Bound Rubber and Elastomer-Filler Interaction

Abstract

Abstract The statistical theory of bound rubber and the polymer-filler gel formation theory are shown to offer a satisfactory quantitative description of a set of experimental bound-rubber data recently obtained by Wolff, Wang, Tan (Rubber Chem. Technol. 66, 163 (1993)) on SBR compounds filled with 17 furnace blacks covering the whole range of rubber grades. The observed decrease of bound-rubber content per unit of interfacial area with increasing loading and/or specific surface area of carbon black is explained by the theory as being due to the statistical nature of the adsorption process. A correlation was found to exist between specific surface activity of filler D (adjustable parameter of the theory, number of active sites per unit surface area) and filler structure, the latter being characterized by the difference between DBP absorption and crushed DBP absorption. Also, D was found to increase with loading of a high-structure black. The two effects are ascribed to filler aggregates breakdown during mixing, which leads to a new active surface formation for polymer bonding.