Types of carbon black

Carbon black might be described as an ideal universal additive it can provide pigmentation, reinforcement, ultraviolet shielding, and anti-static properties -but always provided that the final colour is black. It is used in several different forms, produced by different production processes for its various applications. There are about 100 different grades today, each of which Is matched to an individual application. In thermosetting resins, most carbon blacks tend to inhibit cure and should be avoided. 

The major user of black is the rubber industry, particularly for tyres, where addition of carbon black contributes to reinforcement and resistance to tearing, abrasion, flex, and fatigue. In the USA it is estimated that a little less than 0.5 lb (0.25 kg) of black on average is used for every 1 lb of rubber used. Plastics are the largest and fastest-growing non-elastomer use for carbon black. 

A number of production processes are used, of which furnace black is by far the dominant process, accounting now for 97-98% of total world production (of approximately 6 million tonnes a year). 

Production processes come under two main classifications  

1 Thermal oxidative decomposition processes Furnace black is the newest but also overwhelmingly the predominant process. Liquid feedstock is atomized, sprayed into a flame inside a ceramic-lined furnace, and then quenched, cooled, and filtered. The process offers technical and economic advantages, with the facility to produce a wide range of types, with adjustment of particle size and specific surface area. Particle aggregation can also be controlled by addition of very small amounts of an alkali metal salt. Particle size ranges from 10 to 100 pm. Black made by this process has a very low bulk density and is difficult to handle in this form. It is therefore pelletized or further densified. Wet-pelleting enables carbon black to be converted with water 

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Special types of carbon black may be incorporated in latexes used for backing of carpets to enhance their conductivity. Nylon carpets backed with such conductive latex offer excellent antistatic properties even at 10% rh (110). 

Carbon black consists of elemental carbon with variable amounts of volatile matter and ash. There are several types of carbon blacks, and their characteristics depend on the particle size, which is mainly a function of the production method. 

The surface structure has a strong influence on the corrosion rate of carbon in both acid and alkaline electrolytes. Studies by Kinoshita [33] clearly showed that the specific corrosion rate mAcm"2 of carbon black in 96 wt% H3P04 at 160 °C was affected by heat treatment. A similar trend in the corrosion rate in alkaline electrolyte was observed by Ross [30c], as shown in Fig. 4. It is evident that the corrosion rates of the nongraphitized carbons are higher than those of the corresponding graphitized carbons. Their study further indicated that some types of carbon blacks (e.g., semi... 

In electrocatalysis, the activated carbons, glassy carbon, and carbon black are the transitional forms used. Carbon black is the product of incomplete combustion or decomposition of organic compounds. The shape of its particles is close to spherical. They contain several carbon atom lattice fragments arranged without order. Various types of carbon black serve as substrates for metal catalysts, the properties of the carbon blacks themselves having a strong elfect on the catalytic activity of the combined catalysts thus obtained. 

Rubber which is deliberately rendered electrically conductive by the inclusion in the unvulcanised mix of certain types of carbon black. Conductive rubber for use in, e.g., aircraft tyres has a resistivity below about 105 to 107 ohm-cm. The changeover from the use of channel blacks to oil-based furnace blacks has conferred a degree of conductivity (sometimes unwanted) on many black rubber products, and it should no longer be assumed that any black rubber is a good electrical insulator. See Antistatic Rubber. 

A type of carbon black produced by burning natural gas or oil in a large furnace with a supply of air much lower than that required for complete combustion. The main types are super abrasion (SAF), intermediate super abrasion (TSAF), high abrasion (HAF), fast extrusion (FEF), general purpose (GPF), conductive (CF) and semireinforcing (SRF). 

These types of carbon blacks are characferized by particularly high surface area (50-1,500 m g i)-fo-volume rafios and have much lower impurity levels. However, despite the many black products available, only a small number have been reported for fuel cell use (XC72, BP2000, Ketjen EC300J). Currently,... 

Carbon black Finely divided carbon made by incomplete combustion or decomposition of natural gas or petroleum-based oils in different types of equipment. According to the process and raw material used, it can be furnace (e.g., HAF), thermal (e.g., MT), or channel carbon black (e.g., EPC), each having different characteristics, such as particle size, structure, and morphology. The addition of different types of carbon blacks to rubber compounds results in different processing behavior and vulcanizate properties. 

On the other hand, the term carbon black is used for a group of well-defined, industrially manufactured products. They are produced under carefully controlled conditions. The physical and chemical properties of each type of carbon black are kept within narrow specifications. Carbon black is one form of highly dispersed elemental carbon with extremely small particles. Depending on the production process and the raw materials, carbon black also contains chemically bound hydrogen, oxygen, nitrogen, and sulfur. 

Today at least 35 different types of carbon black are used as fillers in rubber, and about 80 types of carbon black are used in pigments or special applications. The total world production in 1994 was 6 x 1061. More than 90% of the carbon black was produced for the use in the rubber industry. 

Density. Density measurements using the helium displacement method yield values between 1.8 and 2.1 g/cm3 for different types of carbon black. A mean density value of 1.86 g/cm3 is commonly used for the calculation of electron microscopic surface areas. Graphitization raises the density to 2.18 g/cm3. The lower density with respect to graphite (2.266 g/cm3) is due to slightly greater layer distances. 

In the past decades the rapidly expanding automobile industry required increasing numbers of tires with various characteristics. This led not only to the development of new rubber grades, but also to the development of new carbon blacks required by the increasingly refined application processes and to the development of a new and better manufacturing process, the furnace black process. Unlike the old channel black process, this process allows the production of nearly all types of carbon black required by the rubber industry. It also meets the high economic and ecological requirements of our times. 

Other pigment blacks and the rubber blacks are compacted by granulation. Two processes are used dry and wet pelletization. Dry pelletization is a simple, energysaving method, but it does not work with all types of carbon black. It is mainly used for color blacks. Dry pelletization is carried out in rotating drums, where the powdery carbon black rolls to form small spheres. 

Several gas black apparatus are combined to form one production unit. The whole group is fed by one oil vaporizer. The production rate and the yield of an apparatus depend on the type of carbon black produced. For a typical RCC black, the production rate is 7-9 kg/h and the yield is 60%. The yield for high-quality color blacks is considerably lower (10-30%). 

The most important types of carbon black, some typical characteristics, and the principal applications are summarized in Tables 30 and 31. A general overview of the most important application fields is given in Figure 60. 

Differences in the types of carbon black used in the oil field service lead to the seal explosive decompression problems. The molecular weight of the base rubber also is very critical. 

Phillips Petroleum Co Stow, Ohio, Bulletins and Reports on various types of Carbon Blacks. 

The first is an EPDM fraction which is loosely bound to the carbon black due to adsorption interactions. This loosely bound rubber has numerous adsorption network junctions, similar to those in bound rubber. The second EPDM fraction, consisting of extractable rubber, contains a relatively small number of adsorption network junctions and can apparently be extracted from the compounds. The fraction of loosely bound EPDM chains determined with the aid of NMR increases with an increase in the maximum possible EPDM-carbon black contact area per unit volume of the elastomer, regardless the type of carbon black used, and is relatively close to the content of bound rubber [62]. 

In spite of the high concentration of carbon black particles the only observable effect of carbon black is a slight broadening of the resonance of Xe absorbed in EPDM at 205 ppm. The temperature dependence of this shift and the line width of the 205 ppm line are slightly dependent on the presence and the type of carbon black. The temperature dependence is shown in Figure 12.15 at lower temperatures (-33 °C), the sample with the largest carbon black particles (EPDM/N550) has the smallest chemical shift. 

Figure 12.19 The chemical shifts of 129Xe in carbon black filled EPDM as a function of the type of carbon black and the volume fraction of the carbon black in the material...

PEF treatment of carbon blacks. Due to their important specific surface areas, that range from a few m2/g to several thousands m2/g, carbon blacks react thoroughly in PEF conditions. The reactivity of various types of carbon blacks with F2-gas and other fluorinated reagents has been recently investigated by G. Nanse et al. [101-103],... 

Six types of carbon black are produced worldwide acetylene black, channel black, furnace black, gas black, lamp black and thermal black. Specific physical and chemical properties of a carbon black grade are summarized on its material safety data sheet and the suppliers product technical bulletin. 

The Huels-electric-arc process was the only large-scale process using plasma reactions where large quantities of carbon black were produced as a by-product in the production of acetylene. However, this type of carbon black is no longer used as a pigment... 

The last Issue to be dealt with Is the apparent irreversibility of the adsorption. One quite often encounters the opinion, especially In the older literature, that polymer adsorption would be an Irreversible phenomenon. These ideas are based on the hysteresis found In the adsorption isotherms desorption Isotherms (obtained by dilution with solvent) do not coincide with adsorption Isotherms (obtained by adding more polymer at given amount of solvent). Qualitatively, this was already discussed in sec. 5.3d. An experimental example Is given in fig. 5.31, for the adsorption of a polydisperse rubber from heptane on two types of carbon black (differing In specific surface area) ). The desorption Isotherms are found to He considerably above the adsorption Isotherms, the extent of desorption being very small. 

Figure 5.31. Adsorption-desorption hysteresis as observed for rubber adsorbing from n-hexane on to two different types of carbon black. Arrows indicate ascending (increasing Cp) and descending (decreasing Cp) branches. Redrawn from ref.

In rubber systems containing carbon black, flocculation may cause substantial changes in mechanical properties. Flocculation in these systems counteracts filler dispersion. Carbon black flocculation occurs in filled rubber stock during storage or during vulcanization in the absence of shear. " Temperature is the important kinetic factor which affects the flocculation rate (Figure 5.19). In addition to temperature and time, flocculation depends on the type of carbon black and its concentration. 

Figure 8.38. Abrasion loss of SBR containing different types of carbon black vs. interaggregate distance. [Adapted, by permission, from Patel A C, Kaut. u. Gummi Kunst., No.8, 1994, 556-70. ]...

The concentration of carbon black is important for both UV protection and opacity (required to prevent the growth of weeds). The amount of carbon black required for a certain level of opacity depends on the film thickness. The same volume of carbon black per unit area must be maintained in the film as the film thickness is reduced in order to retain the same degree of opacity. For a 30 pm thick film this concentration varies between 4 and 9 wt% depending on the type of carbon black used. 

Choosing carbon black as a filler for fibers has many implications. Figure 19.18 shows the effect of carbon black loading on viscosity in PET. Viscosity depends on the type of carbon black. A reduction of 50% viscosity can be attained at the same carbon black concentration simply by change to another grade of carbon black. Moisture absorption, which affects the drying time, can be substantially reduced (by about 50%) by the selection of the appropriate carbon black." Tiber color and tone are affected by the carbon black type and by the method of its dispersion. 

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