Mixing mechanism during NR-, SBR-, IIR-, and EPR-carbon black (HAF) compounding

Morphological changes of carbon black agglomerates were observed for NR-, SBR-, and IIR-HAF-process oil compounds during mixing in an internal mixer, using an optical microscope with a transmission method. For the convenience of observation, the recipe was designated as containing only a lesser amount of HAF, 10 phr. Those observations were carried out over the minimum mixing times. The changes of the NR compounds are very similar to those of the EPR compounds shown previously. It suggests the onion peeling mechanism might control the dispersion stage of the NR mixing. Although some agglomerates indicate the existence of that mechanism, it was not evident whether or not the mechanism was dominant in the other rubber systems. The process oil influences little the mechanism as understood by the investigation on the oilless systems of NR and EPR. Photomicrographs. 11 ref.--AA