Abstract
To better understand the relationship between flow, mixing and reactions in the process of preparing PP/TiO2, a 3D numerical simulation in a co-rotating twin screw extruder (TSE) was firstly employed using commercial CFD code, ANSYS Polyflow. The effects of rotating speed of screws, stagger angle of knead blocks, inlet flow rate and initial temperature of barrel on the mixing and reaction process in the TSE were investigated. The results reveal that the studied operational and geometric parameters, which determine mixing efficiency, residence time distribution, and temperature of the flows in the TSE, affect the local species concentration, reaction time and reaction rate, and hence have great influences on the conversion rate. The results show that increasing the rotating speed and inlet flow rate can decrease the time for sufficient mixing, which is not conducive to intensive reaction, and increasing the stagger angle has the opposite effect. Moreover, the conversion rate greatly affected by the initial temperature of barrel.
Highlights
The application of Polypropylene (PP) covers many industrial fields, including film, thermoforming and automotive fields, due to its easy processability, relatively high mechanical properties and great recyclability [1]
The corotating twin screw extruder (TSE) investigated in this study consisted of a flow channel and two combined elements, as shown in Figure 1a,b, which consisted of thread sections and kneading block sections
Effect of of initial initial temperature temperature of of barrel barrel on Figure 15b shows the distribution of average conversion rate change in the TSE at different initial temperatures of barrel
Summary
The application of Polypropylene (PP) covers many industrial fields, including film, thermoforming and automotive fields, due to its easy processability, relatively high mechanical properties and great recyclability [1]. One way to improve the PP properties mentioned above is to disperse titanium dioxide (TiO2 ) into PP matrix [3]. In situ sol–gel reactions in melt are the most suitable method for producing dispersed TiO2 nanoparticles in PP matrix without solvent, and it can be applied to industrial processes in a twin screw extruder. Twin screw extruders (TSEs) have been broadly applied in the processing of polymer nanocomposites due to their excellent mixing performance and modular design characteristic. With the great improvement of computing power, the simulation methods have been intensively used to better understand the factors influencing the preparation of nanocomposites by reactive extrusion
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