共挤出机头中的聚合物熔体流动分析

采用Hele-Shaw模型对共挤出机头流道内的聚合物熔体流动进行了数值模拟分析，计算得到了衣架型机头出口处各层料流分界面的位置，并讨论了物料特性、进口处流率比对机头出口处分界面位置的影响。     

片材机头中物料温度分布的模拟分析

本文利用ANSYS和MATLAB软件,对衣架型和T型片材机头中熔体的温度分布进行三维有限元模拟和分析。通过对机头流道内温度分布的模拟,得出了衣架型机头流道的温度分布优于T型机头。     

微通道塑料薄膜挤出机头流道优化及整体设计

微通道塑料薄膜中间有数十条微通道,通过在阻尼区的出口区域斜面镶嵌注气针头成型微通道,同时借鉴衣架式挤出机头的设计经验,对影响口模出口截面速度均匀性的主要流道参数歧管扩张角、扇形区长度、阻尼区倾斜角、阻尼区高度和定型段长度等进行优化。利用正交试验设计实验方案,并用CFD软件Polyflow对实验方案进行相应建模及仿真。利用CFD-post对仿真结果进行分析,以口模出口处截面的速度均匀性指数为评价指标进行流道参数组合的优劣选取,得到最优流道参数。利用最优流道参教组合进行微通道塑料薄膜衣架式挤出机头的整体设计。     

不同角度内模填充衣架型机头的数值模拟

利用Polyflow软件对填充了不同角度内模的衣架型机头流道进行了模拟。研究了不同内模夹角对流道压力分布、出口压力、出口速度以及流道内流体停留时间的影响。结果表明:不同角度内模填充机头流道后,流道压力分布、出口压力和出口速度无明显改变;流道内物料主要停留在歧管端部;通过改变内模夹角,可以改变物料最大停留时间及停留面积,内模夹角为40°时,流道内最大停留时间短,物料停留少。     

衣架式机头

<正> 衣架式机头是介于T型机头和鱼尾式机头之间的一种挤出机头。如图1所示,衣架式机头与T型机头相比,都有一根岐管,但衣架式机头的岐管比T型机头的岐管小,熔体在机头内的停留时间短,对热稳定性较差的聚氯乙烯之类的树脂来说,采用衣架式机头进行板、膜的挤出生产,其物理力学性     

基于Poly Flow模拟分析的新型流道系统设计与分析

塑料板膜挤出机头是挤出热塑性板片材的关键性部件。设计不良几何流道将会导致口模出口挤出速度不均及物料在机头内滞留而热分解,从而引起挤出板片材的横向厚度不均及产品质量下降等问题。本文基于PolyFlow数值模拟分析,以直锥管衣架式机头为基础,提出一种新的流线型流道系统设计方法。经优化设计参数,从模拟结果中取得了良好的挤出效果。并通过了初步的实验验证。     

衣架机头的优化计算及压力分布模拟

阐述了泪滴型歧管衣架机头流道优化计算原理和压力分布模拟计算的方法,编制了CAE软件包。讨论了流道主要参数对挤出压力分布均匀性的影响,并将本计算模块应用于工业实践。从使用效果来看,这种计算方法对于机头的设计和故障诊断具有实际的指导意义,具有一定的应用前景。     

衣架式板材与片材挤出机头优化设计软件的研制

在建立合理的分配流道数学模型基础上，开发了衣架式板材与片材挤出机头优化设计软件，能方便而合理地指导设计者正确处理各影响参数，达到优化设计的目的。     

鱼尾式机头设计

<正> 一、引言目前,用于挤出塑料板的平口机头有:1.T 型机头2.鱼尾式机头3.衣架式机头4.螺杆式机头应用衣架式机头内聚合物熔融流动方程,获得机头各部分尺寸之间的关系,有关的研究结果,在本人过去的文章中,已有报导。     

线性圆锥形衣架机头设计的计算机辅助分析

基于物料在线性圆锥形衣架口模中均一流动原则，采用MATLAB软件计算并绘图，分析了口模高度，幂率指数，扇形区高度和宽度等因素对歧管半径分布和机头中压力降的影响。结果显示：对各个因素分析可以预测口模中歧管半径分布情况和压力降的变化情况，为衣架口模的设计实现了计算机辅助分析。     

Extrusion die design for slowly reacting materials

The flow distribution of slowly reacting polymeric materials inside an extrusion die was analyzed by lubrication theory. The viscosity of the polymeric liquid was assumed to be time-dependent owing to chemical reaction. Three types of extrusion dies were considered: a T-die, a linearly tapered coat-hanger die with a choker bar, and a curvilinearly tapered coat-hanger die. It was found that the T-die is not suitable to deliver the polymeric liquid films, whereas the two coat-hanger dies can deliver the polymeric liquid films with acceptable flow uniformity and residence time distribution.     

Design of Sheet Dies for Minimum Residence Time Distribution: A Review

The various die designs that have been proposed for the manufacture of sheets and flat films from polymeric materials are reviewed, along with the corresponding flow analysis and derived design equations. Successively, the T-die, the linearly tapered coat-hanger die, the curvilinearly tapered coat-hanger die (with manifold of circular or rectangular cross-section), and the fishtail die are examined. In each case, care is taken to outline the assumptions used to derive the equations, and to state the advantages and disadvantages of each design. The limits of these mentioned assumptions are explained and illustrated. Particular attention is paid to the aspects of the design which affect the processing of sensitive or reactive materials (i.e., residence time distribution and wall shear stress).     

A simple numerical approach for the optimal design of an extrusion die

A simple numerical approach that is based on the lubrication approximation is developed for the optimal design of a linearly tapered coat-hanger die. This approach does not require the analytic pressure drop / flow rate equations for flow in the manifold and in the slot section, therefore any generalized Newtonian fluid model can be easily incorporated. Example calculations have demonstrated that the predictions based on this approach are reasonably accurate as compared with those from the complete 3-D finite element simulations.     

Residence time distribution of polymer melts in the linearly tapered coat-hanger die

This article analyzes the average residence time distribution of polymer melt across the die width in a common linearly tapered coat-hanger die, which excells the T die but is a little inferior to the curvilinearly tapered coat-hanger die in residence time uniformity according to the approximated calculation of ten used. From another point of view, a linearly tapered coat-hanger die may be designed so that a desired ratio of the residence time through the die far end to that along the die center line may be imposed as one of the design constraints.     

Computer-aided analysis of a linearly tapered coat-hanger die

We describe the computer-aided engineering analysis of a linearly tapered coat-hanger die in this paper. The general governing equation for flow distribution inside the die was derived first. On the basis of this equation, we have developed the design formula for a die to deliver uniform flow. In addition, we have also examined the variations of lateral flow uniformities and residence time distributions of polymeric liquids under several different design and operating conditions: (1) using manifolds with non-circular cross-sections, (2) adjusting production widths, (3) delivering fluids with different viscosities, and (4) enlarging manifolds for practical production considerations.     

衣架式流延模头内熔体流动与模具变形的三维耦合数值模拟

利用Polyflow软件对一种衣架式流延模头内熔体的流动和模具变形进行了三维耦合数值模拟。结果表明:衣架式模头中熔体的流动可视为歧管内(沿歧管方向)和狭缝中(沿挤出方向)的压力流的组合;模头狭缝表面在模具厚度方向的变形沿挤出方向近似为线性增加,而沿模具宽度方向为非线性减小;模具变形后的熔体出口流率由狭缝的实际间隙和扇形区出口处的压力共同决定,单位宽度的出口流率沿模具宽度方向先增加后减小。     

间甲酚臭氧化反应动力学研究

本文采用停流光谱仪研究了溶解臭氧和间甲酚在液相中的均相反应动力学,探讨了反应温度为298K和pH值在3～7范围内,间甲酚臭氧化反应的动力学参数。间甲酚臭氧化总的反应呈二级,对臭氧浓度和间甲酚浓度分别呈一级。臭氧化反应速率常数随溶液pH值的增大而增大,在T为298K时,当pH值从3变化到7,总的反应速率常数从6 28×103(mol L)-1·s-1增大到9 15×105(mol L)-1·s-1。     

Simulation of polymer flow through a coat-hanger die: A comparison of two numerical approaches

Coat-hanger dies are commonly used for the extrusion of plastic sheets and films. To describe the flow of a molten polymer through a coat-hanger die, a two-dimensional approach is necessary. Moreover, the thermal effects, which play an important role in the flow distribution, have to be taken into account. In this paper, two numerical models for the simulation of coat-hanger dies are described and compared. These models differ mainly in the simplifying assumptions used and in the treatment of the thermal problem. The simulations obtained with the two models were compared with each other and with experimental data. The discrepancies between the two models can be explained by the different theoretical treatments.     

Three-dimensional modelling of Non-Newtonian fluid flow in a coat-hanger die

The three-dimensional model of isothermal flow of power-law fluid in a coat-hanger die has been developed using finite element method. The shape of coat-hanger die used in the present model was determined according to the previous analytical design equation which is based on one-dimensional flow model in the manifold and the slot. Because uniform flow rate across the die outlet is most important to achieve uniform thickness of extruded polymer sheet or film, flow rate distribution is mainly examined to determine the valid process condition for the design equation as the design parameters are changed. The effects of fluid property in terms of power-law index and process parameters not considered in one-dimensional design equation such as die inlet size and the presence of land were analyzed. Results show that the manifold angle is the most influencing design parameter on flow rate distribution. When the material of different power-law index from design value is processed, the change of power-law index affects the uniformity of flow rate appreciably.     

Numerical simulation of three-dimensional viscoelastic flow within dies

In recent years, the development of CAE (Computer Aided Engineering) in polymer processing has been remarkable, and it is expected to be more realistic in viscoelastic numerical simulation, particularly in three-dimensional complex geometry. Because of the problems of computational memory capacity, CPU time, and the numerical convergence of viscoelastic flow simulation, three-dimensional viscoelastic simulation applicable to industrial flow behaviors has not yet been attempted. In this paper, we developed the numerical simulation of three-dimensional viscoelastic flow within dies using a decoupled method, streamwise integration, and penalty function methods to decrease memory, and the TME (“Transformation of Equation of Motion to the Elliptic Equation,” S. Tanoue, T. Kajiwara, and K. Funatsu, The Eleventh Annual Meeting, the Polymer Processing Society Seoul, Korea, Extended Abstracts p.439) method, which raises the stability of convergence. We confirmed the reliability of this simulation technique to compare simulation results with experimental data of the stress field at a downstream wall shear rate of 5.41s^?1 within a 60° angle tapered contraction die. We compared the predictions of a viscoelastic model (Phan-Thien and Tanner model) with a pure viscosity model (Carreau model) at a downstream wall shear rate of 120s^?1 and discovered a remarkable effect of viscoelasticity in the shear stress and first normal stress difference in particular in the tapered region.