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.     

Modeling of a Buss‐Kneader as a polymerization reactor for acrylates. Part I: Model validation

The Buss‐Kneader is generally known as a compounding device. Although a reasonable number of papers have been published on extruders as polymerization reactors, only little is known about the behavior of the Buss‐Kneader when used as a polymerization reactor. Its good mixing properties in the radial and axial directions make it a suitable reactor for exothermal polymerization reactions. This paper describes experiments with the co‐polymerization of n‐butyl acrylate and hydroxyethyl methacrylate in a Buss‐Kneader. For model calculations the Buss‐Kneader was treated as a plug flow reactor with axial dispersion. Experimental results on axial temperature profile, monomer conversion and molecular weight are compared with model calculations. Model parameters are based on independently measured data on the heat transfer coefficient, axial dispersion and polymerization kinetics.     

A comparative study of dispersing a polyamide 6 into a polypropylene melt in a Buss Kneader,continuous mixer,and modular intermeshing corotating and counter‐rotating twin screw extruders

We have made a study of the development of phase morphology of an immiscible blend(75/25)(polypropylene–polyamide‐6) for different types of continuous mixers including (i) Buss Kneader, (ii and iii) modular intermeshing corotating and counter‐rotating twin screw extruders, and (iv) NEX‐T Kobelco Continuous Mixer. Comparisons are made using different screw configurations for each machine. Generally, in comparison of the different machines, the intermeshing counter‐rotating twin screw extruder produced the finest dispersed morphology. Using a droplet breakup kinetic model, we interpreted the blend dispersed phase droplet breakdown rate and coalescence rate. In comparison with our earlier study of the continuous mixing of agglomerates of CaCO₃ particles the polymer droplet breakup rate was smaller than that of the particle agglomerates and the coalescence rates of droplets were many times greater than the particle reagglomerates rates. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Development of The Modern Buss Kneader and The Study of Its Flow and Mixing Mechanisms

The development of the modern modular Buss Kneader from its origins is described. We also summarize experimental studies of the characteristics of this machine. Finally, we review efforts at simulation of flow and design analyses for the Buss Kneader.     

A study of residence time distribution in co‐rotating twin‐screw extruders. Part I: Theoretical modeling

A theoretical model to determine the residence time distribution (RTD) in a co‐rotating twin‐screw extruder is proposed. The method consists of coupling a continuum mechanics approach with a chemical engineering one and allows us to obtain the RTD without any adjustable parameter. The process parameters are obtained using Ludovic® twin‐screw modeling software, and ideal reactors are chosen to depict the screw profile. The influence of screw speed, feed rate and viscosity on RTD are described on a fictive screw profile. The predictions of the model are in qualitative agreement with literature data. The key point of this procedure is obviously the correct association between an ideal reactor and a screw element.     

Modeling of a Buss‐Kneader as a polymerization reactor for acrylates. Part II: Methyl methacrylate based resins

The Buss‐Kneader has proven to be a suitable reactor for the polymerization of acrylates. In this second part, the polymerization of methyl methacrylate and the ter‐polymerization of methyl methacrylate (MMA), hydroxyethyl methacrylate and n‐butylmethacrylate is carried out in a pilot Buss‐Kneader. The reactor had to be pressurized up to about 10 bars to avoid evaporation of MMA. Instabilities in output rate and temperature profiles were observed as a result of fluctuating die pressures. Because of good mixing there may be no diffusion limitation for radicals. As a result, even at high conversions, no gel effect was observed.     

Reactive extrusion of recycled bottle waste material

The objective of this study is to investigate the effect of reactive processing of commingled bottle waste polymer in an extruder. A variety of peroxides and monomers were tested to assess their influence on the final mechanical properties of the product. The reactive extruded polymer blends were prepared in two types of extruders: a co‐rotating twin‐screw extruder and a Buss co‐Kneader single‐screw extruder. Blends were analyzed for mechanical and thermal properties. The effectiveness of the different monomers and peroxides was evaluated in terms of improvement in impact properties. It has been found that the toughness of the polymer blend is improved by reactive processing. Depending on the amount and type of reactants, the impact strength can be improved by 220%, with a slight reduction in the modulus compared to an unmodified physical blend. The most suitable monomers were n‐butylmethacrylate (BMA), t‐butylamino ethylmethacrylate (TBAEMA) and a combination of styrene/maleic anhydride (ST/MAH). The peroxide should have a short half‐lifetime compared to the average residence time in the extruder. The most effective monomers have a high initial reactivity and low rate of evaporation at the processing conditions used. Changes in processing conditions in the extruder influence the reaction conditions and therefore the final properties of the blend. Results were interpreted in terms of residence time, melting profile and peroxide concentration.     

工作参数对2.4m幅宽中央进料式螺杆分配机头内部流场的影响

运用ANSYS的二次开发语言APDL建立了参数化的2.4 m幅宽螺杆分配机头的几何、有限元模型,并生成了宏文件。对分配螺杆的歧管部分采用自由划分网格,狭缝型流道则采用规则的六面体映射网格。借助于ANSYS有限元软件对2.4 m幅宽中央进料式螺杆分配机头内的流场进行了三维模拟分析,比较了入口压力的变化、分配螺杆的转速对机头内部压力场、速度场的影响。分析得出,入口压力值降低有助于机头内的压力均匀分布,增加螺杆转速有助于提高机头内的压力分布的均匀性。     

基于Pro/Engineer的挤出机螺杆三维参数化模块开发

采用参数化设计的方法,在Pro/E中进行二次开发,建立了单螺杆元件的参数化造型和装配模块。利用此模块,用户可以快速地创建单螺杆模型,进行CAE分析。     

Measurement of three-dimensional velocity field in the translational region of a co-rotating twin-screw extruder

The velocity field in the screw channels of a co-rotating twin-screw extruder was measured using laser Doppler anemometry. Velocity distributions were measured for two screw elements having pitches of 14 and 28 mm, respectively. The magnitude of radial velocity component for both elements was no more than 10% of the magnitude of total velocity. The radial and the axial velocity components were similar for both screw elements. Wider range of tangential velocity values and steeper gradients near the flights were observed for smaller pitch screw element.     

注塑机螺杆头三维等温流场的数值模拟

使用Polyflow软件建立注塑机两种螺杆头的三维流道模型,并采用机筒静止、螺杆旋转及进行周期性往复运动的运转条件进行等温数值模拟,求解出了各自流道内的速度场、压力场和剪切应力场。对数值模拟结果的分析表明,有螺纹的螺杆头能更好地减少PVC熔料的停滞热解,增强塑化作用,但是与无螺纹螺杆头相比在防止熔料倒流方面略显不足。     

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。     

脱挥型双螺杆挤出机螺杆组合构型对脱挥效果的影响

通过脱挥理论的分析得出螺杆组合影响脱挥效果的原因,从传质面积、停留时间和剪切速率3个方面对纯螺纹元件组合和带开槽元件组合进行了比较,并在实验中比较了脱挥段分别设置两种组合的脱挥效果,结果表明:螺杆组合对脱挥效果的影响十分明显,在脱挥段设置带有开槽螺纹元件的组合比设置纯螺纹元件组合脱挥效果更好。     

数值模拟研究螺纹元件的混合性能

使用FEM方法数值模拟了同向双螺杆螺纹混合元件和普通螺纹元件流道中硬聚氯乙烯的流动过程,计算了2种螺纹元件流道内熔体的非等温流场,使用粒子示踪法统计分析了2种螺纹元件流道内熔体的混合性能.研究结果表明,螺纹混合元件具有较均匀的剪切速率分布、较平缓的温度分布和较强的分散与分布混合能力,但是其输送能力较小.     

新型螺杆挤出机螺杆强度的有限元分析

介绍了一种新型螺杆挤出机的原理及结构特点。对该新型挤出机的外螺杆建立了符合实际尺寸与形状的有限元模型，利用ansys有限元软件对其进行了应力分析。研究结果表明，安全系数达到3时。承受内外压力的特殊结构外螺杆危险截面的内外表面处。各主要应力值均小于许用应力，强度符合要求。从理论上证明了该螺杆在新的工作载荷条件下具备正常运转的能力。为该新型挤出机进一步的开发提供了保证，同时证明了有限元方法在强度分析中是可靠且高效的。     

啮合同向双螺杆驼峰元件的数值模拟

介绍了啮合同向双螺杆驼峰元件的特点,应用Polyflow软件进行了流场模拟,并与双头螺纹元件进行了比较分析。模拟结果显示:驼峰元件的螺棱和机筒之间的剪切速率比双头螺纹的低;建压能力比双头螺纹元件高;回流量较大,轴向混合能力较强。特别适用于生物降解塑料等热敏性和剪敏性塑料的高速挤出和混合。     

啮合同向双螺杆挤出过程非啮合开槽螺纹元件组合流道三维流场分析

应用ANSYS有限元分析软件对啮合同向双螺杆挤出过程包括非啮合多过程螺纹元件（NI-MPE）组合流道进行了等温非牛顿三维流场模拟分析，得到了包括NI-MPE元件的组合流道的压力场、速度场、剪切速率场和剪切应力场，并与包括非啮合常规螺纹元件的组合流道的模拟结果进行了对比。     

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。     

离心力作用下螺旋推进器强度分析

建立了卧式螺旋卸料沉降离心机螺旋输送器的参数化的三维有限元分析模型,进行了离心力作用下的螺旋输送器强度分析。采用五因素四水平的正交试验法,找出了影响螺旋推进器强度的主要因素。经多变量拟合,得到了离心力作用下螺旋推进器的强度计算公式。