Binder formulation and printing performance of zirconia filament feedstocks for material extrusion (MEX) additive manufacturing

• Interactive effect of 3 main binder components (backbone, elastomer, surfactant) on filament property. • Mathematical model and experimental validation on filament extrusion performance. • Ceramic filament buckling criterium for Material Extrusion Additive Manufacturing. • Distinguish the optimal binder formulation among a vast quantity of potential formulations. Material Extrusion (MEX) with filament feedstocks, as one of the earliest additive manufacturing technologies to produce polymeric parts, has evolved into a manufacturing approach capable of processing metal and ceramic materials by using composite feedstocks. This research presents a comprehensive study of the effect of each binder constituent (backbone, elastomer, and plasticiser) on the production and printability of zirconia filaments with both analytical and experimental methods. Multiple filaments with variable binder contents were designed, produced and tested. Rheological and mechanical tests on the filaments/as-printed pieces unveiled the role of each binder component. The measured data were integrated into mathematical models to evaluate the filament buckling criterion. Printing tests with different nozzle diameters validated the analytical evaluation and measured the buckling threshold. Based on the analytic and experimental results, an optimum region was distinguished for stable filament production and extrusion. Finally, one filament from the optimum region was selected to fabricate pieces for debinding and sintering test. The sintered parts demonstrated a relative density of 98 % and Vickers hardness of 12.48 GPa. This research provides a widely applicable method to identify the potential optimum binder formulation to compound a ceramic filament for MEX based on its intrinsic binder properties