Aggregates Medalia, occluded rubber

The (pc value represents the actual size of filler aggregates in the mix it includes, naturally, the filler object itself plus a significant volume of polymer that is shielded from deformation by aggregate tortuosity. This part of the polymer that will not be deformed is usually called occluded rubber (Kraus, 1970 Medalia, 1970 1974). 

Considering a highly irregular shape and a presence of occluded rubber in cavities of the carbon black aggregates, Medalia [16] introduced effective volume to represent filler concentration. His effective volume fraction, V, replaces the real volume fraction, v, in Equation 8.8. The effective volume fraction, V, is not an adjustable parameter, but calculated from the DBP absorption [17] (see also Chapter 9). The shear storage modulus, G, was measured at 25 °C and 0.25 Hz, with 20 phr of carbon black loading where G was practically independent of the strain amplitude. With 12 carbon blacks of varying particle size and structure, the calculated, G, from the equation. 

In relation with the void volume in carbon black aggregates, Medalia introduced the (debated) concept of "occluded rubber," defined as the fraction of... 

A.I. Medalia. Effective degree of immobilization of rubber occluded within carbon black aggregates. Rubb. Chem. TechnoL, 45,1171-1194,1972. 

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