Carbon black Particle aggregation

A minimum of 10 to 35 parts carbon black to 100 parts of mbber is required to obtain a resistivity in the order of 10 Q-cm. At that loading the carbon black particles, which have an average radius of 10 nm, form grapelike aggregates that provide continuous paths for the electrical current. Special purpose mbbers containing even more carbon black have resistances as low as 1 Q-cm (129). The electrical resistivity of mbber with carbon black is sensitive to strain history, probably because of temporary dismptions of the continuity of the carbon black aggregates. 

So far LII has only been applied for aerosol processes without the consideration of particles dispersed in liquids. First, investigations were carried out with re-dispersed carbon blacks. Besides furnace blacks (Printex A, G, 25, 35, and 55), various gas carbon black particles (FW 18, Colour Black SI60 and S170, Printex U and U140) were also considered. The particles were suspended in different liquids and dispersed by ultrasonic excitation. The stability of the suspension was recorded by measuring the aggregate size distribution (diffusion diameter) with DLS. Moreover, this was done before and after the LII measurements in order to control the stability of the particle suspension. To achieve LII... 

Both of these effects refer to a high surface activity and specific surface of the filler particles [26, 27, 47]. In view of a deeper understanding of such structure-property relationships of filled rubbers it is useful to consider the morphological and energetic surface structure of carbon black particles as well as the primary and secondary aggregate structure in rubber more closely-... 

In the case of carbon black, the aggregates are distributed in the matrix rather than individual particles, it is therefore important in some applications (e.g., conductive plastics) to evaluate the distance between these aggregates. It is now possible to measure these distances by atomic force microscopy coupled with straining device. There is a linear relationship between the parallel distance between aggregates dispersed in SBR and strain value. For 10 phr of N 234, the mean distance between aggregates varied in a range from 1.85 to 3.42 jm. For practical purposes, a modified equation [5.4] is used to determine the interaggregate distance ... 

Silica and carbon black form aggregates 10-100 times the size of the primary particles. Mesh size. 

High-temperature pyrolysis reactions of hydrocarbons are responsible for the production of PAH and solid carbon black particles, soot. This phenomenon is common in diffusion flames where, at high temperatures and without oxygen, hydrocarbon fuel aggregates follow pyrolysis and condensation paths with the formation of heavy aromatic structures. Many PAH s identified in aerosols have been found to be mutagenic and are certainly important soot precursors. This formation of carbonaceous particles has recently become one of the main topics in chemical reaction engineering, especially in the field of pyrolysis and combustion of hydrocarbon fuels. This interest rises from environmental concerns about PAH and soot particle emissions because of their dangerous impact on the human health (Oberdorster et al., 2004). 

With the ZSM-5/TMP zeolite prepared using the method 2 the presence of much broader mesopore distribution indicates that nucleation starts within the interparticle voids of aggregates of carbon black. As carbon black was impregnated with TEOS to approximately 20 % excess (compared to incipient wetness), standard zeolite crystals were formed and encapsulated the carbon matrix. The mesopore volume of the sample ZSM-5/IMP is larger than in the case of ZSM-5/10 and it attains 0.193 cm /g (Table 2). The mesopore size distribution of this sample is broader in comparison with that of the samples prepared by the secondary templating (Fig. 4). Therefore, we can assume that small clusters formed from a few carbon black particles were operative as mesopore template. 

Efforts to enhance the conductivity of transition metal oxide electrodes have included the preparation of composites of the oxide with a conductive material, such as carbon black. Traditional composite electrodes, however, are characterized by aggregation of the carbon black particles [23]. These aggregates are typically on the order of hundreds of nanometers in diameter and may occlude the oxide aerogel surface. Work to enhance the conductivity of the transition metal oxide... 

Figure 6.11 A schematic showing the distinction between carbon black particles and an aggregate.

The silica or carbon black particles used to reinforce commercial materials are seldom completely dispersed, - 391-393 as is assumed in the simulations described. The primary particles are generally aggregated. These aggregates are frequently clustered into less stable arrangements called agglomerates. ... 

Carbon-derived powders and particles comprise a family of synthetic materials, known under the generic term of carbon black, made by burning hydrocarbons in insufficient air. Carbon-black particles are aggregates of graphite microcrystals, each only a few unit cells in size and so small that they are generally not detectable by diffraction techniques. The physical properties of these materials are essentially determined by the nature and extent of their surface areas. 

Fig. 5.72 In bright field optical micrographs, carbon black particles appear as dense particles (A). Such particles can aggregate (B) and provide a locus of failure. Streaks in molded parts, due to poor mixing of the carbon black, are shown in sections of the molded specimens (C and D).

Fig. 5.73 Carbon black particles (arrows) are shown in a sectioned carbon black filled polymer (A) to be aggregates of smaller particles less than 0.1 iim in diameter. Interestingly, a black, multiphase pol)nner, shown in a TEM micrograph of an ultrathin section (B), has carbon black particles within the dispersed phase domains.

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