RELATIONSHIPS BETWEEN STATE-OF-MIX AND EXTRUDATE MELT FRACTURE OF A CARBON-BLACK FILLED SBR-COMPOUND

Melt fracture of batches of a styrene-butadiene (SBR1502) rubber compo und filled with 30 phr N330 carbon black produced at various mixing ti mes was investigated in terms of surface texture wavelength, As mixing time is reduced the wavelength and the severity of surface disruption increases, The wavelength is controlled strongly by the effective vol ume fraction of filler or state-of-mix and by shear rate, A mechanism for melt fracture of the SBR compound has been proposed, based on aver age energy at the extrudate surface. In order to maintain wall slip an d fracture at the extrudate surface, the average energy at the extruda te surface must be higher than the critical energy at the extrudate su rface.