An innovative study to evaluate fillers, part 1: Carbon black and silica

The main components of a rubber compound, polymer and fillers, are evaluated jointly to characterize the reinforcing characteristic of carbon black and silica. A new concept has been developed around three filler parameters: (1) surface area, N(2)SA; (2) volume of the aggregate, VF; and (3) volume fraction of the filler in a compound, Phi(C). These parameters are associated with a decrease in the randomly oriented polymer chains from unity. This decrease is attributed to the interaction between surface chemistry and morphology of the filler. Two parameters are derived from the colloidal properties of the filler: total volume (phi(t)) and total surface area (Sigma(s)). The experimental data discuss dynamic and technological properties as a function of Sigma(s) and phi(t). The fillers involved in the study are carbon black and silica. Compound properties were obtained, at variable loading, in filled and unfilled S-SBR, E-SBR, EPDM and NR. The second part discusses rubber properties, at constant loading, of carbon black and silica. The concept was applied to create precise blends of carbon black and silica to reduce hysteresis and duplicate silica compound properties. The results demonstrate a very sensitive relationship between filler parameters Sigma(s) and phi(t) with compound properties.