啮合同向双螺杆挤出机新型混炼元件性能及应用

就全啮合同双向螺杆挤出机中的混合过程进行了分析讨论，分析了普通螺纹元件和捏合盘元件的混合特性和泵送特性，针对这些元件存在的问题讨论了新型混炼元件的特点（包括典型分散性混炼元件和典型分布性混炼元元件），并作了深入的对比讨论，就上述元件在聚合物改性加工，共混和填充过程中典型的应用示例进行了分析讨论。     

同向双螺杆熔融段螺杆组合对共混物相态变化的影响

研究了双螺杆熔融段不同螺杆组合对模型聚合物共混体系HDPE/PS相态变化的影响。发现错列角为正向30°及正向60°的捏合块具有较好的输送能力,但不利于物料的熔融和混合;90°错列角捏合块对共混物具有很好的熔融和混合效果,其混合性能甚至优于反向30°捏合块,接近反向60°捏合块;及向螺纹元件对共混物相态变化影响显著。     

Mechanisms of mixing in single and co-rotating twin screw extruders

Previous experimental studies have revealed that the mixing efficiencies of widely used continuous processors such as the single and twin screw extruders depend on the types of screw elements, which are utilized. It is generally recognized that the basic single screw extruder and the fully-fighted sections of the fully-intermeshing co-rotating twin screw extruders are not efficient mixers, in contrast to the specialized mixing elements such as the kneading discs used in co-rotating twin screw extruders. However, no simulation techniques were available to characterize quantitatively and rigorously the mixing efficiencies of continuous processors. In this study, we have solved the three-dimensional equations of conservation of mass and momentum, and utilized various tools of dynamics to analyze the mixing occurring in single and co-rotating twin screw extruders. It is shown that simulation methods can indeed capture the relative differences in the mixing mechanisms of continuous processors like the single and twin screw extruders. The ability to distinguish quantitatively between the distributive mixing capabilities of various continuous processors should facilitate numerical testing of new continuous mixer designs, optimization of operating conditions and geometries of existing mixers and the material-specific design of new mixers.     

Simulation of non-isothermal flow in modular co-rotating twin screw extrusion

Non-isothermal flow is simulated in the screw and kneading disc elements in a modular co-rotating twin screw extruder. Methods of calculating mean temperature rises for individual elements are discussed and results are presented. The implications of non-isothermal operation for scale-up is discussed. A method is then described for making calculations in a modular co-rotating machine, that contains many different elements. Example calculations are given showing the tendency of larger machines to buildup greater temperatures when viscous heating is included.     

An experimental study of distributive mixing in fully intermeshing,co-rotating twin screw extruders

Co-rotating twin screw extruders are widely used for various mixing and reactive extrusion tasks in polymer processing operations. In this study, the prevailing mixing mechanisms of various screw elements employed in co-rotating twin screw extrusion process, including regular flighted, and reverse and forward kneading disc elements, were experimentally investigated. A direct goodness of mixing technique based on pigmented thermoplastic elastomers and computerized image analysis was used. The results were elucidated in conjunction with mixing indices suitable for image analysis and the continuous mixing process. Significant differences in the distributive mixing characteristics of various screw elements were revealed.     

啮合同向双螺杆挤出过程组合流道(捏合块 螺纹元件)三维流场分析

利用ANSYS有限元分析软件对啮合同向双螺杆挤出机由捏合盘和螺纹元件组合而成的流道进行了三维等温非牛顿模拟分析 ,得到了组合流道的速度场和压力场。并对螺纹元件流道、捏合块流道及组合流道的流量、回流量、拉伸速率、剪切速率及剪切应力进行了比较。     

Modeling melt conveying and power consumption of co-rotating twin-screw extruder kneading blocks: Part B. Prediction models

Intermeshing co-rotating twin-screw extruders are very versatile because their screw configurations can be tailored both to the application and to the properties of the materials used. Finding the best screw configuration is one of the main purposes of twin-screw extrusion modeling, and requires models that accurately predict conveying and power consumption. The better the process can be predicted, the better the requirements of the final product can be met. We present novel prediction models of the conveying and power-consumption behaviors of intermeshing co-rotating twin-screw extruder kneading blocks for Newtonian fluids. These are based on numerical simulations and therefore consider the complex three dimensional (3D) geometry of this element type without the need for common simplifications. Our models are thus capable of including all leakage flows and gap influences, which are usually ignored, for example, by the flat-plate model. Since our models are derived by symbolic regression based on genetic programming, they consist of algebraic functions and are low-threshold. They can be used to calculate various process parameters for individual kneading blocks or entire screw configurations, as illustrated by a use case.     

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.     

Mixing mechanism of three‐tip kneading block in twin screw extruders

In recent years, twin screw extruders have been applied to various kinds of polymer processing. It has been important to find their optimum geometrical configurations and operational processing conditions for the best performance of extrusions and products. Many engineers have been evolving numerical and the experimental methods to characterize the mixing performance for twin screw extruders. We have carried out three‐dimensional flow simulations of kneading blocks in intermeshing co‐rotating twin screw extruders by using the finite element method to quantify their ability in distributive and dispersive mixing. We discuss their performance in distributive mixing for three different type of kneading blocks in terms of the residence time distribution and the nearest distance between markers at various periods of time, by using the marker tracking method. Those numerical techniques and applications of mixing indices have enabled us to quantify and evaluate their abilities in distributive mixing of kneading blocks in twin screw extruders.     

啮合同向双螺杆挤出过程聚合物粒料熔融机理研究(二)——正向捏合块组合中熔融机理研究

以装有玻璃视窗的可视化双螺杆挤出机为手段，在不同操作条件下对高密度聚乙烯（ＨＤＰＥ）粒料在不同正向捏合块（即由正向捏合盘所组成的螺杆区段）中的熔融过程进行了实验研究。以实验现象为基础，提出了双螺杆挤出过程中海－岛式熔融模型的概念。研究表明，耗散－混合熔融是捏合块中聚合物熔融的主要机理，海－岛式熔融模型是捏合块中聚合物熔融的典型形态；螺杆构型、螺杆转速、加料量是决定聚合物颗粒熔融的主要因素。     

啮合同向双螺杆挤出过程聚合物粒料熔融机理研究(三)——反向捏合块组合中熔融机理研究

以装有玻璃视窗的可视化双螺杆挤出机为手段，在不同操作条件下对高密度聚乙烯（ＨＤＰＥ）粒料在不同错列角、不同轴向长度的反向捏合块的熔融过程进行了实验研究。以实验为基础，讨论了加料量、螺杆转速以及反向捏合块厚度与错列角对聚合物颗粒熔融过程的影响。研究表明，反向捏合块的阻力大小对聚合物的熔融过程十分重要，捏合块中物料的充满度与物料的停留时间是聚合物颗粒熔融的决定因素。     

Modeling of the conveying of solid polymer in the feeding zone of intermeshing co-rotating twin screw extruders

In this paper, a model for the conveying of solid polymer in the feeding zone of intermeshing co-rotating twin screw extruders is proposed. The theoretical model uses an approach that is similar to that commonly used in single screw extruders; however, it takes into account the particular geometry of the screw channel, the partially filled channel, and the special configuration of the two self-wiping screws. The model thus considers two conveying mechanisms: the first one in the channel, which is analyzed in terms of polymer-metal friction, and the second one, which is mainly an axial transport in the intermeshing zone. The theoretical predictions of the model are compared with the experimental results obtained on a laboratory extruder with a polymer in powder form, and satisfactory agreement is observed. The model enables the prediction of the evolution of the filling of the screws towards the geometry and the operating conditions. This is an important key to analyzing the thermal aspects in this zone, which can lead to a prediction of the melting capacity of the extruder. Indeed, the filling of the feeding zone defines the heat transport that occurs between the hot barrel and the solid polymer.     

啮合同向双螺杆挤出机中组合螺杆性能的数值研究（Ⅰ）瞬态流场分析

采用聚合物流动分析软件POLYFLOW,数值模拟了聚合物熔体在组合式啮合同向双螺杆挤出机ZSK60的组合螺杆中的三维等温流动。在计算所得速度场和压力场的基础上,全面分析并讨论了由不同厚度和不同错列角的捏合块元件组成的组合螺杆的流场分布规律;研究了组合螺杆的输送性能和挤出稳定性;并分别采用平均剪切速率、平均特征剪切应力以及平均拉伸流动指数等瞬态混合指数表征了组合螺杆的瞬态混合特性。此外还考察了两种不同流变性质的聚合物熔体在组合螺杆中的瞬态流场分布规律。所得结论可为双螺杆挤出的数值模拟研究提供一定的方法指导,并为其工程实践提供一定的理论指导。     

A comparative study of fiber breakage in compounding glass fiber-reinforced thermoplastics in a buss kneader,modular Co-rotating and counter-rotating twin screw extruders

The breakage of glass fibers was measured for several different types of continuous mixers including (i) Buss Kneader, (ii) modular intermeshing co-rotating twin screw extruder, and (iii) modular intermeshing counter-rotating twin screw extruder. Comparisons are made using different screw configurations, loadings, feeding ports, and mixing elements. Downstream feeding of glass fibers and milder screw configuration favor less breakage of glass fibers.     

3‐D non‐isothermal flow field analysis and mixing performance evaluation of kneading blocks in a co‐rotating twin srew extruder

We have developed a three‐dimensional non‐Newtonian and non‐isothermal flow analysis of the twin screw extruder (TSE) using the finite element method. This code can simulate the fully filled parts of several kinds of screw elements, such as full flight screws, kneading blocks, rotors and their combinations. A marker particle tracking analysis has also been developed to evaluate the mixing performance of the screw elements. In this paper, simulations for the kneading blocks in a co‐rotating TSE were carried out. The screw configurations are combinations of 2‐lobe kneading blocks with several stagger angles and disk widths. The effects of screw configurations on pressure and temperature distributions are examined. We also evaluate the dispersive and distributive mixing via stress magnitude and area stretch obtained by marker particle tracking analysis. Additionally, we discuss the desirable stagger, disk width and their combinations that promote the mixing performance.     

同向双螺杆捏合盘厚度对MAH接枝LDPE反应挤出过程的影响

研究了同向双螺杆挤出机中,捏合盘元件的不同厚度对低密度聚乙烯(LDPE)接枝马来酸酐(MAH)反应挤出过程的影响,并将其与常规螺纹元件进行对比。对挤出沿程中的3个位置和挤出机出口处进行取样,用滴定法测定这些样品的接枝率。结果表明,捏合盘元件所对应的样品接枝率高于常规螺纹元件,并且随着捏合盘厚度的增加,其所对应的样品接枝率下降。此外对于接枝反应而言,捏合盘元件的分布混合能力所起到的作用要高于其分散混合能力。     

同向双螺杆熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响

对啮合同向双螺杆挤出机,将捏合盘置于熔体输送段,通过改变捏合盘错列角,研究双螺杆挤出过程熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响。应用差示扫描量热仪对两相共混体系HDPE/PS的热性能进行了实验研究,结果表明:螺杆构型对共混物的相容性影响不大。同时采用扫描电子显微镜考察了HDPE/PS共混物在熔体输送段末端位置和机头末端所取试样的相态结构,研究表明:置于熔体输送段捏合盘元件错列角对共混物分散相的相畴尺寸有一定影响。     

新型同向双螺杆元件——S型元件研究（Ⅰ）——流场数值模拟

对一种作者设计的新型同向双螺杆元件－S元件进行了流场计算。建立了三维非牛顿等温流场模型。利用ANSYS软件和自行编程计算了元件流场中的压力场，挤出量，回流量，速度场，剪切速率和拉伸速度，并对S形元件的流场与常规螺纹元件的流场作了一定的比较。在后续的文章中将对S形元件的流场及常规螺纹元件的流场计算结果进行实验验证。     

阴离子聚合反应挤出过程的化学热效应

为定量分析聚合反应倾向、优化反应加工条件,在建立紧密啮合同向旋转双螺杆挤出机的反应器模型及物料的化学反应动力学模型、化学流变模型的基础上,分析了阴离子聚合反应挤出过程的化学热效应,推导出反应热的释放量与反应热强度的数值计算式,并通过算例展示了其变化特点。     

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.