Tailored Syndiotactic Polypropylene Feedstock Material for Laser-Based Powder Bed Fusion of Polymers: Material Development and Processability

Current research on laser-based powder bed fusion of polymers (PBF-LB/P) is heavily focused on the relationship between the process and component properties of existing commercially available powder materials, thus constraining the scope of application. An innovative approach is presented in this study, which first emphasizes the synthesis of a tailored polypropylene for PBF-LB/P, and subsequently the performance of the synthesized polymer in the process. Syndiotactic polypropylene (sPP) was chosen because of its advantageous properties, such as low crystallinity and crystallization kinetics compared to isotactic polypropylene. Therefore, a well-known, highly active zirconocene dichloride catalyst was used with appropriate polymerization settings to yield moderately high-molecular-weight sPP with high syndiotacticity. As the obtained product already precipitated directly from the synthesis in particle form, no further intermediate process step to the feedstock material for PBF-LB/P was required. The obtained polymer was analyzed in terms of molecular weight, polydispersity, and syndiotacticity. Furthermore, key properties of the PBF-LB/P process, such as thermal properties, melt viscosity, and powder flow behavior, were investigated. The initial PBF-LB/P processability was assessed by building single layers in a parameter study using an EOS P 396 machine. Based on these findings, a multilayer component was manufactured demonstrating the processability of the material system.