串联式磨盘螺杆挤出机的结构与混炼机理

介绍了自行开发研制的新型混炼装备——串联式磨盘螺杆挤出机的主要结构特点及工作原理，剖析了其独特的混炼机理。试验表明，采用多种形式的串联磨盘能够起到对物料的压缩、剪切与置换三种作用，串联式磨盘螺杆挤出机具有卓越的混炼、塑化性能，而且该机结构简单、挤出压力高。     

主要工艺参数对串联式磨盘挤出机混合性能的影响

采用Polyflow软件模拟了聚合物熔体在串联式磨盘挤出机混炼段内的混合过程。将混合指数和分离尺度作为评价指标,借助统计学方法,分析了主要工艺参数(转速和喂料速率)对串联式磨盘挤出机混合性能的影响。研究结果表明:转速增大,串联式磨盘挤出机的分散混合性能和分布混合性能提高;喂料速率增大,串联式磨盘挤出机分散混合性能下降,但喂料速率对串联式磨盘挤出机分布混合性能影响较小。     

串联式磨盘螺杆挤出机设计原理

结合新型混炼装备CPJ 75/135型串联式磨盘螺杆挤出机的开发研制实践,分析了混炼过程压缩、剪切和置换三要素,从混炼机理、输送原理、温度和剪切变形总量的控制等角度阐述了串联式磨盘螺杆挤出机的核心部件———磨盘的设计原理。研究结果可为该类机型的推广应用和系列化开发提供经验和帮助。     

串联式磨盘螺杆挤出机设计原理

随着新型高分子材料的不断出现，对混炼技术和装备的要求越来越高，传统的混炼工艺与装备已不能能满足要求，具有各种特色、性能优异的新型混炼装备应运而生。串联式磨盘螺杆挤出机是国际上20世纪研究成功的新型混炼装备之一，它不仅具备了单螺杆挤出机结构简单、挤出压力高、承载扭矩大的优点，而且具备磨盘挤出机超强的破碎、分散、剪切、混合和塑化性能优势，同时还可以通过动盘和定盘结构型式的选择、间隙的调节以及工艺条件的变化等手段对混炼工艺过程进行控制，因此用它可以制取一般混炼装置难以加工的特殊高分子材料和高填充复合材料。     

新一代串联式磨盘挤出机

本文简单介绍了串联式磨盘螺杆挤出机的结构特点,将新一代机型可挤出系统,加热冷却系统进行了阐述,通过实验方法对混合性能及混炼质量的影响因素进行了对比和研究,最终总结出有利于提高混炼质量的有效方法和方案。     

串联式磨盘螺杆挤出机一步法挤出成型木塑复合材料的研究

对串联式磨盘螺杆挤出机一步法挤出成型木塑复合材料进行了实验研究，探讨了植物纤维种类、木粉填充量对复合材料力学性能的影响，并在相同配方的条件下对磨盘挤出机和异向平行双螺杆挤出机加工的木塑复合材料的力学性能进行了比较。研究结果表明串联式磨盘螺杆挤出机更适合于高填充木塑复合材料的挤出成型加工。     

三螺杆挤出机与双螺杆挤出机混合性能的比较

利用聚合物流体分析软件Polyflow,对倒三角形排列的三螺杆挤出机和等规格的双螺杆挤出机的混合性能进行了深入分析。通过计算不同角度的拟稳态流场,采用示踪粒子法对聚合物熔体在流场中的动态混合情况进行三维等温数值模拟,在此基础上对粒子轨迹进行统计后处理,并分别采用混合指数、面积伸展率和停留时间分布表征流场的分散混合能力、分布混合能力和轴向混合能力,进而比较两种挤出机的混合性能。另外,在实验条件与模拟条件相同的情况下,进行了实验验证。模拟结果表明,三螺杆挤出机各方面的混合性能均优于双螺杆挤出机。实验结果表明,实验数据与模拟结果基本一致。     

三螺杆挤出机螺杆元件混合特性的数值研究

采用聚合物流体分析软件Polyflow对倒三角形三螺杆挤出机的6种螺杆元件的流道模型进行了三维等温数值模拟。使用Fieldview软件对结果进行统计处理,并采用不同的评价指标来表征混合性能,进而比较螺杆元件之间的混合特性。结果表明,捏合块的剪切和拉伸作用均强于螺纹元件;中性捏合块和左旋元件的回流效果好于其他元件;SME元件剪切弱于螺纹元件,但其拉伸作用和回流效果强于螺纹元件。因此,可根据物料对剪切的敏感性来合理地选择螺杆元件,以获得所期望的产品性能。     

连续混炼装备混合性能的对比研究

以聚对苯二甲酸乙二酯(PET)/聚丙烯(PP)不相容体系的共混为结合点,对比研究了啮合同向平行双螺杆挤出机(TSE)、往复式单螺杆销钉挤出机(RSPE)和串联式磨盘挤出机(SDSE)三种连续混炼装备的混炼性能.共混物微观结构以及宏观力学性能均表明,三种装备中SDSE的混炼效果最好,RSPE的混炼效果稍强于TSE.从比能耗看,加工单位质量物料SDSE耗能最多,而RSPE和TSE耗能基本一致.     

Numerical simulation and experimental validation of mixing performance of kneading discs in a twin screw extruder

This work aims at simulation by particle tracking the local residence time distributions (RTDs) of a co‐rotating twin‐screw extruder using computational fluid dynamics. Simulated results follow reasonably well the trend of experimental results obtained by an in‐line measuring instrument for different screw configurations and feed rates. To analyze the distributive mixing performance and overall efficiency of different types of kneading discs (KDs), mixing parameters such as area stretch ratio, instantaneous efficiency, and time‐average efficiency are calculated. Among KDs with stagger angles 45°, 60°, and 90°, the 90/10/64 with disc gaps is most efficient in terms of distributive mixing. The effects of the disc width and disc gap on the local RTD and distributive mixing are also discussed. This provides a numerical tool for assessing point‐by‐point information on the local RTD, flow, and mixing along the screw extruder. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Flow field analysis of the kneading disc region in a co-rotating twin screw extruder

Co-rotating, intermeshing twin screw extruders are widely used in polymer compounding and blending. Among the different modules of the co-rotating twin screw extruder, the kneading discs are the dominant ones in determining mixing efficiency. The major difficulty in solving the flow problem in the kneading disc region arises from the complex geometry and the time-dependent flow boundaries as the discs rotate. In this work, a fluid dynamics analysis package—FIDAP—using the finite element method was employed to simulate the flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-30 co-rotating twin screw extruder. The problem of time dependent flow boundaries was solved by selecting a number of sequential geometries to represent a complete mixing cycle. The flow field was characterized in terms of velocity profiles, pressure distributions, shear stresses generated and a parameter λ quantifying the elongational flow components. The last two parameters are the most important ones in analyzing mixing efficiency. The influence of design variables (stagger angle, right or left handed configuration) and processing conditions (rpm, axial pressure gradient) on the flow characteristics was analyzed.     

Experimental validation of numerical simulations of the kneading disc section in a twin screw extruder

A comparison of the results of a 3D model for the simulation of flow in the kneading disc region of a fully intermeshing twin screw extruder has been done against particle image velocimetry (PIV) experimental data. Experimental results using a geometry with an extended first and last kneading disc to capture the simplified inlet and outlet boundary conditions, are in good qualitative agreement for low flow rates. The results showed good agreement at flow rates less than 5 mL/s and rotation speeds of 60 rpm, while above that there was poor agreement. These results highlight the importance of the use of appropriate boundary conditions for the accurate prediction of the flow field. The flow field within the kneading discs with forward conveying elements placed before and after the kneading discs was also measured. For a flow rate of 8.5 mL/s and 60 rpm, results showed good agreement when conveying elements were deployed before and after the kneading blocks whereas for lower flow rates there was poor agreement.     

三螺杆塑炼机

介绍了作者新研究开发的三螺杆挤出技术及装备。新技术利用倒品字型排列的全啮合三螺杆所构成的三个啮合区，实现对物料高效的塑炼作用。     

Study of mixing efficiency in kneading discs of co-rotating twin-screw extruders

Co-rotating twin-screw extruders are widely used for compounding and blending in polymer processing. In a modular machine, the dominant elements determining dispersive mixing efficiency are the kneading discs. A fluid dynamics analysis package - FIDAP, using the finite element method was implemented to simulate the 3-D isothermal flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-53 co-rotating twin-screw extruder. The kneading discs simulated are three-lobe discs. The flow field characteristics relevant for dispersive mixing are shear stresses generated and elongational flow components. We compare these flow characteristics for the three-lobe kneading discs of the ZSK-53 with the two-lobe discs of a ZSK-30 machine. We also discuss the influence of processing parameters on the flow field mixing efficiency.     

螺杆挤压机混合能力的分析

分析螺槽中熔体的流动状态 ,运用加权平均总应变来评价螺杆挤压机的混合能力 ,进而提出提高混合能力的途径。对于单螺纹螺杆 ,稍长的计量段 ,稍浅的计量段螺槽及较高的螺杆转速 ,有利于混合作用 ;开发新型螺杆 ,如犁钉分流混合螺杆 ;研制高效混合型螺杆挤压机 ,如球窝型高效混合型螺杆挤压机     

Polymer blend mixing and dispersion in the kneading section of a twin-screw extruder

This paper examines the mechanisms by which a polymer is dispersed in a co-rotating twin-screw extruder. An experimental investigation of the morphological evolution has been carried out on a 45-mm co-rotating twin-screw extruder. Polyethylene/polystyrene (PE/PS) blends in the low concentration range (i.e., 5–15 wt% of PE) were used as a model system. The following general trends were observed. First, the minor phase right after melting is predominantly in a fibrillar form. Secondly, droplet and fiber diameter at this early stage of compounding are already in the micron or sub-micron range. Even though a wide variety of mixing section configurations were used, the fibers created in the early compounding stages were relatively stable throughout extrusion. Morphological evolution after melting must therefore be discussed in terms of variation in the fiber fraction (i.e., fiber to droplet transition) rather than in a change in particle diameter. A control volume model for the flow in kneading blocks is used to interpret the morphological results and to predict the deformation and breakup of dispersed phase fibers under shear and in absence of coalescence. Theoretical results indicate that fiber breakup under shear is not likely in the kneading block under the normal processing conditions, which is confirmed by morphological observations made at the mixing section exit. The influence of several geometrical parameters on mixing and pumping in kneading blocks is also discussed with the use of flow model results.     

立式捏合机捏合间隙影响CFD分析

本文利用计算流体力学(CFD)方法研究捏合间隙对立式捏合机混合性能的影响。首先,根据立式捏合机搅拌桨叶运动特点以及被混物料的流变特性,进行立式捏合机混合流场数值模拟。其次,确定立式捏合机混合性能宏观评价指标。最后,分析了捏合间隙的变化对混合性能评价指标的影响。分析结果表明：间隙越小,立式捏合机的混合性能越好;当空心桨叶两侧的捏合间隙大小相等时,立式捏合机的功耗最小。     

挤出机螺杆直槽式屏障混炼元件的优化设计

研究挤出机螺杆直槽式屏障混炼元件的优化设计问题。根据粘性流体流动基本方程。以单位产量能耗最小为优化目标,建立简化的挤出机螺杆直槽式屏障混炼元件优化设计的数学模型，并应用复合形法求解，确定剪切长度、剪切问隙、屏障长度和屏障槽数等主要几何参数。本研究优化结果均在文献所建议的最佳取值范围内。