Experimental testing of the polymer–filler gel formation theory. Part I

Experimental data were obtained on the concentration dependence of the fraction of total filler–bound polymer, fraction of polymer in a coherent polymer–filler gel, and fraction of solvent‐dispersed filler particles in compounds of fume silica (Aerosil OX50) with natural rubber (NR) and styrene butadiene rubber (SBR). Predictions of the polymer–filler gel formation theory were tested and a good formal description of the data was obtained. The two adjustable parameters of the theory assume reasonable values. While A 0 is a characteristic of the filler interaction with polymer and has similar values in NR and SBR, the functionality f of the theoretically assumed filler particle acting as a polyfunctional crosslinker of polymer chains seems to depend on the polymer as well. Dimensions of the theoretical filler particle calculated from a comparison of experiment with theory are of the same order of magnitude but smaller than those of primary filler particles.