EXPERIMENTAL TESTING OF THE POLYMER-FILLER GEL FORMATION THEORY .1.

Experimental data were obtained on the concentration dependence of the fraction of total filler-bound polymer, fraction of polymer in a cohe rent polymer-filler gel, and fraction of solvent-dispersed filler part icles in compounds of fume silica (Aerosil OX50) with natural rubber ( NR) and styrene butadiene rubber (SBR). Predictions of the polymer-fil ler gel formation theory were tested and a good formal description of the data was obtained. The two adjustable parameters of the theory ass ume reasonable values. While A0 is a characteristic of the filler inte raction with polymer and has similar values in NR and SBR, the functio nality f of the theoretically assumed filler particle acting as a poly functional crosslinker of polymer chains seems to depend on the polyme r as well. Dimensions of the theoretical filler particle calculated fr om a comparison of experiment with theory are of the same order of mag nitude but smaller than those of primary filler particles. (C) 1994 Jo hn Wiley & Sons, Inc.