Dechet Maximilian A, Baumeister Ina, Schmidt Jochen
Institute of Particle Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 4, D-91058 Erlangen, Germany.
Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstraße 9a, D-91058 Erlangen, Germany.
Materials (Basel). 2020 Mar 27;13(7):1535. doi: 10.3390/ma13071535.
In this study, the development of a polyoxymethylene (POM) feedstock material for the powder bed fusion (PBF) of polymers is outlined. POM particles are obtained via liquid-liquid phase separation (LLPS) and precipitation, also known as the solution-dissolution process. In order to identify suitable POM solvent systems for LLPS and precipitation, in the first step, a solvent screening based on solubility parameters was performed, and acetophenone and triacetin were identified as the most promising suitable moderate solvents for POM. Cloud point curves were measured for both solvents to derive suitable temperature profiles and polymer concentrations for the solution-dissolution process. In the next step, important process parameters, namely POM concentration and stirring conditions, were studied to elucidate their effect on the product's properties. The product particles obtained from both aforementioned solvents were characterized with regard to their morphology and size distribution, as well as their thermal properties (cf. the PBF processing window) and compared to a cryo-milled POM PBF feedstock. Both solvents allowed for precipitation of POM particles of an appropriate size distribution for PBF for polymer concentrations of at least up to 20 wt.%. Finally, a larger powder batch for application in the PBF process was produced by precipitation from the preferred solvent acetophenone. This POM powder was further analyzed concerning its flowability, Hausner ratio, and mass-specific surface area. Finally, test specimens, namely a complex gyroid body and a detailed ornament, were successfully manufactured from this feedstock powder showing appropriate bulk solid and thermal properties to demonstrate PBF processability. In summary, a processable and suitable POM PBF feedstock could be developed based on the non-mechanical solution dissolution process, which, to the authors' best knowledge, has not been reported in previous studies.
在本研究中，概述了一种用于聚合物粉末床熔融（PBF）的聚甲醛（POM）原料材料的开发。聚甲醛颗粒通过液 - 液相分离（LLPS）和沉淀获得，也称为溶液 - 溶解过程。为了确定适用于LLPS和沉淀的聚甲醛溶剂体系，第一步，基于溶解度参数进行了溶剂筛选，苯乙酮和三醋精被确定为最有前景的适用于聚甲醛的适度溶剂。测量了两种溶剂的浊点曲线，以得出溶液 - 溶解过程的合适温度曲线和聚合物浓度。下一步，研究了重要的工艺参数，即聚甲醛浓度和搅拌条件，以阐明它们对产品性能的影响。对从上述两种溶剂获得的产品颗粒进行了形态、尺寸分布以及热性能（参见PBF加工窗口）的表征，并与冷冻研磨的聚甲醛PBF原料进行了比较。对于至少高达20 wt.%的聚合物浓度，两种溶剂都能使聚甲醛颗粒沉淀出适合PBF的尺寸分布。最后，通过从优选溶剂苯乙酮中沉淀制备了用于PBF工艺的更大批量的粉末。对该聚甲醛粉末的流动性、哈斯纳比和质量比表面积进行了进一步分析。最后，用这种原料粉末成功制造了测试样品，即一个复杂的螺旋体和一个精细的装饰品，展示了合适的整体固体和热性能，证明了PBF的可加工性。总之，基于非机械溶液溶解过程开发了一种可加工且合适的聚甲醛PBF原料，据作者所知，此前的研究中尚未有相关报道。
