Hard carbon blacks

The ash content of furnace blacks is normally a few tenths of a percent but in some products may be as high as one percent. The chief sources of ash are the water used to quench the hot black from the reactors during manufacture and for wet pelletizing the black. The hardness of the water, and the amount used determines the ash content of the products. The ash consists principally of the salts and oxides of calcium, magnesium, and sodium and accounts for the basic pH (8—10) commonly found in furnace blacks. In some products potassium, in small amounts, is present in the ash content. Potassium salts are used in most carbon black manufacture to control stmcture and mbber vulcanizate modulus (22). The basic mineral salts and oxides have a slight accelerating effect on the vulcanization reaction in mbber. 

Iron. This is a specialty drier that is considered active at temperatures of about 130°C. For this reason iron 2-ethyIhexanoate [19583-54-1] is used in bake coatings that require maximum hardness. The principal drawback of using iron driers is that iron contributes a characteristic brownish red color to the coating and should only be used in dark pigmented systems. It has been reported that iron aids the dispersion of carbon black pigment and reduces the tendency for orange peel film defects (6). 

The Emerman model described in the previous section is hardly applicable to the carbon black-filled CCM as the black particles have sizes of hundreds angstrom and such a composite, compared with the molding channel size, may be considered as a homogeneous viscous fluid. Therefore, the polymer structure, crystallinity and orientation play an important role for such small particles. The above-given example of manufacture of the CCM demonstrates the importance of these factors being considered during processing of a composite material to and article with the desired electrical properties. 

The study of the mechanical properties of filled elastomer systems is a chaUenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward mle of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fiUers hke sihca and carbon black on the reinforcement of elastomers.In general, the strucmre-property relationships developed for filled elastomers have evolved into the foUowing major areas FiUer structure, hydrodynamic reinforcement, and interactions between fiUers and elastomers. 

Although many interface models have been given so far, they are too qualitative and we can hardly connect them to the mechanics and mechanism of carbon black reinforcement of rubbers. On the other hand, many kinds of theories have also been proposed to explain the phenomena, but most of them deal only with a part of the phenomena and they could not totally answer the above four questions. The author has proposed a new interface model and theory to understand the mechanics and mechanism of carbon black reinforcement of rubbers based on the finite element method (FEM) stress analysis of the filled system, in journals and a book. In the new model and theory, the importance of carbon gel (bound rubber) in carbon black reinforcement of rubbers is emphasized repeatedly. Actually, it is not too much to say that the existence of bound rubber and its changeable and deformable characters depending on the magnitude of extension are the essence of carbon black reinforcement of rubbers. 

The new interface model and the concept for the carbon black reinforcement proposed by the author fundamentally combine the structure of the carbon gel (bound mbber) with the mechanical behavior of the filled system, based on the stress analysis (FEM). As shown in Figure 18.6, the new model has a double-layer stmcture of bound rubber, consisting of the inner polymer layer of the glassy state (glassy hard or GH layer) and the outer polymer layer (sticky hard or SH layer). Molecular motion is strictly constrained in the GH layer and considerably constrained in the SH layer compared with unfilled rubber vulcanizate. Figure 18.7 is the more detailed representation to show molecular packing in both layers according to their molecular mobility estimated from the pulsed-NMR measurement. 

Now, we show the relation between the ratio of 8 to Tq, 8/ro and the volume fraction of carbon black (p in Table 18.1, when the diameter of the hard particle (including carbon black, the GH layer and a little more contribution from the cross-links at the surface of particle) is tq and the distance between the hard particles is 8. In the carbon black-filled rubber (ip g 0.23-0.25), the fact that the stress of the filled system is 10-15 times larger than that of the unfilled rubber as shown in Figure 18.1 indicates that more than 90% of the stress of the system is supported by the supernetwork and the remainder of the stress results from the matrix rubber. In the present calculation, however, we can ignore the contribution from the matrix mbber. 

Okumoto [89] has reported an analytical scheme (Scheme 2.8) for automotive rubber products (ENB-EPDM vulcanisates). For high-resolution PyGC analysis, organic additives are first removed from the rubber/(CB, inorganics) formulation. Carbon-black and inorganic material hardly interfere with pyrolysis. For the analysis of the additives the extracted soluble... 

The styrenic thermoplastic elastomers are the only type which are fully compounded in the manner of conventional elastomers. In this case, however, the addition of carbon black, or other fillers, does not give reinforcement. Additions of polystyrene, or high impact polystyrene, and oil are used to vary hardness and tear strength, and fillers can be used to cheapen the material. Other added polymers, e g., EVA, can be used to increase ozone resistance. These materials also require antioxidants for protection during processing and service life, and the poor UV stability restricts their use in outdoor applications. 

Carbon black is another of the carbon-intensive materials. It is formed from the burning of gaseous or liquid hydrocarbons under conditions where the amount of air is limited. Such burning favors soot formation, i.e., carbon black formation. It was produced by the Chinese over 1000 years ago. Today, it is produced in excess of 1.5 million tons annually in the United States. Furnace black is the most widely used carbon black. The particle size of this raw material is relatively large, about 0.08 mm. It is soft with a Mohs scale hardness of less than one. 

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