Premature vulcanization behaviors of rubber compounds under high shear rates processing

The premature vulcanization behaviors of six kinds of common rubber (NR, BR, SBR, NBR, CR, and EPDM) compounds containing curing agents were studied in a wide processing temperature range (100–140°C) and rotor speed range (30–70 rpm) using a Brabender torque rheometer, which can supply the rubber compounds a high shear rates processing condition. After comparison with the Mooney scorch time (MSt5), it is shown that Mooney scorch time cannot predict the premature vulcanization time under high shear rate processing. Six models were put forward based on the data obtained from the Brabender mixing head. The regression analysis and variance analysis showed that these models could simulate the premature vulcanization time very well. An explanation was given based on the reactivity and of rubber chain segments: the increasing reactivity and the impact probability of reactive rubber chain segment under high shear rate is the main reason of shorter scorch time of rubber compounds under high shear rate internal mixing. © 2006 Wiley Periodicals, Inc. JAppl PolymSci 102: 5414–5420, 2006