Conception of a measuring methodology for the degradation behavior of polypropylene and polystyrene in the extrusion process

在聚合物加工领域，聚合物被塑化，以便能够将其加工成最终产品或半成品。聚合物的加工通常是在螺杆机上进行的。例如挤出机和注塑机。在这类螺杆机的加工过程中，材料会受到很高的热应力和机械应力。这种负荷会以分子质量降解的形式导致材料性质的变化。这种分子质量的降解也会导致聚合物的力学和化学性质的变化。在前面的聚丙烯(PP)和聚苯乙烯(PS)的DFG项目中详细研究了分子质量的降解。在这种情况下，材料退化被转换为数学模型，从而能够计算加工引起的材料退化。该模型基于三个降解参数，每个材料都必须知道这三个参数：停留时间敏感性、剪切速率敏感性和温度敏感性。这些参数必须通过实验室测试系列和随后针对每种材料类型的回归来确定。实验研究表明，与类型有关的材料参数的确定是不够的。即使观察几种类型的聚丙烯，在停留时间、温度和剪切速率方面的敏感性也不相同。这可能是由于不同材料类型的稳定性不同所致。因此，有必要确定每一种材料的材料特性，以便能够对材料退化进行充分计算。由于这些参数的确定非常耗时，因此目前计算材料退化是不经济的。这项研究项目的目的是开发一种快速测量所需材料灵敏度的可能性。这应该与KAUTEX Maschinenbau GmbH公司合作完成。要开发的测试方法理想情况下应该能够在几个小时内确定降解参数。这将大大增加数学计算的适用性。在第一步，必须在先前项目的基础上选择合适的测量方法来确定所需的材料参数。此外，它们的可用性还需要测试。在此基础上，将开发一种测量方法，该方法最初将能够快速可靠地确定材料降解参数。这一测量概念应该转化为原型。测量结果将在实验数据的基础上进行验证，并将测试测量方法对其他材料的适用性。

In the field of polymer processing, polymers are plasticized in order to be able to process them into end products or semi-finished products. The processing of polymers is often carried out on screw machines. Examples are extruders and injection moulding machines. During processing on such screw machines, the material is subjected to high thermal and mechanical stress. This load can lead to a change in the properties of the material in the form of a molecular mass degradation. This molecular mass degradation can also lead to changes in the mechanical and chemical properties of the polymer.The degradation of the molecular mass was investigated in detail in the preceding DFG project for polypropylene (PP) and polystyrene (PS). In this case, the material degradation was converted into a mathematical model, which enables the calculation of material degradation caused by processing. The modeling is based on three degradation parameters, which have to be known for each material: the residence time sensitivity, the shear rate sensitivity and the temperature sensitivity. These parameters have to be determined by laboratory test series and a subsequent regression for each material type. Experimental investigations have shown that a type-related determination of the material parameters is not sufficient. Even when looking at several types of polypropylene, the sensitivities in terms of residence time, temperature and shear rate are not identical. This is presumably due to a different stabilization of the different material types. Therefore it is necessary to determine the material characteristics for each individual material in order to enable an adequate calculation of the material degradation. Since the determination of these parameters is very time-consuming, it is currently not economical for the calculation of material degradation. The aim of this research project is to develop a possibility for the fast measurement of the required material sensitivities. This should be done in cooperation with the company KAUTEX Maschinenbau GmbH. The test method to be developed should ideally enable to determine the degradation parameters within a few hours. This would significantly increase the applicability of mathematical calculation.In the first step, suitable measuring methods for determining the required material parameters have to be selected based on the previous project. Also their usability needs to be tested. Based on this, a measurement methodology is to be developed which will initially enable a fast and reliable determination of the material degradation parameters. This measurement concept should be transferred into a prototype. The measurement results will be validated on the basis of experimental data and the applicability of the measurement methodology to other materials will be tested.