SURFACE-ENERGY OF FILLERS AND ITS EFFECT ON RUBBER REINFORCEMENT .1.

This paper studies the influence of different filler loadings of a ran ge of commercially available carbon blacks, a precipitated silica and its hexadecyltriethoxy-silane-modified counterpart on the hysteresis p roperties of standard SBR and NR compounds using E' and tan delta as c riteria for the evaluation. The study of the dynamic moduls E' shows t hat the modified Guth-Gold equation loses its validity beyond certain levels of filler loading. This is caused by filler networking which ca n be quantified by S(f). The parameter S(f) can be defined chromatogra phically and is representative of the ratio between the dispersive and specific components of filler surface energy. The investigation of ta n delta for carbon blacks shows that tan delta is primarily dependent on filler networking. Since the values for S(f) of all carbon blacks i nvestigated are similar, the distance between the carbon black aggrega tes is the main parameter determining tan delta. The comparison of car bon blacks and silicas at constant crosslink density shows that the si lica yields higher values for E' and lower values for tan delta. This is related to the different surface characteristics of the two fillers .