An investigation on the scorch properties of rubber compounds in mixing at high shear rates

摘要

The mixing scorch time (t_s) of six kinds of common rubbers (NR, BR, SBR, NBR, CR, EPDM) were studied in a wide temperature range (100～140℃) and rotor speed range (30～70 r · min~(-1)) using a Brabender torque rheometer, which can supply the rubber compounds a high shear rates processing condition. After compared with the Mooney scorch time (t_5), it is shown that Mooney scorch time can't predict the mixing scorch 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 mixing scorch time very well. An explanation that can explain the model well was given based on the reactivity of rubber chain segments: the increasing reactivity of rubber chain segment under high shear rate is the main reason that the scorch time of rubber compounds shortens in high shear rate internal mixing.