Characterization of the surface activity of furnace blacks - I. Determination of the surface roughness by static gas adsorption monolayer regime

For a deeper understanding of reinforcement mechanisms of elastomers by fil lers, the geometrical surface roughness of carbon blacks was characterised by a fractal concept. The adsorption isotherms of different gases (argon, n itrogen, ethylene, ethane, propane and butane) were analysed by the yardsti ck-method which yields a characteristic scaling behavior between the BET-mo nolayer and the cross section of gases of different size. According to this study the surface can be considered to be rough with a surface fractal dim ension of D-s approximate to 2,6. Hence, the variable reinforcement behavio r of different carbon black types cannot be related to different surface ro ughness. Graphitization of furnace blacks leads to a reduction of surface r oughness with a surface fractal dimension of D-s approximate to 2,3. This c orrelates with a reduced BET-surface area.