In-situ analysis of microstructure development and powder aging during powder bed fusion of plastics using dielectric relaxation spectroscopy

使用激光进行塑料粉末床熔炼（PBF-LB/P）的最大挑战之一是分析过程中的微观结构发展。根据最先进的和当前的研究，在PBF-LB/P中，材料行为的原位分析主要基于热成像或成像过程。这些方法不能对聚合物的结晶和老化机理等微观结构的发展做出任何结论。“使用介电松弛光谱原位分析塑料粉末床熔合过程中的微观结构发展和粉末老化”项目解决了这一挑战。该项目的目的是通过原位介电弛豫光谱（DRS）从根本上了解PBF-LB/P在加工过程中的熔化和结晶动力学。DRS已被证明是研究相变区域、结晶动力学、水分含量以及物理和化学老化机制的有力工具。这种分析方法基于聚合物样品的电正弦激励，并提供了弛豫和平移现象的详细信息。此外，DRS是一种鲁棒且快速的测量方法，已经证明其在聚合物加工中的原位监测潜力。DRS传感器的最新发展使聚合物样品的无接触分析成为可能。这使得DRS成为PBF-LB/P工艺中实现的完美工具，以便更深入地了解加工过程中的微观结构形成和粉末老化，甚至跨越几层。在项目范围内，工艺参数、与材料相关的工艺行为和最终组件特性之间的相关性将在现场DRS测量的基础上得到。除了熔融和结晶行为外，所谓的蛋糕粉的工艺固有特性，如老化效果或水分含量，将被探索，以建议进一步的粉末处理，如粉末的回收，在不进行任何额外测量的情况下进行。为了对这一过程产生一个普遍有效的理解，首先对已经了解的材料PA12进行调查，然后将调查结果转移到填充的PA12和TPU上。该项目代表了材料科学和增材制造的独特结合，并回答了PBF-LB/P微观结构发展的基本和未解决的问题。

One of the greatest challenges in the powder bed fusion of plastics using laser-beam (PBF-LB/P) is the analysis of the microstructure development within the process. According to the state-of-the-art and current research, the in-situ analysis of the material behavior is primarily based on thermographic or imaging processes in PBF-LB/P. These methods do not allow any conclusions on microstructure development such as crystallization and aging mechanism of the polymer during the process. This challenge is addressed by the project “In-situ analysis of microstructure development and powder aging during powder bed fusion of plastics using dielectric relaxation spectroscopy”. The objective of the project is to fundamentally understand the melting and crystallization dynamics in PBF-LB/P during processing by using in-situ dielectric relaxation spectroscopy (DRS). DRS has proven to be a powerful tool for investigating phase transition areas, crystallization kinetics, moisture content, and physical and chemical aging mechanisms. This analyzing method is based on an electrical sinusoidal excitation of a polymer sample and provides detailed information on relaxation and translation phenomena. In addition, DRS is a robust and fast measurement method that has already proven its potential for in-situ monitoring in polymer processing. The latest developments in DRS sensors enable the contact-free analysis of polymer samples. This qualifies DRS as a perfect tool for implementation in the PBF-LB/P process in order to gain a deeper understanding of the microstructure formation and powder aging during processing even across several layers. Within the scope of the project, a correlation between process parameters, material-dependent process behavior, and resulting component properties is to be derived on the basis of in-situ DRS measurements. In addition to the melting and crystallization behavior, process-inherent properties of the so-called partcake powder, such as aging effects or the moisture content, will be explored to recommend further powder treatment, such as recycling of the powder, following the process without any additional measurement. In order to generate a generally valid understanding of the process, the investigations are first carried out on the well-understood material PA12, and then the findings are transferred to filled PA12 and TPU. This project represents a unique combination of materials science and additive manufacturing and answers fundamental and unresolved questions of microstructure development in PBF-LB/P.