Mixing characterization based on drag flow: Phase III - Effect of kneadingblocks on a visco-elastic system

Many new product properties are being achieved by blending and alloying hom opolymers or copolymers with a variety of additives, rather than by the cre ation of a new polymer. This paper examines the effect of screw design and operating conditions on the final product properties for the blending of so lid 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 3 0 mm. The material used is silica mixed into polyisoprene in a 43 mm co-rot ating twin screw extruder. The polymer Mooney viscosity is higher in the 30 mm profile than the other profiles. The average molecular weight for the 3 0 mm tended to be the least for all or the the profiles. In addition, the r ibbon die on the end of the extruder acted as another mixing element and th erefore it also had an effect on both viscosity and the molecular weight wh en it was taken off. The effect is more pronounced for lower drag flow rate s than for higher.