CHARACTERIZATION OF THE MORPHOLOGY OF RUBBER GRADE CARBON-BLACKS BY THERMOPOROMETRY

The intra-aggregate void size distribution (VSD) and void volume, and the fractal dimension D of rubber grade carbon blacks dispersed in water, were measured by thermoporometry. It is shown that the value of R(max) corresponding to the maximum of the VSD curve is proportional to the DBP volume and to the size R(s) of the primary particles constituting the aggregates. It follows that the ratio R(max)/R(s) can be considered as a morphological parameter leading, with the value of the fractal dimension D, to the characterization of the carbon black aggregates. The intra-aggregate void volume, measured by thermoporometry, is compared with that of the occluded volume, calculated by Medalia. It appears that the experimental and calculated values agree fairly well for carbon blacks exhibiting small aggregates, but that the occluded volumes, calculated for larger aggregates, are overestimated. From the determination of the ratio f/phi, between the value of the volume fraction of carbon black f and the volume fraction of aggregates-phi, and from the comparison with its theoretical value (R(max)/R(s))D-3, it is shown that the behavior of the systems, with increasing f, is mainly controlled by the interpenetration of the aggregates.