Optimization of material properties for highly-filled thermoplastic polymers used in fused filament fabrication of ceramics

Fused Filament Fabrication (FFF) is a material extrusion based additive manufacturing technique that enables the processing of thermoplastic filaments, which are selectively extruded and deposited in a layer-wise manner to create three-dimensional objects. Filaments of polymer-based compounds highly-filled with ceramic powders (ca. 40-60 vol.%), known as feedstocks, can be processed by means of FFF to shape ceramic parts. Such parts are then debound in order to remove the polymer from the feedstock. A highly porous structure is obtained, which is sintered at high temperatures to produce dense ceramic components. The use of highly-filled polymers constitutes a processing challenge, due to their high viscosity that complicates the fabrication by FFF. The material properties of compounds filled with zirconia (ca. 47 vol%) were optimized by the incorporation of an additional low viscosity component. It was observed that by adding the low viscosity component, the mechanical properties (flexibility, strength and stiffness) and feedstock viscosity are suitable for the production of filaments and the FFF process. Furthermore, the low viscosity component further promotes the defect-free removal of the major polymer fraction by leaching with a solvent.