三螺旋大幅正弦扰动协同的聚合物混合混炼机理研究

The alternately effect of multi-screw and multi-phase is a key approach to enhance the mixing effect of polymer processing. But owing to the large viscosities of polymer melts, it is difficult to disturb the melt flow during the conventional mixing process. To address this issue, in this work, we develop a novel polymer mixing method based on the synergetic effect of tri-screw and large-amplitude sinusoidal turbulent. A novel ‘balance’ structure that can counteract the force on the screws given by materials is reported by feeding the polymers in bi-ends of the extruder. To the best of our knowledge, this work for the first time achieving the synergetic effect of multi-screw, multi-phase and large-amplitude sinusoidal turbulent in the polymer mixing process. By utilizing such method, a complex flow that coupling both elongation flow and shear flow with large amplitude alternation during polymer processing, which can further lead to an enhanced mass and heat transfer processing during mixing. In this work, several conventional used polymer blend and composite systems are processed to build a theoretical model of such complex flow. By combined analysis of the theoretical prediction, dynamic in-situ visual detection and finite element numerical simulation, this work also intend to study the effect of the amplitude and frequency of sinusoidal turbulent, temperature, rotation speed and other structure parameters of the equipment on the distribution and dispersion effect of various material systems with different rheological properties. In this work, a precise control method of the phase morphologies is also reported. In sum, this work presents a novel method as well as the theoretical work for the polymer mixing process that shows important values in both academy and industry.

多螺旋多界面交替变化是强化聚合物混合混炼过程的重要手段，但由于聚合物熔体黏度高，在混炼过程中实现大幅扰动流场非常困难。本课题提出了三螺旋大幅正弦扰动协同聚合物混合混炼新方法，将研究两端对称进料以抵消物料对螺旋作用力的新型“平衡式”结构，在三螺旋聚合物混合混炼过程中首次实现多螺旋多界面大幅正弦扰动的协同作用，在聚合物加工过程中产生大幅度周期变换的拉伸-剪切耦合复杂流场，强化混合混炼过程中物质与热量的传递；将以典型的聚合物共混、填充体系为主要研究对象，建立拉伸-剪切交替变换流场作用下的混合模型，将理论研究与动态可视化在线检测及有限元数值模拟仿真相结合，分析正弦扰动幅度与周期、混炼系统的温度与转速和设备结构参数对不同流变特性复杂体系分散行为的影响规律，形成三螺旋大幅正弦扰动协同作用下分散相形态精确调控方法。本课题将为聚合物改性提供新的加工方法及指导理论，具有重大的科学意义和巨大的应用价值。

由于聚合物熔体黏度高，难以在混炼过程中引入大幅扰动流场。本项目提出两端对称进料以抵消物料对螺杆作用力的新型“平衡式”结构，解决了大幅正弦扰动作用力场的引入难题。首先，通过建立动力学模型分析振动力场的引入对加工流场的影响，从理论上证明了振动力场的引入在平衡式三螺杆动态挤出机中产生了周期性变换的拉伸-剪切复杂流场。其次，运用数值模拟方法研究了平衡式三螺杆动态挤出机均化段啮合块的混合性能，数值模拟分析结果表明振动力场的引入增强了平衡式三螺杆动态挤出机的混合分散性能。对聚乳酸基生物可降解共混体系的实验研究表明：聚乳酸/聚丁二酸丁二醇酯/甲基丙烯酸缩水甘油酯（PLA/PBS/EGMA）三元共混物的拉伸强度、断裂伸长率和冲击强度都随振幅或振频的增加而增加。随着振幅或振频的增加，振动力场引入的扰动流场越强，促进了三相材料的混合，提高了PLA/PBS/EGMA共混物的相容性。对聚乳酸基生物可降解填充体系的实验研究表明：随振幅或振频的增加，有机蒙脱土（OMMT）的团聚现象逐渐消失，使得OMMT被剥离且均匀分散在PLA基体中。由于OMMT对PLA有异相成核的作用，PLA/OMMT复合材料的结晶度随振幅或振频的增加呈现上升的趋势。最终，相比于稳态加工方法，动态加工方法制备的PLA/OMMT复合材料的拉伸强度、断裂伸长率和冲击强度都有显著的提升。对聚合物共混体系和填充体系的研究表明，振动力场引入所产生的拉伸-剪切复杂流场在聚合物共混改性和填充改性方面具有独特的优势。为了进一步增加平衡式三螺杆挤出机内拉伸流场的占比，本项目设计了一种新型的拉伸混合元件，模拟研究结果表明，此拉伸混合元件能够显著增强三螺杆挤出机内的拉伸流场占比，混合指数最高可达0.9左右，本项目的后续工作将围绕此拉伸混合元件进行实验研究。本项目的研究成果为聚合物的共混改性和填充改性提供了新的加工方法及指导理论，丰富了高分子材料的成型加工方法及理论。