SURFACE-ENERGY OF FILLERS AND ITS EFFECT ON RUBBER REINFORCEMENT .2.

This paper studies the influence of different filler loadings of a range of commercially available carbon blacks, a precipitated silica and its hexadecyltriethoxy-silane-modified counterpart on the hysteresis properties of standard SBR and NR compounds using E' and tan delta as criteria for the evaluation. The study of the dynamic moduls E' shows that the modified Guth-Gold equation loses its validity beyond certain levels of filler loading. This is caused by filler networking which can be quantified by S-f. The parameter S-f can be defined chromatographically and is representative of the ratio between the dispersive and specific components of filler surface energy. The investigation of tan delta for carbon blacks shows that tan delta is primarily dependent on filler networking. Since the values for Si of all carbon blacks investigated are similar, the distance between the carbon black aggregates is the main parameter determining tan delta. The comparision of carbon blacks and silicas at constant crosslink density shows that the silica yields higher values for E' and lower values for tan delta. This is related to the different surface characteristics of the two fillers.