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    Monitoring and classification of polymeric surface features for enabling the adoption of polypropylene powder bed fusion as a standard tool for bioprocessing equipment production

    Year: 2023

    Journal: Additive Manufacturing, Volume 72, 2023-06-25, page 103632

    Authors: Morales López, Álvaro; Marteleur, Klas; Finne-Wistrand, Anna

    Keywords: Surface wettability; Surface texture; Areal surface roughness; Polypropylene powder bed fusion; Tumble surface finishing

    Polypropylene (PP) powder bed fusion (PBF) with subsequent mechanical postprocessing can enable the development of more efficient and effective surfaces for bioprocessing equipment. However, there is still a lack of knowledge regarding the most relevant surface differences when compared to standardized surfaces. Herein, we present a new systematic methodology, including the evaluation of relevant roughness parameters and surface wettability, which has been implemented to assess the potential of AM to produce biopharmaceutical components. Surfaces of PP components produced by PBF and mechanically postprocessed by tumble surface finishing at 5, 10 and 15 h were compared to reference surfaces produced by computer numerical control (CNC) milling manufacturing. Thirteen roughness parameters were found to be relevant, of which the arithmetic mean peak curvature (Spc) and the density of peaks (Spd) were the most significant. The results demonstrate that the reference surfaces had Spc and Spd values of 1029 ± 36 mm−1 and 67739 ± 5440 mm−2, respectively, and moderate wettability with advancing (ACA) and receding (RCA) contact angles of 89 ± 3° and 68 ± 2°, respectively. The as-printed PBF surfaces were hydrophobic, with ACA of 119 ± 2° and RCA of 107 ± 4°, and with Spc and Spd values of 1089 ± 110 mm−1 and 30078 ± 4325 mm−2, respectively. PBF surfaces switched to a hydrophilic surface of 67 ± 3° and 44 ± 4° when the tumble surface finishing time was increased to 15 h. By taking advantage of this knowledge, we could produce surfaces using PBF and 5 h of mechanical postprocessing, which mimicked surface wetting and had Spc of 1100 ± 68 mm−1 and Spd of 55702 ± 9477 mm−2, similar to that of the CNC milling manufacturing. The developed comparative method and the results are important to better understand AM surfaces and can be used to transfer manufacturing from subtractive to additive technologies.
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