Carbon black chemical properties

Properties. The mechanical properties of E-SBR vulcanizates depend on the type and level of filler in the compound. Unfilled gum vulcanizates have very poor tensile strength and ultimate elongation, because the rubber lacks self reinforcing of the type found NR rubber vulcanizates, i.e., strain-induced crystallization. This inadequacy is offset by the addition of reinforcing fillers, i.e., carbon black or chemically coupled silica. At optimum loadings with reinforcing carbon black, mechanical properties similar to those of NR can be achieved. However, NR compounds exceed SBR compounds in tear strength because of NR s strain-induced crystallization. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

Color Concentrates. Color concentrates have become the method of choice to incorporate colorants into resins. Color concentrates have high ratios of colorant to a compatible vehicle. The colorant may be added at 70% colorant to 30% vehicle in a titanium dioxide mixture whereas the ratio may be 15% colorant to 85% vehicle in a carbon black mixture. The amount of colorant that can be added is dependent on the surface area and the oil absorption of the colorant and the wetting abiHty of the vehicle. The normal goal is to get as much colorant in the concentrate as possible to obtain the greatest money value for the product. Furthermore, less added vehicle minimizes the effect on the physical or chemical properties of the resin system. 

The studies by Biermann et al. [28] indicate that the carbon blacks used as the conductive matrix in Leclanche cells remain chemically inert, that is, they do not undergo oxidation during storage or discharge of the cell. However, Caudle et al. [29] found evidence that the ion-exchange properties of carbon black, which exist because of the presence of surface redox groups, are responsible for electrochemical interactions with Mn02. The extent of MnO, reduction to MnOOH depends on the carbon black (i.e., furnace black > acetylene black). 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

Chemicals like polyorthoaminophenol, diphenylamine in small amounts have been found to decrease the yield of cross-linking [388]. The tensile strength of the carbon black-filled polychloroprene compounds has been found to be comparable to the conventional thermally cured one. The physical properties [389] have been observed to improve on adding cross-linking promoters like A,A -hexamethylene-bis-methacrylamide into the polymer matrix. 

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

Ill-defined carbon materials that provide a distinct nanostructure, such as spherical particles in the case of soot and carbon black, or hexagonally ordered cylindrical pores in the case of ordered mesoporous carbons, are not discussed here. Surface chemical, thus catalytic properties of these material are closer to carbon black or activated carbon [13], which is frequently reviewed [2-4]. Here, the higher degree of sp3 hybridization often results in a higher reactivity, however, at lower selectivity, as compared to nanocarbons exposing large basal plane fractions of the overall surface. 

There are four allotropic forms of manganese, which means each of its allotropes has a different crystal form and molecular structure. Therefore, each allotrope exhibits different chemical and physical properties (see the forms of carbon—diamond, carbon black, and graphite). The alpha (a) allotrope is stable at room temperature whereas the gamma (y) form is soft, bendable, and easy to cut. The delta A allotrope exists only at temperatures above 1,100°C. As a pure metal, it cannot be worked into different shapes because it is too brittle. Manganese is responsible for the color in amethyst crystals and is used to make amethyst-colored glass. 

Most chemical properties of technetium are similar to those of rhenium. The metal exhibits several oxidation states, the most stable being the hep-tavalent, Tc +. The metal forms two oxides the black dioxide Tc02 and the heptoxide TC2O7. At ambient temperature in the presence of moisture, a thin layer of dioxide, Tc02, covers the metal surface. The metal burns in fluorine to form two fluorides, the penta- and hexafluorides, TcFs and TcFe. Binary compounds also are obtained with other nonmetaUic elements. It combines with sulfur and carbon at high temperatures forming technetium disulfide and carbide, TcS2 and TcC, respectively. 

The enormous importance of carbon in such diverse fields as inorganic and organic chemistry and biology is well known however, only the aspects of carbon relevant to catalysis will be described here. The main topics we are concerned with are porous activated carbons, carbon black as catalyst supports and forms of coking. Carbon is also currently used as storage for natural gas and to clean up radioactive contamination. Carbon is available at low cost and a vast literature exists on its uses. Coal-derived carbon is made from biomass, wood or fossil plants and its microstructure differs from carbon made from industrial coke. Activated carbons are synthesized by thermal activation or by chemical activation to provide desirable properties like high surface area. 

---