The effect of compound processing on filler flocculation

The effect of the mastication of carbon black-filled NR masterbatches prepa red by liquid phase mixing/coagulation process and dry mixing process on dy namic properties of uncured compounds and vulcanizates were investigated. I ntensive mastication leads to lower a G' and G " along with a depressed str ain dependence of these moduli, indicating an improved micro-dispersion in the uncured compounds. It was also found that in contrast to uncured compou nds, a higher G' and G " and a more developed Payne effect, i. e., a poorer micro-dispersion, were observed for the vulcanizates prepared with the int ensively masticated masterbatches. This phenomenon was attributed to the fl occulation or agglomeration of carbon black aggregates during vulcanization . The flocculation rate is substantially increased upon mastication which i s related to the reduction of the molecular weight of the polymer matrix an d bound rubber content, resulting in the decreased viscosity of the compoun ds.