Evaluation On Mixing Performance Of The Co-Rorating Triple Screw Extruder

The triple intermeshing co-rotating extruder is a new type mixing equipment. The research on the mixing performance of triple screw extruder were limited to the Finite element simulation and anaylsis, but few studies on experiments of the triple-screw extruder. The mixing performance, devolatilization, energy consumption and mixing process of the triple screw extruder were systematicly discussed by the tons of experiments. The contents and conlusions are as follow:1. The dispersive mixing performance and distributive mixing performance, devolatilization of the triple screw extruder were studied by the comparetive analysis of the dispersed phase particle size, its distributive and the mechanical properties of the PP/EPDM and PP/nanoCaCO3 blends(two phase incompatible systems), nanoparticles reunion degree, bubble situation and apparent density of nanoCaCO3 masterbatch prepared by the triple screw extruder and two co-rotating twin screw extruders under the different mixing processes. The experimental results showed:The triple screw extruder have excellent dispersive mixing performance and distributive mixing performance. When the triple screw and co-rotating twin screw extruder had achieved similar mixing effects through preparing the PP/EPDM blends, the length-to-diameter ratio of the triple screw extruder is smaller than twin screw extruder and triple screw extruder have got more throughput than twin screw extruder. During preparing nanoCaCQ3 content of 70% of the masterbatch by the triple screw extruder, the devolatilization and venting are very remarkable, the masterbatch was dense and the apparent density of the masterbatch was larger.2. During preparing the PP/EPDM blends, the power and consumption energy of the three extruders were acquired by extrusion process data comprehensive collection system developed by our team and then the specific energy input (SEI) of the three extruders were comparatively analysed.The triple screw extruder have been lower SEI under the processing conditions of mean shear rate 40～120 s-1 and throughput(geomtric similar throughput)3-12 Kg-h-1, respectively 9% and 33% lower than co-rotating twin screw extruder with a large length-to-diameter ratio.3. The screw shear of the triple screw extruder and mean residence time of the melt in the triple screw extruder have great influence on dispersive mixing effects of rubber particles and the mechanical properities of blends. Due to the PP/EPDM blends were sheared frequently and the mean residence time was longer, the shear temperature rise was higher in the triple screw extruder, blends was easy to degradate, then the mechanical properties of blends were dropped. Under the following mixing process:lower processing temperature, low shear strength of screw configuration, screw speed 93～133 r/min and feed quantity 16-20Kg·h－1,the dispersive mixing effect and mechanical properties of the PP/EPDM blends were better, simultaneously the energy consumption of the triple screw extruder was lower.