L型片材挤出机头流道速度分布三维有限元分析

利用大型有限元计算软件ANSYS进行以三维模型为基础的L型机头内部流动速度分析和模拟研究。通过顺次截取沿挤出方向上 4个不同区域的速度分布图和 7个截面中间层节点横向速度分布曲线 ,分析了物料在L型片材挤出机头中的流动分布情况 ,即物料在机头内部经过几次速度调整逐步达到横向速度分布基本均匀     

L型宽幅挤出机头挤出稳定性研究

通过ANSYS软件对L型宽幅挤出机头流道三维非等温流场进行数值模拟,分析高分子物料在非等温挤出过程中的流场规律,探讨机头流道壁面温度、进料口压力、阻尼宽度和阻尼高度等参数对机头流道内物料流动的影响规律。结果表明:阻尼宽度对物料具有明显的调压作用;机头流道参数对物料挤出压力和挤出均匀性的影响趋势不同,当壁面温度为338～343 K、进料口压力为15.0～19.6 MPa、阻尼宽度为8 mm、阻尼高度为3 mm时,物料挤出均匀性和稳定性较好,可实现高分子片材挤出质量和挤出产量的平衡。     

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。     

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。     

直圆锥形衣架机头非等温三维流场的数值模拟

选用Carreau和近似Arrhenius二种数学模型，提出假设条件，利用Polyflow软件对直圆锥型衣架机头内的流场进行三维非等温有限元模拟和分析，得到不同截面上不同层面的速度、压力和温度分布曲线图。根据分布曲线图进行分析处理，总结得出熔体在机头内的运动规律及特点。     

衣架式机头内流道的设计

衣架式机头,是常用的挤板机头,本文介绍的,是支管渐变型衣架式机头内流道的设计方法。这种机头,在流道内有一定数量的存料,对料流有稳压作用,然而,与支管式机头相比,总存料量较少,减少了物料在机头内的停留时间。此外,在这种机头内,不论物料经过哪一个特定部位,它在机头内的总停留时间,总是一样的,有效地避免了物料在机头内的滞留分解。所以,这种机头,可以适用于各种树脂,特别适用于硬聚氯乙     

遗传算法在L型机头优化设计中的应用

阐述了遗传算法在L型机头设计中的应用,并编制了相应的计算软件包.讨论了L型机头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具有实际的指导意义,具有一定的应用前景.     

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。     

片材机头内聚合物熔体流动的模拟分析

利用ANSYS和MATLAB软件,对缩放型片材机头中熔体的速度、压力和剪切应力的分布进行三维有限元模拟和分析。通过对机头流道不同截面处熔体场量分布的模拟,探知了熔体在流道内的运动规律及特点。     

计算机Pro/E软件设计鱼尾式片材模具

本文利用计算机Pro/E设计软件进行鱼尾式片材挤出模具的设计,利用软件中的塑料顾问,对物料在鱼尾式机头流道内的流场进行模拟:并通过改变扇形区阻流块高度与长度,对物料在模具中熔体流动时机头内熔体压力和出口速度均匀性的影响进行了分析和讨论;这对实际挤出模具的设计具有一定的指导意义。     

鱼尾型机头中熔体流动的三维流场分析

本文利用ANSYS和MATLAB软件，对鱼尾型片材机头中熔体的速度、压力、剪切应力和粘度的分布进行三维有限元模拟和分析。探知了熔体在流道内的运动规律及特点并分析其原因，对口模设计具有定的指导作用。     

LDPE熔体在不同角度圆锥口模的挤出流变分析

深入讨论了聚合物熔体在不同角度圆锥口模的挤出胀大现象及机理,利用生产用挤出机进行不同角度的圆锥口模挤出实验,结果表明,圆锥口模挤出过程中,熔体在收敛流道受到拉伸流变,导致强烈的人口弹性效应,表现出显著的挤出胀大。通过实验研究进一步发现,不同的口模人口角对实验材料表现出不同的Bagley校正因子和可回复弹性应变。     

Numerical simulation of a single-screw plasticating extruder

A fully-predictive steady-state computer model has been developed for a single-screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt-conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature- and shear-rate-dependent viscosity equation is used to describe the melt-flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single-screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High- and low-density polyethylene resins were used.     

LDPE熔体在双螺杆挤出机中流动的有限元分析

利用大型有限元分析软件包ANSYS分析了低密度聚乙烯(LDPE)在双螺杆挤出机三头常规螺纹元件中的流动情况,讨论了整个流道的速度分布、压力分布、粘度分布及螺杆挤出特性曲线。计算结果表明：LDPE熔体在双螺杆挤出机中得到了充分的混合。     

Residence time distribution of a pharmaceutical grade polymer melt in a single screw extrusion process

The residence time distribution (RTD) of a flowing polymer through a single screw extruder was studied. This extruder allows injecting supercritical carbon dioxide (scCO₂) used as physical foaming agent. The tested material is Eudragit E100, a pharmaceutical polymer. RTD was measured at various operating conditions and a model describing RTD has been developed. High screw speed or high temperature implies short residence time, but these parameters do not have the same effect on polymer flow. In the flow rate range studied, scCO₂ has no significant influence. A mathematical model consisting of a plug flow reactor in series with a continuous stirred tank reactor (CSTR) cross-flowing with a dead volume fitted well the experimental data.     

Temperature profiles for polymer melts in tube flow. Part II. Conduction and shear heating corrections

A temperature probe system to measure radial temperature profile of polymer flowing in a rod die and a method to systematically correct the conduction and the frictional shear effects were developed. Experimental data obtained on a 1-1/2-inch extruder using a blow molding compound show that both conduction and frictional shear heating effects are significant in melt temperature measurement and that the radial temperature profiles of the melt in the rod die are influenced by the RPM of the screw and the die-wall temperature. The reliability of the temperature data obtained was compared with the solution obtained from the equations of motion and energy. A good agreement between the predicted versus experimental temperature profile exists. For this polymer system, the relationship between local Nusselt number and the velocity parameter could be adequately described with the theory of Van LeeuWen.     

Controlling the structure of a porous polymer by coupling supercritical CO2 and single screw extrusion process

A study on the extrusion of Eudragit E100 was carried out using supercritical carbon dioxide (scCO₂) as plasticizer and foaming agent. ScCO₂ modifies the rheological properties of the material in the barrel of the extruder and acts as a blowing agent during the relaxation when flowing through the die. For experiments, a single‐screw extruder was modified to be able to inject scCO₂ within the extruded material. The aim is to determine a correlation between operating conditions and foam structure. The effect of three parameters was studied: the temperature in the die and in the metering zone, the screw speed, and the volumetric flow rate of CO₂. An increase in temperature enhances the expansion rate and the average pore diameter and appears to be the most significant parameter. The effect of CO₂ concentration is significant at small concentrations only: the higher the CO₂ concentration, the lower the pore density and the higher both the pore diameter and the expansion rate. The effect of the screw speed is tricky because a variation of this speed involves a decrease of CO₂ weight ratio. This study shows that the structure of the extrudates does not evolve with a coupling of screw speed increase and a subsequent CO₂ weight ratio decrease. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of supercritical carbon dioxide on polystyrene extrusion

A study on the extrusion of polystyrene was carried out using supercritical carbon dioxide (scCO₂) as foaming agent. scCO₂ modifies the rheological properties of the material in the barrel of the extruder and acts as a blowing agent during the relaxation at the passage through the die. For experiments, a single-screw extruder was modified to be able to inject scCO₂ within the extruded material. The effect of operating parameters on material porosity was studied. Samples were characterized by using water-pycnometry, mercury-porosimetry and scanning electron microscopy. Polystyrene with expansion rate about 15–25% was manufactured. A rapid cooling just downstream the die is important to solidify the structure. The die temperature allows the control of the porosity structure. CO₂ concentration shows no significant influence.     

Influence of molecular parameters on material processability in extrusion processes

A viscosity model showing a direct correlation between molecular weight distributions and shear thinning behavior of polymeric melts was used in 3D numerical simulations of an extrusion process. The equipment analyzed was a single screw extruder with an annular die attached. The material of choice in the simulations was polystyrene in a range of molecular weights and degrees of polydispersity. The influence of material parameters (molecular weight and polydispersity) on the system operating point, power consumption and residence time distribution was analyzed. The results were generalized and a window of processing conditions for resins with different properties was analyzed. The effect of blending homologous polymers with different molecular parameters on material processability was also presented. The model can be extended to other materials and various processing equipment.