BOUND RUBBER AND ELASTOMER-FILLER INTERACTION

The statistical theory of bound rubber and the polymer-filler gel form ation theory are shown to offer a satisfactory quantitative descriptio n of a set of experimental bound-rubber data recently obtained by Wolf f, Wang, Tan (RUBBER CHEM. TECHNOL. 66, 163 (1993)) on SBR compounds f illed with 17 furnace blacks covering the whole range of rubber grades . The observed decrease of bound-rubber content per unit of interfacia l area with increasing loading and/or specific surface area of carbon black is explained by the theory as being due to the statistical natur e of the adsorption process. A correlation was found to exist between specific surface activity of filler D (adjustable parameter of the the ory, number of active sites per unit surface area) and filler structur e, the latter being characterized by the difference between DBP absorp tion and crushed DBP absorption. Also, D was found to increase with lo ading of a high-structure black. The two effects are ascribed to fille r aggregates breakdown during mixing, which leads to a new active surf ace formation for polymer bonding.