Rubbery matrix carbon black

It is suggested that the sites of interaction between carbon black and rubbery chains cause physical (adsorption) network junctions in the rubber matrix [20, 62] (Figure 10.10). 

The results obtained for unvulcanised EPDM and NR filled with carbon black provide convincing evidence that the physical network has a bimodal structure [62, 79]. Two types of EPDM chains and/or chain fragments with widely differing densities of EPDM-carbon black adsorption junctions are present in the rubbery matrix outside the EPDM-carbon black interface (tightly bound rubber) (Figure 10.11) [62],... 

By appropriate selection of the markers for stiffness and adhesion, it is possible to differentiate the rubbery matrix (low modulus, high adhesion) and the filler particles (high modulus, low adhesion). As shown in Fig. 3.66, elevations in the height image corresponds well with areas of higher stiffness and lower adhesion. The carbon black particles can be observed in a non-homogeneous distribution at the surface of this microtomed specimen. 

These properties determine how carbon black will be distributed within the blend. These properties are not those of the filler but are the essential properties of the matrix. The matrix thus has strong influence on particle distribution. SEM studies showed that high vinyl polybutadiene and styrene-butadiene copolymers had morphologically identical carbon black distribution. However, their mechanical properties were very different. NMR analysis indicated that the difference in mechanical behavior is related to the interaction and more precisely to the molecular motions in rubbery matrix. 

New generadon nano scale fillers are challenging the domination of traditional fillers such a as carbon blacks and silica in the rubbery industry. Nanoscaled fillers such as layered sihcates, carbon nanotubes, carbon nanofibers (CNFs), exfoliated graphite, spherical particles and Polyhedral oligomeric silsesquioxane (POSS), etc., dispersed as a reinforcing phase in a mbber matrix are emerging as a relatively new form of usefiil material. 

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