Study On Screw Configuration Processing Glass Fiber Reinforced Pp In Co-Rotating Twin Screw Extruder

While processing glass fiber reinforced polymer, different screw configurations can expert a great influence on mechanical behaviors of products.This article used CFD software POLYFLOW to simulate flow fields of three mixing elements including staggering angle of90°kneading block, FTX and VCR;3mixing combinations including staggering angle of60°kneading block+staggering angle of90°kneading block, FTX+staggering angle of90°kneading block and VCR which contains one right-lateral and two left-lateral elements. The result shows that among3mixing elements,VCR has lowest degree of shearing, a shortest resident time and a highest level of distribution mixing;the staggering angle of90°kneading block has a highest degree of shearing and a longest resident time; FTX has a quite weak shearing and the shortest resident time. Among3mixing combinations, the combination of staggering angle of60°kneading block and staggering angle of90°kneading block has the highest degree of shearing,the longest resident time and a quite strong distribution mixing; the VCR combination has the lowest degree of shearing, a rather short resident time and a quite strong distribution mixing; the combination of FTX and staggering angle of90°kneading block has a short resident time and the highest degree of distribution mixing.Experimental studys suggest that when traveling through mixing block,glass fibers are cut to about lmm under shearing in flow fields, the lengths are in the range of0.2mm to3mm. Higher the screw rotating speed is, stronger the shearing will be which would make glass fibers in products shorter, the mechanical properties of products would fall. Under the same condition of content, products produced with VCR configuration have longest glass fibers and best mechanical properties, products produced with kneading block configuration have shortest glass fibers and worst mechanical properties. When filled with glass fibers in20%mass content, tensile strength is improved and impact strength has an about20%increase.Theoretical and experimental studys suggest that when pass through flow fields of different elements and configurations, glass fibers suffered shearing in different levels.It is recommended to choose elements and configurations with low shear rate and shear force,a short and narrowly distributed resident time and a good distribution mixing effect to gain glass fibers in products with longer average length and mixed more equally, which are helpful to improve mechanical properties of products.