Enhancing Photoelectric Powder Deposition of Polymers by Charge Control Substances

Abstract

Charge control substances (CCS) as additives for polymer powders are investigated to make polymer powders suitable for the electrophotographic powder deposition in powder-based additive manufacturing. The use of CCS unifies the occurring charge of a powder, which is crucial for this novel deposition method. Therefore, commercially available polymer powder is functionalized via dry coating in a shaker mixer with two different CCS and analyzed afterwards. The flowability and the degree of coverage of additives on the surface are used to evaluate the coating process. The thermal properties are analyzed by use of differential scanning calorimetry. Most important, the influence of the CCS on the powder charge is shown by measurements of the electrostatic surface potential at first and the powder deposition itself is performed and analyzed with selected formulations afterwards to show the potential of this method. Finally, tensile strength specimens are produced with the conventional deposition method in order to show the usability of the CCS for current machines.

Dry powder coating in additive manufacturing

“…The effect of flowing aids applied as antistatics was also reported by Lexow and Drummer (Lexow and Drummer, 2016), while Düsenberg at al. (Düsenberg et al, 2022a;Düsenberg et al, 2022b). demonstrated that the tribo charging behavior of PP can be tuned by dry coating with fumed oxides: coating with HDK H05TX (Wacker Chemie), which exhibits HMDS/PDMS surface-termination, allows to produce a negatively charging composite powder, while coating PP with HDK H05TA 3 (Wacker Chemie), which exhibits PDMS / amine (-NR 2 ) termination, yields positively charging feedstock.…”

“…Dry particle coating for surface functionalization is not limited to the application of flow enhancers. One can think of many more types of surface functionalization including coloring and, thus, tailoring of the absorption behavior (Jadhav et al, 2019;Jadhav et al, 2020;Jadhav et al, 2021;Lüddecke et al, 2021;Pannitz et al, 2021), charge control (Düsenberg et al, 2022a;Düsenberg et al, 2022b), improvement of electrical conductivity (Blümel et al, 2014), tuning the performance of batteries (Cho and Cho, 2010) or tailoring the dissolution behavior (Linsenbühler and Wirth, 2005), to only name a few examples. Within this paper, we will review recent advances in the application of dry powder coating processes for modification of AM powders with a focus on feedstock materials for powder bed fusion (PBF), i.e., PBF of polymers with a laser beam (PBF-LB/P) and PBF of metals with a laser or electron beam (PBF-LB/M, PBF-EB/M).…”

Innovative Process Strategies in Powder-Based Multi-Material Additive Manufacturing

“…First, the powder and a photoconductive plate (PCP, aluminum plate coated with photoconductive material) are homogeneously charged [28][29][30]. In EPA, powder particles can be charged via gas discharge or triboelectrically [31][32][33]. While gas discharge-based powder charging does not require any further functionalization of the particles in terms of their charging behavior, for triboelectric charging, the particles need to be functionalized with charge-control agents (CCAs) [33].…”

“…While gas discharge-based powder charging does not require any further functionalization of the particles in terms of their charging behavior, for triboelectric charging, the particles need to be functionalized with charge-control agents (CCAs) [33]. However, as described in [31][32][33], triboelectric charging offers some considerable advantages compared with gas discharge-based powder charging. In the case of triboelectric powder charging, the powder flowability, which, in many cases, renders the usage of certain powders impossible for PBF-LB/P, does not play any role in powder application.…”

Magnetizing Polymer Particles with a Solvent-Free Single Stage Process Using Superparamagnetic Iron Oxide Nanoparticles (SPION)s

“…Dry coating has been used for some time to improve the flowability [ 53 , 54 ] and fluidizability [ 55 ] of powders, e.g., by uniform deposition of silica nanoparticles on the surface of the particles. Research has also been conducted to use DC for the production of customized advanced materials, for example to control the powder charge [ 56 , 57 ], improve the humidity resistance [ 58 ] or to increase the electrical conductivity [ 59 ]. The influencing factors for dry coating can be found on the process side as well as on the material side.…”