Improved printability of diamond feedstock by designing of binder compositions for material extrusion additive manufacturing

Purpose Material extrusion additive manufacturing (MEX) is ideal for preparing structure-function integration diamond composites. Feedstock formulation is critical for MEX. However, current research primarily focuses on powder characteristics, such as diamond content and particle size, with limited exploration of binder compositions. This study aims to investigate the performance of diamond feedstocks with varying binder compositions and their suitability for MEX, providing insights and guidance for the design of diamond composite formulations used in MEX. Design/methodology/approach A composite binder system with high-density polyethylene and ethylene-vinyl acetate copolymer as the skeleton was used to prepare diamond feedstocks and corresponding printed green bodies. The rheological and thermal stability of feedstocks with varying skeleton contents (25, 30, 35 Wt.%) of binder were systematically investigated, and their printability and the properties of the corresponding green bodies were evaluated. Findings The results indicated that all prepared feedstocks exhibited pseudoplastic fluid characteristics and were suitable for MEX. Appropriately increasing skeleton content improves shear-thinning behavior. As the skeleton content increased, the surface roughness and dimensional deviation of printed bodies decreased and the stability of the printing process improved. However, excessive skeleton decreased the flow activation energy (E), affecting mixing uniformity, reducing filament deformation and weakening interlayer bonding. Originality/value An optimal skeleton content of the binder in feedstock was identified, which provided the most significant shear-thinning behavior, best thermal stability and mixing uniformity, resulting in the highest density and mechanical properties of the printed bodies.