双螺杆挤出机的应用和发展

<正> 挤出法在塑料加工工业中占有很重要的地位,随着塑料制品的广泛应用,塑料挤出机行业得到了迅速的发展,其中双螺杆挤出机发展最快。意大利Roberto Colombo公司于本世纪30年代,研制出第一台同向转动双螺杆挤出机,紧接着Carto Paquetti     

异向旋转双螺杆挤出机的发展前景

本文通过分析螺杆在不同区段的几何特征及其对相应加工阶段的影响对平行和锥形双螺杆挤出机进行了全面的比较。     

同向双螺杆挤出机的应用及发展

本文简述了同向双螺杆挤出机的积木式设计原理及其应用,并介绍了科亚公司９９年新一代同向双螺杆挤出机的特点。     

试验用双螺杆挤出机的设计

<正> 1985年6月我厂试制成功了第一台小型双螺杆挤出机。双螺杆挤出机是多螺杆挤出机的一种,是在单螺杆挤出机基础上发展起来的。从结构来说,双螺杆挤出机是由机筒、螺杆、加热器,机头连接器,传动装置,加料装置和机座等部件组成。从性能来说,进料产量高,物料塑化好,转速     

双螺杆挤出机与反应性挤出加工技术

本文论述了双螺杆挤出机与反应性挤出加工技术的特点,介绍了其在聚合反应、聚合物可控降解、聚合物接枝及聚合物改性等方面的应用。     

同向平行双螺杆挤出机喂料系统的现状与发展

介绍用向平行双螺杆挤出机喂料系统的现状和发展。通过对同向平行双螺杆挤出机喂料系统功能与结构特点的分析研究，在总结国内外各种类型喂料机的基础上，探讨解决料斗架桥问题的方案，寻找提高喂料螺杆对物料适应性的途径，并自行设计了新型喂料系统，较好地解决了物料架桥问题。     

双螺杆挤出机

一、概述双螺杆挤出机是在单螺杆挤出机的基础上发展起来的。它是在一个双联腔的机筒里并排横放两根螺杆,故称为双螺杆挤出机,见图1。它由传动装置(包括电机、离合器、传动箱与止推轴承)、机筒、螺杆、加热器、机头连接器     

Twin screw extruders: The latest developments

This month's Plastics Additives & Compounding discusses some of the latest developments in twin screw extrusion technology for the compounding and masterbatch industries.     

Twin screw extruders as polymerization reactors for a free radical homo polymerization

The bulk polymerization of n-butylmethacrylate was investigated in a counter-rotating twin screw extruder. It appeared that the gel effect, occurring with bulk polymerizations, affected the polymerization progress very strongly. Due to this effect the conversion of the reaction is independent of the rotation speed of the screws. The reactive extrusion diagram, presented in this paper, indicates how the different phenomena interact with each other and helps to understand the influences of extruder parameters and reaction parameters on the process.     

Single screw extruders

The single screw extruder can offer a number of advantages over other continuous mixing systems such as lower costs, less maintenance and simpler operation. Pigments and additives can now be incorporated into resins to give compounds that may have filler loadings of up to 50%. New developments are now solving limitations in output, product uniformity and control. Plastics Additives & Compounding takes a look at some of the single screw extruders on the market     

Surging in screw extruders

Output uniformity is one of the main factors limiting the maximum output obtainable from a single screw plasticating extruder, and is adversely affected by surging. Several causes of surging have been identified, perhaps the most important being instabilities in the melting process. These are caused by periodic break-up of the bed of compacted solid polymer formed in the screw channel. Solid bed break-up is shown, both experimentally and theoretically, to be associated with rapid acceleration of the bed in the downstream direction parallel to the screw flight. A novel method of measuring solid bed velocity and hence acceleration is described. The theoretical model of the melting process is shown to be capable of predicting this acceleration reliably, and therefore the tendency for a particular combination of screw design, material and operating conditions to cause surging.     

Scale-up of single screw extruders

Scale-up from small laboratory size extruders to large production size extruders is a procedure of great practical importance. Many scale-up rules and theories have been proposed in the past, however it is not always clear how the different scale-up methods will affect extruder performance. A basic analysis of scale-up in plasticating single screw extruders is developed from which the effect of a certain scale-up strategy on extrusion performance can be evaluated in terms of solids conveying, melting, melt conveying, mixing, residence time, heat transfer, power consumption, and specific energy consumption. Various existing scale-up theories are evaluated and compared using the basic analysis. A number of existing scale-up theories have some significant drawbacks, in particular with non-constant specific energy consumption and imbalance between melting rate and pumping rate. Conditions that are desirable to achieve in scale-up are enumerated and ranked in terms of importance. This leads to two new scale-up methods that result in constant mechanical specific energy consumption and high throughput rates. The first scale-up method keeps the specific surface area constant. This scale-up should work well for high values of the Brinkman number. However, at low values of the Brinkman number, the melting rate may be insufficient. The second scale-up method keeps the melting rate at low Brinkman number equal to the pumping rate and, thus, should be useful in cases where the first scale-up method cannot be used.     

Melting in single screw extruders

A model for the melting of granules in a single screw extruder is presented in Part I. It is consistent with observations of earlier workers and retains some of the ideas introduced by Tadmor in his model; however, it assumes that the solid bed of granules cannot stand large differences of principal stresses and so account has to be taken explicitly of the downstream force balance on the solid bed and in the melt pool. Detailed quasi-analytic results are given for a Newtonian (constant viscosity) fluid in Part II. These illustrate the model for a particularly simple case and have relevance for some materials. A more elaborate numerical scheme is described in Part III for a non-Newtonian model and results are presented for comparison with the predictions of other theories and with experiments.     

Melting in single screw extruders

A model for the melting of granules in a single screw extruder is presented in Part I. It is consistent with observations of earlier workers and retains some of the ideas introduced by Tadmor in his model; however, it assumes that the solid bed of granules cannot stand large differences of principal stresses and so account has to be taken explicitly of the downstream force balance on the solid bed and in the melt pool. Detailed quasi-analytic results are given for a Newtonian (constant viscosity) fluid in Part II. These illustrate the model for a particularly simple case and have relevance for some materials. A more elaborate numerical scheme is described in Part III for a non-Newtonian model and results are presented for comparison with the predictions of other theories and with experiments.     

Power for multi-section melt screw extruders

Theoretical equations for power dissipation and torque for single and multi-section screw extruders for Newtonian or slightly non-Newtonian melts are derived from improved theoretical velocity distributions. Verification of the equations is indicated by experimental data for four single-section screws of constant channel depth. The power equations can be easily programmed on a digital computer for design or evaluation.