Simulation of the development of the microstructure of injection-moulded semi-crystalline thermoplastics by means of a multi-scale approach under consideration of shear-induced crystal forms (alpha and beta)

在考虑剪切诱导晶型（α 和 β）的情况下，通过多尺度方法模拟注塑半结晶热塑性塑料的微观结构的发展

• 批准号: 408012354
• 负责人: Professor Dr.-Ing. Christian Hopmann
• 金额: --
• 依托单位: Institut für Kunststoffverarbeitung (IKV) in Industrie und Handwerk an der RWTH Aachen
• 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 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/408012354?language=en
• 关键词: Simulation; development; microstructure; injection; moulded

Semicrystalline thermoplastics have partially spherical spherulitic microstructure. Despite the geometrical similarity of all spherulites, there are three distinct forms (α-, β- and γ-form) that arise from unique unit cells. This results in different local mechanical, thermal and optical component properties. The α-form represents the predominant crystal modification. In general, the lamellae are formed in the form of folded chains in the crystallization of semi-crystalline homopolymers in a quiescent melt. Isotactic polypropylene (iPP) in the α-form shows the unique phenomenon that lamellae are arranged in a so-called "cross-hatched" structure. The β-form has a lower degree of order compared to the α-form, which results inter alia in a higher degree of crystallization and a lower melting point. The formation of the crystalline regions of the β-form can be promoted by the addition of nucleating agents, by the choice of thermal conditions as well as by shear stress. The formation of crystallites of the γ-form occurs relatively rarely in industrially produced components and only in small proportions. It should be noted that the developed model at IKV for describing the crystallization process can not distinguish between different crystal forms. Which means all spherulites are considered the same and in the α-form, which does not correspond to reality, since the influence of β-spherulites are neglected. In the scientific literature, no work or approach is known which simulates the crystallization process in an injection-moulded component made of semicrystalline thermoplastics taking into account the different crystal forms.The aim of this project is the simulation of microstructure formation taking into account the shear-induced crystallization and consequently two dominating crystal forms (α and β) to calculate realistic microstructures and thus to precisely predict the component properties. To this end, the developed model at the IKV will be adapted so that unique nucleation and growth models for each crystal form will be derived and the calibrated using experimental experiments. These models are then implemented in the software SphäroSim, developed at IKV. The boundary conditions for the microstructure simulation come from filling simulation results based on a self-developed approach that describes the boundary conditions with a high resolution. The simulated microstructure will be then compared with the components, which will be produced under the same injection moulding process, and verified.

半结晶热塑性塑料具有部分球形球晶组织。尽管所有球晶的几何形状都很相似，但它们有三种不同的形式（α-、β-和γ-），它们都是由独特的单位细胞产生的。这导致了不同的局部机械、热和光学元件特性。α-型是主要的晶体改性形式。一般情况下，在半晶均聚物在静止熔体中结晶时，片层以折叠链的形式形成。α-型等规聚丙烯（iPP）表现出片层呈“交叉孵化”结构排列的独特现象。与α-相比较，β-相的有序度较低，其结晶度较高，熔点较低。通过加入成核剂、热条件的选择以及剪切应力的作用，可以促进β-型结晶区域的形成。γ-型晶体的形成在工业生产的成分中相对较少，而且只占很小的比例。应该指出的是，IKV开发的用于描述结晶过程的模型不能区分不同的晶体形式。这意味着所有的球晶都被认为是相同的α-形式，这与现实不符，因为忽略了β-球晶的影响。在科学文献中，没有已知的工作或方法来模拟由半结晶热塑性塑料制成的注射成型部件的结晶过程，并考虑到不同的晶体形式。该项目的目的是模拟微观结构的形成，考虑到剪切诱导结晶和两种主要的晶体形式（α和β），以计算真实的微观结构，从而精确预测组件的性能。为此目的，将对IKV开发的模型进行调整，以便为每种晶体形式推导出独特的成核和生长模型，并使用实验实验进行校准。然后在IKV开发的软件SphäroSim中实现这些模型。微观结构模拟的边界条件来自于充填模拟的结果，该方法基于一种高分辨率描述边界条件的方法。然后将模拟的微观结构与在相同注塑工艺下生产的部件进行比较，并进行验证。