Study Of Mixing Mechanism And Macroscopic Reaction Characteristics Of Polymer In A Batch Mixer

Mixers are widely used in the processing of the polymer mixture.The rotor system is the core component of the mixers. Rotor geometryand the operating conditions are the main factors controlling the mixingintensity. Therefore, using the rotor system as the core to study themixing mechanism, revealing the relationships and impact mechanismbetween the intensity of the flow field and the macroscopic reactioncharacteristics of polymer melt are the important theoretical basis toregulate the equipment parameters and process parameters in order tocontrol the reaction process precisely.The flow in2D rotor mixers were numerically simulated using thecomputational fluid dynamics package Polyflow, and the rotationalspeeds of the rotors are9:6rpm,18:12rpm and30:20rpm respectively.And we got the velocity field from the numerical simulations. Themixing effect was evaluated statistically using particle tracking method.We calculated and compared the dispersive mixing performance,distributive mixing performance, logarithm of stretching and mixingefficiency. The results shows that, the faster rotational speed of therotors, the higher frequency share stress and elongation the melt in theroller rotor mixer experienced during the same time. What was more,the left rotor and right rotor meet in the mixing region more frequently,is better for the exchanging of materials in the region, which is good forimproving the distributive mixing efficiency. In this article, wecompared the simulation results with the results of the experiments. Interestingly, there is a perfect analogous between the two results. So,the results of the simulation are correct. We compared the mixingperformance of mixers with different configurations. The results showsthat, under the same rotational speed of9:6rpm, the more lobs of therotor, the better mixing performance of the mixer. This is mainlybecause of that, with more lobs, the material in the mixer endures sharestress and elongation more frequently.Mixers as important equipments in the polymer processingindustry, not only be widely used in the mixing processes, but also beused as reactors. The process of sol-gel reaction preparing PP/TiO2nanocomposites was numerically simulated using the finite elementmethod and programs defined by UDFs in Polyflow. The influence ofrotor speed ratio, temperature, stretch mixing efficiency and precursormass fraction on the conversion rate in either part or the whole mixerwas studied. From the local perspective, the result shows that theasymmetry of the flow field increases with the speed ratio of the rotors,and the deflection phenomenon becomes more obvious. Thetemperature and conversion rate of the reaction in part of the mixerincrease with the rotor speed ratio either. From overall perspective,when the mechanical energy consumption is the same, the chaoticmixing intensity and the average mixing efficiency of the mixerincrease gradually with the rotor speed ratio. Under the same flow fieldintensity, the average mixing efficiency increases with the averagetemperature. This paper also studied the effect of numbers of rotor lobson the conversion rate in the mixer under the same rotational speed. Theresults show that the conversion rate is higher when the number of rotorlobs is high.