Green mechanical properties of PVB-PEG-alumina feedstock for ceramic fused filament fabrication

• The water-debindable highly filled ceramic filaments based on alumina are flexible • The proportion of plasticizer and PEG affects the mechanical properties • Maximum bending radius provides much lower elongation at break than tensile test • Radial expansion results in filament blocking for materials with low Young’s modulus • Aging by polymer blend demixing affects the Young’s modulus and strain at break This paper investigates the critical aspects of the mechanical properties and aging of highly filled feedstocks and filaments for the ceramic fused filament fabrication (FFF) process by different evaluation methods. To evaluate the key mechanical properties, tensile tests on extruded feedstocks, maximum bending radius tests, and Shore D hardness are compared to the maximum extrusion forces considering Euler buckling theory and the radial expansion of the filaments under axial load. The aging is studied through the changes of the tensile properties of the feedstocks kept for 30 weeks in an uncontrolled atmosphere. The mechanical properties vary depending on the testing method and the aging of the feedstocks. The measured values can be used to define thresholds below which the printing process is not reliable. All the feedstocks evaluated, except the one with higher polyethylene glycol (PEG) content, are suitable from a mechanical point of view for the ceramic FFF process.