Study On The Structure Optimization And Mixing Properties Of Barrier Mixers Of Single Screw Extruder

Single screw extruder is the most widely used equipment in plastic industry. However, its weaker dispersive mixing ability limites its development and application because of the deeper channel and weaker shear force. As a kind of barrier mixer, triangle groove mixer can effectively promote the materials mixing, melting and plasticizing. Therefore, designing new type of efficient triangle groove mixers and studying on the mixing characteristics of barrier mixers has greater significance for improving the mixing effects of the single screw extruder and expanding its application.This paper designed and developed several kinds of triangle groove barrier mixers and studied on the factors that influence the flow field properties and mixing performance, such as triangle groove shape, shearing edge width, radial clearance and screw ratating speed. The three-dimension models of different triangle groove mixers were built by UG and the mixing characteristics were analyzed by the finite element software POLYFLOW through some related parameters such as pressure, velocity, temperature, shear rate, mixing index and average deagglomerating energy, etc. In addition, LLDPE/CaCO3 mixing experiments were used for the verification of numerical simulation analysis. Through numerical simulation and experimental analysis, the main conclusions are as follows:(1) The triangle groove shapes are a major factor affecting the flow field mixing characteristics. In the flow field of isosceles reverse triangle groove barrier mixer, the highest pressure of the melts and maximum differential pressure on both sides of the shear edges are higher than those of other shapes, and it also has higher temperature rise. The average particle size of CaCO3 aggregate is the smallest and the tensile strength is the highest because of its strong broken and abrasive action;(2) The shearing edge width and radial clearance also have important influence on the flow field mixing properties. The flow field of the triangle groove barrier mixer with shearing edge width 5mm and radial clearance 2mm has the biggest shear force and the best dispersive mixing action, which contributes to the smallest average particle size of CaCO3 aggregates and the best mixture tensile strength;(3) The appropriate increase of screw rotating speed can effectively enhance the mixing capacity of the triangle groove barrier mixer, reduce the average particle size of CaCO3 aggregates and improve the overall mixing performance of the mixer.