Research Of Mixing Performance And Design For Elongational Flow And High-Dispersion Mixing Twin-Screw Element

Distributive mixing and dispersive mixing are two kinds of mixing types in polymer processing. Two kinds of elongational and high-dispersion mixing twin-screw element were designed on the basis of dispersive mixing mechanism and meshing theory of co-rotating twin screw extruder.Flow field of new type twin screw elements were simulated by polyflow. Pressure field, weighted average shear stress and cumulated maximum tensile rate distribution were obtained by the simulation of high-dispersion mixing elements. Pressure field and cumulated maximum tensile rate distribution were obtained by the simulation analysis of elongational elements. The results showed that six-tip sawtooth-shaped element had the best mixing performance. From 30°to 90°, with the increase of staggering angle of kneading-like disc, the mixing performance weakened, whereas the mixing performance enhanced from 90°to 150°. Four-tip non-intermeshing elongational element had the best tensile performance. Five-cone elongational element had better tensile performance than other screw configurations.The mixing performance for elongational and high-dispersion mixing twin-screw elements was verified by experiments. The results showed that the mixing performance of sawtooth-shaped twin screw element was better than that of common twin-screw element and kneading block except the staggering angle of 150°. The mixing performance for three kinds of staggering angle of kneading-like disc was better than that of the corresponding staggering angle of kneading block. The homogeneity of particle size distribution for sawtooth-shaped twin screw element and kneading-like disc was better than that of common twin-screw element and kneading disc. The tensile performance of non-intermeshing elongational element and cone elongational element was better than S type screw element. The experimental data were in good agreements with the simulation results.