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，以便能够加工成最终产品或半成品。聚合物的加工通常在螺旋机上进行。例如挤出机和注塑机。在这种螺旋机上加工时，材料受到很高的热应力和机械应力。这种负荷会导致材料的性质以分子质量退化的形式发生变化。这种分子质量的退化也会导致聚合物的机械和化学性质的变化。在之前的DFG项目中，对聚丙烯（PP）和聚苯乙烯（PS）的分子质量降解进行了详细的研究。在这种情况下，将材料退化转化为数学模型，从而可以计算加工引起的材料退化。该模型基于三个降解参数，这三个参数必须为每种材料所知：停留时间灵敏度、剪切速率灵敏度和温度灵敏度。这些参数必须通过实验室测试系列和对每种材料类型的后续回归来确定。实验研究表明，材料参数的类型相关的确定是不够的。即使在观察几种聚丙烯时，在停留时间、温度和剪切速率方面的敏感性也不相同。这大概是由于不同材料类型的稳定性不同。因此，有必要确定每种材料的材料特性，以便能够充分计算材料的降解。由于这些参数的确定非常耗时，目前对材料降解进行计算并不经济。本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。所要开发的测试方法最好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。在第一步中，必须根据之前的项目选择合适的测量方法来确定所需的材料参数。它们的可用性也需要测试。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。这个测量概念应该被转移到原型中。测量结果将在实验数据的基础上进行验证，并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.