Velocity measurements on a polypropylene melt during extrusion through a flat coat‐hanger die
Velocity measurements on a polypropylene melt during extrusion through a flat coat‐hanger die
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通过平衣架模头挤出期间聚丙烯熔体的速度测量
DOI：
10.1002/pen.22124
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发表时间：
2012
影响因子：
3.2
通讯作者：
Münstedt
中科院分区：
文献类型：
--
作者：
A. Grieß;Burghelea;Münstedt
采用激光多普勒测速仪（LDV）对聚丙烯熔体通过平衣架式口模挤出过程中观察到的各种流动状态进行了实验研究。LDV测量的速度分布横跨差距的模具在不同的位置沿着模具揭示了三种不同的挤出制度。在较小的壁面剪应力下，速度分布可以用对称曲线拟合，在口模壁面处速度为零。这些轮廓并不沿模具沿着均匀分布。壁面剪应力的增加揭示了第二流动状态，其特征在于速度分布沿着口模均匀分布。随着壁面剪应力的进一步增加，观察到第三种流动状态，其特征在于玻璃窗上的壁面滑移。这种流动状态的系统特征在于在不同的温度和吞吐量的滑移速度的测量。取沿模头的最大速度沿着来评估流动的均匀性，其决定性地影响挤出膜的厚度。通过在不同的生产量和温度下测量速度分布，确定了沿着模头恒定速度的条件。Polym.工程索引，2012.© 2011年塑料工程师协会
An experimental investigation of various flow regimes observed during the extrusion of a polypropylene melt through a flat coat‐hanger die by laser‐Doppler velocimetry (LDV) is presented. LDV measurements of the velocity profiles across the gap of the die at various locations along the die reveal three different extrusion regimes. At small wall shear stresses, the velocity profiles can be fitted by symmetrical curves with the velocities becoming zero at the die walls. These profiles are not uniformly distributed along the die. An increase of the wall shear stress reveals a second flow regime characterized by a uniform distribution of the velocity profiles along the die. As the wall shear stress is increased even further, a third flow regime characterized by wall slip on the glass windows is observed. This flow regime is systematically characterized by measurements of the slip velocities at various temperatures and throughputs. The maximum velocities along the die are taken to assess the uniformity of flow which decisively influences the thickness of the extruded film. By measuring velocity profiles, at different throughput, and temperatures, the conditions for constant velocities along the die were determined. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
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