Improved Description of Elongational Flow Behavior During the Processing of Highly Filled Plastics

高填充塑料加工过程中拉伸流动行为的改进描述

• 批准号: 435000494
• 负责人: Professor Dr.-Ing. Christian Bonten
• 金额: --
• 依托单位: Institut für Kunststofftechnik (IKT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/435000494?language=en
• 关键词: Improved; Description; Elongational; Flow; Behavior

The modification of existing technical thermoplastics with active fillers, functional fillers or inactive fillers is a cost efficient and commonly used approach for property adjustments. Hereby is blending of different polymers with fillers a crucial step to develop new plastics in modern plastic processing. The aim of the modification is always a change of physical properties. Active fillers are able to enhance the mechanical properties whereas elastic fillers are able to enhance the elongational behavior. A high homogeneity of all modifiers in the polymer is essential to achieve the desired performance. According to the current state of the art, the same phenomenon of yielding at low shear rates is shown with additives of different geometry, quantity and type. From a threshold value of a certain concentration and at low shear rates, it seems that a structure of the particles, a so-called particle network, is set up which counteracts the flow and significantly increases the pressure requirement of a machine. It is expected that this flow inhibition also set under extensional strain. However, it is likely to be at a different concentration than under shear stress. The destruction of the network under extensional strain is expected at higher deformation rates.The aim of this proposal is to investigate the assumptions shown above experimentally and to describe the differences in shear and extensional flow in a general model. The influence of additives on the strain hardening, such as for long-chain branched polypropylenes needs to be examined as well. On the one hand, the differences in shear and extensional flow of highly filled polymers may be summarized in dependence of the particle concentration, particle shape and the deformation rate using the Trouton ratio. On the other hand, the differences in shear as well as in elongational flow can be described by a function of time as well as strain rate of the viscosity function. The selected model has to be extended concerning yielding and viscosity changes due to the influence of additives. In addition to the modeling above, an analytical method (such as Cogswell) needs to be developed with which the extensional viscosity can be determined directly from capillary rheometer measurements. This provides easy access to elongational data for both unfilled and filled plastics from capillary rheometer measurements.After a successful project, the established model is intended to generally predict the behavior of highly filled plastics in elongational flow and thus improve the design of the tools, better estimate the pressure requirements of the machine and to more accurately predict the processing behavior in general.

用活性填料、功能填料或非活性填料对现有技术热塑性塑料进行改性是一种经济有效且常用的性能调整方法。因此，将不同聚合物与填料混合是现代塑料加工中开发新塑料的关键步骤。改性的目的始终是改变物理特性。活性填料能够增强机械性能，而弹性填料能够增强伸长行为。聚合物中所有改性剂的高度均匀性对于实现所需的性能至关重要。根据现有技术，不同几何形状、数量和类型的添加剂在低剪切速率下表现出相同的屈服现象。从一定浓度和低剪切速率的阈值开始，似乎建立了一种颗粒结构，即所谓的颗粒网络，它抵消了流动并显着增加了机器的压力要求。预计这种流动抑制也会在拉伸应变下发生。然而，它的浓度可能与剪切应力下的浓度不同。在较高的变形率下，预计网络在拉伸应变下会被破坏。本提案的目的是通过实验研究上述假设，并描述一般模型中剪切流和拉伸流的差异。添加剂对应变硬化的影响（例如对于长链支化聚丙烯）也需要进行研究。一方面，高填充聚合物的剪切和拉伸流动的差异可以根据颗粒浓度、颗粒形状和使用特劳顿比的变形率来概括。另一方面，剪切力和拉伸流动的差异可以通过时间函数以及粘度函数的应变率来描述。由于添加剂的影响，所选模型必须针对屈服和粘度变化进行扩展。除了上述建模之外，还需要开发一种分析方法（例如 Cogswell），可以通过毛细管流变仪测量直接确定拉伸粘度。这样可以通过毛细管流变仪测量轻松获取未填充和填充塑料的伸长数据。项目成功后，建立的模型旨在总体预测高填充塑料在伸长流动中的行为，从而改进工具的设计，更好地估计机器的压力要求，并更准确地预测总体加工行为。