstract The Harkins and Jura (HJ) absolute method of surface area determination (Harkins and Jura, J. Am. Chem. Soc. 66, 919, 1944) has been applied to a large number of carbon blacks. Surface area is calculated from the heat of immersion of the solid powder covered by a preadsorbed multilayer of the immersion liquid. For non-porous carbon blacks good agreement with nitrogen adsorption surface areas is obtained, but with porous blacks the HJ method gives smaller values since micropores are filled and bridged over by the pre-adsorbed film. Thus the HJ areas are more nearly representative of particle size and may be used to calibrate indirect methods of particle size determination. An example of this is shown using light reflectance values on dry carbon black and possible complications due to particle size distribution in the use of the reflectance test are discussed.

A Comparison of Methods for Determining Surface Areas of Carbon Black

1973 ◽  
Vol 46 (1) ◽  
pp. 192-203 ◽  
Author(s):  
R. A. Klyne ◽  
B. D. Simpson ◽  
M. L. Studebaker
Keyword(s):  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Surface Areas ◽  
Furnace Black ◽  
Area Increase ◽  
Experimental Errors ◽  
Specific Surface Areas ◽  
Surface Area Increase

Abstract 1. The various tint tests correlate with each other—it does not make much difference which of the three procedures is used. The discrimination between similar blacks is comparable. Specific surface areas obtained by the three methods are comparable and differences appear to be due to experimental errors. (Compare Figures 5–7). 2. Surface areas larger than some 90 to 100 m2/g cannot be reliably determined from tint strength measurements alone. 3. Structure exerts a pronounced effect on tint strength of furnace blacks, especially above 90 to 100 m2/g. Porosity and/or composition are apparently also variables which affect tinting strength. 4. Densichron reflectance on the dry carbon black can be used to estimate specific surface areas up to about 140 m2/g; but, since theabsoluteerrorincreases as the specific surface area increases, this method loses some of its reliability at values above about 110 m2/g. The relative error in reflectance determinations does not vary greatly over the furnace-black range. Densichron reflectance is influenced by composition, evidently due to composition-related differences in optical properties of the carbons. 5. In CTAB adsorption measurements, titration errors and handling errors tend to be rather constant for blacks of different surface area. Hence, CTAB permits better discrimination among blacks of small particle size. 6. The errors in Densichron reflectance surface area increase with specific surface area. Hence, the deviations between CTAB and reflectance surface area which are due to experimental error increase with the surface area of the sample.

scholarly journals A Case Study of Waste Scrap Tyre-Derived Carbon Black Tested for Nitrogen, Carbon Dioxide, and Cyclohexane Adsorption

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4445 ◽  
Author(s):  
Zuzana Jankovská ◽  
Marek Večeř ◽  
Ivan Koutník ◽  
Lenka Matějová
Keyword(s):  
Activated Carbon ◽  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Sorption Capacity ◽  
Specific Surface Area ◽  
Textural Properties ◽  
Pyrolytic Carbon ◽  
Surface Areas ◽  
Wide Range

Waste scrap tyres were thermally decomposed at the temperature of 600 °C and heating rate of 10 °C·min−1. Decomposition was followed by the TG analysis. The resulting pyrolytic carbon black was chemically activated by a KOH solution at 800 °C. Activated and non-activated carbon black were investigated using high pressure thermogravimetry, where adsorption isotherms of N2, CO2, and cyclohexane were determined. Isotherms were determined over a wide range of pressure, 0.03–4.5 MPa for N2 and 0.03–2 MPa for CO2. In non-activated carbon black, for the same pressure and temperature, a five times greater gas uptake of CO2 than N2 was determined. Contrary to non-activated carbon black, activated carbon black showed improved textural properties with a well-developed irregular mesoporous-macroporous structure with a significant amount of micropores. The sorption capacity of pyrolytic carbon black was also increased by activation. The uptake of CO2 was three times and for cyclohexane ten times higher in activated carbon black than in the non-activated one. Specific surface areas evaluated from linearized forms of Langmuir isotherm and the BET isotherm revealed that for both methods, the values are comparable for non-activated carbon black measured by CO2 and for activated carbon black measured by cyclohexane. It was found out that the N2 sorption capacity of carbon black depends only on its specific surface area size, contrary to CO2 sorption capacity, which is affected by both the size of specific surface area and the nature of carbon black.

Carbon Black Morphology in Rubber

1977 ◽  
Vol 50 (4) ◽  
pp. 842-862 ◽  
Author(s):  
G. C. McDonald ◽  
W. M. Hess
Keyword(s):  
Image Analysis ◽  
Carbon Black ◽  
Size Distribution ◽  
Surface Area ◽  
Surface Activity ◽  
Unit Size ◽  
Wear Rates ◽  
Rubber Compounds ◽  
Activity Structure ◽  
Black Surface

Abstract Electron microscope image analysis of carbon blacks in specific rubber compounds has greatly expanded the range of useful applications for studies of this type. This dispersed carbon-gel procedure has improved the sampling and test precision at operating speeds that are now reasonably comparable to the simple colloidal procedures for characterizing carbon black. Improved models have been developed for deriving black surface area and intraunit occlusion capacity. The EM image analysis approach has been useful in applying certain principles of reinforcement theory, as well as in explaining rubber property differences that are attributable to carbon black variables. Studies on hysteresis at constant strain (E″) have indicated that the important black variables, in diminishing order of significance, are loading, structure (intraunit occlusion and anisometry), unit size, unit size distribution, and surface activity. For hysteresis at constant energy (resilience), the most important black variables appear to be black loading, unit size, unit size distribution, surface activity, and structure. In terms of tread wear resistance (moderate wear rates with SBR-BR), a somewhat different pattern of carbon black variables is apparent. At constant loading, the most important black properties appear to be specific surface area, surface activity, structure, and unit size distribution. At any given tread wear-surface area level, hysteresis can be lowered by broadening the unit size distribution and increasing the surface activity of the black.

The Chemistry of Carbon Black and Reinforcement

1957 ◽  
Vol 30 (5) ◽  
pp. 1400-1483 ◽  
Author(s):  
Merton L. Studebaker
Keyword(s):  
Catalytic Activity ◽  
Hydrogen Sulfide ◽  
Double Bond ◽  
Carbon Black ◽  
Chemical Reactivity ◽  
Chemical Properties ◽  
Hydrogen Atoms ◽  
Methylene Carbon Atom ◽  
Chemical Combination ◽  
Black Surface

Abstract In this discussion, we have indicated that carbon blacks display both chemical and catalytic activity which appear to be sufficient to radically alter the chemistry of vulcanization. Much of the chemical reactivity results in removal of molecules or reactive intermediates which might otherwise produce crosslinks. However, in some cases the chemical reactivity seems to be associated with catalytic activity. When carbon black is heated with rubber, as during hot mixing or during cure, the following types of reaction are considered possible: a) Alkylation (in a broad sense) of carbon black by rubber molecules. This would be a case of alkylation of an aromatic material by an olefin. b) Isomerization of the double bond structure of rubber molecules resulting in conjugation. c) Chemisorption of rubber molecules with dissociation—dehydrogenation—and chemical combination of the rubber-free radicals so formed with the carbon black surface or with themselves, a type of polymerization. Insofar as addition to carbon black is involved, the results of a) and c) are, for practical purposes, identical. During vulcanization, the action of carbon black will be dependent upon the nature of the rubber, the nature of the curing system and the presence of other compounding ingredients. During cure, carbon black may be considered to act in some, if not all, of the following ways: 1) As a catalyst for dehydrogenation by sulfur. 2) As a catalyst for the oxidation of —SH intermediates to —S—S— crosslinks. 3) As a catalyst to convert polysulfides to disulfides or prevent polysulfide formation. (This particular activity has not been demonstrated ; it is suggested in this review only as a possibility.) 4) As a catalyst in activating accelerators by breaking —S—S— linkages, as in TMTD, —S—(S)x—S— linkages in the MBT polysulfide product of Dogadkin and Tutorskii˘, —S—N— linkages in Santocure, NOBS Special, etc. 5) As a catalyst for hydrogen sulfide formation (associated with 1, above) which is apparently necessary, at least under some conditions, to activate curing systems. 6) As a catalyst in the presence of oxidizing agents for the conversion of hydrogen sulfide (and sulfanes) to sulfur. 7) As a catalyst which promotes a type of decomposition of TMTD, and no doubt other systems, in a manner which is efficient in producing crosslinks. In the initial phases of vulcanization, its activity as a dehydrogenation catalyst is of considerable importance. This probably involves chemisorption with dissociation of α-methylene hydrogen atoms. This activity directs the chemical reactions of vulcanization to the α-methylene carbon atom and may lead directly to coupling rather than addition reactions at the double bond. After the dehydrogenation step, polymerization reactions, as described in this issue by Craig, should also be considered as possible. Agglomeration of carbon black particles plus high crosslink density seems to be strongly indicated. This would certainly result in heterogeneous crosslink distribution which would manifest itself in physical properties and possibly in some “chemical properties” of the reinforced vulcanizates.

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