Carbon black aggregate and

Small-angle X-ray scattering (SAXS) data have made it possible to deduce the localisation of organic additives (pigments) in the bulk of isotactic polypropylene (iPP) [344]. This work has confirmed that the additives are located in the amorphous phase, in spite of their crucial influence on the formation of the crystalline phase of iPP. SAXS has also been used to study the 3D structure of different carbon-black aggregates, and silica-filled SBR rubber compounds [345]. 

It was shown, on the one hand, that gum-filler interactions are associated with the immobilization of a certain amount of rubber on the surface or inside the carbon black aggregates, and, on the other hand, that the corresponding bound or occluded rubbers play important roles in the reinforcement process due either to a restriction of elastomer chain mobility in the vicinity of the filler or to an increase of the effective volume of the latter. What are now the effects exerted by a filler on the stress-strain behavior and the modulus of cured rubbers ... 

In Fig. 8, let A be a carbon black aggregate, and M an elastomer macromolecule attached to a point F in space. M contacts A at a point P along the molecule and a point S on the surface of A. The character of F does not concern us at the moment, and at this stage of the discussion, A is fixed relative to F. 

All of these approaches have focused upon increased interaction between the elastomer and carbon black compounding materials resulting in stabilized dispersion of individual carbon black aggregates and a reduction in interaggregate contacts. 

Fig.36. Variation in electrical conductivity (o) with molecular weight for polyethylene composites filled with 4% by volume carbon black, demonstrating the effects of orientation (I), degradation (II) and flow-induced segregation of carbon black aggregates (III). ( ) injection moulded (O) compression moulded (unoriented) [181]...

The latter can be of two types, either purely mechanical, and be associated with the occlusion of rubber into carbon black aggregates (occluded rubber), are more complex and involve physical and chemical interactions, they will then be related to bound rubber. 

Figure 10.10 Schematic representation of the physical network structure in a carbon-black-filled elastomer [62]. The symbol - indicates elastomer - carbon black adsorption junctions. The length scales in this figure and the EPDM/carbon black volume ratio are fictional. For simplicity, none of the contacting carbon black aggregates, which form agglomerates, have been included...

The room temperature 129Xe spectra of the three carbon blacks are shown in Figure 12.17 and, surprisingly, the line width of these Xe resonances is much smaller than that of Xe in the composites. Although it is known that magnetic impurities and susceptibility effects excessively broaden the 13C line width of carbon blacks, these effects clearly are not as serious for Xe adsorbed at the outer and inner surfaces of the carbon black aggregates [20]. 

The exponent df is denoted mass fractal dimension or simply fractal dimension. It characterizes the mass distribution in three dimensional space and can vary between lfractal analysis of furnace blacks was performed, e.g., by Herd et al. [108] or Gerspacher et al. [109, 110]. The solid volume Vp of primary aggregates is normally determined (ASTM 3849) from the cross-section area A and the perimeter P of the single carbon black aggregates by referring to a simple Euclidean relation [108] ... 

This behavior can be understood if a superimposed kinetic aggregation process of primary carbon black aggregates in the rubber matrix is considered that alters the local structure of the percolation network. A corresponding model for the percolation behavior of carbon black filled rubbers that includes kinetic aggregation effects is developed in [22], where the filler concentrations and c are replaced by effective concentrations. In a simplified approach, not considering dispersion effects, the effective filler concentration is given by ... 

In the case of carbon black as a filler, the ultimate tensile strength of a plastic compound results from interfacial effects between the carbon black and the resin. These interfacial effects are enhanced by the presence of a higher concentration of carbon black aggregates (higher loading) and by decreased aggregate size. 

Various manufacturing processes are employed for the production of different gi of carbon black (Medalia and Rivin, 1976). The most important is the oil fur process, in which petroleum residue is subjected to partial combustion and crac in a refractory furnace. Colloidal carbon is produced in the form of a hot smo] small globular particles, which on cooling undergo aggregation to give bran chain-like structures. 

The method is based on the premise that all interstices, known as void volumes, in the carbon black aggregates are filled with DBP. The surface of the carbon black is considered to be wetted and this new surface state is translated into a change in the torque required for the kneading machine. The DBP requirement thus allows conclusions on the degree of aggregation of individual carbon blacks. The rule the greater the DBP absorption, measured in ml g , the higher the carbon black structure. 

---