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聚合物熔体体积输送动力学模型及解析研究

Research of Polymer Melt Volume Transportation Dynamic Model and the Analytical Solution

【作者】 翟术风

【导师】 瞿金平;

【作者基本信息】 华南理工大学 , 机械设计及理论, 2014, 博士

【摘要】 以螺杆为标志的传统的聚合物加工设备存在着热机历程长、能耗高等普遍问题,以拉伸流场支配的叶片挤出机是聚合物加工中一种全新的加工设备,目前以剪切拖曳为主的单螺杆熔体输送理论研究已经形成了比较完善的理论体系。拉伸流场支配的叶片挤出机的工作方式和熔体输送机理与传统的单螺杆挤出机完全不同,因此单螺杆熔体输送机理不适合叶片挤出机熔体输送过程,研究叶片挤出机熔体输送机理不仅有利于优化叶片挤出机设计结构,而且有利于聚合物加工理论的发展和完善。本文基于拉伸流变的聚合物塑化输运设备的基本构成单位叶片塑化输运单元为研究对象,首次比较完整系统地研究了叶片挤出机聚合物熔体输送过程,提出了熔体体积输送的输送理论,在叶片单元塑化输送机理的基础上,建立数学物理模型,分析熔体体积输送过程中周向以及轴向方向熔体的运动规律,并在此基础上建立了熔体体积输送能耗模型,熔体输送能耗过程的实验结果与挤出机实际加工时的能耗实验结果呈现出比较好的一致性。通过建立熔体体积输送过程的数学物理模型,分析了轴向、周向熔体拉伸形变速率,结果发现:聚合物熔体体积输送在很大程度上受到容腔体积的周期性变化的影响,聚合物熔体在容腔中输送时产生轴向和周向的拉伸形变,同时还受到轴向的正应力场的影响,聚合物熔体的体积输送基本实现了正位移输送,其对物料的依赖性显著减弱。本文还通过建立熔体体积输送过程的数学、物理模型探讨研究了熔体体积输送能耗特性,研究结果表明:聚合物熔体体积输送的能耗与温度成反比关系,温度越高,聚合物熔体体积输送的能耗越小,相反温度越低,聚合物熔体体积输送的能耗越大;聚合物熔体体积输送的能耗是与转速成正比关系,转速越大,聚合物熔体体积输送的能耗越大,相反转速越小,聚合物熔体体积输送的能耗越小;熔体体积输送的能耗值与物料的黏度成正比关系,聚合物物料的黏度越大,熔体体积输送所需要的能耗就越大,聚合物物料的黏度越小,熔体体积输送所需要的能耗就越小。最后利用组装式叶片实验挤出机对叶片容腔熔体输送过程中的叶片挤压系统的能耗进行了实验研究,实验结果与理论预测的结果有比较好的一致性。基于拉伸流变的聚合物塑化输运方法和设备是一种全新的聚合物加工方法和设备,本文提出的聚合物熔体体积输送过程模型,为进一步研究叶片挤出机挤出过程打下了良好的基础,也为聚合物叶片塑化输运设备的推广应用提供了重要的理论依据。

【Abstract】 Traditional polymer processing equipment with a symbol of screw exist the problems oflong thermal history and high consumption, the vane extruder based on elongation rheology isa completely new theory and machinery for polymer processing. At present, the research ofthe single-screw melt conveying has been formed a relatively complete theoretical system, thework ways and plasticizing and conveying mechanism of the vane extruder are fully differentwith the screw extruder, thus, the screw melt conveying is not suitable for the vane conveyingprocess. The researches on the vane melt conveying are benefit for the optimization design ofthe vane extruder and have important scientific and practical significance to the developmentand improvement of the polymer processing theory based on elongation rheology.Vane plasticizing and conveying unite (VPCU) is the basic unit in polymer processingmachine, in this paper, the whole melt conveying process is studied systematically for the firsttime and the theory of melt volume conveying has been presented. Based on the vaneplasticizing and convey theory, melt conveying mathematical model and the energyconsumption model are developed to study the melt radical velocity, the circumferentialvelocity and the axial velocity in the VPCU, the experiment results are consistent with thepredictions of energy consumption models.The radical, the circumferential and the axial strain rate of the polymer have been studiedby the melt conveying mathematical model, the results shows that, the cavity volume ofperiodic change has important influences on the melt conveying and the polymer melt endureelongation strain both in the axial and the circumferential direction in the chamber, and anormal stress field in the axial direction formed in the chamber can help to convey the meltwith positive displacement and not depending on the properties of the materials.Through building the energy consumption model in the melt conveying process, theenergy consumption characteristic is analyzed in the paper. The research shows that, thehigher the temperature, the smaller energy consumption of polymer melt conveying is; energyconsumption in the polymer melt conveying press is proportional to the rotational speed of therotor; energy consumption in the polymer melt conveying press is inversely proportional tothe rotational speed of the rotor.Finally, energy consumption characteristics in polymer solids conveying process, meltconveying process and the whole plasticizing and conveying process including solidsconveying, melting and melt conveying in vane extrusion system have been studied experimentally by means of the compositional vane experimental device and the vaneextruder. The experiment results are consistent with the predictions of energy consumptionmodels.The method and equipment of polymer plasticizing and conveying based on elongationrheology is a completely new theory and machinery for polymer processing. The proposedmodels of polymer melt conveying process in VPCU and the energy consumption in theprocess laid a good foundation for further study of polymer vane plasticizing extrusionprocess and its mechanism. This study provided an important theoretical basis for thepromotion of the vane plasticization equipment for polymer processing.

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