Differences in Behavior Between Internal Mixers with Tangential Rotors and Intermeshing Rotors, as Influenced by the Molecular Structure of EPDM

An interpretation of the results of the present studies in terms of flow regimes, on the analogy of the various regimes in the behavior of pure rubber on a two-roll mill, seems obvious. The analogy of the mixing behavior of ethylene-propylene copolymer rubbers with different molecular structures in internal mixers and their behavior on a two-roll mill, applies to tangential as well as to intermeshing type mixers. A tangential rotor mixer would require a second mixing step, either in the batch mixer again or on a two-roll mill to include accelerators and vulcanization ingredients at a lower temperature than obtained in the first mixing step. The shift of the carbon black dispersion to a lower-temperature regime, going from tangential to intermeshing rotor mixers, can be explained in terms of Tokita regimes in relation to the differences in clearances between rotors and mixer walls for both type mixers.