3‐D numerical simulations for polycondensation of poly(p‐phenylene terephthalamide) in twin screw extruder

Abstract

Poly(p-phenylene terephthalamide) (PPTA) is a typical high-performance fiber and usually synthesized by low temperature solution polycondensation in twin screw extruder. During the reactive extrusion, flow behavior, rheokinetics, and temperature are highly coupled, which makes it difficult to ensure the quality of product. In the present work, the rheokinetics of the PPTA solution is established by experiments and its reactive extrusion is investigated via 3-D numerical simulation. The flow pattern, molecular weight distribution and temperature have been investigated for the extruders with three different elements, i.e., full flight screw (FF), kneading block (KB), and screw mixing element (SME). The results indicate that the unique flow characteristic of different screw elements affects mixing experience of the reactants and further the PPTA qualities. By numerical simulation, it shows the temperature increase within the tested extrusion stage is 7 K and reaction heat is found the main energy source for extrusion stage. Furthermore, heat removal method is verified with consideration of industrial production process. The numerical simulation work also discusses the reaction and mixing process in the extruders with three combined screws. The results show the introduction of more reverse FF and KB elements can lead to higher quality of FIG. 2. Rheokinetics of PPTA during polycondensation: (a) effect of shear rate on viscosity. (b) Effect of M w on consistency index. [Color figure can be viewed at wileyonlinelibrary.com]

Experimental methods in chemical engineering: Reactive extrusion

“…Zhu et al [ 80 ] studied the theoretical effects of screw rotating speed, screw element geometry, and initial conversion at the extruder inlet on polymerization of ϵ ‐caprolactone based on 3D fully‐filled twin‐screw conveying elements using Fluent. Zong et al [ 86 ] experimentally researched the rheokinetics of Poly( p ‐phenylene terephthalamide) polycondensation and then theoretically compared flow pattern, temperature, and molecular weight distribution in the conveying screw, kneading element, and SME based on 3D geometric models on the Polyflow platform. More recently, Sun et al [ 87 ] simulated the reactive preparation of PP/TiO 2 nanocomposites in a TSE with two linked screws of conveying and mixing screw elements based on the Polyflow platform as well.…”

Non-Isothermal Simulation and Safety Analysis of Twin-Screw Extrusion Process for Synthetizing Glycidyl Azide Polymer-Based Energetic Thermoplastic Elastomer

“…Zhang et al [ 32 ] prepared a polypropylene (PP)/wood-fiber (WF) composite foam using the pressure quenching batch method and investigated the effects of the screw configuration, screw speed and silica on the physical and mechanical properties and foaming properties of PP/WF composites. Zong et al [ 33 ] studied the flow pattern, molecular weight distribution and temperature of poly (p-phenylenediamine terephthalate) in three extruders with different elements. Zhang et al [ 34 ] calculated the area draw ratio, instantaneous efficiency and time average efficiency of the mixing disc by studying the distributed mixing power and simulated the local residence time distribution of the TSE using the particle tracking method.…”

Study on the Function of Conveying, Kneading Block and Reversing Elements on the Mixing Efficiency and Dispersion Effect inside the Barrel of an Extruder with Numerical Simulation

“…Water as a plasticizer in the extrusion process greatly affects the flow behavior of the fluid; the flow situation inside the extruder also depends on the highly coupled operating conditions, poly-condensation dynamics and rheology dynamics, due to changes in the interaction between the pressure flow and drag flow generated during the rotation of the screws [ 25 ]. Given that raw food materials have deformable, hygroscopic and amorphous properties in a multi-phase mixing and dispersion system, it is necessary to control the extrusion process through theoretical analysis in order to improve the adaptability of different process parameters and meet various needs in different application scenarios [ 26 , 27 ]. Under the limitation of the closed chamber in the extruder, numerical simulation can effectively reveal the shear mixing effect of the fluid, accurately describe the local flow characteristics inside the barrel and provide more detailed information about the “black box” than the experimental study.…”