Effects of grooves on processing conditions within grooved plasticizing units in single screw extrusion

单螺杆挤出是大规模低成本生产塑料制品的重要生产工艺。传统的单螺杆挤出机是由一个带有三个加工区的输送螺杆和一个光滑的机筒组成的。今天，带有凹槽进料区和/或挡板螺丝的变种是最先进的，并被广泛使用。由于在使用槽式喂料挤出机时，喂料区通常会发生磨损，熔化速度低，混合性能差，因此在过去几年中，将连续槽筒与屏障螺杆相结合的使用获得了发展。凹槽塑化区挤出机具有压力分布均匀、磨损小、运行节能、熔体温度低等特点，虽然传统挤出机已建立了熔融流动模型，但其有效性及其在凹槽塑化区的应用尚未得到研究。现有的模型概念只是基于假设和经验，缺乏科学的验证。因此，本项目的目的是详细检查沟槽对工艺的影响。将开发一种模型，能够对带槽塑化单元内发生的事情进行解析或简单的数值描述(例如，有限差分)。首先，使用可拆分挤出筒和螺杆模拟器进行的实验研究将深入了解沟槽对熔融和流动行为的影响程度。将使用基于超声波技术的在线测量来研究温度和停留时间的分布。研究结果将有助于对现有模型概念的修正和调整。随后，新改进的模型将被数学描述并被实施到仿真工具中。最后一组参考实验被用来最终验证该模型。因此，在这个项目中要达到的结果是加深和改善对凹槽塑化区内的熔融和流动过程的了解。在计算模型中的应用将允许描述和预测这些过程，以改进连续槽单螺杆挤出机的设计。

Single-screw extrusion is an important production process for large-scale plastic product manufacturing at low cost. Conventional single-screw extruders are a combination of a conveying screw with three processing zones and a smooth barrel. Today, variants with grooved feed zones and/or barrier screws are the state of the art and widely used. Due to the typical occurrence of wear in the feed zone, low melting rates and poor mixing performance when using grooved feed extruders, the use of continuously grooved barrels in combination with barrier screws has gained momentum within the last years. Extruders with a grooved plasticizing zone have since proved to feature uniform pressure profiles, little wear, energy efficient operation and low melt temperatures.Whereas melting and flow models are well established for conventional extruders, their validity and application for grooved plasticizing zones so far has not been investigated. The existing model concepts are based on assumptions and experience only, which lack scientific validation. Thus, the aim of this project is a detailed examination of the grooves influence on the process. A model will developed, enabling an analytical or simple numerical description (e. g. with finite differences) of what happens within a grooved plasticizing unit. First, experimental studies with a dividable extrusion barrel as well as a screw simulator will give insight to which extent the grooves affect the melting and flow behavior. Inline measurements based on ultrasound technology will be used in order to investigate the temperature and residence time distribution. The results will help to revise and adjust the current model concepts. Subsequently, the newly improved model will then be described mathematically and implemented into a simulation tool. A final set of reference experiments is used to conclusively validate the model. Therefore, the result to be achieved within this project is a deepened and improved understanding of the melting and flow processes within grooved plasticizing zones. The application within a computational model will allow describing and predicting these processes for improved design of continuously grooved single-screw extruders.