As one of key factors that determine the quality of products, the homogenization of polymer melt is closely dependent on the mixing of polymers. The mixing of polymer melt in the homogenizing section by a single screw with torsion elements was analyzed with the computational fluid dynamics (CFD) simulation. The simulation results reveal that screws with such torsion elements arranged in a decentralized form have smaller segregation scale, distribution index and higher mixing efficiency, compared with the conventional screw. The decentralized arrangement is more effective for mixing than the centralized distribution. The rotational flow induced by the torsion elements can significantly enhance the mass transfer process and improve mixing and plasticizing. Compared with those in conventional screw, the distributions of temperature and viscosity are more uniform at the outlet of torsion screws, which also made the torsion element generally more effective and efficient for mixing and plasticizing.

Keywords: torsion element, distributive mixing, dispersive mixing, mixing efficiency, plasticizing quality