Mixing Characterization Based on Drag Flow: Phase III—Effect of Kneading Blocks on a Visco-elastic System

Many new product properties are being achieved by blending and alloying homopolymers or copolymers with a variety of additives, rather than by the creation of a new polymer. This paper examines the effect of screw design and operating conditions on the final product properties for the blending of solid filler into a visco-elastic matrix. To accomplish this, a simple screw design is used and the spacing is changed between the kneading blocks. The spacing for the screw profiles varies from 0 mm to 90 mm in increments of 30 mm. The material used is silica mixed into polyisoprene in a 43 mm co-rotating twin screw extruder. The polymer Mooney viscosity is higher in the 30 mm profile than the other profiles. The average molecular weight for the 30 mm tended to be the least for all of the profiles. In addition, the ribbon die on the end of the extruder acted as another mixing element and therefore it also had an effect on both viscosity and the molecular weight when it was taken off. The effect is more pronounced for lower drag flow rates than for higher.